Loss of mitochondrial fission depletes axonal mitochondria in midbrain dopamine neurons.

PubMed

Berthet, Amandine; Margolis, Elyssa B; Zhang, Jue; Hsieh, Ivy; Zhang, Jiasheng; Hnasko, Thomas S; Ahmad, Jawad; Edwards, Robert H; Sesaki, Hiromi; Huang, Eric J; Nakamura, Ken

2014-10-22

Disruptions in mitochondrial dynamics may contribute to the selective degeneration of dopamine (DA) neurons in Parkinson's disease (PD). However, little is known about the normal functions of mitochondrial dynamics in these neurons, especially in axons where degeneration begins, and this makes it difficult to understand the disease process. To study one aspect of mitochondrial dynamics-mitochondrial fission-in mouse DA neurons, we deleted the central fission protein dynamin-related protein 1 (Drp1). Drp1 loss rapidly eliminates the DA terminals in the caudate-putamen and causes cell bodies in the midbrain to degenerate and lose α-synuclein. Without Drp1, mitochondrial mass dramatically decreases, especially in axons, where the mitochondrial movement becomes uncoordinated. However, in the ventral tegmental area (VTA), a subset of midbrain DA neurons characterized by small hyperpolarization-activated cation currents (Ih) is spared, despite near complete loss of their axonal mitochondria. Drp1 is thus critical for targeting mitochondria to the nerve terminal, and a disruption in mitochondrial fission can contribute to the preferential death of nigrostriatal DA neurons. Copyright © 2014 the authors 0270-6474/14/3414304-14$15.00/0.

False labelling of dopaminergic terminals in the rabbit caudate nucleus: uptake and release of [3H]-5-hydroxytryptamine.

PubMed

Feuerstein, T J; Hertting, G; Lupp, A; Neufang, B

1986-07-01

The effect of the catecholamine uptake inhibitor nomifensine and of the 5-hydroxytryptamine (5-HT) uptake blocker 6-nitroquipazine on the accumulation of [3H]-5-HT (0.1 microM, 60 min incubation) and [3H]-dopamine (0.1 microM, 30 min incubation) into slices of hippocampus and caudate nucleus of the rabbit was investigated. In addition, the influence of nomifensine on the electrically evoked [3H]-5-HT release from caudate nucleus slices and of nomifensine and 6-nitroquipazine on [3H]-5-HT released from caudate nucleus slices was analysed. In hippocampal slices, which contain practically no dopaminergic but densely distributed 5-hydroxytryptaminergic and noradrenergic nerve terminals (ratio of dopamine:5-HT:noradrenaline about 1:30:25), nomifensine (1, 10 microM) did not affect the accumulation of [3H]-5-HT; 6-nitroquipazine (1 microM) reduced [3H]-5-HT uptake to about 35% of controls. In the caudate nucleus, however, where dopamine is the predominant monoamine (ratio of dopamine:5-HT:noradrenaline about 400:25:15) nomifensine (1, 10 microM) reduced the tritium accumulation to 65% whereas 6-nitroquipazine (1 microM) was ineffective. The combination of both drugs (1 microM each) led to a further decrease to about 15%. The uptake of [3H]-dopamine into hippocampal slices was blocked by both nomifensine (1 microM) and 6-nitroquipazine (1 microM) whereas in caudate nucleus slices only nomifensine (1, 10 microM) reduced the accumulation of [3H]-dopamine. The combination of both drugs was not more effective than nomifensine alone. The different effects of both uptake inhibitors in the hippocampus and caudate nucleus suggest a neurone specific rather than a substrate specific mode of action. 4 In caudate nucleus slices incubated with [3H]-5-HT and superfused continuously the electrically evoked 5-HT release was diminished by the D2-dopamine receptor agonist LY 171555 and enhanced by the D2-receptor antagonist domperidone. If, however, the labelling of caudate nucleus slices was performed in the presence of I microM or 1O microM nomifensine, the modulation of 5-HT release via D2- receptors was reduced or abolished, respectively. In the hippocampus both LY 171555 and domperidone were completely ineffective in modulating 5-HT release regardless of the absence or presence of nomifensine. 5 The present results indicate that an inverse cross labelling of [3H]-5-HT into dopaminergic and of [3H]-dopamine into 5-hydroxytryptaminergic terminals may occur despite the low concentration (0.1 microM) oftritiated transmitters used. Such cross labelling, as demonstrated with the incubation period of 60 min in the caudate nucleus, may falsely indicate the existence of D2-dopamine receptors modulating [3H]-5-HT release. If both 5-hydroxytryptaminergic and dopaminergic terminals are present within the brain region under investigation false labelling can be corrected using neuronally specific uptake inhibitors.

Cyclooxygenase-2 is an obligatory factor in methamphetamine-induced neurotoxicity.

PubMed

Thomas, David M; Kuhn, Donald M

2005-05-01

Methamphetamine causes persistent damage to dopamine nerve endings of the striatum. The mechanisms underlying its neurotoxicity are not fully understood, but considerable evidence points to oxidative stress as a probable mechanism. A recent microarray analysis of gene expression changes caused by methamphetamine revealed that cyclooxygenase-2 (COX-2) was induced along with its transcription factor CCAAT/enhancer-binding protein (Thomas DM, Francescutti-Verbeem DM, Liu X, and Kuhn DM, 2004). We report presently that methamphetamine increases striatal expression of COX-2 protein. Cyclooxygenase-1 (COX-1) expression was not changed. Mice bearing a null mutation of the gene for COX-2 were resistant to methamphetamine-induced neurotoxicity. COX-1 knockouts, like wild-type mice, showed extensive dopamine nerve terminal damage. Selective inhibitors of COX-1 [5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethyl pyrazole (SC-560)], COX-2 [N-[2-(cyclohexyloxy)-4-nitrophenyl] methanesulfonamide (NS-398), rofecoxib], or COX-3 (antipyrine) or a nonselective inhibitor of the COX-1/2 isoforms (ketoprofen) did not protect mice from neurotoxicity. Finally, methamphetamine did not change striatal prostaglandin E(2) content. Taken together, these data suggest that COX-2 is an obligatory factor in methamphetamine-induced neurotoxicity. The functional aspect of COX-2 that contributes to drug-induced neurotoxicity does not appear to be its prostaglandin synthetic capacity. Instead, the peroxidase activity associated with COX-2, which can lead to the formation of reactive oxygen species and dopamine quinones, can account for its role.

Early attempts to visualize cortical monoamine nerve terminals.

PubMed

Hökfelt, Tomas

2016-08-15

The Falck-Hillarp, formaldehyde fluorescence method for the demonstration of monoamine neurons in a microscope was established in Lund, Sweden and published in 1962. In the same year Hillarp moved to Karolinska Institutet in Stockholm. Two years later Dahlström and Fuxe published the famous supplement in Acta Physiologica Scandinavica, describing the distribution of the dopamine, noradrenaline and serotonin cell groups in the rat brain. This landmark paper also represented an important contribution to an emerging discipline in neuroscience - chemical neuroanatomy. During the following years several modifications of the original method were developed, attempting to solve some shortcomings, one being the reproducible demonstration of noradrenaline nerve terminals in cortical regions. One result was the paper focused on in the present article, which also describes other efforts in the same direction going on in parallel, primarily, in Lund and Stockholm. As a result there was, in the mid 1970s, a fairly complete knowledge of the catecholamine systems in the rat brain. This article is part of a Special Issue entitled SI:50th Anniversary Issue. Copyright © 2016 Elsevier B.V. All rights reserved.

Role of external and internal calcium on heterocarrier-mediated transmitter release.

PubMed

Fassio, A; Bonanno, G; Fontana, G; Usai, C; Marchi, M; Raiteri, M

1996-04-01

Release-regulating heterocarriers exist on brain nerve endings. We have investigated in this study the mechanisms involved in the neurotransmitter release evoked by GABA heterocarrier activation. GABA increased the basal release of [3H]acetylcholine and [3H]noradrenaline from rat hippocampal synaptosomes and of [3H]dopamine from striatal synaptosomes. These GABA effects, insensitive to GABA receptor antagonists, were prevented by inhibiting GABA uptake but not by blocking noradrenaline, choline, or dopamine transport. Lack of extracellular Ca2+ or addition of tetrodotoxin selectively abolished the GABA-evoked release of [3H]noradrenaline, leaving unaffected that of [3H]acetylcholine or [3H]dopamine. 1,2-Bis(2-aminophenoxyl)-ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM) or vesamicol attenuated the release of [3H]acetylcholine elicited by GABA. Reserpine, but not BAPTA-AM, prevented the effect of GABA on [3H] dopamine release. Autoreceptor activation inhibited the GABA-evoked release of [3H]noradrenaline but not that of [3H]acetylcholine or [3H]dopamine. It is concluded that (a) the release of [3H]noradrenaline consequent to activation of GABA heterocarriers sited on noradrenergic terminals meets the criteria of a conventional exocytotic process, (b) the extracellular [Ca2+]-independent releases of [3H]acetylcholine and [3H]dopamine appear to occur from vesicles possibly through involvement of intraterminal Ca2+, and (c) autoreceptor activation only affects heterocarrier-mediated vesicular release linked to entry of extracellular Ca2+.

Acute effects of moclobemide and deprenyl on 5-HT synthesis rates in the rat brain: An autoradiographic study.

PubMed

Nishi, Kyoko; Mück-Seler, Dorotea; Hasegawa, Shu; Watanabe, Arata; Diksic, Mirko

2006-10-16

Serotonin (5-HT), norepinephrine (NE) and dopamine (DA) released from nerve terminals in the brain are primarily removed from the synaptic cleft by a reuptake mechanism. In part, the homeostasis is maintained by monoamine oxidase (MAO) deamination achieved primarily intracellularly. The present study's aim was to examine the effect of the acute administration of the MAO inhibitors, moclobemide (a MAO-A inhibitor) and deprenyl (a MAO-B inhibitor), on 5-HT synthesis rates, measured in discrete regions of the rat brain by an autoradiographic method, using alpha-[14C]methyl-l-tryptophan as a tracer. MAO inhibitors have different effects on 5-HT synthesis rates in the cell bodies and areas of the nerve terminals. Moclobemide (10 mg/kg, i.p. 30 min before the tracer injection) and deprenyl (3 mg/kg, i.p. 2 h before the tracer injection) decreased the 5-HT synthesis rates in the dorsal (-18% and -22%) and median (-22% and -33%) raphe, respectively. Moclobemide also significantly decreased 5-HT synthesis in the entire nerve terminal areas investigated. The reductions were between 23% (cingulate cortex) and 50% (locus coeruleus). Deprenyl did not significantly affect 5-HT synthesis in the nerve terminals. The present results suggest that MAO-A, and to a lesser extent, MAO-B, are involved in the regulation of 5-HT synthesis in the rat brain. The mechanism(s) of MAO inhibitors' action on 5-HT synthesis in the raphe nuclei are probably related to an increase in the extraneuronal 5-HT concentration and also to the interaction between the serotonergic and catecholaminergic neurons. The reduction of 5-HT synthesis in the raphe nuclei likely occurs by an action of extracellular 5-HT via the dendritic autoreceptors with a possible contribution from the action of extracellular DA and NE. In the terminal regions, the most likely mechanism is via the presynaptic autoreceptors through which elevated extraneuronal 5-HT acts on synthesis control. However, there is also a possibility that the elevation in intraneuronal 5-HT directly inhibits its synthesis, especially following deprenyl treatment. A great influence of moclobemide on 5-HT synthesis could be related to its antidepressant action.

Three-Dimensional-Bioprinted Dopamine-Based Matrix for Promoting Neural Regeneration.

PubMed

Zhou, Xuan; Cui, Haitao; Nowicki, Margaret; Miao, Shida; Lee, Se-Jun; Masood, Fahed; Harris, Brent T; Zhang, Lijie Grace

2018-03-14

Central nerve repair and regeneration remain challenging problems worldwide, largely because of the extremely weak inherent regenerative capacity and accompanying fibrosis of native nerves. Inadequate solutions to the unmet needs for clinical therapeutics encourage the development of novel strategies to promote nerve regeneration. Recently, 3D bioprinting techniques, as one of a set of valuable tissue engineering technologies, have shown great promise toward fabricating complex and customizable artificial tissue scaffolds. Gelatin methacrylate (GelMA) possesses excellent biocompatible and biodegradable properties because it contains many arginine-glycine-aspartic acids (RGD) and matrix metalloproteinase sequences. Dopamine (DA), as an essential neurotransmitter, has proven effective in regulating neuronal development and enhancing neurite outgrowth. In this study, GelMA-DA neural scaffolds with hierarchical structures were 3D-fabricated using our custom-designed stereolithography-based printer. DA was functionalized on GelMA to synthesize a biocompatible printable ink (GelMA-DA) for improving neural differentiation. Additionally, neural stem cells (NSCs) were employed as the primary cell source for these scaffolds because of their ability to terminally differentiate into a variety of cell types including neurons, astrocytes, and oligodendrocytes. The resultant GelMA-DA scaffolds exhibited a highly porous and interconnected 3D environment, which is favorable for supporting NSC growth. Confocal microscopy analysis of neural differentiation demonstrated that a distinct neural network was formed on the GelMA-DA scaffolds. In particular, the most significant improvements were the enhanced neuron gene expression of TUJ1 and MAP2. Overall, our results demonstrated that 3D-printed customizable GelMA-DA scaffolds have a positive role in promoting neural differentiation, which is promising for advancing nerve repair and regeneration in the future.

Peripheral Administration of Tetanus Toxin Hc Fragment Prevents MPP+ Toxicity In Vivo.

PubMed

Moreno-Galarza, Natalia; Mendieta, Liliana; Palafox-Sánchez, Victoria; Herrando-Grabulosa, Mireia; Gil, Carles; Limón, Daniel I; Aguilera, José

2018-02-19

Several studies have shown that intrastriatal application of 1-methyl-4-phenylpyridinium (MPP + ) produces similar biochemical changes in rat to those seen in Parkinson's disease (PD), such as dopaminergic terminal degeneration and consequent appearance of motor deficits, making the MPP + lesion a widely used model of parkinsonism in rodents. Previous results from our group have shown a neuroprotective effect of the carboxyl-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) under different types of stress. In the present study, pretreatment with the intraperitoneal injection of Hc-TeTx in rats prevents the decrease of tyrosine hydroxylase immunoreactivity in the striatum due to injury with MPP + , when applied stereotaxically in the striatum. Similarly, striatal catecholamine contents are restored, as well as the levels of two other dopaminergic markers, the dopamine transporter (DAT) and the vesicular monoamine transporter-2 (VMAT-2). Additionally, uptake studies of [ 3 H]-dopamine and [ 3 H]-MPP + reveal that DAT action is not affected by Hc-TeTx, discarding a protective effect due to a reduced entry of MPP + into nerve terminals. Behavioral assessments show that Hc-TeTx pretreatment improves the motor skills (amphetamine-induced rotation, forelimb use, and adjusting steps) of MPP + -treated rats. Our results lead us to consider Hc-TeTx as a potential therapeutic tool in pathologies caused by impairment of dopaminergic innervation in the striatum, as is the case of PD.

Running wheel exercise enhances recovery from nigrostriatal dopamine injury without inducing neuroprotection.

PubMed

O'Dell, S J; Gross, N B; Fricks, A N; Casiano, B D; Nguyen, T B; Marshall, J F

2007-02-09

Forced use of the forelimb contralateral to a unilateral injection of the dopaminergic neurotoxin 6-hydroxydopamine can promote recovery of motor function in that limb and can significantly decrease damage to dopamine terminals. The present study was conducted to determine (1) whether a form of voluntary exercise, wheel running, would improve motor performance in rats with such lesions, and (2) whether any beneficial effects of wheel running are attributable to ameliorating the dopaminergic damage. In experiment 1, rats were allowed to run in exercise wheels or kept in home cages for 2 1/2 weeks, then given stereotaxic infusions of 6-hydroxydopamine into the left striatum. The rats were replaced into their original environments (wheels or home cages) for four additional weeks, and asymmetries in forelimb use were quantified at 3, 10, 17, and 24 days postoperatively. After killing, dopaminergic damage was assessed by both quantifying 3 beta-(4-iodophenyl)tropan-2 beta-carboxylic acid methyl ester ([(125)I]RTI-55) binding to striatal dopamine transporters and counting tyrosine hydroxylase-positive cells in the substantia nigra. Exercised 6-hydroxydopamine-infused rats showed improved motor outcomes relative to sedentary lesioned controls, effects that were most apparent at postoperative days 17 and 24. Despite this behavioral improvement, 6-hydroxydopamine-induced loss of striatal dopamine transporters and tyrosine hydroxylase-positive nigral cells in exercised and sedentary groups did not differ. Since prior studies suggested that forced limb use improves motor performance by sparing nigrostriatal dopaminergic neurons from 6-hydroxydopamine damage, experiment 2 used a combined regimen of forced plus voluntary wheel running. Again, we found that the motor performance of exercised rats improved more rapidly than that of sedentary controls, but that there were no differences between these groups in the damage produced by 6-hydroxydopamine. It appears that voluntary exercise can facilitate recovery from partial nigrostriatal injury, but it does so without evident sparing of dopamine nerve terminals.

METHAMPHETAMINE-INDUCED DOPAMINE TERMINAL DEFICITS IN THE NUCLEUS ACCUMBENS ARE EXACERBATED BY REWARD-ASSOCIATED CUES AND ATTENUATED BY CB1 RECEPTOR ANTAGONISM

PubMed Central

Loewinger, Gabriel C.; Beckert, Michael V.; Tejeda, Hugo A.; Cheer, Joseph F.

2012-01-01

Methamphetamine (METH) exposure is primarily associated with deleterious effects to dopaminergic neurons. While several studies have implicated the endocannabinoid system in METH’s locomotor, rewarding and neurochemical effects, a role for this signaling system in METH’s effects on dopamine terminal dynamics has not been elucidated. Given that CB1 receptor blockade reduces the acute potentiation of phasic extracellular dopamine release from other psychomotor stimulant drugs and that the degree of acute METH-induced increases in extracellular dopamine levels is related to the severity of dopamine depletion, we predicted that pretreatment with the CB1 receptor antagonist rimonabant would reduce METH-induced alterations at dopamine terminals. Furthermore, we hypothesized that administration of METH in environments where reward associated-cues were present would potentiate METH’s acute effects on dopamine release in the nucleus accumbens and exacerbate changes in dopamine terminal activity. Fast-scan cyclic voltammetry was used to measure electrically-evoked dopamine release in the nucleus accumbens and revealed markers of compromised dopamine terminal integrity nine days after a single dose of METH. These were exacerbated in animals that received METH in the presence of reward-associated cues, and attenuated in rimonabant-pretreated animals. While these deficits in dopamine dynamics were associated with reduced operant responding on days following METH administration in animals treated with only METH, rimonabant-pretreated animals exhibited levels of operant responding comparable to control. Moreover, dopamine release correlated significantly with changes in lever pressing behavior that occurred on days following METH administration. Together these data suggest that the endocannabinoid system is involved in the subsecond dopaminergic response to METH. PMID:22306525

Reinforcement in an in Vitro Analog of Appetitive Classical Conditioning of Feeding Behavior in "Aplysia": Blockade by a Dopamine Antagonist

ERIC Educational Resources Information Center

Reyes, Fredy D.; Mozzachiodi, Riccardo; Baxter, Douglas A.; Byrne, John H.

2005-01-01

In a recently developed in vitro analog of appetitive classical conditioning of feeding in "Aplysia," the unconditioned stimulus (US) was electrical stimulation of the esophageal nerve (En). This nerve is rich in dopamine (DA)-containing processes, which suggests that DA mediates reinforcement during appetitive conditioning. To test this…

Salvinorin A regulates dopamine transporter function via a kappa opioid receptor and ERK1/2-dependent mechanism.

PubMed

Kivell, Bronwyn; Uzelac, Zeljko; Sundaramurthy, Santhanalakshmi; Rajamanickam, Jeyaganesh; Ewald, Amy; Chefer, Vladimir; Jaligam, Vanaja; Bolan, Elizabeth; Simonson, Bridget; Annamalai, Balasubramaniam; Mannangatti, Padmanabhan; Prisinzano, Thomas E; Gomes, Ivone; Devi, Lakshmi A; Jayanthi, Lankupalle D; Sitte, Harald H; Ramamoorthy, Sammanda; Shippenberg, Toni S

2014-11-01

Salvinorin A (SalA), a selective κ-opioid receptor (KOR) agonist, produces dysphoria and pro-depressant like effects. These actions have been attributed to inhibition of striatal dopamine release. The dopamine transporter (DAT) regulates dopamine transmission via uptake of released neurotransmitter. KORs are apposed to DAT in dopamine nerve terminals suggesting an additional target by which SalA modulates dopamine transmission. SalA produced a concentration-dependent, nor-binaltorphimine (BNI)- and pertussis toxin-sensitive increase of ASP(+) accumulation in EM4 cells coexpressing myc-KOR and YFP-DAT, using live cell imaging and the fluorescent monoamine transporter substrate, trans 4-(4-(dimethylamino)-styryl)-N-methylpyridinium) (ASP(+)). Other KOR agonists also increased DAT activity that was abolished by BNI pretreatment. While SalA increased DAT activity, SalA treatment decreased serotonin transporter (SERT) activity and had no effect on norepinephrine transporter (NET) activity. In striatum, SalA increased the Vmax for DAT mediated DA transport and DAT surface expression. SalA up-regulation of DAT function is mediated by KOR activation and the KOR-linked extracellular signal regulated kinase-½ (ERK1/2) pathway. Co-immunoprecipitation and BRET studies revealed that DAT and KOR exist in a complex. In live cells, DAT and KOR exhibited robust FRET signals under basal conditions. SalA exposure caused a rapid and significant increase of the FRET signal. This suggests that the formation of KOR and DAT complexes is promoted in response to KOR activation. Together, these data suggest that enhanced DA transport and decreased DA release resulting in decreased dopamine signalling may contribute to the dysphoric and pro-depressant like effects of SalA and other KOR agonists. Copyright © 2014 Elsevier Ltd. All rights reserved.

Serotonin and dopamine transporter binding in children with autism determined by SPECT.

PubMed

Makkonen, Ismo; Riikonen, Raili; Kokki, Hannu; Airaksinen, Mauno M; Kuikka, Jyrki T

2008-08-01

Disturbances in the serotonergic system have been recognized in autism. To investigate the association between serotonin and dopamine transporters and autism, we studied 15 children (14 males, one female; mean age 8 y 8 mo [SD 3 y 10 mo]) with autism and 10 non-autistic comparison children (five males, five females; mean age 9 y 10 mo [SD 2 y 8 mo]) using single-photon emission computed tomography (SPECT) with [123 I] nor-beta-CIT. The children, with autism were studied during light sedation. They showed reduced serotonin transporter (SERT) binding capacity in the medial frontal cortex, midbrain, and temporal lobe areas. However, after correction due to the estimated effect of sedation, the difference remained significant only in the medial frontal cortex area (p=0.002). In the individuals with autism dopamine transporter (DAT) binding did not differ from that of the comparison group. The results indicate that SERT binding capacity is disturbed in autism. The reduction is more evident in adolescence than in earlier childhood. The low SERT binding reported here and the low serotonin synthesis capacity shown elsewhere may indicate maturation of a lesser number of serotonergic nerve terminals in individuals with autism.

Methamphetamine neurotoxicity in dopamine nerve endings of the striatum is associated with microglial activation.

PubMed

Thomas, David M; Walker, Paul D; Benjamins, Joyce A; Geddes, Timothy J; Kuhn, Donald M

2004-10-01

Methamphetamine intoxication causes long-lasting damage to dopamine nerve endings in the striatum. The mechanisms underlying this neurotoxicity are not known but oxidative stress has been implicated. Microglia are the major antigen-presenting cells in brain and when activated, they secrete an array of factors that cause neuronal damage. Surprisingly, very little work has been directed at the study of microglial activation as part of the methamphetamine neurotoxic cascade. We report here that methamphetamine activates microglia in a dose-related manner and along a time course that is coincident with dopamine nerve ending damage. Prevention of methamphetamine toxicity by maintaining treated mice at low ambient temperature prevents drug-induced microglial activation. MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), which damages dopamine nerve endings and cell bodies, causes extensive microglial activation in striatum as well as in the substantia nigra. In contrast, methamphetamine causes neither microglial activation in the substantia nigra nor dopamine cell body damage. Dopamine transporter antagonists (cocaine, WIN 35,428 [(-)-2-beta-carbomethoxy-3-beta-(4-fluorophenyl)tropane 1,5-naphthalenedisulfonate], and nomifensine), selective D1 (SKF 82958 [(+/-)-6-chloro-7,8-dihydroxy-3-allyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide]), D2 (quinpirole), or mixed D1/D2 receptor agonists (apomorphine) do not mimic the effect of methamphetamine on microglia. Hyperthermia, a prominent and dangerous clinical response to methamphetamine intoxication, was also ruled out as the cause of microglial activation. Together, these data suggest that microglial activation represents an early step in methamphetamine-induced neurotoxicity. Other neurochemical effects resulting from methamphetamine-induced overflow of DA into the synapse, but which are not neurotoxic, do not play a role in this response.

Trifurcation of the tibial nerve within the tarsal tunnel.

PubMed

Develi, Sedat

2018-05-01

The tibial nerve is the larger terminal branch of the sciatic nerve and it terminates in the tarsal tunnel by giving lateral and medial plantar nerves. We present a rare case of trifurcation of the tibial nerve within the tarsal tunnel. The variant nerve curves laterally after branching from the tibial nerve and courses deep to quadratus plantae muscle. Interestingly, posterior tibial artery was also terminating by giving three branches. These branches were accompanying the terminal branches of the tibial nerve.

Nicotine-mediated improvement in L-dopa-induced dyskinesias in MPTP-lesioned monkeys is dependent on dopamine nerve terminal function.

PubMed

Quik, Maryka; Mallela, Archana; Chin, Matthew; McIntosh, J Michael; Perez, Xiomara A; Bordia, Tanuja

2013-02-01

L-dopa-induced dyskinesias (LIDs) are abnormal involuntary movements that develop with long term L-dopa therapy for Parkinson's disease. Studies show that nicotine administration reduced LIDs in several parkinsonian animal models. The present work was done to understand the factors that regulate the nicotine-mediated reduction in LIDs in MPTP-lesioned nonhuman primates. To approach this, we used two groups of monkeys, one with mild-moderate and the other with more severe parkinsonism rendered dyskinetic using L-dopa. In mild-moderately parkinsonian monkeys, nicotine pretreatment (300 μg/ml via drinking water) prevented the development of LIDs by ~75%. This improvement was maintained when the nicotine dose was lowered to 50 μg/ml but was lost with nicotine removal. Nicotine re-exposure again decreased LIDs. By contrast, nicotine treatment did not reduce LIDs in monkeys with more severe parkinsonism. We next determined how nicotine's ability to reduce LIDs correlated with lesion-induced changes in the striatal dopamine transporter and (3)H-dopamine release in these two groups of monkeys. The striatal dopamine transporter was reduced to 54% and 28% of control in mild-moderately and more severely parkinsonian monkeys, respectively. However, basal, K(+), α4β2* and α6β2* nAChR-evoked (3)H-dopamine release were near control levels in striatum of mild-moderately parkinsonian monkeys. By contrast, these same release measures were reduced to a significantly greater extent in striatum of more severely parkinsonian monkeys. Thus, nicotine best improves LIDs in lesioned monkeys in which striatal dopamine transmission is still relatively intact. These data suggest that nicotine treatment would most effectively reduce LIDs in patients with mild to moderate Parkinson's disease. Copyright © 2012 Elsevier Inc. All rights reserved.

Mephedrone, an Abused Psychoactive Component of “Bath Salts” and Methamphetamine Congener, Does not Cause Neurotoxicity to Dopamine Nerve Endings of the Striatum

PubMed Central

Angoa-Pérez, Mariana; Kane, Michael J.; Francescutti, Dina M.; Sykes, Katherine E.; Shah, Mrudang M.; Mohammed, Abiy M.; Thomas, David M.; Kuhn, Donald M.

2012-01-01

Mephedrone (4-methylmethcathinone) is a β-ketoamphetamine with close structural analogy to substituted amphetamines and cathinone derivatives. Abuse of mephedrone has increased dramatically in recent years and has become a significant public health problem in the US and Europe. Unfortunately, very little information is available on the pharmacological and neurochemical actions of mephedrone. In light of the proven abuse potential of mephedrone and considering its similarity to methamphetamine and methcathinone, it is particularly important to know if mephedrone shares with these agents an ability to cause damage to dopamine nerve endings of the striatum. Accordingly, we treated mice with a binge-like regimen of mephedrone (4X 20 or 40 mg/kg) and examined the striatum for evidence of neurotoxicity 2 or 7 days after treatment. While mephedrone caused hyperthermia and locomotor stimulation, it did not lower striatal levels of dopamine, tyrosine hydroxylase or the dopamine transporter under any of the treatment conditions used presently. Furthermore, mephedrone did not cause microglial activation in striatum nor did it increase glial fibrillary acidic protein levels. Taken together, these surprising results suggest that mephedrone, despite its numerous mechanistic overlaps with methamphetamine and the cathinone derivatives, does not cause neurotoxicity to dopamine nerve endings of the striatum. PMID:22191803

[18F]CFT [(18F)WIN 35,428], a radioligand to study the dopamine transporter with PET: characterization in human subjects.

PubMed

Laakso, A; Bergman, J; Haaparanta, M; Vilkman, H; Solin, O; Hietala, J

1998-03-01

We have characterized the usage of [18F]CFT (also known as [18F]WIN 35,428) as a radioligand for in vivo studies of human dopamine transporter by PET. CFT was labeled with 18F to a high specific activity, and dynamic PET scans were conducted in healthy volunteers at various time points up to 5 h from [18F]CFT injection. The regional distribution of [18F]CFT uptake correlated well with the known distribution of dopaminergic nerve terminals in the human brain and also with that of other dopamine transporter radioligands. Striatal binding peaked at 225 min after injection and declined thereafter, demonstrating the reversible nature of the binding to the dopamine transporter. Therefore, due to the relatively long half-life of 18F (109.8 min), PET scans with [18F]CFT could easily be conducted during the binding equilibrium, allowing estimation of Bmax/Kd values (i.e., binding potential). Binding potentials for putamen and caudate measured at equilibrium were 4.79+/-0.11 and 4.50+/-0.23, respectively. We were able to also visualize midbrain dopaminergic neurons (substantia nigra) with [18F]CFT in some subjects. In conclusion, the labeling of CFT with 18F allows PET scans to be conducted at binding equilibrium, and therefore a high signal-to-noise ratio and reliable quantification of binding potential can be achieved. With a high resolution 3D PET scanner, the quantification of extrastriatal dopamine transporters should become possible.

Studies on the role of dopamine in the degeneration of 5-HT nerve endings in the brain of Dark Agouti rats following 3,4-methylenedioxymethamphetamine (MDMA or ‘ecstasy') administration

PubMed Central

Colado, M I; O'Shea, E; Granados, R; Esteban, B; Martín, A B; Green, A R

1999-01-01

We investigated whether dopamine plays a role in the neurodegeneration of 5-hydroxytryptamine (5-HT) nerve endings occurring in Dark Agouti rat brain after 3,4-methylenedioxymethamphetamine (MDMA or ‘ecstasy') administration. Haloperidol (2 mg kg−1 i.p.) injected 5 min prior and 55 min post MDMA (15 mg kg−1 i.p.) abolished the acute MDMA-induced hyperthermia and attenuated the neurotoxic loss of 5-HT 7 days later. When the rectal temperature of MDMA+haloperidol treated rats was kept elevated, this protective effect was marginal. MDMA (15 mg kg−1) increased the dopamine concentration in the dialysate from a striatal microdialysis probe by 800%. L-DOPA (25 mg kg−1 i.p., plus benserazide, 6.25 mg kg−1 i.p.) injected 2 h after MDMA (15 mg kg−1) enhanced the increase in dopamine in the dialysate, but subsequent neurodegeneration was unaltered. L-DOPA (25 mg kg−1) injected before a sub-toxic dose of MDMA (5 mg kg−1) failed to induce neurodegeneration. The MDMA-induced increase in free radical formation in the hippocampus (indicated by increased 2,3- and 2,5-dihydroxybenzoic acid in a microdialysis probe perfused with salicylic acid) was unaltered by L-DOPA. The neuroprotective drug clomethiazole (50 mg kg−1 i.p.) did not influence the MDMA-induced increase in extracellular dopamine. These data suggest that previous observations on the protective effect of haloperidol and potentiating effect of L-DOPA on MDMA-induced neurodegeneration may have resulted from effects on MDMA-induced hyperthermia. The increased extracellular dopamine concentration following MDMA may result from effects of MDMA on dopamine re-uptake, monoamine oxidase and 5-HT release rather than an ‘amphetamine-like' action on dopamine release, thus explaining why the drug does not induce degeneration of dopamine nerve endings. PMID:10193771

Biomimetic PDMS-hydroxyurethane terminated with catecholic moieties for chemical grafting on transition metal oxide-based surfaces

NASA Astrophysics Data System (ADS)

de Aguiar, Kelen R.; Rischka, Klaus; Gätjen, Linda; Noeske, Paul-Ludwig Michael; Cavalcanti, Welchy Leite; Rodrigues-Filho, Ubirajara P.

2018-01-01

The aim of this work was to synthesize a non-isocyanate poly(dimethylsiloxane) hydroxyurethane with biomimetic terminal catechol moieties, as a candidate for inorganic and metallic surface modification. Such surface modifier is capable to strongly attach onto metallic and inorganic substrates forming layers and, in addition, providing water-repellent surfaces. The non-isocyanate route is based on carbon dioxide cycloaddition into bis-epoxide, resulting in a precursor bis(cyclic carbonate)-polydimethylsiloxane (CCPDMS), thus fully replacing isocyanate in the manufacture process. A biomimetic approach was chosen with the molecular composition being inspired by terminal peptides present in adhesive proteins of mussels, like Mefp (Mytilus edulis foot protein), which bear catechol moieties and are strong adhesives even under natural and saline water. The catechol terminal groups were grafted by aminolysis reaction into a polydimethylsiloxane backbone. The product, PDMSUr-Dopamine, presented high affinity towards inhomogeneous alloy surfaces terminated by native oxide layers as demonstrated by quartz crystal microbalance (QCM-D), as well as stability against desorption by rinsing with ethanol. As revealed by QCM-D, X-ray photoelectron spectroscopy (XPS) and computational studies, the thickness and composition of the resulting nanolayers indicated an attachment of PDMSUr-Dopamine molecules to the substrate through both terminal catechol groups, with the adsorbate exposing the hydrophobic PDMS backbone. This hypothesis was investigated by classical molecular dynamic simulation (MD) of pure PDMSUr-Dopamine molecules on SiO2 surfaces. The computationally obtained PDMSUr-Dopamine assembly is in agreement with the conclusions from the experiments regarding the conformation of PDMSUr-Dopamine towards the surface. The tendency of the terminal catechol groups to approach the surface is in agreement with proposed model for the attachment PDMSUr-Dopamine. Remarkably, the versatile PDMSUr-Dopamine modifier facilitates such functionalization for various substrates such as titanium alloy, steel and ceramic surfaces.

Mephedrone, an abused psychoactive component of 'bath salts' and methamphetamine congener, does not cause neurotoxicity to dopamine nerve endings of the striatum.

PubMed

Angoa-Pérez, Mariana; Kane, Michael J; Francescutti, Dina M; Sykes, Katherine E; Shah, Mrudang M; Mohammed, Abiy M; Thomas, David M; Kuhn, Donald M

2012-03-01

Mephedrone (4-methylmethcathinone) is a β-ketoamphetamine with close structural analogy to substituted amphetamines and cathinone derivatives. Abuse of mephedrone has increased dramatically in recent years and has become a significant public health problem in the United States and Europe. Unfortunately, very little information is available on the pharmacological and neurochemical actions of mephedrone. In light of the proven abuse potential of mephedrone and considering its similarity to methamphetamine and methcathinone, it is particularly important to know if mephedrone shares with these agents an ability to cause damage to dopamine nerve endings of the striatum. Accordingly, we treated mice with a binge-like regimen of mephedrone (4 × 20 or 40 mg/kg) and examined the striatum for evidence of neurotoxicity 2 or 7 days after treatment. While mephedrone caused hyperthermia and locomotor stimulation, it did not lower striatal levels of dopamine, tyrosine hydroxylase or the dopamine transporter under any of the treatment conditions used presently. Furthermore, mephedrone did not cause microglial activation in striatum nor did it increase glial fibrillary acidic protein levels. Taken together, these surprising results suggest that mephedrone, despite its numerous mechanistic overlaps with methamphetamine and the cathinone derivatives, does not cause neurotoxicity to dopamine nerve endings of the striatum. © 2011 The Authors. Journal of Neurochemistry © 2011 International Society for Neurochemistry.

Serotonergic mechanisms responsible for levodopa-induced dyskinesias in Parkinson’s disease patients

PubMed Central

Politis, Marios; Wu, Kit; Loane, Clare; Brooks, David J.; Kiferle, Lorenzo; Turkheimer, Federico E.; Bain, Peter; Molloy, Sophie; Piccini, Paola

2014-01-01

Levodopa-induced dyskinesias (LIDs) are the most common and disabling adverse motor effect of therapy in Parkinson’s disease (PD) patients. In this study, we investigated serotonergic mechanisms in LIDs development in PD patients using 11C-DASB PET to evaluate serotonin terminal function and 11C-raclopride PET to evaluate dopamine release. PD patients with LIDs showed relative preservation of serotonergic terminals throughout their disease. Identical levodopa doses induced markedly higher striatal synaptic dopamine concentrations in PD patients with LIDs compared with PD patients with stable responses to levodopa. Oral administration of the serotonin receptor type 1A agonist buspirone prior to levodopa reduced levodopa-evoked striatal synaptic dopamine increases and attenuated LIDs. PD patients with LIDs that exhibited greater decreases in synaptic dopamine after buspirone pretreatment had higher levels of serotonergic terminal functional integrity. Buspirone-associated modulation of dopamine levels was greater in PD patients with mild LIDs compared with those with more severe LIDs. These findings indicate that striatal serotonergic terminals contribute to LIDs pathophysiology via aberrant processing of exogenous levodopa and release of dopamine as false neurotransmitter in the denervated striatum of PD patients with LIDs. Our results also support the development of selective serotonin receptor type 1A agonists for use as antidyskinetic agents in PD. PMID:24531549

Recovery of dopamine transporters with methamphetamine detoxification is not linked to changes in dopamine release

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volkow, Nora D.; Wang, Gene-Jack; Smith, Lisa

Metamphetamine’s widepread abuse and concerns that it may increase Parkinson’s disease led us to assess if the reported loss of dopamine transporters (DAT) in methamphetamine abusers (MA) reflected damage to dopamine neurons. Using PET with [ 11C]cocaine to measure DAT, and with [ 11C]raclopride to measure dopamine release (assessed as changes in specific binding of [ 11C]raclopride between placebo and methylphenidate), which was used as marker of dopamine neuronal function, we show that MA (n=16), tested during early detoxification, had lower DAT (20-30%) but overall normal DA release in striatum (except for a small decrease in left putamen), when comparedmore » to controls (n=15). In controls, DAT were positively correlated with DA release (higher DAT associated with larger DA increases), consistent with DAT serving as markers of DA terminals. In contrast, MA showed a trend for a negative correlation (p=0.07) (higher DAT associated with lower DA increases), consistent with reduced DA re-uptake following DAT downregulation. MA who remained abstinent nine-months later (n=9) showed significant increases in DAT (20%) but methylphenidate-induced dopamine increases did not change. In contrast, in controls, DAT did not change when retested 9 months later but methylphenidate-induced dopamine increases in ventral striatum were reduced (p=0.05). Baseline D2/D3 receptors in caudate were lower in MA than in controls and did not change with detoxification, nor did they change in the controls upon retest. The loss of DAT in the MA, which was not associated with a concomitant reduction in dopamine release as would have been expected if DAT loss reflected DA terminal degneration; as well as the recovery of DAT after protracted detoxification, which was not associated with increased dopamine release as would have been expected if DAT increases reflected terminal regeneration, indicate that the loss of DAT in these MA does not reflect degeneration of dopamine terminals.« less

Recovery of dopamine transporters with methamphetamine detoxification is not linked to changes in dopamine release.

PubMed

Volkow, Nora D; Wang, Gene-Jack; Smith, Lisa; Fowler, Joanna S; Telang, Frank; Logan, Jean; Tomasi, Dardo

2015-11-01

Methamphetamine's widepread abuse and concerns that it might increase Parkinson's disease led us to assess if the reported loss of dopamine transporters (DAT) in methamphetamine abusers (MA) reflected damage to dopamine neurons. Using PET with [(11)C]cocaine to measure DAT, and with [(11)C]raclopride to measure dopamine release (assessed as changes in specific binding of [(11)C]raclopride between placebo and methylphenidate), which was used as a marker of dopamine neuronal function, we show that MA (n=16), tested during early detoxification, had lower DAT (20-30%) but overall normal DA release in striatum (except for a small decrease in left putamen), when compared to controls (n=15). In controls, DAT were positively correlated with DA release (higher DAT associated with larger DA increases), consistent with DAT serving as markers of DA terminals. In contrast, MA showed a trend for a negative correlation (p=0.07) (higher DAT associated with lower DA increases), consistent with reduced DA re-uptake following DAT downregulation. MA who remained abstinent nine-months later (n=9) showed significant increases in DAT (20%) but methylphenidate-induced dopamine increases did not change. In contrast, in controls, DAT did not change when retested 9 months later but methylphenidate-induced dopamine increases in ventral striatum were reduced (p=0.05). Baseline D2/D3 receptors in caudate were lower in MA than in controls and did not change with detoxification, nor did they change in the controls upon retest. The loss of DAT in the MA, which was not associated with a concomitant reduction in dopamine release as would have been expected if DAT loss reflected DA terminal degneration; as well as the recovery of DAT after protracted detoxification, which was not associated with increased dopamine release as would have been expected if DAT increases reflected terminal regeneration, indicate that the loss of DAT in these MA does not reflect degeneration of dopamine terminals. Published by Elsevier Inc.

Recovery of dopamine transporters with methamphetamine detoxification is not linked to changes in dopamine release

DOE PAGES

Volkow, Nora D.; Wang, Gene-Jack; Smith, Lisa; ...

2015-07-21

Metamphetamine’s widepread abuse and concerns that it may increase Parkinson’s disease led us to assess if the reported loss of dopamine transporters (DAT) in methamphetamine abusers (MA) reflected damage to dopamine neurons. Using PET with [ 11C]cocaine to measure DAT, and with [ 11C]raclopride to measure dopamine release (assessed as changes in specific binding of [ 11C]raclopride between placebo and methylphenidate), which was used as marker of dopamine neuronal function, we show that MA (n=16), tested during early detoxification, had lower DAT (20-30%) but overall normal DA release in striatum (except for a small decrease in left putamen), when comparedmore » to controls (n=15). In controls, DAT were positively correlated with DA release (higher DAT associated with larger DA increases), consistent with DAT serving as markers of DA terminals. In contrast, MA showed a trend for a negative correlation (p=0.07) (higher DAT associated with lower DA increases), consistent with reduced DA re-uptake following DAT downregulation. MA who remained abstinent nine-months later (n=9) showed significant increases in DAT (20%) but methylphenidate-induced dopamine increases did not change. In contrast, in controls, DAT did not change when retested 9 months later but methylphenidate-induced dopamine increases in ventral striatum were reduced (p=0.05). Baseline D2/D3 receptors in caudate were lower in MA than in controls and did not change with detoxification, nor did they change in the controls upon retest. The loss of DAT in the MA, which was not associated with a concomitant reduction in dopamine release as would have been expected if DAT loss reflected DA terminal degneration; as well as the recovery of DAT after protracted detoxification, which was not associated with increased dopamine release as would have been expected if DAT increases reflected terminal regeneration, indicate that the loss of DAT in these MA does not reflect degeneration of dopamine terminals.« less

Functional recovery of supersensitive dopamine receptors after intrastriatal grafts of fetal substantia nigra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawson, T.M.; Dawson, V.L.; Gage, F.H.

1991-03-01

Interruption of the ascending dopamine neurons of the nigrostriatal pathway, by 6-hydroxydopamine (6-OHDA) lesion in rats, produced a significant loss of the dopamine transport complexes labeled with the phencyclidine derivative (3H)BTCP. This loss of dopamine innervation in the striatum was present at least 12 to 14 months after lesioning and was functionally manifested by ipsilateral rotation of the animals in response to amphetamine. In these same animals, in comparison to controls, there was a significant increase in the number (Bmax) of (3H)SCH 23390-labeled D-1 receptors in the striatum (36.7%) and the substantia nigra (35.1%) and a 54.4% increase in themore » number (Bmax) of (3H)sulpiride-labeled striatal D-2 receptors without an apparent change in affinity (Kd). Ten to twelve months after the transplantation of homologous fetal substantia nigra into the denervated striatum, there was a significant decrease in amphetamine-induced turning behavior. In these animals, there was an ingrowth of dopamine nerve terminals in the striatum as demonstrated by a return of (3H)BTCP binding. Accompanying this reinnervation was the normalization of D-1 and D-2 receptors to control values in the striatum as well as the return of D-1 receptors to prelesion densities in the substantia nigra. In a subgroup of transplanted rats, amphetamine continued to induce ipsilateral turning. In these animals both D-1 and D-2 receptors remained supersensitive. These results support the hypothesis that the functional recovery of transplanted animals is due, in part, to reinnervation of the striatum. In addition, long-term alterations in receptor density may be related to the behavioral deficits that are associated with the 6-OHDA-lesioned rat.« less

Adenosine A2A receptors modulate the dopamine D2 receptor-mediated inhibition of synaptic transmission in the mouse prefrontal cortex.

PubMed

Real, Joana I; Simões, Ana Patrícia; Cunha, Rodrigo A; Ferreira, Samira G; Rial, Daniel

2018-05-01

Prefrontal cortex (PFC) circuits are modulated by dopamine acting on D 1 - and D 2 -like receptors, which are pharmacologically exploited to manage neuropsychiatric conditions. Adenosine A 2A receptors (A 2 A R) also control PFC-related responses and A 2 A R antagonists are potential anti-psychotic drugs. As tight antagonistic A 2 A R-D 2 R and synergistic A 2 A R-D 1 R interactions occur in other brain regions, we now investigated the crosstalk between A 2 A R and D 1 /D 2 R controlling synaptic transmission between layers II/III and V in mouse PFC coronal slices. Dopamine decreased synaptic transmission, a presynaptic effect based on the parallel increase in paired-pulse responses. Dopamine inhibition was prevented by the D 2 R-like antagonist sulpiride but not by the D 1 R antagonist SCH23390 and was mimicked by the D 2 R agonist sumanirole, but not by the agonists of either D 4 R (A-412997) or D 3 R (PD128907). Dopamine inhibition was prevented by the A 2 A R antagonist, SCH58261, and attenuated in A 2 A R knockout mice. Accordingly, triple-labelling immunocytochemistry experiments revealed the co-localization of A 2 A R and D 2 R immunoreactivity in glutamatergic (vGluT1-positive) nerve terminals of the PFC. This reported positive A 2 A R-D 2 R interaction controlling PFC synaptic transmission provides a mechanistic justification for the anti-psychotic potential of A 2 A R antagonists. © 2018 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Response contingency directs long-term cocaine-induced neuroplasticity in prefrontal and striatal dopamine terminals.

PubMed

Wiskerke, Joost; Schoffelmeer, Anton N M; De Vries, Taco J

2016-10-01

Exposure to addictive substances such as cocaine is well-known to alter brain organisation. Cocaine-induced neuroadaptations depend on several factors, including drug administration paradigm. To date, studies addressing the consequences of cocaine exposure on dopamine transmission have either not been designed to investigate the role of response contingency or focused only on short-term neuroplasticity. We demonstrate a key role of response contingency in directing long-term cocaine-induced neuroplasticity throughout projection areas of the mesocorticolimbic dopamine system. We found enhanced electrically-evoked [(3)H]dopamine release from superfused brain slices of nucleus accumbens shell and core, dorsal striatum and medial prefrontal cortex three weeks after cessation of cocaine self-administration. In yoked cocaine rats receiving the same amount of cocaine passively, sensitised dopamine terminal reactivity was only observed in the nucleus accumbens core. Control sucrose self-administration experiments demonstrated that the observed neuroadaptations were not the result of instrumental learning per se. Thus, long-term withdrawal from cocaine self-administration is associated with widespread sensitisation of dopamine terminals throughout frontostriatal circuitries. Copyright © 2016 Elsevier B.V. and ECNP. All rights reserved.

Pretreatment With Fragments of Substance-P or With Cholecystokinin Differentially Affects Recovery From Sub-Total Nigrostriatal 6-Hydroxydopamine Lesion

PubMed Central

Nikolaus, S.; Huston, J. P.; Schwarting, R. K. W.

1999-01-01

The neuropeptide substance P is known to have mnemogenic and reinforcing actions and can exert neurotrophic and regenerative effects in vitro as well as in vivo. Furthermore, our previous work in the rat showed that either pre- or post-lesion treatment with substance P can promote functional recovery in cases of partial nigrostriatal dopamine lesions. Other work has provided evidence that the effects of substance P might be differentially encoded by its C- and N-terminal fragments. The C-terminal fragment was found to be reinforcing, whereas the mnemogenic as well as neurotrophic properties have been ascribed to the N-terminal sequences. Given these relations, we asked here whether pre-lesion treatment with either a C- or an N-terminal fragment of substance P might differentially affect the behavioral and neurochemical outcome of nigrostriatal dopamine lesions. Therefore, either substance P1−7 or substance P5−11 (37 nmol/kg each) was administered intraperitoneally daily for eight consecutive days before unilateral 6-hydroxy-dopamine lesions of the substantia nigra. Control rats received prelesion treatment with vehicle. Furthermore, we investigated the effects of pre-treatment with Boc-cholecystokinin-4 (0.91 nmol/kg), as we had found an increase in dopamine metabolism in animals that were pre-treated with cholecystokinin-8 in a former study. In accordance with our previous work, drug treatment effects were observed when excluding animals with most severe dopamine lesions: In animals with partial lesions (residual neostriatal dopamine levels of more than 10%), lesion-dependent asymmetries in turning behavior were observed in animals that were pre-treated with vehicle-, substance P1−7 , or Boc-cholecysto-kinin–4,. whereas turning after pre-treatment with substance P5−11 was not significantly asymmetrical. Furthermore, the ipsi- and contra-lateral neostriatal dopamine levels did not differ significantly in this group. Moreover, pre treatment with substance P5−11 affected dopamine metabolism in the neostriatum and in the venral striatum, as indicated by increased ratios of dihydroxyphenyllic acid to dopamine. The data provide the first evidence that the promotive effects of substance-P treatment in the unilateral dopamine lesion model might be mediated by its C-terminal and might depend on actions on residual dopamine mechanisms. PMID:10714262

Dopamine neurons in culture express VGLUT2 explaining their capacity to release glutamate at synapses in addition to dopamine.

PubMed

Dal Bo, Gregory; St-Gelais, Fannie; Danik, Marc; Williams, Sylvain; Cotton, Mathieu; Trudeau, Louis-Eric

2004-03-01

Dopamine neurons have been suggested to use glutamate as a cotransmitter. To identify the basis of such a phenotype, we have examined the expression of the three recently identified vesicular glutamate transporters (VGLUT1-3) in postnatal rat dopamine neurons in culture. We found that the majority of isolated dopamine neurons express VGLUT2, but not VGLUT1 or 3. In comparison, serotonin neurons express only VGLUT3. Single-cell RT-PCR experiments confirmed the presence of VGLUT2 mRNA in dopamine neurons. Arguing for phenotypic heterogeneity among axon terminals, we find that only a proportion of terminals established by dopamine neurons are VGLUT2-positive. Taken together, our results provide a basis for the ability of dopamine neurons to release glutamate as a cotransmitter. A detailed analysis of the conditions under which DA neurons gain or loose a glutamatergic phenotype may provide novel insight into pathophysiological processes that underlie diseases such as schizophrenia, Parkinson's disease and drug dependence.

Comparison of Glutamate Turnover in Nerve Terminals and Brain Tissue During [1,6-13C2]Glucose Metabolism in Anesthetized Rats.

PubMed

Patel, Anant B; Lai, James C K; Chowdhury, Golam I M; Rothman, Douglas L; Behar, Kevin L

2017-01-01

The 13 C turnover of neurotransmitter amino acids (glutamate, GABA and aspartate) were determined from extracts of forebrain nerve terminals and brain homogenate, and fronto-parietal cortex from anesthetized rats undergoing timed infusions of [1,6- 13 C 2 ]glucose or [2- 13 C]acetate. Nerve terminal 13 C fractional labeling of glutamate and aspartate was lower than those in whole cortical tissue at all times measured (up to 120 min), suggesting either the presence of a constant dilution flux from an unlabeled substrate or an unlabeled (effectively non-communicating on the measurement timescale) glutamate pool in the nerve terminals. Half times of 13 C labeling from [1,6- 13 C 2 ]glucose, as estimated by least squares exponential fitting to the time course data, were longer for nerve terminals (Glu C4 , 21.8 min; GABA C2 21.0 min) compared to cortical tissue (Glu C4 , 12.4 min; GABA C2 , 14.5 min), except for Asp C3 , which was similar (26.5 vs. 27.0 min). The slower turnover of glutamate in the nerve terminals (but not GABA) compared to the cortex may reflect selective effects of anesthesia on activity-dependent glucose use, which might be more pronounced in the terminals. The 13 C labeling ratio for glutamate-C4 from [2- 13 C]acetate over that of 13 C-glucose was twice as large in nerve terminals compared to cortex, suggesting that astroglial glutamine under the 13 C glucose infusion was the likely source of much of the nerve terminal dilution. The net replenishment of most of the nerve terminal amino acid pools occurs directly via trafficking of astroglial glutamine.

A study of the mechanisms involved in the neurotoxic action of 3,4-methylenedioxymethamphetamine (MDMA, ‘ecstasy') on dopamine neurones in mouse brain

PubMed Central

Colado, M Isabel; Camarero, Jorge; Mechan, Annis O; Sanchez, Veronica; Esteban, Blanca; Elliott, J Martin; Green, A Richard

2001-01-01

Administration of 3,4-methylenedioxymethamphetamine (MDMA, ‘ecstasy') to mice produces acute hyperthermia and long-term degeneration of striatal dopamine nerve terminals. Attenuation of the hyperthermia decreases the neurodegeneration. We have investigated the mechanisms involved in producing the neurotoxic loss of striatal dopamine. MDMA produced a dose-dependent loss in striatal dopamine concentration 7 days later with 3 doses of 25 mg kg−1 (3 h apart) producing a 70% loss. Pretreatment 30 min before each MDMA dose with either of the N-methyl-D-aspartate antagonists AR-R15896AR (20, 5, 5 mg kg−1) or MK-801 (0.5 mg kg−1×3) failed to provide neuroprotection. Pretreatment with clomethiazole (50 mg kg−1×3) was similarly ineffective in protecting against MDMA-induced dopamine loss. The free radical trapping compound PBN (150 mg kg−1×3) was neuroprotective, but it proved impossible to separate neuroprotection from a hypothermic effect on body temperature. Pretreatment with the nitric oxide synthase (NOS) inhibitor 7-NI (50 mg kg−1×3) produced neuroprotection, but also significant hypothermia. Two other NOS inhibitors, S-methyl-L-thiocitrulline (10 mg kg−1×3) and AR-R17477AR (5 mg kg−1×3), provided significant neuroprotection and had little effect on MDMA-induced hyperthermia. MDMA (20 mg kg−1) increased 2,3-dihydroxybenzoic acid formation from salicylic acid perfused through a microdialysis tube implanted in the striatum, indicating increased free radical formation. This increase was prevented by AR-R17477AR administration. Since AR-R17477AR was also found to have no radical trapping activity this result suggests that MDMA-induced neurotoxicity results from MDMA or dopamine metabolites producing radicals that combine with NO to form tissue-damaging peroxynitrites. PMID:11739248

The effectiveness of Hering's nerve stimulation in controlling penicillin-induced seizures in the rat is dependent on the amygdala.

PubMed

Tubbs, R Shane; Wellons, John C; Patwardhan, Ravish V; Oakes, W Jerry; Wyss, J Michael

2002-11-01

This study tests the hypothesis that the ability of Hering's nerve stimulation (HNS) to blunt seizure activity is dependent on the availability of dopamine in the amygdala. In 10 rats, Hering's nerve (HN) on the right side was isolated and placed on an electrode and penicillin was locally placed on each rat's left frontoparietal region to induce seizures. After the initiation of seizures, HN was stimulated. After the recurrence of seizure activity, the left basolateral amygdala was injected with 1.0 microl of normal saline, dopamine, haloperidol or 1% lidocaine in sequential tests. HN was stimulated after each injection and the latency and amplitude of the seizure activity were assessed. Focal cortical penicillin induced seizures that resulted in tonic-clonic movement of the limbs and face that lasted 35-45 min. Tonic-clonic movements of the limbs and face of similar latency and amplitude were induced by repeated reapplication of penicillin in untreated rats. HNS decreased seizure activity, but infusion of haloperidol or lidocaine into the basolateral amygdala blocked this antiseizure effect of HNS. In contrast, infusion of saline or dopamine had no effect on the ability of HNS to blunt seizure activity. None of the amygdala injections altered the latency or amplitude of seizure activity. These results demonstrate that the ability of HNS to blunt seizure activity in the rat is dependent on an intact dopamine system in the basolateral amygdala. These data will hopefully be useful in furthering our understanding of the circuitry that allows peripheral nerve stimulation to alter seizure activity. Copyright 2002 S. Karger AG, Basel

Role of alpha-synuclein in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonism in mice.

PubMed

Schlüter, O M; Fornai, F; Alessandrí, M G; Takamori, S; Geppert, M; Jahn, R; Südhof, T C

2003-01-01

In humans, mutations in the alpha-synuclein gene or exposure to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produce Parkinson's disease with loss of dopaminergic neurons and depletion of nigrostriatal dopamine. alpha-Synuclein is a vertebrate-specific component of presynaptic nerve terminals that may function in modulating synaptic transmission. To test whether MPTP toxicity involves alpha-synuclein, we generated alpha-synuclein-deficient mice by homologous recombination, and analyzed the effect of deleting alpha-synuclein on MPTP toxicity using these knockout mice. In addition, we examined commercially available mice that contain a spontaneous loss of the alpha-synuclein gene. As described previously, deletion of alpha-synuclein had no significant effects on brain structure or composition. In particular, the levels of synaptic proteins were not altered, and the concentrations of dopamine, dopamine metabolites, and dopaminergic proteins were unchanged. Upon acute MPTP challenge, alpha-synuclein knockout mice were partly protected from chronic depletion of nigrostriatal dopamine when compared with littermates of the same genetic background, whereas mice carrying the spontaneous deletion of the alpha-synuclein gene exhibited no protection. Furthermore, alpha-synuclein knockout mice but not the mice with the alpha-synuclein gene deletion were slightly more sensitive to methamphetamine than littermate control mice. These results demonstrate that alpha-synuclein is not obligatorily coupled to MPTP sensitivity, but can influence MPTP toxicity on some genetic backgrounds, and illustrate the need for extensive controls in studies aimed at describing the effects of mouse knockouts on MPTP sensitivity.

The foetal pig pineal gland is richly innervated by nerve fibres containing catecholamine-synthesizing enzymes, neuropeptide Y (NPY) and C-terminal flanking peptide of NPY, but it does not secrete melatonin.

PubMed

Bulc, Michał; Lewczuk, Bogdan; Prusik, Magdalena; Całka, Jarosław

2013-05-01

Innervation of the mammalian pineal gland during prenatal development is poorly recognized. Therefore, immunofluorescence studies of the pineals of 70- and 90-day-old foetuses of the domestic pig were performed using antibodies against tyrosine hydroxylase (TH), dopamine-β-hydroxylase (DβH), neuropeptide Y (NPY) and C-terminal flanking peptide of NPY (CPON). The investigated glands were supplied by numerous nerve fibres containing TH and DβH. The density of these fibres was higher in the distal and middle parts of the gland than in the proximal one. NPY and CPON were identified in the majority of DβH-positive fibres as well as in a small population of DβH-negative fibres localized mainly in the proximal part of the pineal. The immunoreactive fibres were more numerous in 90-day-old foetuses than in 70-day-old ones. The effect of norepinephrine on melatonin secretion by the foetal pineals in the short-term organ culture was studied to determine the role of DβH-positive fibres during prenatal life. For the same purpose melatonin was measured in the blood in the umbilical cords and in the jugular vein of the mother. The pineals of both groups of foetuses did not secrete melatonin in the organ culture, independently of the presence or absence of norepinephrine in the medium. Melatonin concentrations in the blood in the umbilical cords of foetuses from the same litter and in the jugular vein of their mother were similar. The presence of adrenergic nerve fibres in the pig pineal during gestation does not seem to be associated with the control of melatonin secretion.

Toward development of an in vitro model of methamphetamine-induced dopamine nerve terminal toxicity.

PubMed

Kim, S; Westphalen, R; Callahan, B; Hatzidimitriou, G; Yuan, J; Ricaurte, G A

2000-05-01

To develop an in vitro model of methamphetamine (METH)-induced dopamine (DA) neurotoxicity, striatal synaptosomes were incubated at 37 degrees C with METH for different periods of time (10-80 min), washed once, then tested for DA transporter function at 37 degrees C. METH produced time- and dose-dependent reductions in the V(max) of DA uptake, without producing any change in K(m). Incubation of synaptosomes with the DA neurotoxins 1-methyl-4-phenyl-pyridinium ion, 6-hydroxydopamine, and amphetamine under similar conditions produced comparable effects. In contrast, incubation with fenfluramine, a serotonin neurotoxin, did not. METH-induced decreases in DA uptake were selective, insofar as striatal glutamate uptake was unaffected. Various DA transporter blockers (cocaine, methylphenidate, and bupropion) afforded complete protection against METH-induced decreases in DA uptake, without producing any effect themselves. METH's effects were also temperature dependent, with greater decreases in DA uptake occurring at higher temperatures. Tests for residual drug revealed small amounts (0.1-0.2 microM) of remaining METH, but kinetic studies indicated that decreases in DA uptake were not likely to be due to METH acting as a competitive inhibitor of DA uptake. Decreases in the V(max) of DA uptake were not accompanied by decreases in B(max) of [(3)H]WIN 35,428 binding, possibly because there is no mechanism for removing damaged DA nerve endings from the in vitro preparation Collectively, these results give good support to the development of a valid in vitro model that may prove helpful for elucidating the mechanisms underlying METH-induced DA neurotoxicity.

RELATIVE ACTIONS OF QUATERNARY METHYL DERIVATIVES OF TYRAMINE, DOPAMINE AND NORADRENALINE.

PubMed

CUTHBERT, M F

1964-08-01

Tyramine methiodide and dopamine methobromide have greater pressor effect (three- to five-times) in the spinal cat than the parent amines. Noradrenaline methochloride has little pressor effect. Dopamine methobromide is about four times as potent as nicotine; tyramine methiodide is about equiactive to nicotine; and noradrenaline methochloride has only one-tenth the potency of nicotine. Their pressor effects are usually abolished by hexamethonium but in some experiments the effect of noradrenaline methochloride persisted and was then abolished by tolazoline. Injected intravenously into the cat anaesthetized with chloralose, each of the three quaternary derivatives contracts the nictitating membrane; dopamine methobromide is again the most active, having more than six times the potency of nicotine. When the contractions of the nictitating membrane are induced by continuous stimulation of the preganglionic fibres of the cervical sympathetic nerve, intravenous injection of the quaternary derivatives of tyramine and dopamine has a biphasic effect; there is a block on which a contraction of the membrane appears to be superimposed. Noradrenaline methochloride produces only a further contraction of the membrane. On the isolated rectus abdominis muscle preparation of the frog, dopamine methobromide is the most active in contracting the muscle, being about twelve times as active as nicotine; noradrenaline methochloride is weakest, having only one-hundredth the activity of nicotine. These effects are antagonized by hexamethonium. On the isolated phrenic nerve-diaphragm preparation of the rat, the quaternary derivatives of tyramine and dopamine each have neuromuscular blocking properties, 0.7- and 3-times respectively that of nicotine. Noradrenaline methochloride has no effect. In the sciatic nerve-tibialis preparation of the cat, the quaternary derivatives of tyramine and dopamine are approximately equipotent in producing neuromuscular paralysis, having about three times the activity of nicotine and one-fifth that of suxamethonium. These effects are not antagonized either by neostigmine or by edrophonium. Noradrenaline methochloride has no neuromuscular blocking effect. The nicotine-like properties of these quaternized sympathomimetic amines are discussed. It is of interest that the presence of an hydroxyl group attached to the beta-carbon atom of the side-chain greatly reduces nicotine-like activity. By comparison, choline had about one forty-fifth the pressor activity of ethyltrimethylammonium.

Relative actions of quaternary methyl derivatives of tyramine, dopamine and noradrenaline

PubMed Central

Cuthbert, M. F.

1964-01-01

Tyramine methiodide and dopamine methobromide have greater pressor effect (three- to five-times) in the spinal cat than the parent amines. Noradrenaline methochloride has little pressor effect. Dopamine methobromide is about four times as potent as nicotine; tyramine methiodide is about equiactive to nicotine; and noradrenaline methochloride has only one-tenth the potency of nicotine. Their pressor effects are usually abolished by hexamethonium but in some experiments the effect of noradrenaline methochloride persisted and was then abolished by tolazoline. Injected intravenously into the cat anaesthetized with chloralose, each of the three quaternary derivatives contracts the nictitating membrane; dopamine methobromide is again the most active, having more than six times the potency of nicotine. When the contractions of the nictitating membrane are induced by continuous stimulation of the preganglionic fibres of the cervical sympathetic nerve, intravenous injection of the quaternary derivatives of tyramine and dopamine has a biphasic effect; there is a block on which a contraction of the membrane appears to be superimposed. Noradrenaline methochloride produces only a further contraction of the membrane. On the isolated rectus abdominis muscle preparation of the frog, dopamine methobromide is the most active in contracting the muscle, being about twelve times as active as nicotine; noradrenaline methochloride is weakest, having only one-hundredth the activity of nicotine. These effects are antagonized by hexamethonium. On the isolated phrenic nerve-diaphragm preparation of the rat, the quaternary derivatives of tyramine and dopamine each have neuromuscular blocking properties, 0.7- and 3-times respectively that of nicotine. Noradrenaline methochloride has no effect. In the sciatic nerve-tibialis preparation of the cat, the quaternary derivatives of tyramine and dopamine are approximately equipotent in producing neuromuscular paralysis, having about three times the activity of nicotine and one-fifth that of suxamethonium. These effects are not antagonized either by neostigmine or by edrophonium. Noradrenaline methochloride has no neuromuscular blocking effect. The nicotine-like properties of these quaternized sympathomimetic amines are discussed. It is of interest that the presence of an hydroxyl group attached to the β-carbon atom of the side-chain greatly reduces nicotine-like activity. By comparison, choline had about one forty-fifth the pressor activity of ethyltrimethylammonium. PMID:14206269

Ubiquitin–Synaptobrevin Fusion Protein Causes Degeneration of Presynaptic Motor Terminals in Mice

PubMed Central

Liu, Yun; Li, Hongqiao; Sugiura, Yoshie; Han, Weiping; Gallardo, Gilbert; Khvotchev, Mikhail; Zhang, Yinan; Kavalali, Ege T.; Südhof, Thomas C.

2015-01-01

Protein aggregates containing ubiquitin (Ub) are commonly observed in neurodegenerative disorders, implicating the involvement of the ubiquitin proteasome system (UPS) in their pathogenesis. Here, we aimed to generate a mouse model for monitoring UPS function using a green fluorescent protein (GFP)-based substrate that carries a “noncleavable” N-terminal ubiquitin moiety (UbG76V). We engineered transgenic mice expressing a fusion protein, consisting of the following: (1) UbG76V, GFP, and a synaptic vesicle protein synaptobrevin-2 (UbG76V-GFP-Syb2); (2) GFP-Syb2; or (3) UbG76V-GFP-Syntaxin1, all under the control of a neuron-specific Thy-1 promoter. As expected, UbG76V-GFP-Syb2, GFP-Syb2, and UbG76V-GFP-Sytaxin1 were highly expressed in neurons, such as motoneurons and motor nerve terminals of the neuromuscular junction (NMJ). Surprisingly, UbG76V-GFP-Syb2 mice developed progressive adult-onset degeneration of motor nerve terminals, whereas GFP-Syb2 and UbG76V-GFP-Syntaxin1 mice were normal. The degeneration of nerve terminals in UbG76V-GFP-Syb2 mice was preceded by a progressive impairment of synaptic transmission at the NMJs. Biochemical analyses demonstrated that UbG76V-GFP-Syb2 interacted with SNAP-25 and Syntaxin1, the SNARE partners of synaptobrevin. Ultrastructural analyses revealed a marked reduction in synaptic vesicle density, accompanying an accumulation of tubulovesicular structures at presynaptic nerve terminals. These morphological defects were largely restricted to motor nerve terminals, as the ultrastructure of motoneuron somata appeared to be normal at the stages when synaptic nerve terminals degenerated. Furthermore, synaptic vesicle endocytosis and membrane trafficking were impaired in UbG76V-GFP-Syb2 mice. These findings indicate that UbG76V-GFP-Syb2 may compete with endogenous synaptobrevin, acting as a gain-of-function mutation that impedes SNARE function, resulting in the depletion of synaptic vesicles and degeneration of the nerve terminals. SIGNIFICANCE STATEMENT Degeneration of motor nerve terminals occurs in amyotrophic lateral sclerosis (ALS) patients as well as in mouse models of ALS, leading to progressive paralysis. What causes a motor nerve terminal to degenerate remains unknown. Here we report on transgenic mice expressing a ubiquitinated synaptic vesicle protein (UbG76V-GFP-Syb2) that develop progressive degeneration of motor nerve terminals. These mice may serve as a model for further elucidating the underlying cellular and molecular mechanisms of presynaptic nerve terminal degeneration. PMID:26290230

METHAMPHETAMINE-INDUCED CELL DEATH: SELECTIVE VULNERABILITY IN NEURONAL SUBPOPULATIONS OF THE STRIATUM IN MICE

PubMed Central

ZHU, J. P. Q.; XU, W.; ANGULO, J. A.

2010-01-01

Methamphetamine (METH) is an illicit and potent psychostimulant, which acts as an indirect dopamine agonist. In the striatum, METH has been shown to cause long lasting neurotoxic damage to dopaminergic nerve terminals and recently, the degeneration and death of striatal cells. The present study was undertaken to identify the type of striatal neurons that undergo apoptosis after METH. Male mice received a single high dose of METH (30 mg/kg, i.p.) and were killed 24 h later. To demonstrate that METH induces apoptosis in neurons, we combined terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining with immunohistofluorescence for the neuronal marker neuron-specific nuclear protein (NeuN). Staining for TUNEL and NeuN was colocalized throughout the striatum. METH induces apoptosis in approximately 25% of striatal neurons. Cell counts of TUNEL-positive neurons in the dorsomedial, ventromedial, dorsolateral and ventrolateral quadrants of the striatum did not reveal anatomical preference. The type of striatal neuron undergoing cell death was determined by combining TUNEL with immunohistofluorescence for selective markers of striatal neurons: dopamine- and cAMP-regulated phosphoprotein, of apparent Mr 32,000, parvalbumin, choline acetyltransferase and somatostatin (SST). METH induces apoptosis in approximately 21% of dopamine- and cAMP-regulated phosphoprotein, of apparent Mr 32,000-positive neurons (projection neurons), 45% of GABA-parvalbumin-positive neurons in the dorsal striatum, and 29% of cholinergic neurons in the dorsal–medial striatum. In contrast, the SST-positive interneurons were refractory to METH-induced apoptosis. Finally, the amount of cell loss determined with Nissl staining correlated with the amount of TUNEL staining in the striatum of METH-treated animals. In conclusion, some of the striatal projection neurons and the GABA-parvalbumin and cholinergic interneurons were removed by apoptosis in the aftermath of METH. This imbalance in the populations of striatal neurons may lead to functional abnormalities in the output and processing of neural information in this part of the brain. PMID:16650608

Central projections of the lateral line and eighth nerves in the bowfin, Amia calva.

PubMed

McCormick, C A

1981-03-20

The first-order connections of the anterior and posterior lateral line nerves and of the eighth nerve were determined in the bowfin, Amia calva, using experimental degeneration and anterograde HRP transport techniques. The termination sites of these nerves define a dorsal lateralis cell column and a ventral octavus cell column. The anterior and posterior lateralis nerves distribute ipsilaterally to two medullary nuclei-nucleus medialis and nucleus caudalis. Nucleus medialis comprises the rostral two-thirds of the lateralis column and contains large, Purkinje-like cells dorsally and polygonal, granule, and fusiform cells ventrally. Nucleus caudalis is located posterior to nucleus medialis and consists of small, granule cells. Anterior lateralis fibers terminate ventrally to ventromedially in both nucleus medialis and nucleus caudalis. Posterior lateralis fibers terminate dorsally to dorsolaterally within these two nuclei. A sparse anterior lateralis input may also be present on the dendrites of one of the nuclei within the octavus cell column, nucleus magnocellularis. In contrast, the anterior and posterior rami of the eighth nerve each terminate within four medullary nuclei which comprise the octavus cell column: the anterior, magnocellular, descending, and posterior octavus nuclei. An eighth nerve projection to the medial reticular formation is also present. Some fibers of the lateralis and eighth nerves terminate within the ipsilateral eminentia granularis of the cerebellum. Lateralis fibers distribute to approximately the lateral half of this structure with posterior lateral line fibers terminating laterally and anterior lateral line fibers terminating medially. Eighth nerve fibers distribute to the medial half of the eminentia granularis.

Inhibition of the sympathetic nervous system by a series of heterocyclic congeners of dopamine.

PubMed

Sharabi, F M; Long, J P; Cannon, J G; Hatheway, G J

1976-12-01

A series of heterocyclic congeners of dopamine (GJH-series) with different positions of phenolic oxygens and with the possibility of cis and trans isomerism at the 4a-10b ring juncture was evaluated in vitro and in vivo for dopaminergic activity. Two compounds, GJH-166 and GJH-171, were found to suppress the positive chronotropic response induced by stimulation of the right cardioaccelerator nerves. These effects were antagonized by haloperidol. GJH-166, in doses as low as 9.5 x 10(-4) mugmol/kg reduced the resting heart rate in cats anesthetized with alpha-chloralose. GJH-166 and GJH-171 antagonized pressor responses induced by bilateral carotid occlusion and stimulation of the central stump of the sciatic nerve. The results outlined in this manuscript support the hypothesis that the extended conformation of the dihydroxyhenylethylamine moiety of dopamine with a trans isomeric form is favorable for dopaminergic agonist activity.

Mephedrone Does not Damage Dopamine Nerve Endings of the Striatum but Enhances the Neurotoxicity of Methamphetamine, Amphetamine and MDMA

PubMed Central

Angoa-Pérez, Mariana; Kane, Michael J.; Briggs, Denise I.; Francescutti, Dina M.; Sykes, Catherine E.; Shah, Mrudang M.; Thomas, David M.; Kuhn, Donald M.

2012-01-01

Mephedrone (4-methylmethcathinone) is a β-ketoamphetamine stimulant drug of abuse with close structural and mechanistic similarities to methamphetamine. One of the most powerful actions associated with mephedrone is the ability to stimulate dopamine (DA) release and block its reuptake through its interaction with the dopamine transporter (DAT). Although mephedrone does not cause toxicity to DA nerve endings, its ability to serve as a DAT blocker could provide protection against methamphetamine-induced neurotoxicity like other DAT inhibitors. To test this possibility, mice were treated with mephedrone (10, 20 or 40 mg/kg) prior to each injection of a neurotoxic regimen of methamphetamine (4 injections of 2.5 or 5.0 mg/kg at 2 hr intervals). The integrity of DA nerve endings of the striatum was assessed through measures of DA, DAT and tyrosine hydroxylase levels. The moderate to severe DA toxicity associated with the different doses of methamphetamine was not prevented by any dose of mephedrone but was, in fact, significantly enhanced. The hyperthermia caused by combined treatment with mephedrone and methamphetamine was the same as seen after either drug alone. Mephedrone also enhanced the neurotoxic effects of amphetamine and MDMA on DA nerve endings. In contrast, nomifensine protected against methamphetamine-induced neurotoxicity. Because mephedrone increases methamphetamine neurotoxicity, the present results suggest that it interacts with the DAT in a manner unlike that of other typical DAT inhibitors. The relatively innocuous effects of mephedrone alone on DA nerve endings mask a potentially dangerous interaction with drugs that are often co-abused with it, leading to heightened neurotoxicity. PMID:23205838

Acute corneal epithelial debridement unmasks the corneal stromal nerve responses to ocular stimulation in rats: implications for abnormal sensations of the eye.

PubMed

Hirata, Harumitsu; Mizerska, Kamila; Dallacasagrande, Valentina; Guaiquil, Victor H; Rosenblatt, Mark I

2017-05-01

It is widely accepted that the mechanisms for transducing sensory information reside in the nerve terminals. Occasionally, however, studies have appeared demonstrating that similar mechanisms may exist in the axon to which these terminals are connected. We examined this issue in the cornea, where nerve terminals in the epithelial cell layers are easily accessible for debridement, leaving the underlying stromal (axonal) nerves undisturbed. In isoflurane-anesthetized rats, we recorded extracellularly from single trigeminal ganglion neurons innervating the cornea that are excited by ocular dryness and cooling: low-threshold (<2°C cooling) and high-threshold (>2°C) cold-sensitive plus dry-sensitive neurons playing possible roles in tearing and ocular pain. We found that the responses in both types of neurons to dryness, wetness, and menthol stimuli were effectively abolished by the debridement, indicating that their transduction mechanisms lie in the nerve terminals. However, some responses to the cold, heat, and hyperosmolar stimuli in low-threshold cold-sensitive plus dry-sensitive neurons still remained. Surprisingly, the responses to heat in approximately half of the neurons were augmented after the debridement. We were also able to evoke these residual responses and follow the trajectory of the stromal nerves, which we subsequently confirmed histologically. The residual responses always disappeared when the stromal nerves were cut at the limbus, suggesting that the additional transduction mechanisms for these sensory modalities originated most likely in stromal nerves. The functional significance of these residual and enhanced responses from stromal nerves may be related to the abnormal sensations observed in ocular disease. NEW & NOTEWORTHY In addition to the traditional view that the sensory transduction mechanisms exist in the nerve terminals, we report here that the proximal axons (stromal nerves in the cornea from which these nerve terminals originate) may also be capable of transducing sensory information. We arrived at this conclusion by removing the epithelial cell layers of the cornea in which the nerve terminals reside but leaving the underlying stromal nerves undisturbed. Copyright © 2017 the American Physiological Society.

Acute corneal epithelial debridement unmasks the corneal stromal nerve responses to ocular stimulation in rats: implications for abnormal sensations of the eye

PubMed Central

Mizerska, Kamila; Dallacasagrande, Valentina; Guaiquil, Victor H.; Rosenblatt, Mark I.

2017-01-01

It is widely accepted that the mechanisms for transducing sensory information reside in the nerve terminals. Occasionally, however, studies have appeared demonstrating that similar mechanisms may exist in the axon to which these terminals are connected. We examined this issue in the cornea, where nerve terminals in the epithelial cell layers are easily accessible for debridement, leaving the underlying stromal (axonal) nerves undisturbed. In isoflurane-anesthetized rats, we recorded extracellularly from single trigeminal ganglion neurons innervating the cornea that are excited by ocular dryness and cooling: low-threshold (<2°C cooling) and high-threshold (>2°C) cold-sensitive plus dry-sensitive neurons playing possible roles in tearing and ocular pain. We found that the responses in both types of neurons to dryness, wetness, and menthol stimuli were effectively abolished by the debridement, indicating that their transduction mechanisms lie in the nerve terminals. However, some responses to the cold, heat, and hyperosmolar stimuli in low-threshold cold-sensitive plus dry-sensitive neurons still remained. Surprisingly, the responses to heat in approximately half of the neurons were augmented after the debridement. We were also able to evoke these residual responses and follow the trajectory of the stromal nerves, which we subsequently confirmed histologically. The residual responses always disappeared when the stromal nerves were cut at the limbus, suggesting that the additional transduction mechanisms for these sensory modalities originated most likely in stromal nerves. The functional significance of these residual and enhanced responses from stromal nerves may be related to the abnormal sensations observed in ocular disease. NEW & NOTEWORTHY In addition to the traditional view that the sensory transduction mechanisms exist in the nerve terminals, we report here that the proximal axons (stromal nerves in the cornea from which these nerve terminals originate) may also be capable of transducing sensory information. We arrived at this conclusion by removing the epithelial cell layers of the cornea in which the nerve terminals reside but leaving the underlying stromal nerves undisturbed. PMID:28250152

Methamphetamine-induced hyperthermia and dopaminergic neurotoxicity in mice: pharmacological profile of protective and nonprotective agents.

PubMed

Albers, D S; Sonsalla, P K

1995-12-01

Neurotoxic doses of methamphetamine (METH) can cause hyperthermia in experimental animals. Damage sustained to dopaminergic nerve terminals by this stimulant can be reduced by environmental cooling or by pharmacological manipulation which attenuates the hyperthermia. Many pharmacological agents with very diverse actions protect against METH-induced neuropathology. Several of these compounds, as well as drugs which do not protect, were investigated to determine if there was a relationship between protection and METH-induced hyperthermia. Mice received METH with or without concurrent administration of other drugs and core (i.e., colonic) temperature was monitored during treatment. The animals were sacrificed > or = 5 days later and neostriatal tyrosine hydroxylase activity and dopamine were measured. Core temperature was significantly elevated (> or = 2 degrees C) in mice treated with doses of METH which produced > or = 90% losses in striatal dopamine but not in mice less severally affected (only 50% loss of dopamine). Concurrent treatment of mice with METH and pharmacological agents which protected partially or completely from METH-induced toxicity also prevented the hyperthermic response (i.e., dopamine receptor antagonists, fenfluramine, dizocilpine, alpha-methyl-p-tyrosine, phenytoin, aminooxyacetic acid and propranol). These findings are consistent with the hypothesis that the hyperthermia produced by METH contributes to its neuropathology. However, studies with reserpine, a compound which dramatically lowers core temperature, demonstrated that hyperthermia per se is not a requirement for METH-induced neurotoxicity. Although core temperature was elevated in reserpinized mice treated with METH as compared with reserpinized control mice, their temperatures remained significantly lower than in nonreserpinized control mice. However, the hypothermic state produced in the reserpinized mice did not provide protection from METH-induced toxicity. These data demonstrate that hyperthermia per se contributes to but is not solely responsible for the METH-induced neuropathology.

High Fat Diet Augments Amphetamine Sensitization in Mice: Role of Feeding Pattern, Obesity, and Dopamine Terminal Changes

PubMed Central

Fordahl, Steve C.; Locke, Jason L.; Jones, Sara R.

2016-01-01

High fat (HF) diet-induced obesity has been shown to augment behavioral responses to psychostimulants that target the dopamine system. The purpose of this study was to characterize dopamine terminal changes induced by a HF diet that correspond with enhanced locomotor sensitization to amphetamine. C57BL/6J mice had limited (2hr 3d/week) or extended (24h 7d/week) access to a HF diet or standard chow for six weeks. Mice were then repeatedly exposed to amphetamine (AMPH), and their locomotor responses to an amphetamine challenge were measured. Fast scan cyclic voltammetry was used to identify changes in dopamine terminal function after AMPH exposure. Exposure to a HF diet reduced dopamine uptake and increased locomotor responses to acute, high-dose AMPH administration compared to chow fed mice. Microdialysis showed elevated extracellular dopamine in the nucleus accumbens (NAc) coincided with enhanced locomotion after acute AMPH in HF-fed mice. All mice exhibited locomotor sensitization to amphetamine, but both extended and limited access to a HF diet augmented this response. Neither HF-fed group showed the robust amphetamine sensitization-induced increases in dopamine release, reuptake, and amphetamine potency observed in chow fed animals. However, the potency of amphetamine as an uptake inhibitor was significantly elevated after sensitization in mice with extended (but not limited) access to HF. Conversely, after amphetamine sensitization, mice with limited (but not extended) access to HF displayed reduced autoreceptor sensitivity to the D2/D3 agonist quinpirole. Additionally, we observed reduced membrane dopamine transporter (DAT) levels after HF, and a shift in DAT localization to the cytosol was detected with limited access to HF. This study showed that different patterns of HF exposure produced distinct dopamine terminal adaptations to repeated AMPH, which differed from chow fed mice, and enhanced sensitization to AMPH. Locomotor sensitization in chow fed mice coincided with elevated DAT function and increased AMPH potency; however, the enhanced behavioral response to AMPH after HF exposure was unique in that it coincided with reduced DAT function and diet pattern-specific adaptations. PMID:27267686

Association of dopamine transporter reduction with psychomotor impairment in methamphetamine abusers.

PubMed

Volkow, N D; Chang, L; Wang, G J; Fowler, J S; Leonido-Yee, M; Franceschi, D; Sedler, M J; Gatley, S J; Hitzemann, R; Ding, Y S; Logan, J; Wong, C; Miller, E N

2001-03-01

Methamphetamine is a popular and highly addictive drug of abuse that has raised concerns because it has been shown in laboratory animals to be neurotoxic to dopamine terminals. The authors evaluated if similar changes occur in humans and assessed if they were functionally significant. Positron emission tomography scans following administration of [(11)C]d-threo-methylphenidate (a dopamine transporter ligand) measured dopamine transporter levels (a marker of dopamine cell terminals) in the brains of 15 detoxified methamphetamine abusers and 18 comparison subjects. Neuropsychological tests were also performed to assess motor and cognitive function. Methamphetamine abusers showed significant dopamine transporter reduction in the striatum (mean differences of 27.8% in the caudate and 21.1% in the putamen) relative to the comparison subjects; this reduction was evident even in abusers who had been detoxified for at least 11 months. Dopamine transporter reduction was associated with motor slowing and memory impairment. These results provide evidence that methamphetamine at dose levels taken by human abusers of the drug leads to dopamine transporter reduction that is associated with motor and cognitive impairment. These results emphasize the urgency of alerting clinicians and the public of the long-term changes that methamphetamine can induce in the human brain.

Development of the terminal nerve system in the shark Scyliorhinus canicula.

PubMed

Quintana-Urzainqui, Idoia; Anadón, Ramón; Candal, Eva; Rodríguez-Moldes, Isabel

2014-01-01

The nervus terminalis (or terminal nerve) system was discovered in an elasmobranch species more than a century ago. Over the past century, it has also been recognized in other vertebrate groups, from agnathans to mammals. However, its origin, functions or relationship with the olfactory system are still under debate. Despite the abundant literature about the nervus terminalis system in adult elasmobranchs, its development has been overlooked. Studies in other vertebrates have reported newly differentiated neurons of the terminal nerve system migrating from the olfactory epithelium to the telencephalon as part of a 'migratory mass' of cells associated with the olfactory nerve. Whether the same occurs in developing elasmobranchs (adults showing anatomically separated nervus terminalis and olfactory systems) has not yet been determined. In this work we characterized for the first time the development of the terminal nerve and ganglia in an elasmobranch, the lesser spotted dogfish (Scyliorhinus canicula), by means of tract-tracing techniques combined with immunohistochemical markers for the terminal nerve (such as FMRF-amide peptide), for the developing components of the olfactory system (Gα0 protein, GFAP, Pax6), and markers for early postmitotic neurons (HuC/D) and migrating immature neurons (DCX). We discriminated between embryonic olfactory and terminal nerve systems and determined that both components may share a common origin in the migratory mass. We also localized the exact point where they split off near the olfactory nerve-olfactory bulb junction. The study of the development of the terminal nerve system in a basal gnathostome contributes to the knowledge of the ancestral features of this system in vertebrates, shedding light on its evolution and highlighting the importance of elasmobranchs for developmental and evolutionary studies. © 2014 S. Karger AG, Basel.

Volume Transmission in Central Dopamine and Noradrenaline Neurons and Its Astroglial Targets.

PubMed

Fuxe, Kjell; Agnati, Luigi F; Marcoli, Manuela; Borroto-Escuela, Dasiel O

2015-12-01

Already in the 1960s the architecture and pharmacology of the brainstem dopamine (DA) and noradrenaline (NA) neurons with formation of vast numbers of DA and NA terminal plexa of the central nervous system (CNS) indicated that they may not only communicate via synaptic transmission. In the 1980s the theory of volume transmission (VT) was introduced as a major communication together with synaptic transmission in the CNS. VT is an extracellular and cerebrospinal fluid transmission of chemical signals like transmitters, modulators etc. moving along energy gradients making diffusion and flow of VT signals possible. VT interacts with synaptic transmission mainly through direct receptor-receptor interactions in synaptic and extrasynaptic heteroreceptor complexes and their signaling cascades. The DA and NA neurons are specialized for extrasynaptic VT at the soma-dendrtitic and terminal level. The catecholamines released target multiple DA and adrenergic subtypes on nerve cells, astroglia and microglia which are the major cell components of the trophic units building up the neural-glial networks of the CNS. DA and NA VT can modulate not only the strength of synaptic transmission but also the VT signaling of the astroglia and microglia of high relevance for neuron-glia interactions. The catecholamine VT targeting astroglia can modulate the fundamental functions of astroglia observed in neuroenergetics, in the Glymphatic system, in the central renin-angiotensin system and in the production of long-distance calcium waves. Also the astrocytic and microglial DA and adrenergic receptor subtypes mediating DA and NA VT can be significant drug targets in neurological and psychiatric disease.

Overexpression of parkin in the rat nigrostriatal dopamine system protects against methamphetamine neurotoxicity.

PubMed

Liu, Bin; Traini, Roberta; Killinger, Bryan; Schneider, Bernard; Moszczynska, Anna

2013-09-01

Methamphetamine (METH) is a central nervous system psychostimulant with a high potential for abuse. At high doses, METH causes a selective degeneration of dopaminergic terminals in the striatum, sparing other striatal terminals and cell bodies. We previously detected a deficit in parkin after binge METH in rat striatal synaptosomes. Parkin is an ubiquitin-protein E3 ligase capable of protecting dopamine neurons from diverse cellular insults. Whether the deficit in parkin mediates the toxicity of METH and whether parkin can protect from toxicity of the drug is unknown. The present study investigated whether overexpression of parkin attenuates degeneration of striatal dopaminergic terminals exposed to binge METH. Parkin overexpression in rat nigrostriatal dopamine system was achieved by microinjection of adeno-associated viral transfer vector 2/6 encoding rat parkin (AAV2/6-parkin) into the substantia nigra pars compacta. The microinjections of AAV2/6-parkin dose-dependently increased parkin levels in both the substantia nigra pars compacta and striatum. The levels of dopamine synthesizing enzyme, tyrosine hydroxylase, remained at the control levels; therefore, tyrosine hydroxylase immunoreactivity was used as an index of dopaminergic terminal integrity. In METH-exposed rats, the increase in parkin levels attenuated METH-induced decreases in striatal tyrosine hydroxylase immunoreactivity in a dose-dependent manner, indicating that parkin can protect striatal dopaminergic terminals against METH neurotoxicity. Copyright © 2013 Elsevier Inc. All rights reserved.

Overexpression of parkin in rat nigrostriatal dopamine system protects against methamphetamine neurotoxicity

PubMed Central

Liu, Bin; Traini, Roberta; Killinger, Bryan; Schneider, Bernard; Moszczynska, Anna

2013-01-01

Methamphetamine (METH) is a central nervous system psychostimulant with a high potential for abuse. At high doses, METH causes a selective degeneration of dopaminergic terminals in the striatum, sparing other striatal terminals and cell bodies. We previously detected a deficit in parkin after binge METH in rat striatal synaptosomes. Parkin is an ubiquitin-protein E3 ligase capable of protecting dopamine neurons from diverse cellular insults. Whether the deficit in parkin mediates the toxicity of METH and whether parkin can protect from toxicity of the drug is unknown. The present study investigated whether overexpression of parkin attenuates degeneration of striatal dopaminergic terminals exposed to binge METH. Parkin overexpression in rat nigrostriatal dopamine system was achieved by microinjection of adeno-associated viral transfer vector 2/6 encoding rat parkin (AAV2/6-parkin) into the substantia nigra pars compacta. The microinjections of AAV2/6-parkin dose-dependently increased parkin levels in both the substantia nigra pars compacta and striatum. The levels of dopamine synthesizing enzyme, tyrosine hydroxylase, remained at the control levels; therefore, tyrosine hydroxylase immunoreactivity was used as an index of dopaminergic terminal integrity. In METH-exposed rats, the increase in parkin levels attenuated METH-induced decreases in striatal tyrosine hydroxylase immunoreactivity in a dose-dependent manner, indicating that parkin can protect striatal dopaminergic terminals against METH neurotoxicity. PMID:23313192

Mephedrone does not damage dopamine nerve endings of the striatum, but enhances the neurotoxicity of methamphetamine, amphetamine, and MDMA.

PubMed

Angoa-Pérez, Mariana; Kane, Michael J; Briggs, Denise I; Francescutti, Dina M; Sykes, Catherine E; Shah, Mrudang M; Thomas, David M; Kuhn, Donald M

2013-04-01

Mephedrone (4-methylmethcathinone) is a β-ketoamphetamine stimulant drug of abuse with close structural and mechanistic similarities to methamphetamine. One of the most powerful actions associated with mephedrone is the ability to stimulate dopamine (DA) release and block its re-uptake through its interaction with the dopamine transporter (DAT). Although mephedrone does not cause toxicity to DA nerve endings, its ability to serve as a DAT blocker could provide protection against methamphetamine-induced neurotoxicity like other DAT inhibitors. To test this possibility, mice were treated with mephedrone (10, 20, or 40 mg/kg) prior to each injection of a neurotoxic regimen of methamphetamine (four injections of 2.5 or 5.0 mg/kg at 2 h intervals). The integrity of DA nerve endings of the striatum was assessed through measures of DA, DAT, and tyrosine hydroxylase levels. The moderate to severe DA toxicity associated with the different doses of methamphetamine was not prevented by any dose of mephedrone but was, in fact, significantly enhanced. The hyperthermia caused by combined treatment with mephedrone and methamphetamine was the same as seen after either drug alone. Mephedrone also enhanced the neurotoxic effects of amphetamine and 3,4-methylenedioxymethamphetamine on DA nerve endings. In contrast, nomifensine protected against methamphetamine-induced neurotoxicity. As mephedrone increases methamphetamine neurotoxicity, the present results suggest that it interacts with the DAT in a manner unlike that of other typical DAT inhibitors. The relatively innocuous effects of mephedrone alone on DA nerve endings mask a potentially dangerous interaction with drugs that are often co-abused with it, leading to heightened neurotoxicity. © 2012 International Society for Neurochemistry.

The Role of Endogenous Serotonin in Methamphetamine-Induced Neurotoxicity to Dopamine Nerve Endings of the Striatum

PubMed Central

Thomas, David M.; Angoa-Pérez, Mariana; Francescutti-Verbeem, Dina M.; Shah, Mrudang M.; Kuhn, Donald M.

2010-01-01

Methamphetamine (METH) is a neurotoxic drug of abuse that damages the dopamine (DA) neuronal system in a highly delimited manner. The brain structure most affected by METH is the striatum where long-term DA depletion and microglial activation are maximal. Endogenous DA has been implicated as a critical participant in METH-induced neurotoxicity, most likely as a substrate for non-enzymatic oxidation by METH-generated reactive oxygen species (ROS). The striatum is also extensively innervated by serotonin (5HT) nerve endings and this neurochemical system is modified by METH in much the same manner as seen in DA nerve endings (i.e., increased release of 5HT, loss of function in tryptophan hydroxylase and the serotonin transporter, long-term depletion of 5HT stores). 5HT can also be modified by ROS to form highly reactive species that damage neurons but its role in METH neurotoxicity has not been assessed. Increases in 5HT levels with 5HTP do not change METH-induced neurotoxicity to the DA nerve endings as revealed by reductions in DA, tyrosine hydroxylase and dopamine transporter levels. Partial reductions in 5HT with p-chlorophenylalanine (PCPA) are without effect on METH toxicity, despite the fact that PCPA largely prevents METH-induced hyperthermia. Mice lacking the gene for brain tryptophan hydroxylase 2 are devoid of brain 5HT and respond to METH in the same manner as wild-type controls, despite showing enhanced drug-induced hyperthermia. Taken together, the present results indicate that endogenous 5HT does not appear to play a role in METH-induced damage to DA nerve endings of the striatum. PMID:20722968

The role of endogenous serotonin in methamphetamine-induced neurotoxicity to dopamine nerve endings of the striatum.

PubMed

Thomas, David M; Angoa Pérez, Mariana; Francescutti-Verbeem, Dina M; Shah, Mrudang M; Kuhn, Donald M

2010-11-01

Methamphetamine (METH) is a neurotoxic drug of abuse that damages the dopamine (DA) neuronal system in a highly delimited manner. The brain structure most affected by METH is the striatum where long-term DA depletion and microglial activation are maximal. Endogenous DA has been implicated as a critical participant in METH-induced neurotoxicity, most likely as a substrate for non-enzymatic oxidation by METH-generated reactive oxygen species. The striatum is also extensively innervated by serotonin (5HT) nerve endings and this neurochemical system is modified by METH in much the same manner as seen in DA nerve endings (i.e., increased release of 5HT, loss of function in tryptophan hydroxylase and the serotonin transporter, long-term depletion of 5HT stores). 5HT can also be modified by reactive oxygen species to form highly reactive species that damage neurons but its role in METH neurotoxicity has not been assessed. Increases in 5HT levels with 5-hydroxytryptophan do not change METH-induced neurotoxicity to the DA nerve endings as revealed by reductions in DA, tyrosine hydroxylase and dopamine transporter levels. Partial reductions in 5HT with p-chlorophenylalanine are without effect on METH toxicity, despite the fact that p-chlorophenylalanine largely prevents METH-induced hyperthermia. Mice lacking the gene for brain tryptophan hydroxylase 2 are devoid of brain 5HT and respond to METH in the same manner as wild-type controls, despite showing enhanced drug-induced hyperthermia. Taken together, the present results indicate that endogenous 5HT does not appear to play a role in METH-induced damage to DA nerve endings of the striatum. © 2010 The Authors. Journal Compilation © 2010 International Society for Neurochemistry.

Adaptations of Presynaptic Dopamine Terminals Induced by Psychostimulant Self-Administration

PubMed Central

2015-01-01

A great deal of research has focused on investigating neurobiological alterations induced by chronic psychostimulant use in an effort to describe, understand, and treat the pathology of psychostimulant addiction. It has been known for several decades that dopamine neurotransmission in the nucleus accumbens is integrally involved in the selection and execution of motivated and goal-directed behaviors, and that psychostimulants act on this system to exert many of their effects. As such, a large body of work has focused on defining the consequences of psychostimulant use on dopamine signaling in the striatum as it relates to addictive behaviors. Here, we review presynaptic dopamine terminal alterations observed following self-administration of cocaine and amphetamine, as well as possible mechanisms by which these alterations occur and their impact on the progression of addiction. PMID:25491345

Dopamine Mediates the Vagal Modulation of the Immune System by Electroacupuncture

PubMed Central

Torres-Rosas, Rafael; Yehia, Ghassan; Peña, Geber; Mishra, Priya; del Rocio Thompson-Bonilla, Maria; Moreno-Eutimio, Mario Adán; Arriaga-Pizano, Lourdes Andrea; Isibasi, Armando; Ulloa, Luis

2014-01-01

Previous anti-inflammatory strategies against sepsis, a leading cause of death in hospitals, had limited efficacy in clinical trials, in part because they targeted single cytokines and the experimental models failed to mimic clinical settings1-3. Neuronal networks represent physiological mechanisms selected by evolution to control inflammation that can be exploited for the treatment of inflammatory and infectious disorders3. Here, we report that sciatic nerve activation with electroacupuncture controls systemic inflammation and rescues mice from polymicrobial peritonitis. Electroacupuncture at the sciatic nerve controls systemic inflammation by inducing a vagal activation of DOPA decarboxylase leading to the production of dopamine in the adrenal medulla. Experimental models with adrenolectomized animals mimic clinical adrenal insufficiency4, increase the susceptibility to sepsis, and prevent the anti-inflammatory potential of electroacupuncture. Dopamine inhibits cytokine production via dopaminergic type-1 receptors. Dopaminergic D1-agonists suppress systemic inflammation and rescue mice from polymicrobial peritonitis in animals with adrenal insufficiency. Our results suggest a novel anti-inflammatory mechanism mediated by the sciatic and the vagus nerves modulating the production of catecholamines in the adrenal glands. From a pharmacological perspective, selective dopaminergic agonists mimic the anti-inflammatory potential of electroacupuncture and can provide therapeutic advantages to control inflammation in infectious and inflammatory disorders. PMID:24562381

Presynaptic excitability.

PubMed

Jackson, M B

1995-01-01

Based on functional characterizations with electrophysiological techniques, the channels in nerve terminals appear to be as diverse as channels in nerve cell bodies (Table I). While most presynaptic Ca2+ channels superficially resemble either N-type or L-type channels, variations in detail have necessitated the use of subscripts and other notations to indicate a nerve terminal-specific subtype (e.g., Wang et al., 1993). Variations such as these pose a serious obstacle to the identification of presynaptic channels based solely on the effects of channel blockers on synaptic transmission. Pharmacological sensitivity alone is not likely to help in determining functional properties. Crucial details, such as voltage sensitivity and inactivation, require direct examination. It goes without saying that every nerve terminal membrane contains Ca2+ channels as an entry pathway so that Ca2+ can trigger secretion. However, there appears to be no general specification of channel type, other than the exclusion of T-type Ca2+ channels. T-type Ca2+ channels are defined functionally by strong inactivation and low threshold. Some presynaptic Ca2+ channels inactivate (posterior pituitary and Xenopus nerve terminals), and others have a somewhat reduced voltage threshold (retinal bipolar neurons and squid giant synapse). Perhaps it is just a matter of time before a nerve terminal Ca2+ channel is found with both of these properties. The high threshold and strong inactivation of T-type Ca2+ channels are thought to be adaptations for oscillations and the regulation of bursting activity in nerve cell bodies. The nerve terminals thus far examined have no endogenous electrical activity, but rather are driven by the cell body. On functional grounds, it is then reasonable to anticipate finding T-type Ca2+ channels in nerve terminals that can generate electrical activity on their own. The rarity of such behavior in nerve terminals may be associated with the rarity of presynaptic T-type Ca2+ channels. In four of the five preparations reviewed in this chapter--motor nerve, squid giant synapse, ciliary ganglion, and retina bipolar neurons--evidence was presented that supports a location for Ca2+ channels that is very close to active zones of secretion. All of these synapses secrete from clear vesicles, and the speed and specificity of transduction provided by proximity may be a common feature of these rapid synapses. In contrast, the posterior pituitary secretion apparatus may be triggered by higher-affinity Ca2+ receptors and lower concentrations of Ca2+ (Lindau et al., 1992). This would correspond with the slower performance of peptidergic secretion, but because of the large stimuli needed to evoke release from neurosecretosomes, the possibility remains that the threshold for secretion is higher than that reported. While the role of Ca2+ as a trigger of secretion dictates a requirement for voltage-activated Ca2+ channels as universal components of the presynaptic membrane, the presence of other channels is more difficult to predict. Depolarizations caused by voltage-activated Na+ channels activate the presynaptic Ca2+ channels, but whether this depolarization requires Na+ channels in the presynaptic membrane itself may depend on the electrotonic length of the nerve terminal. Variations in density between motor nerve terminals may reflect species differences in geometry. The high Na+ channel density in the posterior pituitary reflects the great electrotonic length of this terminal arbor. Whether Na+ channels are abundant or not in a presynaptic membrane, K+ channels provide the most robust mechanism for limiting depolarization-induced Ca2+ entry. K+ channel blockers enhance transmission at most synapses. In general, K+ channels are abundant in nerve terminals, although their apparent lower priority compared to Ca2+ channels in the eyes of many investigators leaves us with fewer detailed investigations in some preparations. Most nerve terminals have more than

Modifications of Gustatory Nerve Synapses onto Nucleus of the Solitary Tract Neurons Induced by Dietary Sodium-Restriction During Development

PubMed Central

MAY, OLIVIA L.; ERISIR, ALEV; HILL, DAVID L.

2008-01-01

The terminal fields of nerves carrying gustatory information to the rat brainstem show a remarkable amount of expansion in the nucleus of the solitary tract (NTS) as a result of early dietary sodium restriction. However, the extent to which these axonal changes represent corresponding changes in synapses is not known. To identify the synaptic characteristics that accompany the terminal field expansion, the greater superficial petrosal (GSP), chorda tympani (CT), and glossopharyngeal (IX) nerves were labeled in rats fed a sodium-restricted diet during pre- and postnatal development. The morphology of these nerve terminals within the NTS region where the terminal fields of all three nerves overlap was evaluated by transmission electron microscopy. Compared to data from control rats, CT axons were the most profoundly affected. The density of CT arbors and synapses quadrupled as a result of the near life-long dietary manipulation. In contrast, axon and synapse densities of GSP and IX nerves were not modified in sodium-restricted rats. Furthermore, compared to controls, CT terminals displayed more instances of contacts with postsynaptic dendritic protrusions and IX terminals synapsed more frequently with dendritic shafts. Thus, dietary sodium restriction throughout pre- and postnatal development had differential effects on the synaptic organization of the three nerves in the NTS. These anatomical changes may underlie the impact of sensory restriction during development on the functional processing of taste information and taste-related behaviors. PMID:18366062

Modifications of gustatory nerve synapses onto nucleus of the solitary tract neurons induced by dietary sodium-restriction during development.

PubMed

May, Olivia L; Erisir, Alev; Hill, David L

2008-06-01

The terminal fields of nerves carrying gustatory information to the rat brainstem show a remarkable amount of expansion in the nucleus of the solitary tract (NTS) as a result of early dietary sodium restriction. However, the extent to which these axonal changes represent corresponding changes in synapses is not known. To identify the synaptic characteristics that accompany the terminal field expansion, the greater superficial petrosal (GSP), chorda tympani (CT), and glossopharyngeal (IX) nerves were labeled in rats fed a sodium-restricted diet during pre- and postnatal development. The morphology of these nerve terminals within the NTS region where the terminal fields of all three nerves overlap was evaluated by transmission electron microscopy. Compared to data from control rats, CT axons were the most profoundly affected. The density of CT arbors and synapses quadrupled as a result of the near life-long dietary manipulation. In contrast, axon and synapse densities of GSP and IX nerves were not modified in sodium-restricted rats. Furthermore, compared to controls, CT terminals displayed more instances of contacts with postsynaptic dendritic protrusions and IX terminals synapsed more frequently with dendritic shafts. Thus, dietary sodium restriction throughout pre- and postnatal development had differential effects on the synaptic organization of the three nerves in the NTS. These anatomical changes may underlie the impact of sensory restriction during development on the functional processing of taste information and taste-related behaviors.

Regulation of tyrosine hydroxylase activity and phosphorylation at Ser(19) and Ser(40) via activation of glutamate NMDA receptors in rat striatum.

PubMed

Lindgren, N; Xu, Z Q; Lindskog, M; Herrera-Marschitz, M; Goiny, M; Haycock, J; Goldstein, M; Hökfelt, T; Fisone, G

2000-06-01

The activity of tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of dopamine, is stimulated by phosphorylation. In this study, we examined the effects of activation of NMDA receptors on the state of phosphorylation and activity of tyrosine hydroxylase in rat striatal slices. NMDA produced a time-and concentration-dependent increase in the levels of phospho-Ser(19)-tyrosine hydroxylase in nigrostriatal nerve terminals. This increase was not associated with any changes in the basal activity of tyrosine hydroxylase, measured as DOPA accumulation. Forskolin, an activator of adenylyl cyclase, stimulated tyrosine hydroxylase phosphorylation at Ser(40) and caused a significant increase in DOPA accumulation. NMDA reduced forskolin-mediated increases in both Ser(40) phosphorylation and DOPA accumulation. In addition, NMDA reduced the increase in phospho-Ser(40)-tyrosine hydroxylase produced by okadaic acid, an inhibitor of protein phosphatase 1 and 2A, but not by a cyclic AMP analogue, 8-bromo-cyclic AMP. These results indicate that, in the striatum, glutamate decreases tyrosine hydroxylase phosphorylation at Ser(40) via activation of NMDA receptors by reducing cyclic AMP production. They also provide a mechanism for the demonstrated ability of NMDA to decrease tyrosine hydroxylase activity and dopamine synthesis.

Quantitative determination of 3,4-methylenedioxymethamphetamine by thin-layer chromatography in ecstasy illicit pills in Tehran.

PubMed

Shetab Boushehri, Seyed Vahid; Tamimi, Maryam; Kebriaeezadeh, Abbas

2009-11-01

3,4-Methylenedioxymethamphetamine (MDMA) is the major ingredient of ecstasy illicit pills. It is a hallucinogen, central nervous system stimulant, and serotonergic neurotoxin that strongly releases serotonin from serotonergic nerves terminals. Moreover, it releases norepinephrine and dopamine from nerves terminal, but to a lesser extent than serotonin. Poisoning and even death from abusing MDMA-containing ecstasy illicit pills among abusers is usual. Thus, quantitative determination of MDMA content of ecstasy illicit pills in illicit drug bazaar must be done regularly to find the most high dose ecstasy illicit pills and removing them from illicit drug bazaar. In the present study, MDMA contents of 13 most abundant ecstasy illicit pills were determined by quantitative thin-layer chromatography (TLC). Two procedures for quantitative determination of MDMA contents of ecstasy illicit pills by TLC were used: densitometric and so-called 'scraping off' methods. The former was done in a reflection mode at 285 nm and the latter was done by absorbance measurement of eluted scraped off spots. Limit of detection (LOD), considering signal-to-noise ratio (S/N) of 2, and limit of quantification (LOQ), regarding S/N of 10, of densitometric and scraping off methods were 0.40 microg, 1.20 microg, and 6.87 mug, 20.63 microg, respectively. Repeatabilities (within-laboratory error) of densitometric and scraping off methods were 0.5% and 3.6%, respectively. The results showed that the ecstasy illicit pills contained 24-124.5 mg and 23.9-122.2 mg MDMA by densitometric and scraping off methods, respectively.

A cephalic projection neuron involved in locomotion is dye coupled to the dopaminergic neural network in the medicinal leech.

PubMed

Crisp, Kevin M; Mesce, Karen A

2004-12-01

It is widely appreciated that the selection and modulation of locomotor circuits are dependent on the actions of higher-order projection neurons. In the leech, Hirudo medicinalis, locomotion is modulated by a number of cephalic projection neurons that descend from the subesophageal ganglion in the head. Specifically, descending brain interneuron Tr2 functions as a command-like neuron that can terminate or sometimes trigger fictive swimming. In this study, we demonstrate that Tr2 is dye coupled to the dopaminergic neural network distributed in the head brain. These findings represent the first anatomical evidence in support of dopamine (DA) playing a role in the modulation of locomotion in the leech. In addition, we have determined that bath application of DA to the brain and entire nerve cord reliably and rapidly terminates swimming in all preparations exhibiting fictive swimming. By contrast, DA application to nerve cords expressing ongoing fictive crawling does not inhibit this motor rhythm. Furthermore, we show that Tr2 receives rhythmic feedback from the crawl central pattern generator. For example, Tr2 receives inhibitory post-synaptic potentials during the elongation phase of each crawl cycle. When crawling is not expressed, spontaneous inhibitory post-synaptic potentials in Tr2 correlate in time with spontaneous excitatory post-synaptic potentials in the CV motor neuron, a circular muscle excitor that bursts during the elongation phase of crawling. Our data are consistent with the idea that DA biases the nervous system to produce locomotion in the form of crawling.

Catecholaminergic connectivity to the inner ear, central auditory and vocal motor circuitry in the plainfin midshipman fish, Porichthys notatus

PubMed Central

Forlano, Paul M.; Kim, Spencer D.; Krzyminska, Zuzanna M.; Sisneros, Joseph A.

2014-01-01

Although the neuroanatomical distribution of catecholaminergic (CA) neurons has been well documented across all vertebrate classes, few studies have examined CA connectivity to physiologically and anatomically identified neural circuitry that controls behavior. The goal of this study was to characterize CA distribution in the brain and inner ear of the plainfin midshipman fish (Porichthys notatus) with particular emphasis on their relationship with anatomically labeled circuitry that both produces and encodes social acoustic signals in this species. Neurobiotin labeling of the main auditory endorgan, the saccule, combined with tyrosine hydroxylase immunofluorescence (TH-ir) revealed a strong CA innervation of both the peripheral and central auditory system. Diencephalic TH-ir neurons in the periventricular posterior tuberculum, known to be dopaminergic, send ascending projections to the ventral telencephalon and prominent descending projections to vocal-acoustic integration sites, notably the hindbrain octavolateralis efferent nucleus, as well as onto the base of hair cells in the saccule via nerve VIII. Neurobiotin backfills of the vocal nerve in combination with TH-ir revealed CA terminals on all components of the vocal pattern generator which appears to largely originate from local TH-ir neurons but may include diencephalic projections as well. This study provides strong evidence for catecholamines as important neuromodulators of both auditory and vocal circuitry and acoustic-driven social behavior in midshipman fish. This first demonstration of TH-ir terminals in the main endorgan of hearing in a non-mammalian vertebrate suggests a conserved and important anatomical and functional role for dopamine in normal audition. PMID:24715479

[Changes in the innervation of the taste buds in diabetic rats].

PubMed

Hevér, Helén; Altdorfer, Károly; Zelles, Tivadar; Batbayar, Bayarchimeg; Fehér, Erzsébet

2013-03-24

Abnormal sensations such as pain and impairment of taste are symptoms of approximately 10% of patients having diabetes mellitus. The aim of the study was to investigate and quantify the different neuropeptide containing nerve fibres in the vallate papilla of the diabetic rat. Immunohistochemical methods were used to study the changes of the number of different neuropeptide containing nerve terminals located in the vallate papillae in diabetic rats. Diabetes was induced in the rats with streptozotocin. Two weeks after streptozotocin treatment the number of the substance P, galanin, vasoactive intestinal polypeptide and neuropeptide Y immunoreactive nerve terminals was significantly increased (p<0.05) in the tunica mucosa of the tongue. The number of the lymphocytes and mast cells was also increased significantly. Some of the immunoreactive nerve terminals were located in the lingual epithelium both intragemmally and extragemmally and were seen to comprise dense bundles in the lamina propria just beneath the epithelium. No taste cells were immunoreactive for any of the investigated peptides. Vasoactive intestinal polypeptide and neuropeptide Y immunoreactive nerve fibres were not detected in the taste buds. For weeks after streptozotocin administration the number of the substance P, calcitonin gene related peptide and galanin immunoreactive nerve terminals was decreased both intragemmally and intergemmally. In case of immediate insulin treatment, the number of the immunoreactive nerve terminals was similar to that of the controls, however, insulin treatment given 1 week later to diabetic rats produced a decreased number of nerve fibers. Morphometry revealed no significant difference in papilla size between the control and diabetic groups, but there were fewer taste buds (per papilla). Increased number of immunoreactive nerve terminals and mast cells 2 weeks after the development of diabetes was the consequence of neurogenic inflammation which might cause vasoconstriction and lesions of the oral mucosa. Taste impairment, which developed 4 weeks after streptozotocin treatment could be caused by neuropathic defects and degeneration or morphological changes in the taste buds and nerve fibres.

Effects of combined treatment with mephedrone and methamphetamine or 3,4-methylenedioxymethamphetamine on serotonin nerve endings of the hippocampus

PubMed Central

Angoa-Pérez, Mariana; Kane, Michael J.; Herrera-Mundo, Nieves; Francescutti, Dina M.; Kuhn, Donald M.

2013-01-01

Aims Mephedrone is a stimulant drug of abuse with close structural and mechanistic similarities to methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA). Although mephedrone does not damage dopamine nerve endings it increases the neurotoxicity of amphetamine, methamphetamine and MDMA. The effects of mephedrone on serotonin (5HT) nerve endings are not fully understood, with some investigators reporting damage while others conclude it does not. Presently, we investigate if mephedrone given alone or with methamphetamine or MDMA damages 5HT nerve endings of the hippocampus. Main methods The status of 5HT nerve endings in hippocampus of female C57BL mice was assessed through measures of 5HT by HPLC and by immunoblot analysis of serotonin transporter (SERT) and tryptophan hydroxylase 2 (TPH2), selective markers of 5HT nerve endings. Astrocytosis was assessed through measures of glial fibrillary acidic protein (GFAP) (immunoblotting) and microglial activation was determined by histochemical staining with Isolectin B4. Key findings Mephedrone alone did not cause persistent reductions in the levels of 5HT, SERT or TPH2. Methamphetamine and MDMA alone caused mild reductions in 5HT but did not change SERT and TPH2 levels. Combined treatment with mephedrone and methamphetamine or MDMA did not change the status of 5HT nerve endings to an extent that was different from either drug alone. Significance Mephedrone does not cause toxicity to 5HT nerve endings of the hippocampus. When co-administered with methamphetamine or MDMA, drugs that are often co-abused with mephedrone by humans, toxicity is not increased as is the case for dopamine nerve endings when these drugs are taken together. PMID:23892197

3,4-Methylenedioxypyrovalerone prevents while methylone enhances methamphetamine-induced damage to dopamine nerve endings: β-ketoamphetamine modulation of neurotoxicity by the dopamine transporter

PubMed Central

Anneken, John H.; Angoa-Pérez, Mariana; Kuhn, Donald M.

2016-01-01

Methylone, 3,4-methylenedioxypyrovalerone (MDPV), and mephedrone are psychoactive ingredients of ‘bath salts’ and their abuse represents a growing public health care concern. These drugs are cathinone derivatives and are classified chemically as β-ketoamphetamines. Because of their close structural similarity to the amphetamines, methylone, MDPV, and mephedrone share most of their pharmacological, neurochemical, and behavioral properties. One point of divergence in their actions is the ability to cause damage to the CNS. Unlike methamphetamine, the β-ketoamphetamines do not damage dopamine (DA) nerve endings. However, mephedrone has been shown to significantly accentuate methamphetamine neurotoxicity. Bath salt formulations contain numerous different psychoactive ingredients, and individuals who abuse bath salts also coabuse other illicit drugs. Therefore, we have evaluated the effects of methylone, MDPV, mephedrone, and methamphetamine on DA nerve endings. The β-ketoamphetamines alone or in all possible two-drug combinations do not result in damage to DA nerve endings but do cause hyperthermia. MDPV completely protects against the neurotoxic effects of methamphetamine while methylone accentuates it. Neither MDPV nor methylone attenuates the hyperthermic effects of methamphetamine. The potent neuroprotective effects of MDPV extend to amphetamine-, 3,4-methylenedioxymethamphetamine-, and MPTP-induced neurotoxicity. These results indicate that β-ketoamphetamine drugs that are non-substrate blockers of the DA transporter (i.e., MDPV) protect against methamphetamine neurotoxicity, whereas those that are substrates for uptake by the DA transporter and which cause DA release (i.e., methylone, mephedrone) accentuate neurotoxicity. PMID:25626880

Elevated expression of glutathione peroxidase in PC12 cells results in protection against methamphetamine but not MPTP toxicity.

PubMed

Hom, D G; Jiang, D; Hong, E J; Mo, J Q; Andersen, J K

1997-06-01

In vivo administration of either 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or methamphetamine (MA) produces damage to the dopaminergic nervous system which may be due in part to the generation of reactive oxygen species (ROS). The resistance of superoxide dismutase (SOD) over-expressing transgenic mice to the effects of both MPTP and MA suggests the involvement of superoxide in the resulting neurotoxicity of both compounds. Superoxide can be converted by SOD to hydrogen peroxide, which itself can cause cellular degeneration by reacting with free iron to produce highly reactive hydroxyl radicals resulting in damage to proteins, nucleic acids and membrane phospholipids. Hydrogen peroxide has also been reported to be produced via inhibition of NADH dehydrogenase by MPP + formed during oxidation of MPTP by MAO-B and by dopamine auto-oxidation following MA-induced dopamine release from synaptic vesicles within nerve terminals. To test whether hydrogen peroxide is an important factor in the toxicity of either of these two neurotoxins, we created clonal PC12 lines expressing elevated levels of the hydrogen peroxide-reducing enzyme glutathione peroxidase (GSHPx). Elevation of GSHPx levels in PC12 was found to diminish the rise in ROS levels and lipid peroxidation resulting from MA but not MPTP treatment. Elevated levels of GSHPx also appeared to prevent decreases in transport-mediated dopamine uptake produced via MA administration as well as to attenuate toxin-induced cell loss as measured by either MTT reduction or LDH release. Our data, therefore, suggest that hydrogen peroxide production likely contributes to MA toxicity in dopaminergic neurons.

High-Fat-Diet-Induced Deficits in Dopamine Terminal Function Are Reversed by Restoring Insulin Signaling.

PubMed

Fordahl, Steve C; Jones, Sara R

2017-02-15

Systemically released insulin crosses the blood-brain barrier and binds to insulin receptors on several neural cell types, including dopaminergic neurons. Insulin has been shown to decrease dopamine neuron firing in the ventral tegmental area (VTA), but potentiate release and reuptake at dopamine terminals in the nucleus accumbens (NAc). Here we show that prolonged consumption of a high fat diet blocks insulin's effects in the NAc, but insulin's effects are restored by inhibiting protein tyrosine phosphatase 1B, which supports insulin receptor signaling. Mice fed a high fat diet (60% kcals from fat) displayed significantly higher fasting blood glucose 160 mg/dL, compared to 101 mg/dL for control-diet-fed mice, and high-fat-diet-fed mice showed reduced blood glucose clearance after an intraperitoneal glucose tolerance test. Using fast scan cyclic voltammetry to measure electrically evoked dopamine in brain slices containing the NAc core, high-fat-diet-fed mice exhibited slower dopamine reuptake compared to control-diet-fed mice (2.2 ± 0.1 and 2.67 ± 0.15 μM/s, respectively). Moreover, glucose clearance rate was negatively correlated with V max . Insulin (10 nM to 1 μM) dose dependently increased reuptake rates in control-diet-fed mice compared with in the high-fat-diet group; however, the small molecule insulin receptor sensitizing agent, TCS 401 (300 nM), restored reuptake in high-fat-diet-fed mice to control-diet levels, and a small molecule inhibitor of the insulin receptor, BMS 536924 (300 nM), attenuated reuptake, similar to high-fat-diet-fed mice. These data show that a high-fat diet impairs dopamine reuptake by attenuating insulin signaling at dopamine terminals.

Epothilone D Prevents Binge Methamphetamine-Mediated Loss of Striatal Dopaminergic Markers

PubMed Central

Killinger, Bryan A.; Moszczynska, Anna

2016-01-01

Exposure to binge methamphetamine (METH) can result in a permanent or transient loss of dopaminergic (DAergic) markers such as dopamine (DA), dopamine transporter (DAT), and tyrosine hydroxylase (TH) in the striatum. We hypothesized that the METH-induced loss of striatal DAergic markers was, in part, due to destabilization of microtubules (MTs) in the nigrostriatal DA pathway that ultimately impedes anterograde axonal transport of these markers. To test this hypothesis, adult male Sprague Dawley rats were treated with binge METH or saline in the presence or absence of epothilone D (EpoD), a MT-stabilizing compound, and assessed for the levels of several DAergic markers as well as for the levels of tubulins and their posttranslational modifications (PMTs) at 3 days after the treatments. Binge METH induced a loss of stable long-lived MTs within the striatum but not within the SNpc. Treatment with a low dose of EpoD increased the levels of markers of stable MTs and prevented METH-mediated deficits in several DAergic markers in the striatum. By contrast, administration of a high dose of EpoD appeared to destabilize MTs and potentiated the METH-induced deficits in several DAergic markers. The low-dose EpoD also prevented the METH-induced increase in striatal DA turnover and increased behavioral stereotypy during METH treatment. Together, these results demonstrate that MT dynamics plays a role in the development of METH-induced losses of several DAergic markers in the striatum and may mediate METH-induced degeneration of terminals in the nigrostriatal DA pathway. Our study also demonstrates that MT-stabilizing drugs, such as EpoD have a potential to serve as useful therapeutic agents to restore function of DAergic nerve terminals following METH exposure when administered at low doses. PMID:26465779

The terminal latency of the phrenic nerve correlates with respiratory symptoms in amyotrophic lateral sclerosis.

PubMed

Park, Jin-Sung; Park, Donghwi

2017-09-01

The aim of the study was to investigate the electrophysiological parameters in phrenic nerve conduction studies (NCS) that sensitively reflect latent respiratory insufficiency present in amyotrophic lateral sclerosis (ALS). Forty-nine patients with ALS were examined, and after exclusion, 21 patients with ALS and their phrenic NCS results were reviewed. The patients were divided into two groups according to their respiratory sub-score in the ALS functional rating scale - revised (Group A, sub-score 12vs. Group B, sub-score 11). We compared the parameters of phrenic NCS between the two groups. There were no significant differences in the clinical characteristics between the two groups. Using a multivariate model, we found that the terminal latency of the phrenic nerve was the only parameter that was associated with early symptoms of respiratory insufficiency (p<0.05). The optimal cutoff value for the terminal latency of the phrenic nerve was 7.65ms (sensitivity 80%, specificity 68.2%). The significantly prolonged terminal latency of the phrenic nerve in our study may reflect a profound distal motor axonal dysfunction of the phrenic nerve in patients with ALS in the early stage of respiratory insufficiency that can be used as a sensitive electrophysiological marker reflecting respiratory symptoms in ALS. The terminal latency of the phrenic nerve is useful for early detection of respiratory insufficiency in patients with ALS. Copyright © 2017. Published by Elsevier B.V.

Running wheel exercise before a binge regimen of methamphetamine does not protect against striatal dopaminergic damage.

PubMed

O'dell, Steven J; Marshall, John F

2014-09-01

Repeated administration of methamphetamine (mAMPH) to rodents in a single-day "binge" dosing regimen produces long-lasting damage to forebrain dopaminergic nerve terminals as measured by decreases in tissue dopamine (DA) content and levels of the plasmalemmal DA transporter (DAT). However, the midbrain cell bodies from which the DA terminals arise survive, and previous reports show that striatal DA markers return to control levels by 12 months post-mAMPH, suggesting long-term repair or regrowth of damaged DA terminals. We previously showed that when rats engaged in voluntary aerobic exercise for 3 weeks before and 3 weeks after a binge regimen of mAMPH, exercise significantly ameliorated mAMPH-induced decreases in striatal DAT. However, these data left unresolved the question of whether exercise protected against the initial neurotoxicity from the mAMPH binge or accelerated the repair of the damaged DA terminals. The present experiments were designed to test whether exercise protects against the mAMPH-induced injury. Adult male Sprague-Dawley rats were allowed to run in wheels for 3 weeks before an acute binge regimen of mAMPH or saline, then placed into nonwheel cages for an additional week before autoradiographic determination of striatal DAT binding. The autoradiographic findings showed that prior exercise provided no protection against mAMPH-induced damage to striatal DA terminals. These results, together with analyses from our previous experiments, suggest that voluntary exercise may accelerate the repair of mAMPH-damaged DA terminals and that voluntary exercise may be useful as therapeutic adjunct in the treatment mAMPH addicts. © 2014 Wiley Periodicals, Inc.

Presynaptic control of transmission along the pathway mediating disynaptic reciprocal inhibition in the cat

PubMed Central

Enríquez-Denton, M; Nielsen, J; Perreault, M-C; Morita, H; Petersen, N; Hultborn, H

2000-01-01

In cat lumbar motoneurones, disynaptic inhibitory postsynaptic potentials (IPSPs) evoked by stimulation of antagonist motor nerves were depressed for at least 150 ms following conditioning stimulation of flexor (1.7-2 times threshold (T)) and ankle extensor (5T) nerves. The aim of the present study was to investigate the possibility that this depression is caused by presynaptic inhibitory mechanisms acting at the terminals of group I afferent fibres projecting to the Ia inhibitory interneurones and/or the terminals of these interneurones to the target motoneurones. Conditioning stimulation of flexor, but not ankle extensor, nerves evoked a depression of the monosynaptic Ia excitatory postsynaptic potentials (EPSPs) recorded intracellularly in Ia inhibitory interneurones. This depression lasted between 200 and 700 ms and was not accompanied by a depression of the monosynaptic EPSPs evoked by stimulation of descending pathways. These results suggest that flexor, but not ankle extensor, group I afferent fibres can modulate sensory transmission at the synapse between Ia afferent fibres and Ia inhibitory interneurones. Conditioning stimulation of flexor muscle nerves, extensor muscle nerves and cutaneous nerves produced a long-lasting increase in excitability of the terminals of the Ia inhibitory interneurones. The increase in the excitability of the terminals was not secondary to an electrotonic spread of synaptic excitation at the soma. Indeed, concomitant with the excitability increase of the terminals there were signs of synaptic inhibition in the soma. The unitary IPSPs induced in target motoneurones following the spike activity of single Ia inhibitory interneurones were depressed by conditioning stimulation of muscle and cutaneous nerves. Since the conditioning stimulation also evoked compound IPSPs in those motoneurones, a firm conclusion as to whether unitary IPSP depression involved presynaptic inhibitory mechanism of the terminals of the interneurones could not be reached. The possibility that the changes in excitability of the Ia interneuronal terminals reflect the presence of a presynaptic inhibitory mechanism similar to that operating at the terminals of the afferent fibres (presynaptic inhibition) is discussed.1. In cat lumbar motoneurones, disynaptic inhibitory postsynaptic potentials (IPSPs) evoked by stimulation of antagonist motor nerves were depressed for at least 150 ms following conditioning stimulation of flexor (1.7-2 times threshold (T)) and ankle extensor (5T) nerves. The aim of the present study was to investigate the possibility that this depression is caused by presynaptic inhibitory mechanisms acting at the terminals of group I afferent fibres projecting to the Ia inhibitory interneurones and/or the terminals of these interneurones to the target motoneurones. PMID:10922013

Ultrastructural and molecular biologic comparison of classic proprioceptors and palisade endings in sheep extraocular muscles.

PubMed

Rungaldier, Stefanie; Heiligenbrunner, Stefan; Mayer, Regina; Hanefl-Krivanek, Christiane; Lipowec, Marietta; Streicher, Johannes; Blumer, Roland

2009-12-01

To analyze and compare the structural and molecular features of classic proprioceptors like muscle spindles and Golgi tendon organs (GTOs) and putative proprioceptors (palisade endings) in sheep extraocular muscle (EOMs). The EOMs of four sheep were analyzed. Frozen sections or wholemount preparations of the samples were immunohistochemically labeled and analyzed by confocal laser scanning microscopy. Triple labeling with different combinations of antibodies against neurofilament, synaptophysin, and choline acetyltransferase (ChAT), as well as alpha-bungarotoxin and phalloidin, was performed. Microscopic anatomy of the nerve end organs was analyzed by transmission electron microscopy. The microscopic anatomy demonstrated that muscle spindles and GTOs had a perineural capsule and palisade endings a connective tissue capsule. Sensory nerve terminals in muscle spindles and GTOs contained only a few vesicles, whereas palisade nerve terminals were full of clear vesicles. Likewise, motor terminals in the muscle spindles' polar regions were full of clear vesicles. Immunohistochemistry showed that sensory nerve fibers as well as their sensory nerve terminals in muscle spindles and GTOs were ChAT-negative. Palisade endings were supplied by ChAT-positive nerve fibers, and the palisade complexes including palisade nerve terminals were also ChAT-immunoreactive. Motor terminals in muscle spindles were ChAT and alpha-bungarotoxin positive. The present study demonstrated in sheep EOMs that palisade endings are innervated by cholinergic axons exhibiting characteristics typical of motoneurons, whereas muscle spindles (except the polar regions) and GTOs are supplied by noncholinergic axons. These results raise the question of whether palisade endings are candidates for proprioceptors in EOMs.

Ultrastructural and molecular biologic comparison of classical proprioceptors and palisade endings in sheep extraocular muscles

PubMed Central

RUNGALDIER, Stefanie; HEILIGENBRUNNER, Stefan; MAYER, Regina; HANEFL-KRIVANEK, Christiane; LIPOWEC, Marietta; STREICHER, Johannes; BLUMER, Roland

2016-01-01

Purpose To analyze and compare the structural and molecular features of classical proprioceptors like muscle spindles and Golgi tendon organs (GTOs) and putative proprioceptors (palisade endings) in sheep extraocular muscle (EOMs). Methods The EOMs of four sheep were analyzed. Frozen sections or whole mount preparations of the samples were immunohistochemically labeled and analyzed by confocal laser scanning microscopy. Triple labeling with different combinations of antibodies against neurofilament, synaptophysin and choline acetyltransferase (ChAT) as well as α-bungarotoxin and phalloidin was performed. Microscopic anatomy of the nerve end organs was analyzed by transmission electron microscopy. Results The microscopic anatomy demonstrated that muscle spindles and GTOs had a perineural capsule and palisade endings a connective tissue capsule. Sensory nerve terminals in muscle spindles and GTOs contained only few vesicles whereas palisade nerve terminals were full of clear vesicles. Likewise, motor terminals in the muscle spindles’ polar regions were full of clear vesicles. Immunohistochemistry showed that sensory nerve fibers as well as their sensory nerve terminals in muscle spindles and GTOs were ChAT-negative. Palisade endings were supplied by ChAT-positive nerve fibers and the palisade complexes including palisade nerve terminals were also ChAT-immunoreactive. Motor terminals in muscle spindles were ChAT and α-bungarotoxin -positive. Conclusions The present study demonstrated in sheep EOMs that palisade endings are innervated by cholinergic axons exhibiting characteristics typical for motoneurons whereas muscle spindles (except the polar regions) and GTOs are supplied by non-cholinergic axons. These results question whether palisade endings are candidates for proprioceptors in EOMs. PMID:19553627

Current research on methamphetamine-induced neurotoxicity: animal models of monoamine disruption.

PubMed

Kita, Taizo; Wagner, George C; Nakashima, Toshikatsu

2003-07-01

Methamphetamine (METH)-induced neurotoxicity is characterized by a long-lasting depletion of striatal dopamine (DA) and serotonin as well as damage to striatal dopaminergic and serotonergic nerve terminals. Several hypotheses regarding the mechanism underlying METH-induced neurotoxicity have been proposed. In particular, it is thought that endogenous DA in the striatum may play an important role in mediating METH-induced neuronal damage. This hypothesis is based on the observation of free radical formation and oxidative stress produced by auto-oxidation of DA consequent to its displacement from synaptic vesicles to cytoplasm. In addition, METH-induced neurotoxicity may be linked to the glutamate and nitric oxide systems within the striatum. Moreover, using knockout mice lacking the DA transporter, the vesicular monoamine transporter 2, c-fos, or nitric oxide synthetase, it was determined that these factors may be connected in some way to METH-induced neurotoxicity. Finally a role for apoptosis in METH-induced neurotoxicity has also been established including evidence of protection of bcl-2, expression of p53 protein, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), activity of caspase-3. The neuronal damage induced by METH may reflect neurological disorders such as autism and Parkinson's disease.

Expanded Terminal Fields of Gustatory Nerves Accompany Embryonic BDNF Overexpression in Mouse Oral Epithelia

PubMed Central

Sun, Chengsan; Dayal, Arjun

2015-01-01

Brain-derived neurotrophic factor (BDNF) is expressed in gustatory epithelia and is required for gustatory neurons to locate and innervate their correct target during development. When BDNF is overexpressed throughout the lingual epithelium, beginning embryonically, chorda tympani fibers are misdirected and innervate inappropriate targets, leading to a loss of taste buds. The remaining taste buds are hyperinnervated, demonstrating a disruption of nerve/target matching in the tongue. We tested the hypothesis here that overexpression of BDNF peripherally leads to a disrupted terminal field organization of nerves that carry taste information to the brainstem. The chorda tympani, greater superficial petrosal, and glossopharyngeal nerves were labeled in adult wild-type (WT) mice and in adult mice in which BDNF was overexpressed (OE) to examine the volume and density of their central projections in the nucleus of the solitary tract. We found that the terminal fields of the chorda tympani and greater superficial petrosal nerves and overlapping fields that included these nerves in OE mice were at least 80% greater than the respective field volumes in WT mice. The shapes of terminal fields were similar between the two groups; however, the density and spread of labels were greater in OE mice. Unexpectedly, there were also group-related differences in chorda tympani nerve function, with OE mice showing a greater relative taste response to a concentration series of sucrose. Overall, our results show that disruption in peripheral innervation patterns of sensory neurons have significant effects on peripheral nerve function and central organization of their terminal fields. PMID:25568132

The Role of D2-Autoreceptors in Regulating Dopamine Neuron Activity and Transmission

PubMed Central

Ford, Christopher P

2014-01-01

Dopamine D2-autoreceptors play a key role in regulating the activity of dopamine neurons and control the synthesis, release and uptake of dopamine. These Gi/o-coupled inhibitory receptors play a major part in shaping dopamine transmission. Found at both somatodendritic and axonal sites, autoreceptors regulate the firing patterns of dopamine neurons and control the timing and amount of dopamine released from their terminals in target regions. Alterations in the expression and activity of autoreceptors are thought to contribute to Parkinson’s disease as well as schizophrenia, drug addiction and attention deficit hyperactivity disorder (ADHD), which emphasizes the importance of D2-autoreceptors in regulating the dopamine system. This review will summarize the cellular actions of dopamine autoreceptors and discuss recent advances that have furthered our understanding of the mechanisms by which D2-receptors control dopamine transmission. PMID:24463000

Cholinergic Interneurons Underlie Spontaneous Dopamine Release in Nucleus Accumbens

PubMed Central

2017-01-01

The release of dopamine from terminals in the NAc is regulated by a number of factors, including voltage-gated ion channels, D2-autoreceptors, and nAChRs. Cholinergic interneurons (CINs) drive dopamine release through activation of nAChRs on dopamine terminals. Using cyclic voltammetry in mouse brain slices, nAChR-dependent spontaneous dopamine transients and the mechanisms underlying the origin were examined in the NAc. Spontaneous events were infrequent (0.3 per minute), but the rate and amplitude were increased after blocking Kv channels with 4-aminopyridine. Although the firing frequency of CINs was increased by blocking glutamate reuptake with TBOA and the Sk blocker apamin, only 4-aminopyridine increased the frequency of dopamine transients. In contrast, inhibition of CIN firing with the μ/δ selective opioid [Met5]enkephalin (1 μm) decreased spontaneous dopamine transients. Cocaine increased the rate and amplitude of dopamine transients, suggesting that the activity of the dopamine transporter limits the detection of these events. In the presence of cocaine, the rate of spontaneous dopamine transients was further increased after blocking D2-autoreceptors. Blockade of muscarinic receptors had no effect on evoked dopamine release, suggesting that feedback inhibition of acetylcholine release was not involved. Thus, although spontaneous dopamine transients are reliant on nAChRs, the frequency was not strictly governed by the activity of CINs. The increase in frequency of spontaneous dopamine transients induced by cocaine was not due to an increase in cholinergic tone and is likely a product of an increase in detection resulting from decreased dopamine reuptake. SIGNIFICANCE STATEMENT The actions of dopamine in the NAc are thought to be responsible for endogenous reward and the reinforcing properties of drugs of abuse, such as psychostimulants. The present work examines the mechanisms underlying nAChR-induced spontaneous dopamine release. This study demonstrates that spontaneous dopamine release is (1) dependent of the activation of nicotinic receptors, (2) independent on the spontaneous activity of cholinergic interneurons, and (3) that cocaine increased the detection of dopamine transients by prolonging the presence and increasing the diffusion of dopamine in the extracellular space. The release of acetylcholine is therefore responsible for spontaneous dopamine transients, and cocaine augments dopamine tone without altering activity of cholinergic interneurons. PMID:28115487

Modeling neuropeptide transport in various types of nerve terminals containing en passant boutons.

PubMed

Kuznetsov, I A; Kuznetsov, A V

2015-03-01

We developed a mathematical model for simulating neuropeptide transport inside dense core vesicles (DCVs) in axon terminals containing en passant boutons. The motivation for this research is a recent experimental study by Levitan and colleagues (Bulgari et al., 2014) which described DCV transport in nerve terminals of type Ib and type III as well as in nerve terminals of type Ib with the transcription factor DIMM. The goal of our modeling is validating the proposition put forward by Levitan and colleagues that the dramatic difference in DCV number in type Ib and type III terminals can be explained by the difference in DCV capture in type Ib and type III boutons rather than by differences in DCV anterograde transport and half-life of resident DCVs. The developed model provides a tool for studying the dynamics of DCV transport in various types of nerve terminals. The model is also an important step in gaining a better mechanistic understanding of transport processes in axons and identifying directions for the development of new models in this area. Copyright © 2014 Elsevier Inc. All rights reserved.

The serotonergic system in Parkinson's patients with dyskinesia: evidence from imaging studies.

PubMed

Pagano, Gennaro; Niccolini, Flavia; Politis, Marios

2017-12-20

The purpose of review is to review the current status of positron emission tomography (PET) molecular imaging of serotonergic system in Parkinson's patients who experience levodopa-induced (LIDs) and graft-induced dyskinesias (GIDs). PET imaging studies have shown that Parkinson's disease is characterized by progressive loss of dopaminergic and serotonergic neurons. Parkinson's patients who experienced LIDs and GIDs have an aberrant spreading of serotonergic terminals, which lead to an increased serotonergic/dopaminergic terminals ratio within the putamen. Serotonergic terminals convert exogenous levodopa into dopamine in a non-physiological manner and release an abnormal amount of dopamine without an auto-regulatory feedback. This results in higher swings in synaptic levels of dopamine, which leads to the development of LIDs and GIDs. The modulation of serotonergic terminals with 5-HT 1A and 5-HT 1B receptors agonists partially reduced these motor complications. In vivo PET studies confirmed that abnormal spreading of serotonergic terminals within the putamen has a pivotal role in the development of LIDs and GIDs. However, glutamatergic, adenosinergic, opioid systems, and phosphodiesterases 10A may also play a role in the development of these motor complications. An integrative multimodal imaging approach combining PET and MRI imaging techniques is needed to fully understand the mechanisms underlying the development of LIDs and GIDs.

Desmin and nerve terminal expression during embryonic development of the lateral pterygoid muscle in mice.

PubMed

Yamamoto, Masahito; Shinomiya, Takashi; Kishi, Asuka; Yamane, Shigeki; Umezawa, Takashi; Ide, Yoshinobu; Abe, Shinichi

2014-09-01

In adults, the lateral pterygoid muscle (LPM) is usually divided into the upper and lower head, between which the buccal nerve passes. Recent investigations have demonstrated foetal developmental changes in the topographical relationship between the human LPM and buccal nerve. However, as few studies have investigated this issue, we clarified the expression of desmin and nerve terminal distribution during embryonic development of the LPM in mice. We utilized immunohistochemical staining and reverse transcription chain reaction (RT-PCR) to clarify the expression of desmin and nerve terminal distribution. We observed weak expression of desmin in the LPM at embryonic day (ED) 11, followed by an increase in expression from embryonic days 12-15. In addition, starting at ED 12, we observed preferential accumulation of desmin in the vicinity of the myotendinous junction, a trend that did not change up to ED 15. Nerve terminal first appeared at ED 13 and formed regularly spaced linear arrays at the centre of the muscle fibre by ED 15. The results of immunohistochemical staining agreed with those of RT-PCR analysis. We found that desmin accumulated in the vicinity of the myotendinous junction starting at ED 12, prior to the onset of jaw movement. We speculate that the accumulation of desmin is due to factors other than mechanical stress experienced during early muscle contraction. Meanwhile, the time point at which nerve terminals first appeared roughly coincided with the onset of jaw movement. Copyright © 2014 Elsevier Ltd. All rights reserved.

Multiple functions of neuronal plasma membrane neurotransmitter transporters.

PubMed

Raiteri, Luca; Raiteri, Maurizio

2015-11-01

Removal from receptors of neurotransmitters just released into synapses is one of the major steps in neurotransmission. Transporters situated on the plasma membrane of nerve endings and glial cells perform the process of neurotransmitter (re)uptake. Because the density of transporters in the membranes can fluctuate, transporters can determine the transmitter concentrations at receptors, thus modulating indirectly the excitability of neighboring neurons. Evidence is accumulating that neurotransmitter transporters can exhibit multiple functions. Being bidirectional, neurotransmitter transporters can mediate transmitter release by working in reverse, most often under pathological conditions that cause ionic gradient dysregulations. Some transporters reverse to release transmitters, like dopamine or serotonin, when activated by 'indirectly acting' substrates, like the amphetamines. Some transporters exhibit as one major function the ability to capture transmitters into nerve terminals that perform insufficient synthesis. Transporter activation can generate conductances that regulate directly neuronal excitability. Synaptic and non-synaptic transporters play different roles. Cytosolic Na(+) elevations accompanying transport can interact with plasmalemmal or/and mitochondrial Na(+)/Ca(2+) exchangers thus generating calcium signals. Finally, neurotransmitter transporters can behave as receptors mediating releasing stimuli able to cause transmitter efflux through multiple mechanisms. Neurotransmitter transporters are therefore likely to play hitherto unknown roles in multiple therapeutic treatments. Copyright © 2015 Elsevier Ltd. All rights reserved.

Protective actions of the vesicular monoamine transporter 2 (VMAT2) in monoaminergic neurons.

PubMed

Guillot, Thomas S; Miller, Gary W

2009-04-01

Vesicular monoamine transporters (VMATs) are responsible for the packaging of neurotransmitters such as dopamine, serotonin, norepinephrine, and epinephrine into synaptic vesicles. These proteins evolved from precursors in the major facilitator superfamily of transporters and are among the members of the toxin extruding antiporter family. While the primary function of VMATs is to sequester neurotransmitters within vesicles, they can also translocate toxicants away from cytosolic sites of action. In the case of dopamine, this dual role of VMAT2 is combined-dopamine is more readily oxidized in the cytosol where it can cause oxidative stress so packaging into vesicles serves two purposes: neurotransmission and neuroprotection. Furthermore, the deleterious effects of exogenous toxicants on dopamine neurons, such as MPTP, can be attenuated by VMAT2 activity. The active metabolite of MPTP can be kept within vesicles and prevented from disrupting mitochondrial function thereby sparing the dopamine neuron. The highly addictive drug methamphetamine is also neurotoxic to dopamine neurons by using dopamine itself to destroy the axon terminals. Methamphetamine interferes with vesicular sequestration and increases the production of dopamine, escalating the amount in the cytosol and leading to oxidative damage of terminal components. Vesicular transport seems to resist this process by sequestering much of the excess dopamine, which is illustrated by the enhanced methamphetamine neurotoxicity in VMAT2-deficient mice. It is increasingly evident that VMAT2 provides neuroprotection from both endogenous and exogenous toxicants and that while VMAT2 has been adapted by eukaryotes for synaptic transmission, it is derived from phylogenetically ancient proteins that originally evolved for the purpose of cellular protection.

Selectivity of the uptake of glutamate and GABA in two morphologically distinct insect neuromuscular synapses.

PubMed

van Marle, J; Piek, T; Lammertse, T; Lind, A; Van Weeren-Kramer, J

1985-11-25

The common inhibitor (CI) and slow excitor tibiae (SETi) innervated slow muscles 135cd of the locust Schistocerca gregaria were incubated under high-affinity uptake conditions either in [3H]GABA or in [3H]glutamate. [3H]GABA is accumulated in the glia of the nerve endings of the CI as well as the SETi; however, it is accumulated only in the terminal axons of the CI, not in the terminal axons of the SETi. The grain densities above the glia and above the CI terminal axons are approximately 2 grains/micron2. After incubation in [3H]glutamate the grain densities above the CI terminal axons and the SETi terminal axons are approximately 4 grains/micron2; the grain densities above the glia of both types of nerve endings are approximately 17 grains/micron2. The relatively high labeling (3 grains/micron2) of the muscles after incubation in the presence of glutamate is ascribed to the high metabolic requirements of slow muscles. The conclusion is drawn that a high-affinity uptake system for GABA is present in the CI terminal axons and in the glia of both the CI and SETi nerve endings. However, while the glutamate uptake in the CI and SETi nerve endings of the slow 135cd is comparable to the high-affinity uptake of glutamate in the fast excitor tibiae (FETi) nerve endings of the fast retractor unguis muscle, a high-affinity uptake of glutamate was only demonstrated in the glia of both types of nerve endings. A high-affinity uptake in the terminal axons of the CI and SETi may be masked by an extensively low-affinity uptake of glutamate by the muscles.

Facile synthesis of terminal-alkyne bioorthogonal molecules for live -cell surface-enhanced Raman scattering imaging through Au-core and silver/dopamine-shell nanotags.

PubMed

Chen, Meng; Zhang, Ling; Yang, Bo; Gao, Mingxia; Zhang, Xiangmin

2018-03-01

Alkyne is unique, specific and biocompatible in the Raman-silent region of the cell, but there still remains a challenge to achieve ultrasensitive detection in living systems due to its weak Raman scattering. Herein, a terminal alkyne ((E)-2-[4-(ethynylbenzylidene)amino]ethane-1-thiol (EBAE)) with surface-enhanced Raman scattering is synthesized. The EBAE molecule possesses S- and C-termini, which can be directly bonded to gold nanoparticles and dopamine/silver by forming the Au-S chemical bond and the carbon-metal bond, respectively. The distance between Raman reporter and AuNPs/AgNPs can be reduced, contributing to forming hot-spot-based SERS substrate. The alkyne functionalized nanoparticles are based on Au core and encapsulating polydopamine shell, defined as Au-core and dopamine/Ag-shell (ACDS). The bimetallic ACDS induce strong SERS signals for molecular imaging that arise from the strong electromagnetic field. Furthermore, the EBAE provides a distinct peak in the cellular Raman-silent region with nearly zero background interference. The EBAE Raman signals could be tremendously enhanced when the Raman reporter is located at the middle of the Au-core and dopamine/Ag-shell. Therefore, this work could have huge potential benefits for the highly sensitive detection of intercellular information delivery by connecting the recognition molecules in biomedical diagnostics. Graphical abstract Terminal-alkyne-functionalized Au-core and silver/dopamine-shell nanotags for live-cell surface-enhanced Raman scattering imaging.

Vesicular Monoamine Transporter 2 (VMAT2) Level Regulates MPTP Vulnerability and Clearance of Excess Dopamine in Mouse Striatal Terminals.

PubMed

Lohr, Kelly M; Chen, Merry; Hoffman, Carlie A; McDaniel, Miranda J; Stout, Kristen A; Dunn, Amy R; Wang, Minzheng; Bernstein, Alison I; Miller, Gary W

2016-09-01

The vesicular monoamine transporter 2 (VMAT2) packages neurotransmitters for release during neurotransmission and sequesters toxicants into vesicles to prevent neuronal damage. In mice, low VMAT2 levels causes catecholaminergic cell loss and behaviors resembling Parkinson's disease, while high levels of VMAT2 increase dopamine release and protect against dopaminergic toxicants. However, comparisons across these VMAT2 mouse genotypes were impossible due to the differing genetic background strains of the animals. Following back-crossing to a C57BL/6 line, we confirmed that mice with approximately 95% lower VMAT2 levels compared with wild-type (VMAT2-LO) display significantly reduced vesicular uptake, progressive dopaminergic terminal loss with aging, and exacerbated 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity. Conversely, VMAT2-overexpressing mice (VMAT2-HI) are protected from the loss of striatal terminals following MPTP treatment. We also provide evidence that enhanced vesicular filling in the VMAT2-HI mice modifies the handling of newly synthesized dopamine, indicated by changes in indirect measures of extracellular dopamine clearance. These results confirm the role of VMAT2 in the protection of vulnerable nigrostriatal dopamine neurons and may also provide new insight into the side effects of L-DOPA treatments in Parkinson's disease. © The Author 2016. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Serotonin and serotoninergic neurons. A radioautographic and immunocytochemical study of the nucleus raphe dorsalis and nucleus dorsomedialis hypothalami.

PubMed

Arezki, F; Afailal, I; Bosler, O; Steinbusch, H W; Calas, A

1987-01-01

In an attempt to define cytophysiological criteria with which to establish whether or not a given neuron is serotoninergic, radioautography was combined with serotonin (5-HT) immunocytochemistry on the same sections from the nucleus raphe dorsalis (NRD) and/or nucleus dorsomedialis hypothalami (NDM) in rats subjected to intraventricular administrations of (3H)-5-HT or (3H)-dopamine (DA). All the (3H)-5-HT-accumulating neurons (cell bodies, dendrites and terminals) were found to be distinct from the (3H)-DA labeled ones and invariably immunostained for 5-HT in both regions studied. However, some immunoreactive neuronal elements within the area of tracer diffusion did not exhibit significant radioautographic labeling. In the NDM where 5-HT immunoreactive nerve cells could be detected only after intraventricular administration of 5-HT, these were found to be definitely distinct from the tyrosine hydroxylase immunoreactive and (3H)-DA labeled neurons of the dopaminergic periventricular-arcuate complex. After immunostaining for GAD at the electron microscopic level, (3H)-5-HT labeled nerve cells and terminals were not found to exhibit any significant immunoreactivity. Associations between (3H)-DA labeled and GAD immunoreactive processes with 5-HT immunoreactive or (3H)-5-HT-accumulating neurons, respectively, could also be observed in the NDM. When considered as a whole along with previous observations by other authors indicating a probable synthesis of 5-HT within NDM neurons, our data suggest that a given neuron can be classified as serotoninergic on the sole basis of its ability to selectively take up exogenous 5-HT under experimental conditions compatible with non interspecific labeling of catecholaminergic neurons. They also provide valuable information on the neurochemical environment and possible control of central serotoninergic neurons.

[Morphologic studies of the protective role of catechin on kanamycin otoneurotoxicity in SD rats].

PubMed

Liu, Guo-hui; Xie, Ding-hua; Wu, Wei-jing

2002-12-28

To determine the protection of catechin on aminoglycoside antibiotics otoneurotoxicity in SD rats, and observe the morphologic changes of cochlear efferent nerve terminals and outer hair cells after the injection of kanamycin and the feeding of catechin by the stomach tube. Thirty-eight SD rats were randomly assigned into three experimental groups (KM-treated, catechin-treated, KM and catechin in combination) and one control group. The KM-treated group was given kanamycin in a dose of 500 mg.(kg.d)-1 for 14 days. The catechin-treated group was given catechin once by the stomach tube in a dose of 400 mg.(kg.d)-1. Two kinds of medicine were simultaneously given in the KM+ catechin group. Transmission electron microscopy was utilized to observe the subcellular structure of efferent nerve fibers and outer hair cells. The densities of efferent nerve fibers and terminals were examined and the numbers of efferent nerve fibers and terminals were numerated by the surface preparation using modified histochemical staining for acetylcholinesterase (AchE). The damage in the group protected by catechin was relieved compared with the unprotected group. No damage was found in the catechin-treated alone group and controls. The densities and numbers of efferent nerve fibers and terminals were obviously fewer in the unprotected group than in the protected group and controls(P < 0.05). There was no significant difference in the numbers of efferent nerve fibers and terminals of the group protected by catechin compared with the controls and the catechin-treated group (P > 0.05). Catechin significantly protects MOC efferent nerves in kanamycin otoneurotoxicity.

Selective effects of buspirone and molindone on dopamine metabolism and function in the striatum and frontal cortex of the rat.

PubMed

McMillen, B A; McDonald, C C

1983-03-01

The hypothesis that the nerve endings of the dopamine projection of the frontal cortex lack autoreceptors for regulation of tyrosine hydroxylase was tested by using the preferential inhibitors of dopamine autoreceptors, molindole and buspirone. In contrast to haloperidol, which elevates dopamine metabolism in the striatum and frontal cortex, both molindone and buspirone elicited little change in dopamine metabolism in the frontal cortex at doses up to 3.0 mg/kg, which cause the same maximal response in the corpus striatum as does haloperidol. Thus, the lack of autoreceptors in the frontal cortex is of pharmacological importance. That preferential inhibition of striatal dopamine autoreceptors may reverse catalepsy by enhancing synthesis and release of dopamine was tested by first inducing catalepsy with different drugs and then administering molindone or buspirone. Only buspirone (1.0 mg/kg) reversed catalepsy. This effect does not require presynaptic dopamine as catalepsy was reversed by buspirone in the dopamine-depleted rat (with 2.0 mg/kg R04-1284) as well as after postsynaptic dopamine receptor blockade by haloperidol of cis-flupenthixol. Thus, the mechanism for the reversal of catalepsy appears to be located efferent from the dopamine neuron. Buspirone, a non-benzodiazepine anti-anxiety drug, may prove useful for treatment of extrapyramidal motor disorders of either iatrogenic or idiosyncratic origin.

The dimensions and characteristics of the subepidermal nerve plexus in human skin--terminal Schwann cells constitute a substantial cell population within the superficial dermis.

PubMed

Reinisch, Christina M; Tschachler, Erwin

2012-03-01

The skin constitutes the largest sensorial organ. Its nervous system consists of different types of afferent nerve fibers which spread out immediately beneath the skin surface to sense temperature, touch and pain. Our aim was to investigate the dimension and topographic relationship of the different nerve fibers of the subepidermal nerve plexus in human hairy skin and to analyze numbers and marker expression of terminal Schwann cells. Nerve fibers and Schwann cells were investigated on dermal sheet preparations and thick sections of skin from various body regions of 10 individuals. The dimension of subepidermal nerve fibers varied between different body sites with highest values in chest skin (100 ± 18 mm/mm(2)) and lowest in posterior forearm skin (53 ± 10 mm/mm(2)). The majority of fibers (85.79%) were unmyelinated, thus representing C-fibers, of which 7.84% were peptidergic. Neurofilament-positive fibers (A-fibers) accounted for 14.21% and fibers positive for both neurofilament and myelin (Aβ-fibers) for only 0.18%. The number of Schwann cells varied in accordance with nerve fiber length from 453 ± 108 on chest skin to 184 ± 58/mm(2) in skin of the posterior forearm. Terminal Schwann cells showed a marker profile comparable to Schwann cells in peripheral nerves with the notable exception of expression of NGFr, NCAM, L1CAM and CD146 on myelinating Schwann cells in the dermis but not in peripheral nerves. Our data show that terminal Schwann cells constitute a substantial cell population within the papillary dermis and that both nerve fiber length and Schwann cell numbers vary considerably between different body sites. Copyright © 2011 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.

Carbachol induces burst firing of dopamine cells in the ventral tegmental area by promoting calcium entry through L-type channels in the rat

PubMed Central

Zhang, Lei; Liu, Yudan; Chen, Xihua

2005-01-01

Enhanced activity of the central dopamine system has been implicated in many psychiatric disorders including schizophrenia and addiction. Besides terminal mechanisms that boost dopamine levels at the synapse, the cell body of dopamine cells enhances terminal dopamine concentration through encoding action potentials in bursts. This paper presents evidence that burst firing of dopamine cells in the ventral tegmental area was under cholinergic control using nystatin-perforated patch clamp recording from slice preparations. The non-selective cholinergic agonist carbachol excited the majority of recorded neurones, an action that was not affected by blocking glutamate and GABA ionotropic receptors. Twenty per cent of dopamine cells responded to carbachol with robust bursting, an effect mediated by both muscarinic and nicotinic cholinoceptors postsynaptically. Burst firing induced as such was completely dependent on calcium entry as it could be blocked by cadmium and more specifically the L-type blocker nifedipine. In the presence of the sodium channel blocker tetrodotoxin, carbachol induced membrane potential oscillation that had similar kinetics and frequency as burst firing cycles and could also be blocked by cadmium and nifedipine. Direct activation of the L-type channel with Bay K8644 induced strong bursting which could be blocked by nifedipine but not by depleting internal calcium stores. These results indicate that carbachol increases calcium entry into the postsynaptic cell through L-type channels to generate calcium-dependent membrane potential oscillation and burst firing. This could establish the L-type channel as a target for modulating the function of the central dopamine system in disease conditions. PMID:16081481

High-Bandwidth Atomic Force Microscopy Reveals A Mechanical spike Accompanying the Action Potential in mammalian Nerve Terminals

NASA Astrophysics Data System (ADS)

Salzberg, Brian M.

2008-03-01

Information transfer from neuron to neuron within nervous systems occurs when the action potential arrives at a nerve terminal and initiates the release of a chemical messenger (neurotransmitter). In the mammalian neurohypophysis (posterior pituitary), large and rapid changes in light scattering accompany secretion of transmitter-like neuropeptides. In the mouse, these intrinsic optical signals are intimately related to the arrival of the action potential (E-wave) and the release of arginine vasopressin and oxytocin (S-wave). We have used a high bandwidth (20 kHz) atomic force microscope (AFM) to demonstrate that these light scattering signals are associated with changes in nerve terminal volume, detected as nanometer-scale movements of a cantilever positioned on top of the neurohypophysis. The most rapid mechanical response, the ``spike'', has duration comparable to that of the action potential (˜2 ms) and probably reflects an increase in terminal volume due to H2O movement associated with Na^+-influx. Elementary calculations suggest that two H2O molecules accompanying each Na^+-ion could account for the ˜0.5-1.0 å increase in the diameter of each terminal during the action potential. Distinguishable from the mechanical ``spike'', a slower mechanical event, the ``dip'', represents a decrease in nerve terminal volume, depends upon Ca^2+-entry, as well as on intra-terminal Ca^2+-transients, and appears to monitor events associated with secretion. A simple hypothesis is that this ``dip'' reflects the extrusion of the dense core granule that comprises the secretory products. These dynamic high bandwidth AFM recordings are the first to monitor mechanical events in nervous systems and may provide novel insights into the mechanism(s) by which excitation is coupled to secretion at nerve terminals.

Palisade endings in extraocular muscles of the monkey are immunoreactive for choline acetyltransferase and vesicular acetylcholine transporter.

PubMed

Konakci, Kadriye Zeynep; Streicher, Johannes; Hoetzenecker, Wolfram; Haberl, Ines; Blumer, Michael Josef Franz; Wieczorek, Grazyna; Meingassner, Josef Gottfried; Paal, Szabolcs Levente; Holzinger, Daniel; Lukas, Julius-Robert; Blumer, Roland

2005-12-01

To analyze palisade endings in extraocular muscles (EOMs) of a primate species and to examine our previous findings in cat that palisade endings are putative effector organs. Eleven monkeys (Macaca fascicularis) of both sexes, between 4 and 6 years of age were analyzed. Whole EOM myotendons were immunostained with four combinations of triple-fluorescent labeling and examined by confocal laser scanning microscopy. Labeling included antibodies against choline acetyltransferase (ChAT), vesicular acetylcholine transporter (VAChT), neurofilament, and synaptophysin. Muscle fibers were counterstained with phalloidin. Palisade endings were observed in all monkey EOMs. Nerve fibers extended from the muscle into the tendon and looped back to divide into a terminal arborization (palisade ending) around a single muscle fiber tip. In approximately 30% of the cases, nerve fibers supplying palisade endings often established motor terminals outside the palisade complex. Nerve fibers forming palisade endings were ChAT-neurofilament positive. Axonal branches of palisade endings were ChAT-neurofilament positive as well. All palisade nerve terminals exhibited ChAT-synaptophysin immunoreactivity. Within the palisade complex, palisade nerve terminals exhibited VAChT immunoreactivity. All palisade nerve terminals were VAChT-synaptophysin immunoreactive. The results confirm that in the monkey, palisade endings contain acetylcholine and are therefore most likely effector organs. Palisade endings are also present in human EOMs and because of their location at the myotendinous junction, these organs are of crucial interest for strabismus surgery.

Molecular Machines Determining the Fate of Endocytosed Synaptic Vesicles in Nerve Terminals

PubMed Central

Fassio, Anna; Fadda, Manuela; Benfenati, Fabio

2016-01-01

The cycle of a synaptic vesicle (SV) within the nerve terminal is a step-by-step journey with the final goal of ensuring the proper synaptic strength under changing environmental conditions. The SV cycle is a precisely regulated membrane traffic event in cells and, because of this, a plethora of membrane-bound and cytosolic proteins are devoted to assist SVs in each step of the journey. The cycling fate of endocytosed SVs determines both the availability for subsequent rounds of release and the lifetime of SVs in the terminal and is therefore crucial for synaptic function and plasticity. Molecular players that determine the destiny of SVs in nerve terminals after a round of exo-endocytosis are largely unknown. Here we review the functional role in SV fate of phosphorylation/dephosphorylation of SV proteins and of small GTPases acting on membrane trafficking at the synapse, as they are emerging as key molecules in determining the recycling route of SVs within the nerve terminal. In particular, we focus on: (i) the cyclin-dependent kinase-5 (cdk5) and calcineurin (CN) control of the recycling pool of SVs; (ii) the role of small GTPases of the Rab and ADP-ribosylation factor (Arf) families in defining the route followed by SV in their nerve terminal cycle. These regulatory proteins together with their synaptic regulators and effectors, are molecular nanomachines mediating homeostatic responses in synaptic plasticity and potential targets of drugs modulating the efficiency of synaptic transmission. PMID:27242505

Molecular Machines Determining the Fate of Endocytosed Synaptic Vesicles in Nerve Terminals.

PubMed

Fassio, Anna; Fadda, Manuela; Benfenati, Fabio

2016-01-01

The cycle of a synaptic vesicle (SV) within the nerve terminal is a step-by-step journey with the final goal of ensuring the proper synaptic strength under changing environmental conditions. The SV cycle is a precisely regulated membrane traffic event in cells and, because of this, a plethora of membrane-bound and cytosolic proteins are devoted to assist SVs in each step of the journey. The cycling fate of endocytosed SVs determines both the availability for subsequent rounds of release and the lifetime of SVs in the terminal and is therefore crucial for synaptic function and plasticity. Molecular players that determine the destiny of SVs in nerve terminals after a round of exo-endocytosis are largely unknown. Here we review the functional role in SV fate of phosphorylation/dephosphorylation of SV proteins and of small GTPases acting on membrane trafficking at the synapse, as they are emerging as key molecules in determining the recycling route of SVs within the nerve terminal. In particular, we focus on: (i) the cyclin-dependent kinase-5 (cdk5) and calcineurin (CN) control of the recycling pool of SVs; (ii) the role of small GTPases of the Rab and ADP-ribosylation factor (Arf) families in defining the route followed by SV in their nerve terminal cycle. These regulatory proteins together with their synaptic regulators and effectors, are molecular nanomachines mediating homeostatic responses in synaptic plasticity and potential targets of drugs modulating the efficiency of synaptic transmission.

Selective binding, uptake, and retrograde transport of tetanus toxin by nerve terminals in the rat iris. An electron microscope study using colloidal gold as a tracer

PubMed Central

1978-01-01

A series of specific macromolecules (tetanus toxin, cholera toxin, nerve growth factor [NGF], and several lectins) have been shown to be transported retrogradely with high selectivity from terminals to cell bodies in various types of neurons. Under identical experimental conditions (low protein concentrations injected), most other macromolecules, e.g. horseradish peroxidase (HRP), albumin, ferritin, are not transported in detectable amounts. In the present EM study, we demonstrate selective binding of tetanus toxin to the surface membrane of nerve terminals, followed by uptake and subsequent retorgrade axonal transport. Tetanus toxin or albumin was adsorbed to colloidal gold particles (diam 200 A). The complex was shown to be stable and well suited as an EM tracer. 1-4 h after injection into the anterior eye chamber of adult rats, tetanus toxin-gold particles were found to be selectively associated with membranes of nerve terminals and preterminal axons. Inside terminals and axons, the tracer was localized mainly in smooth endoplasmic reticulum (SER)-like membrane compartments. In contrast, association of albumin-gold complexes with nervous structures was never observed, in spite of extensive uptake into fibroblasts. Electron microscope and biochemical experiments showed selective retrograde transport of tetanus toxin-gold complexes to the superior cervical ganglion. Specific binding to membrane components at nerve terminals and subsequent internalization and retrograde transport may represent an important pathway for macromolecules carrying information from target organs to the perikarya of their innervating neurons. PMID:659508

Redistribution of Cav2.1 channels and calcium ions in nerve terminals following end-to-side neurorrhaphy: ionic imaging analysis by TOF-SIMS.

PubMed

Liu, Chiung-Hui; Chang, Hung-Ming; Tseng, To-Jung; Lan, Chyn-Tair; Chen, Li-You; Youn, Su-Chung; Lee, Jian-Jr; Mai, Fu-Der; Chou, Jui-Feng; Liao, Wen-Chieh

2016-11-01

The P/Q-type voltage-dependent calcium channel (Cav2.1) in the presynaptic membranes of motor nerve terminals plays an important role in regulating Ca 2+ transport, resulting in transmitter release within the nervous system. The recovery of Ca 2+ -dependent signal transduction on motor end plates (MEPs) and innervated muscle may directly reflect nerve regeneration following peripheral nerve injury. Although the functional significance of calcium channels and the levels of Ca 2+ signalling in nerve regeneration are well documented, little is known about calcium channel expression and its relation with the dynamic Ca 2+ ion distribution at regenerating MEPs. In the present study, end-to-side neurorrhaphy (ESN) was performed as an in vivo model of peripheral nerve injury. The distribution of Ca 2+ at regenerating MEPs following ESN was first detected by time-of-flight secondary ion mass spectrometry, and the specific localization and expression of Cav2.1 channels were examined by confocal microscopy and western blotting. Compared with other fundamental ions, such as Na + and K + , dramatic changes in the Ca 2+ distribution were detected along with the progression of MEP regeneration. The re-establishment of Ca 2+ distribution and intensity were correlated with the functional recovery of muscle in ESN rats. Furthermore, the re-clustering of Cav2.1 channels after ESN at the nerve terminals corresponded with changes in the Ca 2+ distribution. These results indicated that renewal of the Cav2.1 distribution within the presynaptic nerve terminals may be necessary for initiating a proper Ca 2+ influx and shortening the latency of muscle contraction during nerve regeneration.

Phasic dopamine release drives rapid activation of striatal D2-receptors

PubMed Central

Marcott, Pamela F; Mamaligas, Aphroditi A; Ford, Christopher P

2014-01-01

Summary Striatal dopamine transmission underlies numerous goal-directed behaviors. Medium spiny neurons (MSNs) are a major target of dopamine in the striatum. However, as dopamine does not directly evoke a synaptic event in MSNs, the time course of dopamine signaling in these cells remains unclear. To examine how dopamine release activates D2-receptors on MSNs, G-protein activated inwardly rectifying potassium (GIRK2; Kir 3.2) channels were virally overexpressed in the striatum and the resulting outward currents were used as a sensor of D2-receptor activation. Electrical and optogenetic stimulation of dopamine terminals evoked robust D2-receptor inhibitory post-synaptic currents (IPSCs) in GIRK2-expressing MSNs that occurred in under a second. Evoked D2-IPSCs could be driven by repetitive stimulation and were not occluded by background dopamine tone. Together, the results indicate that D2-receptors on MSNs exhibit functional low affinity and suggest that striatal D2-receptors can encode both tonic and phasic dopamine signals. PMID:25242218

Coincident postsynaptic activity gates presynaptic dopamine release to induce plasticity in Drosophila mushroom bodies

PubMed Central

Ueno, Kohei; Suzuki, Ema; Naganos, Shintaro; Ofusa, Kyoko; Horiuchi, Junjiro; Saitoe, Minoru

2017-01-01

Simultaneous stimulation of the antennal lobes (ALs) and the ascending fibers of the ventral nerve cord (AFV), two sensory inputs to the mushroom bodies (MBs), induces long-term enhancement (LTE) of subsequent AL-evoked MB responses. LTE induction requires activation of at least three signaling pathways to the MBs, mediated by nicotinic acetylcholine receptors (nAChRs), NMDA receptors (NRs), and D1 dopamine receptors (D1Rs). Here, we demonstrate that inputs from the AL are transmitted to the MBs through nAChRs, and inputs from the AFV are transmitted by NRs. Dopamine signaling occurs downstream of both nAChR and NR activation, and requires simultaneous stimulation of both pathways. Dopamine release requires the activity of the rutabaga adenylyl cyclase in postsynaptic MB neurons, and release is restricted to MB neurons that receive coincident stimulation. Our results indicate that postsynaptic activity can gate presynaptic dopamine release to regulate plasticity. DOI: http://dx.doi.org/10.7554/eLife.21076.001 PMID:28117664

Morphology of presumptive rapidly adapting receptors in the rat bronchus.

PubMed Central

Kappagoda, C T; Skepper, J N; McNaughton, L; Siew, E E; Navaratnam, V

1990-01-01

The present investigation was undertaken in rats to determine whether sensory nerves exist in apposition to the bronchial microvessels which may function as rapidly adapting receptors (RAR). The primary and secondary bronchi on both sides were removed and processed for light and electron microscopy. Nerves were frequently found in relation to venules external to the muscle coat of bronchi. They comprised myelinated axons which ended individually as non-myelinated convoluted terminals enclosed within a loose capsule of attenuated cells. Serial sections showed that these terminals were not related to ganglion cells. Cervical vagal section and injection of HRP-WGA into the nodose ganglion provided corroborative evidence of the sensory nature of these terminals. Vagal section caused degenerative changes in the encapsulated nerve terminals in the bronchial walls and horseradish peroxidase labelling was demonstrable in such terminals. Moreover, immunocytochemical studies demonstrated the presence of calcitonin gene regulated peptide and substance P in these structures. It is suggested that they comprise the RAR. Encapsulated nerve terminals were not found in the epithelial layer, in the submucous coat or in the muscularis of bronchi. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 PMID:1691164

Stimulation of accumbal GABAA receptors inhibits delta2-, but not delta1-, opioid receptor-mediated dopamine efflux in the nucleus accumbens of freely moving rats.

PubMed

Aono, Yuri; Kiguchi, Yuri; Watanabe, Yuriko; Waddington, John L; Saigusa, Tadashi

2017-11-15

The nucleus accumbens contains delta-opioid receptors that may reduce inhibitory neurotransmission. Reduction in GABA A receptor-mediated inhibition of accumbal dopamine release due to delta-opioid receptor activation should be suppressed by stimulating accumbal GABA A receptors. As delta-opioid receptors are divided into delta2- and delta1-opioid receptors, we analysed the effects of the GABA A receptor agonist muscimol on delta2- and delta1-opioid receptor-mediated accumbal dopamine efflux in freely moving rats using in vivo microdialysis. Drugs were administered intracerebrally through the dialysis probe. Doses of compounds indicate total amount administered (mol) during 25-50min infusions. The delta2-opioid receptor agonist deltorphin II (25.0nmol)- and delta1-opioid receptor agonist DPDPE (5.0nmol)-induced increases in dopamine efflux were inhibited by the delta2-opioid receptor antagonist naltriben (1.5nmol) and the delta1-opioid receptor antagonist BNTX (150.0pmol), respectively. Muscimol (250.0pmol) inhibited deltorphin II (25.0nmol)-induced dopamine efflux. The GABA A receptor antagonist bicuculline (50.0pmol), which failed to affect deltorphin II (25.0nmol)-induced dopamine efflux, counteracted the inhibitory effect of muscimol on deltorphin II-induced dopamine efflux. Neither muscimol (250.0pmol) nor bicuculline (50.0 and 500.0pmol) altered DPDPE (5.0nmol)-induced dopamine efflux. The present results show that reduction in accumbal GABA A receptor-mediated inhibition of dopaminergic activity is necessary to produce delta2-opioid receptor-induced increase in accumbal dopamine efflux. This study indicates that activation of delta2- but not delta1-opioid receptors on the cell bodies and/or terminals of accumbal GABAergic interneurons inhibits GABA release and, accordingly, decreases GABA A receptor-mediated inhibition of dopaminergic terminals, resulting in enhanced accumbal dopamine efflux. Copyright © 2017 Elsevier B.V. All rights reserved.

Neuronal Depolarization Drives Increased Dopamine Synaptic Vesicle Loading via VGLUT.

PubMed

Aguilar, Jenny I; Dunn, Matthew; Mingote, Susana; Karam, Caline S; Farino, Zachary J; Sonders, Mark S; Choi, Se Joon; Grygoruk, Anna; Zhang, Yuchao; Cela, Carolina; Choi, Ben Jiwon; Flores, Jorge; Freyberg, Robin J; McCabe, Brian D; Mosharov, Eugene V; Krantz, David E; Javitch, Jonathan A; Sulzer, David; Sames, Dalibor; Rayport, Stephen; Freyberg, Zachary

2017-08-30

The ability of presynaptic dopamine terminals to tune neurotransmitter release to meet the demands of neuronal activity is critical to neurotransmission. Although vesicle content has been assumed to be static, in vitro data increasingly suggest that cell activity modulates vesicle content. Here, we use a coordinated genetic, pharmacological, and imaging approach in Drosophila to study the presynaptic machinery responsible for these vesicular processes in vivo. We show that cell depolarization increases synaptic vesicle dopamine content prior to release via vesicular hyperacidification. This depolarization-induced hyperacidification is mediated by the vesicular glutamate transporter (VGLUT). Remarkably, both depolarization-induced dopamine vesicle hyperacidification and its dependence on VGLUT2 are seen in ventral midbrain dopamine neurons in the mouse. Together, these data suggest that in response to depolarization, dopamine vesicles utilize a cascade of vesicular transporters to dynamically increase the vesicular pH gradient, thereby increasing dopamine vesicle content. Copyright © 2017 Elsevier Inc. All rights reserved.

Neuronal Depolarization Drives Increased Dopamine Synaptic Vesicle Loading via VGLUT

PubMed Central

Aguilar, Jenny I.; Dunn, Matthew; Mingote, Susana; Karam, Caline S.; Farino, Zachary J.; Sonders, Mark S.; Choi, Se Joon; Grygoruk, Anna; Zhang, Yuchao; Cela, Carolina; Choi, Ben Jiwon; Flores, Jorge; Freyberg, Robin J.; McCabe, Brian D.; Mosharov, Eugene V.; Krantz, David E.; Javitch, Jonathan A.; Sulzer, David; Sames, Dalibor; Rayport, Stephen; Freyberg, Zachary

2017-01-01

SUMMARY The ability of presynaptic dopamine terminals to tune neurotransmitter release to meet the demands of neuronal activity is critical to neurotransmission. Although vesicle content has been assumed to be static, in vitro data increasingly suggest that cell activity modulates vesicle content. Here, we use a coordinated genetic, pharmacological, and imaging approach in Drosophila to study the presynaptic machinery responsible for these vesicular processes in vivo. We show that cell depolarization increases synaptic vesicle dopamine content prior to release via vesicular hyperacidification. This depolarization-induced hyperacidification is mediated by the vesicular glutamate transporter (VGLUT). Remarkably, both depolarization-induced dopamine vesicle hyperacidification and its dependence on VGLUT2 are seen in ventral midbrain dopamine neurons in the mouse. Together, these data suggest that in response to depolarization, dopamine vesicles utilize a cascade of vesicular transporters to dynamically increase the vesicular pH gradient, thereby increasing dopamine vesicle content. PMID:28823729

Palisade endings are present in canine extraocular muscles and have a cholinergic phenotype

PubMed Central

RUNGALDIER, Stefanie; POMIKAL, Christine; STREICHER, Johannes; BLUMER, Roland

2016-01-01

Classical proprioceptors, like Golgi tendon organs and muscle spindles are absent in the extraocular muscles (EOMs) of most mammals. Instead, a nerve end organ was detected in the EOMs of each species including sheep, cats, rabbits, rats, monkeys, and man examined so far: the palisade ending. Until now no evidence appeared that palisade endings are present in canine EOMs. We analyzed dog EOMs by confocal laser scanning microscopy, 3D reconstruction, and transmission electron microscopy. In EOM wholemount preparations stained with antibodies against neurofilament and synaptophysin we found typical palisade endings. Nerve fibers coming from the muscle extended into the tendon. There, the nerve fibers turned 180° and returned to branch into preterminal axons which established nerve terminals around a single muscle fiber tip. Fine structural analyses revealed that each palisade ending in dog EOMs established nerve terminals on the tendon. In some palisade endings we found nerve terminals contacting the muscle fiber as well. Such neuromuscular contacts had a basal lamina in the synaptic cleft thereby resembling motor terminals. By using antibodies against choline acetyltransferase (ChAT) we proved that canine palisade endings are ChAT-immunoreactive. This study shows that palisade endings are present in canine EOMs. In line with prior findings in cat and monkey, palisade endings in dog have a cholinergic phenotype. PMID:19766165

Compartmentalized beta subunit distribution determines characteristics and ethanol sensitivity of somatic, dendritic, and terminal large-conductance calcium-activated potassium channels in the rat central nervous system.

PubMed

Wynne, P M; Puig, S I; Martin, G E; Treistman, S N

2009-06-01

Neurons are highly differentiated and polarized cells, whose various functions depend upon the compartmentalization of ion channels. The rat hypothalamic-neurohypophysial system (HNS), in which cell bodies and dendrites reside in the hypothalamus, physically separated from their nerve terminals in the neurohypophysis, provides a particularly powerful preparation in which to study the distribution and regional properties of ion channel proteins. Using electrophysiological and immunohistochemical techniques, we characterized the large-conductance calcium-activated potassium (BK) channel in each of the three primary compartments (soma, dendrite, and terminal) of HNS neurons. We found that dendritic BK channels, in common with somatic channels but in contrast to nerve terminal channels, are insensitive to iberiotoxin. Furthermore, analysis of dendritic BK channel gating kinetics indicates that they, like somatic channels, have fast activation kinetics, in contrast to the slow gating of terminal channels. Dendritic and somatic channels are also more sensitive to calcium and have a greater conductance than terminal channels. Finally, although terminal BK channels are highly potentiated by ethanol, somatic and dendritic channels are insensitive to the drug. The biophysical and pharmacological properties of somatic and dendritic versus nerve terminal channels are consistent with the characteristics of exogenously expressed alphabeta1 versus alphabeta4 channels, respectively. Therefore, one possible explanation for our findings is a selective distribution of auxiliary beta1 subunits to the somatic and dendritic compartments and beta4 to the terminal compartment. This hypothesis is supported immunohistochemically by the appearance of distinct punctate beta1 or beta4 channel clusters in the membrane of somatic and dendritic or nerve terminal compartments, respectively.

Synthesis of dopamine in E. coli using plasmid-based expression system and its marked effect on host growth profiles.

PubMed

Das, Arunangshu; Verma, Anita; Mukherjee, Krishna J

2017-09-14

L-Dopa and dopamine are important pathway intermediates toward the synthesis of catecholamine such as epinephrine and norepinephrine from amino acid L-tyrosine. Dopamine, secreted from dopaminergic nerve cells, serves as an important neurotransmitter. We report the synthesis of dopamine by extending the aromatic amino acid pathway of Escherichia coli DH5α by the expression of 4-hydroxyphenylacetate-3-hydrolase (HpaBC) from E. coli and an engineered dopa decarboxylase (DDC) from pig kidney cell. The activity of HpaBC and DDC require 200 µM iron supplementation and 50 µM vitamin B6, respectively as additives to the growth media. The maximum concentration of L-dopa and dopamine obtained from the broth was around 26 and 27 mg/L after 24 hr of separate shake flask studies. We observed that in the presence of dopamine synthesized in vivo host growth was remarkably enhanced. These observations lead us to an interesting finding about the role of these catecholamines on bacterial growth. It is clear that synthesis of dopamine in vivo actually promotes growth much efficiently as compared to when dopamine is added to the system from outside. From HPLC and GC-MS data it was further observed that L-dopa was stable within the observable time of experiments whereas dopamine actually was subjected to degradation via oxidation and host consumption.

Classical Neurotransmitters and their Significance within the Nervous System.

ERIC Educational Resources Information Center

Veca, A.; Dreisbach, J. H.

1988-01-01

Describes some of the chemical compounds involved in the nervous system and their roles in transmitting nerve signals. Discusses acetylcholine, dopamine, norepinephrine, serotonin, histamine, glycine, glutemate, and gamma-aminobutyric acid and their effects within the nervous system. (CW)

Increase of transcription factor EB (TFEB) and lysosomes in rat DRG neurons and their transportation to the central nerve terminal in dorsal horn after nerve injury.

PubMed

Jung, J; Uesugi, N; Jeong, N Y; Park, B S; Konishi, H; Kiyama, H

2016-01-28

In the spinal dorsal horn (DH), nerve injury activates microglia and induces neuropathic pain. Several studies clarified an involvement of adenosine triphosphate (ATP) in the microglial activation. However, the origin of ATP together with the release mechanism is unclear. Recent in vitro study revealed that an ATP marker, quinacrine, in lysosomes was released from neurite terminal of dorsal root ganglion (DRG) neurons to extracellular space via lysosomal exocytosis. Here, we demonstrate a possibility that the lysosomal ingredient including ATP released from DRG neurons by lysosomal-exocytosis is an additional source of the glial activation in DH after nerve injury. After rat L5 spinal nerve ligation (SNL), mRNA for transcription factor EB (TFEB), a transcription factor controlling lysosomal activation and exocytosis, was induced in the DRG. Simultaneously both lysosomal protein, LAMP1- and vesicular nuclear transporter (VNUT)-positive vesicles were increased in L5 DRG neurons and ipsilateral DH. The quinacrine staining in DH was increased and co-localized with LAMP1 immunoreactivity after nerve injury. In DH, LAMP1-positive vesicles were also co-localized with a peripheral nerve marker, Isolectin B4 (IB4) lectin. Injection of the adenovirus encoding mCherry-LAMP1 into DRG showed that mCherry-positive lysosomes are transported to the central nerve terminal in DH. These findings suggest that activation of lysosome synthesis including ATP packaging in DRG, the central transportation of the lysosome, and subsequent its exocytosis from the central nerve terminal of DRG neurons in response to nerve injury could be a partial mechanism for activation of microglia in DH. This lysosome-mediated microglia activation mechanism may provide another clue to control nociception and pain. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

Identification of a null mutation in the human dopamine D4 receptor gene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noethen, M.M.; Cichon, S.; Hebebrand, J.

1994-09-01

Dopamine receptors belong to the family of G protein-coupled receptors. Five different dopamine receptor genes have thus far been identified. These receptors are classified into two main subfamilies: D1, which includes the D1 and D5 receptors, and D2, which includes the D2, D3, and D4 receptors. The dopamine D4 receptor is of great interest for research into neuropsychiatric disorders and psychopharmacology in light of the fact that it binds the antipsychotic medication clozapine with higher affinity than does any other dopamine receptor. In addition, among the dopamine receptors, the D4 receptor shows a uniquely high degree of genetic variation inmore » the human population. We identified a new 13 bp deletion in exon 1 of the D4 gene. This frameshift creates a terminator codon at amino acid position 98. mRNA isolated from brain tissue of two heterozygous persons showed both alleles to be expressed. The deletion occurs with a frequency of 2% in the German population. One person was identified to be homozygous for the deletion. Interestingly, he has a normal intelligence and did not exhibit a major psychiatric disorder as defined by DSM III-R. The 13 bp deletion is the first mutation resulting in premature translation termination reported for a dopamine receptor gene so far. This mutation is a good candidate to test for potential effects on disease and/or individual response to pharmacotherapy. Association studies in patients with various psychiatric illnesses and differences in response to clozapine are underway.« less

Prejunctional and postjunctional actions of heptanol and 18 beta-glycyrretinic acid in the rodent vas deferens.

PubMed

Rahman, Faisal; Manchanda, Rohit; Brain, Keith L

2009-06-15

Heptanol and 18 beta-glycyrrhetinic acid (18 beta GA) block gap junctions, but have other actions on transmitter release that have not been characterised. This study investigates the prejunctional and postjunctional effects of these compounds in guinea pig and mouse vas deferens using intracellular electrophysiological recording and confocal Ca(2+) imaging of sympathetic nerve terminals. In mice, heptanol (2 mM) reversibly decreased the amplitude of purinergic excitatory junction potentials (EJPs; 52+/-5%, P<0.05) while having little effect on spontaneous excitatory junction potentials (sEJPs). Heptanol (2 mM) reversibly abolished the nerve terminal Ca(2+) transient in 52% of terminals. 18 beta GA (10 microM) decreased the mean EJP amplitude, and increased input resistance in both mouse (137+/-17%, P<0.05) and guinea pig (354+/-50%, P<0.001) vas deferens indicating gap junction blockade. Further, 18 beta GA increased the sEJP frequency significantly in guinea pigs (by 71+/-25%, P<0.05) and in 5 out of 6 tissues in mice (19+/-3%, P<0.05). Moreover, 18 beta GA depolarised cells from both mice (11+/-1%, P<0.01) and guinea pigs (8+/-1%, P<0.005). Therefore, we conclude that heptanol (2 mM) decreases neurotransmitter release (given the decrease in EJP amplitude) by abolishing the nerve terminal action potential in a proportion of nerve terminals. 18 betaGA (10 microM) effectively blocks the gap junctions, but the increase in sEJP frequency suggests an additional prejunctional effect, which might involve the induction of spontaneous nerve terminal action potentials.

Epothilone D prevents binge methamphetamine-mediated loss of striatal dopaminergic markers.

PubMed

Killinger, Bryan A; Moszczynska, Anna

2016-02-01

Exposure to binge methamphetamine (METH) can result in a permanent or transient loss of dopaminergic (DAergic) markers such as dopamine (DA), dopamine transporter, and tyrosine hydroxylase (TH) in the striatum. We hypothesized that the METH-induced loss of striatal DAergic markers was, in part, due to a destabilization of microtubules (MTs) in the nigrostriatal DA pathway that ultimately impedes anterograde axonal transport of these markers. To test this hypothesis, adult male Sprague-Dawley rats were treated with binge METH or saline in the presence or absence of epothilone D (EpoD), a MT-stabilizing compound, and assessed 3 days after the treatments for the levels of several DAergic markers as well as for the levels of tubulins and their post-translational modifications (PMTs). Binge METH induced a loss of stable long-lived MTs within the striatum but not within the substantia nigra pars compacta (SNpc). Treatment with a low dose of EpoD increased the levels of markers of stable MTs and prevented METH-mediated deficits in several DAergic markers in the striatum. In contrast, administration of a high dose of EpoD appeared to destabilize MTs and potentiated the METH-induced deficits in several DAergic markers. The low-dose EpoD also prevented the METH-induced increase in striatal DA turnover and increased behavioral stereotypy during METH treatment. Together, these results demonstrate that MT dynamics plays a role in the development of METH-induced losses of several DAergic markers in the striatum and may mediate METH-induced degeneration of terminals in the nigrostriatal DA pathway. Our study also demonstrates that MT-stabilizing drugs such as EpoD have a potential to serve as useful therapeutic agents to restore function of DAergic nerve terminals following METH exposure when administered at low doses. Administration of binge methamphetamine (METH) negatively impacts neurotransmission in the nigrostriatal dopamine (DA) system. The effects of METH include decreasing the levels of DAergic markers in the striatum. We have determined that high-dose METH destabilizes microtubules in this pathway, which is manifested by decreased levels of acetylated (Acetyl) and detyrosinated (Detyr) α-tubulin (I). A microtubule stabilizing agent epothilone D protects striatal microtubules form the METH-induced loss of DAergic markers (II). These findings provide a new strategy for protection form METH - restoration of proper axonal transport. © 2015 International Society for Neurochemistry.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dilts, R.P. Jr.

In vitro autoradiographic techniques were coupled with selective chemical lesions of the A10 dopamine cells and intrinsic perikarya of the region to delineate the anatomical localization of mu and delta opioid receptors, as well as, neurotensin receptors. Mu opioid receptors were labeled with {sup 125}I-DAGO. Delta receptors were labeled with {sup 125}I-DPDPE. Neurotensin receptors were labeled with {sup 125}I-NT3. Unilateral lesions of the dopamine perikarya were produced by injections of 6-OHDA administered in the ventral mesencephalon. Unilateral lesions of intrinsic perikarya were induced by injections of quinolinic acid in to the A10 dopamine cell region. Unilateral lesions produced with 6-OHDAmore » resulted in the loss of neurotensin receptors in the A10 region and within the terminal fields. Mu opioid receptors were unaffected by this treatment, but delta opioid receptors increased in the contralateral striatum and nucleus accumbens following 6-OHDA administration. Quinolinic acid produced a reduction of mu opioid receptors within the A10 region with a concomitant reduction in neurotensin receptors in both the cell body region and terminal fields. These results are consistent with a variety of biochemical and behavioral data which suggest the indirect modulation of dopamine transmission by the opioids. In contrast these results strongly indicate a direct modulation of the mesolimbic dopamine system by neurotensin.« less

Vulnerability to glutamate toxicity of dopaminergic neurons is dependent on endogenous dopamine and MAPK activation.

PubMed

Izumi, Yasuhiko; Yamamoto, Noriyuki; Matsuo, Takaaki; Wakita, Seiko; Takeuchi, Hiroki; Kume, Toshiaki; Katsuki, Hiroshi; Sawada, Hideyuki; Akaike, Akinori

2009-07-01

Dopaminergic neurons are more vulnerable than other types of neurons in cases of Parkinson disease and ischemic brain disease. An increasing amount of evidence suggests that endogenous dopamine plays a role in the vulnerability of dopaminergic neurons. Although glutamate toxicity contributes to the pathogenesis of these disorders, the sensitivity of dopaminergic neurons to glutamate toxicity has not been clarified. In this study, we demonstrated that dopaminergic neurons were preferentially affected by glutamate toxicity in rat mesencephalic cultures. Glutamate toxicity in dopaminergic neurons was blocked by inhibiting extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase, and p38 MAPK. Furthermore, depletion of dopamine by alpha-methyl-dl-p-tyrosine methyl ester (alpha-MT), an inhibitor of tyrosine hydroxylase (TH), protected dopaminergic neurons from the neurotoxicity. Exposure to glutamate facilitated phosphoryration of TH at Ser31 by ERK, which contributes to the increased TH activity. Inhibition of ERK had no additive effect on the protection offered by alpha-MT, whereas alpha-MT and c-jun N-terminal kinase or p38 MAPK inhibitors had additive effects and yielded full protection. These data suggest that endogenous dopamine is responsible for the vulnerability to glutamate toxicity of dopaminergic neurons and one of the mechanisms may be an enhancement of dopamine synthesis mediated by ERK.

Long-term dopamine transporter expression and normal cellular distribution of mitochondria in dopaminergic neuron transplants in Parkinson’s disease patients

PubMed Central

Hallett, Penelope J; Cooper, Oliver; Sadi, Damaso; Robertson, Harold; Mendez, Ivar; Isacson, Ole

2014-01-01

Summary To determine the long-term health and function of transplanted dopamine neurons in Parkinson’s disease (PD) patients, the expression of dopamine transporters (DAT) and mitochondrial morphology was examined in human fetal midbrain cellular transplants. DAT was robustly expressed in transplanted dopamine neuron terminals in the reinnervated host putamen and caudate, for at least 14 years after transplantation. The transplanted dopamine neurons showed a healthy and non-atrophied morphology at all time points. Labeling of the mitochondrial outer membrane protein Tom20 and alpha-synuclein showed typical cellular pathology in the patients’ own substantia nigra, which was not observed in transplanted dopamine neurons. These results show that the vast majority of transplanted neurons remain healthy long-term in PD patients, consistent with the clinically maintained function of fetal dopamine neuron transplants for up to 15–18 years in patients. These findings are critically important for the rational development of stem cell-based dopamine neuronal replacement therapies for PD. PMID:24910427

[Experimental studies for the improvement of facial nerve regeneration].

PubMed

Guntinas-Lichius, O; Angelov, D N

2008-02-01

Using a combination of the following, it is possible to investigate procedures to improve the morphological and functional regeneration of the facial nerve in animal models: 1) retrograde fluorescence tracing to analyse collateral axonal sprouting and the selectivity of reinnervation of the mimic musculature, 2) immunohistochemistry to analyse both the terminal axonal sprouting in the muscles and the axon reaction within the nucleus of the facial nerve, the peripheral nerve, and its environment, and 3) digital motion analysis of the muscles. To obtain good functional facial nerve regeneration, a reduction of terminal sprouting in the mimic musculature seems to be more important than a reduction of collateral sprouting at the lesion site. Promising strategies include acceleration of nerve regeneration, forced induced use of the paralysed face, mechanical stimulation of the face, and transplantation of nerve-growth-promoting olfactory epithelium at the lesion site.

Cortical ionotropic glutamate receptor antagonism protects against methamphetamine-induced striatal neurotoxicity.

PubMed

Gross, N B; Duncker, P C; Marshall, J F

2011-12-29

Binge administration of the psychostimulant drug, methamphetamine (mAMPH), produces long-lasting structural and functional abnormalities in the striatum. mAMPH binges produce nonexocytotic release of dopamine (DA), and mAMPH-induced activation of excitatory afferent inputs to cortex and striatum is evidenced by elevated extracellular glutamate (GLU) in both regions. The mAMPH-induced increases in DA and GLU neurotransmission are thought to combine to injure striatal DA nerve terminals of mAMPH-exposed brains. Systemic pretreatment with either competitive or noncompetitive N-methyl-D-aspartic acid (NMDA) antagonists protects against mAMPH-induced striatal DA terminal damage, but the locus of these antagonists' effects has not been determined. Here, we applied either the NMDA receptor antagonist, (dl)-amino-5-phosphonovaleric acid (AP5), or the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist, dinitroquinoxaline-2,3-dione (DNQX), directly to the dura mater over frontoparietal cortex to assess their effects on mAMPH-induced cortical and striatal immediate-early gene (c-fos) expression. In a separate experiment we applied AP5 or DNQX epidurally in the same cortical location of rats during a binge regimen of mAMPH and assessed mAMPH-induced striatal dopamine transporter (DAT) depletions 1 week later. Our results indicate that both ionotropic glutamate receptor antagonists reduced the mAMPH-induced Fos expression in cerebral cortex regions near the site of epidural application and reduced Fos immunoreactivity in striatal regions innervated by the affected cortical regions. Also, epidural application of the same concentration of either antagonist during a binge mAMPH regimen blunted the mAMPH-induced striatal DAT depletions with a topography similar to its effects on Fos expression. These findings demonstrate that mAMPH-induced dopaminergic injury depends upon cortical NMDA and AMPA receptor activation and suggest the involvement of the corticostriatal projections in mAMPH neurotoxicity. Copyright © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.

The nervus terminalis in the chick: a FMRFamide-immunoreactive and AChE-positive nerve.

PubMed

Wirsig-Wiechmann, C R

1990-07-16

The chick terminal nerve (TN) was examined by immunocytochemical and histochemical methods. Molluscan cardioexcitatory peptide-immunoreactive (FMRFamide-ir) and acetylcholinesterase (AChE)-positive TN perikarya and fibers were distributed along olfactory and trigeminal nerves. FMRFamide-ir TN fibers terminated in the olfactory lamina propria and epithelium and in ganglia along the rostroventral nasal septum. This initial description of several populations of avian TN neurons should provide the foundation for future developmental studies of this system.

Peripheral nerve hyperexcitability with preterminal nerve and neuromuscular junction remodeling is a hallmark of Schwartz-Jampel syndrome.

PubMed

Bauché, Stéphanie; Boerio, Delphine; Davoine, Claire-Sophie; Bernard, Véronique; Stum, Morgane; Bureau, Cécile; Fardeau, Michel; Romero, Norma Beatriz; Fontaine, Bertrand; Koenig, Jeanine; Hantaï, Daniel; Gueguen, Antoine; Fournier, Emmanuel; Eymard, Bruno; Nicole, Sophie

2013-12-01

Schwartz-Jampel syndrome (SJS) is a recessive disorder with muscle hyperactivity that results from hypomorphic mutations in the perlecan gene, a basement membrane proteoglycan. Analyses done on a mouse model have suggested that SJS is a congenital form of distal peripheral nerve hyperexcitability resulting from synaptic acetylcholinesterase deficiency, nerve terminal instability with preterminal amyelination, and subtle peripheral nerve changes. We investigated one adult patient with SJS to study this statement in humans. Perlecan deficiency due to hypomorphic mutations was observed in the patient biological samples. Electroneuromyography showed normal nerve conduction, neuromuscular transmission, and compound nerve action potentials while multiple measures of peripheral nerve excitability along the nerve trunk did not detect changes. Needle electromyography detected complex repetitive discharges without any evidence for neuromuscular transmission failure. The study of muscle biopsies containing neuromuscular junctions showed well-formed post-synaptic element, synaptic acetylcholinesterase deficiency, denervation of synaptic gutters with reinnervation by terminal sprouting, and long nonmyelinated preterminal nerve segments. These data support the notion of peripheral nerve hyperexcitability in SJS, which would originate distally from synergistic actions of peripheral nerve and neuromuscular junction changes as a result of perlecan deficiency. Copyright © 2013 Elsevier B.V. All rights reserved.

Integration of Synaptic Vesicle Cargo Retrieval with Endocytosis at Central Nerve Terminals

PubMed Central

Cousin, Michael A.

2017-01-01

Central nerve terminals contain a limited number of synaptic vesicles (SVs) which mediate the essential process of neurotransmitter release during their activity-dependent fusion. The rapid and accurate formation of new SVs with the appropriate cargo is essential to maintain neurotransmission in mammalian brain. Generating SVs containing the correct SV cargo with the appropriate stoichiometry is a significant challenge, especially when multiple modes of endocytosis exist in central nerve terminals, which occur at different locations within the nerve terminals. These endocytosis modes include ultrafast endocytosis, clathrin-mediated endocytosis (CME) and activity-dependent bulk endocytosis (ADBE) which are triggered by specific patterns of neuronal activity. This review article will assess the evidence for the role of classical adaptor protein complexes in SV retrieval, discuss the role of monomeric adaptors and how interactions between specific SV cargoes can facilitate retrieval. In addition it will consider the evidence for preassembled plasma membrane cargo complexes and their role in facilitating these endocytosis modes. Finally it will present a unifying model for cargo retrieval at the presynapse, which integrates endocytosis modes in time and space. PMID:28824381

Effects of Nicotine and Ethanol on Indices of Reward and Sensory-Motor Function in Rats: Implications for the Positive Epidemiologic Relationship Between the Use of Cigarettes and the Use of Alcohol

DTIC Science & Technology

1997-10-07

include the auditory nerve, the ventral cochlear nucleus , nuclei of the lateral lemniscus, nucleus reticularis pontis caudalis, spinal neuron, and lower...chambers. In addition, there was a significant effect of nicotine and ethanol to reduce the ratio of dopamine/DOPAC in nucleus accumbens. Because...dopaminergic activity in nucleus accumbens is known to mediate nicotine reinforcement, reductions in the ratio of dopamine/DOPAC (perhaps indicating an

Genetic and pharmacological evidence that endogenous nociceptin/orphanin FQ contributes to dopamine cell loss in Parkinson's disease.

PubMed

Arcuri, Ludovico; Viaro, Riccardo; Bido, Simone; Longo, Francesco; Calcagno, Mariangela; Fernagut, Pierre-Olivier; Zaveri, Nurulain T; Calò, Girolamo; Bezard, Erwan; Morari, Michele

2016-05-01

To investigate whether the endogenous neuropeptide nociceptin/orphanin FQ (N/OFQ) contributes to the death of dopamine neurons in Parkinson's disease, we undertook a genetic and a pharmacological approach using NOP receptor knockout (NOP(-/-)) mice, and the selective and potent small molecule NOP receptor antagonist (-)-cis-1-methyl-7-[[4-(2,6-dichlorophenyl)piperidin-1-yl]methyl]-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol (SB-612111). Stereological unbiased methods were used to estimate the total number of dopamine neurons in the substantia nigra of i) NOP(-/-) mice acutely treated with the parkinsonian neurotoxin 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP), ii) naïve mice subacutely treated with MPTP, alone or in combination with SB-612111, iii) rats injected with a recombinant adeno-associated viral (AAV) vector overexpressing human mutant p.A53T α-synuclein, treated with vehicle or SB-612111. NOP(-/-) mice showed a 50% greater amount of nigral dopamine neurons spared in response to acute MPTP compared to controls, which was associated with a milder motor impairment. SB-612111, given 4 days after MPTP treatment to mimic the clinical condition, prevented the loss of nigral dopamine neurons and striatal dopaminergic terminals caused by subacute MPTP. SB-612111, administered a week after the AAV injections in a clinically-driven protocol, also increased by 50% both the number of spared nigral dopamine neurons and striatal dopamine terminals, and prevented accompanying motor deficits induced by α-synuclein. We conclude that endogenous N/OFQ contributes to dopamine neuron loss in pathogenic and etiologic models of Parkinson's disease through NOP receptor-mediated mechanisms. NOP receptor antagonists might prove effective as disease-modifying agents in Parkinson's disease, through the rescue of degenerating nigral dopamine neurons and/or the protection of the healthy ones. Copyright © 2016. Published by Elsevier Inc.

Effect of O-methyl-β-cyclodextrin-modified magnetic nanoparticles on the uptake and extracellular level of l-glutamate in brain nerve terminals.

PubMed

Horák, Daniel; Beneš, Milan; Procházková, Zuzana; Trchová, Miroslava; Borysov, Arsenii; Pastukhov, Artem; Paliienko, Konstantin; Borisova, Tatiana

2017-01-01

Changes in cholesterol concentration in the plasma membrane of presynaptic nerve terminals nonspecifically modulate glutamate transport and homeostasis in the central nervous system. Reduction of the cholesterol content in isolated rat brain nerve terminals (synaptosomes) using cholesterol-depleting agents decreases the glutamate uptake and increases the extracellular level of glutamate in nerve terminals. Extraction of cholesterol from the plasma membrane and its further removal from the synaptosomes by external magnetic field can be achieved by means of magnetic nanoparticles with immobilized cholesterol-depleting agent such as O-methyl-β-cyclodextrin (MCD). A simple approach is developed for preparation of maghemite (γ-Fe 2 O 3 ) nanoparticles containing chemically bonded MCD. The method is based on preparation of a silanization agent containing MCD. It is synthesized by the reaction of triethoxy(3-isocyanatopropyl)silane with MCD. Base-catalyzed silanization of superparamagnetic γ-Fe 2 O 3 provides a relatively stable colloid product containing 48μmol of MCDg -1 . MCD-modified γ-Fe 2 O 3 nanoparticles decrease the initial rate of the uptake and accumulation of l-[ 14 C]glutamate and increase the extracellular l-[ 14 C]glutamate level in the preparation of nerve terminals. The effect of MCD-immobilized nanoparticles is the same as that of MCD solution; moreover, magnetic manipulation of the nanoparticles enables removal of bonded cholesterol. Copyright © 2016 Elsevier B.V. All rights reserved.

A top-down perspective on dopamine, motivation and memory.

PubMed

Phillips, Anthony G; Vacca, Giada; Ahn, Soyon

2008-08-01

Dopamine (DA) activity, in the form of increased neural firing or enhanced release of transmitter from nerve terminals and varicosities, is linked to a number of important psychological processes including: movement; hedonic reactions to positive reward; provision of an error detection signal during the acquisition of new learning; response to novel stimuli; provision of reinforcement signals essential for acquisition of new action patterns; and incentive motivation. This review focuses primarily on our research linking dynamic changes in DA efflux on the timescale of minutes, with incentive motivation, as revealed by brain dialysis experiments in behaving animals. Recent experiments on sensory-specific satiety and successive positive and negative contrast are discussed along with the distinction between preparatory behaviors that precede contact with biologically significant stimuli and subsequent consummatory behaviors. The relationship between DA efflux in the medial prefrontal cortex (mPFC) and foraging for food based on working memory is also discussed in support of the conjecture that DA may serve as a link between motivation and memory functions. Evidence in support of 'top-down' regulation of dopaminergic activity in the mesocorticolimbic DA pathways is reviewed briefly to introduce a mechanism by which activation of ascending DA projections in this manner might optimize dopaminergic modulation of executive function within regions such as the mPFC. Collectively, these processes could ensure coordination between cognitive processes that assess current opportunities and the motivational systems that select and engage patterns of approach behavior that bring organisms into contact with the essentials for survival.

Lacosamide diminishes dryness-induced hyperexcitability of corneal cold sensitive nerve terminals.

PubMed

Kovács, Illés; Dienes, Lóránt; Perényi, Kristóf; Quirce, Susana; Luna, Carolina; Mizerska, Kamila; Acosta, M Carmen; Belmonte, Carlos; Gallar, Juana

2016-09-15

Lacosamide is an anti-epileptic drug that is also used for the treatment of painful diabetic neuropathy acting through voltage-gated sodium channels. The aim of this work was to evaluate the effects of acute application of lacosamide on the electrical activity of corneal cold nerve terminals in lacrimo-deficient guinea pigs. Four weeks after unilateral surgical removal of the main lachrimal gland in guinea pigs, corneas were excised and superfused in vitro at 34°C for extracellular electrophysiological recording of nerve terminal impulse activity of cold thermosensitive nerve terminals. The characteristics of the spontaneous and the stimulus-evoked (cooling ramps from 34°C to 15°C) activity before and in presence of lacosamide 100µM and lidocaine 100µM were compared. Cold nerve terminals (n=34) recorded from dry eye corneas showed significantly enhanced spontaneous activity (8.0±1.1 vs. 5.2±0.7imp/s; P<0.05) and cold response (21.2±1.7 vs. 16.8±1.3imp/s; P<0.05) as well as reduced cold threshold (1.5±0.1 vs. 2.8±0.2 Δ°C; P<0.05) to cooling ramps compared to terminals (n=58) from control animals. Both lacosamide and lidocaine decreased spontaneous activity and peak response to cooling ramps significantly (P<0.05). Temperature threshold was increased by the addition of lidocaine (P<0.05) but not lacosamide (P>0.05) to the irrigation fluid. In summary, the application of lacosamide results in a significant decrease of the augmented spontaneous activity and responsiveness to cold of corneal sensory nerves from tear-deficient animals. Based on these promising results we speculate that lacosamide might be used to reduce the hyperexcitability of corneal cold receptors caused by prolonged ocular surface dryness due to hyposecretory or evaporative dry eye disease. Copyright © 2016 Elsevier B.V. All rights reserved.

Modulating dopamine release by optogenetics in transgenic mice reveals terminal dopaminergic dynamics

PubMed Central

Lu, Yao; Driscoll, Nicolette; Ozden, Ilker; Yu, Zeyang; Nurmikko, Arto V.

2015-01-01

Abstract. Dopamine (DA) release and uptake dynamics in the nucleus accumbens (NAc) have important implications for neurological diseases and mammalian animal behaviors. We demonstrate here the use of cell-type-specific optogenetic targeting in conjunction with fast-scan cyclic voltammetry applied to brain slices prepared from specifically tailored transgenic mice, which conditionally express channelrhodopsin-2 (ChR2) through dopamine transporter (DAT)-Cre. Terminal dopaminergic dynamics and the direct manipulation of induced DA release level by controlling light intensity, pulse width, and the shape of stimulation waveforms were studied. Effective cell terminal-targeting optogenetic induction of DA release at physiological levels in NAc is demonstrated and discussed. It was found that delivering more light energy by increasing stimulation intensity and length is not the only way to control DA release; the temporal shape of the stimulus waveform at light onset is also critically related to induced DA concentrations. In addition, DA uptake dynamics as well as the recovery of the presynaptic releasable DA pool are studied and modeled. More broadly, our experimental findings provide important further evidence for effectively applying optogenetics to induce neurotransmitter release in the behaviorally relevant region of the brain in a highly cell-type selective context. PMID:26171413

Quantitative monitoring of activity-dependent bulk endocytosis of synaptic vesicle membrane by fluorescent dextran imaging

PubMed Central

Clayton, Emma Louise; Cousin, Michael Alan

2012-01-01

Activity-dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle (SV) retrieval mode in central nerve terminals during periods of intense neuronal activity. Despite this fact there are very few real time assays that report the activity of this critical SV retrieval mode. In this paper we report a simple and quantitative assay of ADBE using uptake of large flourescent dextrans as fluid phase markers. We show that almost all dextran uptake occurs in nerve terminals, using co-localisation with the fluorescent probe FM1-43. We also demonstrate that accumulated dextran cannot be unloaded by neuronal stimulation, indicating its specific loading into bulk endosomes and not SVs. Quantification of dextran uptake was achieved by using thresholding analysis to count the number of loaded nerve terminals, since monitoring the average fluorescence intensity of these nerve terminals did not accurately report the extent of ADBE. Using this analysis we showed that dextran uptake occurs very soon after stimulation and that it does not persist when stimulation terminates. Thus we have devised a simple and quantitative method to monitor ADBE in living neurones, which will be ideal for real time screening of small molecule inhibitors of this key SV retrieval mode. PMID:19766140

Long-term health of dopaminergic neuron transplants in Parkinson's disease patients.

PubMed

Hallett, Penelope J; Cooper, Oliver; Sadi, Damaso; Robertson, Harold; Mendez, Ivar; Isacson, Ole

2014-06-26

To determine the long-term health and function of transplanted dopamine neurons in Parkinson's disease (PD) patients, the expression of dopamine transporters (DATs) and mitochondrial morphology were examined in human fetal midbrain cellular transplants. DAT was robustly expressed in transplanted dopamine neuron terminals in the reinnervated host putamen and caudate for at least 14 years after transplantation. The transplanted dopamine neurons showed a healthy and nonatrophied morphology at all time points. Labeling of the mitochondrial outer membrane protein Tom20 and α-synuclein showed a typical cellular pathology in the patients' own substantia nigra, which was not observed in transplanted dopamine neurons. These results show that the vast majority of transplanted neurons remain healthy for the long term in PD patients, consistent with clinical findings that fetal dopamine neuron transplants maintain function for up to 15-18 years in patients. These findings are critically important for the rational development of stem-cell-based dopamine neuronal replacement therapies for PD. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Characterization of human dopamine responsive protein DRG-1 that binds to p75NTR-associated cell death executor NADE.

PubMed

Yu, Yao; Wang, Jiadong; Yuan, Hanying; Qin, Feng; Wang, Jing; Zhang, Nailing; Li, Yu-Yang; Liu, Jianping; Lu, Hong

2006-07-19

Expression of human dopamine responsive gene-1 (DRG-1) is up-regulated in response to treatment of dopamine in the rat astrocytes. However, its functions are not clear up to now. In the presented studies, DRG-1 was identified to be a conserved gene in the vertebrate and expressed abundantly in human testis, brain and skeletal muscle. DRG-1 was shown to interact with human p75NTR-associated cell death executor (NADE) in vivo and in vitro, and the interaction occurred in cytoplasm. The regions required for the interaction were subsequently mapped to the N-terminal of DRG-1 and the C-terminal of NADE. Furthermore, MTT assay showed that stable expression of DRG-1 in 293 cells could promote cell proliferation, and this promotion was suppressed by overexpression of NADE. In flow cytometry cell cycle analysis, overexpression of DRG-1 in 293 or PC12 cells increased the population of cells in the S phase with a concomitant decrease in G0/G1 population. These findings suggest that DRG-1 may contribute to the dopamine-induced cell growth, which is negatively regulated by NADE.

Dopamine disposition in the presynaptic process regulates the severity of methamphetamine-induced neurotoxicity.

PubMed

Kuhn, Donald M; Francescutti-Verbeem, Dina M; Thomas, David M

2008-10-01

Methamphetamine (METH) is well known for its ability to cause damage to dopamine (DA) nerve endings of the striatum. The mechanisms by which METH causes neurotoxicity are not fully understood, but likely candidates are increased oxidative and nitrosative stress and mitochondrial dysfunction. Microglial activation is also emerging as an important element of the METH neurotoxic cascade, and it appears that extensive cross-talk between these cells and DA nerve endings is an early event in this process. It may seem paradoxical, but DA itself is also thought to be an essential factor in the neuronal damaging effects of METH, but issues relating to its precise role in this regard remain unanswered. We present in this overview a summary of studies that tested how alterations in the disposition of presynaptic DA (injections of reserpine, L-DOPA, or clorgyline) modulate METH neurotoxicity. In all cases, these drugs significantly increased the magnitude of microglial activation as well as the severity of damage to striatal DA nerve endings caused by METH. The enhancement of METH effects in striatum by reserpine, L-DOPA, and clorgyline persisted for 14 days and showed no evidence of recovery. These data establish that subtle shifts in the newly synthesized pool of DA can cause substantial changes in the severity of METH-induced neurotoxicity. DA released into the synapse by METH is very likely the source of downstream reactants that provoke microglial activation and the ensuing damage to DA nerve endings.

Methamphetamine induces striatal neurokinin-1 receptor endocytosis primarily in somatostatin/NPY/NOS interneurons and the role of dopamine receptors in mice.

PubMed

Wang, Jing; Angulo, Jesus A

2011-04-01

Methamphetamine (METH) is a psychostimulant that induces long-term deficits of dopamine terminal markers and apoptotic cell death in the striatum. Our laboratory demonstrated that pharmacological blockade of the neurokinin-1 receptor attenuated the METH-induced damage to the striatal dopamine terminals and the apoptotic cell death of some striatal neurons. Here, we used histological methods to assess the effect of METH on neurokinin-1 receptor trafficking in the striatum as an indirect index of signaling by the neuropeptide substance P (natural ligand for this receptor). Male mice received a single injection of METH (30 mg/kg, i.p.) and were sacrificed 30 min later. Immunohistofluorescence confocal microscopy confirmed that the neurokinin-1 receptor is located on cholinergic and somatostatin interneurons of the striatum. METH induced the trafficking of the neurokinin-1 receptor from the membrane into cytoplasmic endosomes primarily in the somatostatin/NPY/NOS interneurons, and this phenomenon was attenuated by antagonists of the dopamine D1 (SCH-23390), D2 (raclopride), or neurokinin-1 (WIN-51,708) receptors. These data demonstrate that METH induces the trafficking of the striatal neurokinin-1 receptors principally in the somatostatin/NPY/NOS interneurons and that this phenomenon is dependent on the activity of dopamine D1 and D2 receptors. Copyright © 2010 Wiley-Liss, Inc.

Muscular innervation of the proximal duodenum of the guinea pig.

PubMed

Iino, S

2000-10-01

We investigated the muscular structure and innervation of the gastroduodenal junction in the guinea pig. In the gastroduodenal junction, the innermost layer of the circular muscle contained numerous nerve fibers and terminals. Since this nerve network continued onto the deep muscular plexus (DMP) of the duodenum, we surmised that the numerous nerve fibers in the gastroduodenal junction were specialized DMP in the most proximal part of the duodenum. The innermost layer containing many nerve fibers was about 1,000 microm in length and 100 microm in thickness in the proximal duodenum. This layer contained numerous connective tissue fibers composed of collagen and elastic fibers. Five to 30 smooth muscle cells lay in contact with each other and were surrounded by fine connective tissue. The nerve fibers in the proximal duodenum contained nerve terminals immunoreactive for choline acetyltransferase, dynorphin, enkephalin, galanin, gastrin-releasing peptide, nitric oxide synthase, substance P, and vasoactive intestinal polypeptide. Adrenergic fibers which contained tyrosine hydroxylase immunoreactivity were rare in the proximal duodenum. In the innermost layer of the proximal duodenum, there were numerous c-Kit immunopositive cells that were in contact with nerve terminals. This study allowed us to clarify the specific architecture of the most proximal portion of the duodenum. The functional significance of the proximal duodenum in relation to the electrical connection and neural cooperation of the musculature between the antrum and the duodenum is also discussed.

The 'glial' glutamate transporter, EAAT2 (Glt-1) accounts for high affinity glutamate uptake into adult rodent nerve endings.

PubMed

Suchak, Sachin K; Baloyianni, Nicoletta V; Perkinton, Michael S; Williams, Robert J; Meldrum, Brian S; Rattray, Marcus

2003-02-01

The excitatory amino acid transporters (EAAT) removes neurotransmitters glutamate and aspartate from the synaptic cleft. Most CNS glutamate uptake is mediated by EAAT2 into glia, though nerve terminals show evidence for uptake, through an unknown transporter. Reverse-transcriptase PCR identified the expression of EAAT1, EAAT2, EAAT3 and EAAT4 mRNAs in primary cultures of mouse cortical or striatal neurones. We have used synaptosomes and glial plasmalemmal vesicles (GPV) from adult mouse and rat CNS to identify the nerve terminal transporter. Western blotting showed detectable levels of the transporters EAAT1 (GLAST) and EAAT2 (Glt-1) in both synaptosomes and GPVs. Uptake of [3H]D-aspartate or [3H]L-glutamate into these preparations revealed sodium-dependent uptake in GPV and synaptosomes which was inhibited by a range of EAAT blockers: dihydrokainate, serine-o-sulfate, l-trans-2,4-pyrrolidine dicarboxylate (PDC) (+/-)-threo-3-methylglutamate and (2S,4R )-4-methylglutamate. The IC50 values found for these compounds suggested functional expression of the 'glial, transporter, EAAT2 in nerve terminals. Additionally blockade of the majority EAAT2 uptake sites with 100 micro m dihydrokainate, failed to unmask any functional non-EAAT2 uptake sites. The data presented in this study indicate that EAAT2 is the predominant nerve terminal glutamate transporter in the adult rodent CNS.

Palisade endings are present in canine extraocular muscles and have a cholinergic phenotype.

PubMed

Rungaldier, Stefanie; Pomikal, Christine; Streicher, Johannes; Blumer, Roland

2009-11-20

Classical proprioceptors, like Golgi tendon organs and muscle spindles are absent in the extraocular muscles (EOMs) of most mammals. Instead, a nerve end organ was detected in the EOMs of each species including sheep, cat, rabbit, rat, monkey, and human examined so far: the palisade ending. Until now no clear evidence appeared that palisade endings are also present in canine EOMs. Here, we analyzed dog EOMs by confocal laser scanning microscopy, 3D reconstruction, and transmission electron microscopy. In EOM wholemount preparations stained with antibodies against neurofilament and synaptophysin we could demonstrate typical palisade endings. Nerve fibers coming from the muscle extend into the tendon. There, the nerve fibers turn 180 degrees and return to branch into preterminal axons which establish nerve terminals around a single muscle fiber tip. Fine structural analysis revealed that each palisade ending in dog EOMs establish nerve terminals on the tendon. In some palisade endings we found nerve terminals contacting the muscle fiber as well. Such neuromuscular contacts have a basal lamina in the synaptic cleft. By using an antibody against choline acetyltransferase (ChAT) we proved that canine palisade endings are ChAT-immunoreactive. This study shows that palisade endings are present in canine EOMs. In line with prior findings in cat and monkey, palisade endings in dog have a cholinergic phenotype.

Pituitary adenylyl cyclase-activating polypeptide (PACAP) and its receptor (PAC1-R) are positioned to modulate afferent signaling in the cochlea.

PubMed

Drescher, M J; Drescher, D G; Khan, K M; Hatfield, J S; Ramakrishnan, N A; Abu-Hamdan, M D; Lemonnier, L A

2006-09-29

Pituitary adenylyl cyclase-activating polypeptide (PACAP), via its specific receptor pituitary adenylyl cyclase-activating polypeptide receptor 1 (PAC1-R), is known to have roles in neuromodulation and neuroprotection associated with glutamatergic and cholinergic neurotransmission, which, respectively, are believed to form the primary basis for afferent and efferent signaling in the organ of Corti. Previously, we identified transcripts for PACAP preprotein and multiple splice variants of its receptor, PAC1-R, in microdissected cochlear subfractions. In the present work, neural localizations of PACAP and PAC1-R within the organ of Corti and spiral ganglion were examined, defining sites of PACAP action. Immunolocalization of PACAP and PAC1-R in the organ of Corti and spiral ganglion was compared with immunolocalization of choline acetyltransferase (ChAT) and synaptophysin as efferent neuronal markers, and glutamate receptor 2/3 (GluR2/3) and neurofilament 200 as afferent neuronal markers, for each of the three cochlear turns. Brightfield microscopy giving morphological detail for individual immunolocalizations was followed by immunofluorescence detection of co-localizations. PACAP was found to be co-localized with ChAT in nerve fibers of the intraganglionic spiral bundle and beneath the inner and outer hair cells within the organ of Corti. Further, evidence was obtained that PACAP is expressed in type I afferent axons leaving the spiral ganglion en route to the auditory nerve, potentially serving as a neuromodulator in axonal terminals. In contrast to the efferent localization of PACAP within the organ of Corti, PAC1-R immunoreactivity was co-localized with afferent dendritic neuronal marker GluR2/3 in nerve fibers passing beneath and lateral to the inner hair cell and in fibers at supranuclear and basal sites on outer hair cells. Given the known association of PACAP with catecholaminergic neurotransmission in sympathoadrenal function, we also re-examined the issue of whether the organ of Corti receives adrenergic innervation. We now demonstrate the existence of nerve fibers within the organ of Corti which are immunoreactive for the adrenergic marker dopamine beta-hydroxylase (DBH). DBH immunoreactivity was particularly prominent in nerve fibers both at the base and near the cuticular plate of outer hair cells of the apical turn, extending to the non-sensory Hensen's cell region. Evidence was obtained for limited co-localization of DBH with PAC1-R and PACAP. In the process of this investigation, we obtained evidence that efferent and afferent nerve fibers, in addition to adrenergic nerve fibers, are present at supranuclear sites on outer hair cells and distributed within the non-sensory epithelium of the apical cochlear turn for rat, based upon immunoreactivity for the corresponding neuronal markers. Overall, PACAP is hypothesized to act within the organ of Corti as an efferent neuromodulator of afferent signaling via PAC1-R that is present on type I afferent dendrites, in position to afford protection from excitotoxicity. Additionally, PACAP/PAC1-R may modulate secretion of catecholamines from adrenergic terminals within the organ of Corti.

Examining the Complex Regulation and Drug-Induced Plasticity of Dopamine Release and Uptake Using Voltammetry in Brain Slices

PubMed Central

2013-01-01

Fast scan cyclic voltammetry in brain slices (slice voltammetry) has been used over the last several decades to increase substantially our understanding of the complex local regulation of dopamine release and uptake in the striatum. This technique is routinely used for the study of changes that occur in the dopamine system associated with various disease states and pharmacological treatments, and to study mechanisms of local circuitry regulation of dopamine terminal function. In the context of this Review, we compare the relative advantages of voltammetry using striatal slice preparations versus in vivo preparations, and highlight recent advances in our understanding of dopamine release and uptake in the striatum specifically from studies that use slice voltammetry in drug-naïve animals and animals with a history of psychostimulant self-administration. PMID:23581570

Computational Systems Analysis of Dopamine Metabolism

PubMed Central

Qi, Zhen; Miller, Gary W.; Voit, Eberhard O.

2008-01-01

A prominent feature of Parkinson's disease (PD) is the loss of dopamine in the striatum, and many therapeutic interventions for the disease are aimed at restoring dopamine signaling. Dopamine signaling includes the synthesis, storage, release, and recycling of dopamine in the presynaptic terminal and activation of pre- and post-synaptic receptors and various downstream signaling cascades. As an aid that might facilitate our understanding of dopamine dynamics in the pathogenesis and treatment in PD, we have begun to merge currently available information and expert knowledge regarding presynaptic dopamine homeostasis into a computational model, following the guidelines of biochemical systems theory. After subjecting our model to mathematical diagnosis and analysis, we made direct comparisons between model predictions and experimental observations and found that the model exhibited a high degree of predictive capacity with respect to genetic and pharmacological changes in gene expression or function. Our results suggest potential approaches to restoring the dopamine imbalance and the associated generation of oxidative stress. While the proposed model of dopamine metabolism is preliminary, future extensions and refinements may eventually serve as an in silico platform for prescreening potential therapeutics, identifying immediate side effects, screening for biomarkers, and assessing the impact of risk factors of the disease. PMID:18568086

Control of extracellular dopamine at dendrite and axon terminals

PubMed Central

Ford, Christopher P.; Gantz, Stephanie C.; Phillips, Paul E. M.; Williams, John T.

2010-01-01

Midbrain dopamine neurons release dopamine from both axons and dendrites. The mechanism underlying release at these different sites has been proposed to differ. This study used electrochemical and electrophysiological methods to compare the time course and calcium-dependence of somatodendritc dopamine release in the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) to that of axonal dopamine release in the dorsal striatum. The amount of dopamine released in the striatum was ~20 fold greater than in cell body regions of the VTA or SNc. However the calcium dependence and time to peak of the dopamine transients were similar. These results illustrate an unexpected overall similarity in the mechanisms of dopamine release in the striatum and cell body regions. To examine how diffusion regulates the time course of dopamine following release, dextran was added to the extracellular solution to slow diffusion. In the VTA, dextran slowed the rate of rise and fall of the extracellular dopamine transient as measured by fast-scan cyclic voltammetry (FSCV) yet did not alter the kinetics of the dopamine dependent inhibitory post-synaptic current (IPSC). Dextran failed to significantly alter the time course of the rise and fall of the dopamine transient in the striatum suggesting a more influential role for reuptake in the striatum. The conclusion is that the time course of dopamine within the extracellular space of the VTA is dependent on both diffusion and reuptake, whereas the activation of D2-receptors on dopamine neurons is primarily limited by reuptake. PMID:20484639

Acute fasting increases somatodendritic dopamine release in the ventral tegmental area

PubMed Central

2015-01-01

Fasting and food restriction alter the activity of the mesolimbic dopamine system to affect multiple reward-related behaviors. Food restriction decreases baseline dopamine levels in efferent target sites and enhances dopamine release in response to rewards such as food and drugs. In addition to releasing dopamine from axon terminals, dopamine neurons in the ventral tegmental area (VTA) also release dopamine from their soma and dendrites, and this somatodendritic dopamine release acts as an autoinhibitory signal to inhibit neighboring VTA dopamine neurons. It is unknown whether acute fasting also affects dopamine release, including the local inhibitory somatodendritic dopamine release in the VTA. In these studies, I have tested whether fasting affects the inhibitory somatodendritic dopamine release within the VTA by examining whether an acute 24-h fast affects the inhibitory postsynaptic current mediated by evoked somatodendritic dopamine release (D2R IPSC). Fasting increased the contribution of the first action potential to the overall D2R IPSC and increased the ratio of repeated D2R IPSCs evoked at short intervals. Fasting also reduced the effect of forskolin on the D2R IPSC and led to a significantly bigger decrease in the D2R IPSC in low extracellular calcium. Finally, fasting resulted in an increase in the D2R IPSCs when a more physiologically relevant train of D2R IPSCs was used. Taken together, these results indicate that fasting caused a change in the properties of somatodendritic dopamine release, possibly by increasing dopamine release, and that this increased release can be sustained under conditions where dopamine neurons are highly active. PMID:26084913

Membrane transporters as mediators of synaptic dopamine dynamics: implications for disease

PubMed Central

Lohr, Kelly M.; Masoud, Shababa T.; Salahpour, Ali; Miller, Gary W.

2016-01-01

Dopamine was first identified as a neurotransmitter localized to the midbrain over 50 years ago. The dopamine transporter (DAT; SLC6A3) and the vesicular monoamine transporter 2 (VMAT2; SLC18A2) are two regulators of dopamine homeostasis in the presynaptic neuron. DAT transports dopamine from the extracellular space into the cytosol of the presynaptic terminal. VMAT2 then packages this cytosolic dopamine into vesicular compartments for subsequent release upon neurotransmission. Thus, DAT and VMAT2 act in concert to move transmitter efficiently throughout the neuron. The accumulation of dopamine in the neuronal cytosol can trigger oxidative stress and neurotoxicity, suggesting that the proper compartmentalization of dopamine is critical for neuron function and risk of disease. For decades, studies have examined the effects of reduced transporter function in mice (e.g. DAT-KO, VMAT2-KO, VMAT2-deficient). However, we have only recently been able to assess the effects of elevated transporter expression using BAC transgenic methods (DAT-tg, VMAT2-HI mice). Complemented with in vitro work and neurochemical techniques to assess dopamine compartmentalization, a new focus on the importance of transporter proteins as both models of human disease and potential drug targets has emerged. Here we review the importance of DAT and VMAT2 function in the delicate balance of neuronal dopamine. PMID:27520881

Triazines facilitate neurotransmitter release of synaptic terminals located in hearts of frog (Rana ridibunda) and honeybee (Apis mellifera) and in the ventral nerve cord of a beetle (Tenebrio molitor).

PubMed

Papaefthimiou, Chrisovalantis; Zafeiridou, Georgia; Topoglidi, Aglaia; Chaleplis, George; Zografou, Stella; Theophilidis, George

2003-07-01

Three triazine herbicides, atrazine, simazine and metribuzine, and some of their major metabolites (cyanuric acid and 6-azauracil) were investigated for their action on synaptic terminals using three different isolated tissue preparations from the atria of the frog, Rana ridibunda, the heart of the honeybee, Apis mellifera macedonica, and the ventral nerve cord of the beetle, Tenebrio molitor. The results indicate that triazines facilitate the release of neurotransmitters from nerve terminals, as already reported for the mammalian central nervous system. The no observed effect concentration, the maximum concentration of the herbicide diluted in the saline that has no effect on the physiological properties of the isolated tissue, was estimated for each individual preparation. According to their relative potency, the three triazines tested can be ranked as follows: atrazine (cyanuric acid), simazine>metribuzine (6-azauracil). The action of these compounds on the cholinergic (amphibians, insects), adrenergic (amphibian) and octopaminergic (insects) synaptic terminals is discussed.

Optogenetic versus electrical stimulation of dopamine terminals in the nucleus accumbens reveals local modulation of presynaptic release

PubMed Central

Melchior, James R.; Ferris, Mark J.; Stuber, Garret D.; Riddle, David R.; Jones, Sara R.

2015-01-01

The nucleus accumbens is highly heterogeneous, integrating regionally distinct afferent projections and accumbal interneurons, resulting in diverse local microenvironments. Dopamine (DA) neuron terminals similarly express a heterogeneous collection of terminal receptors that modulate DA signaling. Cyclic voltammetry is often used to probe DA terminal dynamics in brain slice preparations; however, this method traditionally requires electrical stimulation to induce DA release. Electrical stimulation excites all of the neuronal processes in the stimulation field, potentially introducing simultaneous, multi-synaptic modulation of DA terminal release. We used optogenetics to selectively stimulate DA terminals and used voltammetry to compare DA responses from electrical and optical stimulation of the same area of tissue around a recording electrode. We found that with multiple pulse stimulation trains, optically stimulated DA release increasingly exceeded that of electrical stimulation. Furthermore, electrical stimulation produced inhibition of DA release across longer duration stimulations. The GABAB antagonist, CGP 55845, increased electrically stimulated DA release significantly more than light stimulated release. The nicotinic acetylcholine receptor antagonist, dihydro-β-erythroidine hydrobromide, inhibited single pulse electrically stimulated DA release while having no effect on optically stimulated DA release. Our results demonstrate that electrical stimulation introduces local multi-synaptic modulation of DA release that is absent with optogenetically targeted stimulation. PMID:26011081

Extralaryngeal division of the recurrent laryngeal nerve: a new description for the inferior laryngeal nerve.

PubMed

Yalcin, Bulent; Tunali, Selcuk; Ozan, Hasan

2008-05-01

Extralaryngeal division of the recurrent laryngeal nerve was contradictory in the literature. We aimed to investigate extralaryngeal division of the nerve, and also propose a new description for the inferior laryngeal nerve. Sixty specimens (120 sides) were examined for this project, including 41 men and 19 women cadavers between the ages of 40 and 89 years at death. In one right side, terminal segment of the nerve gave off many small branches surrounding the inferior thyroid artery then reaching the larynx, trachea, thyroid gland and esophagus. In eight sides, terminal segment of the nerve had no extralaryngeal division and entered the larynx as a single trunk. In 110 sides, the nerve had extralaryngeal division. One hundred and three nerves had two laryngeal and one to three extralaryngeal branches. Two types were described in this group. In type I (66 nerves), both branches arose from the same level of nerve. Type I had two subtypes: type Ia, the origin of the branches was just below the inferior constrictor muscle; type Ib, the origin of the branches was 15-35 mm below the muscle. In type II (37 nerves), the laryngeal branches arose just 3-5 mm above the extralaryngeal branches. We observed that the laryngeal and extralaryngeal branches arose generally from the same point of the recurrent laryngeal nerve. The inferior laryngeal nerve is thus very short, or even nonexistent. Therefore, we suggest that if the term "superior laryngeal nerve" is a given, standard, and accepted term, then the term "inferior laryngeal nerve" should also be accepted instead of the term "recurrent laryngeal nerve."

Susceptibility of ascending dopamine projections to 6-hydroxydopamine in rats: effect of hypothermia.

PubMed

Grant, R J; Clarke, P B S

2002-01-01

The aims of this study were to determine (1) whether mesolimbic and nigrostriatal DA cell bodies degenerate to different extents after 6-hydroxydopamine (6-OHDA) is administered into their respective terminal fields and (2) whether hypothermia, associated with sodium pentobarbital anesthesia, protects DA neurons from the toxic effects of 6-OHDA. To address these questions, 6-OHDA or vehicle was infused into either the ventral or dorsal striatum or into the medial forebrain bundle, under conditions of brain normothermia or hypothermia. Two weeks post-surgery, tyrosine hydroxylase-positive cell bodies were counted in the ventral tegmental area (VTA) and substantia nigra. In addition, autoradiographic labeling of tyrosine hydroxylase protein and dopamine transporter was quantified in dopamine terminal fields and cell body areas. Overall, DA cell bodies in the VTA were substantially less susceptible than those in the substantia nigra to depletion of dopaminergic markers. Hypothermia provided two types of neuroprotection. The first occurred when 6-OHDA was administered into the dorsal striatum, and was associated with a 30-50% increase in residual dopaminergic markers in the lateral portion of the VTA. The second neuroprotective effect of hypothermia occurred when 6-OHDA was given into the medial forebrain bundle. This was associated with a 200-300% increase in residual dopaminergic markers in the mesolimbic and nigrostriatal terminal fields; no significant protection occurred in the cell body regions.Collectively, these findings show that (1) the dopaminergic somata in the substantia nigra are more susceptible than those in the VTA to 6-OHDA-induced denervation, and (2) hypothermia can provide anatomically selective neuroprotection within the substantia nigra-VTA cell population. The continued survival of mesolimbic dopamine cell bodies after a 6-OHDA lesion may have functional implications relating to drugs of abuse, as somatodendritic release of dopamine in the VTA has been shown to play a role in the effectiveness of cocaine reward.

Surgical Approaches to Facial Nerve Deficits

PubMed Central

Birgfeld, Craig; Neligan, Peter

2011-01-01

The facial nerve is one of the most commonly injured cranial nerves. Once injured, the effects on form, function, and psyche are profound. We review the anatomy of the facial nerve from the brain stem to its terminal branches. We also discuss the physical exam findings of facial nerve injury at various levels. Finally, we describe various reconstructive options for reanimating the face and restoring both form and function. PMID:22451822

Synaptic and paracrine mechanisms at carotid body arterial chemoreceptors

PubMed Central

Nurse, Colin A

2014-01-01

Mammalian carotid bodies are the main peripheral arterial chemoreceptors, strategically located at the bifurcation of the common carotid artery. When stimulated these receptors initiate compensatory respiratory and cardiovascular reflexes to maintain homeostasis. Thus, in response to low oxygen (hypoxia) or increased CO2/H+ (acid hypercapnia), chemoreceptor type I cells depolarize and release excitatory neurotransmitters, such as ATP, which stimulate postsynaptic P2X2/3 receptors on afferent nerve terminals. The afferent discharge is shaped by autocrine and paracrine mechanisms involving both excitatory and inhibitory neuromodulators such as adenosine, serotonin (5-HT), GABA and dopamine. Recent evidence suggests that paracrine activation of P2Y2 receptors on adjacent glia-like type II cells may help boost the ATP signal via the opening of pannexin-1 channels. The presence of an inhibitory efferent innervation, mediated by release of nitric oxide, provides additional control of the afferent discharge. The broad array of neuromodulators and their receptors appears to endow the carotid body with a remarkable plasticity, most apparent during natural and pathophysiological conditions associated with chronic sustained and intermittent hypoxia. PMID:24665097

The nature of catecholamine-containing neurons in the enteric nervous system in relationship with organogenesis, normal human anatomy and neurodegeneration.

PubMed

Natale, G; Ryskalin, L; Busceti, C L; Biagioni, F; Fornai, F

2017-09-01

The gastrointestinal tract is provided with extrinsic and intrinsic innervation. The extrinsic innervation includes the classic vagal parasympathetic and sympathetic components, with afferent sensitive and efferent secretomotor fibers. The intrinsic innervations is represented by the enteric nervous system (ENS), which is recognized as a complex neural network controlling a variety of cell populations, including smooth muscle cells, mucosal secretory cells, endocrine cells, microvasculature, immune and inflammatory cells. This is finalized to regulate gastrointestinal secretion, absorption and motility. In particular, this network is organized in several plexuses each one providing quite autonomous control of gastrointestinal functions (hence the definition of "second brain"). The similarity between ENS and CNS is further substantiated by the presence of local sensitive pseudo- unipolar ganglionic neurons with both peripheral and central branching which terminate in the enteric wall. A large variety of neurons and neurotransmitters takes part in the ENS. However, the nature of these neurons and their role in the regulation of gastrointestinal functions is debatable. In particular, the available literature reporting the specific nature of catecholamine- containing neurons provides conflicting evidence. This is critical both for understanding the specific role of each catecholamine in the gut and, mostly, to characterize specifically the enteric neuropathology occurring in a variety of diseases. An emphasis is posed on neurodegenerative disorders, such as Parkinson's disease, which is associated with the loss of catecholamine neurons. In this respect, the recognition of the nature of such neurons within the ENS would contribute to elucidate the pathological mechanisms which produce both CNS and ENS degeneration and to achieve more effective therapeutic approaches. Despite a great emphasis is posed on the role of noradrenaline to regulate enteric activities only a few reports are available on the anatomy and physiology of enteric dopamine neurons. Remarkably, this review limits the presence of enteric noradrenaline (and adrenaline) only within extrinsic sympathetic nerve terminals. This is based on careful morphological studies showing that the only catecholamine-containing neurons within ENS would be dopaminergic. This means that enteric pathology of catecholamine neurons should be conceived as axon pathology for noradrenaline neurons and whole cell pathology for dopamine neurons which would be the sole catecholamine cell within intrinsic circuitries affecting gut motility and secretions.The gastrointestinal tract is provided with extrinsic and intrinsic innervation. The extrinsic innervation includes the classic vagal parasympathetic and sympathetic components, with afferent sensitive and efferent secretomotor fibers. The intrinsic innervations is represented by the enteric nervous system (ENS), which is recognized as a complex neural network  controlling a variety of cell populations, including smooth muscle cells, mucosal secretory cells, endocrine cells, microvasculature, immune and inflammatory cells. This is finalized to regulate gastrointestinal secretion, absorption and motility. In particular, this network is organized in several plexuses each one providing quite autonomous control of gastrointestinal functions (hence the definition of "second brain"). The similarity between ENS and CNS is further substantiated by the presence of local sensitive pseudounipolar ganglionic neurons with both peripheral and central branching which terminate in the enteric wall. A large variety of neurons and neurotransmitters takes part in the ENS. However, the nature of these neurons and their role in the regulation of gastrointestinal functions is debatable. In particular, the available literature reporting the specific nature of catecholamine-containing neurons provides conflicting evidence. This is critical both for understanding the specific role of each catecholamine in the gut and, mostly, to characterize specifically the enteric neuropathology occurring in a variety of diseases. An emphasis is posed on neurodegenerative disorders, such as including Parkinson's disease, which is associated with the loss of catecholamine neurons. In this respect, the recognition of the nature of such neurons within the ENS would contribute to elucidate the pathological mechanisms which produce both CNS and ENS degeneration and to achieve more effective therapeutic approaches. Despite a great emphasis is posed on the role of noradrenaline to regulate enteric activities only a few reports are available on the anatomy and physiology of enteric dopamine neurons. Remarkably, this review limits the presence of enteric noradrenaline (and adrenaline) only within extrinsic sympathetic nerve terminals. This is based on careful morphological studies showing that the only catecholamine-containing neurons within ENS would be dopaminergic. This means that enteric pathology of catecholamine neurons should be conceived as axon pathology for noradrenaline neurons and whole cell pathology for dopamine neurons which would be the sole catecholamine cell within intrinsic circuitries affecting gut motility and secretions.

Intranasal Delivery of pGDNF Nanoparticles for Parkinson's Disease

NASA Astrophysics Data System (ADS)

Harmon, Brendan Trevor

Parkinson's disease (PD) is a progressive neurodegenerative disorder that primarily affects the dopaminergic A9 nigrostriatal tract. For dopamine neurons specifically, glial cell-derived neurotrophic factor (GDNF) has been shown to promote their survival and proliferation both in culture and in vivo. GDNF has also proven to be neuroprotective and restorative in various animal models of PD and some human clinical trials. However, its delivery to the brain has required invasive surgical routes which are not clinically practical for many patients. The main objective of this project was to test intranasal delivery to the brain of a nanoparticle vector incorporating an expression plasmid for GDNF (pGDNF). The intranasal route circumvents the blood-brain barrier, allowing larger sized vectors into the central nervous system while avoiding peripheral distribution. This approach would provide a renewable source of GDNF within the target areas of the brain, the striatum and the substantia nigra (SN) without the need for surgical injections or frequent re-dosing. A PEGylated polylysine compacted plasmid nanoparticle vector (PEG-CK30), developed by Copernicus Therapeutics, Inc., has been shown to transfect neurons and glial cells in vivo while lacking the safety issues present with other vectors. The first goal of this work was to determine if these PEG-CK30 compacted plasmid nanoparticles can successfully transfect cells and express the reporter protein, enhanced green fluorescent protein (eGFP) in the rat brain after intranasal administration. Initial in vivo experiments utilized the expression plasmid pCG, expressing eGFP under the fast-acting cytomegalovirus (CMV) promoter. Intranasal administration of pCG nanoparticles resulted in evidence of transfection of brain cells, as shown both qualitatively, by GFP-immunohistochemistry, and quantitatively, by GFP-ELISA. Expression was detected throughout the rat brain two days post-administration. Following the proof-of-principle study with pCG, a new plasmid was created by Copernicus Therapeutics, Inc. to better mimic their long-lasting pGDNF plasmid while providing both GDNF as well as the reporter function of eGFP. This eGFP-GDNF plasmid was used to monitor expression and cell-types transfected. This expression plasmid, called pUGG, was first characterized in vitro to verify protein expression. Transfection experiments in SHEP-1 neuroblastoma cells, ventral midbrain cultures, and N27 dopaminergic cells all demonstrated that pUGG expressed bioactive eGFP and GDNF. However, cleavage of the two proteins did not occur and the expressed protein emerged as a fusion construct which was not detectable by GDNF-ELISA, although it was detected by GFP-ELISA. The next goal was to determine if pUGG was able to transfect cells in vivo in rat brain. Direct striatal injection of pUGG nanoparticles showed significant eGFP expression at the site of injection both 7 and 14 days post-administration with no difference in eGFP expression between the two time-points. GFP-immunohistochemistry at the striatal injection site revealed expression of eGFP-positive cells as well as evidence of GDNF's bioactivity as indicated by neurite outgrowth. Moving forward, we administered pUGG nanoparticles intranasally to rats and found significant expression seven days later throughout the brain, with highest levels in the forebrain areas (olfactory bulb and frontal cortex). Significant expression was also seen along the rostral-caudal axis of the brain compared with naked pUGG plasmid. The final goal of this work was to examine whether intranasal pGDNF pre-treatment could generate sufficient GDNF to protect SN dopamine neurons after a unilateral 6-hydroxydopmaine (6-OHDA) lesion, a common animal model for PD. Copernicus' pGDNF plasmid was utilized for the neuroprotection experiments to avoid possible confounds due to the GFP fusion produced by pUGG. Tyrosine hydroxylase-immunostaining density was used as a marker for dopamine neurons in the SN and their nerve terminals in the striatum. Dopamine cell counts were also performed in the SN. Intranasal delivery of pGDNF significantly protected dopamine neurons in the rat 6-OHDA model of PD. This was revealed in three ways. First, pGDNF treatments reduced amphetamine-induced circling behavior, suggesting a prevention of dopamine loss on the 6-OHDA-lesioned side. Second, pGDNF increased TH staining density and dopamine cell counts in the SN on the 6-OHDA-lesioned side. This result was direct evidence of neuroprotection of dopamine cell bodies. Third, pGDNF increased TH staining density in the striatum on the 6-OHDA-lesioned side. This result was direct evidence of protection of dopaminergic nerve terminals. Intranasal pGDNF nanoparticles provided greater neuroprotection than naked pGDNF for all measures. This result was consistent with our previous findings that pGDNF nanoparticles produce more GDNF in brain than the naked plasmid. Collectively, these results demonstrate that intranasal delivery of Copernicus' pGDNF nanoparticles has great clinical potential as a new, non-invasive and non-viral gene therapy approach for early stage Parkinson's disease. By promoting recovery of damaged neurons and preventing further cell loss, symptoms may be reversed and disease progression may be stopped.

Occlusion of carotid artery and hypergravity loading of animals caused similar effects on L-[14C]glutamate uptake in rat brain nerve terminals

NASA Astrophysics Data System (ADS)

Borisova, Tatiana; Sivko, Roman; Krisanova, Natalia

Changes in sodium-dependent L-[14C]glutamate uptake in rat brain nerve terminals was com-paratively analysed after hypergravity loading of animals (centrifugation of rats in special con-tainers at 10 G for 1 hour) and unilateral occlusion of carotid artery (20 min). The initial velocity of L-[14C]glutamate uptake was decreased from 2.5 ± 0.2 nmol x min-1 x mg-1 of proteins to 2.05 ± 0.1 nmol x min-1 x mg-1 of proteins after hypergravity and after occlusion -up to 2.25 ± 0.1 nmol x min-1 x mg-1 of proteins. Recently, we have shown that a decrease in L-[14C]glutamate uptake was at least partially caused by the redaction in the membrane potential of nerve terminals and the proton gradient of synaptic vesicles. These parameters were analysed after unilateral occlusion of carotid artery, where one brain hemisphere was used as a control, whereas the second one as subjected to ischemic/hypoxic conditions. Similarly with hypergravity, we revealed a decrease in the membrane potential of nerve terminals by ˜ 10 % and a reduction of the proton gradient of synaptic vesicles by ˜ 5 % after occlusion of carotid artery. Thus, a decrease in the activity of glutamate transporters after hypergrav-ity and unilateral occlusion of carotid artery was at least partially caused by changes in the membrane potential of nerve terminals and the proton gradient of synaptic vesicles. This fact may be considered in support of the suggestion that ischemia/hypoxia was a main unspecific stressor, which caused the alterations in glutamatergic neurotransmission under conditions of hypergravity.

Maintenance of Mouse Gustatory Terminal Field Organization Is Disrupted following Selective Removal of Peripheral Sodium Salt Taste Activity at Adulthood

PubMed Central

Sun, Chengsan

2017-01-01

Neural activity plays a critical role in the development of central circuits in sensory systems. However, the maintenance of these circuits at adulthood is usually not dependent on sensory-elicited neural activity. Recent work in the mouse gustatory system showed that selectively deleting the primary transduction channel for sodium taste, the epithelial sodium channel (ENaC), throughout development dramatically impacted the organization of the central terminal fields of three nerves that carry taste information to the nucleus of the solitary tract. More specifically, deleting ENaCs during development prevented the normal maturation of the fields. The present study was designed to extend these findings by testing the hypothesis that the loss of sodium taste activity impacts the maintenance of the normal adult terminal field organization in male and female mice. To do this, we used an inducible Cre-dependent genetic recombination strategy to delete ENaC function after terminal field maturation occurred. We found that removal of sodium taste neural activity at adulthood resulted in significant reorganization of mature gustatory afferent terminal fields in the nucleus of the solitary tract. Specifically, the chorda tympani and greater superficial petrosal nerve terminal fields were 1.4× and 1.6× larger than age-matched controls, respectively. By contrast, the glossopharyngeal nerve, which is not highly sensitive to sodium taste stimulation, did not undergo terminal field reorganization. These surprising results suggest that gustatory nerve terminal fields remain plastic well into adulthood, which likely impacts central coding of taste information and taste-related behaviors with altered taste experience. SIGNIFICANCE STATEMENT Neural activity plays a major role in the development of sensory circuits in the mammalian brain. However, the importance of sensory-driven activity in maintaining these circuits at adulthood, especially in subcortical structures, appears to be much less. Here, we tested whether the loss of sodium taste activity in adult mice impacts the maintenance of how taste nerves project to the first central relay. We found that specific loss of sodium-elicited taste activity at adulthood produced dramatic and selective reorganization of terminal fields in the brainstem. This demonstrates, for the first time, that taste-elicited activity is necessary for the normal maintenance of central gustatory circuits at adulthood and highlights a level of plasticity not seen in other sensory system subcortical circuits. PMID:28676575

Optogenetically-induced tonic dopamine release from VTA-nucleus accumbens projections inhibits reward consummatory behaviors

PubMed Central

Mikhailova, Maria A.; Bass, Caroline E.; Grinevich, Valentina P.; Chappell, Ann M.; Deal, Alex L.; Bonin, Keith D.; Weiner, Jeff L.; Gainetdinov, Raul R.; Budygin, Evgeny A.

2016-01-01

Recent optogenetic studies demonstrated that phasic dopamine release in the nucleus accumbens may play a causal role in multiple aspects of natural and drug reward-related behaviors. The role of tonic dopamine release in reward consummatory behavior remains unclear. The current study used a combinatorial viral-mediated gene delivery approach to express ChR2 on mesolimbic dopamine neurons in rats. We used optical activation of this dopamine circuit to mimic tonic dopamine release in the nucleus accumbens and to explore the causal relationship between this form of dopamine signaling within the ventral tegmental area (VTA)-nucleus accumbens projection and consumption of a natural reward. Using a two bottle choice paradigm (sucrose vs. water), the experiments revealed that tonic optogenetic stimulation of mesolimbic dopamine transmission significantly decreased reward consummatory behaviors. Specifically, there was a significant decrease in the number of bouts, licks and amount of sucrose obtained during the drinking session. Notably, activation of VTA dopamine cell bodies or dopamine terminals in the nucleus accumbens resulted in identical behavioral consequences. No changes in the water intake were evident under the same experimental conditions. Collectively, these data demonstrate that tonic optogenetic stimulation of VTA-nucleus accumbens dopamine release is sufficient to inhibit reward consummatory behavior, possibly by preventing this circuit from engaging in phasic activity that is thought to be essential for reward-based behaviors. PMID:27421228

Pathomechanisms of Dopamine Dysregulation in DYT1 Dystonia: Targets for Therapeutics

DTIC Science & Technology

2016-10-01

DA release in DYT1(ΔE) knockin mice by assessing VMAT2 function, vesicle utilization, the ultrastructure of DA terminals, and D2 DA...in slice, the ultrastructure of DA terminals, D2 DA autoreceptor function nicotinic AChR (nAChR) heteroreceptors function. 2) To determine the

Isolation of Synaptosomes, Synaptic Plasma Membranes, and Synaptic Junctional Complexes.

PubMed

Michaelis, Mary L; Jiang, Lei; Michaelis, Elias K

2017-01-01

Isolation of synaptic nerve terminals or synaptosomes provides an opportunity to study the process of neurotransmission at many levels and with a variety of approaches. For example, structural features of the synaptic terminals and the organelles within them, such as synaptic vesicles and mitochondria, have been elucidated with electron microscopy. The postsynaptic membranes are joined to the presynaptic "active zone" of transmitter release through cell adhesion molecules and remain attached throughout the isolation of synaptosomes. These "post synaptic densities" or "PSDs" contain the receptors for the transmitters released from the nerve terminals and can easily be seen with electron microscopy. Biochemical and cell biological studies with synaptosomes have revealed which proteins and lipids are most actively involved in synaptic release of neurotransmitters. The functional properties of the nerve terminals, such as responses to depolarization and the uptake or release of signaling molecules, have also been characterized through the use of fluorescent dyes, tagged transmitters, and transporter substrates. In addition, isolated synaptosomes can serve as the starting material for the isolation of relatively pure synaptic plasma membranes (SPMs) that are devoid of organelles from the internal environment of the nerve terminal, such as mitochondria and synaptic vesicles. The isolated SPMs can reseal and form vesicular structures in which transport of ions such as sodium and calcium, as well as solutes such as neurotransmitters can be studied. The PSDs also remain associated with the presynaptic membranes during isolation of SPM fractions, making it possible to isolate the synaptic junctional complexes (SJCs) devoid of the rest of the plasma membranes of the nerve terminals and postsynaptic membrane components. Isolated SJCs can be used to identify the proteins that constitute this highly specialized region of neurons. In this chapter, we describe the steps involved in isolating synaptosomes, SPMs, and SJCs from brain so that these preparations can be used with new technological advances to address many as yet unanswered questions about the synapse and its remarkable activities in neuronal cell communication.

Muscarinic acetylcholine receptor subtype expression in avian vestibular hair cells, nerve terminals and ganglion cells.

PubMed

Li, G Q; Kevetter, G A; Leonard, R B; Prusak, D J; Wood, T G; Correia, M J

2007-04-25

Muscarinic acetylcholine receptors (mAChRs) are widely expressed in the CNS and peripheral nervous system and play an important role in modulating the cell activity and function. We have shown that the cholinergic agonist carbachol reduces the pigeon's inwardly rectifying potassium channel (pKir2.1) ionic currents in native vestibular hair cells. We have cloned and sequenced pigeon mAChR subtypes M2-M5 and we have studied the expression of all five mAChR subtypes (M1-M5) in the pigeon vestibular end organs (semicircular canal ampullary cristae and utricular maculae), vestibular nerve fibers and the vestibular (Scarpa's) ganglion using tissue immunohistochemistry (IH), dissociated single cell immunocytochemistry (IC) and Western blotting (WB). We found that vestibular hair cells, nerve fibers and ganglion cells each expressed all five (M1-M5) mAChR subtypes. Two of the three odd-numbered mAChRs (M1, M5) were present on the hair cell cilia, supporting cells and nerve terminals. And all three odd numbered mAChRs (M1, M3 and M5) were expressed on cuticular plates, myelin sheaths and Schwann cells. Even-numbered mAChRs were seen on the nerve terminals. M2 was also shown on the cuticular plates and supporting cells. Vestibular efferent fibers and terminals were not identified in our studies. Results from WB of the dissociated vestibular epithelia, nerve fibers and vestibular ganglia were consistent with the results from IH and IC. Our findings suggest that there is considerable co-expression of the subtypes on the neural elements of the labyrinth. Further electrophysiological and pharmacological studies should delineate the mechanisms of action of muscarinic acetylcholine receptors on structures in the labyrinth.

Peripheral axotomy of the rat mandibular trigeminal nerve leads to an increase in VIP and decrease of other primary afferent neuropeptides in the spinal trigeminal nucleus.

PubMed

Atkinson, M E; Shehab, S A

1986-12-01

In the vasoactive intestinal polypeptide (VIP)-rich lumbosacral spinal cord, VIP increases at the expense of other neuropeptides after primary sensory nerve axotomy. This study was undertaken to ascertain whether similar changes occur in peripherally axotomised cranial sensory nerves. VIP immunoreactivity increased in the terminal region of the mandibular nerve in the trigeminal nucleus caudalis following unilateral section of the sensory root of the mandibular trigeminal nerve at the foramen orale. Other primary afferent neuropeptides (substance P, cholecystokinin and somatostatin) were depleted and fluoride-resistant acid phosphatase activity was abolished in the same circumscribed areas of the nucleus caudalis. The rise in VIP and depletion of other markers began 4 days postoperatively and was maximal by 10 days, these levels remaining unchanged up to 1 year postoperatively. VIP-immunoreactive cell bodies were absent from trigeminal ganglia from the unoperated side but small and medium cells stained intensely in the ganglia of the operated side after axotomy. These observations indicate that increase of VIP in sensory nerve terminals is a general phenomenon occurring in both cranial and spinal sensory terminal areas. The intense VIP immunoreactivity in axotomised trigeminal ganglia suggests that the increased levels of VIP in the nucleus caudalis are of peripheral origin, indicating a change in expression of neuropeptides within primary afferent neurons following peripheral axotomy.

Prevention and Treatment of Noise-Induced Tinnitus. Revision

DTIC Science & Technology

2013-07-01

CTBP2 immunolabeling) for their loss following noise. Sub-Task 1c: Assessment of Auditory Nerve ( VGLUT1 immunolabel) terminals on neurons in Ventral...and Dorsal Cochlear Nucleus (VCN, DCN) for their loss following noise. Sub-Task 1d: Assessment of VGLUT2 , VAT & VGAT immunolabeled terminals in VCN...significant reduction in connections compared to animals without noise exposure. Sub-Task 1c: Assessment of Auditory Nerve ( VGLUT1 immunolabel

Direct evidence for activity-dependent glucose phosphorylation in neurons with implications for the astrocyte-to-neuron lactate shuttle

PubMed Central

Patel, Anant B.; Lai, James C. K.; Chowdhury, Golam M. I.; Hyder, Fahmeed; Rothman, Douglas L.; Shulman, Robert G.; Behar, Kevin L.

2014-01-01

Previous 13C magnetic resonance spectroscopy experiments have shown that over a wide range of neuronal activity, approximately one molecule of glucose is oxidized for every molecule of glutamate released by neurons and recycled through astrocytic glutamine. The measured kinetics were shown to agree with the stoichiometry of a hypothetical astrocyte-to-neuron lactate shuttle model, which predicted negligible functional neuronal uptake of glucose. To test this model, we measured the uptake and phosphorylation of glucose in nerve terminals isolated from rats infused with the glucose analog, 2-fluoro-2-deoxy-d-glucose (FDG) in vivo. The concentrations of phosphorylated FDG (FDG6P), normalized with respect to known neuronal metabolites, were compared in nerve terminals, homogenate, and cortex of anesthetized rats with and without bicuculline-induced seizures. The increase in FDG6P in nerve terminals agreed well with the increase in cortical neuronal glucose oxidation measured previously under the same conditions in vivo, indicating that direct uptake and oxidation of glucose in nerve terminals is substantial under resting and activated conditions. These results suggest that neuronal glucose-derived pyruvate is the major oxidative fuel for activated neurons, not lactate-derived from astrocytes, contradicting predictions of the original astrocyte-to-neuron lactate shuttle model under the range of study conditions. PMID:24706914

Direct evidence for activity-dependent glucose phosphorylation in neurons with implications for the astrocyte-to-neuron lactate shuttle.

PubMed

Patel, Anant B; Lai, James C K; Chowdhury, Golam M I; Hyder, Fahmeed; Rothman, Douglas L; Shulman, Robert G; Behar, Kevin L

2014-04-08

Previous (13)C magnetic resonance spectroscopy experiments have shown that over a wide range of neuronal activity, approximately one molecule of glucose is oxidized for every molecule of glutamate released by neurons and recycled through astrocytic glutamine. The measured kinetics were shown to agree with the stoichiometry of a hypothetical astrocyte-to-neuron lactate shuttle model, which predicted negligible functional neuronal uptake of glucose. To test this model, we measured the uptake and phosphorylation of glucose in nerve terminals isolated from rats infused with the glucose analog, 2-fluoro-2-deoxy-D-glucose (FDG) in vivo. The concentrations of phosphorylated FDG (FDG6P), normalized with respect to known neuronal metabolites, were compared in nerve terminals, homogenate, and cortex of anesthetized rats with and without bicuculline-induced seizures. The increase in FDG6P in nerve terminals agreed well with the increase in cortical neuronal glucose oxidation measured previously under the same conditions in vivo, indicating that direct uptake and oxidation of glucose in nerve terminals is substantial under resting and activated conditions. These results suggest that neuronal glucose-derived pyruvate is the major oxidative fuel for activated neurons, not lactate-derived from astrocytes, contradicting predictions of the original astrocyte-to-neuron lactate shuttle model under the range of study conditions.

Adenosine A2B and A3 receptor location at the mouse neuromuscular junction.

PubMed

Garcia, Neus; Priego, Mercedes; Hurtado, Erica; Obis, Teresa; Santafe, Manel M; Tomàs, Marta; Lanuza, Maria Angel; Tomàs, Josep

2014-07-01

To date, four subtypes of adenosine receptors have been cloned (A(1)R, A(2A)R, A(2B)R, and A(3)R). In a previous study we used confocal immunocytochemistry to identify A(1)R and A(2A)R receptors at mouse neuromuscular junctions (NMJs). The data shows that these receptors are localized differently in the three cells (muscle, nerve and glia) that configure the NMJs. A(1)R localizes in the terminal teloglial Schwann cell and nerve terminal, whereas A(2A)R localizes in the postsynaptic muscle and in the axon and nerve terminal. Here, we use Western blotting to investigate the presence of A(2B)R and A(3)R receptors in striated muscle and immunohistochemistry to localize them in the three cells of the adult neuromuscular synapse. The data show that A(2B)R and A(3)R receptors are present in the nerve terminal and muscle cells at the NMJs. Neither A(2B)R nor A(3)R receptors are localized in the Schwann cells. Thus, the four subtypes of adenosine receptors are present in the motor endings. The presence of these receptors in the neuromuscular synapse allows the receptors to be involved in the modulation of transmitter release. © 2014 Anatomical Society.

Ulcerative colitis: ultrastructure of interstitial cells in myenteric plexus.

PubMed

Rumessen, J J; Vanderwinden, J-M; Horn, T

2010-10-01

Interstitial cells of Cajal (ICC) are key regulatory cells in the gut. In the colon of patients with severe ulcerative colitis (UC), myenteric ICC had myoid ultrastructural features and were in close contact with nerve terminals. In all patients as opposed to controls, some ICC profiles showed degenerative changes, such as lipid droplets and irregular vacuoles. Nerve terminals often appeared swollen and empty. Glial cells, muscle cells, and fibroblast-like cells (FLC) showed no alterations. FLC enclosed macrophages (MLC), which were in close contact with naked axon terminals. The organization and cytological changes may be of pathophysiological significance in patients with UC.

Observations on the elimination of polyneuronal innervation in developing mammalian skeletal muscle.

PubMed Central

O'Brien, R A; Ostberg, A J; Vrbová, G

1978-01-01

1. The mechanism responsible for the elimination of polyneuronal innervation in developing rat soleus muscles was studied electrophysiologically and histologically. 2. Initially all the axons contacting a single end-plate have simple bulbous terminals. As elimination proceeds one axon develops terminal branches while the other terminals remain bulbous and may be seen in contact with, or a short distance away from, the end-plate. It is suggested that the branched terminal remains in contact with the muscle fibre while the other terminals withdraw. 3. At a time when polyneuronal innervation can no longer be detected electrophysiologically, the histological technique still shows the presence of end-plates contacted by more than one nerve terminal. 4. The effect of activity on the disappearance of polyneuronal innervation was examined. Activity was increased by electrical stimulation of the right sciatic nerve. This procedure also produced reflex activity in the contralateral limb. In both cases polyneuronal innervation was eliminated more rapidly in the active muscles. 5. The finding that proteolytic enzymes are released from muscles treated with acetylcholine (ACh), and the observation of the more rapid elimination of supernumerary terminals at the end-plates of active muscles, lead to the suggestion that superfluous nerve-muscle contacts are removed by the proteolytic enzymes in response to neuromuscular activity. The selective stabilization of only one of the terminals is discussed in the light of these results. Images Plate 1 Plate 2 PMID:722562

Membrane transporters as mediators of synaptic dopamine dynamics: implications for disease.

PubMed

Lohr, Kelly M; Masoud, Shababa T; Salahpour, Ali; Miller, Gary W

2017-01-01

Dopamine was first identified as a neurotransmitter localized to the midbrain over 50 years ago. The dopamine transporter (DAT; SLC6A3) and the vesicular monoamine transporter 2 (VMAT2; SLC18A2) are regulators of dopamine homeostasis in the presynaptic neuron. DAT transports dopamine from the extracellular space into the cytosol of the presynaptic terminal. VMAT2 then packages this cytosolic dopamine into vesicular compartments for subsequent release upon neurotransmission. Thus, DAT and VMAT2 act in concert to move the transmitter efficiently throughout the neuron. Accumulation of dopamine in the neuronal cytosol can trigger oxidative stress and neurotoxicity, suggesting that the proper compartmentalization of dopamine is critical for neuron function and risk of disease. For decades, studies have examined the effects of reduced transporter function in mice (e.g. DAT-KO, VMAT2-KO, VMAT2-deficient). However, we have only recently been able to assess the effects of elevated transporter expression using BAC transgenic methods (DAT-tg, VMAT2-HI mice). Complemented with in vitro work and neurochemical techniques to assess dopamine compartmentalization, a new focus on the importance of transporter proteins as both models of human disease and potential drug targets has emerged. Here, we review the importance of DAT and VMAT2 function in the delicate balance of neuronal dopamine. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

The dopamine beta-hydroxylase inhibitor nepicastat increases dopamine release and potentiates psychostimulant-induced dopamine release in the prefrontal cortex.

PubMed

Devoto, Paola; Flore, Giovanna; Saba, Pierluigi; Bini, Valentina; Gessa, Gian Luigi

2014-07-01

The dopamine-beta-hydroxylase inhibitor nepicastat has been shown to reproduce disulfiram ability to suppress the reinstatement of cocaine seeking after extinction in rats. To clarify its mechanism of action, we examined the effect of nepicastat, given alone or in association with cocaine or amphetamine, on catecholamine release in the medial prefrontal cortex and the nucleus accumbens, two key regions involved in the reinforcing and motivational effects of cocaine and in the reinstatement of cocaine seeking. Nepicastat effect on catecholamines was evaluated by microdialysis in freely moving rats. Nepicastat reduced noradrenaline release both in the medial prefrontal cortex and in the nucleus accumbens, and increased dopamine release in the medial prefrontal cortex but not in the nucleus accumbens. Moreover, nepicastat markedly potentiated cocaine- and amphetamine-induced extracellular dopamine accumulation in the medial prefrontal cortex but not in the nucleus accumbens. Extracellular dopamine accumulation produced by nepicastat alone or by its combination with cocaine or amphetamine was suppressed by the α2 -adrenoceptor agonist clonidine. It is suggested that nepicastat, by suppressing noradrenaline synthesis and release, eliminated the α2 -adrenoceptor mediated inhibitory mechanism that constrains dopamine release and cocaine- and amphetamine-induced dopamine release from noradrenaline or dopamine terminals in the medial prefrontal cortex. © 2012 The Authors, Addiction Biology © 2012 Society for the Study of Addiction.

Putative presynaptic dopamine dysregulation in schizophrenia is supported by molecular evidence from post-mortem human midbrain

PubMed Central

Purves-Tyson, T D; Owens, S J; Rothmond, D A; Halliday, G M; Double, K L; Stevens, J; McCrossin, T; Shannon Weickert, C

2017-01-01

The dopamine hypothesis of schizophrenia posits that increased subcortical dopamine underpins psychosis. In vivo imaging studies indicate an increased presynaptic dopamine synthesis capacity in striatal terminals and cell bodies in the midbrain in schizophrenia; however, measures of the dopamine-synthesising enzyme, tyrosine hydroxylase (TH), have not identified consistent changes. We hypothesise that dopamine dysregulation in schizophrenia could result from changes in expression of dopamine synthesis enzymes, receptors, transporters or catabolic enzymes. Gene expression of 12 dopamine-related molecules was examined in post-mortem midbrain (28 antipsychotic-treated schizophrenia cases/29 controls) using quantitative PCR. TH and the synaptic dopamine transporter (DAT) proteins were examined in post-mortem midbrain (26 antipsychotic-treated schizophrenia cases per 27 controls) using immunoblotting. TH and aromatic acid decarboxylase (AADC) mRNA and TH protein were unchanged in the midbrain in schizophrenia compared with controls. Dopamine receptor D2 short, vesicular monoamine transporter (VMAT2) and DAT mRNAs were significantly decreased in schizophrenia, with no change in DRD3 mRNA, DRD3nf mRNA and DAT protein between diagnostic groups. However, DAT protein was significantly increased in putatively treatment-resistant cases of schizophrenia compared to putatively treatment-responsive cases. Midbrain monoamine oxidase A (MAOA) mRNA was increased, whereas MAOB and catechol-O-methyl transferase mRNAs were unchanged in schizophrenia. We conclude that, whereas some mRNA changes are consistent with increased dopamine action (decreased DAT mRNA), others suggest reduced dopamine action (increased MAOA mRNA) in the midbrain in schizophrenia. Here, we identify a molecular signature of dopamine dysregulation in the midbrain in schizophrenia that mainly includes gene expression changes of molecules involved in dopamine synthesis and in regulating the time course of dopamine action. PMID:28094812

The N-terminal region of the dopamine D2 receptor, a rhodopsin-like GPCR, regulates correct integration into the plasma membrane and endocytic routes

PubMed Central

Cho, DI; Min, C; Jung, KS; Cheong, SY; Zheng, M; Cheong, SJ; Oak, MH; Cheong, JH; Lee, BK; Kim, KM

2012-01-01

BACKGROUND AND PURPOSE Functional roles of the N-terminal region of rhodopsin-like GPCR family remain unclear. Using dopamine D2 and D3 receptors as a model system, we probed the roles of the N-terminal region in the signalling, intracellular trafficking of receptor proteins, and explored the critical factors that determine the functionality of the N-terminal region. EXPERIMENTAL APPROACH The N-terminal region of the D2 receptor was gradually shortened or switched with that of the D3 receptor or a non-specific sequence (FLAG), or potential N-terminal glycosylation sites were mutated. Effects of these manipulations on surface expression, internalization, post-endocytic behaviours and signalling were determined. KEY RESULTS Shortening the N-terminal region of the D2 receptor enhanced receptor internalization and impaired surface expression and signalling; ligand binding, desensitization and down-regulation were not affected but their association with a particular microdomain, caveolae, was disrupted. Replacement of critical residues within the N-terminal region with the FLAG epitope failed to restore surface expression but partially restored the altered internalization and signalling. When the N-terminal regions were switched between D2 and D3 receptors, cell surface expression pattern of each receptor was switched. Mutations of potential N-terminal glycosylation sites inhibited surface expression but enhanced internalization of D2 receptors. CONCLUSIONS AND IMPLICATIONS Shortening of N-terminus or mutation of glycosylation sites located within the N-terminus enhanced receptor internalization but impaired the surface expression of D2 receptors. The N-terminal region of the D2 receptor, in a sequence-specific manner, controls the receptor's conformation and integration into the plasma membrane, which determine its subcellular localization, intracellular trafficking and signalling properties. PMID:22117524

Lack of functional and morphological susceptibility of the greater superficial petrosal nerve to developmental dietary sodium restriction.

PubMed

Sollars, S I; Hill, D L

2000-12-01

Restriction of dietary sodium during gestation has major effects on taste function and anatomy in the offspring. The chorda tympani nerve of offspring that are maintained on sodium-reduced chow throughout life (NaDep) has reduced neurophysiological responses to sodium and altered morphology of its terminal field in the nucleus of the solitary tract. There are many anatomical and physiological similarities between the chorda tympani nerve that innervates taste buds on the anterior tongue and the greater superficial petrosal nerve (GSP) that innervates taste buds on the palate. To determine if the GSP is similarly susceptible to the effects of dietary sodium restriction, the present study examined neurophysiological responses and the terminal field of the GSP in NaDep and control rats. Neurophysiological responses of the GSP to a variety of sodium and non-sodium stimuli did not differ between NaDep and control rats. Furthermore, the volume and shape of the GSP terminal field in the nucleus of the solitary tract did not differ between the groups. Therefore, despite the high degree of functional and anatomical correspondence between the chorda tympani nerve and the GSP, the GSP does not appear to be susceptible to the effects of lifelong dietary sodium restriction.

Substance P immunoreactive nerve terminals in the dorsolateral nucleus of the tractus solitarius: roles in the baroreceptor reflex.

PubMed

Massari, V J; Shirahata, M; Johnson, T A; Lauenstein, J M; Gatti, P J

1998-03-02

Physiological and light microscopic evidence suggest that substance P (SP) may be a neurotransmitter contained in first-order sensory baroreceptor afferents; however, ultrastructural support for this hypothesis is lacking. We have traced the central projections of the carotid sinus nerve (CSN) in the cat by utilizing the transganglionic transport of horseradish peroxidase (HRP). The dorsolateral subnucleus of the nucleus tractus solitarius (dlNTS) was processed for the histochemical visualization of transganglionically labeled CSN afferents and for the immunocytochemical visualization of SP by dual labeling light and electron microscopic methods. Either HRP or SP was readily identified in single-labeled unmyelinated axons, myelinated axons, and nerve terminals in the dlNTS. SP immunoreactivity was also identified in unmyelinated axons, myelinated axons, and nerve terminals in the dlNTS, which were simultaneously identified as CSN primary afferents. However, only 15% of CSN terminals in the dlNTS were immunoreactive for SP. Therefore, while the ultrastructural data support the hypothesis that SP immunoreactive first-order neurons are involved in the origination of the baroreceptor reflex, they suggest that only a modest part of the total sensory input conveyed from the carotid sinus baroreceptors to the dlNTS is mediated by SP immunoreactive CSN terminals. Five types of axo-axonic synapses were observed in the dlNTS. SP immunoreactive CSN afferents were very rarely involved in these synapses. Furthermore, SP terminals were never observed to form the presynaptic element in an axo-axonic synapse with a CSN afferent. Therefore, SP does not appear to be involved in the modulation of the baroreceptor reflex in the dlNTS. Copyright 1998 Elsevier Science B.V.

Terminal-Nerve-Derived Neuropeptide Y Modulates Physiological Responses in the Olfactory Epithelium of Hungry Axolotls (Ambystoma mexicanum)

PubMed Central

Mousley, Angela; Polese, Gianluca; Marks, Nikki J.; Eisthen, Heather L.

2007-01-01

The vertebrate brain actively regulates incoming sensory information, effectively filtering input and focusing attention toward environmental stimuli that are most relevant to the animal's behavioral context or physiological state. Such centrifugal modulation has been shown to play an important role in processing in the retina and cochlea, but has received relatively little attention in olfaction. The terminal nerve, a cranial nerve that extends underneath the lamina propria surrounding the olfactory epithelium, displays anatomical and neurochemical characteristics that suggest that it modulates activity in the olfactory epithelium. Using immunocytochemical techniques, we demonstrate that neuropeptide Y (NPY) is abundantly present in the terminal nerve in the axolotl (Ambystoma mexicanum), an aquatic salamander. Because NPY plays an important role in regulating appetite and hunger in many vertebrates, we investigated the possibility that NPY modulates activity in the olfactory epithelium in relation to the animal's hunger level. We therefore characterized the full length NPY gene from axolotls to enable synthesis of authentic axolotl NPY for use in electrophysiological experiments. We find that axolotl NPY modulates olfactory epithelial responses evoked by L-glutamic acid, a food-related odorant, but only in hungry animals. Similarly, whole-cell patch-clamp recordings demonstrate that bath application of axolotl NPY enhances the magnitude of a tetrodotoxin-sensitive inward current, but only in hungry animals. These results suggest that expression or activity of NPY receptors in the olfactory epithelium may change with hunger level, and that terminal nerve-derived peptides modulate activity in the olfactory epithelium in response to an animal's changing behavioral and physiological circumstances. PMID:16855098

Terminal nerve-derived neuropeptide y modulates physiological responses in the olfactory epithelium of hungry axolotls (Ambystoma mexicanum).

PubMed

Mousley, Angela; Polese, Gianluca; Marks, Nikki J; Eisthen, Heather L

2006-07-19

The vertebrate brain actively regulates incoming sensory information, effectively filtering input and focusing attention toward environmental stimuli that are most relevant to the animal's behavioral context or physiological state. Such centrifugal modulation has been shown to play an important role in processing in the retina and cochlea, but has received relatively little attention in olfaction. The terminal nerve, a cranial nerve that extends underneath the lamina propria surrounding the olfactory epithelium, displays anatomical and neurochemical characteristics that suggest that it modulates activity in the olfactory epithelium. Using immunocytochemical techniques, we demonstrate that neuropeptide Y (NPY) is abundantly present in the terminal nerve in the axolotl (Ambystoma mexicanum), an aquatic salamander. Because NPY plays an important role in regulating appetite and hunger in many vertebrates, we investigated the possibility that NPY modulates activity in the olfactory epithelium in relation to the animal's hunger level. We therefore characterized the full-length NPY gene from axolotls to enable synthesis of authentic axolotl NPY for use in electrophysiological experiments. We find that axolotl NPY modulates olfactory epithelial responses evoked by l-glutamic acid, a food-related odorant, but only in hungry animals. Similarly, whole-cell patch-clamp recordings demonstrate that bath application of axolotl NPY enhances the magnitude of a tetrodotoxin-sensitive inward current, but only in hungry animals. These results suggest that expression or activity of NPY receptors in the olfactory epithelium may change with hunger level, and that terminal nerve-derived peptides modulate activity in the olfactory epithelium in response to an animal's changing behavioral and physiological circumstances.

Intramuscular Distribution of the Abducens Nerve in the Lateral Rectus Muscle for the Management of Strabismus.

PubMed

Shin, Hyun Jin; Lee, Shin-Hyo; Shin, Kang-Jae; Koh, Ki-Seok; Song, Wu-Chul

2018-06-01

To elucidate the intramuscular distribution and branching patterns of the abducens nerve in the lateral rectus (LR) muscle so as to provide anatomical confirmation of the presence of compartmentalization, including for use in clinical applications such as botulinum toxin injections. Thirty whole-mount human cadaver specimens were dissected and then Sihler's stain was applied. The basic dimensions of the LR and its intramuscular nerve distribution were investigated. The distances from the muscle insertion to the point at which the abducens nerve enters the LR and to the terminal nerve plexus were also measured. The LR was 46.0 mm long. The abducens nerve enters the muscle on the posterior one-third of the LR and then typically divides into a few branches (average of 1.8). This supports a segregated abducens nerve selectively innervating compartments of the LR. The intramuscular nerve distribution showed a Y-shaped ramification with root-like arborization. The intramuscular nerve course finished around the middle of the LR (24.8 mm posterior to the insertion point) to form the terminal nerve plexus. This region should be considered the optimal target site for botulinum toxin injections. We have also identified the presence of an overlapping zone and communicating nerve branches between the neighboring LR compartments. Sihler's staining is a useful technique for visualizing the entire nerve network of the LR. Improving the knowledge of the nerve distribution patterns is important not only for researchers but also clinicians to understand the functions of the LR and the diverse pathophysiology of strabismus.

Afferent fibers and sensory ganglion cells within the oculomotor nerve in some mammals and man. II. Electrophysiological investigations.

PubMed

Manni, E; Bortolami, R; Pettorossi, V E; Lucchi, M L; Callegari, E

1978-01-01

The main aim of the present study was to localize with electrophysiological techniques the central projections and terminations of the aberrant trigeminal fibres contained in the oculomotor nerve of the lamb. After severing a trigeminal root, single-shock electrical stimulation of the trigeminal axons present in the central stump of the ipsilateral oculomotor nerve evoked field potentials in the area of, i) the subnucleus gelatinosus of the nucleus caudalis trigemini at the level of C1-C2; ii) the main sensory trigeminal nucleus; iii) the descending trigeminal nucleus and tract; iv) the adjacent reticular formation. Units whose discharge rate was influenced by such a stimulation were also found in the same territories. These regions actually exhibited degenerations after cutting an oculomotor nerve. We conclude, therefore, that the trigeminal fibres which leave the Vth nerve at the level of the cavernous sinus and enter the brain stem through the IIIrd nerve, end in the same structures which receive the terminations of the afferent fibres entering the brain stem through the sensory trigeminal root.

Utility of a tripolar stimulating electrode for eliciting dopamine release in the rat striatum.

PubMed

Bergstrom, B P; Garris, P A

1999-03-01

The present study evaluated tripolar stimulating electrodes for eliciting dopamine release in the rat brain in vivo. Stimulating electrodes were placed either in the medial forebrain bundle or in the ventral mesencephalon associated with the ventral tegmental area and substantia nigra. The concentration of extracellular dopamine was monitored in dopamine terminal fields at 100-ms intervals using fast-scan cyclic voltammetry at carbon-fiber microelectrodes. To characterize the stimulated area, recordings were collected in several striatal regions including the caudate putamen and the core and shell of the nucleus accumbens. The tripolar electrode was equally effective in stimulating dopamine release in medial and lateral regions of the striatum. In contrast, responses evoked by a bipolar electrode were typically greater in one mediolateral edge versus the other. The added size of the tripolar electrode did not appear to cause complications as signals were stable over the course of the experiment (3 h). Subsets of mesostriatal dopamine neurons could also be selectively activated using the tripolar electrode in excellent agreement with previously described topography. Taken together, these results suggested that the tripolar stimulating electrode is well suited for studying the regulation of midbrain dopamine neurons in vivo.

Crayfish neuromuscular facilitation activated by constant presynaptic action potentials and depolarizing pulses

PubMed Central

Zucker, Robert S.

1974-01-01

1. Experiments were conducted to test the hypothesis that facilitation of transmitter release in response to repetitive stimulation of the exciter motor axon to the crayfish claw opener muscle is due to an increase in the amplitude or duration of the action potential in presynaptic terminals. No consistent changes were found in the nerve terminal potential (n.t.p.) recorded extracellularly at synaptic sites on the surface of muscle fibres. 2. Apparent changes in n.t.p. are attributed to three causes. (i) Some recordings are shown to be contaminated by non-specific muscle responses which grow during facilitation. (ii) Some averaged n.t.p.s exhibit opposite changes in amplitude and duration which suggest a change in the synchrony of presynaptic nerve impulses at different frequencies. (iii) Some changes in n.t.p. are blocked by γ-methyl glutamate, an antagonist of the post-synaptic receptor, which suggests that these changes are caused by small muscle movements. 3. The only change in n.t.p. believed to represent an actual change in the intracellular signal is a reduction in n.t.p. amplitude to the second of two stimuli separated by a brief interval. 4. Tetra-ethyl ammonium ions increase synaptic transmission about 20% and prolong the n.t.p. about 15%. This result suggests that an increase in n.t.p. large enough to increase transmission by the several hundred per cent occurring during facilitation would be detected. 5. The nerve terminals are electrically excitable, and most synaptic sites have a diphasic or triphasic n.t.p., which suggests that the motor neurone terminals are actively invaded by nerve impulses. 6. When nerve impulses are blocked in tetrodotoxin, depolarization of nerve terminals increases the frequency of miniature excitatory junctional potentials (e.j.p.s), and a phasic e.j.p. can be evoked by large, brief depolarizing pulses. Responses to repetitive or paired depolarizations of constant amplitude and duration exhibit a facilitation similar to that of e.j.p.s evoked by nerve impulses. 7. It is concluded that facilitation in the crayfish claw opener is not due to a change in the presynaptic action potential, but is due to some change at a later step in the depolarization—secretion process. PMID:4153766

Crayfish neuromuscular facilitation activated by constant presynaptic action potentials and depolarizing pulses.

PubMed

Zucker, R S

1974-08-01

1. Experiments were conducted to test the hypothesis that facilitation of transmitter release in response to repetitive stimulation of the exciter motor axon to the crayfish claw opener muscle is due to an increase in the amplitude or duration of the action potential in presynaptic terminals. No consistent changes were found in the nerve terminal potential (n.t.p.) recorded extracellularly at synaptic sites on the surface of muscle fibres.2. Apparent changes in n.t.p. are attributed to three causes.(i) Some recordings are shown to be contaminated by non-specific muscle responses which grow during facilitation.(ii) Some averaged n.t.p.s exhibit opposite changes in amplitude and duration which suggest a change in the synchrony of presynaptic nerve impulses at different frequencies.(iii) Some changes in n.t.p. are blocked by gamma-methyl glutamate, an antagonist of the post-synaptic receptor, which suggests that these changes are caused by small muscle movements.3. The only change in n.t.p. believed to represent an actual change in the intracellular signal is a reduction in n.t.p. amplitude to the second of two stimuli separated by a brief interval.4. Tetra-ethyl ammonium ions increase synaptic transmission about 20% and prolong the n.t.p. about 15%. This result suggests that an increase in n.t.p. large enough to increase transmission by the several hundred per cent occurring during facilitation would be detected.5. The nerve terminals are electrically excitable, and most synaptic sites have a diphasic or triphasic n.t.p., which suggests that the motor neurone terminals are actively invaded by nerve impulses.6. When nerve impulses are blocked in tetrodotoxin, depolarization of nerve terminals increases the frequency of miniature excitatory junctional potentials (e.j.p.s), and a phasic e.j.p. can be evoked by large, brief depolarizing pulses. Responses to repetitive or paired depolarizations of constant amplitude and duration exhibit a facilitation similar to that of e.j.p.s evoked by nerve impulses.7. It is concluded that facilitation in the crayfish claw opener is not due to a change in the presynaptic action potential, but is due to some change at a later step in the depolarization-secretion process.

Maintenance of Mouse Gustatory Terminal Field Organization Is Disrupted following Selective Removal of Peripheral Sodium Salt Taste Activity at Adulthood.

PubMed

Skyberg, Rolf; Sun, Chengsan; Hill, David L

2017-08-09

Neural activity plays a critical role in the development of central circuits in sensory systems. However, the maintenance of these circuits at adulthood is usually not dependent on sensory-elicited neural activity. Recent work in the mouse gustatory system showed that selectively deleting the primary transduction channel for sodium taste, the epithelial sodium channel (ENaC), throughout development dramatically impacted the organization of the central terminal fields of three nerves that carry taste information to the nucleus of the solitary tract. More specifically, deleting ENaCs during development prevented the normal maturation of the fields. The present study was designed to extend these findings by testing the hypothesis that the loss of sodium taste activity impacts the maintenance of the normal adult terminal field organization in male and female mice. To do this, we used an inducible Cre-dependent genetic recombination strategy to delete ENaC function after terminal field maturation occurred. We found that removal of sodium taste neural activity at adulthood resulted in significant reorganization of mature gustatory afferent terminal fields in the nucleus of the solitary tract. Specifically, the chorda tympani and greater superficial petrosal nerve terminal fields were 1.4× and 1.6× larger than age-matched controls, respectively. By contrast, the glossopharyngeal nerve, which is not highly sensitive to sodium taste stimulation, did not undergo terminal field reorganization. These surprising results suggest that gustatory nerve terminal fields remain plastic well into adulthood, which likely impacts central coding of taste information and taste-related behaviors with altered taste experience. SIGNIFICANCE STATEMENT Neural activity plays a major role in the development of sensory circuits in the mammalian brain. However, the importance of sensory-driven activity in maintaining these circuits at adulthood, especially in subcortical structures, appears to be much less. Here, we tested whether the loss of sodium taste activity in adult mice impacts the maintenance of how taste nerves project to the first central relay. We found that specific loss of sodium-elicited taste activity at adulthood produced dramatic and selective reorganization of terminal fields in the brainstem. This demonstrates, for the first time, that taste-elicited activity is necessary for the normal maintenance of central gustatory circuits at adulthood and highlights a level of plasticity not seen in other sensory system subcortical circuits. Copyright © 2017 the authors 0270-6474/17/377619-12$15.00/0.

Neuromodulatory properties of fluorescent carbon dots: effect on exocytotic release, uptake and ambient level of glutamate and GABA in brain nerve terminals.

PubMed

Borisova, Tatiana; Nazarova, Anastasia; Dekaliuk, Mariia; Krisanova, Natalia; Pozdnyakova, Natalia; Borysov, Arsenii; Sivko, Roman; Demchenko, Alexander P

2015-02-01

Carbon dots (C-dots), a recently discovered class of fluorescent nano-sized particles with pure carbon core, have great bioanalytical potential. Neuroactive properties of fluorescent C-dots obtained from β-alanine by microwave heating were assessed based on the analysis of their effects on the key characteristics of GABA- and glutamatergic neurotransmission in isolated rat brain nerve terminals. It was found that C-dots (40-800 μg/ml) in dose-dependent manner: (1) decreased exocytotic release of [(3)H]GABA and L-[(14)C]glutamate; (2) reduced acidification of synaptic vesicles; (3) attenuated the initial velocity of Na(+)-dependent transporter-mediated uptake of [(3)H]GABA and L-[(14)C]glutamate; (4) increased the ambient level of the neurotransmitters, nevertheless (5) did not change significantly the potential of the plasma membrane of nerve terminals. Almost complete suppression of exocytotic release of the neurotransmitters was caused by C-dots at a concentration of 800 μg/ml. Fluorescent and neuromodulatory features combined in C-dots create base for their potential usage for labeling and visualization of key processes in nerve terminals, and also in theranostics. In addition, natural presence of carbon-containing nanoparticles in the human food chain and in the air may provoke the development of neurologic consequences. Copyright © 2014 Elsevier Ltd. All rights reserved.

High probability neurotransmitter release sites represent an energy efficient design

PubMed Central

Lu, Zhongmin; Chouhan, Amit K.; Borycz, Jolanta A.; Lu, Zhiyuan; Rossano, Adam J; Brain, Keith L.; Zhou, You; Meinertzhagen, Ian A.; Macleod, Gregory T.

2016-01-01

Nerve terminals contain multiple sites specialized for the release of neurotransmitters. Release usually occurs with low probability, a design thought to confer many advantages. High probability release sites are not uncommon but their advantages are not well understood. Here we test the hypothesis that high probability release sites represent an energy efficient design. We examined release site probabilities and energy efficiency at the terminals of two glutamatergic motor neurons synapsing on the same muscle fiber in Drosophila larvae. Through electrophysiological and ultrastructural measurements we calculated release site probabilities to differ considerably between terminals (0.33 vs. 0.11). We estimated the energy required to release and recycle glutamate from the same measurements. The energy required to remove calcium and sodium ions subsequent to nerve excitation was estimated through microfluorimetric and morphological measurements. We calculated energy efficiency as the number of glutamate molecules released per ATP molecule hydrolyzed, and high probability release site terminals were found to be more efficient (0.13 vs. 0.06). Our analytical model indicates that energy efficiency is optimal (~0.15) at high release site probabilities (~0.76). As limitations in energy supply constrain neural function, high probability release sites might ameliorate such constraints by demanding less energy. Energy efficiency can be viewed as one aspect of nerve terminal function, in balance with others, because high efficiency terminals depress significantly during episodic bursts of activity. PMID:27593375

Cannabinoid Type 1 Receptors Transiently Silence Glutamatergic Nerve Terminals of Cultured Cerebellar Granule Cells

PubMed Central

Ramírez-Franco, Jorge; Bartolomé-Martín, David; Alonso, Beatris; Torres, Magdalena; Sánchez-Prieto, José

2014-01-01

Cannabinoid receptors are the most abundant G protein-coupled receptors in the brain and they mediate retrograde short-term inhibition of neurotransmitter release, as well as long-term depression of synaptic transmission at many excitatory synapses. The induction of presynaptically silent synapses is a means of modulating synaptic strength, which is important for synaptic plasticity. Persistent activation of cannabinoid type 1 receptors (CB1Rs) mutes GABAergic terminals, although it is unclear if CB1Rs can also induce silencing at glutamatergic synapses. Cerebellar granule cells were transfected with VGLUT1-pHluorin to visualise the exo-endocytotic cycle. We found that prolonged stimulation (10 min) of cannabinoid receptors with the agonist HU-210 induces the silencing of previously active synapses. However, the presynaptic silencing induced by HU-210 is transient as it reverses after 20 min. cAMP with forskolin prevented CB1R-induced synaptic silencing, via activation of the Exchange Protein directly Activated by cAMP (Epac). Furthermore, Epac activation accelerated awakening of already silent boutons. Electron microscopy revealed that silencing was associated with synaptic vesicle (SV) redistribution within the nerve terminal, which diminished the number of vesicles close to the active zone of the plasma membrane. Finally, by combining functional and immunocytochemical approaches, we observed a strong correlation between the release capacity of the nerve terminals and RIM1α protein content, but not that of Munc13-1 protein. These results suggest that prolonged stimulation of cannabinoid receptors can transiently silence glutamatergic nerve terminals. PMID:24533119

Recovery of the sub-basal nerve plexus and superficial nerve terminals after corneal epithelial injury in mice.

PubMed

Downie, Laura E; Naranjo Golborne, Cecilia; Chen, Merry; Ho, Ngoc; Hoac, Cam; Liyanapathirana, Dasun; Luo, Carol; Wu, Ruo Bing; Chinnery, Holly R

2018-06-01

Our aim was to compare regeneration of the sub-basal nerve plexus (SBNP) and superficial nerve terminals (SNT) following corneal epithelial injury. We also sought to compare agreement when quantifying nerve parameters using different image analysis techniques. Anesthetized, female C57BL/6 mice received central 1-mm corneal epithelial abrasions. Four-weeks post-injury, eyes were enucleated and processed for PGP9.5 to visualize the corneal nerves using wholemount immunofluorescence staining and confocal microscopy. The percentage area of the SBNP and SNT were quantified using: ImageJ automated thresholds, ImageJ manual thresholds and manual tracings in NeuronJ. Nerve sum length was quantified using NeuronJ and Imaris. Agreement between methods was considered with Bland-Altman analyses. Four-weeks post-injury, the sum length of nerve fibers in the SBNP, but not the SNT, was reduced compared with naïve eyes. In the periphery, but not central cornea, of both naïve and injured eyes, nerve fiber lengths in the SBNP and SNT were strongly correlated. For quantifying SBNP nerve axon area, all image analysis methods were highly correlated. In the SNT, there was poor correlation between manual methods and auto-thresholding, with a trend towards underestimating nerve fiber area using auto-thresholding when higher proportions of nerve fibers were present. In conclusion, four weeks after superficial corneal injury, there is differential recovery of epithelial nerve axons; SBNP sum length is reduced, however the sum length of SNTs is similar to naïve eyes. Care should be taken when selecting image analysis methods to compare nerve parameters in different depths of the corneal epithelium due to differences in background autofluorescence. Copyright © 2018 Elsevier Ltd. All rights reserved.

Attenuation of methamphetamine-induced nigrostriatal dopaminergic neurotoxicity in mice by lipopolysaccharide pretreatment.

PubMed

Lin, Yin Chiu; Kuo, Yu-Min; Liao, Pao-Chi; Cherng, Chianfang G; Su, Su-Wen; Yu, Lung

2007-04-30

Immunological activation has been proposed to play a role in methamphetamine-induced dopaminergic terminal damage. In this study, we examined the roles of lipopolysaccharide, a pro-inflammatory and inflammatory factor, treatment in modulating the methamphetamine-induced nigrostriatal dopamine neurotoxicity. Lipopolysaccharide pretreatment did not affect the basal body temperature or methamphetamine-elicited hyperthermia three days later. Such systemic lipopolysaccharide treatment mitigated methamphetamine-induced striatal dopamine and 3,4-dihydroxyphenylacetic acid depletions in a dose-dependent manner. As the most potent dose (1 mg/kg) of lipopolysaccharide was administered two weeks, one day before or after the methamphetamine dosing regimen, methamphetamine-induced striatal dopamine and 3,4-dihydroxyphenylacetic acid depletions remained unaltered. Moreover, systemic lipopolysaccharide pretreatment (1 mg/kg) attenuated local methamphetamine infusion-produced dopamine and 3,4-dihydroxyphenylacetic acid depletions in the striatum, indicating that the protective effect of lipopolysaccharide is less likely due to interrupted peripheral distribution or metabolism of methamphetamine. We concluded a critical time window for systemic lipopolysaccharide pretreatment in exerting effective protection against methamphetamine-induced nigrostriatal dopamine neurotoxicity.

Increased presynaptic regulation of dopamine neurotransmission in the nucleus accumbens core following chronic ethanol self-administration in female macaques

PubMed Central

Siciliano, Cody A.; Calipari, Erin S.; Yorgason, Jordan T.; Lovinger, David M.; Mateo, Yolanda; Jimenez, Vanessa A.; Helms, Christa M.; Grant, Kathleen A.; Jones, Sara R.

2016-01-01

Rationale Hypofunction of striatal dopamine neurotransmission, or hypodopaminergia, is a consequence of excessive ethanol use, and is hypothesized to be a critical component of alcoholism, driving alcohol intake in an attempt to restore dopamine levels; however, the neurochemical mechanisms involved in these dopaminergic deficiencies are unknown. Objective Here we examined the specific dopaminergic adaptations that produce hypodopaminergia and contribute to alcohol use disorders using direct, sub-second measurements of dopamine signaling in nonhuman primates following chronic ethanol self-administration. Methods Female rhesus macaques completed one year of daily (22 hr/day) ethanol self-administration. Subsequently, fast-scan cyclic voltammetry was used in nucleus accumbens core brain slices to determine alterations in dopamine terminal function, including release and uptake kinetics, and sensitivity to quinpirole (D2/D3 dopamine receptor agonist) and U50,488 (kappa-opioid receptor agonist) induced inhibition of dopamine release. Results Ethanol drinking greatly increased uptake rates, which were positively correlated with lifetime ethanol intake. Furthermore, the sensitivity of dopamine D2/D3 autoreceptors and kappa-opioid receptors, which both act as negative regulators of presynaptic dopamine release, were moderately and robustly enhanced in ethanol drinkers. Conclusions Greater uptake rates and sensitivity to D2-type autoreceptor and kappa-opioid receptor agonists could converge to drive a hypodopaminergic state, characterized by reduced basal dopamine and an inability to mount appropriate dopaminergic responses to salient stimuli. Together, we outline the specific alterations to dopamine signaling that may drive ethanol-induced hypofunction of the dopamine system, and suggest that the dopamine and dynorphin/kappa-opioid receptor systems may be efficacious pharmcotherapeutic targets in the treatment of alcohol use disorders. PMID:26892380

Single cocaine exposure does not alter striatal pre-synaptic dopamine function in mice: an [18 F]-FDOPA PET study.

PubMed

Bonsall, David R; Kokkinou, Michelle; Veronese, Mattia; Coello, Christopher; Wells, Lisa A; Howes, Oliver D

2017-12-01

Cocaine is a recreational drug of abuse that binds to the dopamine transporter, preventing reuptake of dopamine into pre-synaptic terminals. The increased presence of synaptic dopamine results in stimulation of both pre- and post-synaptic dopamine receptors, considered an important mechanism by which cocaine elicits its reinforcing properties. However, the effects of acute cocaine administration on pre-synaptic dopamine function remain unclear. Non-invasive imaging techniques such as positron emission tomography have revealed impaired pre-synaptic dopamine function in chronic cocaine users. Similar impairments have been seen in animal studies, with microdialysis experiments indicating decreased basal dopamine release. Here we use micro positron emission tomography imaging techniques in mice to measure dopamine synthesis capacity and determine the effect of acute cocaine administration of pre-synaptic dopamine function. We show that a dose of 20 mg/kg cocaine is sufficient to elicit hyperlocomotor activity, peaking 15-20 min post treatment (p < 0.001). However, dopamine synthesis capacity in the striatum was not significantly altered by acute cocaine treatment (KiCer: 0.0097 per min vs. 0.0112 per min in vehicle controls, p > 0.05). Furthermore, expression levels of two key enzymes related to dopamine synthesis, tyrosine hydroxylase and aromatic l-amino acid decarboxylase, within the striatum of scanned mice were not significantly affected by acute cocaine pre-treatment (p > 0.05). Our findings suggest that while the regulation of dopamine synthesis and release in the striatum have been shown to change with chronic cocaine use, leading to a reduced basal tone, these adaptations to pre-synaptic dopaminergic neurons are not initiated following a single exposure to the drug. © 2017 International Society for Neurochemistry.

Increased presynaptic regulation of dopamine neurotransmission in the nucleus accumbens core following chronic ethanol self-administration in female macaques.

PubMed

Siciliano, Cody A; Calipari, Erin S; Yorgason, Jordan T; Lovinger, David M; Mateo, Yolanda; Jimenez, Vanessa A; Helms, Christa M; Grant, Kathleen A; Jones, Sara R

2016-04-01

Hypofunction of striatal dopamine neurotransmission, or hypodopaminergia, is a consequence of excessive ethanol use and is hypothesized to be a critical component of alcoholism, driving alcohol intake in an attempt to restore dopamine levels; however, the neurochemical mechanisms involved in these dopaminergic deficiencies are not fully understood. Here we examined the specific dopaminergic adaptations that produce hypodopaminergia and contribute to alcohol use disorders using direct, sub-second measurements of dopamine signaling in nonhuman primates following chronic ethanol self-administration. Female rhesus macaques completed 1 year of daily (22 h/day) ethanol self-administration. Subsequently, fast-scan cyclic voltammetry was used in nucleus accumbens core brain slices to determine alterations in dopamine terminal function, including release and uptake kinetics, and sensitivity to quinpirole (D2/D3 dopamine receptor agonist) and U50,488 (kappa opioid receptor agonist) induced inhibition of dopamine release. Ethanol drinking greatly increased uptake rates, which were positively correlated with lifetime ethanol intake. Furthermore, the sensitivity of dopamine D2/D3 autoreceptors and kappa opioid receptors, which both act as negative regulators of presynaptic dopamine release, was moderately and robustly enhanced in ethanol drinkers. Greater uptake rates and sensitivity to D2-type autoreceptor and kappa opioid receptor agonists could converge to drive a hypodopaminergic state, characterized by reduced basal dopamine and an inability to mount appropriate dopaminergic responses to salient stimuli. Together, we outline the specific alterations to dopamine signaling that may drive ethanol-induced hypofunction of the dopamine system and suggest that the dopamine and dynorphin/kappa opioid receptor systems may be efficacious pharmacotherapeutic targets in the treatment of alcohol use disorders.

Immunocytochemical localization of glutamic acid decarboxylase (GAD) and substance P in neural areas mediating motion-induced emesis: Effects of vagal stimulation on GAD immunoreactivity

NASA Technical Reports Server (NTRS)

Damelio, F.; Gibbs, M. A.; Mehler, W. R.; Daunton, Nancy G.; Fox, Robert A.

1991-01-01

Immunocytochemical methods were employed to localize the neurotransmitter amino acid gamma-aminobutyric acid (GABA) by means of its biosynthetic enzyme glutamic acid decarboxylase (GAD) and the neuropeptide substance P in the area postrema (AP), area subpostrema (ASP), nucleus of the tractus solitarius (NTS), and gelatinous nucleus (GEL). In addition, electrical stimulation was applied to the night vagus nerve at the cervical level to assess the effects on GAD-immunoreactivity (GAR-IR). GAD-IR terminals and fibers were observed in the AP, ASP, NTS, and GEL. They showed pronounced density at the level of the ASP and gradual decrease towards the solitary complex. Nerve cells were not labelled in our preparations. Ultrastructural studies showed symmetric or asymmetric synaptic contracts between labelled terminals and non-immunoreactive dendrites, axons, or neurons. Some of the labelled terminals contained both clear- and dense-core vesicles. Our preliminary findings, after electrical stimulation of the vagus nerve, revealed a bilateral decrease of GAD-IR that was particularly evident at the level of the ASP. SP-immunoreactive (SP-IR) terminals and fibers showed varying densities in the AP, ASP, NTS, and GEL. In our preparations, the lateral sub-division of the NTS showed the greatest accumulation. The ASP showed medium density of immunoreactive varicosities and terminals and the AP and GEL displayed scattered varicose axon terminals. The electron microscopy revealed that all immunoreactive terminals contained clear-core vesicles which make symmetric or asymmetric synaptic contact with unlabelled dendrites. It is suggested that the GABAergic terminals might correspond to vagal afferent projections and that GAD/GABA and substance P might be co-localized in the same terminal allowing the possibility of a regulated release of the transmitters in relation to demands.

Morphology of salivary gland and distribution of dopamine and serotonin on red palm weevil (RPW), Rhynchophorus ferrugineus (Coleoptera: Curculionidae)

NASA Astrophysics Data System (ADS)

Hidayah, A. S. Nurul; Wahida, O. Nurul; Shafinaz, M. N. Norefrina; Idris, A. G.

2013-11-01

The Red Palm Weevil (RPW), Rhynchophorus ferrugineus (Olivier, 1790) is insect pest to plants of the family Palmaceae. No study has been reported on the digestive mechanism of Red Palm Weevil (RPW). Salivary glands are responsible in the feeding regulation of insect while serotonin and dopamine play a significant role in the regulation of this gland. It is great to see the morphology of the salivary gland and how dopamine and serotonin possibly play their role in this gland. Two variation of RPW, striped and spotted RPW were chosen. The morphology of the gland of both RPW variants examined by using light microscopy was found to be a tubular type. Immunohistochemical analysis conducted showed that serotonin and dopamine in both variations did not innervate the glands suggesting they are not act as neurotransmitter. However, it can be detected on few areas within the glands. This suggests that serotonin and dopamine may act as a hormone because there is no evidence on the nerve fibers. The role of these biogenic amines in the salivary gland of RPW needs further investigation. Hopefully the data would help in understanding the mechanism of salivary glands control by biogenic amines in RPW specifically and insects with sucking mouthpart generally.

Uptake and metabolism of fructose by rat neocortical cells in vivo and by isolated nerve terminals in vitro.

PubMed

Hassel, Bjørnar; Elsais, Ahmed; Frøland, Anne-Sofie; Taubøll, Erik; Gjerstad, Leif; Quan, Yi; Dingledine, Raymond; Rise, Frode

2015-05-01

Fructose reacts spontaneously with proteins in the brain to form advanced glycation end products (AGE) that may elicit neuroinflammation and cause brain pathology, including Alzheimer's disease. We investigated whether fructose is eliminated by oxidative metabolism in neocortex. Injection of [(14) C]fructose or its AGE-prone metabolite [(14) C]glyceraldehyde into rat neocortex in vivo led to formation of (14) C-labeled alanine, glutamate, aspartate, GABA, and glutamine. In isolated neocortical nerve terminals, [(14) C]fructose-labeled glutamate, GABA, and aspartate, indicating uptake of fructose into nerve terminals and oxidative fructose metabolism in these structures. This was supported by high expression of hexokinase 1, which channels fructose into glycolysis, and whose activity was similar with fructose or glucose as substrates. By contrast, the fructose-specific ketohexokinase was weakly expressed. The fructose transporter Glut5 was expressed at only 4% of the level of neuronal glucose transporter Glut3, suggesting transport across plasma membranes of brain cells as the limiting factor in removal of extracellular fructose. The genes encoding aldose reductase and sorbitol dehydrogenase, enzymes of the polyol pathway that forms glucose from fructose, were expressed in rat neocortex. These results point to fructose being transported into neocortical cells, including nerve terminals, and that it is metabolized and thereby detoxified primarily through hexokinase activity. We asked how the brain handles fructose, which may react spontaneously with proteins to form 'advanced glycation end products' and trigger inflammation. Neocortical cells took up and metabolized extracellular fructose oxidatively in vivo, and isolated nerve terminals did so in vitro. The low expression of fructose transporter Glut5 limited uptake of extracellular fructose. Hexokinase was a main pathway for fructose metabolism, but ketohexokinase (which leads to glyceraldehyde formation) was expressed too. Neocortical cells also took up and metabolized glyceraldehyde oxidatively. © 2015 International Society for Neurochemistry.

Resveratrol and pinostilbene confer neuroprotection against aging-related deficits through an ERK1/2 dependent-mechanism

USDA-ARS?s Scientific Manuscript database

Age-related declines in motor function may be due, in part, to an increase in oxidative stress in the aging brain leading to death of brain cells that transmit dopamine (DA), one of the brain chemicals responsible for transmitting signals between brain nerve cells. We examined the neuroprotective ef...

Morphology of P2X3-immunoreactive nerve endings in the rat laryngeal mucosa.

PubMed

Takahashi, Natsumi; Nakamuta, Nobuaki; Yamamoto, Yoshio

2016-02-01

The morphological characteristics of P2X3-immunoreactive nerve endings in the laryngeal mucosa were herein examined using immunohistochemistry with confocal laser microscopy. Ramified intraepithelial nerve endings immunoreactive to P2X3 were distributed in the epiglottis and arytenoid region. The axon terminals of P2X3-immunoreactive ramified endings were beaded or flat in shape. These endings were also immunoreactive to P2X2 and not identical to the nerve endings immunoreactive to Na(+)-K(+)-ATPase α3-subunit, substance P (SP), and calcitonin gene-related peptide (CGRP). P2X3-immunoreactive axon terminals were also immunoreactive to vGLUT1, vGLUT2, and vGLUT3. In addition to ramified endings, P2X3-immunoreactive nerve endings were associated with α-gustducin-immunoreactive solitary chemosensory cells and/or SNAP25-immunoreactive neuroendocrine cells. Furthermore, P2X3-immunoreactive nerve endings were also observed in the taste bud-like chemosensory cell clusters of the stratified squamous epithelium covering epiglottic and arytenoid cartilage. The P2X3-immunoreactive nerve endings that associated with sensory and/or endocrine cells and chemosensory cell clusters were also immunoreactive to P2X2, vGLUT1, vGLUT2, and vGLUT3, but not to SP or CGRP. In conclusion, P2X3-immunoreactive nerve endings may be classified into two types, i.e., intraepithelial ramified nerve endings and nerve endings associated with chemosensory cells and neuroendocrine cells.

Involvement of catecholaminergic neurons in motor innervation of striated muscle in the mouse esophagus.

PubMed

van der Keylen, Piet; Garreis, Fabian; Steigleder, Ruth; Sommer, Daniel; Neuhuber, Winfried L; Wörl, Jürgen

2016-05-01

Enteric co-innervation is a peculiar innervation pattern of striated esophageal musculature. Both anatomical and functional data on enteric co-innervation related to various transmitters have been collected in different species, although its function remains enigmatic. However, it is unclear whether catecholaminergic components are involved in such a co-innervation. Thus, we examined to identify catecholaminergic neuronal elements and clarify their relationship to other innervation components in the esophagus, using immunohistochemistry with antibodies against tyrosine hydroxylase (TH), vesicular acetylcholine transporter (VAChT), choline acetyltransferase (ChAT) and protein gene product 9.5 (PGP 9.5), α-bungarotoxin (α-BT) and PCR with primers for amplification of cDNA encoding TH and dopamine-β-hydroxylase (DBH). TH-positive nerve fibers were abundant throughout the myenteric plexus and localized on about 14% of α-BT-labelled motor endplates differing from VAChT-positive vagal nerve terminals. TH-positive perikarya represented a subpopulation of only about 2.8% of all PGP 9.5-positive myenteric neurons. Analysis of mRNA showed both TH and DBH transcripts in the mouse esophagus. As ChAT-positive neurons in the compact formation of the nucleus ambiguus were negative for TH, the TH-positive nerve varicosities on motor endplates are presumably of enteric origin, although a sympathetic origin cannot be excluded. In the medulla oblongata, the cholinergic ambiguus neurons were densely supplied with TH-positive varicosities. Thus, catecholamines may modulate vagal motor innervation of esophageal-striated muscles not only at the peripheral level via enteric co-innervation but also at the central level via projections to the nucleus ambiguus. As Parkinson's disease, with a loss of central dopaminergic neurons, also affects the enteric nervous system and dysphagia is prevalent in patients with this disease, investigation of intrinsic catecholamines in the esophagus may be worthwhile to understand such a symptom.

Exposure to the Polybrominated Diphenyl Ether Mixture DE-71 Damages the Nigrostriatal Dopamine System: Role of Dopamine Handling in Neurotoxicity

PubMed Central

Bradner, Joshua M.; Suragh, Tiffany A.; Wilson, W. Wyatt; Lazo, Carlos R.; Stout, Kristen A.; Kim, Hye Mi; Wang, Min Z.; Walker, Douglas I.; Pennell, Kurt D.; Richardson, Jason R.; Miller, Gary W.; Caudle, W. Michael

2013-01-01

In the last several decades polybrominated diphenyl ethers (PBDEs) have replaced the previously banned polychlorinated biphenyls (PCBs) in multiple flame retardant utilities. As epidemiological and laboratory studies have suggested PCBs as a risk factor for Parkinson’s disease (PD), the similarities between PBDEs and PCBs suggest that PBDEs have the potential to be neurotoxic to the dopamine system. The purpose of this study was to evaluate the neurotoxic effects of the PBDE mixture, DE-71, on the nigrostriatal dopamine system and address the role of altered dopamine handling in mediating this neurotoxicity. Using an in vitro model system we found DE-71 effectively caused cell death in a dopaminergic cell line as well as reducing the number of TH+ neurons isolated from VMAT2 WT and LO animals. Assessment of DE-71 neurotoxicity in vivo demonstrated significant deposition of PBDE congeners in the brains of mice, leading to reductions in striatal dopamine and dopamine handling, as well as reductions in the striatal dopamine transporter (DAT) and VMAT2. Additionally, DE-71 elicited a significant locomotor deficit in the VMAT2 WT and LO mice. However, no change was seen in TH expression in dopamine terminal or in the number of dopamine neurons in the substantia nigra pars compacta (SNpc). To date, these are the first data to demonstrate that exposure to PBDEs disrupts the nigrostriatal dopamine system. Given their similarities to PCBs, additional laboratory and epidemiological research should be considered to assess PBDEs as a potential risk factor for PD and other neurological disorders. PMID:23287494

Facilitatory effects of piracetam on excitability of motor nerve terminals and neuromuscular transmission.

PubMed

Hall, E D; Von Voigtlander, P F

1987-11-01

The possible in vivo facilitatory effects of the pyrrolidine acetamide no-otropic agent piracetam on neuromuscular transmission, were studied based upon reports of enhancement of central cholinergic function. Piracetam was shown to antagonize the lethal effects of the neuromuscular blocking agent hemicholinium-3 (HC-3), in female CF-1 mice when administered in a dose of 100 mg/kg (i.p.) simultaneously with HC-3. A 30 mg/kg (i.p.) dose of piracetam was ineffective by itself, although it potentiated the protective effects of choline (25 mg/kg i.p.). The analogs of piracetam, aniracetam, oxiracetam, pramiracetam and dupracetam also significantly antagonized the lethality of HC-3 at doses over a 30-300 mg/kg range. The acute facilitatory properties of piracetam on neuromuscular transmission were examined in more detail in vivo in the soleus nerve muscle preparation of the cat. A 100 mg/kg (i.v.) dose of piracetam, while having no effect on its own, significantly enhanced the ability of a 200 micrograms/kg (i.v.) dose of edrophonium to produce a potentiation of muscle contraction dependent on repetitive discharges in the soleus motor nerve terminals. In preparations in which the motor nerve terminals of the soleus were in a partially degenerated state as a result of section of the motor axons 48 hr earlier, piracetam acted to restore their sensitivity to edrophonium. Furthermore, in both normal and partially degenerated preparations, piracetam significantly decreased the neuromuscular blocking effects of a 150 micrograms/kg (i.v.) dose of d-tubocurarine. The mechanism of the neuromuscular facilitatory effects of piracetam on neuromuscular transmission is discussed in terms of an enhanced excitability of motor nerve terminals together with an action to increase the synthesis and/or release of acetylcholine.

The origin of the post-tetanic hyperpolarization of mammalian motor nerve terminals

PubMed Central

Gage, P. W.; Hubbard, J. I.

1966-01-01

1. Motor nerve terminals in magnesium-poisoned rat hemidiaphragm-phrenic nerve preparations in vitro were stimulated with short depolarizing pulses of approximately threshold strength and the evoked antidromic responses recorded from the phrenic nerve. The percentage of these 1/sec or 0·5/sec stimuli to which there was no antidromic response was used as a quantitative measure of the terminal excitability. After standard tetanic stimulation (1000 impulses at 100/sec) the excitability of the terminals was depressed for an average duration of 60-70 sec, during most of which time no antidromic responses to stimuli of pretetanic intensity were recorded. There was no significant interaction between stimuli to the terminals at rates of 1 or 0·5/sec. 2. Potassium-free solutions at first increased, then decreased, the post-tetanic depression of excitability. Raising [K]o threefold (15 mM) abolished the post-tetanic depression and often converted it to an exaltation of excitability. 3. Polarizing currents were applied to the terminals with a second electrode. Depolarizing currents increased, while hyperpolarizing currents decreased, the post-tetanic depression of excitability. 4. In solutions with 70% of the normal NaCl content replaced by sucrose, the post-tetanic depression of excitability was reversibly prolonged. 5. In the presence of 7·7 × 10-6 M digoxin or 0·42 mM ouabain there was a small reversible reduction of post-tetanic excitability. 6. After exposure to solutions containing no glucose or to solutions containing 3-5 mM sodium azide the excitability of the terminals was not altered by the tetanus. After washing with the control solution, post-tetanic depression of excitability returned. Antimycin-A (1·8 × 10-6 M) had little or no effect upon post-tetanic excitability. 7. It was concluded that the post-tetanic depression of excitability reflected hyperpolarization of the terminals and that this hyperpolarization was caused by a shift of the membrane potential towards the potassium equilibrium potential because of an increase in potassium permeability. ImagesFig. 1 PMID:5921834

Variation in Lingual Nerve Course: A Human Cadaveric Study

PubMed Central

Al-Amery, Samah M.; Nambiar, Phrabhakaran; Naidu, Murali

2016-01-01

The lingual nerve is a terminal branch of the mandibular nerve. It is varied in its course and in its relationship to the mandibular alveolar crest, submandibular duct and also the related muscles in the floor of the mouth. This study aims to understand the course of the lingual nerve from the molar area until its insertion into the tongue muscle. This cadaveric research involved the study of 14 hemi-mandibles and consisted of two parts: (i) obtaining morphometrical measurements of the lingual nerve to three landmarks on the alveolar ridge, and (b) understanding non-metrical or morphological appearance of its terminal branches inserting in the ventral surface of the tongue. The mean distance between the fourteen lingual nerves and the alveolar ridge was 12.36 mm, and they were located 12.03 mm from the lower border of the mandible. These distances were varied when near the first molar (M1), second molar (M2) and third molar (M3). The lingual nerve coursed on the floor of the mouth for approximately 25.43 mm before it deviated toward the tongue anywhere between the mesial of M1 and distal of M2. Thirteen lingual nerves were found to loop around the submandibular duct for an average distance of 6.92 mm (95% CI: 5.24 to 8.60 mm). Their looping occurred anywhere between the M2 and M3. In 76.9% of the cases the loop started around the M3 region and the majority (69.2%) of these looping ended at between the first and second molars and at the lingual developmental groove of the second molar. It gave out as many as 4 branches at its terminal end at the ventral surface of the tongue, with the presence of 2 branches being the most common pattern. An awareness of the variations of the lingual nerve is important to prevent any untoward complications or nerve injury and it is hoped that these findings will be useful for planning of surgical procedures related to the alveolar crest, submandibular gland/ duct and surrounding areas. PMID:27662622

Central GLP-1 receptor activation modulates cocaine-evoked phasic dopamine signaling in the nucleus accumbens core.

PubMed

Fortin, Samantha M; Roitman, Mitchell F

2017-07-01

Drugs of abuse increase the frequency and magnitude of brief (1-3s), high concentration (phasic) dopamine release events in terminal regions. These are thought to be a critical part of drug reinforcement and ultimately the development of addiction. Recently, metabolic regulatory peptides, including the satiety signal glucagon-like peptide-1 (GLP-1), have been shown to modulate cocaine reward-driven behavior and sustained dopamine levels after cocaine administration. Here, we use fast-scan cyclic voltammetry (FSCV) to explore GLP-1 receptor (GLP-1R) modulation of dynamic dopamine release in the nucleus accumbens (NAc) during cocaine administration. We analyzed dopamine release events in both the NAc shell and core, as these two subregions are differentially affected by cocaine and uniquely contribute to motivated behavior. We found that central delivery of the GLP-1R agonist Exendin-4 suppressed the induction of phasic dopamine release events by intravenous cocaine. This effect was selective for dopamine signaling in the NAc core. Suppression of phasic signaling in the core by Exendin-4 could not be attributed to interference with cocaine binding to one of its major substrates, the dopamine transporter, as cocaine-induced increases in reuptake were unaffected. The results suggest that GLP-1R activation, instead, exerts its suppressive effects by altering dopamine release - possibly by suppressing the excitability of dopamine neurons. Given the role of NAc core dopamine in the generation of conditioned responses based on associative learning, suppression of cocaine-induced dopamine signaling in this subregion by GLP-1R agonism may decrease the reinforcing properties of cocaine. Thus, GLP-1Rs remain viable targets for the treatment and prevention of cocaine seeking, taking and relapse. Copyright © 2017 Elsevier Inc. All rights reserved.

Synaptic Regulator α-Synuclein in Dopaminergic Fibers Is Essentially Required for the Maintenance of Subependymal Neural Stem Cells.

PubMed

Perez-Villalba, Ana; Sirerol-Piquer, M Salomé; Belenguer, Germán; Soriano-Cantón, Raúl; Muñoz-Manchado, Ana Belén; Villadiego, Javier; Alarcón-Arís, Diana; Soria, Federico N; Dehay, Benjamin; Bezard, Erwan; Vila, Miquel; Bortolozzi, Analía; Toledo-Aral, Juan José; Pérez-Sánchez, Francisco; Fariñas, Isabel

2018-01-24

Synaptic protein α-synuclein (α-SYN) modulates neurotransmission in a complex and poorly understood manner and aggregates in the cytoplasm of degenerating neurons in Parkinson's disease. Here, we report that α-SYN present in dopaminergic nigral afferents is essential for the normal cycling and maintenance of neural stem cells (NSCs) in the brain subependymal zone of adult male and female mice. We also show that premature senescence of adult NSCs into non-neurogenic astrocytes in mice lacking α-SYN resembles the effects of dopaminergic fiber degeneration resulting from chronic exposure to 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine or intranigral inoculation of aggregated toxic α-SYN. Interestingly, NSC loss in α-SYN-deficient mice can be prevented by viral delivery of human α-SYN into their sustantia nigra or by treatment with l-DOPA, suggesting that α-SYN regulates dopamine availability to NSCs. Our data indicate that α-SYN, present in dopaminergic nerve terminals supplying the subependymal zone, acts as a niche component to sustain the neurogenic potential of adult NSCs and identify α-SYN and DA as potential targets to ameliorate neurogenic defects in the aging and diseased brain. SIGNIFICANCE STATEMENT We report an essential role for the protein α-synuclein present in dopaminergic nigral afferents in the regulation of adult neural stem cell maintenance, identifying the first synaptic regulator with an implication in stem cell niche biology. Although the exact role of α-synuclein in neural transmission is not completely clear, our results indicate that it is required for stemness and the preservation of neurogenic potential in concert with dopamine. Copyright © 2018 the authors 0270-6474/18/380815-12$15.00/0.

The nigrostriatal dopamine system of aging GFRα-1 heterozygous mice: neurochemistry, morphology and behavior

PubMed Central

Zaman, Vandana; Boger, Heather A.; Granholm, Ann-Charlotte; Rohrer, Baerbel; Moore, Alfred; Buhusi, Mona; Gerhardt, Greg A.; Hoffer, Barry J.; Middaugh, Lawrence D.

2009-01-01

Given the established importance of glial cell line-derived neurotrophic factor (GDNF) in maintaining dopaminergic neurotransmitter systems, the nigrostriatal system and associated behaviors of mice with genetic reduction of its high-affinity receptor, GDNF receptor (GFR)α-1 (GFRα-1+/−), were compared with wild-type controls. Motor activity and the stimulatory effects of a dopamine (DA) D1 receptor agonist (SKF 82958) were assessed longitudinally at 8 and 18 months of age. Monoamine concentrations and dopaminergic nerve terminals in the striatum and the number of dopaminergic neurons in the substantia nigra (SN) were assessed. The results support the importance of GFRα-1 in maintaining normal function of the nigrostriatal dopaminergic system, with deficits being observed for GFRα-1+/− mice at both ages. Motor activity was lower and the stimulatory effects of the DA agonist were enhanced for the older GFRα-1+/− mice. DA in the striatum was reduced in the GFRα-1+/− mice at both ages, and tyrosine hydroxylase-positive cell numbers in the SN were reduced most substantially in the older GFRα-1+/− mice. The combined behavioral, pharmacological probe, neurochemical and morphological measures provide evidence of abnormalities in GFRα-1+/− mice that are indicative of an exacerbated aging-related decline in dopaminergic system function. The noted deficiencies, in turn, suggest that GFRα-1 is necessary for GDNF to maintain normal function of the nigrostriatal dopaminergic system. Although the precise mechanism(s) for the aging-related changes in the dopaminergic system remain to be established, the present study clearly establishes that genetic reductions in GFRα-1 can contribute to the degenerative changes observed in this system during the aging process. PMID:18973577

Dopamine-induced programmed cell death is associated with cytochrome c release and caspase-3 activation in snail salivary gland cells.

PubMed

Pirger, Zsolt; Rácz, Boglárka; Kiss, Tibor

2009-02-01

PCD (programmed cell death) is a common mechanism to remove unwanted and excessive cells from organisms. In several exocrine cell types, PCD mode of release of secretory products has been reported. The molecular mechanism of the release, however, is largely unknown. Our aim was to study the molecular mechanism of saliva release from cystic cells, the specific cell type of snail SGs (salivary glands). SG cells in active feeding animals revealed multiple morphological changes characteristic of PCD. Nerve stimulation and DA (dopamine) increased the number of TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling)-positive cells both in inactive and feeding animals. The DA-induced PCD was prevented by TEA (tetraethylammonium chloride) and eticlopride, emphasizing the role of K channels and D2 receptors in the PCD of cystic cells. DA enhanced cyto-c (cytochrome c) translocation into the cytosol and methyl-beta-cyclodextrin prevented it, suggesting apoptosome formation and ceramide involvement in the PCD linking of the surface DA receptor to mitochondria. Western blot analysis revealed that the release of cyto-c was under the control of Bcl-2 and Bad. DA also increased the active caspase-3 in gland cells while D2 receptor antagonists and TEA attenuated it. Our results provide evidence for a type of transmitter-mediated pathway that regulates the PCD of secretory cells in a mitochondrial-caspase-dependent manner. The activation of specific molecules, such as K channels, DA receptors, cyto-c, ceramide, Bcl-2 proteins and caspase-3, but not caspase-8, was demonstrated in cells involved in the DA-induced PCD, suggesting that PCD is a physiological method for the release of saliva from SG cells.

The newly synthesized pool of dopamine determines the severity of methamphetamine-induced neurotoxicity.

PubMed

Thomas, David M; Francescutti-Verbeem, Dina M; Kuhn, Donald M

2008-05-01

The neurotransmitter dopamine (DA) has long been implicated as a participant in the neurotoxicity caused by methamphetamine (METH), yet, its mechanism of action in this regard is not fully understood. Treatment of mice with the tyrosine hydroxylase (TH) inhibitor alpha-methyl-p-tyrosine (AMPT) lowers striatal cytoplasmic DA content by 55% and completely protects against METH-induced damage to DA nerve terminals. Reserpine, by disrupting vesicle amine storage, depletes striatal DA by more than 95% and accentuates METH-induced neurotoxicity. l-DOPA reverses the protective effect of AMPT against METH and enhances neurotoxicity in animals with intact TH. Inhibition of MAO-A by clorgyline increases pre-synaptic DA content and enhances METH striatal neurotoxicity. In all conditions of altered pre-synaptic DA homeostasis, increases or decreases in METH neurotoxicity paralleled changes in striatal microglial activation. Mice treated with AMPT, l-DOPA, or clorgyline + METH developed hyperthermia to the same extent as animals treated with METH alone, whereas mice treated with reserpine + METH were hypothermic, suggesting that the effects of alterations in cytoplasmic DA on METH neurotoxicity were not strictly mediated by changes in core body temperature. Taken together, the present data reinforce the notion that METH-induced release of DA from the newly synthesized pool of transmitter into the extracellular space plays an essential role in drug-induced striatal neurotoxicity and microglial activation. Subtle alterations in intracellular DA content can lead to significant enhancement of METH neurotoxicity. Our results also suggest that reactants derived from METH-induced oxidation of released DA may serve as neuronal signals that lead to microglial activation early in the neurotoxic process associated with METH.

Ventral tegmental ionotropic glutamate receptor stimulation of nucleus accumbens tonic dopamine efflux blunts hindbrain-evoked phasic neurotransmission: implications for dopamine dysregulation disorders.

PubMed

Tye, S J; Miller, A D; Blaha, C D

2013-11-12

Activation of glutamate receptors within the ventral tegmental area (VTA) stimulates extrasynaptic (basal) dopamine release in terminal regions, including the nucleus accumbens (NAc). Hindbrain inputs from the laterodorsal tegmental nucleus (LDT) are critical for elicitation of phasic VTA dopamine cell activity and consequent transient dopamine release. This study investigated the role of VTA ionotropic glutamate receptor (iGluR) stimulation on both basal and LDT electrical stimulation-evoked dopamine efflux in the NAc using in vivo chronoamperometry and fixed potential amperometry in combination with stearate-graphite paste and carbon fiber electrodes, respectively. Intra-VTA infusion of the iGluR agonists (±)-α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA; 1 μg/μl) or N-methyl-d-aspartic acid (NMDA; 2 μg/μl) enhanced basal NAc dopamine efflux. This iGluR-mediated potentiation of basal dopamine efflux was paralleled by an attenuation of LDT-evoked transient NAc dopamine efflux, suggesting that excitation of basal activity effectively inhibited the capacity of hindbrain afferents to elicit transient dopamine efflux. In line with this, post-NMDA infusion of the dopamine D2 autoreceptor (D2R) agonist quinpirole (1 μg/μl; intra-VTA) partially recovered NMDA-mediated attenuation of LDT-evoked NAc dopamine, while concurrently attenuating NMDA-mediated potentiation of basal dopamine efflux. Post-NMDA infusion of quinpirole (1 μg/μl) alone attenuated basal and LDT-evoked dopamine efflux. Taken together, these data reveal that hyperstimulation of basal dopamine transmission can stunt hindbrain burst-like stimulation-evoked dopamine efflux. Inhibitory autoreceptor mechanisms within the VTA help to partially recover the magnitude of phasic dopamine efflux, highlighting the importance of both iGluRs and D2 autoreceptors in maintaining the functional balance of tonic and phasic dopamine neurotransmission. Dysregulation of this balance may have important implications for disorders of dopamine dysregulation such as attention deficit hyperactivity disorder. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Increased release of norepinephrine and dopamine from canine kidney during bilateral carotid occlusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bradley, T.; Hjemdahl, P.; DiBona, G.F.

1987-02-01

The renal overflow of norepinephrine (NE) and dopamine (DA) to plasma from the innervated kidney was studied at rest and during sympathetic nervous system activation by bilateral carotid artery occlusion (BCO) in vagotomized dogs under barbiturate or barbiturate/nitrous oxide anesthesia. BCO elevated arterial pressure and the arterial plasma concentration of NE, DA, and epinephrine (Epi). Renal vascular resistance (renal arterial pressure kept constant) increased by 15 +/- 7% and the net renal venous outflows (renal veno-arterial concentration difference x renal plasma flow) of NE and DA were enhanced. To obtain more correct estimates of the renal contribution to the renalmore » venous catecholamine outflow, they corrected for the renal extraction of arterial catecholamines, assessed as the extractions of (/sup 3/H)NE, (/sup 3/H)DA, or endogenous Epi. The (/sup 3/H)NE corrected renal NE overflow to plasma increased from 144 +/- 40 to 243 +/- 64 pmol-min/sup -1/ during BCO, which, when compared with a previous study of the (/sup 3/H)NE corrected renal NE overflow to plasma evoked by electrical renal nerve stimulation, corresponds to a 40% increase in nerve impulse frequency from approx. 0.6 Hz. If the renal catecholamine extraction was not taken into account the effect of BCO was underestimated. The renal DA overflow to plasma was about one-fifth of the NE overflow both at rest and during BCO, indicating that there was no preferential activation of noradrenergic or putative dopaminergic nerves by BCO.« less

No association between schizophrenia and polymorphisms within the genes for debrisoquine 4-hydroxylase (CYP2D6) and the dopamine transporter (DAT)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daniels, J.; Williams, J.; Asherson, P.

1995-02-27

It has been suggested that the cytochrome P450 mono-oxygenase, debrisoquine 4-hydroxylase, is involved in the catabolism and processing of neurotransmitters subsequent to their reuptake into target cells. It is also thought to be related to the dopamine transporter that acts to take released dopamine back up into presynaptic terminals. The present study used the association approach to test the hypothesis that mutations in the genes for debrisoquine 4-hydroxylase (CYP2D6) and the dopamine transporter (DAT) confer susceptibility to schizophrenia. There were no differences in allele or genotype frequencies between patients and controls in the mutations causing the poor metaboliser phenotype inmore » CYP2D6. In addition there was no association found between schizophrenia and a 48 bp repeat within the 3{prime} untranslated region of DAT. 18 refs., 2 tabs.« less

Evidence for crustacean cardioactive peptide-like innervation of the gut in Locusta migratoria.

PubMed

Donini, Andrew; Ngo, Caroline; Lange, Angela B

2002-11-01

Hindguts from female Vth instar larvae, young adults (1-2 days) and old adults (>10 days) are equally sensitive to the crustacean cardioactive peptide (CCAP), with changes in contraction occurring at a threshold concentration of 10(-9)M and maximal responses observed at concentrations ranging between 10(-7) and 5x10(-6)M. An immunohistochemical examination of the gut of Locusta migratoria with an antiserum raised against CCAP revealed an extensive network of CCAP-like immunoreactive processes on the hindgut and posterior midgut via the 11th sternal nerve arising from the terminal abdominal ganglion. Anterograde filling of the 11th sternal nerve with neurobiotin revealed extensive processes and terminals on the hindgut. Retrograde filling of the branch of the 11th sternal nerve which innervates the hindgut with neurobiotin revealed two bilaterally paired cells in the terminal abdominal ganglion which co-localized with CCAP-like immunoreactivity. Results suggest that a CCAP-like substance acts as a neurotransmitter/neuromodulator at the locust hindgut.

Nucleus Accumbens Microcircuit Underlying D2-MSN-Driven Increase in Motivation.

PubMed

Soares-Cunha, Carina; Coimbra, Bárbara; Domingues, Ana Verónica; Vasconcelos, Nivaldo; Sousa, Nuno; Rodrigues, Ana João

2018-01-01

The nucleus accumbens (NAc) plays a central role in reinforcement and motivation. Around 95% of the NAc neurons are medium spiny neurons (MSNs), divided into those expressing dopamine receptor D1 (D1R) or dopamine receptor D2 (D2R). Optogenetic activation of D2-MSNs increased motivation, whereas inhibition of these neurons produced the opposite effect. Yet, it is still unclear how activation of D2-MSNs affects other local neurons/interneurons or input terminals and how this contributes for motivation enhancement. To answer this question, in this work we combined optogenetic modulation of D2-MSNs with in loco pharmacological delivery of specific neurotransmitter antagonists in rats. First, we showed that optogenetic activation of D2-MSNs increases motivation in a progressive ratio (PR) task. We demonstrated that this behavioral effect relies on cholinergic-dependent modulation of dopaminergic signalling of ventral tegmental area (VTA) terminals, which requires D1R and D2R signalling in the NAc. D2-MSN optogenetic activation decreased ventral pallidum (VP) activity, reducing the inhibitory tone to VTA, leading to increased dopaminergic activity. Importantly, optogenetic activation of D2-MSN terminals in the VP was sufficient to recapitulate the motivation enhancement. In summary, our data suggests that optogenetic stimulation of NAc D2-MSNs indirectly modulates VTA dopaminergic activity, contributing for increased motivation. Moreover, both types of dopamine receptors signalling in the NAc are required in order to produce the positive behavioral effects.

Nucleus Accumbens Microcircuit Underlying D2-MSN-Driven Increase in Motivation

PubMed Central

Soares-Cunha, Carina; Coimbra, Bárbara; Domingues, Ana Verónica; Vasconcelos, Nivaldo; Sousa, Nuno

2018-01-01

Abstract The nucleus accumbens (NAc) plays a central role in reinforcement and motivation. Around 95% of the NAc neurons are medium spiny neurons (MSNs), divided into those expressing dopamine receptor D1 (D1R) or dopamine receptor D2 (D2R). Optogenetic activation of D2-MSNs increased motivation, whereas inhibition of these neurons produced the opposite effect. Yet, it is still unclear how activation of D2-MSNs affects other local neurons/interneurons or input terminals and how this contributes for motivation enhancement. To answer this question, in this work we combined optogenetic modulation of D2-MSNs with in loco pharmacological delivery of specific neurotransmitter antagonists in rats. First, we showed that optogenetic activation of D2-MSNs increases motivation in a progressive ratio (PR) task. We demonstrated that this behavioral effect relies on cholinergic-dependent modulation of dopaminergic signalling of ventral tegmental area (VTA) terminals, which requires D1R and D2R signalling in the NAc. D2-MSN optogenetic activation decreased ventral pallidum (VP) activity, reducing the inhibitory tone to VTA, leading to increased dopaminergic activity. Importantly, optogenetic activation of D2-MSN terminals in the VP was sufficient to recapitulate the motivation enhancement. In summary, our data suggests that optogenetic stimulation of NAc D2-MSNs indirectly modulates VTA dopaminergic activity, contributing for increased motivation. Moreover, both types of dopamine receptors signalling in the NAc are required in order to produce the positive behavioral effects. PMID:29780881

Effect of acute millimeter wave exposure on dopamine metabolism of NGF-treated PC12 cells.

PubMed

Haas, Alexis J; Le Page, Yann; Zhadobov, Maxim; Sauleau, Ronan; Dréan, Yves Le; Saligaut, Christian

2017-07-01

Several forthcoming wireless telecommunication systems will use electromagnetic frequencies at millimeter waves (MMWs), and technologies developed around the 60-GHz band will soon know a widespread distribution. Free nerve endings within the skin have been suggested to be the targets of MMW therapy which has been used in the former Soviet Union. So far, no studies have assessed the impact of MMW exposure on neuronal metabolism. Here, we investigated the effects of a 24-h MMW exposure at 60.4 GHz, with an incident power density (IPD) of 5 mW/cm², on the dopaminergic turnover of NGF-treated PC12 cells. After MMW exposure, both intracellular and extracellular contents of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were studied using high performance liquid chromatography. Impact of exposure on the dopamine transporter (DAT) expression was also assessed by immunocytochemistry. We analyzed the dopamine turnover by assessing the ratio of DOPAC to DA, and measuring DOPAC accumulation in the medium. Neither dopamine turnover nor DAT protein expression level were impacted by MMW exposure. However, extracellular accumulation of DOPAC was found to be slightly increased, but not significantly. This result was related to the thermal effect, and overall, no evidence of non-thermal effects of MMW exposure were observed on dopamine metabolism. © The Author 2017. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Dopaminergic Presynaptic Modulation of Nigral Afferents: Its Role in the Generation of Recurrent Bursting in Substantia Nigra Pars Reticulata Neurons

PubMed Central

de Jesús Aceves, José; Rueda-Orozco, Pavel E.; Hernández, Ricardo; Plata, Víctor; Ibañez-Sandoval, Osvaldo; Galarraga, Elvira; Bargas, José

2011-01-01

Previous work has shown the functions associated with activation of dopamine presynaptic receptors in some substantia nigra pars reticulata (SNr) afferents: (i) striatonigral terminals (direct pathway) posses presynaptic dopamine D1-class receptors whose action is to enhance inhibitory postsynaptic currents (IPSCs) and GABA transmission. (ii) Subthalamonigral terminals posses D1- and D2-class receptors where D1-class receptor activation enhances and D2-class receptor activation decreases excitatory postsynaptic currents. Here we report that pallidonigral afferents posses D2-class receptors (D3 and D4 types) that decrease inhibitory synaptic transmission via presynaptic modulation. No action of D1-class agonists was found on pallidonigral synapses. In contrast, administration of D1-receptor antagonists greatly decreased striatonigral IPSCs in the same preparation, suggesting that tonic dopamine levels help in maintaining the function of the striatonigral (direct) pathway. When both D3 and D4 type receptors were blocked, pallidonigral IPSCs increased in amplitude while striatonigral connections had no significant change, suggesting that tonic dopamine levels are repressing a powerful inhibition conveyed by pallidonigral synapses (a branch of the indirect pathway). We then blocked both D1- and D2-class receptors to acutely decrease direct pathway (striatonigral) and enhance indirect pathways (subthalamonigral and pallidonigral) synaptic force. The result was that most SNr projection neurons entered a recurrent bursting firing mode similar to that observed during Parkinsonism in both patients and animal models. These results raise the question as to whether the lack of dopamine in basal ganglia output nuclei is enough to generate some pathological signs of Parkinsonism. PMID:21347219

Dopamine-Dependent Compensation Maintains Motor Behavior in Mice with Developmental Ablation of Dopaminergic Neurons

PubMed Central

DeMaro, Joseph A.; Knoten, Amanda; Hoshi, Masato; Pehek, Elizabeth; Johnson, Eugene M.; Gereau, Robert W.

2013-01-01

The loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) and consequent depletion of striatal dopamine are known to underlie the motor deficits observed in Parkinson's disease (PD). Adaptive changes in dopaminergic terminals and in postsynaptic striatal neurons can compensate for significant losses of striatal dopamine, resulting in preservation of motor behavior. In addition, compensatory changes independent of striatal dopamine have been proposed based on PD therapies that modulate nondopaminergic circuits within the basal ganglia. We used a genetic strategy to selectively destroy dopaminergic neurons in mice during development to determine the necessity of these neurons for the maintenance of normal motor behavior in adult and aged mice. We find that loss of 90% of SNc dopaminergic neurons and consequent depletion of >95% of striatal dopamine does not result in changes in motor behavior in young-adult or aged mice as evaluated by an extensive array of motor behavior tests. Treatment of aged mutant mice with the dopamine receptor antagonist haloperidol precipitated motor behavior deficits in aged mutant mice, indicating that <5% of striatal dopamine is sufficient to maintain motor function in these mice. We also found that mutant mice exhibit an exaggerated response to l-DOPA compared with control mice, suggesting that preservation of motor function involves sensitization of striatal dopamine receptors. Our results indicate that congenital loss of dopaminergic neurons induces remarkable adaptions in the nigrostriatal system where limited amounts of dopamine in the dorsal striatum can maintain normal motor function. PMID:24155314

Immunohistochemical demonstration of enkephalin-containing nerve fibers in guinea pig and rat lungs.

PubMed

Shimosegawa, T; Foda, H D; Said, S I

1989-08-01

Met-enkephalin (Met-Enk) and Leu-enkephalin (Leu-Enk), the opioid peptides originally isolated from the brain, are believed to act as inhibitory neuromodulators at various synaptic sites. In this immunohistochemical study, we have investigated the localization and distribution of Met- and Leu-Enk immunoreactivities in airways and pulmonary vessels of guinea pigs and rats. Immunoreactivities to both peptides were found in nerve fibers and nerve terminals distributed mainly to the trachea and major bronchi, and were especially prevalent in the smooth muscle layer, in the lamina propria, and around tracheal and bronchial glands, but not in the epithelium. Few immunoreactive nerve fibers were detected in smaller bronchi, bronchioles, and alveoli. Enkephalin-immunoreactive nerve fibers were also localized in the walls of pulmonary and bronchial vessels. Within airway microganglia, immunoreactivity was observed in a few nerve terminals, but not in ganglion cell bodies. Met- and Leu-Enk immunoreactive nerve fibers showed similar distribution patterns, though minor differences were noted between the two species: Enk-immunoreactive nerve fibers in the smooth muscle layer were more abundant in guinea pigs than in rats, whereas those in mucous glands were richer in rats than in guinea pigs. These results document the presence of Met- and Leu-Enk immunoreactivity in nerve fibers supplying guinea pig and rat airways and pulmonary vessels, and provide a morphologic basis for the view that enkephalins are likely neurotransmitters or neuromodulators in the lung.

Greater Ethanol Inhibition of Presynaptic Dopamine Release in C57BL/6J than DBA/2J Mice: Role of Nicotinic Acetylcholine Receptors

PubMed Central

Yorgason, Jordan T.; Rose, Jamie H.; McIntosh, J. Michael; Ferris, Mark J.; Jones, Sara R.

2014-01-01

The mesolimbic dopamine system, originating in the ventral tegmental area (VTA) and projecting to the nucleus accumbens (NAc), has been heavily implicated in the reinforcing effects of ethanol. Recent slice voltammetry studies have shown that ethanol inhibits dopamine release selectively during highfrequency activity that elicits phasic dopamine release shown to be important for learning and reinforcement. Presently, we examined ethanol inhibition of electrically evoked NAc dopamine in two mouse strains with divergent dopamine responses to ethanol, C57BL/6 (C57) and DBA/2J (DBA) mice. Previous electrophysiology and microdialysis studies have demonstrated greater ethanol induced VTA dopaminergic firing and NAc dopamine elevations in DBA compared to C57 mice. Additionally, DBA mice have greater ethanol responses in dopamine-related behaviors, including hyperlocomotion and conditioned place preference. Currently, we demonstrate greater sensitivity of ethanol inhibition of NAc dopamine signaling in C57 compared to DBA mice. The reduced sensitivity to ethanol inhibition in DBA mice may contribute to the overall greater ethanol-induced dopamine signaling and related behaviors observed in this strain. NAc cholinergic activity is known to potently modulate terminal dopamine release. Additionally, ethanol is known to interact with multiple aspects of nicotinic acetylcholine receptor activity. Therefore, we examined ethanol-mediated inhibition of dopamine release at two ethanol concentrations (80 and 160mM) during bath application of the non-selective nicotinic receptor antagonist mecamylamine, as well as compounds selective for the β2- (DhβE) and α6- (α-conotoxin MII [H9A; L15A]) subunit-containing receptors. Mecamylamine and DhβE decreased dopamine release and reduced ethanol's inhibitory effects on dopamine in both DBA and C57 mice. Further, α-conotoxin also reduced the dopamine release and the dopamine-inhibiting effects of ethanol at the 80mM, but not 160mM, concentration. These data suggest that ethanol is acting in part through nicotinic acetylcholine receptors, or downstream effectors, to reduce dopamine release during high-frequency activity. PMID:25451295

N-cadherin expression in palisade nerve endings of rat vellus hairs.

PubMed

Kaidoh, Toshiyuki; Inoué, Takao

2008-02-01

Palisade nerve endings (PNs) are mechanoreceptors around vellus hairs of mammals. Each lanceolate nerve ending (LN) of the PN is characterized by a sensory nerve ending symmetrically sandwiched by two processes of type II terminal Schwann cells (tSCIIs). However, the molecular mechanisms underlying the structural organization of the PN are poorly understood. Electron microscopy showed that adherens junctions appeared to adhere to the sensory nerve ending and tSCII processes, so we examined the location of the N-cadherin adhesion system in PNs of rat vellus hairs by using immunoelectron microscopy. N-cadherin localized near both ends of the cell boundary between sensory nerve ending and tSCII processes, which corresponded to the sites of adherens junctions. We further found cadherin-associated proteins, alpha- and beta-catenins, at the linings of adherens junctions. Three-dimensional reconstruction of immunoelectron microscopic serial thin sections showed four linear arrays of N-cadherin arranged longitudinally along the LN beneath the four longitudinal borders of two tSCII processes. In contrast, sensory nerve fibers just proximal to the LNs formed common unmyelinated nerve fibers, in which N-cadherin was located mainly at the mesaxon of type I terminal Schwann cells (tSCIs). These results suggest that the four linear arrays of N-cadherin-mediated junctions adhere the sensory nerve ending and tSCII processes side by side to form the characteristic structure of the LN, and the structural differences between the LNs and the proximal unmyelinated nerve fibers possibly are due to the difference in the pattern of N-cadherin expression between sensory nerve endings and tSCII or tSCI processes. (c) 2007 Wiley-Liss, Inc.

Dopamine D2 receptor expression in the corticotroph cells of the human normal pituitary gland.

PubMed

Pivonello, Rosario; Waaijers, Marlijn; Kros, Johan M; Pivonello, Claudia; de Angelis, Cristina; Cozzolino, Alessia; Colao, Annamaria; Lamberts, Steven W J; Hofland, Leo J

2017-08-01

The dopamine D 2 receptor is the main dopamine receptor expressed in the human normal pituitary gland. The aim of the current study was to evaluate dopamine D 2 receptor expression in the corticotroph cell populations of the anterior lobe and pars intermedia, as well as posterior lobe of the human normal pituitary gland by immunohistochemistry. Human normal pituitary gland samples obtained from routine autopsies were used for the study. In all cases, histology together with immunostaining for adrenocorticotropic hormone, melanocyte-stimulating hormone, prolactin, and neurofilaments were performed and compared to the immunostaining for D 2 receptor. D 2 receptor was heterogeneously expressed in the majority of the cell populations of the anterior and posterior lobe as well as in the area localized between the anterior and posterior lobe, and arbitrary defined as "intermediate zone". This zone, characterized by the presence of nerve fibers included the residual pars intermedia represented by the colloid-filled cysts lined by the remnant melanotroph cells strongly expressing D 2 receptors, and clusters of corticotroph cells, belonging to the anterior lobe but localized within the cysts and adjacent to the posterior lobe, variably expressing D 2 receptors. D 2 dopamine receptor is expressed in the majority of the cell populations of the human normal pituitary gland, and particularly, in the different corticotroph cell populations localized in the anterior lobe and the intermediate zone of the pituitary gland.

[Molecular mechanisms of neurotransmission].

PubMed

Nagatsu, T

2000-12-01

Neurotransmission is regulated by neurotransmitters at the synapses in the neuronal circuits. Main neurotransmitters are classified into the groups of amino acids, amines, purines, peptides, and nitric oxide. In principle, neurotransmitters except peptides are synthesized in the presynaptic neuroterminals from the precursors by the synthesizing enzymes, stored in the synaptic vesicles, released by exocytosis into the synaptic cleft, combined with the postsynaptic membrane receptors, and induce a series of signal transduction to produce acute, short-term, or long-term physiological effects. Termination of the neurotransmission is carried out either by re-uptake into presynaptic nerve terminals through plasma membrane transporters and storage into synaptic vesicles through vesicular transporters or by degradation through metabolizing enzymes (acetylcholine and peptides). Almost all genes related to neurotransmitters have been cloned and the structures of the genes and the protein products have been characterized. Molecular mechanisms of neurotransmission have been elucidated by mouse molecular genetics such as transgenic or knockout mice. Over-expression of human tyrosine hydroxylase (TH). the rate-limiting enzyme of catecholamine synthesis, in transgenic mice (Kaneda et al, Neuron 6, 583-584, 1991) or conversion of norepinephrine neurons to epinephrine neurons (Kobayashi et al, Proc Natl Acad Sci USA 89, 1631-1635, 1992) does not significantly change the phenotype due to compensatory mechanisms such as receptor down-regulation. In contrast, TH (-/-) mutant mice die at perinatal period due to heart failure caused by norepinephrine deficiency in the sympathetic neurons (Kobayashi et al, J Biol Chem 270, 27235-27243, 1995). TH (+/-) mice show a partial decrease in norepinephrine and a modest memory impairment (Kobayashi et al, J Neurosci 20, 2418-2426, 2000). One problem with adult phenotype in transgenic or knockout mice is that mutations cause the confounding effect of the developmental compensation. Thus conditional knockout of a specific type of neurons at a definite time after birth is required. Immunotoxin mediated conditional cell targeting (IMCT) (Kobayashi et al, Proc Natl Acad Sci 92, 1132-1136, 1995) is a novel transgenic technique for elucidating the function of a neuron in a neuronal circuit. Human molecular genetics of genetic neurological diseases are also useful for elucidating molecular mechanisms of neurotransmission. Autosomal dominant dopa-responsive dystonia (DRD) (Segawa's disease) with mutations of GTP cyclohydrolase I (Ichinose et al, Nature Genet 8, 236-242, 1994) causes a partial decrease in dopamine in the nigrostriatal dopamine neurons and produces a dystonia phenotype (Segawa's syndrome). In contrast, autosomal recessive GTP cyclohydrolase I deficiency with complete loss of the enzyme activity produces deficiencies of dopamine, norepinephrine, and serotonin and complex phenotypes with severe neurological symptoms (Ichinose et al, J Biol Chem 270, 10062-10071, 1995).

Functional Connectome Analysis of Dopamine Neuron Glutamatergic Connections in Forebrain Regions.

PubMed

Mingote, Susana; Chuhma, Nao; Kusnoor, Sheila V; Field, Bianca; Deutch, Ariel Y; Rayport, Stephen

2015-12-09

In the ventral tegmental area (VTA), a subpopulation of dopamine neurons express vesicular glutamate transporter 2 and make glutamatergic connections to nucleus accumbens (NAc) and olfactory tubercle (OT) neurons. However, their glutamatergic connections across the forebrain have not been explored systematically. To visualize dopamine neuron forebrain projections and to enable photostimulation of their axons independent of transmitter status, we virally transfected VTA neurons with channelrhodopsin-2 fused to enhanced yellow fluorescent protein (ChR2-EYFP) and used DAT(IREScre) mice to restrict expression to dopamine neurons. ChR2-EYFP-expressing neurons almost invariably stained for tyrosine hydroxylase, identifying them as dopaminergic. Dopamine neuron axons visualized by ChR2-EYFP fluorescence projected most densely to the striatum, moderately to the amygdala and entorhinal cortex (ERC), sparsely to prefrontal and cingulate cortices, and rarely to the hippocampus. Guided by ChR2-EYFP fluorescence, we recorded systematically from putative principal neurons in target areas and determined the incidence and strength of glutamatergic connections by activating all dopamine neuron terminals impinging on recorded neurons with wide-field photostimulation. This revealed strong glutamatergic connections in the NAc, OT, and ERC; moderate strength connections in the central amygdala; and weak connections in the cingulate cortex. No glutamatergic connections were found in the dorsal striatum, hippocampus, basolateral amygdala, or prefrontal cortex. These results indicate that VTA dopamine neurons elicit widespread, but regionally distinct, glutamatergic signals in the forebrain and begin to define the dopamine neuron excitatory functional connectome. Dopamine neurons are important for the control of motivated behavior and are involved in the pathophysiology of several major neuropsychiatric disorders. Recent studies have shown that some ventral midbrain dopamine neurons are capable of glutamate cotransmission. With conditional expression of channelrhodopsin in dopamine neurons, we systematically explored dopamine neuron connections in the forebrain and identified regionally specific dopamine neuron excitatory connections. Establishing that only a subset of forebrain regions receive excitatory connections from dopamine neurons will help to determine the function of dopamine neuron glutamate cotransmission, which likely involves transmission of precise temporal signals and enhancement of the dynamic range of dopamine neuron signals. Copyright © 2015 the authors 0270-6474/15/3516259-13$15.00/0.

Dopamine modulation of GABAergic function enables network stability and input selectivity for sustaining working memory in a computational model of the prefrontal cortex.

PubMed

Lew, Sergio E; Tseng, Kuei Y

2014-12-01

Dopamine modulation of GABAergic transmission in the prefrontal cortex (PFC) is thought to be critical for sustaining cognitive processes such as working memory and decision-making. Here, we developed a neurocomputational model of the PFC that includes physiological features of the facilitatory action of dopamine on fast-spiking interneurons to assess how a GABAergic dysregulation impacts on the prefrontal network stability and working memory. We found that a particular non-linear relationship between dopamine transmission and GABA function is required to enable input selectivity in the PFC for the formation and retention of working memory. Either degradation of the dopamine signal or the GABAergic function is sufficient to elicit hyperexcitability in pyramidal neurons and working memory impairments. The simulations also revealed an inverted U-shape relationship between working memory and dopamine, a function that is maintained even at high levels of GABA degradation. In fact, the working memory deficits resulting from reduced GABAergic transmission can be rescued by increasing dopamine tone and vice versa. We also examined the role of this dopamine-GABA interaction for the termination of working memory and found that the extent of GABAergic excitation needed to reset the PFC network begins to occur when the activity of fast-spiking interneurons surpasses 40 Hz. Together, these results indicate that the capability of the PFC to sustain working memory and network stability depends on a robust interplay of compensatory mechanisms between dopamine tone and the activity of local GABAergic interneurons.

Dopamine agonist suppression of rapid-eye-movement sleep is secondary to sleep suppression mediated via limbic structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miletich, R.S.

The effects of pergolide, a direct dopamine receptor agonist, on sleep and wakefulness, motor behavior and /sup 3/H-spiperone specific binding in limbic structures and striatum in rats was studied. The results show that pergolide induced a biphasic dose effect, with high doses increasing wakefulness and suppressing sleep while low dose decreased wakefulness, but increased sleep. It was shown that pergolide-induced sleep suppression was blocked by ..cap alpha..-glupenthixol and pimozide, two dopamine receptor antagonists. It was further shown that pergolide merely delayed the rebound resulting from rapid-eye-movement (REM) sleep deprivation, that dopamine receptors stimulation had no direct effect on the period,more » phase or amplitude of the circadian rhythm of REM sleep propensity and that there was no alteration in the coupling of REM sleep episodes with S/sub 2/ episodes. Rapid-eye-movement sleep deprivation resulted in increased sensitivity to the pergolide-induced wakefulness stimulation and sleep suppression and pergolide-induced motor behaviors of locomotion and head bobbing. /sup 3/H-spiperone specific binding to dopamine receptors was shown to be altered by REM sleep deprivation in the subcortical limbic structures. It is concluded that the REM sleep suppressing action of dopamine receptor stimulation is secondary to sleep suppression per se and not secondary to a unique effect on the REM sleep. Further, it is suggested that the wakefulness stimulating action of dopamine receptor agonists is mediated by activation of the dopamine receptors in the terminal areas of the mesolimbocortical dopamine projection system.« less

Active uptake of substance P carboxy-terminal heptapeptide (5-11) into rat brain and rabbit spinal cord slices.

PubMed

Nakata, Y; Kusaka, Y; Yajima, H; Segawa, T

1981-12-01

We previously reported that nerve terminals and glial cells lack an active uptake system capable of terminating transmitter action of substance P (SP). In the present study, we demonstrated the existence of an active uptake system for SP carboxy-terminal heptapeptide, (5-11)SP. When the slices from either rat brain or rabbit spinal cord were incubated with [3H](5-11)SP, the uptake of (5-11)SP into slices was observed. The uptake system has the properties of an active transport mechanism: it is dependent on temperature and sensitive to hypoosmotic treatment and is inhibited by ouabain and dinitrophenol (DNP). In the brain, (5-11)SP was accumulated by means of a high-affinity and a low-affinity uptake system. The Km and the Vmax values for the high-affinity system were 4.20 x 10(-8) M and 7.59 fmol/10 mg wet weight/min, respectively, whereas these values for the low-affinity system were 1.00 x 10(-6) M and 100 fmol/10 mg wet weight/min, respectively. In the spinal cord, there was only one uptake system, with a Km value of 2.16 x 10(-7) M and Vmax value of 26.2 fmol/10 mg wet weight/min. These results suggest that when SP is released from nerve terminals, it is hydrolysed into (5-11)SP before or after acting as a neurotransmitter, which is in turn accumulated into nerve terminals. Therefore, the uptake system may represent a possible mechanism for the inactivation of SP.

Regulator of G protein signaling-12 modulates the dopamine transporter in ventral striatum and locomotor responses to psychostimulants.

PubMed

Gross, Joshua D; Kaski, Shane W; Schroer, Adam B; Wix, Kimberley A; Siderovski, David P; Setola, Vincent

2018-02-01

Regulators of G protein signaling are proteins that accelerate the termination of effector stimulation after G protein-coupled receptor activation. Many regulators of G protein signaling proteins are highly expressed in the brain and therefore considered potential drug discovery targets for central nervous system pathologies; for example, here we show that RGS12 is highly expressed in microdissected mouse ventral striatum. Given a role for the ventral striatum in psychostimulant-induced locomotor activity, we tested whether Rgs12 genetic ablation affected behavioral responses to amphetamine and cocaine. RGS12 loss significantly decreased hyperlocomotion to lower doses of both amphetamine and cocaine; however, other outcomes of administration (sensitization and conditioned place preference) were unaffected, suggesting that RGS12 does not function in support of the rewarding properties of these psychostimulants. To test whether observed response changes upon RGS12 loss were caused by changes to dopamine transporter expression and/or function, we prepared crude membranes from the brains of wild-type and RGS12-null mice and measured dopamine transporter-selective [ 3 H]WIN 35428 binding, revealing an increase in dopamine transporter levels in the ventral-but not dorsal-striatum of RGS12-null mice. To address dopamine transporter function, we prepared striatal synaptosomes and measured [ 3 H]dopamine uptake. Consistent with increased [ 3 H]WIN 35428 binding, dopamine transporter-specific [ 3 H]dopamine uptake in RGS12-null ventral striatal synaptosomes was found to be increased. Decreased amphetamine-induced locomotor activity and increased [ 3 H]WIN 35428 binding were recapitulated with an independent RGS12-null mouse strain. Thus, we propose that RGS12 regulates dopamine transporter expression and function in the ventral striatum, affecting amphetamine- and cocaine-induced increases in dopamine levels that specifically elicit acute hyperlocomotor responses.

Species differences in somatodendritic dopamine transmission determine D2-autoreceptor mediated inhibition of ventral tegmental area neuron firing

PubMed Central

Courtney, Nicholas A; Mamaligas, Aphroditi A; Ford, Christopher P

2012-01-01

The somatodendritic release of dopamine within the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) activates inhibitory post-synaptic D2-receptors on dopaminergic neurons. The proposed mechanisms that regulate this form of transmission differ between electrochemical studies using rats and guinea pigs and electrophysiological studies using mice. This study examines the release and resulting dopamine D2-autoreceptor mediated inhibitory post-synaptic currents (D2-IPSCs) in the VTA of mouse, rat and guinea pig. Robust D2-IPSCs were observed in all recordings from neurons in slices taken from mouse, whereas in rat and guinea pig D2-IPSCs were observed less frequently and were significantly smaller in amplitude. In slices taken from guinea pig, dopamine release was more persistent under conditions of reduced extracellular calcium. The decline in the concentration of dopamine was also prolonged and not as sensitive to inhibition of reuptake by cocaine. This resulted in an increased duration of D2-IPSCs in the guinea pig. Therefore, unlike the mouse or the rat, the time course of dopamine in the extracellular space of the guinea pig determined the duration the D2-IPSC. Functionally, differences in D2-IPSCs resulted in inhibition of dopamine neuron firing only in slices from mouse. The results suggest that the mechanisms and functional consequences of somatodendritic dopamine transmission in the VTA vary among species. This highlights the complexity that underlies dopamine dependent transmission in one brain area. Differences in somatodendritic transmission would be expected in vivo to affect the downstream activity of the mesocorticolimbic dopamine system and subsequent terminal release. PMID:23015441

Effects of chemical sympathectomy on the increases in plasma catecholamines and dopamine-beta-hydroxylase induced by forced immobilization and insulin-induced hypoglycemia: origin and fate of plasma dopamine-beta-hydroxylase.

PubMed

Israel, A S; Barbella, Y R; Cubeddu, L X

1982-06-01

The effect of acute stresses on plasma norepinephrine, epinephrine and dopamine-beta-hydroxylase (DBH) were evaluated in control and 6-hydroxydopamine-treated, awake cannulated guinea pigs. Forced immobolization for 1 hr caused a 3- and 5-fold increase in plasma DBH and norepinephrine, respectively. Pretreatment with 6-hydroxydopamine (23 mg/kg b.wt.i.a., 72 and 48 hr before stress) reduced by 70% the increase in plasma DBH and totally prevented the rise in plasma catecholamines evoked by the restraining stress. Injection of insulin (5 U/kg b.wt.i.a.) induced a 60% decrease in blood glucose, a 1-fold increase in plasma DBH and a selective 4-fold increase in plasma epinephrine; these effects were not modified by chemical sympathectomy. Our results indicate that forced immobilization and hypoglycemia produce a preferential activation of the sympathetic postganglionic nerves and of the adrenal medulla, respectively, and that in guinea pigs both stresses increase plasma DBH. The kinetics of disappearance of plasma DBH were studied after subjecting the guinea pigs for 1 hr to forced immobilization. Although 7 of 12 animals showed a biphasic rate of fall of plasma DBH, in each case there was a rapid initial fall possibly due to the "distribution" of the enzyme with a T1/2 of 1.65 hr. Similar findings were observed in 6-hydroxydopamine-treated guinea pigs. These results suggest that the distribution of DBH is the most important process in reducing the augmented plasma DBH levels elicited by a short-term stress and that this process is not dependent on the integrity of the sympathetic nerves nor on the adrenal or sympathetic origin of the enzyme. This study supports the view that the ratio, content of releasable DBH present in sympathetic nerves and adrenal glands/total circulating pool of DBH, is the factor that determines whether an increase in plasma DBH would occur in animals exposed to an acute stress.

The role of the neuropeptide somatostatin on methamphetamine and glutamate-induced neurotoxicity in the striatum of mice.

PubMed

Afanador, Lauriaselle; Mexhitaj, Ina; Diaz, Carolyn; Ordonez, Dalila; Baker, Lisa; Angulo, Jesus A

2013-05-13

A large body of evidence shows that methamphetamine (METH) causes sustained damage to the brain in animal models and human METH users. In chronic users there are indications of cognitive and motor deficits. Striatal neuropeptides are in a position to modulate the neurochemical effects of METH and consequently striatal neural damage. Somatostatin (SST) is an intrinsic striatal neuropeptide that has been shown to inhibit glutamate transmission; glutamate is integral to METH toxicity and contributes to nitric oxide (NO) synthesis. We hypothesize that SST will protect from METH by inhibition of NO synthesis and thus reducing oxidative stress. To this end, the SST analogue octreotide (OCT) was microinjected into the striatum prior to a systemic injection of METH (30mg/kg). We then assessed 3-nitrotyrosine (3-NT), an indirect index of NO production, tyrosine hydroxylase (TH) protein levels (dopamine terminal marker) and Fluoro-Jade C positive cells (degenerating cells). The SST agonist OCT dose dependently attenuated the METH-induced accumulation of striatal 3-NT. Moreover, pretreatment with OCT effectively mitigated cell death but failed to protect dopamine terminals. Next we co-infused OCT and NMDA and measured 3-NT and Fluoro-Jade C staining. Treatment with OCT had no effect on these parameters. The data demonstrate that SST attenuates the METH-induced production of NO protecting the striatum from the METH-induced cell loss. However, SST failed to prevent the toxicity of the dopamine terminals suggesting that pre- and post-synaptic striatal damage occur via independent mechanisms. Copyright © 2013 Elsevier B.V. All rights reserved.

The Role of the Neuropeptide Somatostatin on Methamphetamine and Glutamate-Induced Neurotoxicity in the Striatum of Mice

PubMed Central

Afanador, Lauriaselle; Mexhitaj, Ina; Diaz, Carolyn; Ordonez, Dalila; Baker, Lisa; Angulo, Jesus A.

2014-01-01

A large body of evidence shows that methamphetamine (METH) causes sustained damage to the brain in animal models and human METH users. In chronic users there are indications of cognitive and motor deficits. Striatal neuropeptides are in a position to modulate the neurochemical effects of METH and consequently striatal neural damage. Somatostatin (SST) is an intrinsic striatal neuropeptide that has been shown to inhibit glutamate transmission; glutamate is integral to METH toxicity and contributes to nitric oxide (NO) synthesis. We hypothesize that SST will protect from METH by inhibition of NO synthesis and thus reducing oxidative stress. To this end, the SST analogue octreotide (OCT) was microinjected into the striatum prior to a systemic injection of METH (30 mg/kg). We then assessed 3-nitrotyrosine (3-NT), an indirect index of NO production, tyrosine hydroxylase (TH) protein levels (dopamine terminal marker) and Fluoro-Jade C positive cells (degenerating cells). The SST agonist OCT dose dependently attenuated the METH-induced accumulation of striatal 3-NT. Moreover, pretreatment with OCT effectively mitigated cell death but failed to protect dopamine terminals. Next we co-infused OCT and NMDA and measured 3-NT and Fluoro-Jade C staining. Treatment with OCT had no effect on these parameters. The data demonstrate that SST attenuates the METH-induced production of NO protecting the striatum from the METH-induced cell loss. However, SST failed to prevent the toxicity of the dopamine terminals suggesting that pre- and post-synaptic striatal damage occur via independent mechanisms. PMID:23524190

MK-801 protection against methamphetamine-induced striatal dopamine terminal injury is associated with attenuated dopamine overflow.

PubMed

Weihmuller, F B; O'Dell, S J; Marshall, J F

1992-06-01

Repeated administrations of methamphetamine (m-AMPH) produce high extracellular levels of dopamine (DA) and subsequent striatal DA terminal damage. Pharmacological blockade of N-methyl-D-aspartate (NMDA) receptors has been shown previously to prevent m-AMPH-induced striatal DA terminal injury, but the mechanism for this protection is unclear. In the present study, in vivo microdialysis was used to determine the effects of blockade of NMDA receptors with the noncompetitive antagonist MK-801 on m-AMPH-induced striatal DA overflow. Four injections of MK-801 (0.5 mg/kg, ip) alone did not significantly change extracellular striatal DA concentrations from pretreatment values. Four treatments with m-AMPH (4.0 mg/kg, sc at 2-hr intervals) increased striatal DA overflow, and the overflow was particularly extensive following the fourth injection. This m-AMPH regimen produced a 40% reduction in striatal DA tissue content 1 week later. Treatment with MK-801 15 min before each of the four m-AMPH injections or prior to only the last two m-AMPH administrations attenuated the m-AMPH-induced increase in striatal DA overflow and protected completely against striatal DA depletions. Other MK-801 treatment regimens less effectively reduced the m-AMPH-induced striatal DA efflux and were ineffective in protecting against striatal DA depletions. Linear regression analysis indicated that cumulative DA overflow was strongly predictive (r = -.68) of striatal DA tissue levels measured one week later. These findings suggest that the extensive DA overflow seen during a neurotoxic regimen of m-AMPH is a crucial component of the subsequent neurotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Iatrogenic nerve injuries during shoulder surgery.

PubMed

Carofino, Bradley C; Brogan, David M; Kircher, Michelle F; Elhassan, Bassem T; Spinner, Robert J; Bishop, Allen T; Shin, Alexander Y

2013-09-18

The current literature indicates that neurologic injuries during shoulder surgery occur infrequently and result in little if any morbidity. The purpose of this study was to review one institution's experience treating patients with iatrogenic nerve injuries after shoulder surgery. A retrospective review of the records of patients evaluated in a brachial plexus specialty clinic from 2000 to 2010 identified twenty-six patients with iatrogenic nerve injury secondary to shoulder surgery. The records were reviewed to determine the operative procedure, time to presentation, findings on physical examination, treatment, and outcome. The average age was forty-three years (range, seventeen to seventy-two years), and the average delay prior to referral was 5.4 months (range, one to fifteen months). Seven nerve injuries resulted from open procedures done to treat instability; nine, from arthroscopic surgery; four, from total shoulder arthroplasty; and six, from a combined open and arthroscopic operation. The injury occurred at the level of the brachial plexus in thirteen patients and at a terminal nerve branch in thirteen. Fifteen patients (58%) did not recover nerve function after observation and required surgical management. A structural nerve injury (laceration or suture entrapment) occurred in nine patients (35%), including eight of the thirteen who presented with a terminal nerve branch injury and one of the thirteen who presented with an injury at the level of the brachial plexus. Nerve injuries occurring during shoulder surgery can produce severe morbidity and may require surgical management. Injuries at the level of a peripheral nerve are more likely to be surgically treatable than injuries of the brachial plexus. A high index of suspicion and early referral and evaluation should be considered when evaluating patients with iatrogenic neurologic deficits after shoulder surgery.

Thiol-yne click reactions on alkynyl-dopamine-modified reduced graphene oxide.

PubMed

Kaminska, Izabela; Qi, Wang; Barras, Alexandre; Sobczak, Janusz; Niedziolka-Jonsson, Joanna; Woisel, Patrice; Lyskawa, Joel; Laure, William; Opallo, Marcin; Li, Musen; Boukherroub, Rabah; Szunerits, Sabine

2013-06-24

The large-scale preparation of graphene is of great importance due to its potential applications in various fields. We report herein a simple method for the simultaneous exfoliation and reduction of graphene oxide (GO) to reduced GO (rGO) by using alkynyl-terminated dopamine as the reducing agent. The reaction was performed under mild conditions to yield rGO functionalized with the dopamine derivative. The chemical reactivity of the alkynyl function was demonstrated by post-functionalization with two thiolated precursors, namely 6-(ferrocenyl)hexanethiol and 1H,1H,2H,2H-perfluorodecanethiol. X-ray photoelectron spectroscopy, UV/Vis spectrophotometry, Raman spectroscopy, conductivity measurements, and cyclic voltammetry were used to characterize the resulting surfaces. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chronic cocaine disrupts mesocortical learning mechanisms

PubMed Central

Buchta, William C.; Riegel, Arthur C.

2016-01-01

The addictive power of drugs of abuse such as cocaine comes from their ability to hijack natural reward and plasticity mechanisms mediated by dopamine signaling in the brain. Reward learning involves burst firing of midbrain dopamine neurons in response to rewards and cues predictive of reward. The resulting release of dopamine in terminal regions is thought to act as a teaching signaling to areas such as the prefrontal cortex and striatum. In this review, we posit that a pool of extrasynaptic dopaminergic D1-like receptors activated in response to dopamine neuron burst firing serve to enable synaptic plasticity in the prefrontal cortex in response to rewards and their cues. We propose that disruptions in these mechanisms following chronic cocaine use contribute to addiction pathology, in part due to the unique architecture of the mesocortical pathway. By blocking dopamine reuptake in the cortex, cocaine elevates dopamine signaling at these extra-synaptic receptors, prolonging D1-receptor activation and the subsequent activation of intracellular signaling cascades, and thus inducing long-lasting maladaptive plasticity. These cellular adaptations may account for many of the changes in cortical function observed in drug addicts, including an enduring vulnerability to relapse. Therefore, understanding and targeting these neuroadaptations may provide cognitive benefits and help prevent relapse in human drug addicts. PMID:25704202

Effects of asarinin on dopamine biosynthesis and 6-hydroxydopamine-induced cytotoxicity in PC12 cells.

PubMed

Park, Hyun Jin; Lee, Kyung Sook; Zhao, Ting Ting; Lee, Kyung Eun; Lee, Myung Koo

2017-05-01

This study investigated the effects of asarinin on dopamine biosynthesis and 6-hydroxydopamine (6-OHDA)-induced cytotoxicity in rat adrenal pheochromocytoma (PC12) cells. Treatment with asarinin (25-50 μM) increased intracellular dopamine levels and enhanced L-DOPA-induced increases in dopamine levels. Asarinin (25 μM) induced cyclic AMP-dependent protein kinase A (PKA) signaling, leading to increased cyclic AMP-response element binding protein (CREB) and tyrosine hydroxylase (TH) phosphorylation, which in turn stimulated dopamine production. Asarinin (25 μM) also activated transient phosphorylation of extracellular signal-regulated kinase (ERK1/2) and Bad phosphorylation at Ser 112, both of which have been shown to promote cell survival. In contrast, asarinin (25 μM) inhibited sustained ERK1/2, Bax, c-Jun N-terminal kinase (JNK1/2) and p38 mitogen-activated protein kinase (p38MAPK) phosphorylation and caspase-3 activity, which were induced by 6-OHDA (100 μM). These results suggest that asarinin induces dopamine biosynthesis via activation of the PKA-CREB-TH system and protects against 6-OHDA-induced cytotoxicity by inhibiting the sustained activation of the ERK-p38MAPK-JNK1/2-caspase-3 system in PC12 cells.

Molecular characteristics suggest an effector function of palisade endings in extraocular muscles.

PubMed

Konakci, Kadriye Zeynep; Streicher, Johannes; Hoetzenecker, Wolfram; Blumer, Michael Josef Franz; Lukas, Julius-Robert; Blumer, Roland

2005-01-01

To analyze palisade endings in cat extraocular muscles (EOMs) and to clarify whether these EOM-specific organs are sensory or motor. Twelve cats aged between 1 and 16 years were analyzed. Whole EOM tendons were immunostained using four different combinations of triple fluorescence labeling. Triple labeling included antibodies against choline acetyltransferase (ChAT), neurofilament, synaptophysin, and alpha-bungarotoxin. Preparations were examined by confocal laser scanning microscopy. ChAT-labeled EOMs were also analyzed by immunoelectron microscopy. Three-dimensional reconstructions were made of palisade endings. Palisade endings were found in the distal and proximal myotendinous regions of cat EOMs. These endings arose from thin nerve fibers coming from the muscle and extending into the tendon. There, the nerve fibers turned back 180 degrees to divide into terminal branches around the muscle fiber tips. Terminal branches established numerous contacts with the tendon attached to the muscle fiber tip and only a few contacts with the muscle fiber. Often, nerve fibers forming palisade endings on muscle fiber tips were observed to establish multiple motor contacts on muscle fibers outside palisade endings. Three-dimensional reconstructions depicted the complex morphology of the palisade endings. All nerve fibers supplying palisade endings stained positively for ChAT and neurofilament. All nerve terminals in palisade endings were ChAT and synaptophysin positive. Only neuromuscular contacts in palisade endings were positive for alpha-bungarotoxin, as well. This study provides evidence that palisade endings in cat EOMs have effector function. The findings may be of significance for strabismus surgery because palisade endings are also found in human EOMs.

1,2,3,4-Tetrahydroisoquinoline protects terminals of dopaminergic neurons in the striatum against the malonate-induced neurotoxicity.

PubMed

Lorenc-Koci, Elzbieta; Gołembiowska, Krystyna; Wardas, Jadwiga

2005-07-27

Malonate, a reversible inhibitor of the mitochondrial enzyme succinate dehydrogenase, is frequently used as a model neurotoxin to produce lesion of the nigrostriatal dopaminergic system in animals due to particular sensitivity of dopamine neurons to mild energy impairment. This model of neurotoxicity was applied in our study to explore neuroprotective potential of 1,2,3,4-tetrahydroisoquinoline (TIQ), an endo- and exogenous substance whose function in the mammalian brain, despite extensive studies, has not been elucidated so far. Injection of malonate at a dose of 3 mumol unilaterally into the rat left medial forebrain bundle resulted in the 54% decrease in dopamine (DA) concentration in the ipsilateral striatum and, depending on the examined striatum regions, caused 24-44% reduction in [3H]GBR12,935 binding to the dopamine transporter (DAT). TIQ (50 mg/kg i.p.) administered 4 h before malonate infusion and next once daily for successive 7 days prevented both these effects of malonate. Such TIQ treatment restored DA content and DAT binding almost to the control level. The results of the present study indicate that TIQ may act as a neuroprotective agent in the rat brain. An inhibition of the enzymatic activities of monoamine oxidase and gamma-glutamyl transpeptidase as well as an increase in the striatal levels of glutathione and nitric oxide found after TIQ administration and reported in our earlier studies are considered to be potential factors that may be involved in the TIQ-mediated protection of dopamine terminals from malonate toxicity.

Functional Fast Scan Cyclic Voltammetry Assay to Characterize Dopamine D2 and D3 Autoreceptors in the Mouse Striatum

PubMed Central

2010-01-01

Dopamine D2 and D3 autoreceptors are located on presynaptic terminals and are known to control the release and synthesis of dopamine. Dopamine D3 receptors have a fairly restricted pattern of expression in the mammalian brain. Their localization in the nucleus accumbens core and shell is of particular interest because of their association with the rewarding properties of drugs of abuse. Using background subtracted fast scan cyclic voltammetry, we investigated the effects of dopamine D2 and D3 agonists on electrically stimulated dopamine release and uptake rates in the mouse caudate putamen and nucleus accumbens core and shell. The dopamine D2 agonists (−)-quinpirole hydrochloride and 5,6,7,8-tetrahydro-6-(2-propen-1-yl)-4H-thiazolo[4,5-d]azepin-2-amine dihydrochloride (B-HT 920) had the same dopamine release inhibition effects on caudate putamen and nucleus accumbens (core and shell) on the basis of their EC50 values and efficacies. This suggests that the dopamine D2 autoreceptor functionality is comparable in all three striatal regions investigated. The dopamine D3 agonists (4aR,10bR)-3,4a,4,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol hydrochloride ((+)-PD 128907) and (±)-7-Hydroxy-2-dipropylaminotetralin hydrobromide (7-OH-DPAT) had a significantly greater effect on dopamine release inhibition in the nucleus accumbens shell than in the caudate putamen. This study confirms that, the dopamine D3 autoreceptor functionality is greater in the nucleus accumbens shell followed by the nucleus accumbens core, with the caudate putamen having the least. Neither dopamine D2 nor D3 agonists affected the uptake rates in nucleus accumbens but concentrations greater than 0.1 μM lowered the uptake rate in caudate putamen. To validate our method of evaluating dopamine D2 and D3 autoreceptors, sulpiride (D2 antagonist) and nafadotride (D3 antagonist) were used to reverse the effects of the dopamine agonists to approximately 100% of the preagonist dopamine release concentration. Finally, these results demonstrate a functional voltammetric assay that characterizes dopamine D2-like agonists as either D2- or D3-preferring agonists by taking advantage of the unique receptor density within the striatum. PMID:20567609

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

C-11 hydroxy ephedrine, introduced as the first clinically usable norepinephrine analogue, studies employing normal volunteers and patients with various cardiac disorders was found to valuable as a nonadreneric tracer. Simultaneously, animal studies been used to assess its use following ischemic injury in order to define neuronal damage. Current research focuses on the comparison of C-11 hydroxyephedrine with other neurotransmitters such as C-11 epinephrine and C-11 threohydroxyephedrine. Epinephrine is primarily stored in vesicles of the nerve terminal, while threo-hydroxyephedrine is only substrate to uptake I mechanism. Such a combination of radiotracers may allow the dissection of uptake I mechanism as wellmore » as vesicular storage. In parallel to the refinement of presynaptic tracers for the sympathetic nervous system, we are developing radiopharmaceuticals to delineate the adrenergic receptors in the heart. The combined evaluation of pre- and postsynaptic nerve function will improve our ability to identify abnormalides. We are currently developing a new radiosynthesis of the hydrophilic adrenergic receptor antagonist C-11 CGP-12177 which has been used by others for the visualization of adrenergic receptors in the heart. We are developing radiopharmaceuticals, for the delineation of presynaptic cholinergic nerve terminals. Derivatives of benzovesamicol have been labeled in our institution and are currently under investigation. The most promising agent is F-18 benzovesamicol (FEBOBV) which allows the visualization of parasympathetic nerve terminals in the canine heart as demonstrated by, preliminary PET data.« less

Presynaptic Proteins as Markers of the Neurotoxic Activity of BmjeTX-I and BmjeTX-II Toxins from Bothrops marajoensis (Marajó Lancehead) Snake Venom.

PubMed

Lisboa, Antonio; Melaré, Rodolfo; Franco, Junia R B; Bis, Carolina V; Gracia, Marta; Ponce-Soto, Luis A; Marangoni, Sérgio; Rodrigues-Simioni, Léa; da Cruz-Höfling, Maria Alice; Rocha, Thalita

2016-01-01

Neuromuscular preparations exposed to B. marajoensis venom show increases in the frequency of miniature end-plate potentials and twitch tension facilitation followed by presynaptic neuromuscular paralysis, without evidences of muscle damage. Considering that presynaptic toxins interfere into the machinery involved in neurotransmitter release (synaptophysin, synaptobrevin, and SNAP25 proteins), the main objective of this communication is to analyze, by immunofluorescence and western blotting, the expression of the synaptic proteins, synaptophysin, synaptobrevin, and SNAP25 and by myography, light, and transmission electron microscopy the pathology of motor nerve terminals and skeletal muscle fibres of chick biventer cervicis preparations (CBC) exposed in vitro to BmjeTX-I and BmjeTX-II toxins from B. marajoensis venom. CBC incubated with toxins showed irreversible twitch tension blockade and unaffected KCl- and ACh-evoked contractures, and the positive colabelling of acetylcholine receptors confirmed that their action was primarily at the motor nerve terminal. Hypercontraction and loose myofilaments and synaptic vesicle depletion and motor nerve damage indicated that the toxins displayed both myotoxic and neurotoxic effect. The blockade resulted from interference on synaptophysin, synaptobrevin, and SNAP25 proteins leading to the conclusion that BmjeTX-I and BmjeTX-II affected neurotransmitter release machinery by preventing the docking of synaptic vesicles to the axolemma of the nerve terminal.

Different role of TTX-sensitive voltage-gated sodium channel (NaV 1) subtypes in action potential initiation and conduction in vagal airway nociceptors.

PubMed

Kollarik, M; Sun, H; Herbstsomer, R A; Ru, F; Kocmalova, M; Meeker, S N; Undem, B J

2018-04-15

The action potential initiation in the nerve terminals and its subsequent conduction along the axons of afferent nerves are not necessarily dependent on the same voltage-gated sodium channel (Na V 1) subunits. The action potential initiation in jugular C-fibres within airway tissues is not blocked by TTX; nonetheless, conduction of action potentials along the vagal axons of these nerves is often dependent on TTX-sensitive channels. This is not the case for nodose airway Aδ-fibres and C-fibres, where both action potential initiation and conduction is abolished by TTX or selective Na V 1.7 blockers. The difference between the initiation of action potentials within the airways vs. conduction along the axons should be considered when developing Na V 1 blocking drugs for topical application to the respiratory tract. The action potential (AP) initiation in the nerve terminals and its subsequent AP conduction along the axons do not necessarily depend on the same subtypes of voltage-gated sodium channels (Na V 1s). We evaluated the role of TTX-sensitive and TTX-resistant Na V 1s in vagal afferent nociceptor nerves derived from jugular and nodose ganglia innervating the respiratory system. Single cell RT-PCR was performed on vagal afferent neurons retrogradely labelled from the guinea pig trachea. Almost all of the jugular neurons expressed the TTX-sensitive channel Na V 1.7 along with TTX-resistant Na V 1.8 and Na V 1.9. Tracheal nodose neurons also expressed Na V 1.7 but, less frequently, Na V 1.8 and Na V 1.9. Na V 1.6 were expressed in ∼40% of the jugular and 25% of nodose tracheal neurons. Other Na V 1 α subunits were only rarely expressed. Single fibre recordings were made from the vagal nodose and jugular nerve fibres innervating the trachea or lung in the isolated perfused vagally-innervated preparations that allowed for selective drug delivery to the nerve terminal compartment (AP initiation) or to the desheathed vagus nerve (AP conduction). AP initiation in jugular C-fibres was unaffected by TTX, although it was inhibited by Na V 1.8 blocker (PF-01247324) and abolished by combination of TTX and PF-01247324. However, AP conduction in the majority of jugular C-fibres was abolished by TTX. By contrast, both AP initiation and conduction in nodose nociceptors was abolished by TTX or selective Na V 1.7 blockers. Distinction between the effect of a drug with respect to inhibiting AP in the nerve terminals within the airways vs. at conduction sites along the vagus nerve is relevant to therapeutic strategies involving inhaled Na V 1 blocking drugs. © 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society.

Lentiviral-mediated transfer of CDNF promotes nerve regeneration and functional recovery after sciatic nerve injury in adult rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Lei; Liu, Yi; Zhao, Hua

Highlights: •CDNF was successfully transfected by a lentiviral vector into the distal sciatic nerve. •CDNF improved S-100, NF200 expression and nerve regeneration after sciatic injury. •CDNF improved the remyelination and thickness of the regenerated sciatic nerve. •CDNF improved gastrocnemius muscle weight and sciatic functional recovery. -- Abstract: Peripheral nerve injury is often followed by incomplete and unsatisfactory functional recovery and may be associated with sensory and motor impairment of the affected limb. Therefore, a novel method is needed to improve the speed of recovery and the final functional outcome after peripheral nerve injuries. This report investigates the effect of lentiviral-mediatedmore » transfer of conserved dopamine neurotrophic factor (CDNF) on regeneration of the rat peripheral nerve in a transection model in vivo. We observed notable overexpression of CDNF protein in the distal sciatic nerve after recombinant CDNF lentiviral vector application. We evaluated sciatic nerve regeneration after surgery using light and electron microscopy and the functional recovery using the sciatic functional index and target muscle weight. HE staining revealed better ordered structured in the CDNF-treated group at 8 weeks post-surgery. Quantitative analysis of immunohistochemistry of NF200 and S-100 in the CDNF group revealed significant improvement of axonal and Schwann cell regeneration compared with the control groups at 4 weeks and 8 weeks after injury. The thickness of the myelination around the axons in the CDNF group was significantly higher than in the control groups at 8 weeks post-surgery. The CDNF group displayed higher muscle weights and significantly increased sciatic nerve index values. Our findings suggest that CDNF gene therapy could provide durable and stable CDNF protein concentration and has the potential to enhance peripheral nerve regeneration, morphological and functional recovery following nerve injury, which suggests a promising strategy for peripheral nerve repair.« less

Midbrain dopamine function in schizophrenia and depression: a post-mortem and positron emission tomographic imaging study.

PubMed

Howes, Oliver D; Williams, Matthew; Ibrahim, Kemal; Leung, Garret; Egerton, Alice; McGuire, Philip K; Turkheimer, Federico

2013-11-01

Elevated in vivo markers of presynaptic striatal dopamine activity have been a consistent finding in schizophrenia, and include a large effect size elevation in dopamine synthesis capacity. However, it is not known if the dopaminergic dysfunction is limited to the striatal terminals of dopamine neurons, or is also evident in the dopamine neuron cell bodies, which mostly originate in the substantia nigra. The aim of our studies was therefore to determine whether dopamine synthesis capacity is altered in the substantia nigra of people with schizophrenia, and how this relates to symptoms. In a post-mortem study, a semi-quantitative analysis of tyrosine hydroxylase staining was conducted in nigral dopaminergic cells from post-mortem tissue from patients with schizophrenia (n = 12), major depressive disorder (n = 13) and matched control subjects (n = 13). In an in vivo imaging study, nigral and striatal dopaminergic function was measured in patients with schizophrenia (n = 29) and matched healthy control subjects (n = 29) using (18)F-dihydroxyphenyl-L-alanine ((18)F-DOPA) positron emission tomography. In the post-mortem study we found that tyrosine hydroxylase staining was significantly increased in nigral dopaminergic neurons in schizophrenia compared with both control subjects (P < 0.001) and major depressive disorder (P < 0.001). There was no significant difference in tyrosine hydroxylase staining between control subjects and patients with major depressive disorder, indicating that the elevation in schizophrenia is not a non-specific indicator of psychiatric illness. In the in vivo imaging study we found that (18)F-dihydroxyphenyl-L-alanine uptake was elevated in both the substantia nigra and in the striatum of patients with schizophrenia (effect sizes = 0.85, P = 0.003 and 1.14, P < 0.0001, respectively) and, in the voxel-based analysis, was elevated in the right nigra (P < 0.05 corrected for family wise-error). Furthermore, nigral (18)F-dihydroxyphenyl-L-alanine uptake was positively related with the severity of symptoms (r = 0.39, P = 0.035) in patients. However, whereas nigral and striatal (18)F-dihydroxyphenyl-L-alanine uptake were positively related in control subjects (r = 0.63, P < 0.001), this was not the case in patients (r = 0.30, P = 0.11). These findings indicate that elevated dopamine synthesis capacity is seen in the nigral origin of dopamine neurons as well as their striatal terminals in schizophrenia, and is linked to symptom severity in patients.

Stochastic Simulation of Dopamine Neuromodulation for Implementation of Fluorescent Neurochemical Probes in the Striatal Extracellular Space.

PubMed

Beyene, Abraham G; McFarlane, Ian R; Pinals, Rebecca L; Landry, Markita P

2017-10-18

Imaging the dynamic behavior of neuromodulatory neurotransmitters in the extracelluar space that arise from individual quantal release events would constitute a major advance in neurochemical imaging. Spatial and temporal resolution of these highly stochastic neuromodulatory events requires concurrent advances in the chemical development of optical nanosensors selective for neuromodulators in concert with advances in imaging methodologies to capture millisecond neurotransmitter release. Herein, we develop and implement a stochastic model to describe dopamine dynamics in the extracellular space (ECS) of the brain dorsal striatum to guide the design and implementation of fluorescent neurochemical probes that record neurotransmitter dynamics in the ECS. Our model is developed from first-principles and simulates release, diffusion, and reuptake of dopamine in a 3D simulation volume of striatal tissue. We find that in vivo imaging of neuromodulation requires simultaneous optimization of dopamine nanosensor reversibility and sensitivity: dopamine imaging in the striatum or nucleus accumbens requires nanosensors with an optimal dopamine dissociation constant (K d ) of 1 μM, whereas K d s above 10 μM are required for dopamine imaging in the prefrontal cortex. Furthermore, as a result of the probabilistic nature of dopamine terminal activity in the striatum, our model reveals that imaging frame rates of 20 Hz are optimal for recording temporally resolved dopamine release events. Our work provides a modeling platform to probe how complex neuromodulatory processes can be studied with fluorescent nanosensors and enables direct evaluation of nanosensor chemistry and imaging hardware parameters. Our stochastic model is generic for evaluating fluorescent neurotransmission probes, and is broadly applicable to the design of other neurotransmitter fluorophores and their optimization for implementation in vivo.

Endoplasmic Reticulum Stress as a Mediator of Neurotoxin-Induced Dopamine Neuron Death

DTIC Science & Technology

2006-07-01

reversible reduction in choline acetyl- transferase concentration in rat hypoglossal nucleus after hypoglossal nerve transection. Nature 275, 324–325...cally, analogs were evaluated for their ability to enhance choline acetyltransferase (ChAT) activity in embryonic rat spinal cord and basal forebrain...of ibotenate, CEP1347 protected basal forebrain cholinergic neurons.102 In a model of apoptosis induced in auditory hair cells by noise trauma, CEP1347

Semi-quantitative ultrastructural analysis of the localization and neuropeptide content of gonadotropin releasing hormone nerve terminals in the median eminence throughout the estrous cycle of the rat.

PubMed

Prevot, V; Dutoit, S; Croix, D; Tramu, G; Beauvillain, J C

1998-05-01

The ultrastructural appearance of gonadotropin releasing hormone-immunoreactive elements was studied in the external zone of the median eminence of adult female Wistar rats. On the one hand, the purpose of the study was to determine the distribution of gonadotropin releasing hormone terminals towards the parenchymatous basal lamina at the level of hypothalamo-hypophyseal portal vessels, throughout the estrous cycle. On the other hand, we have semi-quantified the gonadotropin releasing hormone content in nerve terminals or preterminals during this physiological condition. A morphometric study was coupled to a colloidal 15 mn gold postembedding immunocytochemistry procedure. Animals were killed at 09.00 on diestrus II, 0.900, 10.00, 13.00, 17.00 and 18.00 on proestrus and 09.00 on estrus (n = 4-8 rats/group). A preliminary light microscopic study was carried out to identify an antero-posterior part of median eminence strongly immunostained by anti-gonadotropin releasing hormone antibodies but which was, in addition, easily spotted. This last condition was necessary to make a good comparison between each animal. Contacts between gonadotropin releasing hormone nerve terminals and the basal lamina were observed only the day of proestrus. Such contacts, however, were rare and in the great majority of cases, gonadotropin releasing hormone terminals are separated from basal lamina by tanycytic end feet. The morphometric analysis showed no significant variation in average distance between gonadotropin releasing hormone terminals and capillaries throughout the estrous cycle. Consequently, it did not appear that a large neuroglial plasticity exists during the estrous cycle. However, the observation of contacts only on proestrus together with some ultrastructural images evoke the possibility of a slight plasticity. The semi-quantitative results show that the content of gonadotropin releasing hormone in the nerve endings presented two peaks on proestrus: one at 09.00 (23 +/- 5 particles/micrograms2, P < 0.03) before the onset of luteinizing hormone surge, and the second at 18.00 (16 +/- 2 particles/micrograms2, P < 0.01) concomitantly with the luteinizing hormone surge, when compared to baseline values on proestrus 10.00 (8 +/- particles/micrograms2).

Functional maturation of motor nerve terminals in the avian iris: ultrastructure, transmitter metabolism and synaptic reliability

PubMed Central

Pilar, Guillermo; Tuttle, Jeremy; Vaca, Ken

1981-01-01

1. The transformation of easily fatigued embryonic neuromuscular junctions into highly reliable mature terminals was examined by studying functional and morphological changes during development of the avian iris. The mature ability to follow repetitive electrical nerve stimulation was correlated with the rate of acetylcholine (ACh) synthesis and choline uptake, and with the fine structure of the nerve terminals and the post-synaptic elements. 2. The terminals of the ciliary nerve of the chick initially form functional synaptic contacts with the iris muscle at embryonic St. 34-40. At the onset of this period, no Na+-dependent high affinity choline uptake can be demonstrated, and the low level of ACh synthesis present is sensitive to Na+ removal. At St. 36 [3H]ACh synthesis begins to increase, the increment being Na+-dependent. 3. ACh synthesis in the embryonic iris was insensitive to a conditioning [K+]o depolarization even as late as St. 43. Just before hatching, depolarization elicits some augmentation in synthesis, but by 2 days ex ovo this release-induced response has increased by an order of magnitude. 4. Concurrently with the acquisition of the ability to respond to depolarization with accelerated synthesis, neuromuscular transmission in the iris becomes reliable and secure during stimulation at 20 Hz. Embryonic junctions rapidly block during such stimulation, and the failure is shown to be presynaptic in origin, resulting most probably from failure to sustain adequate levels of transmitter release. 5. Ultrastructural examination of the developing ciliary terminals revealed few synaptic vesicles at early stages, and a dearth of other specializations. The sequence of development from these small structurally undistinguished endings to large en plaque junctions completely filled with vesicles was reconstructed and compared to other neuromuscular junctions. Morphological maturation appears progressive with little evidence of discontinuity signalling functional status, but it is only after the terminals enlarge and become closely packed with vesicles that mature synaptic reliability is found. 6. The temporal correlation between responsiveness of transmitter synthesis to depolarization and reliable neuromuscular transmission suggests that modulation of neurotransmitter metabolism in response to demand signals the achievement of junctional maturity. ImagesABPlate 2Plate 3Plate 4 PMID:6279822

Genome-wide association study of aggressive behaviour in chicken.

PubMed

Li, Zhenhui; Zheng, Ming; Abdalla, Bahareldin Ali; Zhang, Zhe; Xu, Zhenqiang; Ye, Qiao; Xu, Haiping; Luo, Wei; Nie, Qinghua; Zhang, Xiquan

2016-08-03

In the poultry industry, aggressive behaviour is a large animal welfare issue all over the world. To date, little is known about the underlying genetics of the aggressive behaviour. Here, we performed a genome-wide association study (GWAS) to explore the genetic mechanism associated with aggressive behaviour in chickens. The GWAS results showed that a total of 33 SNPs were associated with aggressive behaviour traits (P < 4.6E-6). rs312463697 on chromosome 4 was significantly associated with aggression (P = 2.10905E-07), and it was in the intron region of the sortilin-related VPS10 domain containing receptor 2 (SORCS2) gene. In addition, biological function analysis of the nearest 26 genes around the significant SNPs was performed with Ingenuity Pathway Analysis. An interaction network contained 17 genes was obtained and SORCS2 was involved in this network, interacted with nerve growth factor (NGF), nerve growth factor receptor (NGFR), dopa decarboxylase (L-dopa) and dopamine. After knockdown of SORCS2, the mRNA levels of NGF, L-dopa and dopamine receptor genes DRD1, DRD2, DRD3 and DRD4 were significantly decreased (P < 0.05). In summary, our data indicated that SORCS2 might play an important role in chicken aggressive behaviour through the regulation of dopaminergic pathways and NGF.

Dopamine quinones activate microglia and induce a neurotoxic gene expression profile: relationship to methamphetamine-induced nerve ending damage.

PubMed

Kuhn, Donald M; Francescutti-Verbeem, Dina M; Thomas, David M

2006-08-01

Methamphetamine (METH) intoxication leads to persistent damage of dopamine (DA) nerve endings of the striatum. Recently, we and others have suggested that the neurotoxicity associated with METH is mediated by extensive microglial activation. DA itself has been shown to play an obligatory role in METH neurotoxicity, possibly through the formation of quinone species. We show presently that DA-quinones (DAQ) cause a time-dependent activation of cultured microglial cells. Microarray analysis of the effects of DAQ on microglial gene expression revealed that 101 genes were significantly changed in expression, with 73 genes increasing and 28 genes decreasing in expression. Among those genes differentially regulated by DAQ were those often associated with neurotoxic conditions including inflammation, cytokines, chemokines, and prostaglandins. In addition, microglial genes associated with a neuronally protective phenotype were among those that were downregulated by DAQ. These results implicate DAQ as one species that could cause early activation of microglial cells in METH intoxication, manifested as an alteration in the expression of a broad biomarker panel of genes. These results also link oxidative stress, chemical alterations in DA to its quinone, and microglial activation as part of a cascade of glial-neuronal crosstalk that can amplify METH-induced neurotoxicity.

Switch from excitatory to inhibitory actions of ethanol on dopamine levels after chronic exposure: Role of kappa opioid receptors

PubMed Central

Karkhanis, Anushree N.; Huggins, Kimberly N.; Rose, Jamie H.; Jones, Sara R.

2016-01-01

Acute ethanol exposure is known to stimulate the dopamine system; however, chronic exposure has been shown to downregulate the dopamine system. In rodents, chronic intermittent exposure (CIE) to ethanol also increases negative affect during withdrawal, such as, increases in anxiety- and depressive-like behavior. Moreover, CIE exposure results in increased ethanol drinking and preference during withdrawal. Previous literature documents reductions in CIE-induced anxiety-, depressive-like behaviors and ethanol intake in response to kappa opioid receptor (KOR) blockade. KORs are located on presynaptic dopamine terminals in the nucleus accumbens (NAc) and inhibit release, an effect which has been linked to negative affective behaviors. Previous reports show an upregulation in KOR function following extended CIE exposure; however it is not clear whether there is a direct link between KOR upregulation and dopamine downregulation during withdrawal from CIE. This study aimed to examine the effects of KOR modulation on dopamine responses to ethanol of behaving mice exposed to air or ethanol vapor in a repeated intermittent pattern. First, we showed that KORs have a greater response to an agonist after moderate CIE compared to air exposed mice using ex vivo fast scan cyclic voltammetry. Second, using in vivo microdialysis, we showed that, in contrast to the expected increase in extracellular levels of dopamine following an acute ethanol challenge in air exposed mice, CIE exposed mice exhibited a robust decrease in dopamine levels. Third, we showed that blockade of KORs reversed the aberrant inhibitory dopamine response to ethanol in CIE exposed mice while not affecting the air exposed mice demonstrating that inhibition of KORs “rescued” dopamine responses in CIE exposed mice. Taken together, these findings indicate that augmentation of dynorphin/KOR system activity drives the reduction in stimulated (electrical and ethanol) dopamine release in the NAc. Thus, blockade of KORs is a promising avenue for developing pharmacotherapies for alcoholism. PMID:27450094

The metabotropic glutamate receptor activates the lipid kinase PI3K in Drosophila motor neurons through the calcium/calmodulin-dependent protein kinase II and the nonreceptor tyrosine protein kinase DFak.

PubMed

Chun-Jen Lin, Curtis; Summerville, James B; Howlett, Eric; Stern, Michael

2011-07-01

Ligand activation of the metabotropic glutamate receptor (mGluR) activates the lipid kinase PI3K in both the mammalian central nervous system and Drosophila motor nerve terminal. In several subregions of the mammalian brain, mGluR-mediated PI3K activation is essential for a form of synaptic plasticity termed long-term depression (LTD), which is implicated in neurological diseases such as fragile X and autism. In Drosophila larval motor neurons, ligand activation of DmGluRA, the sole Drosophila mGluR, similarly mediates a PI3K-dependent downregulation of neuronal activity. The mechanism by which mGluR activates PI3K remains incompletely understood in either mammals or Drosophila. Here we identify CaMKII and the nonreceptor tyrosine kinase DFak as critical intermediates in the DmGluRA-dependent activation of PI3K at Drosophila motor nerve terminals. We find that transgene-induced CaMKII inhibition or the DFak(CG1) null mutation each block the ability of glutamate application to activate PI3K in larval motor nerve terminals, whereas transgene-induced CaMKII activation increases PI3K activity in motor nerve terminals in a DFak-dependent manner, even in the absence of glutamate application. We also find that CaMKII activation induces other PI3K-dependent effects, such as increased motor axon diameter and increased synapse number at the larval neuromuscular junction. CaMKII, but not PI3K, requires DFak activity for these increases. We conclude that the activation of PI3K by DmGluRA is mediated by CaMKII and DFak.

Central Projections of Antennal and Labial Palp Sensory Neurons in the Migratory Armyworm Mythimna separata

PubMed Central

Ma, Bai-Wei; Zhao, Xin-Cheng; Berg, Bente G.; Xie, Gui-Ying; Tang, Qing-Bo; Wang, Gui-Rong

2017-01-01

The oriental armyworm, Mythimna separata (Walker), is a polyphagous, migratory pest relying on olfactory cues to find mates, locate nectar, and guide long-distance flight behavior. In the present study, a combination of neuroanatomical techniques were utilized on this species, including backfills, confocal microscopy, and three-dimensional reconstructions, to trace the central projections of sensory neurons from the antenna and the labial pit organ, respectively. As previously shown, the axons of the labial sensory neurons project via the ipsilateral labial nerve and terminate in three main areas of the central nervous system: (1) the labial-palp pit organ glomerulus of each antennal lobe, (2) the gnathal ganglion, and (3) the prothoracic ganglion of the ventral nerve cord. Similarly, the antennal sensory axons project to multiple areas of the central nervous system. The ipsilateral antennal nerve targets mainly the antennal lobe, the antennal mechanosensory and motor center, and the prothoracic and mesothoracic ganglia. Specific staining experiments including dye application to each of the three antennal segments indicate that the antennal lobe receives input from flagellar olfactory neurons exclusively, while the antennal mechanosensory and motor center is innervated by mechanosensory neurons from the whole antenna, comprising the flagellum, pedicle, and scape. The terminals in the mechanosensory and motor center are organized in segregated zones relating to the origin of neurons. The flagellar mechanosensory axons target anterior zones, while the pedicular and scapal axons terminate in posterior zones. In the ventral nerve cord, the processes from the antennal sensory neurons terminate in the motor area of the thoracic ganglia, suggesting a close connection with motor neurons. Taken together, the numerous neuropils innervated by axons both from the antenna and labial palp indicate the multiple roles these sensory organs serve in insect behavior. PMID:29209176

Three variations of the laryngeal nerve in the same patient: a case report

PubMed Central

2011-01-01

Introduction A non-recurrent course is a rare anatomic variation of the inferior laryngeal nerve (ILN). Bilateral extra-laryngeal bifurcation of the ILN seldom occurs before its laryngeal entry. Anastomosis between the ILN and cervical sympathetic chain is another rare anatomic feature. The prevalence of extra-laryngeal branching of the non-recurrent nerve is unknown. We present an example of triple anatomic variations of ILNs in the same patient, and also two anatomic variations in the same nerve. Case presentation A 56-year-old Caucasian man with a large toxic multi-nodular goiter was surgically treated with total thyroidectomy. Both his right and left ILNs were identified, fully exposed and preserved along their cervical courses. We discovered many variations during bilateral exploration of the two ILNs. His right ILN was non-recurrent. This non-recurrent ILN showed a terminal division before laryngeal entry. The left nerve had a usual course as a recurrent laryngeal nerve (RLN) at his tracheaesophageal groove. We also discovered bifurcation of his RLN beginning at a neurovascular (RLN and inferior thyroid artery) crossing point. Anterior and posterior branches of both nerves entered his larynx separately. The sympathetic inferior laryngeal anastomotic branch (SILAB) between the posterior branch of his left ILN and the cervical sympathetic chain was established in the distal part of the nerve before laryngeal entry. Conclusion A non-recurrent nerve and extra-laryngeal branching of the ILN are two different variations. The coincidence of a right non-recurrent ILN and bilateral bifurcation of both nerves is a very interesting feature. SILAB is a rare additional finding as a third anatomic variation in the same patient. Extra-laryngeal terminal division of a non-recurrent ILN is an extremely unusual anatomic finding. Two anatomic variations have occurred in the same nerve, like "the variation of the variation". PMID:21722360

Daily Electrical Muscle Stimulation Enhances Functional Recovery Following Nerve Transection and Repair in Rats.

PubMed

Willand, Michael P; Chiang, Cameron D; Zhang, Jennifer J; Kemp, Stephen W P; Borschel, Gregory H; Gordon, Tessa

2015-08-01

Incomplete recovery following surgical reconstruction of damaged peripheral nerves is common. Electrical muscle stimulation (EMS) to improve functional outcomes has not been effective in previous studies. To evaluate the efficacy of a new, clinically translatable EMS paradigm over a 3-month period following nerve transection and immediate repair. Rats were divided into 6 groups based on treatment (EMS or no treatment) and duration (1, 2, or 3 months). A tibial nerve transection injury was immediately repaired with 2 epineurial sutures. The right gastrocnemius muscle in all rats was implanted with intramuscular electrodes. In the EMS group, the muscle was electrically stimulated with 600 contractions per day, 5 days a week. Terminal measurements were made after 1, 2, or 3 months. Rats in the 3-month group were assessed weekly using skilled and overground locomotion tests. Neuromuscular junction reinnervation patterns were also examined. Muscles that received daily EMS had significantly greater numbers of reinnervated motor units with smaller average motor unit sizes. The majority of muscle endplates were reinnervated by a single axon arising from a nerve trunk with significantly fewer numbers of terminal sprouts in the EMS group, the numbers being small. Muscle mass and force were unchanged but EMS improved behavioral outcomes. Our results demonstrated that EMS using a moderate stimulation paradigm immediately following nerve transection and repair enhances electrophysiological and behavioral recovery. © The Author(s) 2014.

Glutamatergic modulation of hyperactivity in mice lacking the dopamine transporter

PubMed Central

Gainetdinov, Raul R.; Mohn, Amy R.; Bohn, Laura M.; Caron, Marc G.

2001-01-01

In the brain, dopamine exerts an important modulatory influence over behaviors such as emotion, cognition, and affect as well as mechanisms of reward and the control of locomotion. The dopamine transporter (DAT), which reuptakes the released neurotransmitter into presynaptic terminals, is a major determinant of the intensity and duration of the dopaminergic signal. Knockout mice lacking the dopamine transporter (DAT-KO mice) display marked changes in dopamine homeostasis that result in elevated dopaminergic tone and pronounced locomotor hyperactivity. A feature of DAT-KO mice is that their hyperactivity can be inhibited by psychostimulants and serotonergic drugs. The pharmacological effect of these drugs occurs without any observable changes in dopaminergic parameters, suggesting that other neurotransmitter systems in addition to dopamine might contribute to the control of locomotion in these mice. We report here that the hyperactivity of DAT-KO mice can be markedly further enhanced when N-methyl-d-aspartate receptor-mediated glutamatergic transmission is blocked. Conversely, drugs that enhance glutamatergic transmission, such as positive modulators of l-α-amino-3-hydroxy-5-methylisoxazole-4-propionate glutamate receptors, suppress the hyperactivity of DAT-KO mice. Interestingly, blockade of N- methyl-d-aspartate receptors prevented the inhibitory effects of both psychostimulant and serotonergic drugs on hyperactivity. These findings support the concept of a reciprocal functional interaction between dopamine and glutamate in the basal ganglia and suggest that agents modulating glutamatergic transmission may represent an approach to manage conditions associated with dopaminergic dysfunction. PMID:11572967

Discrete neurochemical coding of distinguishable motivational processes: insights from nucleus accumbens control of feeding.

PubMed

Baldo, Brian A; Kelley, Ann E

2007-04-01

The idea that nucleus accumbens (Acb) dopamine transmission contributes to the neural mediation of reward, at least in a general sense, has achieved wide acceptance. Nevertheless, debate remains over the precise nature of dopamine's role in reward and even over the nature of reward itself. In the present article, evidence is reviewed from studies of food intake, feeding microstructure, instrumental responding for food reinforcement, and dopamine efflux associated with feeding, which suggests that reward processing in the Acb is best understood as an interaction among distinct processes coded by discrete neurotransmitter systems. In agreement with several theories of Acb dopamine function, it is proposed here that allocation of motor effort in seeking food or food-associated conditioned stimuli can be dissociated from computations relevant to the hedonic evaluation of food during the consummatory act. The former appears to depend upon Acb dopamine transmission and the latter upon striatal opioid peptide release. Moreover, dopamine transmission may play a role in 'stamping in' associations between motor acts and goal attainment and perhaps also neural representations corresponding to rewarding outcomes. Finally, evidence is reviewed that amino acid transmission specifically in the Acb shell acts as a central 'circuit breaker' to flexibly enable or terminate the consummatory act, via descending connections to hypothalamic feeding control systems. The heuristic framework outlined above may help explain why dopamine-compromising manipulations that strongly diminish instrumental goal-seeking behaviors leave consummatory activity relatively unaffected.

Attenuated microglial activation mediates tolerance to the neurotoxic effects of methamphetamine.

PubMed

Thomas, David M; Kuhn, Donald M

2005-02-01

Methamphetamine causes persistent damage to dopamine nerve endings of the striatum. Repeated, intermittent treatment of mice with low doses of methamphetamine leads to the development of tolerance to its neurotoxic effects. The mechanisms underlying tolerance are not understood but clearly involve more than alterations in drug bioavailability or reductions in the hyperthermia caused by methamphetamine. Microglia have been implicated recently as mediators of methamphetamine-induced neurotoxicity. The purpose of the present studies was to determine if a tolerance regimen of methamphetamine would attenuate the microglial response to a neurotoxic challenge. Mice treated with a low-dose methamphetamine tolerance regimen showed minor reductions in striatal dopamine content and low levels of microglial activation. When the tolerance regimen preceded a neurotoxic challenge of methamphetamine, the depletion of dopamine normally seen was significantly attenuated. The microglial activation that occurs after a toxic methamphetamine challenge was blunted likewise. Despite the induction of tolerance against drug-induced toxicity and microglial activation, a neurotoxic challenge with methamphetamine still caused hyperthermia. These results suggest that tolerance to methamphetamine neurotoxicity is associated with attenuated microglial activation and they further dissociate its neurotoxicity from drug-induced hyperthermia.

Neuropeptide Y in the adult and fetal human pineal gland.

PubMed

Møller, Morten; Phansuwan-Pujito, Pansiri; Badiu, Corin

2014-01-01

Neuropeptide Y was isolated from the porcine brain in 1982 and shown to be colocalized with noradrenaline in sympathetic nerve terminals. The peptide has been demonstrated to be present in sympathetic nerve fibers innervating the pineal gland in many mammalian species. In this investigation, we show by use of immunohistochemistry that neuropeptide Y is present in nerve fibers of the adult human pineal gland. The fibers are classical neuropeptidergic fibers endowed with large boutons en passage and primarily located in a perifollicular position with some fibers entering the pineal parenchyma inside the follicle. The distance from the immunoreactive terminals to the pinealocytes indicates a modulatory function of neuropeptide Y for pineal physiology. Some of the immunoreactive fibers might originate from neurons located in the brain and be a part of the central innervation of the pineal gland. In a series of human fetuses, neuropeptide Y-containing nerve fibers was present and could be detected as early as in the pineal of four- to five-month-old fetuses. This early innervation of the human pineal is different from most rodents, where the innervation starts postnatally.

Neuropeptide Y in the Adult and Fetal Human Pineal Gland

PubMed Central

Møller, Morten; Phansuwan-Pujito, Pansiri

2014-01-01

Neuropeptide Y was isolated from the porcine brain in 1982 and shown to be colocalized with noradrenaline in sympathetic nerve terminals. The peptide has been demonstrated to be present in sympathetic nerve fibers innervating the pineal gland in many mammalian species. In this investigation, we show by use of immunohistochemistry that neuropeptide Y is present in nerve fibers of the adult human pineal gland. The fibers are classical neuropeptidergic fibers endowed with large boutons en passage and primarily located in a perifollicular position with some fibers entering the pineal parenchyma inside the follicle. The distance from the immunoreactive terminals to the pinealocytes indicates a modulatory function of neuropeptide Y for pineal physiology. Some of the immunoreactive fibers might originate from neurons located in the brain and be a part of the central innervation of the pineal gland. In a series of human fetuses, neuropeptide Y-containing nerve fibers was present and could be detected as early as in the pineal of four- to five-month-old fetuses. This early innervation of the human pineal is different from most rodents, where the innervation starts postnatally. PMID:24757681

The Scaffolding Protein, Grb2-associated Binder-1, in Skeletal Muscles and Terminal Schwann Cells Regulates Postnatal Neuromuscular Synapse Maturation

PubMed Central

Park, So Young; Jang, So Young; Shin, Yoon Kyoung; Jung, Dong Keun; Yoon, Byeol A; Kim, Jong Kook; Jo, Young Rae; Lee, Hye Jeong

2017-01-01

The vertebrate neuromuscular junction (NMJ) is considered as a “tripartite synapse” consisting of a motor axon terminal, a muscle endplate, and terminal Schwann cells that envelope the motor axon terminal. The neuregulin 1 (NRG1)-ErbB2 signaling pathway plays an important role in the development of the NMJ. We previously showed that Grb2-associated binder 1 (Gab1), a scaffolding mediator of receptor tyrosine kinase signaling, is required for NRG1-induced peripheral nerve myelination. Here, we determined the role of Gab1 in the development of the NMJ using muscle-specific conditional Gab1 knockout mice. The mutant mice showed delayed postnatal maturation of the NMJ. Furthermore, the selective loss of the gab1 gene in terminal Schwann cells produced delayed synaptic elimination with abnormal morphology of the motor endplate, suggesting that Gab1 in both muscles and terminal Schwann cells is required for proper NMJ development. Gab1 in terminal Schwann cells appeared to regulate the number and process elongation of terminal Schwann cells during synaptic elimination. However, Gab2 knockout mice did not show any defects in the development of the NMJ. Considering the role of Gab1 in postnatal peripheral nerve myelination, our findings suggest that Gab1 is a pleiotropic and important component of NRG1 signals during postnatal development of the peripheral neuromuscular system. PMID:28680299

The Scaffolding Protein, Grb2-associated Binder-1, in Skeletal Muscles and Terminal Schwann Cells Regulates Postnatal Neuromuscular Synapse Maturation.

PubMed

Park, So Young; Jang, So Young; Shin, Yoon Kyoung; Jung, Dong Keun; Yoon, Byeol A; Kim, Jong Kook; Jo, Young Rae; Lee, Hye Jeong; Park, Hwan Tae

2017-06-01

The vertebrate neuromuscular junction (NMJ) is considered as a "tripartite synapse" consisting of a motor axon terminal, a muscle endplate, and terminal Schwann cells that envelope the motor axon terminal. The neuregulin 1 (NRG1)-ErbB2 signaling pathway plays an important role in the development of the NMJ. We previously showed that Grb2-associated binder 1 (Gab1), a scaffolding mediator of receptor tyrosine kinase signaling, is required for NRG1-induced peripheral nerve myelination. Here, we determined the role of Gab1 in the development of the NMJ using muscle-specific conditional Gab1 knockout mice. The mutant mice showed delayed postnatal maturation of the NMJ. Furthermore, the selective loss of the gab1 gene in terminal Schwann cells produced delayed synaptic elimination with abnormal morphology of the motor endplate, suggesting that Gab1 in both muscles and terminal Schwann cells is required for proper NMJ development. Gab1 in terminal Schwann cells appeared to regulate the number and process elongation of terminal Schwann cells during synaptic elimination. However, Gab2 knockout mice did not show any defects in the development of the NMJ. Considering the role of Gab1 in postnatal peripheral nerve myelination, our findings suggest that Gab1 is a pleiotropic and important component of NRG1 signals during postnatal development of the peripheral neuromuscular system.

Palisade endings: cholinergic sensory organs or effector organs?

PubMed

Blumer, Roland; Konakci, Kadriye Zeynep; Pomikal, Christine; Wieczorek, Grazyna; Lukas, Julius-Robert; Streicher, Johannes

2009-03-01

This study aims to complement the authors' prior findings on palisade endings in extraocular muscles (EOMs) of monkeys, and to clarify whether palisade endings are cholinergic motor or cholinergic sensory. Macaque monkeys (Macaca fascicularis, n = 10) of both sexes were analyzed using three-dimensional (3D) reconstructions, confocal laser scanning microscopy (CLSM), and conventional/immuno transmission electron microscopy (TEM). For CLSM, we used three combinations of triple fluorescent labeling. EOM wholemounts were labeled with cholinergic markers, including choline acetyltransferase (ChAT), choline transporter (ChT), vesicular acetylcholine transporter (VAChT), and a classical postsynaptic marker for motor terminals, namely alpha-bungarotoxin. Muscle fibers were counterstained with phalloidin. 3D reconstructions were done of triple-labeled palisade endings. For immuno TEM, tissue was labeled with antibody against ChAT. Concordant with prior findings, the authors demonstrated that palisade endings at the muscle fiber tips arose from nerve fibers that are ChAT-positive. In 25% of the cases, axons forming palisade endings established multiple neuromuscular contacts outside the palisade complex. Such additional neuromuscular contacts were motor terminals, as demonstrated by alpha-bungarotoxin binding. All palisade endings established nerve terminals on the tendon. In 40% of the palisade endings, nerve terminals were observed on the muscle fiber as well. Neurotendinous contacts and neuromuscular contacts in palisade endings were ChT/ChAT/VAChT-immunoreactive. Neuromuscular contacts exhibited structural features of motor terminals and were also alpha-bungarotoxin positive. The present study ascertained that palisade endings are cholinergic motor organs. Therefore, it was concluded that palisade endings are not candidates to provide eye-position signals.

Ionotropic and metabotropic receptor mediated airway sensory nerve activation.

PubMed

Lee, Min-Goo; Kollarik, Marian; Chuaychoo, Benjamas; Undem, Bradley J

2004-01-01

There are several receptors capable of inducing activating generator potentials in cough-associated afferent terminals in the airways. The chemical receptors leading to generator potentials can be subclassified into ionotropic and metabotropic types. An ionotropic receptor has an agonist-binding domain, and also serves directly as an ion channel that is opened upon binding of the agonist. Examples of ionotropic receptors found in airway sensory nerve terminals include receptors for serotonin (5-HT3 receptors), ATP (P2X receptors), acetylcholine (nicotinic receptors), receptors for capsaicin and related vanilloids (TRPV1 receptors), and acid receptors (acid sensing ion channels). Afferent nerve terminals can also be depolarized via activation of metabotropic or G-protein coupled receptors (GPCRs). Among the GPCRs that can lead to activation of airway afferent fibers include bradykinin B2 and adenosine A1 receptors. The signaling events leading to GPCR-mediated membrane depolarization are more complex than that seen with ionotropic receptors. The GPCR-mediated effects are thought to occur through classical second messenger systems such as activation of phospholipase C. This may lead to membrane depolarization through interaction with specific ionotropic receptors (such as TRPV1) and/or various types of calcium activated channels.

Identification and Characterization of ML352: A Novel, Noncompetitive Inhibitor of the Presynaptic Choline Transporter

PubMed Central

2015-01-01

The high-affinity choline transporter (CHT) is the rate-limiting determinant of acetylcholine (ACh) synthesis, yet the transporter remains a largely undeveloped target for the detection and manipulation of synaptic cholinergic signaling. To expand CHT pharmacology, we pursued a high-throughput screen for novel CHT-targeted small molecules based on the electrogenic properties of transporter-mediated choline transport. In this effort, we identified five novel, structural classes of CHT-specific inhibitors. Chemical diversification and functional analysis of one of these classes identified ML352 as a high-affinity (Ki = 92 nM) and selective CHT inhibitor. At concentrations that fully antagonized CHT in transfected cells and nerve terminal preparations, ML352 exhibited no inhibition of acetylcholinesterase (AChE) or cholineacetyltransferase (ChAT) and also lacked activity at dopamine, serotonin, and norepinephrine transporters, as well as many receptors and ion channels. ML352 exhibited noncompetitive choline uptake inhibition in intact cells and synaptosomes and reduced the apparent density of hemicholinium-3 (HC-3) binding sites in membrane assays, suggesting allosteric transporter interactions. Pharmacokinetic studies revealed limited in vitro metabolism and significant CNS penetration, with features predicting rapid clearance. ML352 represents a novel, potent, and specific tool for the manipulation of CHT, providing a possible platform for the development of cholinergic imaging and therapeutic agents. PMID:25560927

N- and C-terminal substance P fragments: differential effects on striatal [3H]substance P binding and NK1 receptor internalization.

PubMed

Michael-Titus, A T; Blackburn, D; Connolly, Y; Priestley, J V; Whelpton, R

1999-07-13

N- and C-terminal substance P (SP) fragments increase striatal dopamine outflow at nanomolar concentrations. This contrasts with their low affinity for NK1 receptors. To explore this discrepancy, we investigated the interaction of SP and SP fragments with NK1 sites in fresh striatal slices, the same model used in the functional studies on dopamine outflow. [3H]SP bound specifically to one site (Kd = 6.6 +/- 0.9 nM; Bmax = 12.6 +/- 0.7 fmol/mg protein). [3H]SP binding was displaced by SP (IC50 = 11.8 nM), but not by SP(1-7) or SP(5-11), up to 10 microM. In contrast, 10 nM SP(1-7) or SP(5-11) induced significant internalization of the NK1 receptor, similar to that induced by SP. We suggest that SP fragments have high affinity for an NK1 receptor conformer which is different from that labelled by [3H]SP.

Morphologically mixed chemical-electrical synapses formed by primary afferents in rodent vestibular nuclei as revealed by immunofluorescence detection of connexin36 and vesicular glutamate transporter-1

PubMed Central

Nagy, James I.; Bautista, Wendy; Blakley, Brian; Rash, John E.

2013-01-01

Axon terminals forming mixed chemical/electrical synapses in the lateral vestibular nucleus of rat were described over forty years ago. Because gap junctions formed by connexins are the morphological correlate of electrical synapses, and with demonstrations of widespread expression of the gap junction protein connexin36 (Cx36) in neurons, we investigated the distribution and cellular localization of electrical synapses in the adult and developing rodent vestibular nuclear complex, using immunofluorescence detection of Cx36 as a marker for these synapses. In addition, we examined Cx36 localization in relation to that of the nerve terminal marker vesicular glutamate transporter-1 (vglut-1). An abundance of immunolabelling for Cx36 in the form of Cx36-puncta was found in each of the four major vestibular nuclei of adult rat and mouse. Immunolabelling was associated with somata and initial dendrites of medium and large neurons, and was absent in vestibular nuclei of Cx36 knockout mice. Cx36-puncta were seen either dispersed or aggregated into clusters on the surface of neurons, and were never found to occur intracellularly. Nearly all Cx36-puncta were localized to large nerve terminals immunolabelled for vglut-1. These terminals and their associated Cx36-puncta were substantially depleted after labyrinthectomy. Developmentally, labelling for Cx36 was already present in the vestibular nuclei at postnatal day 5, where it was only partially co-localized with vglut-1, and did not become fully associated with vglut-1-positive terminals until postnatal day 20 to 25. The results show that vglut-1-positive primary afferent nerve terminals form mixed synapses throughout the vestibular nuclear complex, that the gap junction component of these synapses contain Cx36, that multiple Cx36-containing gap junctions are associated with individual vglut-1 terminals and that the development of these mixed synapses is protracted over several postnatal weeks. PMID:23912039

Schwann Cells in Neuromuscular Junction Formation and Maintenance.

PubMed

Barik, Arnab; Li, Lei; Sathyamurthy, Anupama; Xiong, Wen-Cheng; Mei, Lin

2016-09-21

The neuromuscular junction (NMJ) is a tripartite synapse that is formed by motor nerve terminals, postjunctional muscle membranes, and terminal Schwann cells (TSCs) that cover the nerve-muscle contact. NMJ formation requires intimate communications among the three different components. Unlike nerve-muscle interaction, which has been well characterized, less is known about the role of SCs in NMJ formation and maintenance. We show that SCs in mice lead nerve terminals to prepatterned AChRs. Ablating SCs at E8.5 (i.e., prior nerve arrival at the clusters) had little effect on aneural AChR clusters at E13.5, suggesting that SCs may not be necessary for aneural clusters. SC ablation at E12.5, a time when phrenic nerves approach muscle fibers, resulted in smaller and fewer nerve-induced AChR clusters; however, SC ablation at E15.5 reduced AChR cluster size but had no effect on cluster density, suggesting that SCs are involved in AChR cluster maturation. Miniature endplate potential amplitude, but not frequency, was reduced when SCs were ablated at E15.5, suggesting that postsynaptic alterations may occur ahead of presynaptic deficits. Finally, ablation of SCs at P30, after NMJ maturation, led to NMJ fragmentation and neuromuscular transmission deficits. Miniature endplate potential amplitude was reduced 3 d after SC ablation, but both amplitude and frequency were reduced 6 d after. Together, these results indicate that SCs are not only required for NMJ formation, but also necessary for its maintenance; and postsynaptic function and structure appeared to be more sensitive to SC ablation. Neuromuscular junctions (NMJs) are critical for survival and daily functioning. Defects in NMJ formation during development or maintenance in adulthood result in debilitating neuromuscular disorders. The role of Schwann cells (SCs) in NMJ formation and maintenance was not well understood. We genetically ablated SCs during development and after NMJ formation to investigate the consequences of the ablation. This study reveals a critical role of SCs in NMJ formation as well as maintenance. Copyright © 2016 the authors 0270-6474/16/369770-12$15.00/0.

Suprachiasmatic nuclei and Circadian rhythms. The role of suprachiasmatic nuclei on rhythmic activity of neurons in the lateral hypothalamic area, ventromedian nuclei and pineal gland

NASA Technical Reports Server (NTRS)

Nishino, H.

1977-01-01

Unit activity of lateral hypothalamic area (LHA) and Ventromedian nuclei (VMN) was recorded in urethane anesthetized male rats. A 5 to 10 sec. a 3-5 min and a circadian rhythmicity were observed. In about 15% of all neurons, spontaneous activity of LHA and VMN showed reciprocal relationships. Subthreshold stimuli applied at a slow rate in the septum and the suprachiasmatic nuclei (SCN) suppressed the rhythms without changing firing rates. On the other hand, stimulation of the optic nerve at a rate of 5 to 10/sec increased firing rates in 1/3 of neurons of SCN. Iontophoretically applied acetylcholine increased 80% of tested neurons of SCN, whereas norepinephrine, dopamine and 5 HT inhibited 64, 60 and 75% of SCN neurons respectively. These inhibitions were much stronger in neurons, the activity of which was increased by optic nerve stimulation. Stimulation of the SCN inhibited the tonic activity in cervical sympathetic nerves.

Deficient functional recovery after facial nerve crush in rats is associated with restricted rearrangements of synaptic terminals in the facial nucleus.

PubMed

Hundeshagen, G; Szameit, K; Thieme, H; Finkensieper, M; Angelov, D N; Guntinas-Lichius, O; Irintchev, A

2013-09-17

Crush injuries of peripheral nerves typically lead to axonotmesis, axonal damage without disruption of connective tissue sheaths. Generally, human patients and experimental animals recover well after axonotmesis and the favorable outcome has been attributed to precise axonal reinnervation of the original peripheral targets. Here we assessed functionally and morphologically the long-term consequences of facial nerve axonotmesis in rats. Expectedly, we found that 5 months after crush or cryogenic nerve lesion, the numbers of motoneurons with regenerated axons and their projection pattern into the main branches of the facial nerve were similar to those in control animals suggesting precise target reinnervation. Unexpectedly, however, we found that functional recovery, estimated by vibrissal motion analysis, was incomplete at 2 months after injury and did not improve thereafter. The maximum amplitude of whisking remained substantially, by more than 30% lower than control values even 5 months after axonotmesis. Morphological analyses showed that the facial motoneurons ipsilateral to injury were innervated by lower numbers of glutamatergic terminals (-15%) and cholinergic perisomatic boutons (-26%) compared with the contralateral non-injured motoneurons. The structural deficits were correlated with functional performance of individual animals and associated with microgliosis in the facial nucleus but not with polyinnervation of muscle fibers. These results support the idea that restricted CNS plasticity and insufficient afferent inputs to motoneurons may substantially contribute to functional deficits after facial nerve injuries, possibly including pathologic conditions in humans like axonotmesis in idiopathic facial nerve (Bell's) palsy. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Schizophrenia: a review of neuropharmacology.

PubMed

Lyne, J; Kelly, B D; O'Connor, W T

2004-01-01

The last few decades have seen significant advances in our understanding of the neurochemical basis of schizophrenia. To describe the neurotransmitter systems and nerve circuits implicated in schizophrenia; to compare the neuropharmacology of typical and atypical anti-psychotic agents; and to describe recent developments in the pharmacological treatment of schizophrenia. Relevant pharmacological, neurophysiological and psychiatric literature was examined and reviewed. Schizophrenia is associated with abnormalities of multiple neurotransmitter systems, including dopamine, serotonin, gamma-aminobutyric acid and glutamate. Typical and atypical antipsychotic agents differ in their receptor-binding affinities, which are related to their differing side-effect profiles. Novel therapeutic strategies include normalisation of synaptic dopamine or serotonin levels, serotonin receptor antagonism and modulation of cerebral protein synthesis. The ideal treatment for schizophrenia may not be a single pharmacological agent but several agents that match the different expressions of the illness, in combination with psycho-social interventions.

Increased vesicular monoamine transporter binding during early abstinence in human methamphetamine users: Is VMAT2 a stable dopamine neuron biomarker?

PubMed

Boileau, Isabelle; Rusjan, Pablo; Houle, Sylvain; Wilkins, Diana; Tong, Junchao; Selby, Peter; Guttman, Mark; Saint-Cyr, Jean A; Wilson, Alan A; Kish, Stephen J

2008-09-24

Animal data indicate that methamphetamine can damage striatal dopamine terminals. Efforts to document dopamine neuron damage in living brain of methamphetamine users have focused on the binding of [(11)C]dihydrotetrabenazine (DTBZ), a vesicular monoamine transporter (VMAT2) positron emission tomography (PET) radioligand, as a stable dopamine neuron biomarker. Previous PET data report a slight decrease in striatal [(11)C]DTBZ binding in human methamphetamine users after prolonged (mean, 3 years) abstinence, suggesting that the reduction would likely be substantial in early abstinence. We measured striatal VMAT2 binding in 16 recently withdrawn (mean, 19 d; range, 1-90 d) methamphetamine users and in 14 healthy matched-control subjects during a PET scan with (+)[(11)C]DTBZ. Unexpectedly, striatal (+)[(11)C]DTBZ binding was increased in methamphetamine users relative to controls (+22%, caudate; +12%, putamen; +11%, ventral striatum). Increased (+)[(11)C]DTBZ binding in caudate was most marked in methamphetamine users abstinent for 1-3 d (+41%), relative to the 7-21 d (+15%) and >21 d (+9%) groups. Above-normal VMAT2 binding in some drug users suggests that any toxic effect of methamphetamine on dopamine neurons might be masked by an increased (+)[(11)C]DTBZ binding and that VMAT2 radioligand binding might not be, as is generally assumed, a "stable" index of dopamine neuron integrity in vivo. One potential explanation for increased (+)[(11)C]DTBZ binding is that VMAT2 binding is sensitive to changes in vesicular dopamine storage levels, presumably low in drug users. If correct, (+)[(11)C]DTBZ might be a useful imaging probe to correlate changes in brain dopamine stores and behavior in users of methamphetamine.

Role of dopamine transporters in the behavioral effects of 3,4-methylenedioxymethamphetamine (MDMA) in nonhuman primates

PubMed Central

Fantegrossi, William E.; Bauzo, Rayna M.; Manvich, Daniel M.; Morales, Jose C.; Votaw, John R.; Goodman, Mark M.

2011-01-01

Rationale The interoceptive and reinforcing effects of 3,4-methylenedioxymethamphetamine (MDMA) are similar to those of psychostimulants, but the role of dopamine in the behavioral effects of MDMA is not well documented, especially in primates. Objective The aim of this study was to assess the role of dopamine in the behavioral effects of MDMA in two nonhuman primate species. Methods The behavioral effects of MDMA, with and without serotonergic or dopaminergic pretreatments, were studied in squirrel monkeys trained to respond under a fixed-interval schedule of stimulus termination; effects on caudate dopamine levels were studied in a separate group of squirrel monkeys using in vivo microdialysis. Positron emission tomography neuroimaging with the dopamine transporter (DAT) ligand [18F]FECNT was used to determine DAT occupancy by MDMA in rhesus monkeys. Results MDMA (0.5–1.5 mg/kg) did not induce behavioral stimulant effects, but the highest dose of MDMA suppressed responding. Pretreatment with fluoxetine (3.0 mg/kg) or the selective 5HT2A antagonist M100907 (0.03–0.3 mg/kg) attenuated the rate suppressing effects of MDMA. In contrast, pretreatment with the selective dopamine transporter inhibitor RTI-177 (0.1 mg/kg) did not alter the rate suppressing effects of MDMA. Administration of MDMA at a dose that suppressed operant behavior had negligible effects on extracellular dopamine. The percent DAT occupancy of MDMA at a dose that suppressed operant behavior also was marginal and reflected low in vivo potency for DAT binding. Conclusions Collectively, these results indicate that behaviorally relevant doses of MDMA do not induce behavioral stimulant or dopamine transporter-mediated effects in nonhuman primates. PMID:19421742

Role of dopamine transporters in the behavioral effects of 3,4-methylenedioxymethamphetamine (MDMA) in nonhuman primates.

PubMed

Fantegrossi, William E; Bauzo, Rayna M; Manvich, Daniel M; Morales, Jose C; Votaw, John R; Goodman, Mark M; Howell, Leonard L

2009-08-01

The interoceptive and reinforcing effects of 3,4-methylenedioxymethamphetamine (MDMA) are similar to those of psychostimulants, but the role of dopamine in the behavioral effects of MDMA is not well documented, especially in primates. The aim of this study was to assess the role of dopamine in the behavioral effects of MDMA in two nonhuman primate species. The behavioral effects of MDMA, with and without serotonergic or dopaminergic pretreatments, were studied in squirrel monkeys trained to respond under a fixed-interval schedule of stimulus termination; effects on caudate dopamine levels were studied in a separate group of squirrel monkeys using in vivo microdialysis. Positron emission tomography neuroimaging with the dopamine transporter (DAT) ligand [18F]FECNT was used to determine DAT occupancy by MDMA in rhesus monkeys. MDMA (0.5-1.5 mg/kg) did not induce behavioral stimulant effects, but the highest dose of MDMA suppressed responding. Pretreatment with fluoxetine (3.0 mg/kg) or the selective 5HT(2A) antagonist M100907 (0.03-0.3 mg/kg) attenuated the rate suppressing effects of MDMA. In contrast, pretreatment with the selective dopamine transporter inhibitor RTI-177 (0.1 mg/kg) did not alter the rate suppressing effects of MDMA. Administration of MDMA at a dose that suppressed operant behavior had negligible effects on extracellular dopamine. The percent DAT occupancy of MDMA at a dose that suppressed operant behavior also was marginal and reflected low in vivo potency for DAT binding. Collectively, these results indicate that behaviorally relevant doses of MDMA do not induce behavioral stimulant or dopamine transporter-mediated effects in nonhuman primates.

Chronic methamphetamine administration causes differential regulation of transcription factors in the rat midbrain.

PubMed

Krasnova, Irina N; Ladenheim, Bruce; Hodges, Amber B; Volkow, Nora D; Cadet, Jean Lud

2011-04-25

Methamphetamine (METH) is an addictive and neurotoxic psychostimulant widely abused in the USA and throughout the world. When administered in large doses, METH can cause depletion of striatal dopamine terminals, with preservation of midbrain dopaminergic neurons. Because alterations in the expression of transcription factors that regulate the development of dopaminergic neurons might be involved in protecting these neurons after toxic insults, we tested the possibility that their expression might be affected by toxic doses of METH in the adult brain. Male Sprague-Dawley rats pretreated with saline or increasing doses of METH were challenged with toxic doses of the drug and euthanized two weeks later. Animals that received toxic METH challenges showed decreases in dopamine levels and reductions in tyrosine hydroxylase protein concentration in the striatum. METH pretreatment protected against loss of striatal dopamine and tyrosine hydroxylase. In contrast, METH challenges caused decreases in dopamine transporters in both saline- and METH-pretreated animals. Interestingly, METH challenges elicited increases in dopamine transporter mRNA levels in the midbrain in the presence but not in the absence of METH pretreatment. Moreover, toxic METH doses caused decreases in the expression of the dopamine developmental factors, Shh, Lmx1b, and Nurr1, but not in the levels of Otx2 and Pitx3, in saline-pretreated rats. METH pretreatment followed by METH challenges also decreased Nurr1 but increased Otx2 and Pitx3 expression in the midbrain. These findings suggest that, in adult animals, toxic doses of METH can differentially influence the expression of transcription factors involved in the developmental regulation of dopamine neurons. The combined increases in Otx2 and Pitx3 expression after METH preconditioning might represent, in part, some of the mechanisms that served to protect against METH-induced striatal dopamine depletion observed after METH preconditioning.

Disruption of the Axonal Trafficking of Tyrosine Hydroxylase mRNA Impairs Catecholamine Biosynthesis in the Axons of Sympathetic Neurons

PubMed Central

Gioio, Anthony E.

2017-01-01

Abstract Tyrosine hydroxylase (TH) is the enzyme that catalyzes the rate-limiting step in the biosynthesis of the catecholamine neurotransmitters. In a previous communication, evidence was provided that TH mRNA is trafficked to the axon, where it is locally translated. In addition, a 50-bp sequence element in the 3′untranslated region (3’UTR) of TH mRNA was identified that directs TH mRNA to distal axons (i.e., zip-code). In the present study, the hypothesis was tested that local translation of TH plays an important role in the biosynthesis of the catecholamine neurotransmitters in the axon and/or presynaptic nerve terminal. Toward this end, a targeted deletion of the axonal transport sequence element was developed, using the lentiviral delivery of the CRISPR/Cas9 system, and two guide RNA (gRNA) sequences flanking the 50-bp cis-acting regulatory element in rat superior cervical ganglion (SCG) neurons. Deletion of the axonal transport element reduced TH mRNA levels in the distal axons and reduced the axonal protein levels of TH and TH activity as measured by phosphorylation of SER40 in SCG neurons. Moreover, deletion of the zip-code diminished the axonal levels of dopamine (DA) and norepinephrine (NE). Conversely, the local translation of exogenous TH mRNA in the distal axon enhanced TH levels and activity, and elevated axonal NE levels. Taken together, these results provide direct evidence to support the hypothesis that TH mRNA trafficking and local synthesis of TH play an important role in the synthesis of catecholamines in the axon and presynaptic terminal. PMID:28630892

Disruption of the Axonal Trafficking of Tyrosine Hydroxylase mRNA Impairs Catecholamine Biosynthesis in the Axons of Sympathetic Neurons.

PubMed

Aschrafi, Armaz; Gioio, Anthony E; Dong, Lijin; Kaplan, Barry B

2017-01-01

Tyrosine hydroxylase (TH) is the enzyme that catalyzes the rate-limiting step in the biosynthesis of the catecholamine neurotransmitters. In a previous communication, evidence was provided that TH mRNA is trafficked to the axon, where it is locally translated. In addition, a 50-bp sequence element in the 3'untranslated region (3'UTR) of TH mRNA was identified that directs TH mRNA to distal axons (i.e., zip-code). In the present study, the hypothesis was tested that local translation of TH plays an important role in the biosynthesis of the catecholamine neurotransmitters in the axon and/or presynaptic nerve terminal. Toward this end, a targeted deletion of the axonal transport sequence element was developed, using the lentiviral delivery of the CRISPR/Cas9 system, and two guide RNA (gRNA) sequences flanking the 50-bp cis- acting regulatory element in rat superior cervical ganglion (SCG) neurons. Deletion of the axonal transport element reduced TH mRNA levels in the distal axons and reduced the axonal protein levels of TH and TH activity as measured by phosphorylation of SER40 in SCG neurons. Moreover, deletion of the zip-code diminished the axonal levels of dopamine (DA) and norepinephrine (NE). Conversely, the local translation of exogenous TH mRNA in the distal axon enhanced TH levels and activity, and elevated axonal NE levels. Taken together, these results provide direct evidence to support the hypothesis that TH mRNA trafficking and local synthesis of TH play an important role in the synthesis of catecholamines in the axon and presynaptic terminal.

Atropine and Other Anticholinergic Drugs

DTIC Science & Technology

2007-01-01

parasympathetic est concern, along with their chemical names and nerves and muscarinic and nicotinic choliner - two-letter military designations, are tabun (o...that hydrolyzes the cholin - tions, tremor, convulsions, electrical seizures and ergic neurotransmitter acetylcholine (ACh), that loss of respiratory... cholin - depress salivation, bronchial secretions and ergic synaptic nerve terminals, this leads to very sweating, increase heart rate, produce pupilary

Anatomy and Neurophysiology of Cough

PubMed Central

Canning, Brendan J.; Chang, Anne B.; Bolser, Donald C.; Smith, Jaclyn A.; Mazzone, Stuart B.; Adams, Todd M.; Altman, Kenneth W.; Barker, Alan F.; Birring, Surinder S.; Blackhall, Fiona; Bolser, Donald, C.; Boulet, Louis-Philippe; Braman, Sidney S.; Brightling, Christopher; Callahan-Lyon, Priscilla; Canning, Brendan; Chang, Anne Bernadette; Coeytaux, Remy; Cowley, Terrie; Davenport, Paul; Diekemper, Rebecca L.; Ebihara, Satoru; El Solh, Ali A.; Escalante, Patricio; Feinstein, Anthony; Field, Stephen K.; Fisher, Dina; French, Cynthia T.; Gibson, Peter; Gold, Philip; Grant, Cameron; Harding, Susan M.; Harnden, Anthony; Hill, Adam T.; Irwin, Richard S.; Kahrilas, Peter J.; Keogh, Karina A.; Lane, Andrew P.; Lewis, Sandra Zelman; Lim, Kaiser; Malesker, Mark A.; Mazzone, Peter; Mazzone, Stuart; Molasiotis, Alex; Murad, M. Hassan; Newcombe, Peter; Nguyen, Huong Q.; Oppenheimer, John; Prezant, David; Pringsheim, Tamara; Restrepo, Marcos I.; Rosen, Mark; Rubin, Bruce; Ryu, Jay H.; Smith, Jaclyn; Tarlo, Susan M.; Turner, Ronald B.; Vertigan, Anne; Wang, Gang; Weir, Kelly

2014-01-01

Bronchopulmonary C-fibers and a subset of mechanically sensitive, acid-sensitive myelinated sensory nerves play essential roles in regulating cough. These vagal sensory nerves terminate primarily in the larynx, trachea, carina, and large intrapulmonary bronchi. Other bronchopulmonary sensory nerves, sensory nerves innervating other viscera, as well as somatosensory nerves innervating the chest wall, diaphragm, and abdominal musculature regulate cough patterning and cough sensitivity. The responsiveness and morphology of the airway vagal sensory nerve subtypes and the extrapulmonary sensory nerves that regulate coughing are described. The brainstem and higher brain control systems that process this sensory information are complex, but our current understanding of them is considerable and increasing. The relevance of these neural systems to clinical phenomena, such as urge to cough and psychologic methods for treatment of dystussia, is high, and modern imaging methods have revealed potential neural substrates for some features of cough in the human. PMID:25188530

Nerve Entrapment Syndromes at the Wrist and Elbow by Sonography.

PubMed

Klauser, Andrea S; Buzzegoli, Tommaso; Taljanovic, Mihra S; Strobl, Sylvia; Rauch, Stefan; Teh, James; Wanschitz, Julia; Löscher, Wolfgang; Martinoli, Carlo

2018-07-01

Nerve entrapment syndromes of the upper extremity are associated with structural abnormalities or by an intrinsic abnormality of the nerve. Nerve entrapment syndromes generally have a typical clinical presentation, and findings on physical examination and in conjunction with electrodiagnostic studies imaging is used to evaluate the cause, severity, and etiology of the entrapment. With the development of high-frequency linear array transducers (12-24 MHz), ultrasound (US) is incomparable in terms of spatial resolution to depict morphological aspects and changes in nerves. US can identify the abnormalities causing entrapment, such as fibrous bands, ganglia, anomalous muscles, and osseous deformities, with the advantage of dynamic assessment under active and passive examination. US is a unique diagnostic modality that allows superb visualization of both large and small peripheral terminal nerve branches of the upper extremity and enables the correct diagnosis of various nerve entrapment syndromes. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Exercise-induced rescue of tongue function without striatal dopamine sparing in a rat neurotoxin model of Parkinson disease.

PubMed

Ciucci, Michelle R; Schaser, Allison J; Russell, John A

2013-09-01

Unilateral lesions to the medial forebrain bundle with 6-hydroxydopamine (6-OHDA) lead to force and timing deficits during a complex licking task. We hypothesized that training targeting tongue force generation during licking would improve timing and force measures and also lead to striatal dopamine sparing. Nine month-old male Fisher344/Brown Norway rats were used in this experiment. Sixteen rats were in the control condition and received tongue exercise (n=8) or no exercise (n=8). Fourteen rats were in the 6-OHDA lesion condition and underwent tongue exercise (n=7) and or no exercise (n=7). Following 4 weeks of training and post-training measures, all animals underwent bilateral stimulation of the hypoglossal nerves to measure muscle contractile properties and were then transcardially perfused and brain tissues collected for immunohistochemistry to examine striatal dopamine content. Results demonstrated that exercise animals performed better for maximal force, average force, and press rate than their no-exercise counterparts, and the 6-OHDA animals that underwent exercise performed as well as the Control No Exercise group. Interestingly, there were no group differences for tetanic muscle force, despite behavioral recovery of forces. Additionally, behavioral and neurochemical analyses indicate that there were no differences in striatal dopamine. Thus, targeted exercise can improve tongue force and timing deficits related to 6-OHDA lesions and this exercise likely has a central, versus peripheral (muscle strength) mechanism. However, this mechanism is not related to sparing of striatal dopamine content. Copyright © 2013 Elsevier B.V. All rights reserved.

Light microscopic image analysis system to quantify immunoreactive terminal area apposed to nerve cells.

PubMed

Wu, L C; D'Amelio, F; Fox, R A; Polyakov, I; Daunton, N G

1997-06-06

The present report describes a desktop computer-based method for the quantitative assessment of the area occupied by immunoreactive terminals in close apposition to nerve cells in relation to the perimeter of the cell soma. This method is based on Fast Fourier Transform (FFT) routines incorporated in NIH-Image public domain software. Pyramidal cells of layer V of the somatosensory cortex outlined by GABA immunolabeled terminals were chosen for our analysis. A Leitz Diaplan light microscope was employed for the visualization of the sections. A Sierra Scientific Model 4030 CCD camera was used to capture the images into a Macintosh Centris 650 computer. After preprocessing, filtering was performed on the power spectrum in the frequency domain produced by the FFT operation. An inverse FFT with filter procedure was employed to restore the images to the spatial domain. Pasting of the original image to the transformed one using a Boolean logic operation called 'AND'ing produced an image with the terminals enhanced. This procedure allowed the creation of a binary image using a well-defined threshold of 128. Thus, the terminal area appears in black against a white background. This methodology provides an objective means of measurement of area by counting the total number of pixels occupied by immunoreactive terminals in light microscopic sections in which the difficulties of labeling intensity, size, shape and numerical density of terminals are avoided.

Light microscopic image analysis system to quantify immunoreactive terminal area apposed to nerve cells

NASA Technical Reports Server (NTRS)

Wu, L. C.; D'Amelio, F.; Fox, R. A.; Polyakov, I.; Daunton, N. G.

1997-01-01

The present report describes a desktop computer-based method for the quantitative assessment of the area occupied by immunoreactive terminals in close apposition to nerve cells in relation to the perimeter of the cell soma. This method is based on Fast Fourier Transform (FFT) routines incorporated in NIH-Image public domain software. Pyramidal cells of layer V of the somatosensory cortex outlined by GABA immunolabeled terminals were chosen for our analysis. A Leitz Diaplan light microscope was employed for the visualization of the sections. A Sierra Scientific Model 4030 CCD camera was used to capture the images into a Macintosh Centris 650 computer. After preprocessing, filtering was performed on the power spectrum in the frequency domain produced by the FFT operation. An inverse FFT with filter procedure was employed to restore the images to the spatial domain. Pasting of the original image to the transformed one using a Boolean logic operation called 'AND'ing produced an image with the terminals enhanced. This procedure allowed the creation of a binary image using a well-defined threshold of 128. Thus, the terminal area appears in black against a white background. This methodology provides an objective means of measurement of area by counting the total number of pixels occupied by immunoreactive terminals in light microscopic sections in which the difficulties of labeling intensity, size, shape and numerical density of terminals are avoided.

Structural evidence that botulinum toxin blocks neuromuscular transmission by impairing the calcium influx that normally accompanies nerve depolarization

PubMed Central

1981-01-01

Taking advantage of the fact that nerve terminal mitochondria swell and sequester calcium during repetitive nerve stimulation, we here confirm that this change is caused by calcium influx into the nerve and use this fact to show that botulinum toxin abolishes such calcium influx. The optimal paradigm for producing the mitochondrial changes in normal nerves worked out to be 5 min of stimulation at 25 Hz in frog Ringer's solution containing five time more calcium than normal. Applying this same stimulation paradigm to botulinum-intoxicated nerves produced no mitochondrial changes at all. Only when intoxicated nerves were stimulated in 4-aminopyridine (which grossly exaggerates calcium currents in normal nerves) or when they were soaked in black widow spider venom (which is a nerve-specific calcium ionophore) could nerve mitochondria be induced to swell and accumulate calcium. These results indicate that nerve mitochondria are not damaged directly by the toxin and point instead to a primary inhibition of the normal depolarization- evoked calcium currents that accompany nerve activity. Because these currents normally provide the calcium that triggers transmitter secretion from the nerve, this demonstration of their inhibition helps to explain how botulinum toxin paralyzes. PMID:6259176

Effects of chronic methamphetamine on psychomotor and cognitive functions and dopamine signaling in the brain.

PubMed

Thanos, Panayotis K; Kim, Ronald; Delis, Foteini; Rocco, Mark J; Cho, Jacob; Volkow, Nora D

2017-03-01

Methamphetamine (MA) studies in animals usually involve acute, binge, or short-term exposure to the drug. However, addicts take substantial amounts of MA for extended periods of time. Here we wished to study the effects of MA exposure on brain and behavior, using an animal model analogous to this pattern of MA intake. MA doses, 4 and 8mg/kg/day, were based on previously reported average daily freely available MA self-administration levels. We examined the effects of 16 week MA treatment on psychomotor and cognitive function in the rat using open field and novel object recognition tests and we studied the adaptations of the dopaminergic system, using in vitro and in vivo receptor imaging. We show that chronic MA treatment, at doses that correspond to the average daily freely available self-administration levels in the rat, disorganizes open field activity, impairs alert exploratory behavior and anxiety-like state, and downregulates dopamine transporter in the striatum. Under these treatment conditions, dopamine terminal functional integrity in the nucleus accumbens is also affected. In addition, lower dopamine D1 receptor binding density, and, to a smaller degree, lower dopamine D2 receptor binding density were observed. Potential mechanisms related to these alterations are discussed. Copyright © 2016. Published by Elsevier B.V.

The N-Terminal Residues 43 to 60 Form the Interface for Dopamine Mediated α-Synuclein Dimerisation

PubMed Central

Leong, Su Ling; Hinds, Mark G.; Connor, Andrea R.; Smith, David P.; Illes-Toth, Eva; Pham, Chi L. L.; Barnham, Kevin J.; Cappai, Roberto

2015-01-01

α-synuclein (α-syn) is a major component of the intracellular inclusions called Lewy bodies, which are a key pathological feature in the brains of Parkinson’s disease patients. The neurotransmitter dopamine (DA) inhibits the fibrillisation of α-syn into amyloid, and promotes α-syn aggregation into SDS-stable soluble oligomers. While this inhibition of amyloid formation requires the oxidation of both DA and the methionines in α-syn, the molecular basis for these processes is still unclear. This study sought to define the protein sequences required for the generation of oligomers. We tested N- (α-syn residues 43–140) and C-terminally (1–95) truncated α-syn, and found that similar to full-length protein both truncated species formed soluble DA:α-syn oligomers, albeit 1–95 had a different profile. Using nuclear magnetic resonance (NMR), and the N-terminally truncated α-syn 43–140 protein, we analysed the structural characteristics of the DA:α-syn 43–140 dimer and α-syn 43–140 monomer and found the dimerisation interface encompassed residues 43 to 60. Narrowing the interface to this small region will help define the mechanism by which DA mediates the formation of SDS-stable soluble DA:α-syn oligomers. PMID:25679387

Neurite outgrowth mediated by the heat shock protein Hsp90α: a novel target for the antipsychotic drug aripiprazole

PubMed Central

Ishima, T; Iyo, M; Hashimoto, K

2012-01-01

Aripiprazole is an atypical antipsychotic drug approved for the treatment of psychiatric disorders such as schizophrenia, bipolar disorder, major depressive disorder and autism. The drug shows partial agonistic activity at dopamine D2 receptors and 5-hydroxytryptamine (5-HT) 5-HT1A receptors, and antagonistic activity at 5-HT2A receptors. However, the precise mechanistic pathways remain unclear. In this study, we examined the effects of aripiprazole on neurite outgrowth. Aripiprazole significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells, in a concentration-dependent manner. The 5-HT1A receptor antagonist WAY-100635, but not the dopamine D2 receptor antagonist sulpiride, blocked the effects of aripiprazole, although, only partially. Specific inhibitors of inositol 1,4,5-triphosphate (IP3) receptors and BAPTA-AM, a chelator of intracellular Ca2+, blocked the effects of aripiprazole. Moreover, specific inhibitors of several common signaling pathways phospholipase C-γ (PLC-γ), phosphatidylinositol-3 kinase (PI3K), mammalian target of rapamycin, p38 MAPK, c-Jun N-terminal kinase, Akt, Ras, Raf, ERK, MAPK) also blocked the effects of aripiprazole. Using proteomic analysis, we found that aripiprazole significantly increased levels of the heat shock protein Hsp90α in cultured cells. The effects of aripiprazole on NGF-induced neurite outgrowth were significantly attenuated by treatment with Hsp90α RNA interference, but not by the negative control of Hsp90α. These findings suggest that both 5-HT1A receptor activation and Ca2+ signaling via IP3 receptors, as well as their downstream cellular signaling pathways play a role in the promotion of aripiprazole-induced neurite outgrowth. Furthermore, aripiprazole-induced increases in Hsp90α protein expression may form part of the therapeutic mechanism for this drug. PMID:23047241

Handlebar palsy--a compression syndrome of the deep terminal (motor) branch of the ulnar nerve in biking.

PubMed

Capitani, Daniel; Beer, Serafin

2002-10-01

We describe 3 patients who developed a severe palsy of the intrinsic ulnar supplied hand muscles after bicycle riding. Clinically and electrophysiologically all showed an isolated lesion of the deep terminal motor branch of the ulnar nerve leaving the hypothenar muscle and the distal sensory branch intact. This type of lesion at the canal of Guyon is quite unusual, caused in the majority of cases by chronic external pressure over the ulnar palm. In earlier reports describing this lesion in bicycle riders, most patients experienced this lesion after a long distance ride. Due to the change of riding position and shape of handlebars (horn handle) in recent years, however, even a single bicycle ride may be sufficient to cause a lesion of this ulnar branch. Especially in downhill riding, a large part of the body weight is supported by the hand on the corner of the handlebar leading to a high load at Guyon's canal. As no sensory fibres are affected, the patients are not aware of the ongoing nerve compression until a severe lesion develops. Individual adaptation of the handlebar and riding position seems to be crucial for prevention of this type of nerve lesion.

Effect of endogenous tachykinins on neuro-effector transmission of vagal nerve in guinea-pig tracheal tissue.

PubMed

Aizawa, H; Miyazaki, N; Inoue, H; Ikeda, T; Shigematsu, N

1990-01-01

To elucidate the effect of endogenous tachykinins on neuro-effector transmission of vagal nerves, we performed in vitro experiments using guinea-pig tracheal smooth muscle. The subthreshold dose (the highest dose which did not induce any smooth muscle contraction) of capsaicin (10(-8) to 10(-7) M) increased the amplitudes of contractions evoked by electrical field stimulation (EFS) significantly, but not those by acetylcholine (ACh). The inhibitor of neutral endopeptidase, phosphoramidon (10(-7) to 10(-6) M), increased the contractions evoked by EFS significantly. The inhibitor of cholinesterase, physostigmine (10(-6) to 10(-5) M), induced smooth muscle contractions, but such contractions were inhibited by atropine, suggesting the spontaneous release of ACh from the vagal nerve terminals. The subthreshold dose of substance P or capsaicin increased the contractions evoked by physostigmine. These results indicated that endogenous tachykinins increase the spontaneous ACh release as well as the ACh release in response to vagal stimulation from the nerve terminals. Furthermore, it is suggested that the excitatory effects of the tachykinins on the vagal neuro-effector transmission may be modulated by neutral endopeptidase in the guinea pig.

A comparison of epithalamic, hypothalamic and spinal neurosecretory terminals.

PubMed

Vigh-Teichmann, I; Vigh, B

1979-01-01

Nerve endings of epithalamic, hypothalamic and spinal neurosecretory areas were studied by light and electron microscopy in various vertebrates (from fishes up to mammals) including the lancelet. Areas investigated were the pineal organ, the pulvinar corporis pinealis, the neurohypophysis, the median eminence, the urophysis, the terminal filum and the medullo-spinal neurosecretory zones. We found that in all these areas the neurosecretory endings have common structures, which we call synaptic hemidesmosomes or neurohormonal terminals. These are characterized by accumulation of vesicles, and dense projections in a terminal on the basal lamina of the surface of the nervous tissue. A critical review of the literature suggests that a considerble neuroendocrine activity is associated with synaptic hemidesmosomes as special neurohormonal effector structures of the nerve cells. The cell-to-cell synapses formed by neurosecretory cells are discussed in connection with the dual capacity of these cells to function as both endocrine and "ordinary# neuronal elements. The importance of the external cerebrospinal fluid (CSF) space for the transport of materials released in the so-called neurohemal areas, is stressed.

Selective Deletion of Sodium Salt Taste during Development Leads to Expanded Terminal Fields of Gustatory Nerves in the Adult Mouse Nucleus of the Solitary Tract.

PubMed

Sun, Chengsan; Hummler, Edith; Hill, David L

2017-01-18

Neuronal activity plays a key role in the development of sensory circuits in the mammalian brain. In the gustatory system, experimental manipulations now exist, through genetic manipulations of specific taste transduction processes, to examine how specific taste qualities (i.e., basic tastes) impact the functional and structural development of gustatory circuits. Here, we used a mouse knock-out model in which the transduction component used to discriminate sodium salts from other taste stimuli was deleted in taste bud cells throughout development. We used this model to test the hypothesis that the lack of activity elicited by sodium salt taste impacts the terminal field organization of nerves that carry taste information from taste buds to the nucleus of the solitary tract (NST) in the medulla. The glossopharyngeal, chorda tympani, and greater superficial petrosal nerves were labeled to examine their terminal fields in adult control mice and in adult mice in which the α-subunit of the epithelial sodium channel was conditionally deleted in taste buds (αENaC knockout). The terminal fields of all three nerves in the NST were up to 2.7 times greater in αENaC knock-out mice compared with the respective field volumes in control mice. The shapes of the fields were similar between the two groups; however, the density and spread of labels were greater in αENaC knock-out mice. Overall, our results show that disruption of the afferent taste signal to sodium salts disrupts the normal age-dependent "pruning" of all terminal fields, which could lead to alterations in sensory coding and taste-related behaviors. Neural activity plays a major role in the development of sensory circuits in the mammalian brain. To date, there has been no direct test of whether taste-elicited neural activity has a role in shaping central gustatory circuits. However, recently developed genetic tools now allow an assessment of how specific taste stimuli, in this case sodium salt taste, play a role in the maturation of the terminal fields in the mouse brainstem. We found that the specific deletion of sodium salt taste during development produced terminal fields in adults that were dramatically larger than in control mice, demonstrating for the first time that sodium salt taste-elicited activity is necessary for the normal maturation of gustatory inputs into the brain. Copyright © 2017 the authors 0270-6474/17/370660-13$15.00/0.

Selective Deletion of Sodium Salt Taste during Development Leads to Expanded Terminal Fields of Gustatory Nerves in the Adult Mouse Nucleus of the Solitary Tract

PubMed Central

Sun, Chengsan; Hummler, Edith

2017-01-01

Neuronal activity plays a key role in the development of sensory circuits in the mammalian brain. In the gustatory system, experimental manipulations now exist, through genetic manipulations of specific taste transduction processes, to examine how specific taste qualities (i.e., basic tastes) impact the functional and structural development of gustatory circuits. Here, we used a mouse knock-out model in which the transduction component used to discriminate sodium salts from other taste stimuli was deleted in taste bud cells throughout development. We used this model to test the hypothesis that the lack of activity elicited by sodium salt taste impacts the terminal field organization of nerves that carry taste information from taste buds to the nucleus of the solitary tract (NST) in the medulla. The glossopharyngeal, chorda tympani, and greater superficial petrosal nerves were labeled to examine their terminal fields in adult control mice and in adult mice in which the α-subunit of the epithelial sodium channel was conditionally deleted in taste buds (αENaC knockout). The terminal fields of all three nerves in the NST were up to 2.7 times greater in αENaC knock-out mice compared with the respective field volumes in control mice. The shapes of the fields were similar between the two groups; however, the density and spread of labels were greater in αENaC knock-out mice. Overall, our results show that disruption of the afferent taste signal to sodium salts disrupts the normal age-dependent “pruning” of all terminal fields, which could lead to alterations in sensory coding and taste-related behaviors. SIGNIFICANCE STATEMENT Neural activity plays a major role in the development of sensory circuits in the mammalian brain. To date, there has been no direct test of whether taste-elicited neural activity has a role in shaping central gustatory circuits. However, recently developed genetic tools now allow an assessment of how specific taste stimuli, in this case sodium salt taste, play a role in the maturation of the terminal fields in the mouse brainstem. We found that the specific deletion of sodium salt taste during development produced terminal fields in adults that were dramatically larger than in control mice, demonstrating for the first time that sodium salt taste-elicited activity is necessary for the normal maturation of gustatory inputs into the brain. PMID:28100747

Co-administration of betulinic acid and methamphetamine causes toxicity to dopaminergic and serotonergic nerve terminals in the striatum of late adolescent rats

PubMed Central

Killinger, Bryan; Shah, Mrudang; Moszczynska, Anna

2013-01-01

Psychostimulant methamphetamine (METH) is toxic to dopaminergic and serotonergic striatal nerve terminals in adult, but not in adolescent, brain. Betulinic acid (BA) and its derivatives are promising anti-HIV agents with some toxic properties. Many METH users, particularly young men, are HIV-positive; therefore, they might be treated with BA or its derivative for HIV infection. It is not known whether BA, or any of its derivatives, is neurotoxic in combination with METH in adolescent brain. The present study investigated the effects of BA and binge METH in the striatum in late adolescent rats. BA or METH alone did not decrease the levels of dopaminergic or serotonergic markers in the striatum whereas BA and METH together decreased these markers in a BA dose-dependent manner. BA and METH combination also caused decreases in the levels of mitochondrial complex I in the same manner; BA alone only slightly decreased the levels of the enzyme in striatal synaptosomes. BA or METH alone increased cytochrome c. METH alone decreased parkin, increased complex II and striatal BA levels. These results suggest that METH in combination with BA can be neurotoxic to dopaminergic and serotonergic striatal nerve terminals in late adolescent brain via mitochondrial dysfunction and parkin deficit. PMID:24151877

Effect of peripheral nerve injury on receptive fields of cells in the cat spinal cord.

PubMed

Devor, M; Wall, P D

1981-06-20

When the sciatic and saphenous nerves are cut and ligated in adult cats, the immediate effect is the production of a completely anesthetic foot and a region in medial lumbar dorsal horn where almost all cells have lost their natural receptive fields (RFs). Beginning at about 1 week and maturing by 4 weeks, some 40% of cells in the medial dorsal horn gain a novel RF on proximal skin, that is, upper and lower leg, thigh, lower back, or perineum. This new RF is supplied by intact proximal nerves and not by sciatic and saphenous nerve fibers that sprouted in the periphery. During the period of switching of RFs from distal to proximal skin there was no gross atrophy of dorsal horn grey matter and no Fink-Heimer stainable degeneration of central arbors and terminals of peripherally axotomized afferents. In intact animals medial dorsal horn cells showed no sign of response to mechanical stimulation of proximal skin. RFs of some of the cells had spontaneous variations in size and sensitivity, but these were not nearly sufficient to explain the large shifts observed after chronic nerve section. Tetanic electrical stimulation of skin or peripheral nerves often caused RFs to shrink, but never to expand. Although natural stimuli of proximal skin would not excite medial dorsal horn cells in intact or acutely deafferented animals, it was found that electrical stimulation of proximal nerves did excite many of these cells, often at short latencies. In the discussion we justify our working hypothesis that the appearance of novel RFs is due to the strengthening or unmasking of normally present but ineffective afferent terminals, rather than to long-distance sprouting of new afferent arbors within the spinal cord.

Intralaryngeal neuroanatomy of the recurrent laryngeal nerve of the rabbit

PubMed Central

Ryan, Stephen; McNicholas, Walter T; O'Regan, Ronan G; Nolan, Philip

2003-01-01

We undertook this study to determine the detailed neuroanatomy of the terminal branches of the recurrent laryngeal nerve (RLN) in the rabbit to facilitate future neurophysiological recordings from identified branches of this nerve. The whole larynx was isolated post mortem in 17 adult New Zealand White rabbits and prepared using a modified Sihler's technique, which stains axons and renders other tissues transparent so that nerve branches can be seen in whole mount preparations. Of the 34 hemi-laryngeal preparations processed, 28 stained well and these were dissected and used to characterize the neuroanatomy of the RLN. In most cases (23/28) the posterior cricoarytenoid muscle (PCA) was supplied by a single branch arising from the RLN, though in five PCA specimens there were two or three separate branches to the PCA. The interarytenoid muscle (IA) was supplied by two parallel filaments arising from the main trunk of the RLN rostral to the branch(es) to the PCA. The lateral cricoarytenoid muscle (LCA) commonly received innervation from two fine twigs branching from the RLN main trunk and travelling laterally towards the LCA. The remaining fibres of the RLN innervated the thyroarytenoid muscle (TA) and comprised two distinct branches, one supplying the pars vocalis and the other branching extensively to supply the remainder of the TA. No communicating anastomosis between the RLN and superior laryngeal nerve within the larynx was found. Our results suggest it is feasible to make electrophysiological recordings from identified terminal branches of the RLN supplying laryngeal adductor muscles separate from the branch or branches to the PCA. However, the very small size of the motor nerves to the IA and LCA suggests that it would be very difficult to record selectively from the nerve supply to individual laryngeal adductor muscles. PMID:12739619

The Effects of Renal Denervation on Renal Hemodynamics and Renal Vasculature in a Porcine Model

PubMed Central

Verloop, Willemien L.; Hubens, Lisette E. G.; Spiering, Wilko; Doevendans, Pieter A.; Goldschmeding, Roel; Bleys, Ronald L. A. W.; Voskuil, Michiel

2015-01-01

Rationale Recently, the efficacy of renal denervation (RDN) has been debated. It is discussed whether RDN is able to adequately target the renal nerves. Objective We aimed to investigate how effective RDN was by means of functional hemodynamic measurements and nerve damage on histology. Methods and Results We performed hemodynamic measurements in both renal arteries of healthy pigs using a Doppler flow and pressure wire. Subsequently unilateral denervation was performed, followed by repeated bilateral hemodynamic measurements. Pigs were terminated directly after RDN or were followed for 3 weeks or 3 months after the procedure. After termination, both treated and control arteries were prepared for histology to evaluate vascular damage and nerve damage. Directly after RDN, resting renal blood flow tended to increase by 29±67% (P = 0.01). In contrast, renal resistance reserve increased from 1.74 (1.28) to 1.88 (1.17) (P = 0.02) during follow-up. Vascular histopathology showed that most nerves around the treated arteries were located outside the lesion areas (8±7 out of 55±25 (14%) nerves per pig were observed within a lesion area). Subsequently, a correlation was noted between a more impaired adventitia and a reduction in renal resistance reserve (β: -0.33; P = 0.05) at three weeks of follow-up. Conclusion Only a small minority of renal nerves was targeted after RDN. Furthermore, more severe adventitial damage was related to a reduction in renal resistance in the treated arteries at follow-up. These hemodynamic and histological observations may indicate that RDN did not sufficiently target the renal nerves. Potentially, this may explain the significant spread in the response after RDN. PMID:26587981

Altered vesicular glutamate transporter distributions in the mouse cochlear nucleus following cochlear insult

PubMed Central

Heeringa, Amarins N.; Stefanescu, Roxana A.; Raphael, Yehoash; Shore, Susan E.

2015-01-01

Vesicular glutamate transporters 1 and 2 (VGLUT1 and VGLUT2) have distinct distributions in the cochlear nucleus that correspond to the sources of the labeled terminals. VGLUT1 is mainly associated with terminals of auditory nerve fibers, whereas VGLUT2 is mainly associated with glutamatergic terminals deriving from other sources that project to the cochlear nucleus (CN), including somatosensory and vestibular terminals. Previous studies in guinea pig have shown that cochlear damage results in a decrease of VGLUT1-labeled puncta and an increase in VGLUT2-labeled puncta. This indicates cross-modal compensation that is of potential importance in somatic tinnitus. To examine whether this effect is consistent across species and to provide a background for future studies, using transgenesis, the current study examines VGLUT expression profiles upon cochlear insult by intracochlear kanamycin injections in the mouse. Intracochlear kanamycin injections abolished ipsilateral ABR responses in all animals and reduced ipsilateral spiral ganglion neuron densities in animals that were sacrificed after four weeks, but not in animals that were sacrificed after three weeks. In all unilaterally deafened animals, VGLUT1 density was decreased in CN regions that receive auditory nerve fiber terminals, i.e. in the deep layer of the dorsal cochlear nucleus (DCN), in the interstitial region where the auditory nerve enters the CN, and in the magnocellular region of the antero- and posteroventral CN. In contrast, density of VGLUT2 expression was upregulated in the fusiform cell layer of the DCN and in the granule cell lamina, which are known to receive somatosensory and vestibular terminals. These results show that a cochlear insult induces cross-modal compensation in the cochlear nucleus of the mouse, confirming previous findings in guinea pig, and that these changes are not dependent on the occurrence of spiral ganglion neuron degeneration. PMID:26705736

Altered vesicular glutamate transporter distributions in the mouse cochlear nucleus following cochlear insult.

PubMed

Heeringa, A N; Stefanescu, R A; Raphael, Y; Shore, S E

2016-02-19

Vesicular glutamate transporters 1 and 2 (VGLUT1 and VGLUT2) have distinct distributions in the cochlear nucleus that correspond to sources of the labeled terminals. VGLUT1 is mainly associated with terminals of auditory nerve fibers, whereas VGLUT2 is mainly associated with glutamatergic terminals deriving from other sources that project to the cochlear nucleus (CN), including somatosensory and vestibular terminals. Previous studies in guinea pig have shown that cochlear damage results in a decrease of VGLUT1-labeled puncta and an increase in VGLUT2-labeled puncta. This indicates cross-modal compensation that is of potential importance in somatic tinnitus. To examine whether this effect is consistent across species and to provide a background for future studies, using transgenesis, the current study examines VGLUT expression profiles upon cochlear insult by intracochlear kanamycin injections in the mouse. Intracochlear kanamycin injections abolished ipsilateral ABR responses in all animals and reduced ipsilateral spiral ganglion neuron densities in animals that were sacrificed after four weeks, but not in animals that were sacrificed after three weeks. In all unilaterally deafened animals, VGLUT1 density was decreased in CN regions that receive auditory nerve fiber terminals, i.e., in the deep layer of the dorsal cochlear nucleus (DCN), in the interstitial region where the auditory nerve enters the CN, and in the magnocellular region of the antero- and posteroventral CN. In contrast, density of VGLUT2 expression was upregulated in the fusiform cell layer of the DCN and in the granule cell lamina, which are known to receive somatosensory and vestibular terminals. These results show that a cochlear insult induces cross-modal compensation in the cochlear nucleus of the mouse, confirming previous findings in guinea pig, and that these changes are not dependent on the occurrence of spiral ganglion neuron degeneration. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

HTDP-2, a new synthetic compound, inhibits glutamate release through reduction of voltage-dependent Ca²⁺ influx in rat cerebral cortex nerve terminals.

PubMed

Lin, Tzu-Yu; Lu, Cheng-Wei; Huang, Shu-Kuei; Chou, Shang-Shing Peter; Kuo, Yuh-Chi; Chou, Shiu-Huey; Tzeng, Woan-Fang; Leu, Chieh-Yih; Huang, Rwei-Fen S; Liew, Yih-Fong; Wang, Su-Jane

2011-01-01

The present study was aimed at investigating the effect of trans-6-(4-chlorobutyl)-5-hydroxy-4-(phenylthio)-1-tosyl-5,6-dihydropyridine-2(1H)-one (HTDP-2), a novel synthetic compound, on the release of endogenous glutamate in rat cerebrocortical nerve terminals (synaptosomes) and exploring the possible mechanism. The release of glutamate was evoked by the K⁺ channel blocker 4-aminopyridine (4-AP) and measured by an on-line enzyme-coupled fluorimetric assay. We also used a membrane potential-sensitive dye to assay nerve terminal excitability and depolarization, and a Ca²⁺ indicator, Fura-2-acetoxymethyl ester, to monitor cytosolic Ca²⁺ concentrations ([Ca²⁺](c)). HTDP-2 inhibited the release of glutamate evoked by 4-AP in a concentration-dependent manner. Inhibition of glutamate release by HTDP-2 was prevented by the chelating intraterminal Ca²⁺ ions, and by the vesicular transporter inhibitor bafilomycin A1, but was insensitive to the glutamate transporter inhibitor DL-threo-β-benzyloxyaspartate. HTDP-2 did not alter the resting synaptosomal membrane potential or 4-AP-mediated depolarization whereas it decreased the 4-AP-induced increase in [Ca²⁺](c). Furthermore, the inhibitory effect of HTDP-2 on the evoked glutamate release was abolished by the N-, and P/Q-type Ca²⁺ channel blocker ω-conotoxin MVIIC, but not by the ryanodine receptor blocker dantrolene, or the mitochondrial Na⁺/Ca²⁺ exchanger blocker CGP37157. Based on these results, we suggest that, in rat cerebrocortical nerve terminals, HTDP-2 decreases voltage-dependent Ca²⁺ channel activity and, in so doing, inhibits the evoked glutamate release. Copyright © 2011 S. Karger AG, Basel.

Under stressful conditions activation of the ionotropic P2X7 receptor differentially regulates GABA and glutamate release from nerve terminals of the rat cerebral cortex.

PubMed

Barros-Barbosa, Aurora R; Oliveira, Ângela; Lobo, M Graça; Cordeiro, J Miguel; Correia-de-Sá, Paulo

2018-01-01

γ-Aminobutyric acid (GABA) and glutamate (Glu) are the main inhibitory and excitatory neurotransmitters in the central nervous system (CNS), respectively. Fine tuning regulation of extracellular levels of these amino acids is essential for normal brain activity. Recently, we showed that neocortical nerve terminals from patients with epilepsy express higher amounts of the non-desensitizing ionotropic P2X7 receptor. Once activated by ATP released from neuronal cells, the P2X7 receptor unbalances GABAergic vs. glutamatergic neurotransmission by differentially interfering with GABA and Glu uptake. Here, we investigated if activation of the P2X7 receptor also affects [ 3 H]GABA and [ 14 C]Glu release measured synchronously from isolated nerve terminals (synaptosomes) of the rat cerebral cortex. Data show that activation of the P2X7 receptor consistently increases [ 14 C]Glu over [ 3 H]GABA release from cortical nerve terminals, but the GABA/Glu ratio depends on extracellular Ca 2+ concentrations. While the P2X7-induced [ 3 H]GABA release is operated by a Ca 2+ -dependent pathway when external Ca 2+ is available, this mechanism shifts towards the reversal of the GAT1 transporter in low Ca 2+ conditions. A different scenario is verified regarding [ 14 C]Glu outflow triggered by the P2X7 receptor, since the amino acid seems to be consistently released through the recruitment of connexin-containing hemichannels upon P2X7 activation, both in the absence and in the presence of external Ca 2+ . Data from this study add valuable information suggesting that ATP, via P2X7 activation, not only interferes with the high-affinity uptake of GABA and Glu but actually favors the release of these amino acids through distinct molecular mechanisms amenable to differential therapeutic control. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of new fluorinated analogues of GABA, pregabalin bioisosters, on the ambient level and exocytotic release of [3H]GABA from rat brain nerve terminals.

PubMed

Borisova, T; Pozdnyakova, N; Shaitanova, E; Gerus, I; Dudarenko, M; Haufe, G; Kukhar, V

2017-01-15

Recently, we have shown that new fluorinated analogues of γ-aminobutyric acid (GABA), bioisosters of pregabalin (β-i-Bu-GABA), i.e. β-polyfluoroalkyl-GABAs (FGABAs), with substituents: β-CF 3 -β-OH (1), β-CF 3 (2); β-CF 2 CF 2 H (3), are able to increase the initial rate of [ 3 H]GABA uptake by isolated rat brain nerve terminals (synaptosomes), and this effect is higher than that of pregabalin. So, synthesized FGABAs are structural but not functional analogues of GABA. Herein, we assessed the effects of synthesized FGABAs (100μM) on the ambient level and exocytotic release of [ 3 H]GABA in nerve terminals and compared with those of pregabalin (100μM). It was shown that FGABAs 1-3 did not influence the ambient level of [ 3 H]GABA in the synaptosomal preparations, and this parameter was also not altered by pregabalin. During blockage of GABA transporters GAT1 by specific inhibitor NO-711, FGABAs and pregabalin also did not change ambient [ 3 H]GABA in synaptosomal preparations. Exocytotic release of [ 3 H]GABA from synaptosomes decreased in the presence of FGABAs 1-3 and pregabalin, and the effects of FGABAs 1 &3 were more significant than those of FGABAs 2 and pregabalin. FGABAs 1-3/pregabalin-induced decrease in exocytotic release of [ 3 H]GABA from synaptosomes was not a result of changes in the potential of the plasma membrane. Therefore, new synthesized FGABAs 1 &3 were able to decrease exocytotic release of [ 3 H]GABA from nerve terminals more effectively in comparison to pregabalin. Absence of unspecific side effects of FGABAs 1 &3 on the membrane potential makes these compounds perspective for medical application. Copyright © 2016 Elsevier Ltd. All rights reserved.

The clinical toxicology of metamfetamine.

PubMed

Schep, Leo J; Slaughter, Robin J; Beasley, D Michael G

2010-08-01

Metamfetamine is a highly addictive amfetamine analog that acts primarily as a central nervous system (CNS) stimulant. The escalating abuse of this drug in recent years has lead to an increasing burden upon health care providers. An understanding of the drug's toxic effects and their medical treatment is therefore essential for the successful management of patients suffering this form of intoxication. The aim of this review is to summarize all main aspects of metamfetamine poisoning including epidemiology, mechanisms of toxicity, toxicokinetics, clinical features, diagnosis, and management. A summary of the literature on metamfetamine was compiled by systematically searching OVID MEDLINE and ISI Web of Science. Further information was obtained from book chapters, relevant news reports, and web material. Epidemiology. Following its use in the Second World War, metamfetamine gained popularity as an illicit drug in Japan and later the United States. Its manufacture and use has now spread to include East and South-East Asia, North America, Mexico, and Australasia, and its world-wide usage, when combined with amfetamine, exceeds that of all other drugs of abuse except cannabis. Mechanisms of toxicity. Metamfetamine acts principally by stimulating the enhanced release of catecholamines from sympathetic nerve terminals, particularly of dopamine in the mesolimbic, mesocortical, and nigrostriatal pathways. The consequent elevation of intra-synaptic monoamines results in an increased activation of central and peripheral α±- and β-adrenergic postsynaptic receptors. This can cause detrimental neuropsychological, cardiovascular, and other systemic effects, and, following long-term abuse, neuronal apoptosis and nerve terminal degeneration. Toxicokinetics. Metamfetamine is rapidly absorbed and well distributed throughout the body, with extensive distribution across high lipid content tissues such as the blood-brain barrier. In humans the major metabolic pathways are aromatic hydroxylation producing 4-hydroxymetamfetamine and N-demethylation to form amfetamine. Metamfetamine is excreted predominantly in the urine and to a lesser extent by sweating and fecal excretion, with reported terminal half-lives ranging from ∼5 to 30 h. Clinical features. The clinical effects of metamfetamine poisoning can vary widely, depending on dose, route, duration, and frequency of use. They are predominantly characteristic of an acute sympathomimetic toxidrome. Common features reported include tachycardia, hypertension, chest pain, various cardiac dysrhythmias, vasculitis, headache, cerebral hemorrhage, hyperthermia, tachypnea, and violent and aggressive behaviour. Management. Emergency stabilization of vital functions and supportive care is essential. Benzodiazepines alone may adequately relieve agitation, hypertension, tachycardia, psychosis, and seizure, though other specific therapies can also be required for sympathomimetic effects and their associated complications. Metamfetamine may cause severe sympathomimetic effects in the intoxicated patient. However, with appropriate, symptom-directed supportive care, patients can be expected to make a full recovery.

Immunohistochemical localization of FMRFamide-containing neurons and nerve fibers in the ganglia and the gonad wall of the scallop, Pecten maximus (L).

PubMed

Henry, M; Benlinmame, N; Belhsen, O K; Jule, Y; Mathieu, M

1995-02-01

The Phe-Met-Arg-Phe NH2 (FMRFamide)-like immunoreactivity was detected in neurons of the cerebro-pedal and visceral ganglia of the scallop Pecten maximus using immunohistochemical techniques. FMRFamide-like immunoreactivity was also found in nerve fibers localized in the connective tissue and the epithelial wall of the gonad. Electron microscopy study carried out on the gonads indicates the existence of numerous nerve fibers crossing the connective tissue; nerve terminals apposed to highly secretory cells were seen in the gonad wall. All in all, the present immunohistochemical and electron microscopic data suggest that FMRFamide might play an unusual secretagogue role in the gonad wall.

Mechanisms of Kappa Opioid Receptor Potentiation of Dopamine D2 Receptor Function in Quinpirole-Induced Locomotor Sensitization in Rats.

PubMed

Escobar, Angélica P; González, Marcela P; Meza, Rodrigo C; Noches, Verónica; Henny, Pablo; Gysling, Katia; España, Rodrigo A; Fuentealba, José A; Andrés, María E

2017-08-01

Increased locomotor activity in response to the same stimulus is an index of behavioral sensitization observed in preclinical models of drug addiction and compulsive behaviors. Repeated administration of quinpirole, a D2/D3 dopamine agonist, induces locomotor sensitization. This effect is potentiated and accelerated by co-administration of U69593, a kappa opioid receptor agonist. The mechanism underlying kappa opioid receptor potentiation of quinpirole-induced locomotor sensitization remains to be elucidated. Immunofluorescence anatomical studies were undertaken in mice brain slices and rat presynaptic synaptosomes to reveal kappa opioid receptor and D2R pre- and postsynaptic colocalization in the nucleus accumbens. Tonic and phasic dopamine release in the nucleus accumbens of rats repeatedly treated with U69593 and quinpirole was assessed by microdialysis and fast scan cyclic voltammetry. Anatomical data show that kappa opioid receptor and D2R colocalize postsynaptically in medium spiny neurons of the nucleus accumbens and the highest presynaptic colocalization occurs on the same dopamine terminals. Significantly reduced dopamine levels were observed in quinpirole, and U69593-quinpirole treated rats, explaining sensitization of D2R. Presynaptic inhibition induced by kappa opioid receptor and D2R of electrically evoked dopamine release was faster in U69593-quinpirole compared with quinpirole-repeatedly treated rats. Pre- and postsynaptic colocalization of kappa opioid receptor and D2R supports a role for kappa opioid receptor potentiating both the D2R inhibitory autoreceptor function and the inhibitory action of D2R on efferent medium spiny neurons. Kappa opioid receptor co-activation accelerates D2R sensitization by contributing to decrease dopamine release in the nucleus accumbens. © The Author 2017. Published by Oxford University Press on behalf of CINP.

Encoding of aversion by dopamine and the nucleus accumbens.

PubMed

McCutcheon, James E; Ebner, Stephanie R; Loriaux, Amy L; Roitman, Mitchell F

2012-01-01

Adaptive motivated behavior requires rapid discrimination between beneficial and harmful stimuli. Such discrimination leads to the generation of either an approach or rejection response, as appropriate, and enables organisms to maximize reward and minimize punishment. Classically, the nucleus accumbens (NAc) and the dopamine projection to it are considered an integral part of the brain's reward circuit, i.e., they direct approach and consumption behaviors and underlie positive reinforcement. This reward-centered framing ignores important evidence about the role of this system in encoding aversive events. One reason for bias toward reward is the difficulty in designing experiments in which animals repeatedly experience punishments; another is the challenge in dissociating the response to an aversive stimulus itself from the reward/relief experienced when an aversive stimulus is terminated. Here, we review studies that employ techniques with sufficient time resolution to measure responses in ventral tegmental area and NAc to aversive stimuli as they are delivered. We also present novel findings showing that the same stimulus - intra-oral infusion of sucrose - has differing effects on NAc shell dopamine release depending on the prior experience. Here, for some rats, sucrose was rendered aversive by explicitly pairing it with malaise in a conditioned taste aversion paradigm. Thereafter, sucrose infusions led to a suppression of dopamine with a similar magnitude and time course to intra-oral infusions of a bitter quinine solution. The results are discussed in the context of regional differences in dopamine signaling and the implications of a pause in phasic dopamine release within the NAc shell. Together with our data, the emerging literature suggests an important role for differential phasic dopamine signaling in aversion vs. reward.

Substance P released from intrinsic airway neurons contributes to ozone-enhanced airway hyperresponsiveness in ferret trachea.

PubMed

Wu, Zhong-Xin; Satterfield, Brian E; Dey, Richard D

2003-08-01

Exposure to ozone (O3) induces airway hyperresponsiveness mediated partly through the release of substance P (SP) from nerve terminals in the airway wall. Although substantial evidence suggests that SP is released by sensory nerves, SP is also present in neurons of airway ganglia. The purpose of this study was to investigate the role of intrinsic airway neurons in O3-enhanced airway responsiveness in ferret trachea. To remove the effects of sensory innervation, segments of ferret trachea were maintained in culture conditions for 24 h before in vitro exposure to 2 parts/million of O3 or air for 1 h. Sensory nerve depletion was confirmed by showing that capsaicin did not affect tracheal smooth muscle responsiveness to cholinergic agonist or contractility responses to electrical field stimulation (EFS). Contractions of isolated tracheal smooth muscle to EFS were significantly increased after in vitro O3 exposure, but the constrictor response to cholinergic agonist was not altered. Pretreatment with CP-99994, an antagonist of the neurokinin 1 receptor, attenuated the increased contraction to EFS after O3 exposure but had no effect in the air exposure group. The number of SP-positive neurons in longitudinal trunk ganglia, the extent of SP innervation to superficial muscular plexus nerve cell bodies, and SP nerve fiber density in tracheal smooth muscle all increased significantly after O3 exposure. The results show that release of SP from intrinsic airway neurons contributes to O3-enhanced tracheal smooth muscle responsiveness by facilitating acetylcholine release from cholinergic nerve terminals.

Biophysical characterization of interactions between the C-termini of peripheral nerve claudins and the PDZ₁ domain of zonula occludens.

PubMed

Wu, Jiawen; Peng, Dungeng; Zhang, Yang; Lu, Zhenwei; Voehler, Markus; Sanders, Charles R; Li, Jun

2015-03-27

Our recent study has shown that cellular junctions in myelin and in the epi-/perineruium that encase nerve fibers regulate the permeability of the peripheral nerves. This permeability may affect propagation of the action potential. Direct interactions between the PDZ₁ domain of zonula occludens (ZO₁ or ZO₂) and the C-termini of claudins are known to be crucial for the formation of tight junctions. Using the purified PDZ₁ domain of ZO₂ and a variety of C-terminal mutants of peripheral nerve claudins (claudin-1, claudin-2, claudin-3, claudin-5 in epi-/perineurium; claudin-19 in myelin), we have utilized NMR spectroscopy to determine specific roles of the 3 C-terminal claudin residues (position -2, -1, 0) for their interactions with PDZ₁ of ZO₂. In contrast to the canonical model that emphasizes the importance of residues at the -2 and 0 positions, our results demonstrate that, for peripheral nerve claudins, the residue at position -1 plays a critical role in association with PDZ₁, while the side-chain of residue 0 plays a significant but lesser role. Surprisingly, claudin-19, the most abundant claudin in myelin, exhibited no binding to ZO₂. These findings reveal that the binding mechanism of claudin/ZO in epi-/perineurium is distinct from the canonical interactions between non-ZO PDZ-containing proteins with their ligands. This observation provides the molecular basis for a strategy to develop drugs that target tight junctions in the epi-/perineurium of peripheral nerves. Published by Elsevier Inc.

Rehabilitation, Using Guided Cerebral Plasticity, of a Brachial Plexus Injury Treated with Intercostal and Phrenic Nerve Transfers.

PubMed

Dahlin, Lars B; Andersson, Gert; Backman, Clas; Svensson, Hampus; Björkman, Anders

2017-01-01

Recovery after surgical reconstruction of a brachial plexus injury using nerve grafting and nerve transfer procedures is a function of peripheral nerve regeneration and cerebral reorganization. A 15-year-old boy, with traumatic avulsion of nerve roots C5-C7 and a non-rupture of C8-T1, was operated 3 weeks after the injury with nerve transfers: (a) terminal part of the accessory nerve to the suprascapular nerve, (b) the second and third intercostal nerves to the axillary nerve, and (c) the fourth to sixth intercostal nerves to the musculocutaneous nerve. A second operation-free contralateral gracilis muscle transfer directly innervated by the phrenic nerve-was done after 2 years due to insufficient recovery of the biceps muscle function. One year later, electromyography showed activation of the biceps muscle essentially with coughing through the intercostal nerves, and of the transferred gracilis muscle by deep breathing through the phrenic nerve. Voluntary flexion of the elbow elicited clear activity in the biceps/gracilis muscles with decreasing activity in intercostal muscles distal to the transferred intercostal nerves (i.e., corresponding to eighth intercostal), indicating cerebral plasticity, where neural control of elbow flexion is gradually separated from control of breathing. To restore voluntary elbow function after nerve transfers, the rehabilitation of patients operated with intercostal nerve transfers should concentrate on transferring coughing function, while patients with phrenic nerve transfers should focus on transferring deep breathing function.

Microsurgical anatomy of the trochlear nerve.

PubMed

Joo, Wonil; Rhoton, Albert L

2015-10-01

The trochlear nerve is the cranial nerve with the longest intracranial course, but also the thinnest. It is the only nerve that arises from the dorsal surface of the brainstem and decussates in the superior medullary velum. After leaving the dorsal surface of the brainstem, it courses anterolaterally around the lateral surface of the brainstem and then passes anteriorly just beneath the free edge of the tentorium. It passes forward to enter the cavernous sinus, traverses the superior orbital fissure and terminates in the superior oblique muscle in the orbit. Because of its small diameter and its long course, the trochlear nerve can easily be injured during surgical procedures. Therefore, precise knowledge of its surgical anatomy and its neurovascular relationships is essential for approaching and removing complex lesions of the orbit and the middle and posterior fossae safely. This review describes the microsurgical anatomy of the trochlear nerve and is illustrated with pictures involving the nerve and its surrounding connective and neurovascular structures. © 2015 Wiley Periodicals, Inc.

Mu-opiate receptor and Beta-endorphin expression in nerve endings and keratinocytes in human skin.

PubMed

Bigliardi-Qi, M; Sumanovski, L T; Büchner, S; Rufli, T; Bigliardi, P L

2004-01-01

We have previously shown that human epidermal keratinocytes express a functionally active micro-opiate receptor, which adds a new dimension to the recently developed research in neuroimmunodermatology and neurogenic inflammation in skin diseases. Human keratinocytes specifically bind and also produce beta-endorphin, the endogenous micro-opiate receptor ligand. Using confocal imaging microscopy, we could now demonstrate that micro-opiate receptors are not only expressed in keratinocytes, but also on unmyelinated peripheral nerve fibers in the dermis and epidermis. Some of the peripheral nerve fibers also express the ligand beta-endorphin. The keratinocytes positive for beta-endorphin staining are clustered around the terminal ends of the unmyelinated nerve fibers. Therefore the opiate receptor system seems to be crucial in the direct communication between nerves and skin. The keratinocytes can influence the unmyelinated nerve fibers in the epidermis directly via secreting beta-endorphin. On the other hand, nerve fibers can also secrete beta-endorphin and influence the migration, differentiation and probably also the cytokine production pattern of keratinocytes.

Flow Cytometric Analysis of Presynaptic Nerve Terminals Isolated from Rats Subjected to Hypergravity

NASA Astrophysics Data System (ADS)

Borisova, Tatiana

2008-06-01

Flow cytometric studies revealed an insignificant decrease in cell size heterogeneity and cytoplasmic granularity of rat brain nerve terminals (synaptosomes) isolated from animals subjected to centrifuge-induced hypergravity as compared to control ones. The analysis of plasma membrane potential using the potentiometric optical dye rhodamine 6G showed a decrease in fluorescence intensity by 10 % at steady state level in hypergravity synaptosomes. To monitor synaptic vesicle acidification we used pH-sensitive fluorescent dye acridine orange and demonstrated a lower fluorescence intensity level at steady state (10%) after hypergravity as compared to controls. Thus, exposure to hypergravity resulted in depolarization of the synaptosomal plasma membrane and diminution in synaptic vesicle acidification that may be a cause leading to altered synaptic neurotransmission.

Synaptic Activity and Muscle Contraction Increases PDK1 and PKCβI Phosphorylation in the Presynaptic Membrane of the Neuromuscular Junction.

PubMed

Hurtado, Erica; Cilleros, Víctor; Just, Laia; Simó, Anna; Nadal, Laura; Tomàs, Marta; Garcia, Neus; Lanuza, Maria A; Tomàs, Josep

2017-01-01

Conventional protein kinase C βI (cPKCβI) is a conventional protein kinase C (PKC) isoform directly involved in the regulation of neurotransmitter release in the neuromuscular junction (NMJ). It is located exclusively at the nerve terminal and both synaptic activity and muscle contraction modulate its protein levels and phosphorylation. cPKCβI molecular maturation includes a series of phosphorylation steps, the first of which is mediated by phosphoinositide-dependent kinase 1 (PDK1). Here, we sought to localize PDK1 in the NMJ and investigate the hypothesis that synaptic activity and muscle contraction regulate in parallel PDK1 and cPKCβI phosphorylation in the membrane fraction. To differentiate the presynaptic and postsynaptic activities, we abolished muscle contraction with μ-conotoxin GIIIB (μ-CgTx-GIIIB) in some experiments before stimulation of the phrenic nerve (1 Hz, 30 min). Then, we analyzed total and membrane/cytosol fractions of skeletal muscle by Western blotting. Results showed that PDK1 is located exclusively in the nerve terminal of the NMJ. After nerve stimulation with and without coincident muscle contraction, total PDK1 and phosphorylated PDK1 (pPDK1) protein levels remained unaltered. However, synaptic activity specifically enhanced phosphorylation of PDK1 in the membrane, an important subcellular location for PDK1 function. This increase in pPDK1 coincides with a significant increase in the phosphorylation of its substrate cPKCβI also in the membrane fraction. Moreover, muscle contraction maintains PDK1 and pPDK1 but increases cPKCβI protein levels and its phosphorylation. Thus, even though PDK1 activity is maintained, pcPKCβI levels increase in concordance with total cPKCβI. Together, these results indicate that neuromuscular activity could induce the membrane targeting of pPDK1 in the nerve terminal of the NMJ to promote the phosphorylation of the cPKCβI, which is involved in ACh release.

Synaptic Activity and Muscle Contraction Increases PDK1 and PKCβI Phosphorylation in the Presynaptic Membrane of the Neuromuscular Junction

PubMed Central

Hurtado, Erica; Cilleros, Víctor; Just, Laia; Simó, Anna; Nadal, Laura; Tomàs, Marta; Garcia, Neus; Lanuza, Maria A.; Tomàs, Josep

2017-01-01

Conventional protein kinase C βI (cPKCβI) is a conventional protein kinase C (PKC) isoform directly involved in the regulation of neurotransmitter release in the neuromuscular junction (NMJ). It is located exclusively at the nerve terminal and both synaptic activity and muscle contraction modulate its protein levels and phosphorylation. cPKCβI molecular maturation includes a series of phosphorylation steps, the first of which is mediated by phosphoinositide-dependent kinase 1 (PDK1). Here, we sought to localize PDK1 in the NMJ and investigate the hypothesis that synaptic activity and muscle contraction regulate in parallel PDK1 and cPKCβI phosphorylation in the membrane fraction. To differentiate the presynaptic and postsynaptic activities, we abolished muscle contraction with μ-conotoxin GIIIB (μ-CgTx-GIIIB) in some experiments before stimulation of the phrenic nerve (1 Hz, 30 min). Then, we analyzed total and membrane/cytosol fractions of skeletal muscle by Western blotting. Results showed that PDK1 is located exclusively in the nerve terminal of the NMJ. After nerve stimulation with and without coincident muscle contraction, total PDK1 and phosphorylated PDK1 (pPDK1) protein levels remained unaltered. However, synaptic activity specifically enhanced phosphorylation of PDK1 in the membrane, an important subcellular location for PDK1 function. This increase in pPDK1 coincides with a significant increase in the phosphorylation of its substrate cPKCβI also in the membrane fraction. Moreover, muscle contraction maintains PDK1 and pPDK1 but increases cPKCβI protein levels and its phosphorylation. Thus, even though PDK1 activity is maintained, pcPKCβI levels increase in concordance with total cPKCβI. Together, these results indicate that neuromuscular activity could induce the membrane targeting of pPDK1 in the nerve terminal of the NMJ to promote the phosphorylation of the cPKCβI, which is involved in ACh release. PMID:28890686

Cholinergic Nociceptive Mechanisms in Rat Meninges and Trigeminal Ganglia: Potential Implications for Migraine Pain.

PubMed

Shelukhina, Irina; Mikhailov, Nikita; Abushik, Polina; Nurullin, Leniz; Nikolsky, Evgeny E; Giniatullin, Rashid

2017-01-01

Parasympathetic innervation of meninges and ability of carbachol, acetylcholine (ACh) receptor (AChR) agonist, to induce headaches suggests contribution of cholinergic mechanisms to primary headaches. However, neurochemical mechanisms of cholinergic regulation of peripheral nociception in meninges, origin place for headache, are almost unknown. Using electrophysiology, calcium imaging, immunohistochemistry, and staining of meningeal mast cells, we studied effects of cholinergic agents on peripheral nociception in rat hemiskulls and isolated trigeminal neurons. Both ACh and carbachol significantly increased nociceptive firing in peripheral terminals of meningeal trigeminal nerves recorded by local suction electrode. Strong nociceptive firing was also induced by nicotine, implying essential role of nicotinic AChRs in control of excitability of trigeminal nerve endings. Nociceptive firing induced by carbachol was reduced by muscarinic antagonist atropine, whereas the action of nicotine was prevented by the nicotinic blocker d-tubocurarine but was insensitive to the TRPA1 antagonist HC-300033. Carbachol but not nicotine induced massive degranulation of meningeal mast cells known to release multiple pro-nociceptive mediators. Enzymes terminating ACh action, acetylcholinesterase (AChE) and butyrylcholinesterase, were revealed in perivascular meningeal nerves. The inhibitor of AChE neostigmine did not change the firing per se but induced nociceptive activity, sensitive to d-tubocurarine, after pretreatment of meninges with the migraine mediator CGRP. This observation suggested the pro-nociceptive action of endogenous ACh in meninges. Both nicotine and carbachol induced intracellular Ca 2+ transients in trigeminal neurons partially overlapping with expression of capsaicin-sensitive TRPV1 receptors. Trigeminal nerve terminals in meninges, as well as dural mast cells and trigeminal ganglion neurons express a repertoire of pro-nociceptive nicotinic and muscarinic AChRs, which could be activated by the ACh released from parasympathetic nerves. These receptors represent a potential target for novel therapeutic interventions in trigeminal pain and probably in migraine.

Characterization of an Invertebrate-Type Dopamine Receptor of the American Cockroach, Periplaneta americana

PubMed Central

Troppmann, Britta; Balfanz, Sabine; Krach, Christian; Baumann, Arnd; Blenau, Wolfgang

2014-01-01

We have isolated a cDNA coding for a putative invertebrate-type dopamine receptor (Peadop2) from P. americana brain by using a PCR-based strategy. The mRNA is present in samples from brain and salivary glands. We analyzed the distribution of the PeaDOP2 receptor protein with specific affinity-purified polyclonal antibodies. On Western blots, PeaDOP2 was detected in protein samples from brain, subesophageal ganglion, thoracic ganglia, and salivary glands. In immunocytochemical experiments, we detected PeaDOP2 in neurons with their somata being located at the anterior edge of the medulla bilaterally innervating the optic lobes and projecting to the ventro-lateral protocerebrum. In order to determine the functional and pharmacological properties of the cloned receptor, we generated a cell line constitutively expressing PeaDOP2. Activation of PeaDOP2-expressing cells with dopamine induced an increase in intracellular cAMP. In contrast, a C-terminally truncated splice variant of this receptor did not exhibit any functional property by itself. The molecular and pharmacological characterization of the first dopamine receptor from P. americana provides the basis for forthcoming studies focusing on the significance of the dopaminergic system in cockroach behavior and physiology. PMID:24398985

Characterization of an invertebrate-type dopamine receptor of the American cockroach, Periplaneta americana.

PubMed

Troppmann, Britta; Balfanz, Sabine; Krach, Christian; Baumann, Arnd; Blenau, Wolfgang

2014-01-06

We have isolated a cDNA coding for a putative invertebrate-type dopamine receptor (Peadop2) from P. americana brain by using a PCR-based strategy. The mRNA is present in samples from brain and salivary glands. We analyzed the distribution of the PeaDOP2 receptor protein with specific affinity-purified polyclonal antibodies. On Western blots, PeaDOP2 was detected in protein samples from brain, subesophageal ganglion, thoracic ganglia, and salivary glands. In immunocytochemical experiments, we detected PeaDOP2 in neurons with their somata being located at the anterior edge of the medulla bilaterally innervating the optic lobes and projecting to the ventro-lateral protocerebrum. In order to determine the functional and pharmacological properties of the cloned receptor, we generated a cell line constitutively expressing PeaDOP2. Activation of PeaDOP2-expressing cells with dopamine induced an increase in intracellular cAMP. In contrast, a C-terminally truncated splice variant of this receptor did not exhibit any functional property by itself. The molecular and pharmacological characterization of the first dopamine receptor from P. americana provides the basis for forthcoming studies focusing on the significance of the dopaminergic system in cockroach behavior and physiology.

Development of peptide-containing nerves in the human fetal prostate gland.

PubMed

Jen, P Y; Dixon, J S

1995-08-01

Immunohistochemical methods were used to study the developing peptidergic innervation of the human fetal prostate gland in a series of specimens ranging in gestational age from 13 to 30 wk. The overall innervation of each specimen was visualised using protein gene product 9.5 (PGP), a general nerve marker. The onset and development of specific neuropeptide-containing subpopulations were investigated using antisera to neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP), bombesin (BOM), somatostatin (SOM), leu-enkephalin (l-ENK) and met-enkephalin (m-ENK). In addition the occurrence and distribution of presumptive noradrenergic nerves was studied using antisera to dopamine-beta-hydroxylase (D beta H) and tyrosine hydroxylase (TH). At 13 wk numerous branching PGP-immunoreactive (-IR) nerves were observed in the capsule of the developing prostate gland and surrounding the preprostatic urethra but the remainder of the gland was devoid of nerves. The majority of nerves in the capsule contained D beta H and TH and were presumed to be noradrenergic in type while other nerves (in decreasing numbers) contained NPY, l-ENK, SP and CGRP. Nerves associated with the preprostatic urethra did not contain any of the neuropeptides under investigation. At 17 wk the density of nerves in the capsule had increased and occasional m-ENK-, VIP- and BOM-IR nerve fibres were also observed. In addition PGP, D beta H-, TH-, NPY- and l-ENK-IR nerves occurred in association with smooth muscle bundles which at 17 wk were present in the outer part of the gland. Occasional PGP-IR nerves were also present at the base of the epithelium forming some of the prostatic glands. At 23 wk some of the subepithelial nerves showed immunoreactivity for NPY, VIP or l-ENK. At 26 wk smooth muscle bundles occurred throughout the gland and were richly innervated by PGP, D beta H and TH-IR nerves while a less dense plexus was formed by NPY- and l-ENK-IR nerves together with a few m-ENK-IR nerves. Occasional smooth muscle-associated varicose nerve fibres showed immunoreactivity for SP, CGRP, VIP or BOM although the majority of these types of nerve formed perivascular plexuses. Also at 26 wk numerous varicose nerve fibres were observed in association with the prostatic acini, the majority of such nerves containing NPY with a few showing immunoreactivity to VIP, l-ENK, SP or CGRP.(ABSTRACT TRUNCATED AT 400 WORDS)

Communicating branches between lingual and hypoglossal nerve: observation using Sihler's staining technique.

PubMed

Iwanaga, Joe; Watanabe, Koichi; Saga, Tsuyoshi; Tabira, Yoko; Nakamura, Moriyoshi; Fisahn, Christian; Tubbs, R Shane; Kusukawa, Jingo; Yamaki, Koh-Ichi

2017-07-01

Many dental procedures are at risk of injuring the lingual nerve. We performed this study to better elucidate the microanatomy that exists between the ipsilateral lingual and hypoglossal nerves so that iatrogenic injury can be avoided. Adult human cadaveric tongues (ten sides) underwent Sihler's staining to identify the microanatomy between the lingual and hypoglossal nerves. The lingual nerve entered the middle part of the anterior two-thirds of the tongue from its lateral side and divided into two to four thick branches. These branches were then disseminated to the anterior, middle, and posterior parts of the anterior two-thirds of the tongue via 7-14 thin nerve bundles as terminal branches. The hypoglossal nerve entered the tongue at the posterior border of its anterior two-thirds and traveled forward to the apex of the tongue on all sides. All specimens were found to have communicating branches between the lingual and hypoglossal nerves at its anterior, middle, and posterior thirds. Our results indicate that the ipsilateral lingual and hypoglossal nerves constantly have three connections on each side between them. This knowledge might aid the dentist in minimizing iatrogenic nerve injury.

Glutamate synaptic inputs to ventral tegmental area neurons in the rat derive primarily from subcortical sources.

PubMed

Omelchenko, N; Sesack, S R

2007-05-25

Dopamine and GABA neurons in the ventral tegmental area project to the nucleus accumbens and prefrontal cortex and modulate locomotor and reward behaviors as well as cognitive and affective processes. Both midbrain cell types receive synapses from glutamate afferents that provide an essential control of behaviorally-linked activity patterns, although the sources of glutamate inputs have not yet been completely characterized. We used antibodies against the vesicular glutamate transporter subtypes 1 and 2 (VGlut1 and VGlut2) to investigate the morphology and synaptic organization of axons containing these proteins as putative markers of glutamate afferents from cortical versus subcortical sites, respectively, in rats. We also characterized the ventral tegmental area cell populations receiving VGlut1+ or VGlut2+ synapses according to their transmitter phenotype (dopamine or GABA) and major projection target (nucleus accumbens or prefrontal cortex). By light and electron microscopic examination, VGlut2+ as opposed to VGlut1+ axon terminals were more numerous, had a larger average size, synapsed more proximally, and were more likely to form convergent synapses onto the same target. Both axon types formed predominantly asymmetric synapses, although VGlut2+ terminals more often formed synapses with symmetric morphology. No absolute selectivity was observed for VGlut1+ or VGlut2+ axons to target any particular cell population. However, the synapses onto mesoaccumbens neurons more often involved VGlut2+ terminals, whereas mesoprefrontal neurons received relatively equal synaptic inputs from VGlut1+ and VGlut2+ profiles. The distinct morphological features of VGlut1 and VGlut2 positive axons suggest that glutamate inputs from presumed cortical and subcortical sources, respectively, differ in the nature and intensity of their physiological actions on midbrain neurons. More specifically, our findings imply that subcortical glutamate inputs to the ventral tegmental area expressing VGlut2 predominate over cortical sources of excitation expressing VGlut1 and are more likely to drive the behaviorally-linked bursts in dopamine cells that signal future expectancy or attentional shifting.

Terminal changes in hereditary sensory and autonomic neuropathy: a long-term follow-up of a sporadic case.

PubMed

Lee, Sang-Soo; Lee, Sung-Hyun; Han, Seol-Heui

2003-07-01

We describe terminal changes in a long-term follow-up of a 51-year-old man with sporadic hereditary sensory and autonomic neuropathy (HSAN). From the age of 15 years onwards, he suffered from multiple painless ulcers of his feet and fingers, necessitating amputation. Neurological studies revealed almost complete sensory loss affecting all modalities in the upper and lower limbs, minimal involvement of motor fibers, and areflexia. A neurophysiological abnormality involved an absence of sensory action potentials with relatively normal motor nerve conduction velocities. Biopsy of the sural nerve showed almost total loss of myelinated fibers with a mild decrease in unmyelinated fibers. Despite the late onset of the disease, the progressive course, and the lancinating pain, the terminal features of this patient, which involved a selective loss of myelinated fibers and widespread sensory loss, seem to be symptomatic of HSAN II, the progressive form of autosomal recessive sensory neuropathy, and emphasize the clinical heterogeneity of HSAN.

A rare case of recurrent vasodepressive attacks of 2-hours duration: analysis of the mechanism by muscle sympathetic nerve activity recording.

PubMed

Yatomi, A; Iguchi, A; Uemura, K; Sakamoto, N; Iwase, S; Mano, T

1989-03-01

Muscle sympathetic nerve activity was recorded in a 57-year-old male patient suffering from severe hypotensive attacks with bradycardia for 10 years. Continuous blood pressure recording demonstrated frequent drastic falls in pressure. Disappearance and reappearance of muscle sympathetic nerve activity coincided with the onset and termination of attacks. Awakening from sleep or emotional and/or cardiovascular stress seems to trigger hypotension. Cardiac pacemaker was not useful in limiting the attack, because right ventricular pacing caused abrupt falls in both blood pressure and heart rate.

[Neurotransmission in developmental disorders].

PubMed

Takeuchi, Yoshihiro

2008-11-01

Attention deficit/hyperactivity disorder (AD/HD) is a heterogeneous developmental disorder with an etiology that is not fully understood. AD/HD has been considered to occur due to a disturbance in cathecholaminergic neurotransmission, with particular emphasis on dopamine. The neurotransmission of dopamine in subcortical regions such as the basal ganglia and limbic areas is synaptic; on the other hand, dopamine neurotransmission in the frontal cortex is quite different, because there are very few dopamine transporters (DAT) in the frontal cortex that allow dopamine to diffuse away from the dopamine synapse ("volume transmission"). It is now clear that noradrenergic neurons play a key regulatory role in dopaminergic function in the frontal cortex. Furthermore, serotonergic neurons exert an inhibitory effect on midbrain dopamine cell bodies, and they have an influence on dopamine release in terminal regions. There is accumulating neurobiological evidence pointing toward a role of the serotonin system in AD/HD. The etiology of autism spectrum disorders (ASD) is still unclear, but information from genetics, neuropathology, brain imaging, and basic neuroscience has provided insights into the understanding of this developmental disorder. In addition to abnormal circuitry in specific limbic and neocortical areas of the cerebral cortex, impairments in brainstem, cerebellar, thalamic, and basal ganglia connections have been reported. Numerous studies have pointed to abnormalities in serotonin and glutamate neurotransmission. Three important aspects involved in the pathophysiology of ASD have been proposed. The first is cell migration, the second is unbalanced excitatory-inhibitory networks, and the third is synapse formation and pruning, the key factors being reelin, neurexin, and neuroligin. Serotonin is considered to play an important role in all of these aspects of the pathophysiology of ASD. Finally, I would like to emphasize that it is crucial in the field of child neurology medical examination and treatment should be based on the basic neuroscience, always taking "neurons" into consideration.

Evidence for recycling of synaptic vesicle membrane during transmitter release at the frog neuromuscular junction.

PubMed

Heuser, J E; Reese, T S

1973-05-01

When the nerves of isolated frog sartorius muscles were stimulated at 10 Hz, synaptic vesicles in the motor nerve terminals became transiently depleted. This depletion apparently resulted from a redistribution rather than disappearance of synaptic vesicle membrane, since the total amount of membrane comprising these nerve terminals remained constant during stimulation. At 1 min of stimulation, the 30% depletion in synaptic vesicle membrane was nearly balanced by an increase in plasma membrane, suggesting that vesicle membrane rapidly moved to the surface as it might if vesicles released their content of transmitter by exocytosis. After 15 min of stimulation, the 60% depletion of synaptic vesicle membrane was largely balanced by the appearance of numerous irregular membrane-walled cisternae inside the terminals, suggesting that vesicle membrane was retrieved from the surface as cisternae. When muscles were rested after 15 min of stimulation, cisternae disappeared and synaptic vesicles reappeared, suggesting that cisternae divided to form new synaptic vesicles so that the original vesicle membrane was now recycled into new synaptic vesicles. When muscles were soaked in horseradish peroxidase (HRP), this tracerfirst entered the cisternae which formed during stimulation and then entered a large proportion of the synaptic vesicles which reappeared during rest, strengthening the idea that synaptic vesicle membrane added to the surface was retrieved as cisternae which subsequently divided to form new vesicles. When muscles containing HRP in synaptic vesicles were washed to remove extracellular HRP and restimulated, HRP disappeared from vesicles without appearing in the new cisternae formed during the second stimulation, confirming that a one-way recycling of synaptic membrane, from the surface through cisternae to new vesicles, was occurring. Coated vesicles apparently represented the actual mechanism for retrieval of synaptic vesicle membrane from the plasma membrane, because during nerve stimulation they proliferated at regions of the nerve terminals covered by Schwann processes, took up peroxidase, and appeared in various stages of coalescence with cisternae. In contrast, synaptic vesicles did not appear to return directly from the surface to form cisternae, and cisternae themselves never appeared directly connected to the surface. Thus, during stimulation the intracellular compartments of this synapse change shape and take up extracellular protein in a manner which indicates that synaptic vesicle membrane added to the surface during exocytosis is retrieved by coated vesicles and recycled into new synaptic vesicles by way of intermediate cisternae.

EVIDENCE FOR RECYCLING OF SYNAPTIC VESICLE MEMBRANE DURING TRANSMITTER RELEASE AT THE FROG NEUROMUSCULAR JUNCTION

PubMed Central

Heuser, J. E.; Reese, T. S.

1973-01-01

When the nerves of isolated frog sartorius muscles were stimulated at 10 Hz, synaptic vesicles in the motor nerve terminals became transiently depleted. This depletion apparently resulted from a redistribution rather than disappearance of synaptic vesicle membrane, since the total amount of membrane comprising these nerve terminals remained constant during stimulation. At 1 min of stimulation, the 30% depletion in synaptic vesicle membrane was nearly balanced by an increase in plasma membrane, suggesting that vesicle membrane rapidly moved to the surface as it might if vesicles released their content of transmitter by exocytosis. After 15 min of stimulation, the 60% depletion of synaptic vesicle membrane was largely balanced by the appearance of numerous irregular membrane-walled cisternae inside the terminals, suggesting that vesicle membrane was retrieved from the surface as cisternae. When muscles were rested after 15 min of stimulation, cisternae disappeared and synaptic vesicles reappeared, suggesting that cisternae divided to form new synaptic vesicles so that the original vesicle membrane was now recycled into new synaptic vesicles. When muscles were soaked in horseradish peroxidase (HRP), this tracerfirst entered the cisternae which formed during stimulation and then entered a large proportion of the synaptic vesicles which reappeared during rest, strengthening the idea that synaptic vesicle membrane added to the surface was retrieved as cisternae which subsequently divided to form new vesicles. When muscles containing HRP in synaptic vesicles were washed to remove extracellular HRP and restimulated, HRP disappeared from vesicles without appearing in the new cisternae formed during the second stimulation, confirming that a one-way recycling of synaptic membrane, from the surface through cisternae to new vesicles, was occurring. Coated vesicles apparently represented the actual mechanism for retrieval of synaptic vesicle membrane from the plasma membrane, because during nerve stimulation they proliferated at regions of the nerve terminals covered by Schwann processes, took up peroxidase, and appeared in various stages of coalescence with cisternae. In contrast, synaptic vesicles did not appear to return directly from the surface to form cisternae, and cisternae themselves never appeared directly connected to the surface. Thus, during stimulation the intracellular compartments of this synapse change shape and take up extracellular protein in a manner which indicates that synaptic vesicle membrane added to the surface during exocytosis is retrieved by coated vesicles and recycled into new synaptic vesicles by way of intermediate cisternae. PMID:4348786

Inhibitory effects of HgCl2 on excitation-secretion coupling at the motor nerve terminal and excitation-contraction coupling in the muscle cell.

PubMed

Røed, A; Herlofson, B B

1994-12-01

1. Indirect and direct twitch (0.1-Hz) stimulation of the rat phrenic nerve-diaphragm disclosed that the inhibitory effect of HgCl2, 3.7 x 10(-5) M, on the neuromuscular transmission and in the muscle cell, was accelerated by 10-sec periods of 50-Hz tetanic stimulation every 10 min. This activity-dependent enhancement suggested an inhibitory mechanism of HgCl2 related to the development of fatigue, like membrane depolarization or decreased excitability, decreased availability of transmitter, or interference with the factors controlling excitation-secretion coupling of the nerve terminal, i.e. (Ca2+)0 or (Ca2+)i, and excitation-contraction coupling in the muscle cell, i.e., (Ca2+)i. 2. During both indirect and direct stimulation, HgCl2-induced inhibition was enhanced markedly by pretreatment with caffeine, which releases Ca2+ from endoplasmic and sarcoplasmic reticulum in the nerve terminal and muscle cell, respectively. This caffeine-induced enhancement was completely antagonized by dantrolene, which inhibits the caffeine-induced release. However, dantrolene alone did not antagonize the HgCl2-induced inhibition. 3. Since caffeine depletes the intracellular Ca2+ stores of the smooth endoplasmic reticulum, HgCl2 probably inhibits by binding to SH groups of transport proteins conveying the messenger function of (Ca2+)i. In the muscle cell this leads to inhibition of contraction. In the nerve terminal, an additional enhancement of the HgCl2-induced inhibition, by inhibiting reuptake of choline by TEA and tetanic stimulation, suggested that HgCl2 inhibited a (Ca2+)i signal necessary for this limiting factor in resynthesis of acetylcholine. 4. The (Ca2+)0 signal necessary for stimulus-induced release of acetylcholine was not affected by HgCl2. Hyperpolarization in K(+)-free solution antagonized the inhibitory effect of HgCl2 at indirect stimulation, and Ca(2+)-free solution enhanced the inhibitory effect at direct stimulation. K+ depolarization, membrane electric field increase with high Ca2+, membrane stabilization with lidocaine, and half-threshold stimulation, did not change the inhibitory effect of HgCl CH3HgCl. 1.85 x 10(-5) M, disclosed a synergistic interaction with caffeine during direct, but not during indirect, stimulation.

Neurochemical and neuroanatomic effects of 3,4-methylenedioxymethamphetamine (MDMA) in rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Virus, R.; Commins, D.; Vosmer, G.

1986-03-05

Rats injected s.c. twice daily for 4 consecutive days with 10,20, or 40 mg/kg MDMA or saline and sacrificed 2 weeks after the last injection showed dose-dependent reductions in serotonin (5-HT) concentrations in hypothalamus, hippocampus (HIP), striatum (STR), somatosensory cortex (SC) and other cortical areas (CTX). 5-HT depletion was maximal in HIP (11.5 +/- 1.7%) and SC (15.3 +/- 3.2%, p<0.001 in both cases) at the 40 mg/kg MDMA dose. Forty mg/kg MDMA also reduced the amounts of dopamine (DA) in STR (78.2 +/- 6.4%, p<0.001) and of norepinephrine (NE) in HIP (74.5 +/- 6.4%, P<0.025) and CTX (77.9 +/-more » 6.1%, p<0.05). In addition, 20 mg/kg MDMA markedly reduced the number of (/sup 3/H)5-HT uptake sites (V/sub max/ 35.2% of control) without affecting the affinity (K/sub m/) in HIP. Fink-Heimer staining showed that rats injected s.c. twice daily for 2 days with 80 mg/kg MDMA had greater degeneration of nerve terminals in STR (p<0.005) and pyramidal cells in Layer III of SC (p<0.01) than did control rats. These results clearly suggest that repeated exposure to MDMA selectively damages serotonergic neurons in the central nervous system of rats.« less

Sound damage and gentamicin treatment produce different patterns of damage to the efferent innervation of the chick cochlea.

PubMed

Ofsie, M S; Hennig, A K; Messana, E P; Cotanche, D A

1997-11-01

Both sound exposure and gentamicin treatment cause damage to sensory hair cells in the peripheral chick auditory organ, the basilar papilla. This induces a regeneration response which replaces hair cells and restores auditory function. Since functional recovery requires the re-establishment of connections between regenerated hair cells and the central nervous system, we have investigated the effects of sound damage and gentamicin treatment on the neuronal elements within the cochlea. Whole-mount preparations of basilar papillae were labeled with phalloidin to label the actin cytoskeleton and antibodies to neurofilaments, choline acetyltransferase, and synapsin to label neurons; and examined by confocal laser scanning microscopy. When chicks are treated with gentamicin or exposed to acoustic overstimulation, the transverse nerve fibers show no changes from normal cochleae assayed in parallel. Efferent nerve terminals, however, disappear from areas depleted of hair cells following acoustic trauma. In contrast, efferent nerve endings are still present in the areas of hair cell loss following gentamicin treatment, although their morphological appearance is greatly altered. These differences in the response of efferent nerve terminals to sound exposure versus gentamicin treatment may account, at least in part, for the discrepancies reported in the time of recovery of auditory function.

Nucleus accumbens controls wakefulness by a subpopulation of neurons expressing dopamine D1 receptors.

PubMed

Luo, Yan-Jia; Li, Ya-Dong; Wang, Lu; Yang, Su-Rong; Yuan, Xiang-Shan; Wang, Juan; Cherasse, Yoan; Lazarus, Michael; Chen, Jiang-Fan; Qu, Wei-Min; Huang, Zhi-Li

2018-04-20

Nucleus accumbens (NAc) is involved in behaviors that depend on heightened wakefulness, but its impact on arousal remains unclear. Here, we demonstrate that NAc dopamine D 1 receptor (D 1 R)-expressing neurons are essential for behavioral arousal. Using in vivo fiber photometry in mice, we find arousal-dependent increases in population activity of NAc D 1 R neurons. Optogenetic activation of NAc D 1 R neurons induces immediate transitions from non-rapid eye movement sleep to wakefulness, and chemogenetic stimulation prolongs arousal, with decreased food intake. Patch-clamp, tracing, immunohistochemistry, and electron microscopy reveal that NAc D 1 R neurons project to the midbrain and lateral hypothalamus, and might disinhibit midbrain dopamine neurons and lateral hypothalamus orexin neurons. Photoactivation of terminals in the midbrain and lateral hypothalamus is sufficient to induce wakefulness. Silencing of NAc D 1 R neurons suppresses arousal, with increased nest-building behaviors. Collectively, our data indicate that NAc D 1 R neuron circuits are essential for the induction and maintenance of wakefulness.

Corneal nerve regeneration. Correlation between morphology and restoration of sensitivity.

PubMed

de Leeuw, A M; Chan, K Y

1989-09-01

Corneal nerve regeneration was determined in albino rabbits after deepithelialization of the cornea using heptanol. Regeneration was monitored up to 10 weeks by measuring corneal tactile sensitivity using an esthesiometer and by examining stromal and intraepithelial nerve patterns following gold chloride impregnation and acetylcholinesterase staining. Tactile sensitivity was much reduced, possibly absent, up to 2 weeks after wounding. From 2.5-4 weeks, sensitivity recovered rapidly to 60% of prewounding levels and remained unchanged thereafter. In control corneas, a distinct orientation of the basoepithelial leashes towards the nasal-most limbus was observed in the central two-thirds of the cornea. Three days after wounding, neurites that were oriented radially towards the wound center extended into the periphery of the wound area from just beyond the wound margin. At 1 week, regenerating axons were present as single neurites and in the form of modified leashes, mainly at the periphery of the wound area but also more towards the center. At 3 weeks, neurites, regenerated leashes and networks of terminals with terminal endings were found throughout the regenerated epithelium. Regional changes in the orientation of the regenerated leashes were observed also. No further change in the intraepithelial nerve pattern was detectable thereafter up to 10 weeks after wounding. It was concluded that partial restoration of tactile sensitivity following deepithelialization of the cornea is a function of the establishment of a near-normal nerve pattern in the regenerated epithelium and is correlated with the subnormal neural density observed in a previous study.

How the optic nerve allocates space, energy capacity, and information

PubMed Central

Perge, Janos A.; Koch, Kristin; Miller, Robert; Sterling, Peter; Balasubramanian, Vijay

2009-01-01

Fiber tracts should use space and energy efficiently because both resources constrain neural computation. We found for a myelinated tract (optic nerve) that astrocytes use nearly 30% of the space and more than 70% of the mitochondria, establishing the significance of astrocytes for the brain’s space and energy budgets. Axons are mostly thin with a skewed distribution peaking at 0.7µm, near the lower limit set by channel noise. This distribution is matched closely by the distribution of mean firing rates measured under naturalistic conditions, suggesting that firing rate increases proportionally with axon diameter. In axons thicker than 0.7µm mitochondria occupy a constant fraction of axonal volume -- thus, mitochondrial volumes rise as the diameter squared. These results imply a law of diminishing returns: twice the information rate requires more than twice the space and energy capacity. We conclude that the optic nerve conserves space and energy by sending most information at low rates over fine axons with small terminal arbors, and sending some information at higher rates over thicker axons with larger terminal arbors – but only where more bits/s are needed for a specific purpose. Thicker axons seem to be needed, not for their greater conduction velocity (nor other intrinsic electrophysiological purpose), but instead to support larger terminal arbors and more active zones that transfer information synaptically at higher rates. PMID:19535603

High affinity choline uptake (HACU) and choline acetyltransferase (ChAT) activity in neuronal cultures for mechanistic and drug discovery studies

PubMed Central

Ray, Balmiki; Bailey, Jason A.; Simon, Jay R.; Lahiri, Debomoy K.

2012-01-01

Acetylcholine (ACh) is the neurotransmitter used by cholinergic neurons at the neuromuscular junction and in parasympathetic nerve terminals in the periphery, as well as important memory-related circuits in the brain and also takes part in several critical functions. ACh is synthesized from choline and acetyl coenzyme-A by the enzyme choline acetyltransferase (ChAT). The formation of acetylcholine in cholinergic nerve terminals requires both the transport of choline into the cells from the extracellular space, and the activity of ChAT. High affinity choline uptake (HACU) represents the majority of choline uptake into the nerve terminal, and is the acutely regulated, rate-limiting step in ACh synthesis. The HACU component of choline uptake can be differentiated from non-specific choline uptake by inhibition of the choline transporter with hemicholinium. Several methods have been described previously to measure HACU and ChAT simultaneously in synaptosomes, but a well-documented protocol for cultured cells is lacking. We describe a procedure to simultaneously measure HACU and ChAT in cultured cells by simple radionuclide-based techniques. In this procedure we have quantitatively determined HACU and ChAT activity in cholinergically differentiated human neuroblastoma (SK-N-SH) cells. These simple methods can be used for neurochemical and drug discovery studies relevant to several disorders including Alzheimer’s disease, myasthenia gravis, and cardiovascular disease. PMID:22752895

No consistent bioenergetic defects in presynaptic nerve terminals isolated from mouse models of Alzheimer’s disease

PubMed Central

Choi, Sung W.; Gerencser, Akos A.; Ng, Ryan; Flynn, James M.; Melov, Simon; Danielson, Steven R.; Gibson, Bradford W.; Nicholls, David G.; Bredesen, Dale E.; Brand, Martin D.

2012-01-01

Depressed cortical energy supply and impaired synaptic function are predominant associations of Alzheimer’s disease (AD). To test the hypothesis that presynaptic bioenergetic deficits are associated with the progression of AD pathogenesis, we compared bioenergetic variables of cortical and hippocampal presynaptic nerve terminals (synaptosomes) from commonly used mouse models with AD-like phenotypes (J20 age 6 months, Tg2576 age 16 months and APP/PS age 9 and 14 months) to age-matched controls. No consistent bioenergetic deficiencies were detected in synaptosomes from the three models, only APP/PS cortical synaptosomes from 14 month old mice showed an increase in respiration associated with proton leak. J20 mice were chosen for a highly stringent investigation of mitochondrial function and content. There were no significant differences in the quality of the synaptosomal preparations or the mitochondrial volume fraction. Furthermore, respiratory variables, calcium handling, and membrane potentials of synaptosomes from symptomatic J20 mice under calcium-imposed stress were not consistently impaired. The recovery of marker proteins during synaptosome preparation was the same, ruling out the possibility that the lack of functional bioenergetic defects in synaptosomes from J20 mice was due to the selective loss of damaged synaptosomes during sample preparation. Our results support the conclusion that the intrinsic bioenergetic capacities of presynaptic nerve terminals are maintained in these symptomatic AD mouse models. PMID:23175831

Stimuli of Sensory-Motor Nerves Terminate Arterial Contractile Effects of Endothelin-1 by CGRP and Dissociation of ET-1/ETA-Receptor Complexes

PubMed Central

Meens, Merlijn J. P. M. T.; Compeer, Matthijs G.; Hackeng, Tilman M.; van Zandvoort, Marc A.; Janssen, Ben J. A.; De Mey, Jo G. R.

2010-01-01

Background Endothelin-1 (ET-1), a long-acting paracrine mediator, is implicated in cardiovascular diseases but clinical trials with ET-receptor antagonists were not successful in some areas. We tested whether the quasi-irreversible receptor-binding of ET-1 (i) limits reversing effects of the antagonists and (ii) can be selectively dissociated by an endogenous counterbalancing mechanism. Methodology/Principal findings In isolated rat mesenteric resistance arteries, ETA-antagonists, endothelium-derived relaxing factors and synthetic vasodilators transiently reduced contractile effects of ET-1 but did not prevent persistent effects of the peptide. Stimuli of peri-vascular vasodilator sensory-motor nerves such as capsaicin not only reduced but also terminated long-lasting effects of ET-1. This was prevented by CGRP-receptor antagonists and was mimicked by exogenous calcitonin gene-related peptide (CGRP). Using 2-photon laser scanning microscopy in vital intact arteries, capsaicin and CGRP, but not ETA-antagonism, were observed to promote dissociation of pre-existing ET-1/ETA-receptor complexes. Conclusions Irreversible binding and activation of ETA-receptors by ET-1 (i) occur at an antagonist-insensitive site of the receptor and (ii) are selectively terminated by endogenously released CGRP. Hence, natural stimuli of sensory-motor nerves that stimulate release of endogenous CGRP can be considered for therapy of diseases involving ET-1. PMID:20532232

L-Dihydroxyphenylserine (L-DOPS): a norepinephrine prodrug.

PubMed

Goldstein, David S

2006-01-01

L-threo-3,4-dihydroxyphenylserine (L-DOPS, droxydopa) is a synthetic catecholamino acid. When taken orally, L-DOPS is converted to the sympathetic neurotransmitter, norepinephrine (NE), via decarboxylation catalyzed by L-aromatic-amino-acid decarboxylase (LAAAD). Plasma L-DOPS levels peak at about 3 h, followed by a monoexponential decline with a half-time of 2 to 3 h. Plasma levels of NE and of its main neuronal metabolite, dihydroxyphenylglycol (DHPG) peak approximately concurrently but at much lower concentrations. The relatively long half-time for disappearance of L-DOPS from plasma, compared to that of NE, explains their very different attained plasma concentrations. In patients with neurogenic orthostatic hypotension, L-DOPS increases blood pressure and ameliorates orthostatic intolerance. Inhibition of LAAAD, such as by treatment with carbidopa, which does not penetrate the blood-brain barrier, prevents the blood pressure effects of the drug, indicating that L-DOPS increases blood pressure by augmenting NE production outside the brain. Patients with pure autonomic failure (which usually entails loss of sympathetic noradrenergic nerves), and patients with multiple system atrophy (in which noradrenergic innervation remains intact) have similar plasma NE responses to L-DOPS. This suggests mainly non-neuronal production of NE from L-DOPS. L-DOPS is very effective in treatment of deficiency of dopamine-beta-hydroxylase (DBH), the enzyme required for conversion of dopamine to NE in sympathetic nerves. L-DOPS holds promise for treating other much more common conditions involving decreased DBH activity or NE deficiency, such as a variety of syndromes associated with neurogenic orthostatic hypotension.

Ultrastructural and cytochemical evidence for single impulse initiation zones in vestibular macular nerve fibers of rat

NASA Technical Reports Server (NTRS)

Ross, Muriel D.; Chee, Oliver; Black, Samuel; Cutler, Lynn

1991-01-01

Cupric ion-ferricyanide labeling methods and related ferrocyanide-stained tissues were used to locate the characterize, at the ultrastructural level, presumptive impulse initiation zones in the three types of vestibular macular nerve fibers. Large-diameter, M-type vestibular nerve fibers terminate in a calyx at the heminode, and labeling is coextensive with the base of the calyx. Intermediate, M/U-type nerve fibers have short, unmyelinated preterminal segments that sometimes bifurcate intamacularly, and small-diameter, U-type nerve fibers have long, unmyelinated preterminal axons and up to three branches. Preterminals of these nerve fibers display ultrastructural heterogeneity that is correlated with labeling patterns for sodium channels and/or associated polyanionic sites. They have a nodelike ultrastructure and label heavily from near the heminode to the base of the macula. Their intramacular branches, less organized ultrastructurally, label only slightly. Results indicate that vestibular nerve fibers have one impulse initiation zone, located near the heminode, that varies in length according to nerve fiber type. Structural heterogeneity may favor impulse conduction in the central direction, and length of the impulse initiation zone could influence nerve discharge patterns.

Visual neuroscience before the neuron.

PubMed

Wade, Nicholas J

2004-01-01

Visual neuroscience is considered to be a contemporary concern, based in large part on relating characteristics of neural functioning to visual experience. It presupposes a detailed knowledge of neural activity for which the neuron doctrine is a fundamental tenet. However, long before either the neuron doctrine had been advanced or the nerve cell had been described, attempts were made to estimate the dimensions of nerve fibres from measures of visual resolution. In the seventeenth century, the microscopes of Hooke and van Leeuwenhoek were unable to resolve structures as small as nerves adequately. However, it was not Hooke's microscope that led to an estimate of the dimensions of nerve fibres but his experiments on the limits of visual resolution. Hooke determined that a separation of one minute of arc was the minimum that could normally be seen. Descartes had earlier speculated that the retina consisted of the terminations of fibres of the optic nerve, and that their size defined the limits of what could be seen. Estimates of the diameters of nerve fibres were made on the basis of human visual acuity by Porterfield in 1738; he calculated the diameters of nerve fibres in the retina as one 7200th part of an inch (0.0035 mm), based on the resolution of one minute of arc as the minimum visible. In the same year, Jurin questioned the reliability of such estimates because of variations in visual resolution with different stimuli. The measurement of visual acuity was refined by Mayer in 1755, with dots, gratings, and grids used as stimuli. In the 1830s, Treviranus fused the microscopic and acuity approaches to determine the dimensions of nerve fibres. His indirect estimates of the dimensions of retinal fibres were close to those derived from microscopic observation. However, the suggestion that the retina consisted of terminations of nerve fibres influenced his detailed illustrations of its microscopic structure. Contrary to the situation that obtained after the microscopic structure of the retina had been established, a function of vision (acuity) was used to determine the dimensions of the structures (retinal elements) that were thought to mediate it.

Identification of the visceral pain pathway activated by noxious colorectal distension in mice.

PubMed

Kyloh, Melinda; Nicholas, Sarah; Zagorodnyuk, Vladimir P; Brookes, Simon J; Spencer, Nick J

2011-01-01

In patients with irritable bowel syndrome, visceral pain is evoked more readily following distension of the colorectum. However, the identity of extrinsic afferent nerve pathway that detects and transmits visceral pain from the colorectum to the spinal cord is unclear. In this study, we identified which extrinsic nerve pathway(s) underlies nociception from the colorectum to the spinal cord of rodents. Electromyogram recordings were made from the transverse oblique abdominal muscles in anesthetized wild type (C57BL/6) mice and acute noxious intraluminal distension stimuli (100-120 mmHg) were applied to the terminal 15 mm of colorectum to activate visceromotor responses (VMRs). Lesioning the lumbar colonic nerves in vivo had no detectable effect on the VMRs evoked by colorectal distension. Also, lesions applied to the right or left hypogastric nerves failed to reduce VMRs. However, lesions applied to both left and right branches of the rectal nerves abolished VMRs, regardless of whether the lumbar colonic or hypogastric nerves were severed. Electrical stimulation applied to either the lumbar colonic or hypogastric nerves in vivo, failed to elicit a VMR. In contrast, electrical stimulation (2-5 Hz, 0.4 ms, 60 V) applied to the rectum reliably elicited VMRs, which were abolished by selective lesioning of the rectal nerves. DiI retrograde labeling from the colorectum (injection sites 9-15 mm from the anus, measured in unstretched preparations) labeled sensory neurons primarily in dorsal root ganglia (DRG) of the lumbosacral region of the spinal cord (L6-S1). In contrast, injection of DiI into the mid to proximal colon (injection sites 30-75 mm from the anus, measured in unstretched preparations) labeled sensory neurons in DRG primarily of the lower thoracic level (T6-L2) of the spinal cord. The visceral pain pathway activated by acute noxious distension of the terminal 15 mm of mouse colorectum is transmitted predominantly, if not solely, through rectal/pelvic afferent nerve fibers to the spinal cord. The sensory neurons of this spinal afferent pathway lie primarily in the lumbosacral region of the spinal cord, between L6 and S1.

Autologous transplantation with fewer fibers repairs large peripheral nerve defects

PubMed Central

Deng, Jiu-xu; Zhang, Dian-yin; Li, Ming; Weng, Jian; Kou, Yu-hui; Zhang, Pei-xun; Han, Na; Chen, Bo; Yin, Xiao-feng; Jiang, Bao-guo

2017-01-01

Peripheral nerve injury is a serious disease and its repair is challenging. A cable-style autologous graft is the gold standard for repairing long peripheral nerve defects; however, ensuring that the minimum number of transplanted nerve attains maximum therapeutic effect remains poorly understood. In this study, a rat model of common peroneal nerve defect was established by resecting a 10-mm long right common peroneal nerve. Rats receiving transplantation of the common peroneal nerve in situ were designated as the in situ graft group. Ipsilateral sural nerves (10–30 mm long) were resected to establish the one sural nerve graft group, two sural nerves cable-style nerve graft group and three sural nerves cable-style nerve graft group. Each bundle of the peroneal nerve was 10 mm long. To reduce the barrier effect due to invasion by surrounding tissue and connective-tissue overgrowth between neural stumps, small gap sleeve suture was used in both proximal and distal terminals to allow repair of the injured common peroneal nerve. At three months postoperatively, recovery of nerve function and morphology was observed using osmium tetroxide staining and functional detection. The results showed that the number of regenerated nerve fibers, common peroneal nerve function index, motor nerve conduction velocity, recovery of myodynamia, and wet weight ratios of tibialis anterior muscle were not significantly different among the one sural nerve graft group, two sural nerves cable-style nerve graft group, and three sural nerves cable-style nerve graft group. These data suggest that the repair effect achieved using one sural nerve graft with a lower number of nerve fibers is the same as that achieved using the two sural nerves cable-style nerve graft and three sural nerves cable-style nerve graft. This indicates that according to the ‘multiple amplification’ phenomenon, one small nerve graft can provide a good therapeutic effect for a large peripheral nerve defect. PMID:29323049

Alterations in Corneal Sensory Nerves During Homeostasis, Aging, and After Injury in Mice Lacking the Heparan Sulfate Proteoglycan Syndecan-1.

PubMed

Pal-Ghosh, Sonali; Tadvalkar, Gauri; Stepp, Mary Ann

2017-10-01

To determine the impact of the loss of syndecan 1 (SDC1) on intraepithelial corneal nerves (ICNs) during homeostasis, aging, and in response to 1.5-mm trephine and debridement injury. Whole-mount corneas are used to quantify ICN density and thickness over time after birth and in response to injury in SDC1-null and wild-type (WT) mice. High-resolution three-dimensional imaging is used to visualize intraepithelial nerve terminals (INTs), axon fragments, and lysosomes in corneal epithelial cells using antibodies against growth associated protein 43 (GAP43), βIII tubulin, and LAMP1. Quantitative PCR was performed to quantify expression of SDC1, SDC2, SDC3, and SDC4 in corneal epithelial mRNA. Phagocytosis was assessed by quantifying internalization of fluorescently labeled 1-μm latex beads. Intraepithelial corneal nerves innervate the corneas of SDC1-null mice more slowly. At 8 weeks, ICN density is less but thickness is greater. Apically projecting intraepithelial nerve terminals and lysosome-associated membrane glycoprotein 1 (LAMP1) are also reduced in unwounded SDC1-null corneas. Quantitative PCR and immunofluorescence studies show that SDC3 expression and localization are increased in SDC1-null ICNs. Wild-type and SDC1-null corneas lose ICN density and thickness as they age. Recovery of axon density and thickness after trephine but not debridement wounds is slower in SDC1-null corneas compared with WT. Experiments assessing phagocytosis show reduced bead internalization by SDC1-null epithelial cells. Syndecan-1 deficiency alters ICN morphology and homeostasis during aging, reduces epithelial phagocytosis, and impairs reinnervation after trephine but not debridement injury. These data provide insight into the mechanisms used by sensory nerves to reinnervate after injury.

Posterior Orbitofrontal and Anterior Cingulate Pathways to the Amygdala Target Inhibitory and Excitatory Systems with Opposite Functions.

PubMed

Zikopoulos, Basilis; Höistad, Malin; John, Yohan; Barbas, Helen

2017-05-17

The bidirectional dialogue of the primate posterior orbitofrontal cortex (pOFC) with the amygdala is essential in cognitive-emotional functions. The pOFC also sends a uniquely one-way excitatory pathway to the amygdalar inhibitory intercalated masses (IM), which inhibit the medial part of the central amygdalar nucleus (CeM). Inhibition of IM has the opposite effect, allowing amygdalar activation of autonomic structures and emotional arousal. Using multiple labeling approaches to identify pathways and their postsynaptic sites in the amygdala in rhesus monkeys, we found that the anterior cingulate cortex innervated mostly the basolateral and CeM amygdalar nuclei, poised to activate CeM for autonomic arousal. By contrast, a pathway from pOFC to IM exceeded all other pathways to the amygdala by density and size and proportion of large and efficient terminals. Moreover, whereas pOFC terminals in IM innervated each of the three distinct classes of inhibitory neurons, most targeted neurons expressing dopamine- and cAMP-regulated phosphoprotein (DARPP-32+), known to be modulated by dopamine. The predominant pOFC innervation of DARPP-32+ neurons suggests activation of IM and inhibition of CeM, resulting in modulated autonomic function. By contrast, inhibition of DARPP-32 neurons in IM by high dopamine levels disinhibits CeM and triggers autonomic arousal. The findings provide a mechanism to help explain how a strong pOFC pathway, which is poised to moderate activity of CeM, through IM, can be undermined by the high level of dopamine during stress, resulting in collapse of potent inhibitory mechanisms in the amygdala and heightened autonomic drive, as seen in chronic anxiety disorders. SIGNIFICANCE STATEMENT The dialogue between prefrontal cortex and amygdala allows thoughts and emotions to influence actions. The posterior orbitofrontal cortex sends a powerful pathway that targets a special class of amygdalar intercalated mass (IM) inhibitory neurons, whose wiring may help modulate autonomic function. By contrast, the anterior cingulate cortex innervates other amygdalar parts, activating circuits to help avoid danger. Most IM neurons in primates label for the protein DARPP-32, known to be activated or inhibited based on the level of dopamine. Stress markedly increases dopamine release and inhibits IM neurons, compromises prefrontal control of the amygdala, and sets off a general alarm system as seen in affective disorders, such as chronic anxiety and post-traumatic stress disorder. Copyright © 2017 the authors 0270-6474/17/375051-14$15.00/0.

Perinatal thiamine deficiency-induced spontaneous abortion and pup-killing responses in rat dams.

PubMed

Bâ, Abdoulaye

2013-03-01

The current study attempts to determine whether thiamine (B1 vitamin) deficiency and chronic alcohol-related thiamine-deficient (TD) status, disturb maternal behavior towards pups. During gestation and lactation, Wistar rat dams were exposed to the following treatments: (i) prenatal TD dams; (ii) perinatal TD dams; (iii) postnatal TD dams; (iv) 12% alcohol/water drinking mothers; (v) ad libitum control dams. Pair-feeding treatments controlled malnutrition related to thiamine deficiency; (vi) prenatal pair-fed (PF) dams; (vii) perinatal PF dams; (viii) postnatal PF dams and included also the control of alcohol consummation: (ix) PF saccharose dams. Dams were observed for gestation outcome and for apparent disorders of the maternal behavior related to the pups at parturition. From the nine experimental groups studied, only pre- and perinatal TD dams exhibited spontaneous abortion (33.36 and 41.66%, respectively) followed by pups-killing responses where, respectively, 4 dams/7 (57.14%) and 5 dams/7 (71.43%) showed disruption of maternal behavior and appearance of cannibalism towards pups which all were killed within 48 hours after parturition. Spontaneous abortion and pup-killing responses were not observed in the dams of any other experimental group, suggesting that perinatal disturbances of hormonal factors underlay these maternal disorders. Previous studies reported that thiamine deficiency-induced degeneration of dopamine neurons may be related to mouse-killing aggression in rats. The present study suggests that perinatal thiamine deficiency-induced alteration of dopaminergic neurons in maternal brain could be a trigger factor of pup-killing responses. Central dopamine and oxytocin have been strongly associated with both the onset and maintenance of maternal behavior and the regulation of maternal aggressiveness as well. Our studies suggest that estrogen control oxytocin levels in brain structures of pregnancy-terminated rats via dopamine transmission. Thiamine may modulate cAMP/Ca2+ -dependent estradiol-triggered responses which in turn control dopamine synthesis. Consequently, thiamine deficiency induced perinatally triggers pup-killing responses in pregnancy-terminated rats by the following toxic effects: (i) disturbances of estrogen production and/or release affecting dopamine synthesis; (ii) alterations of dopamine inhibition on central oxytocinergic system-related maternal aggressiveness. Likewise, our results indicate also that perinatal thiamine deficiency alone induces spontaneous abortion, reduces litter size, and lowers birth weight, which together suggest changing in the fetoplacental estrogen receptor alpha/progesterone receptor A ratio during gestation, via autocrine/paracrine regulation disturbances. Those hypotheses should be confirmed by further investigations.

Identification of a negative regulatory region for the exchange activity and characterization of T332I mutant of Rho guanine nucleotide exchange factor 10 (ARHGEF10).

PubMed

Chaya, Taro; Shibata, Satoshi; Tokuhara, Yasunori; Yamaguchi, Wataru; Matsumoto, Hiroshi; Kawahara, Ichiro; Kogo, Mikihiko; Ohoka, Yoshiharu; Inagaki, Shinobu

2011-08-26

The T332I mutation in Rho guanine nucleotide exchange factor 10 (ARHGEF10) was previously found in persons with slowed nerve conduction velocities and thin myelination of peripheral nerves. However, the molecular and cellular basis of the T332I mutant is not understood. Here, we show that ARHGEF10 has a negative regulatory region in the N terminus, in which residue 332 is located, and the T332I mutant is constitutively active. An N-terminal truncated ARHGEF10 mutant, ARHGEF10 ΔN (lacking amino acids 1-332), induced cell contraction that was inhibited by a Rho kinase inhibitor Y27632 and had higher GEF activity for RhoA than the wild type. The T332I mutant also showed the phenotype similar to the N-terminal truncated mutant. These data suggest that the ARHGEF10 T332I mutation-associated phenotype observed in the peripheral nerves is due to activated GEF activity of the ARHGEF10 T332I mutant.

Identification of a Negative Regulatory Region for the Exchange Activity and Characterization of T332I Mutant of Rho Guanine Nucleotide Exchange Factor 10 (ARHGEF10)*

PubMed Central

Chaya, Taro; Shibata, Satoshi; Tokuhara, Yasunori; Yamaguchi, Wataru; Matsumoto, Hiroshi; Kawahara, Ichiro; Kogo, Mikihiko; Ohoka, Yoshiharu; Inagaki, Shinobu

2011-01-01

The T332I mutation in Rho guanine nucleotide exchange factor 10 (ARHGEF10) was previously found in persons with slowed nerve conduction velocities and thin myelination of peripheral nerves. However, the molecular and cellular basis of the T332I mutant is not understood. Here, we show that ARHGEF10 has a negative regulatory region in the N terminus, in which residue 332 is located, and the T332I mutant is constitutively active. An N-terminal truncated ARHGEF10 mutant, ARHGEF10 ΔN (lacking amino acids 1–332), induced cell contraction that was inhibited by a Rho kinase inhibitor Y27632 and had higher GEF activity for RhoA than the wild type. The T332I mutant also showed the phenotype similar to the N-terminal truncated mutant. These data suggest that the ARHGEF10 T332I mutation-associated phenotype observed in the peripheral nerves is due to activated GEF activity of the ARHGEF10 T332I mutant. PMID:21719701

Innervation pattern of polycystic ovaries in the women.

PubMed

Wojtkiewicz, Joanna; Jana, Barbara; Kozłowska, Anna; Crayton, Robert; Majewski, Mariusz; Zalecki, Michał; Baranowski, Włodzimierz; Radziszewski, Piotr

2014-11-01

The aim of the present study was to determine the changes in both the distribution pattern and density of nerve fibers containing dopamine β-hydroxylase (DβH), vesicular acetylcholine transporter (VAChT), neuronal nitric oxide synthase (nNOS), substance P (SP), calcitonin gene related peptide (CGRP), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), somatostatin (SOM), galanin (GAL) and pituitary adenylate cyclase-activating polypeptide (PACAP) in the human polycystic ovaries. In the polycystic ovaries, when compared to the immunoreactions pattern observed in the control gonads, following changes were revealed: (1) an increase in the number of DβH-, VAChT-, VIP- or GAL-immunoreactive (IR) nerve fibers within the stroma as well as in the number of DβH-IR fibers near primordial follicles and medullar veins and venules; (2) a reduction in the number of nerve fibers containing nNOS, CGRP, SOM, PACAP within the stroma and in the numbers of CGRP-IR fibers around arteries; (3) an appearance of SP- and GAL-IR fibers around medullar and cortical arteries, arterioles, veins and venules, with except of GAL-IR fibers supplying medullar veins; and (4) the lack of nNOS-IR nerve fibers near primordial follicles and VIP-IR nerves around medullar arteries and arterioles. In conclusion, our results suggest that the changes in the innervation pattern of the polycystic ovaries in human may play an important role in the pathogenesis and/or course of this disorder. Copyright © 2014. Published by Elsevier B.V.

Iometopane: (123)I beta-CIT, dopascan injection, GPI 200, RTI 55.

PubMed

2003-01-01

Iometopane [(123)I beta-CIT, GPI 200, RTI 55], a tropane derivative labelled with iodine-123, is a dopamine imaging agent that was under development with Guilford Pharmaceuticals (as Dopascan Injection) for the early diagnosis of Parkinson's disease. Neurochemical imaging with iometopane using conventional single photon emission computerised tomography (SPECT) provided images of the brain for the distinguished diagnosis of Parkinson's disease. The ability of iometopane to bind to the dopamine transporter on presynaptic dopaminergic nerve terminal in the striatum (caudate nucleus and putamen) has been used to differentiate the uptake of the agent by the neurons in the striatum in patients with a Parkinsonian disorder (Parkinson's disease and progressive supranuclear palsy) from patients without a Parkinsonian disorder (essential tremor and healthy controls) with high sensitivity and specificity. The diminished uptake of iometopane in the striatum on the SPECT images of patients with a Parkinsonian disorder can be applied to assess both disease trait and disease state (severity) reflected by the severity of the brain dopamine neuron loss. The rate of clinical progression of Parkinson's disease varies greatly and is currently unpredictable. Imaging with iometopane provides the opportunity to evaluate patients longitudinally from early to late disease using an objective biomarker for dopamine nerve cell degeneration. Diagnostic imaging with Dopascan Injection is thought to differentiate Parkinson's disease from other forms of tremor, eliminate tests such as MRI and CT scans, unnecessary and inappropriate medications (psychotropics), and significantly reduce the number of people remaining on Parkinson's disease medications for life, despite not having Parkinson's disease. Guilford Pharmaceuticals acquired the licence for iometopane from the Research Triangle Institute, US, and sub-licensed it to Daiichi Radioisotope Laboratories for marketing, sales and distribution in Japan, Korea and Taiwan. In July 2003, Daiichi Radioisotope Laboratories paid a milestone payment of $0.55 million to Guilford after filing an application for approval in Japan. In January 2002, Guilford signed an exclusive European development, marketing and sales and distribution agreement for iometopane with MAP Medical Technologies of Finland. Under the terms of the agreement, MAP Medical Technologies will assume responsibility for regulatory approvals, manufacturing, marketing and selling the agent in all member states of the EU and other selected markets. In return, Guilford will receive an upfront payment, milestone payments and royalties on future sales in these territories. In July 2002, MAP Medical Technologies become a subsidiary of Schering AG. In March 2002, Guilford Pharmaceuticals sublicensed iometopane to Molecular Neuroimaging LLC (MNI) of Connecticut, USA. Under the terms of the agreement, MNI will pay a royalty for each administration of iometopane, and also provide Guilford Pharmaceuticals with favourable pricing for the services (including administration of iometopane) for any clinical trials of Guilford's product candidates. This agreement will be terminated upon the US FDA's approval of the product candidate for marketing and sale in the US. Guilford has retained commercial rights to Dopascan Injection in the US. MAP Medical Technologies (Schering AG) submitted a Marketing Authorisation Application (MAA) in Finland for European approval of iometopane for the diagnosis of Parkinson's disease in April 2002. Daiichi Radioisotope Laboratories filed an application for approval of iometopane (Dopascan Injection) for the diagnosis of Parkinson's disease in Japan in July 2003. Guilford Pharmaceuticals is conducting a phase II clinical trial in 200 patients with Parkinson's disease where iometopane imaging is used to assess the effectiveness of GPI 1485, an investigational drug candidate, at baseline and at one year and two years after treatment with either GPI 1485 or placebo. The enrolment is expected to be completed in Q3 of 2003. Guint with either GPI 1485 or placebo. The enrolment is expected to be completed in Q3 of 2003. Guilford Pharmaceuticals decided not to proceed with phase III clinical trials and further development of iometopane due to its inability to contract a suitable manufacturer for the clinical and commercial supply of iometopane on acceptable conditions in the US. Guilford Pharmaceuticals obtained the patent coverage for iometopane in the US, Australia and Europe (Austria, Belgium, Switzerland, Liechtenstein, Germany, Denmark, Spain, France, the United Kingdom, Italy, Luxembourg, the Netherlands, Sweden and Greece). Separate filings were made in Finland, Norway, Japan, Canada and Korea. The manufacturing methods of Dopascan are protected by patents in the US and Europe. Dopascan is a registered trademark in the US, Canada, Europe and Asia.

Neuropathy in non-freezing cold injury (trench foot).

PubMed Central

Irwin, M S; Sanders, R; Green, C J; Terenghi, G

1997-01-01

Non-freezing cold injury (trench foot) is characterized, in severe cases, by peripheral nerve damage and tissue necrosis. Controversy exists regarding the susceptibility of nerve fibre populations to injury as well as the mechanism of injury. Clinical and histological studies (n = 2) were conducted in a 40-year-old man with severe non-freezing cold injury in both feet. Clinical sensory tests, including two-point discrimination and pressure, vibration and thermal thresholds, indicated damage to large and small diameter nerves. On immunohistochemical assessment, terminal cutaneous nerve fibres within the plantar skin stained much less than in a normal control whereas staining to von Willebrand factor pointed to increased vascularity in all areas. The results indicate that all nerve populations (myelinated and unmyelinated) were damaged, possibly in a cycle of ischaemia and reperfusion. Images Figure 1 a Figure 1 b Figure 2 a Figure 2 b Figure 3 a Figure 3 b PMID:9306996

Conductance changes associated with the secretory potential in the cockroach salivary gland.

PubMed

Ginsborg, B L; House, C R; Silinsky, E M

1974-02-01

1. Conductance changes in the acini of the cockroach salivary gland have been examined during nerve stimulation by means of two intracellular electrodes placed in the same acinus, the first electrode being used for recording membrane potential and the second for current injection.2. The transient hyperpolarization (secretory potential) in the acinus evoked by nerve stimuli is accompanied by a rise in membrane conductance. The conductance, however, remains high for a longer period than that of the response.3. Applying the analysis of Trautwein & Dudel (1958) to the secretory potentials recorded in the acinus (assumed to behave electrically like a single cell) gives estimates of the ;transmitter equilibrium potential'. The values indicate that the neurotransmitter increases the membrane potassium conductance.4. The hyperpolarization of the acinus evoked by 10(-6)M dopamine in the bathing fluid is also associated with an increase in membrane potassium conductance.

The blocking action of choline 2:6-xylyl ether bromide on adrenergic nerves

PubMed Central

Exley, K. A.

1957-01-01

Choline 2:6-xylyl ether bromide (TM 10), given systemically to cats in doses of 5 to 15 mg./kg., abolishes the effects of adrenergic nerve stimulation whilst leaving the reactions of the effector organs to adrenaline unimpaired. The effects of a single dose may take up to one hour to become fully established and last for more than twenty-four hours. Apart from transitory ganglionic blockade, cholinergic autonomic nerves are unaffected even by large doses of TM 10. Doses of TM 10 which produce effective blockade do not impair conduction along adrenergic nerve trunks; the drug must, therefore, act at, or close to, the nerve terminals. TM 10 prevents the output of noradrenaline from the spleen on stimulating the splenic nerves; but, in acute experiments, it does not influence the liberation of pressor amines from the stimulated suprarenals. Examination of some ethers related to TM 10 revealed no correlation between TM 10-like adrenergic blocking activity and local anaesthetic activity. The action of TM 10 on adrenergic nerves does not, therefore, seem to be accounted for by axonal block. ImagesFIG. 8 PMID:13460234

Active uptake system for substance P carboxy-terminal heptapeptide (5-11) into a fraction from rabbit enriched in glial cells.

PubMed

Inoue, A; Nakata, Y; Yajima, H; Segawa, T

1984-10-01

In the present study, we demonstrated the existence of an active uptake system for substance P carboxy-terminal heptapeptide, (5-11)SP. When a fraction from rabbit brain enriched in glial cells was incubated with [3H] (5-11)SP, an uptake of [3H](5-11)SP was observed. The uptake system has the properties of an active transport mechanism. Kinetic analysis indicated two components of [3H](5-11)SP uptake, one representing a high and the other a low affinity transport system. After unilateral ablation of the striatum, approximately 30% of the high affinity [3H](5-11)SP uptake capacity of substantia nigra slices disappeared. The subcellular distribution of the high affinity uptake indicated that [3H] 5-hydroxytryptamine was taken up mostly into the P2B fraction (synaptosomal fraction), whereas [3H](5-11)SP was taken up into the P2A fraction (myelin fraction) to the same extent as into the P2B fraction. These results suggest that when SP is released from nerve terminals, it is hydrolysed into (5-11)SP, which is in turn accumulated into glial cells as well as nerve terminals and that this high affinity uptake mechanism may play an important role in terminating the synaptic action of SP.

Mutual enhancement of central neurotoxicity induced by ketamine followed by methamphetamine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ke, J.-J.; Chen, H.-I.; Jen, C.J.

2008-03-01

We hereby report that repeated administration of ketamine (350 mg/kg in total) and methamphetamine (30 mg/kg in total) causes specific glutamatergic and dopaminergic neuron deficits, respectively, in adult mouse brain. Acute ketamine did not affect basal body temperature or the later methamphetamine-induced hyperthermia. However, pretreatment with repeated doses of ketamine aggravated methamphetamine-induced dopaminergic terminal loss as evidenced by a drastic decrease in the levels of dopamine, 3,4-dihydroxyphenylacetic acid, and dopamine transporter density as well as poor gait balance performance. In contrast, methamphetamine-induced serotonergic depletion was not altered by ketamine pretreatment. Likewise, the subsequent treatment with methamphetamine exacerbated the ketamine-induced glutamatergicmore » damage as indicated by reduced levels of the vesicular glutamate transporter in hippocampus and striatum and poor memory performance in the Morris water maze. Finally, since activation of the D1 and AMPA/kainate receptors has been known to be involved in the release of glutamate and dopamine, we examined the effects of co-administration of SCH23390, a D1 antagonist, and CNQX, an AMPA/kainate antagonist. Intraventricular CNQX infusion abolished ketamine's potentiation of methamphetamine-induced dopamine neurotoxicity, while systemic SCH23390 mitigated methamphetamine's potentiation of ketamine-induced glutamatergic toxicity. We conclude that repeated doses of ketamine potentiate methamphetamine-induced dopamine neurotoxicity via AMPA/kainate activation and that conjunctive use of methamphetamine aggravates ketamine-induced glutamatergic neurotoxicity possibly via D1 receptor activation.« less

Development of peptide-containing nerves in the human fetal prostate gland.

PubMed Central

Jen, P Y; Dixon, J S

1995-01-01

Immunohistochemical methods were used to study the developing peptidergic innervation of the human fetal prostate gland in a series of specimens ranging in gestational age from 13 to 30 wk. The overall innervation of each specimen was visualised using protein gene product 9.5 (PGP), a general nerve marker. The onset and development of specific neuropeptide-containing subpopulations were investigated using antisera to neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP), bombesin (BOM), somatostatin (SOM), leu-enkephalin (l-ENK) and met-enkephalin (m-ENK). In addition the occurrence and distribution of presumptive noradrenergic nerves was studied using antisera to dopamine-beta-hydroxylase (D beta H) and tyrosine hydroxylase (TH). At 13 wk numerous branching PGP-immunoreactive (-IR) nerves were observed in the capsule of the developing prostate gland and surrounding the preprostatic urethra but the remainder of the gland was devoid of nerves. The majority of nerves in the capsule contained D beta H and TH and were presumed to be noradrenergic in type while other nerves (in decreasing numbers) contained NPY, l-ENK, SP and CGRP. Nerves associated with the preprostatic urethra did not contain any of the neuropeptides under investigation. At 17 wk the density of nerves in the capsule had increased and occasional m-ENK-, VIP- and BOM-IR nerve fibres were also observed. In addition PGP, D beta H-, TH-, NPY- and l-ENK-IR nerves occurred in association with smooth muscle bundles which at 17 wk were present in the outer part of the gland. Occasional PGP-IR nerves were also present at the base of the epithelium forming some of the prostatic glands. At 23 wk some of the subepithelial nerves showed immunoreactivity for NPY, VIP or l-ENK. At 26 wk smooth muscle bundles occurred throughout the gland and were richly innervated by PGP, D beta H and TH-IR nerves while a less dense plexus was formed by NPY- and l-ENK-IR nerves together with a few m-ENK-IR nerves. Occasional smooth muscle-associated varicose nerve fibres showed immunoreactivity for SP, CGRP, VIP or BOM although the majority of these types of nerve formed perivascular plexuses. Also at 26 wk numerous varicose nerve fibres were observed in association with the prostatic acini, the majority of such nerves containing NPY with a few showing immunoreactivity to VIP, l-ENK, SP or CGRP.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 PMID:7591978

Supercharged end-to-side anterior interosseous to ulnar motor nerve transfer for intrinsic musculature reinnervation.

PubMed

Barbour, John; Yee, Andrew; Kahn, Lorna C; Mackinnon, Susan E

2012-10-01

Functional motor recovery after peripheral nerve injury is predominantly determined by the time to motor end plate reinnervation and the absolute number of regenerated motor axons that reach target. Experimental models have shown that axonal regeneration occurs across a supercharged end-to-side (SETS) nerve coaptation. In patients with a recovering proximal ulnar nerve injury, a SETS nerve transfer conceptually is useful to protect and preserve distal motor end plates until the native axons fully regenerate. In addition, for nerve injuries in which incomplete regeneration is anticipated, a SETS nerve transfer may be useful to augment the regenerating nerve with additional axons and to more quickly reinnervate target muscle. We describe our technique for a SETS nerve transfer of the terminal anterior interosseous nerve (AIN) to the pronator quadratus muscle (PQ) end-to-side to the deep motor fascicle of the ulnar nerve in the distal forearm. In addition, we describe our postoperative therapy regimen for these transfers and an evaluation tool for monitoring progressive muscle reinnervation. Although the AIN-to-ulnar motor group SETS nerve transfer was specifically designed for ulnar nerve injuries, we believe that the SETS procedure might have broad clinical utility for second- and third-degree axonotmetic nerve injuries, to augment partial recovery and/or "babysit" motor end plates until the native parent axons regenerate to target. We would consider all donor nerves currently utilized in end-to-end nerve transfers for neurotmetic injuries as candidates for this SETS technique. Copyright © 2012 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

The sensory-motor bridge neurorraphy: an anatomic study of feasibility between sensory branch of the musculocutaneous nerve and deep branch of the radial nerve.

PubMed

Goubier, Jean-Noel; Teboul, Frédéric

2011-05-01

Restoring elbow flexion remains the first step in the management of total palsy of the brachial plexus. Non avulsed upper roots may be grafted on the musculocutaneous nerve. When this nerve is entirely grafted, some motor fibres regenerate within the sensory fibres quota. Aiming potential utilization of these lost motor fibres, we attempted suturing the sensory branch of the musculocutaneous nerve onto the deep branch of the radial nerve. The objective of our study was to assess the anatomic feasibility of such direct suturing of the terminal sensory branch of the musculocutaneous nerve onto the deep branch of the radial nerve. The study was carried out with 10 upper limbs from fresh cadavers. The sensory branch of the musculocutaneous muscle was dissected right to its division. The motor branch of the radial nerve was identified and dissected as proximally as possible into the radial nerve. Then, the distance separating the two nerves was measured so as to assess whether direct neurorraphy of the two branches was feasible. The excessive distance between the two branches averaged 6 mm (1-13 mm). Thus, direct neurorraphy of the sensory branch of the musculocutaneous nerve and the deep branch of the radial nerve was possible. When the whole musculocutaneous nerve is grafted, some of its motor fibres are lost amongst the sensory fibres (cutaneous lateral antebrachial nerve). By suturing this sensory branch onto the deep branch of the radial nerve, "lost" fibres may be retrieved, resulting in restoration of digital extension. Copyright © 2011 Wiley-Liss, Inc.

Role of nitric oxide in methamphetamine neurotoxicity: protection by 7-nitroindazole, an inhibitor of neuronal nitric oxide synthase.

PubMed

Di Monte, D A; Royland, J E; Jakowec, M W; Langston, J W

1996-12-01

The role of nitric oxide (NO.) in the neurotoxic effects of methamphetamine (METH) was evaluated using 7-nitroindazole (7-NI), a potent inhibitor of neuronal nitric oxide synthase. Treatment of mice with 7-NI (50 mg/kg) almost completely counteracted the loss of dopamine, 3,4-dihydroxyphenylacetic acid, and tyrosine hydroxylase immunoreactivity observed 5 days after four injections of 10 or 7.5 mg/kg METH. With the higher dose of METH, this protection at 5 days occurred despite the fact that combined administration of METH and 7-NI significantly increased lethality and exacerbated METH-induced dopamine release (as indicated by a greater dopamine depletion at 90 min and 1 day). Combined treatment with 4 x 10 mg/kg METH and 7-NI also slightly increased the body temperature of mice as compared with METH alone. Thus, the neuroprotective effects of 7-NI are independent from lethality, are not likely to be related to a reduction of METH-induced dopamine release, and are not due to a decrease in body temperature. These results indicate that NO. formation is an important step leading to METH neurotoxicity, and suggest that the cytotoxic properties of NO. may be directly involved in dopaminergic terminal damage.

In-vivo staging of pathology in REM sleep behaviour disorder: a multimodality imaging case-control study.

PubMed

Knudsen, Karoline; Fedorova, Tatyana D; Hansen, Allan K; Sommerauer, Michael; Otto, Marit; Svendsen, Kristina B; Nahimi, Adjmal; Stokholm, Morten G; Pavese, Nicola; Beier, Christoph P; Brooks, David J; Borghammer, Per

2018-06-01

Accumulating evidence suggests that α-synuclein aggregates-a defining pathology of Parkinson's disease-display cell-to-cell transmission. α-synuclein aggregation is hypothesised to start in autonomic nerve terminals years before the appearance of motor symptoms, and subsequently spread via autonomic nerves to the spinal cord and brainstem. To assess this hypothesis, we investigated sympathetic, parasympathetic, noradrenergic, and dopaminergic innervation in patients with idiopathic rapid eye movement (REM) sleep behaviour disorder, a prodromal phenotype of Parkinson's disease. In this prospective, case-control study, we recruited patients with idiopathic REM sleep behaviour disorder, confirmed by polysomnography, without clinical signs of parkinsonism or dementia, via advertisement and through sleep clinics in Denmark. We used 11 C-donepezil PET and CT to assess cholinergic (parasympathetic) gut innervation, 123 I-metaiodobenzylguanidine (MIBG) scintigraphy to measure cardiac sympathetic innervation, neuromelanin-sensitive MRI to measure integrity of pigmented neurons of the locus coeruleus, 11 C-methylreboxetine (MeNER) PET to assess noradrenergic nerve terminals originating in the locus coeruleus, and 18 F-dihydroxyphenylalanine (DOPA) PET to assess nigrostriatal dopamine storage capacity. For each imaging modality, we compared patients with idiopathic REM sleep behaviour disorder with previously published reference data of controls without neurological disorders or cognitive impairment and with symptomatic patients with Parkinson's disease. We assessed imaging data using one-way ANOVA corrected for multiple comparisons. Between June 3, 2016, and Dec 19, 2017, we recruited 22 consecutive patients with idiopathic REM sleep behaviour disorder to the study. Compared with controls, patients with idiopathic REM sleep behaviour disorder had decreased colonic 11 C-donepezil uptake (-0·322, 95% CI -0·112 to -0·531; p=0·0020), 123 I-MIBG heart:mediastinum ratio (-0·508, -0·353 to -0·664; p<0·0001), neuromelanin-sensitive MRI locus coeruleus:pons ratio (-0·059, -0·019 to -0·099; p=0·0028), and putaminal 18 F-DOPA uptake (Ki; -0·0023, -0·0009 to -0·0037; p=0·0013). No between-group differences were detected between idiopathic REM sleep behaviour disorder and Parkinson's disease groups with respect to 11 C-donepezil (p=0·39), 123 I-MIBG (p>0·99), neuromelanin-sensitive MRI (p=0·96), and 11 C-MeNER (p=0·56). By contrast, 15 (71%) of 21 patients with idiopathic REM sleep behaviour disorder had 18 F-DOPA Ki values within normal limits, whereas all patients with Parkinson's disease had significantly decreased 18 F-DOPA Ki values when compared with patients with idiopathic REM sleep behaviour disorder (p<0·0001). Patients with idiopathic REM sleep behaviour disorder had fully developed pathology in the peripheral autonomic nervous system and the locus coeruleus, equal to that in diagnosed Parkinson's disease. These patients also showed noradrenergic thalamic denervation, but most had normal putaminal dopaminergic storage capacity. This caudorostral gradient of dysfunction supports the hypothesis that α-synuclein pathology in Parkinson's disease initially targets peripheral autonomic nerves and then spreads rostrally to the brainstem. Lundbeck Foundation, Jascha Foundation, and the Swiss National Foundation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Neurotensin enhances glutamatergic EPSCs in VTA neurons by acting on different neurotensin receptors.

PubMed

Bose, Poulomee; Rompré, Pierre-Paul; Warren, Richard A

2015-11-01

Neurotensin (NT) is an endogenous neuropeptide that modulates dopamine and glutamate neurotransmission in several limbic regions innervated by neurons located in the ventral tegmental area (VTA). While several studies showed that NT exerted a direct modulation on VTA dopamine neurons less is known about its role in the modulation of glutamatergic neurotransmission in this region. The present study was aimed at characterising the effects of NT on glutamate-mediated responses in different populations of VTA neurons. Using whole cell patch clamp recording technique in horizontal rat brain slices, we measured the amplitude of glutamatergic excitatory post-synaptic currents (EPSCs) evoked by electrical stimulation of VTA afferents before and after application of different concentrations of NT1-13 or its C-terminal fragment, NT8-13. Neurons were classified as either Ih(+) or Ih(-) based on the presence or absence of a hyperpolarisation activated cationic current (Ih). We found that NT1-13 and NT8-13 produced comparable concentration dependent increase in the amplitude of EPSCs in both Ih(+) and Ih(-) neurons. In Ih(+) neurons, the enhancement effect of NT8-13 was blocked by both antagonists, while in Ih(-) neurons it was blocked by the NTS1/NTS2 antagonist, SR142948A, but not the preferred NTS1 antagonist, SR48692. In as much as Ih(-) neurons are non-dopaminergic neurons and Ih(+) neurons represent both dopamine and non-dopamine neurons, we can conclude that NT enhances glutamatergic mediated responses in dopamine, and in a subset of non-dopamine, neurons by acting respectively on NTS1 and an NT receptor other than NTS1. Copyright © 2015 Elsevier Inc. All rights reserved.

[Professor Morii and my academic life].

PubMed

Nishizawa, Yoshiki

2011-12-01

Emeritus Professor Hirotoshi Morii was an important mentor in my academic life, who was a chief editor of CLINICAL CALCIUM with Professor Yoshio Yazaki for a long time. In the study of dopamine-β-hydroxylase, hyperthyroidism was able to prove hypotonic status for sympathetic nerve system by his valuable suggestion, though this condition was believed to be hypersympathetic till 1974 when my paper was published in Journal of Clinical Endocrinology and Metabolism. His suggestion struck me at that time. And this experience continues to give me an active power through my academic life.

Neuronal Calcium Sensor-1 Binds the D2 Dopamine Receptor and G-protein-coupled Receptor Kinase 1 (GRK1) Peptides Using Different Modes of Interactions.

PubMed

Pandalaneni, Sravan; Karuppiah, Vijaykumar; Saleem, Muhammad; Haynes, Lee P; Burgoyne, Robert D; Mayans, Olga; Derrick, Jeremy P; Lian, Lu-Yun

2015-07-24

Neuronal calcium sensor-1 (NCS-1) is the primordial member of the neuronal calcium sensor family of EF-hand Ca(2+)-binding proteins. It interacts with both the G-protein-coupled receptor (GPCR) dopamine D2 receptor (D2R), regulating its internalization and surface expression, and the cognate kinases GRK1 and GRK2. Determination of the crystal structures of Ca(2+)/NCS-1 alone and in complex with peptides derived from D2R and GRK1 reveals that the differential recognition is facilitated by the conformational flexibility of the C-lobe-binding site. We find that two copies of the D2R peptide bind within the hydrophobic crevice on Ca(2+)/NCS-1, but only one copy of the GRK1 peptide binds. The different binding modes are made possible by the C-lobe-binding site of NCS-1, which adopts alternative conformations in each complex. C-terminal residues Ser-178-Val-190 act in concert with the flexible EF3/EF4 loop region to effectively form different peptide-binding sites. In the Ca(2+)/NCS-1·D2R peptide complex, the C-terminal region adopts a 310 helix-turn-310 helix, whereas in the GRK1 peptide complex it forms an α-helix. Removal of Ser-178-Val-190 generated a C-terminal truncation mutant that formed a dimer, indicating that the NCS-1 C-terminal region prevents NCS-1 oligomerization. We propose that the flexible nature of the C-terminal region is essential to allow it to modulate its protein-binding sites and adapt its conformation to accommodate both ligands. This appears to be driven by the variability of the conformation of the C-lobe-binding site, which has ramifications for the target specificity and diversity of NCS-1. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Neuronal Calcium Sensor-1 Binds the D2 Dopamine Receptor and G-protein-coupled Receptor Kinase 1 (GRK1) Peptides Using Different Modes of Interactions*

PubMed Central

Pandalaneni, Sravan; Karuppiah, Vijaykumar; Saleem, Muhammad; Haynes, Lee P.; Burgoyne, Robert D.; Mayans, Olga; Derrick, Jeremy P.; Lian, Lu-Yun

2015-01-01

Neuronal calcium sensor-1 (NCS-1) is the primordial member of the neuronal calcium sensor family of EF-hand Ca2+-binding proteins. It interacts with both the G-protein-coupled receptor (GPCR) dopamine D2 receptor (D2R), regulating its internalization and surface expression, and the cognate kinases GRK1 and GRK2. Determination of the crystal structures of Ca2+/NCS-1 alone and in complex with peptides derived from D2R and GRK1 reveals that the differential recognition is facilitated by the conformational flexibility of the C-lobe-binding site. We find that two copies of the D2R peptide bind within the hydrophobic crevice on Ca2+/NCS-1, but only one copy of the GRK1 peptide binds. The different binding modes are made possible by the C-lobe-binding site of NCS-1, which adopts alternative conformations in each complex. C-terminal residues Ser-178–Val-190 act in concert with the flexible EF3/EF4 loop region to effectively form different peptide-binding sites. In the Ca2+/NCS-1·D2R peptide complex, the C-terminal region adopts a 310 helix-turn-310 helix, whereas in the GRK1 peptide complex it forms an α-helix. Removal of Ser-178–Val-190 generated a C-terminal truncation mutant that formed a dimer, indicating that the NCS-1 C-terminal region prevents NCS-1 oligomerization. We propose that the flexible nature of the C-terminal region is essential to allow it to modulate its protein-binding sites and adapt its conformation to accommodate both ligands. This appears to be driven by the variability of the conformation of the C-lobe-binding site, which has ramifications for the target specificity and diversity of NCS-1. PMID:25979333

Innervation of the wrist joint and surgical perspectives of denervation.

PubMed

Van de Pol, Gerrit J; Koudstaal, Maarten J; Schuurman, Arnold H; Bleys, Ronald L A W

2006-01-01

Because our experience with the techniques used in denervation surgery of the wrist joint often has proven insufficient in treating chronic pain we conducted an anatomic study to clarify the exact contributions of the nerves supplying the wrist joint. Our goal was to reveal all periosteal and capsular nerve connections and if necessary adjust our technique used in denervation surgery. Innervation of the wrist joint was investigated by microdissection and histologic examination of 18 human wrists. An acetylcholinesterase method was used to identify the nerves, both in whole-mount preparations and in sections. We found that the main innervation to the wrist capsule and periosteal nerve network came from the anterior interosseous nerve, lateral antebrachial cutaneous nerve, and posterior interosseous nerve. The palmar cutaneous branch of the median nerve, the deep branch of the ulnar nerve, the superficial branch of the radial nerve, and the dorsal branch of the ulnar nerve also were found to have connections with the capsule. The periosteal nerve branches did not appear to play a major role in the innervation of the capsule and ligaments; here the specific articular nerve branches proved more important. The posterior and medial antebrachial cutaneous nerves did not connect to the wrist capsule or periosteum but rather terminated in the extensor and flexor retinaculum. Based on our findings we propose to denervate the wrist by making 2 incisions. With one palmar and one dorsal incision it should be possible to disconnect the periosteum from the capsule and interrupt the majority of the capsular nerve branches.

Gastric Bypass Surgery Recruits a Gut PPAR-α-Striatal D1R Pathway to Reduce Fat Appetite in Obese Rats.

PubMed

Hankir, Mohammed K; Seyfried, Florian; Hintschich, Constantin A; Diep, Thi-Ai; Kleberg, Karen; Kranz, Mathias; Deuther-Conrad, Winnie; Tellez, Luis A; Rullmann, Michael; Patt, Marianne; Teichert, Jens; Hesse, Swen; Sabri, Osama; Brust, Peter; Hansen, Harald S; de Araujo, Ivan E; Krügel, Ute; Fenske, Wiebke K

2017-02-07

Bariatric surgery remains the single most effective long-term treatment modality for morbid obesity, achieved mainly by lowering caloric intake through as yet ill-defined mechanisms. Here we show in rats that Roux-en-Y gastric bypass (RYGB)-like rerouting of ingested fat mobilizes lower small intestine production of the fat-satiety molecule oleoylethanolamide (OEA). This was associated with vagus nerve-driven increases in dorsal striatal dopamine release. We also demonstrate that RYGB upregulates striatal dopamine 1 receptor (D1R) expression specifically under high-fat diet feeding conditions. Mechanistically, interfering with local OEA, vagal, and dorsal striatal D1R signaling negated the beneficial effects of RYGB on fat intake and preferences. These findings delineate a molecular/systems pathway through which bariatric surgery improves feeding behavior and may aid in the development of novel weight loss strategies that similarly modify brain reward circuits compromised in obesity. Copyright © 2017 Elsevier Inc. All rights reserved.

Highly sensitive detection of quantal dopamine secretion from pheochromocytoma cells using neural microelectrode array electrodeposited with polypyrrole graphene.

PubMed

Wang, Li; Xu, Huiren; Song, Yilin; Luo, Jinping; Wei, Wenjing; Xu, Shengwei; Cai, Xinxia

2015-04-15

For the measurement of events of dopamine (DA) release as well as the coordinating neurotransmission in the nerve system, a neural microelectrode array (nMEA) electrodeposited directionally with polypyrrole graphene (PG) nanocomposites was fabricated. The deposited graphene significantly increased the surface area of working electrode, which led to the nMEA (with diameter of 20 μm) with excellent selectivity and sensitivity to DA. Furthermore, PG film modification exhibited low detection limit (4 nM, S/N = 3.21), high sensitivity, and good linearity in the presence of ascorbic acid (e.g., 13933.12 μA mM(-1) cm(-2) in the range of 0.8-10 μM). In particular, the nMEA combined with the patch-clamp system was used to detect quantized DA release from pheochromocytoma cells under 100 mM K(+) stimulation. The nMEA that integrates 60 microelectrodes is novel for detecting a large number of samples simultaneously, which has potential for neural communication research.

Tertiary Oximes on Brain Acetylcholinesterase and Central Excitatory Effects of Nerve Agents

DTIC Science & Technology

2012-01-01

5 test doses of the oxime. Animals were euthanized 45 min after oxime treatment when blood and target tissues were collected. AChE activity was...the ability of MINA and DHAP to block or terminate nerve agent-induced electroencephalographic (EEG) seizure activity was evaluated. Animals...instrumented to record brain EEG activity were challenged with a seizure-inducing dose (2.0 x LD50) of GB, GF, or VX, and oxime was administered one min

The release of acetylcholine from post-ganglionic cell bodies in response to depolarization.

PubMed Central

Johnson, D A; Pilar, G

1980-01-01

1. Acetylcholine (Ach) release from parasympathetic ganglia cell somata was investigated in denervated avian ciliary ganglia. Three days after the input to the ganglion (the oculomotor nerve) was sectioned, all presynaptic nerve terminals had degenerated. 2. Denervated ganglia were shown to contain endogenous ACh and to be capable of synthesizing [3H]ACh from [3H]choline added to the incubation medium. 3. In response to depolarization induced by incubation in 50 mM-[K+]o, denervated ganglia released [3H]ACh into bath effluents in amounts approximately 15% of the non-denervated contralateral control. This release was shown to be Ca2+ dependent in both intact and denervated ganglia. 4. Antidromic electrical stimulation of ciliary nerves also elicited [3H]ACh release. Nicotine (1 microgram/microliter.) depolarized denervated ciliary ganglion cells and evoked release of the transmitter and this release was antagonized by curare. 5. It is concluded that the ganglionic cell bodies sysnthesized ACh and released the transmitter in response to K+ depolarization, antidromic stimulation and cholinergic agonists, despite the lack of morphological specializations usually associated with stimulus-induced release of neurotransmitter. The evidence suggests the existence of a mechanism of transmitter release which is Ca2+ dependent, probably from a cytoplasmic pool and therefore distinct from the usual vesicular release at the nerve terminal. Images Plate 1 Plate 2 PMID:6247485

Supersensitive Kappa Opioid Receptors Promotes Ethanol Withdrawal-Related Behaviors and Reduce Dopamine Signaling in the Nucleus Accumbens.

PubMed

Rose, Jamie H; Karkhanis, Anushree N; Chen, Rong; Gioia, Dominic; Lopez, Marcelo F; Becker, Howard C; McCool, Brian A; Jones, Sara R

2016-05-01

Chronic ethanol exposure reduces dopamine transmission in the nucleus accumbens, which may contribute to the negative affective symptoms associated with ethanol withdrawal. Kappa opioid receptors have been implicated in withdrawal-induced excessive drinking and anxiety-like behaviors and are known to inhibit dopamine release in the nucleus accumbens. The effects of chronic ethanol exposure on kappa opioid receptor-mediated changes in dopamine transmission at the level of the dopamine terminal and withdrawal-related behaviors were examined. Five weeks of chronic intermittent ethanol exposure in male C57BL/6 mice were used to examine the role of kappa opioid receptors in chronic ethanol-induced increases in ethanol intake and marble burying, a measure of anxiety/compulsive-like behavior. Drinking and marble burying were evaluated before and after chronic intermittent ethanol exposure, with and without kappa opioid receptor blockade by nor-binaltorphimine (10mg/kg i.p.). Functional alterations in kappa opioid receptors were assessed using fast scan cyclic voltammetry in brain slices containing the nucleus accumbens. Chronic intermittent ethanol-exposed mice showed increased ethanol drinking and marble burying compared with controls, which was attenuated with kappa opioid receptor blockade. Chronic intermittent ethanol-induced increases in behavior were replicated with kappa opioid receptor activation in naïve mice. Fast scan cyclic voltammetry revealed that chronic intermittent ethanol reduced accumbal dopamine release and increased uptake rates, promoting a hypodopaminergic state of this region. Kappa opioid receptor activation with U50,488H concentration-dependently decreased dopamine release in both groups; however, this effect was greater in chronic intermittent ethanol-treated mice, indicating kappa opioid receptor supersensitivity in this group. These data suggest that the chronic intermittent ethanol-induced increase in ethanol intake and anxiety/compulsive-like behaviors may be driven by greater kappa opioid receptor sensitivity and a hypodopaminergic state of the nucleus accumbens. © The Author 2015. Published by Oxford University Press on behalf of CINP.

Cytoarchitectonic study of the brain of a dwarf snakehead, Channa gachua (Ham.). I. The telencephalon.

PubMed

Baile, Vidya V; Patle, Pratap J

2011-12-01

Cytoarchitectonic pattern of the telencephalon of a dwarf snakehead, Channa gachua, is studied by serial transverse sections of the brain (Kluver and Barrera staining). On the anteriormost extremity of the telencephalon, olfactory bulbs terminate that are sessile. The olfactory bulbs comprise four concentric layers, which from outside toward the center are olfactory nerve layer, a glomerular layer, mitral cell layer, and internal cell layer. Large terminal nerve ganglion cells are prominently visible in the dorsomedial position where the bulbs terminate on the telencephalon. In all, 24 nuclei are identified in the telencephalon on ventral and dorsal areas and are named according to their position. Ventral telencephalon exhibits 11 nuclei. On the dorsal telencephalon, there are 13 nuclei. These again are named according to their position on dorsal, ventral, median, lateral, or posterior part. This study reported for the first time in this fish will be useful in tracing the neuronal system of Channa gachua and subsequent studies of the functional aspects of these nuclei in the regulation of reproductive cycle of this species.

The effects of lubrol WX on brain membrane Ca2+/Mg2+ ATPase and ATP-dependent Ca2+ uptake activity following acute and chronic ethanol.

PubMed

Ross, D H; Garrett, K M; Cardenas, H L

1985-02-01

Acute administration of ethanol (2.5 gm/kg, i.p.) to rats inhibits the cytosolic buffering of Ca2+ in nerve terminals. Ca2+ ATPase and ATP-dependent Ca2+ uptake are both inhibited 30 min after a single dose of ethanol. Chronic ethanol administration (6%, 14 days) did not inhibit Ca2+ ATPase but significantly stimulated ATP-dependent Ca2+ uptake. Lubrol WX treatment of acute ethanolic membranes reverses the inhibition of Ca2+ ATPase seen following ethanol. Lubrol WX treatment of chronic ethanolic membranes prevents the increase in ATP-dependent Ca2+ uptake seen in ethanolic membranes. Both acute and chronic ethanol-induced changes in Ca2+ transport within nerve terminals may involve lipid-dependent parameters of the membrane which may underlie neuronal adaptation.

The effects of combined application of inorganic Martian dust simulant and carbon dots on glutamate transport rat brain nerve terminals

NASA Astrophysics Data System (ADS)

Borisova, Tatiana; Krisanova, Natalia; Nazarova, Anastasiya; Borysov, Arseniy; Pastukhov, Artem; Pozdnyakova, Natalia; Dudarenko, Marina

2016-07-01

During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and can be transported to the central nervous system (Oberdorster et al., 2004). Recently, the research team of this study found the minor fractions of nanoparticles with the size ~ 50 -60 nm in Lunar and Martian dust stimulants (JSC-1a and JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin), whereas the average size of the simulants was 1 mm and 4mm, respectively (Krisanova et al., 2013). Also, the research team of this study discovered new phenomenon - the neuromodulating and neurotoxic effect of carbon nano-sized particles - Carbon dots (C-dots), originated from ash of burned carbon-containing product (Borisova et al, 2015). The aims of this study was to analyse acute effects of upgraded stimulant of inorganic Martian dust derived from volcanic ash (JSC-1a/JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin) by the addition of carbon components, that is, carbon dots, on the key characteristic of synaptic neurotransmission. Acute administration of carbon-containing Martian dust analogue resulted in a significant decrease in transporter-mediated uptake of L-[14C]glutamate (the major excitatory neurotransmitter) by isolated rat brain nerve terminals. The ambient level of the neurotransmitter in the preparation of nerve terminals increased in the presence of carbon dot-contained Martian dust analogue. These effects were associated with action of carbon component of the upgraded Martian dust stimulant but not with its inorganic constituent.

Novel technique for repair of severed peripheral nerves in rats using polyurea crosslinked silica aerogel scaffold.

PubMed

Sabri, Firouzeh; Gerth, David; Tamula, George-Rudolph M; Phung, Thien-Chuong N; Lynch, Kyle J; Boughter, John D

2014-10-01

To design, synthesize, and test in vivo an aerogel-based top-open peripheral nerve scaffold to simultaneously support and guide multiple completely severed peripheral nerves in a rat model. Also, to explore options for immobilizing severed nerves on the aerogel material without the use of sutures resulting in reduced surgical time. A novel material and approach was developed for the reattachment of severed peripheral nerves. Nerve confinement and alignment in this case relies on the surface properties of a lightweight, highly porous, polyurea crosslinked silica aerogel scaffold. The distal and proximal ends of completely transected nerve terminals were positioned inside prefabricated "top-open" corrugated channels that cradled approximately two thirds of the circumference of the nerve trunk and connectivity of the severed nerves was evaluated using sciatic function index (SFI) technique for five months post-surgery on 10 female Sprague-Dawley rats then compared with the gold standard for peripheral nerve repair. The interaction of nerves with the surface of the scaffold was investigated also. Multichannel aerogel-based nerve support scaffold showed similar SFI recovery trend as the case suture repair technique. Usage of an adhesion-promoting coating reduced the friction between the nerve and the scaffold leading to slippage and lack of attachment between nerve and surface. The aerogel scaffold used in this study did not collapse under pressure during the incubation period and allowed for a rapid and non-invasive peripheral nerve repair approach without the demands of microsurgery on both time and surgical expertise. This technique may allow for simultaneous repair and reconnection of multiple severed nerves particularly relevant to nerve branching sites.

Correlation of ultrasound appearance, gross anatomy, and histology of the femoral nerve at the femoral triangle.

PubMed

Lonchena, Tiffany K; McFadden, Kathryn; Orebaugh, Steven L

2016-01-01

Correlation between ultrasound appearance, gross anatomic characteristics, and histologic structure of the femoral nerve (FN) is lacking. Utilizing cadavers, we sought to characterize the anatomy of the FN, and provide a quantitative measure of its branching. We hypothesize that at the femoral crease, the FN exists as a group of nerve branches, rather than a single nerve structure, and secondarily, that this transition into many branches is apparent on ultrasonography. Nineteen preserved cadavers were investigated. Ultrasonography was sufficient to evaluate the femoral nerve in nine specimens; gross dissection was utilized in all 19. Anatomic characteristics were recorded, including distances from the inguinal ligament to femoral crease, first nerve branch, and complete arborization of the nerve. The nerves from nine specimens were excised for histologic analysis. On ultrasound, the nerve became more flattened, widened, and less discrete as it coursed distally. Branching of the nerve was apparent in 12 of 18 images, with mean distance from inguinal ligament of 3.9 (1.0) cm. However, upon dissection, major branching of the femoral nerve occurred at 3.1 (1.0) cm distal to the inguinal ligament, well proximal to the femoral crease. Histologic analysis was consistent with findings at dissection. The femoral nerve arborizes into multiple branches between the inguinal ligament and the femoral crease. Initial branching is often high in the femoral triangle. As hypothesized, the FN exists as a closely associated group of nerve branches at the level of the femoral crease; however, the termination of the nerve into multiple branches is not consistently apparent on ultrasonography.

Substance P enhances electrical field stimulation-induced mast cell degranulation in rat trachea.

PubMed

Hua, X Y; Back, S M; Tam, E K

1996-06-01

We previously demonstrated in an ex vivo rat tracheal model that chymotryptic activity is an index of mast cell degranulation and that substance P (SP) and electrical field stimulation (EFS) synergistically degranulate mucosal and connective tissue mast cells. In the current study, we found that the facilitatory effect of SP was apparent at concentrations as low as 10(-9) M. This effect was mimicked by 10(-7) M neurokinin A or by 10(-6) M capsaicin and was blocked by the NK1 receptor antagonist CP-96,345. SP + EFS-induced mast cell secretion was significantly attenuated by 10(-6) M tetrodotoxin. The response was also attenuated in tracheas from rats in which sensory nerves had been depleted by systemic pretreatment with capsaicin or in which sympathetic nerves had been depleted by systemic pretreatment with 6-hydroxy-dopamine. Atropine (10(-6) M) or indomethacin (10(-5) M) also attenuated SP + EFS-induced mast cell secretion. Our findings suggest the importance of a sensitizing rather than a direct stimulating effect of SP on mast cell degranulation. SP may increase the sensitivity of mast cells to EFS-discharged mediators or facilitate the release of mast cell-stimulating mediators from autonomic nerves.

Effects of cysteamine on dopamine-mediated behaviors: evidence for dopamine-somatostatin interactions in the striatum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin-Iverson, M.T.; Radke, J.M.; Vincent, S.R.

1986-06-01

The effects of prior treatment with cysteamine, a drug which appears to deplete selectively the neuropeptide somatostatin, on apomorphine-induced stereotypy and amphetamine-induced locomotor activity and conditioned place preferences were investigated. Twelve hours following systemic cysteamine injections apomorphine-induced stereotypy was attenuated and striatal somatostatin levels were reduced by half. Systemic cysteamine also decreased the motor stimulant effects of amphetamine, without influencing the rewarding properties as determined by the conditioned place preference procedure. Direct injections of cysteamine into the nucleus accumbens also decreased the locomotor response to amphetamine, and produced a local reduction in somatostatin levels in the accumbens. Cysteamine did notmore » appear to alter monoamine turnover in the striatum after either systemic or intra-accumbens injections. These results suggest that somatostatin in the nucleus accumbens and caudate-putamen modulates the motor, but not the reinforcing properties of dopaminergic drugs, possibly via an action postsynaptic to dopamine-releasing terminals. Furthermore, it is evident from these results that cysteamine is an important tool with which to study the central actions of somatostatin.« less

Dopamine activates the motor pattern for crawling in the medicinal leech.

PubMed

Puhl, Joshua G; Mesce, Karen A

2008-04-16

Locomotion in segmented animals is thought to be based on the coupling of "unit burst generators," but the biological nature of the unit burst generator has been revealed in only a few animal systems. We determined that dopamine (DA), a universal modulator of motor activity, is sufficient to activate fictive crawling in the medicinal leech, and can exert its actions within the smallest division of the animal's CNS, the segmental ganglion. In the entire isolated nerve cord or in the single ganglion, DA induced slow antiphasic bursting (approximately 15 s period) of motoneurons known to participate in the two-step elongation-contraction cycle underlying crawling behavior. During each cycle, the dorsal (DE-3) and ventral (VE-4) longitudinal excitor motoneurons fired approximately 180 degrees out of phase from the ventrolateral circular excitor motoneuron (CV), which marks the elongation phase. In many isolated whole nerve cords, DE-3 bursting progressed in an anterior to posterior direction with intersegmental phase delays appropriate for crawling. In the single ganglion, the dorsal (DI-1) and ventral (VI-2) inhibitory longitudinal motoneurons fired out of phase with each DE-3 burst, further confirming that the crawl unit burst generator exists in the single ganglion. All isolated ganglia of the CNS were competent to produce DA-induced robust fictive crawling, which typically lasted uninterrupted for 5-15 min. A quantitative analysis indicated that DA-induced crawling was not significantly different from electrically evoked or spontaneous crawling. We conclude that DA is sufficient to activate the full crawl motor program and that the kernel for crawling resides within each segmental ganglion.

Measuring Synaptic Vesicle Endocytosis in Cultured Hippocampal Neurons.

PubMed

Villarreal, Seth; Lee, Sung Hoon; Wu, Ling-Gang

2017-09-04

During endocytosis, fused synaptic vesicles are retrieved at nerve terminals, allowing for vesicle recycling and thus the maintenance of synaptic transmission during repetitive nerve firing. Impaired endocytosis in pathological conditions leads to decreases in synaptic strength and brain functions. Here, we describe methods used to measure synaptic vesicle endocytosis at the mammalian hippocampal synapse in neuronal culture. We monitored synaptic vesicle protein endocytosis by fusing a synaptic vesicular membrane protein, including synaptophysin and VAMP2/synaptobrevin, at the vesicular lumenal side, with pHluorin, a pH-sensitive green fluorescent protein that increases its fluorescence intensity as the pH increases. During exocytosis, vesicular lumen pH increases, whereas during endocytosis vesicular lumen pH is re-acidified. Thus, an increase of pHluorin fluorescence intensity indicates fusion, whereas a decrease indicates endocytosis of the labelled synaptic vesicle protein. In addition to using the pHluorin imaging method to record endocytosis, we monitored vesicular membrane endocytosis by electron microscopy (EM) measurements of Horseradish peroxidase (HRP) uptake by vesicles. Finally, we monitored the formation of nerve terminal membrane pits at various times after high potassium-induced depolarization. The time course of HRP uptake and membrane pit formation indicates the time course of endocytosis.

Sensory Innervation of the Nonspecialized Connective Tissues in the Low Back of the Rat

PubMed Central

Corey, Sarah M.; Vizzard, Margaret A.; Badger, Gary J.; Langevin, Helene M.

2011-01-01

Chronic musculoskeletal pain, including low back pain, is a worldwide debilitating condition; however, the mechanisms that underlie its development remain poorly understood. Pathological neuroplastic changes in the sensory innervation of connective tissue may contribute to the development of nonspecific chronic low back pain. Progress in understanding such potentially important abnormalities is hampered by limited knowledge of connective tissue's normal sensory innervation. The goal of this study was to evaluate and quantify the sensory nerve fibers terminating within the nonspecialized connective tissues in the low back of the rat. With 3-dimensional reconstructions of thick (30–80 μm) tissue sections we have for the first time conclusively identified sensory nerve fiber terminations within the collagen matrix of connective tissue in the low back. Using dye labeling techniques with Fast Blue, presumptive dorsal root ganglia cells that innervate the low back were identified. Of the Fast Blue-labeled cells, 60–88% also expressed calcitonin gene-related peptide (CGRP) immunoreactivity. Based on the immunolabeling with CGRP and the approximate size of these nerve fibers (≤2 μm) we hypothesize that they are Aδ or C fibers and thus may play a role in the development of chronic pain. PMID:21411968

Impact of serotonin 2C receptor null mutation on physiology and behavior associated with nigrostriatal dopamine pathway function.

PubMed

Abdallah, Luna; Bonasera, Stephen J; Hopf, F Woodward; O'Dell, Laura; Giorgetti, Marco; Jongsma, Minke; Carra, Scott; Pierucci, Massimo; Di Giovanni, Giuseppe; Esposito, Ennio; Parsons, Loren H; Bonci, Antonello; Tecott, Laurence H

2009-06-24

The impact of serotonergic neurotransmission on brain dopaminergic pathways has substantial relevance to many neuropsychiatric disorders. A particularly prominent role has been ascribed to the inhibitory effects of serotonin 2C receptor (5-HT(2C)R) activation on physiology and behavior mediated by the mesolimbic dopaminergic pathway, particularly in the terminal region of the nucleus accumbens. The influence of this receptor subtype on functions mediated by the nigrostriatal dopaminergic pathway is less clear. Here we report that a null mutation eliminating expression of 5-HT(2C)Rs produces marked alterations in the activity and functional output of this pathway. 5-HT(2C)R mutant mice displayed increased activity of substantia nigra pars compacta (SNc) dopaminergic neurons, elevated baseline extracellular dopamine concentrations in the dorsal striatum (DSt), alterations in grooming behavior, and enhanced sensitivity to the stereotypic behavioral effects of d-amphetamine and GBR 12909. These psychostimulant responses occurred in the absence of phenotypic differences in drug-induced extracellular dopamine concentration, suggesting a phenotypic alteration in behavioral responses to released dopamine. This was further suggested by enhanced behavioral responses of mutant mice to the D(1) receptor agonist SKF 81297. Differences in DSt D(1) or D(2) receptor expression were not found, nor were differences in medium spiny neuron firing patterns or intrinsic membrane properties following dopamine stimulation. We conclude that 5-HT(2C)Rs regulate nigrostriatal dopaminergic activity and function both at SNc dopaminergic neurons and at a locus downstream of the DSt.

Prevention and Treatment of Noise-Induced Tinnitus

DTIC Science & Technology

2012-07-01

process of completing the normative data base(s) of VGLUT1 , VAT and VGAT immunostaining in the rat AVCN and DCN that will allow assessment of changes under...our experimental conditions. Initial results indicate some loss of VGLUT1 immunolabeled auditory nerve terminals in the ventral cochlear nucleus...Research Accomplishments for TASK 3: Test the hypothesis that the loss of AN terminals (marked by VGLUT1 immunolabel) on neurons in the AVCN and

The neglected cranial nerve: nervus terminalis (cranial nerve N).

PubMed

Vilensky, Joel A

2014-01-01

The nervus terminalis (NT; terminal nerve) was clearly identified as an additional cranial nerve in humans more than a century ago yet remains mostly undescribed in modern anatomy textbooks. The nerve is referred to as the nervus terminalis because in species initially examined its fibers were seen entering the brain in the region of the lamina terminalis. It has also been referred to as cranial nerve 0, but because there is no Roman symbol for zero, an N for the Latin word nulla is a better numerical designation. This nerve is very distinct in human fetuses and infants but also has been repeatedly identified in adult human brains. The NT fibers are unmyelinated and emanate from ganglia. The fibers pass through the cribriform plate medial to those of the olfactory nerve fila. The fibers end in the nasal mucosa and probably arise from autonomic/neuromodulatory as well as sensory neurons. The NT has been demonstrated to release luteinizing-releasing luteinizing hormone and is therefore thought to play a role in reproductive behavior. Based on the available evidence, the NT appears to be functional in adult humans and should be taught in medical schools and incorporated into anatomy/neuroanatomy textbooks. Copyright © 2012 Wiley Periodicals, Inc., a Wiley company.

Abnormal afferent nerve endings in the soft palatal mucosa of sleep apnoics and habitual snorers.

PubMed

Friberg, D; Gazelius, B; Hökfelt, T; Nordlander, B

1997-07-23

Habitual snoring precedes obstructive sleep apnea (OSA), but the pathophysiological mechanisms behind progression are still unclear. The patency of upper airways depends on a reflexogen mechanism reacting on negative intrapharyngeal pressure at inspiration, probably mediated by mucosal receptors, i.e., via afferent nerve endings. Such nerves contain a specific nerve protein, protein-gene product 9.5 (PGP 9.5) and in some cases substance P (SP) and calcitonin gene-related (CGRP). Biopsies of the soft palatial mucosa were obtained from non-smoking men ten OSA patients, 11 habitual snorers and 11 non-snoring controls. The specimens were immunohistochemically analyzed for PGP 9.5, SP and CGRP. As compared to controls, an increased number of PGP-, SP- and CGRP-immunoreactive nerves were demonstrated in the mucosa in 9/10 OSA patients and 4/11 snorers, in addition to varicose nerve endings in the papillae and epithelium. Using double staining methodology, it could be shown that SP- and CGRP-like immunoreactivities (LIs) often coexisted in these fibres, as did CGRP- and PGP 9.5-LIs. The increased density in sensory nerve terminals are interpreted to indicate an afferent nerve lesion. Our results support the hypothesis of a progressive neurogenic lesion as a contributory factor to the collapse of upper airways during sleep in OSA patients.

Neuroprotective potential of spermidine against rotenone induced Parkinson's disease in rats.

PubMed

Sharma, Sunaina; Kumar, Puneet; Deshmukh, Rahul

2018-06-01

Parkinson's disease is a leading hypokinetic disorder characterized by selective loss of dopaminergic neurons in substantia nigra pars compacta (SNpc) region of mid-brain. Degeneration of dopaminergic neurons is considered to be due to oxidative stress, neuroinflammation, disturbed calcium homeostasis and glutamate excitotoxicity etc. Spermidine is a polyamine which counteracts age associated cell death by scavenging free radical formation, activates authophagic machinery by enhancing formation of autophagosome, and antagonizes NMDA receptor. In the current study we investigated the neuroprotective potential of spermidine against rotenone induced PD in rats. Rats were treated subcutaneously with rotenone 1.5 mg/kg daily for 28 days. Spermidine 5&10 mg/kg was administered orally 1 h prior to rotenone administration from 15 to 28. Rotenone caused significant reduction in motor functioning and elevated levels of oxidative stress markers and proinflammatory cytokines levels (IL-1β, IL6 and TNF-α). The neurochemical analysis revealed a significant decrease in serotonin, norepinephrine, dopamine and their metabolites accompanied by a significant loss of dopaminergic neurons in the SNpc following ROT injection. However, treatment with spermidine rescued DAergic neurons in SNpc and nerve terminals in the striatum following ROT insult. Spermidine treatment also attenuated oxidative stress, neuroinflammation and restored striatal neurochemistry. Results of our study suggest that spermidine has promising neuroprotective effect against degenerative changes in experimental PD, and the protective effects are mediated through its antioxidant and anti-inflammatory properties. Copyright © 2018 Elsevier Ltd. All rights reserved.

Bradykinin activates a cross-signaling pathway between sensory and adrenergic nerve endings in the heart: a novel mechanism of ischemic norepinephrine release?

PubMed

Seyedi, N; Maruyama, R; Levi, R

1999-08-01

We had shown that bradykinin (BK) generated by cardiac sympathetic nerve endings (i.e., synaptosomes) promotes exocytotic norepinephrine (NE) release in an autocrine mode. Because the synaptosomal preparation may include sensory C-fiber endings, which BK is known to stimulate, sensory nerves could contribute to the proadrenergic effects of BK in the heart. We report that BK is a potent releaser of NE from guinea pig heart synaptosomes (EC(50) approximately 20 nM), an effect mediated by B(2) receptors, and almost completely abolished by prior C-fiber destruction or blockade of calcitonin gene-related peptide and neurokinin-1 receptors. C-fiber destruction also greatly decreased BK-induced NE release from the intact heart, whereas tyramine-induced NE release was unaffected. Furthermore, C-fiber stimulation with capsaicin and activation of calcitonin gene-related peptide and neurokinin-1 receptors initiated NE release from cardiac synaptosomes, indicating that stimulation of sensory neurons in turn activates sympathetic nerve terminals. Thus, BK is likely to release NE in the heart in part by first liberating calcitonin gene-related peptide and Substance P from sensory nerve endings; these neuropeptides then stimulate specific receptors on sympathetic terminals. This action of BK is positively modulated by cyclooxygenase products, attenuated by activation of histamine H(3) receptors, and potentiated at a lower pH. The NE-releasing action of BK is likely to be enhanced in myocardial ischemia, when protons accumulate, C fibers become activated, and the production of prostaglandins and BK increases. Because NE is a major arrhythmogenic agent, the activation of this interneuronal signaling system between sensory and adrenergic neurons may contribute to ischemic dysrhythmias and sudden cardiac death.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

Our research efforts in the first funding year concentrated on animal and clinical studies validating {sup 11}C-hydroxyephedrine as a marker for norepinephrine uptake and storage in presynaptic sympathetic nerve terminals. In addition to kinetic studies in animals, the first clinical studies have been performed. {sup 11}C-hydroxyephedrine provides excellent image quality in the human heart with high myocardium to blood ratios. A canine model with transient intracoronary occlusion of the left anterior descending aorta was used to show decreased retention of tracer with ischemia. Clinical studies of patients with acute myocardial infarction showed an area of decreased retention of tracer exceedingmore » the infarct territory as defined by {sup 82}Rb blood flow imaging. We are also developing tracers for the parasympathetic nervous system. It appears that methyl-TRB is a specific tracer for this system. Studies of {sup 11}C- or {sup 18}F-benzovesamicol as a potential tracer for parasympathetic presynaptic nerve terminals are under way. (MHB)« less

Dynamin phosphorylation controls optimization of endocytosis for brief action potential bursts

PubMed Central

Armbruster, Moritz; Messa, Mirko; Ferguson, Shawn M; De Camilli, Pietro; Ryan, Timothy A

2013-01-01

Modulation of synaptic vesicle retrieval is considered to be potentially important in steady-state synaptic performance. Here we show that at physiological temperature endocytosis kinetics at hippocampal and cortical nerve terminals show a bi-phasic dependence on electrical activity. Endocytosis accelerates for the first 15–25 APs during bursts of action potential firing, after which it slows with increasing burst length creating an optimum stimulus for this kinetic parameter. We show that activity-dependent acceleration is only prominent at physiological temperature and that the mechanism of this modulation is based on the dephosphorylation of dynamin 1. Nerve terminals in which dynamin 1 and 3 have been replaced with dynamin 1 harboring dephospho- or phospho-mimetic mutations in the proline-rich domain eliminate the acceleration phase by either setting endocytosis at an accelerated state or a decelerated state, respectively. DOI: http://dx.doi.org/10.7554/eLife.00845.001 PMID:23908769

TRPA1 activation by lidocaine in nerve terminals results in glutamate release increase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piao, L.-H.; Fujita, Tsugumi; Jiang, C.-Y.

2009-02-20

We examined the effects of local anesthetics lidocaine and procaine on glutamatergic spontaneous excitatory transmission in substantia gelatinosa (SG) neurons in adult rat spinal cord slices with whole-cell patch-clamp techniques. Bath-applied lidocaine (1-5 mM) dose-dependently and reversibly increased the frequency but not the amplitude of spontaneous excitatory postsynaptic current (sEPSC) in SG neurons. Lidocaine activity was unaffected by the Na{sup +}-channel blocker, tetrodotoxin, and the TRPV1 antagonist, capsazepine, but was inhibited by the TRP antagonist, ruthenium red. In the same neuron, the TRPA1 agonist, allyl isothiocyanate, and lidocaine both increased sEPSC frequency. In contrast, procaine did not produce presynaptic enhancement.more » These results indicate that lidocaine activates TRPA1 in nerve terminals presynaptic to SG neurons to increase the spontaneous release of L-glutamate.« less

Selective inhibition of dopamine-beta-hydroxylase enhances dopamine release from noradrenergic terminals in the medial prefrontal cortex.

PubMed

Devoto, Paola; Flore, Giovanna; Saba, Pierluigi; Frau, Roberto; Gessa, Gian L

2015-10-01

Disulfiram has been claimed to be useful in cocaine addiction therapy, its efficacy being attributed to dopamine-beta-hydroxylase (DBH) inhibition. Our previous results indicate that disulfiram and the selective DBH inhibitor nepicastat increase extracellular dopamine (DA) in the rat medial prefrontal cortex (mPFC), and markedly potentiated cocaine-induced increase. Concomitantly, in rats with cocaine self-administration history, cocaine-seeking behavior induced by drug priming was prevented, probably through overstimulation of D1 receptors due to the DA increase. The present research was aimed at studying the neurochemical mechanisms originating the enhanced DA release. Noradrenergic system ablation was attained by intracerebroventricular (i.c.v.) administration of the neurotoxin anti-DBH-saporin (aDBH-sap). DA, noradrenaline (NA), and DOPAC were assessed by HPLC after ex vivo tissue extraction or in vivo microdialysis. Control and denervated rats were subjected to microdialysis in the mPFC and caudate nucleus to evaluate the effect of nepicastat-cocaine combination on extracellular DA levels and their regulation by α2-adrenoceptors. Fifteen days after neurotoxin or its vehicle administration, tissue and extracellular NA were reduced to less than 2% the control value, while extracellular DA was increased by approximately 100%. In control rats, nepicastat given alone and in combination with cocaine increased extracellular DA by about 250% and 1100%, respectively. In denervated rats, nepicastat slightly affected extracellular DA, while in combination with cocaine increased extracellular DA by 250%. No differences were found in the caudate nucleus. Clonidine almost totally reversed the extracellular DA elevation produced by nepicastat-cocaine combination, while it was ineffective in denervated rats. This research shows that the increase of extracellular DA produced by nepicastat alone or in combination with cocaine was prevented by noradrenergic denervation. The results indicate that nepicastat enhances DA release from noradrenergic terminals supposedly by removing NA from α2-autoreceptors. In addition to the inhibition of DA uptake, the latter mechanism may explain the synergistic effect of cocaine on nepicastat-induced DA release.

Mechanisms of α-Synuclein Induced Synaptopathy in Parkinson's Disease

PubMed Central

Bridi, Jessika C.; Hirth, Frank

2018-01-01

Parkinson's disease (PD) is characterized by intracellular inclusions of aggregated and misfolded α-Synuclein (α-Syn), and the loss of dopaminergic (DA) neurons in the brain. The resulting motor abnormalities mark the progression of PD, while non-motor symptoms can already be identified during early, prodromal stages of disease. Recent studies provide evidence that during this early prodromal phase, synaptic and axonal abnormalities occur before the degenerative loss of neuronal cell bodies. These early phenotypes can be attributed to synaptic accumulation of toxic α-Syn. Under physiological conditions, α-Syn functions in its native conformation as a soluble monomer. However, PD patient brains are characterized by intracellular inclusions of insoluble fibrils. Yet, oligomers and protofibrils of α-Syn have been identified to be the most toxic species, with their accumulation at presynaptic terminals affecting several steps of neurotransmitter release. First, high levels of α-Syn alter the size of synaptic vesicle pools and impair their trafficking. Second, α-Syn overexpression can either misregulate or redistribute proteins of the presynaptic SNARE complex. This leads to deficient tethering, docking, priming and fusion of synaptic vesicles at the active zone (AZ). Third, α-Syn inclusions are found within the presynaptic AZ, accompanied by a decrease in AZ protein levels. Furthermore, α-Syn overexpression reduces the endocytic retrieval of synaptic vesicle membranes during vesicle recycling. These presynaptic alterations mediated by accumulation of α-Syn, together impair neurotransmitter exocytosis and neuronal communication. Although α-Syn is expressed throughout the brain and enriched at presynaptic terminals, DA neurons are the most vulnerable in PD, likely because α-Syn directly regulates dopamine levels. Indeed, evidence suggests that α-Syn is a negative modulator of dopamine by inhibiting enzymes responsible for its synthesis. In addition, α-Syn is able to interact with and reduce the activity of VMAT2 and DAT. The resulting dysregulation of dopamine levels directly contributes to the formation of toxic α-Syn oligomers. Together these data suggest a vicious cycle of accumulating α-Syn and deregulated dopamine that triggers synaptic dysfunction and impaired neuronal communication, ultimately causing synaptopathy and progressive neurodegeneration in Parkinson's disease. PMID:29515354

Comparative proteomic analysis of differentially expressed proteins between peripheral sensory and motor nerves.

PubMed

He, Qianru; Man, Lili; Ji, Yuhua; Zhang, Shuqiang; Jiang, Maorong; Ding, Fei; Gu, Xiaosong

2012-06-01

Peripheral sensory and motor nerves have different functions and different approaches to regeneration, especially their distinct ability to accurately reinervate terminal nerve pathways. To understand the molecular aspects underlying these differences, the proteomics technique by coupling isobaric tags for relative and absolute quantitation (iTRAQ) with online two-dimensional liquid chromatography tandem mass spectrometry (2D LC-MS/MS) was used to investigate the protein profile of sensory and motor nerve samples from rats. A total of 1472 proteins were identified in either sensory or motor nerve. Of them, 100 proteins showed differential expressions between both nerves, and some of them were validated by quantitative real time RT-PCR, Western blot analysis, and immunohistochemistry. In the light of functional categorization, the differentially expressed proteins in sensory and motor nerves, belonging to a broad range of classes, were related to a diverse array of biological functions, which included cell adhesion, cytoskeleton, neuronal plasticity, neurotrophic activity, calcium-binding, signal transduction, transport, enzyme catalysis, lipid metabolism, DNA-binding, synaptosome function, actin-binding, ATP-binding, extracellular matrix, and commitment to other lineages. The relatively higher expressed proteins in either sensory or motor nerve were tentatively discussed in combination with their specific molecular characteristics. It is anticipated that the database generated in this study will provide a solid foundation for further comprehensive investigation of functional differences between sensory and motor nerves, including the specificity of their regeneration.

Neuroprotective effects of (-)-epigallocatechin-3-gallate (EGCG) against peripheral nerve transection-induced apoptosis.

PubMed

Kian, Kosar; Khalatbary, Ali Reza; Ahmadvand, Hassan; Karimpour Malekshah, Abbasali; Shams, Zahra

2018-01-02

Recent studies revealed the neuroprotective effects of epigallocatechin-3-gallate (EGCG) on a variety of neural injury models. The purpose of this study was to determine the neuroprotective effects of EGCG following sciatic nerve transection (SNT). Rats were randomly divided into four groups each as follows: Sham-operated group, SNT group, and Pre-EGCG (50-mg/kg, i.p., 30 minutes before nerve transection and followed for 3 days) and Post-EGCG (50-mg/kg, i.p., 1 hour after nerve transection and followed for 3 days) groups. Spinal cord segments of the sciatic nerve and related dorsal root ganglions were removed four weeks after nerve transection for the assessment of malondialdehyde (MDA) levels, superoxide dismutase (SOD) and catalase (CAT) activities, immunohistochemistry of caspase-3, cyclooxygenase-2 (COX-2), S100beta (S100B), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). MDA levels were significantly decreased, and SOD and CAT activities were significantly increased in EGCG-treated rats after nerve transection. Attenuated caspase-3 and COX-2 expression, and TUNEL reaction could be significantly detected in the EGCG-treated rats after nerve transection. Also, EGCG significantly increased S100B expression. We propose that EGCG may be effective in the protection of neuronal cells against retrograde apoptosis and may enhance neuronal survival time following nerve transection.

Antihypertensive effect of etamicastat in dopamine D2 receptor-deficient mice.

PubMed

Armando, Ines; Asico, Laureano D; Wang, Xiaoyan; Jones, John E; Serrão, Maria Paula; Cuevas, Santiago; Grandy, David K; Soares-da-Silva, Patricio; Jose, Pedro A

2018-04-13

Abnormalities of the D 2 R gene (DRD2) play a role in the pathogenesis of human essential hypertension; variants of the DRD2 have been reported to be associated with hypertension. Disruption of Drd2 (D 2 -/- ) in mice increases blood pressure. The hypertension of D 2 -/- mice has been related, in part, to increased sympathetic activity, renal oxidative stress, and renal endothelin B receptor (ETBR) expression. We tested in D 2 -/- mice the effect of etamicastat, a reversible peripheral inhibitor of dopamine-β-hydroxylase that reduces the biosynthesis of norepinephrine from dopamine and decreases sympathetic nerve activity. Blood pressure was measured in anesthetized D 2 -/- mice treated with etamicastat by gavage, (10 mg/kg), conscious D 2 -/- mice, and D 2 +/+ littermates, and mice with the D 2 R selectively silenced in the kidney, treated with etamicastat in the drinking water (10 mg/kg per day). Tissue and urinary catecholamines and renal expression of selected G protein-coupled receptors, enzymes related to the production of reactive oxygen species, and sodium transporters were also measured. Etamicastat decreased blood pressure both in anesthetized and conscious D 2 -/- mice and mice with renal-selective silencing of D 2 R to levels similar or close to those measured in D 2 +/+ littermates. Etamicastat decreased cardiac and renal norepinephrine and increased cardiac and urinary dopamine levels in D 2 -/- mice. It also normalized the increased renal protein expressions of ETBR, NADPH oxidase isoenzymes, and urinary 8-isoprostane, as well as renal NHE3 and NCC, and increased the renal expression of D 1 R but not D 5 R in D 2 -/- mice. In conclusion, etamicastat is effective in normalizing the increased blood pressure and some of the abnormal renal biochemical alterations of D 2 -/- mice.

Identification of PN1, a Predominant Voltage-Dependent Sodium Channel Expressed Principally in Peripheral Neurons

NASA Astrophysics Data System (ADS)

Toledo-Aral, Juan J.; Moss, Brenda L.; He, Zhi-Jun; Koszowski, Adam G.; Whisenand, Teri; Levinson, Simon R.; Wolf, John J.; Silos-Santiago, Inmaculada; Halegoua, Simon; Mandel, Gail

1997-02-01

Membrane excitability in different tissues is due, in large part, to the selective expression of distinct genes encoding the voltage-dependent sodium channel. Although the predominant sodium channels in brain, skeletal muscle, and cardiac muscle have been identified, the major sodium channel types responsible for excitability within the peripheral nervous system have remained elusive. We now describe the deduced primary structure of a sodium channel, peripheral nerve type 1 (PN1), which is expressed at high levels throughout the peripheral nervous system and is targeted to nerve terminals of cultured dorsal root ganglion neurons. Studies using cultured PC12 cells indicate that both expression and targeting of PN1 is induced by treatment of the cells with nerve growth factor. The preferential localization suggests that the PN1 sodium channel plays a specific role in nerve excitability.

Comparative distribution of misonidazole and its amine metabolite in female Swiss Webster mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Born, J.L.; Hadley, W.M.

1985-06-01

The distribution of misonidazole and its terminal reduction product 1-(2-amino-1-imidazolyl)-3-methoxy-2-propanol (misoamine) were compared in female Swiss Webster mice to determine if either misonidazole or misoamine is distributed to peripheral nerves. Female Swiss Webster mice received a 100 mg/kg (5 ..mu..Ci/..mu..mole) i.p. dose of either /sup 3/H-misonidazole or /sup 3/H-miso-amine and the distribution of radioactivity was determined in various tissues including sciatic nerves and other myelinated nerves. Misonidazole produced higher initial tissue concentrations of radioactivity than did miso-amine. The relative tissue concentrations of radioactivity produced by misonidazole or miso-amine were similar, although not identical, 48 hours after administration of the drugs.more » Both sciatic and other myelinated nerves were found to retain radioactivity following the administration of either misonidazole or miso-amine.« less

Polyamine FTX-3.3 and polyamine amide sFTX-3.3 inhibit presynaptic calcium currents and acetylcholine release at mouse motor nerve terminals.

PubMed

Fatehi, M; Rowan, E G; Harvey, A L; Moya, E; Blagbrough, I S

1997-02-01

FTX-3.3 is the proposed structure of a calcium-channel blocking toxin that has been isolated from the funnel web spider (Agelenopsis aperta). The effects of FTX-3.3 and one of its analogues, sFTX-3.3, on acetylcholine release, on presynaptic currents at mouse motor nerve terminals and on whole-cell sodium currents in SK.N.SH cells (a human neuroblastoma cell line) have been studied. FTX-3.3 (10-30 microM) and sFTX-3.3 (100-300 microM) reversibly reduced release of acetylcholine by approximately 70-90% and 40-60%, respectively. FTX-3.3 (10 microM) blocked the fast component of presynaptic calcium currents by approximately 60%. sFTX-3.3 (100 microM) reduced the duration of the slow component of presynaptic calcium currents by about 50% of the control and also reduced presynaptic sodium current by approximately 20% of the control. sFTX-3.3 (100 microM) reduced whole-cell sodium current recorded from SK.N.SH cells by approximately 15%, whereas FTX-3.3, even at 200 microM, did not affect this current. Since the only difference in chemical structures of these toxins is that sFTX-3.3 has an amide function which is absent in FTX-3.3, the amide function may be responsible for the reduced potency and selectivity of sFTX-3.3. This study also provides further support for the existence of P-type calcium channels at mouse motor nerve terminals.

Strontium, barium, and manganese metabolism in isolated presynaptic nerve terminals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rasgado-Flores, H.; Sanchez-Armass, S.; Blaustein, M.P.

1987-06-01

To gain insight into the mechanisms by which the divalent cations Sr, Ba, and Mn affect neurotransmitter release from presynaptic nerve terminals, the authors examined the sequestration of these cations, ion comparison to Ca, by mitochondrial and nonmitochondrial organelles and the extrusion of these cations from isolated nerve terminals. Sequestration was studied in synaptosomes made leaky to small ions by treatment with saponin; efflux was examined in intact synaptosomes that were preloaded with the divalent cations by incubation in depolarizing (K rich) media. The selectivity sequence for ATP-dependent mitochondrial uptake that they observed was Mn>>Ca>Sr>>Ba, whereas that for the SERmore » was Ca greater than or equal to Mn>Sr>>Ba. When synaptosomes that were preloaded with divalent cations were incubated in Na- and Ca-free media, there was little efflux of /sup 45/Ca, /sup 133/Ba, /sup 85/Sr, or /sup 54/Mn. When the incubation was carried out in media containing Na without Ca, there was substantial stimulation of Ca and Sr efflux, but only slight stimulation of Ba or Mn efflux. In Na-free media, the addition of 1 mM Ca promoted the efflux of all four divalent cations, probably via Ca-divalent cation exchange. In summary, the sequestration and extrusion data suggest that, with equal loads, Mn will be buffered to the greatest extent, whereas Ba will be least well buffered. These results may help to explain why Mn has a very long-lasting effect on transmitter release, while the effect of Sr is much briefer.« less

Myosin Va Plays a Role in Nitrergic Smooth Muscle Relaxation in Gastric Fundus and Corpora Cavernosa of Penis

PubMed Central

Carew, Josephine A.; Goyal, Raj K.; Sullivan, Maryrose P.

2014-01-01

The intracellular motor protein myosin Va is involved in nitrergic neurotransmission possibly by trafficking of neuronal nitric oxide synthase (nNOS) within the nerve terminals. In this study, we examined the role of myosin Va in the stomach and penis, proto-typical smooth muscle organs in which nitric oxide (NO) mediated relaxation is critical for function. We used confocal microscopy and co-immunoprecipitation of tissue from the gastric fundus (GF) and penile corpus cavernosum (CCP) to localize myosin Va with nNOS and demonstrate their molecular interaction. We utilized in vitro mechanical studies to test whether smooth muscle relaxations during nitrergic neuromuscular neurotransmission is altered in DBA (dilute, brown, non-agouti) mice which lack functional myosin Va. Myosin Va was localized in nNOS-positive nerve terminals and was co-immunoprecipitated with nNOS in both GF and CCP. In comparison to C57BL/6J wild type (WT) mice, electrical field stimulation (EFS) of precontracted smooth muscles of GF and CCP from DBA animals showed significant impairment of nitrergic relaxation. An NO donor, Sodium nitroprusside (SNP), caused comparable levels of relaxation in smooth muscles of WT and DBA mice. These normal postjunctional responses to SNP in DBA tissues suggest that impairment of smooth muscle relaxation resulted from inhibition of NO synthesis in prejunctional nerve terminals. Our results suggest that normal physiological processes of relaxation of gastric and cavernosal smooth muscles that facilitate food accommodation and penile erection, respectively, may be disrupted under conditions of myosin Va deficiency, resulting in complications like gastroparesis and erectile dysfunction. PMID:24516539

Distance between intramuscular nerve and artery in the extraocular muscles: a preliminary immunohistochemical study using elderly human cadavers.

PubMed

Kitamura, Kei; Cho, Kwang Ho; Jang, Hyung Suk; Murakami, Gen; Yamamoto, Masahito; Abe, Shin-Ichi

2017-01-01

Extraocular muscles are quite different from skeletal muscles in muscle fiber type and nerve supply; the small motor unit may be the most well known. As the first step to understanding the nerve-artery relationship, in this study we measured the distance from the arteriole (25-50 μm in thickness) to the nerve terminal twigs in extraocular muscles. With the aid of immunohistochemistry for nerves and arteries, we examined the arteriole-nerve distance at 10-15 sites in each of 68 extraocular muscles obtained from ten elderly cadavers. The oblique sections were nearly tangential to the muscle plate and included both global and orbital aspects of the muscle. In all muscles, the nerve twigs usually took a course parallel to muscle fibers, in contrast to most arterioles that crossed muscles. Possibly due to polyinnervation, an intramuscular nerve plexus was evident in four rectus and two oblique muscles. The arteriole-nerve distance usually ranged from 300 to 400 μm. However, individual differences were more than two times greater in each of seven muscles. Moreover, in each muscle the difference between sites sometimes reached 1 mm or more. The distance was generally shorter in the rectus and oblique muscles than in the levator palpebrae muscle, which reached statistical significance (p < 0.05). The differences in arteriole-nerve distances between sites within each muscle, between muscles, and between individuals might lead to an individual biological rhythm of fatigue in oculomotor performance.

Harmful impact on presynaptic glutamate and GABA transport by carbon dots synthesized from sulfur-containing carbohydrate precursor.

PubMed

Borisova, Tatiana; Dekaliuk, Mariia; Pozdnyakova, Natalia; Pastukhov, Artem; Dudarenko, Marina; Borysov, Arsenii; Vari, Sandor G; Demchenko, Alexander P

2017-07-01

Carbon nanoparticles that may be potent air pollutants with adverse effects on human health often contain heteroatoms including sulfur. In order to study in detail their effects on different physiological and biochemical processes, artificially produced carbon dots (CDs) with well-controlled composition that allows fluorescence detection may be of great use. Having been prepared from different types of organic precursors, CDs expose different atoms at their surface suggesting a broad variation of functional groups. Recently, we demonstrated neurotoxic properties of CDs synthesized from the amino acid β-alanine, and it is of importance to analyze whether CDs obtained from different precursors and particularly those exposing sulfur atoms induce similar neurotoxic effects. This study focused on synthesis of CDs from the sulfur-containing precursor thiourea-CDs (TU-CDs) with a size less than 10 nm, their characterization, and neuroactivity assessment. Neuroactive properties of TU-CDs were analyzed based on their effects on the key characteristics of glutamatergic and γ-aminobutyric acid (GABA) neurotransmission in isolated rat brain nerve terminals. It was observed that TU-CDs (0.5-1.0 mg/ml) attenuated the initial velocity of Na + -dependent transporter-mediated uptake and accumulation of L-[ 14 C]glutamate and [ 3 H]GABA by nerve terminals in a dose-dependent manner and increased the ambient level of the neurotransmitters. Starting from the concentration of 0.2 mg/ml, TU-CDs evoked a gradual dose-dependent depolarization of the plasma membrane of nerve terminals measured with the cationic potentiometric dye rhodamine 6G. Within the concentration range of 0.1-0.5 mg/ml, TU-CDs caused an "unphysiological" step-like increase in fluorescence intensity of the рН-sensitive fluorescent dye acridine orange accumulated by synaptic vesicles. Therefore, despite different surface properties and fluorescent features of CDs prepared from different starting materials (thiourea and β-alanine), their principal neurotoxic effects are analogous but displayed at a different level of efficiency. Sulfur-containing TU-CDs exhibit lower effects (by ~30%) on glutamate and GABA transport in the nerve terminals in comparison with sulfur-free β-alanine CDs. Our results suggest considering that an uncontrolled presence of carbon-containing particulate matter in the human environment may pose a toxicity risk for the central nervous system.

Serotonin neurons in the dorsal raphe mediate the anticataplectic action of orexin neurons by reducing amygdala activity.

PubMed

Hasegawa, Emi; Maejima, Takashi; Yoshida, Takayuki; Masseck, Olivia A; Herlitze, Stefan; Yoshioka, Mitsuhiro; Sakurai, Takeshi; Mieda, Michihiro

2017-04-25

Narcolepsy is a sleep disorder caused by the loss of orexin (hypocretin)-producing neurons and marked by excessive daytime sleepiness and a sudden weakening of muscle tone, or cataplexy, often triggered by strong emotions. In a mouse model for narcolepsy, we previously demonstrated that serotonin neurons of the dorsal raphe nucleus (DRN) mediate the suppression of cataplexy-like episodes (CLEs) by orexin neurons. Using an optogenetic tool, in this paper we show that the acute activation of DRN serotonin neuron terminals in the amygdala, but not in nuclei involved in regulating rapid eye-movement sleep and atonia, suppressed CLEs. Not only did stimulating serotonin nerve terminals reduce amygdala activity, but the chemogenetic inhibition of the amygdala using designer receptors exclusively activated by designer drugs also drastically decreased CLEs, whereas chemogenetic activation increased them. Moreover, the optogenetic inhibition of serotonin nerve terminals in the amygdala blocked the anticataplectic effects of orexin signaling in DRN serotonin neurons. Taken together, the results suggest that DRN serotonin neurons, as a downstream target of orexin neurons, inhibit cataplexy by reducing the activity of amygdala as a center for emotional processing.

Serotonin neurons in the dorsal raphe mediate the anticataplectic action of orexin neurons by reducing amygdala activity

PubMed Central

Hasegawa, Emi; Maejima, Takashi; Yoshida, Takayuki; Herlitze, Stefan; Yoshioka, Mitsuhiro; Sakurai, Takeshi; Mieda, Michihiro

2017-01-01

Narcolepsy is a sleep disorder caused by the loss of orexin (hypocretin)-producing neurons and marked by excessive daytime sleepiness and a sudden weakening of muscle tone, or cataplexy, often triggered by strong emotions. In a mouse model for narcolepsy, we previously demonstrated that serotonin neurons of the dorsal raphe nucleus (DRN) mediate the suppression of cataplexy-like episodes (CLEs) by orexin neurons. Using an optogenetic tool, in this paper we show that the acute activation of DRN serotonin neuron terminals in the amygdala, but not in nuclei involved in regulating rapid eye-movement sleep and atonia, suppressed CLEs. Not only did stimulating serotonin nerve terminals reduce amygdala activity, but the chemogenetic inhibition of the amygdala using designer receptors exclusively activated by designer drugs also drastically decreased CLEs, whereas chemogenetic activation increased them. Moreover, the optogenetic inhibition of serotonin nerve terminals in the amygdala blocked the anticataplectic effects of orexin signaling in DRN serotonin neurons. Taken together, the results suggest that DRN serotonin neurons, as a downstream target of orexin neurons, inhibit cataplexy by reducing the activity of amygdala as a center for emotional processing. PMID:28396432

Synaptic Vesicle Mobility and Presynaptic F-Actin Are Disrupted in a N-ethylmaleimide–sensitive Factor Allele of Drosophila

PubMed Central

Nunes, Paula; Haines, Nicola; Kuppuswamy, Venkat; Fleet, David J.

2006-01-01

N-ethylmaleimide sensitive factor (NSF) can dissociate the soluble NSF attachment receptor (SNARE) complex, but NSF also participates in other intracellular trafficking functions by virtue of SNARE-independent activity. Drosophila that express a neural transgene encoding a dominant-negative form of NSF2 show an 80% reduction in the size of releasable synaptic vesicle pool, but no change in the number of vesicles in nerve terminal boutons. Here we tested the hypothesis that vesicles in the NSF2 mutant terminal are less mobile. Using a combination of genetics, pharmacology, and imaging we find a substantial reduction in vesicle mobility within the nerve terminal boutons of Drosophila NSF2 mutant larvae. Subsequent analysis revealed a decrease of filamentous actin in both NSF2 dominant-negative and loss-of-function mutants. Lastly, actin-filament disrupting drugs also decrease vesicle movement. We conclude that a factor contributing to the NSF mutant phenotype is a reduction in vesicle mobility, which is associated with decreased presynaptic F-actin. Our data are consistent with a model in which actin filaments promote vesicle mobility and suggest that NSF participates in establishing or maintaining this population of actin. PMID:16914524

An immunohistochemical screening of neurochemical markers in fungiform papillae and taste buds of the anterior rat tongue.

PubMed

Astbäck, J; Arvidson, K; Johansson, O

1997-02-01

The occurrence and distribution of several neurochemical markers were investigated. Numerous nerve fibres were shown, using antibodies to protein gene product (PGP) 9.5, neurone-specific enolase, calcitonin gene-related peptide (CGRP), substance P. neurokinin A or protein S-100. The presence of vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine amide (PHI), neuropeptide tyrosine, dopamine-beta-hydroxylase (DBH), cholecystokinin/gastrin, glutamate and galanin was more scarce. Nerve fibres containing these above-mentioned markers were found at several locations, i.e. in the epithelium, connective tissue, and around blood vessels. In the taste buds, numerous PGP 9.5, neurone-specific enolase-, CGRP-, substance P-, neurokinin A- and protein S-100-containing structures were found, but few VIP and galanin ones. No immunoreactivity was found with antibodies against somatostatin, bombesin, enkephalin or dynorphin. These findings extend knowledge about the general as well as the neurochemical messenger-based innervation of rat fungiform papillae, forming a firm basis for future functional investigations of normal, experimental and also clinical materials.

Invertebrate Specific D1-like Dopamine Receptor in Control of Salivary Glands in the Black-Legged Tick Ixodes scapularis

PubMed Central

Šimo, Ladislav; Koči, Juraj; Kim, Donghun; Park, Yoonseong

2014-01-01

The control of tick salivary secretion, which plays a crucial role in compromising the host immune system, involves complex neural mechanisms. Dopamine is known to be the most potent activator of salivary secretion, as a paracrine/autocrine factor. We describe the invertebrate specific D1-like dopamine receptor (InvD1L), which is highly expressed in tick salivary glands. The InvD1L phylogenic clade was found only in invertebrates, suggesting that this receptor was lost in the vertebrates during evolution. InvD1L expressed in CHO-K1 cells was activated by dopamine with a median effective dose (EC50) of 1.34 μM. Immunohistochemistry using the antibody raised against InvD1L revealed two different types of immunoreactivities: basally located axon terminals that are colocalized with myoinhibitory peptide (MIP) and SIFamide neuropeptides, and longer axon-like processes that are positive only for the InvD1L antibody and extended to the apical parts of the acini. Both structures were closely associated with the myoepithelial cell, as visualized by beta-tubulin antibody, lining the acinar lumen in a web-like fashion. Subcellular localizations of InvD1L in the salivary gland suggest that InvD1L modulates the neuronal activities including MIP/SIFamide varicosities, and leads the contraction of myoepithelial cells and/or of the acinar valve to control the efflux of the luminal content. Combining the previously described D1 receptor with its putative function for activating an influx of fluid through the epithelial cells of acini, we propose that complex control of the tick salivary glands is mediated through two different dopamine receptors, D1 and InvD1L, for different downstream responses of the acinar cells. PMID:24307522

Neuronal BDNF Signaling Is Necessary for the Effects of Treadmill Exercise on Synaptic Stripping of Axotomized Motoneurons

PubMed Central

Krakowiak, Joey; Liu, Caiyue; Papudesu, Chandana; Ward, P. Jillian; Wilhelm, Jennifer C.; English, Arthur W.

2015-01-01

The withdrawal of synaptic inputs from the somata and proximal dendrites of spinal motoneurons following peripheral nerve injury could contribute to poor functional recovery. Decreased availability of neurotrophins to afferent terminals on axotomized motoneurons has been implicated as one cause of the withdrawal. No reduction in contacts made by synaptic inputs immunoreactive to the vesicular glutamate transporter 1 and glutamic acid decarboxylase 67 is noted on axotomized motoneurons if modest treadmill exercise, which stimulates the production of neurotrophins by spinal motoneurons, is applied after nerve injury. In conditional, neuron-specific brain-derived neurotrophic factor (BDNF) knockout mice, a reduction in synaptic contacts onto motoneurons was noted in intact animals which was similar in magnitude to that observed after nerve transection in wild-type controls. No further reduction in coverage was found if nerves were cut in knockout mice. Two weeks of moderate daily treadmill exercise following nerve injury in these BDNF knockout mice did not affect synaptic inputs onto motoneurons. Treadmill exercise has a profound effect on synaptic inputs to motoneurons after peripheral nerve injury which requires BDNF production by those postsynaptic cells. PMID:25918648

Nitrergic nerves derived from the pterygopalatine ganglion innervate arteries irrigating the cerebrum but not the cerebellum and brain stem in monkeys.

PubMed

Ayajiki, Kazuhide; Kobuchi, Shuhei; Tawa, Masashi; Okamura, Tomio

2012-01-01

The functional roles of the nitrergic nerves innervating the monkey cerebral artery were evaluated in a tension-response study examining isolated arteries in vitro and cerebral angiography in vivo. Nicotine produced relaxation of arteries by stimulation of nerve terminals innervating isolated monkey arteries irrigating the cerebrum, cerebellum and brain stem. Relaxation of arteries induced by nicotine was abolished by treatment with N(G)-nitro-L-arginine, a nitric oxide synthase inhibitor, and was restored by addition of L-arginine. Cerebral angiography showed that electrical stimulation of the unilateral greater petrosal nerve, which connects to the pterygopalatine ganglion via the parasympathetic ganglion synapse, produced vasodilatation of the anterior, middle and posterior cerebral arteries in the stimulated side. However, stimulation failed to produce vasodilatation of the superior and anterior-inferior cerebellar arteries and the basilar artery in anesthetized monkeys. Therefore, nitrergic nerves derived from the pterygopalatine ganglion appear to regulate cerebral vasomotor function. In contrast, circulation in the cerebellum and brain stem might be regulated by nitrergic nerves originating not from the pterygopalatine ganglion, but rather from an unknown ganglion (or ganglia).

Interplay between mast cells, enterochromaffin cells, and sensory signaling in the aging human bowel.

PubMed

Yu, Y; Daly, D M; Adam, I J; Kitsanta, P; Hill, C J; Wild, J; Shorthouse, A; Grundy, D; Jiang, W

2016-10-01

Advanced age is associated with a reduction in clinical visceral pain perception. However, the underlying mechanisms remain largely unknown. Previous studies have suggested that an abnormal interplay between mast cells, enterochromaffin (EC) cells, and afferent nerves contribute to nociception in gastrointestinal disorders. The aim of this study was to investigate how aging affects afferent sensitivity and neuro-immune association in the human bowel. Mechanical and chemical sensitivity of human bowel afferents were examined by ex vivo afferent nerve recordings. Age-related changes in the density of mast cells, EC cells, sensory nerve terminals, and mast cell-nerve micro-anatomical association were investigated by histological and immune staining. Human afferents could be broadly classified into subpopulations displaying mechanical and chemical sensitivity, adaptation, chemo-sensitization, and recruitment. Interestingly human bowel afferent nerve sensitivity was attenuated with age. The density of substance P-immunoreactive (SP-IR) nerve varicosities was also reduced with age. In contrast, the density of ileal and colonic mucosal mast cells was increased with age, as was ileal EC cell number. An increased proportion of mast cells was found in close apposition to SP-IR nerves. Afferent sensitivity in human bowel was reduced with advancing age. Augmentation of mast cells and EC cell numbers and the mast cell-nerve association suggest a compensatory mechanism for sensory neurodegeneration. © 2016 The Authors. Neurogastroenterology & Motility Published by John Wiley & Sons Ltd.

Nerve growth factor reduces apoptotic cell death in rat facial motor neurons after facial nerve injury.

PubMed

Hui, Lian; Yuan, Jing; Ren, Zhong; Jiang, Xuejun

2015-01-01

To assess the effects of nerve growth factor (NGF) on motor neurons after induction of a facial nerve lesion, and to compare the effects of different routes of NGF injection on motor neuron survival. This study was carried out in the Department of Otolaryngology Head & Neck Surgery, China Medical University, Liaoning, China from October 2012 to March 2013. Male Wistar rats (n = 65) were randomly assigned into 4 groups: A) healthy controls; B) facial nerve lesion model + normal saline injection; C) facial nerve lesion model + NGF injection through the stylomastoid foramen; D) facial nerve lesion model + intraperitoneal injection of NGF. Apoptotic cell death was detected using the terminal deoxynucleotidyl transferase dUTP nick end-labeling assay. Expression of caspase-3 and p53 up-regulated modulator of apoptosis (PUMA) was determined by immunohistochemistry. Injection of NGF significantly reduced cell apoptosis, and also greatly decreased caspase-3 and PUMA expression in injured motor neurons. Group C exhibited better efficacy for preventing cellular apoptosis and decreasing caspase-3 and PUMA expression compared with group D (p<0.05). Our findings suggest that injections of NGF may prevent apoptosis of motor neurons by decreasing caspase-3 and PUMA expression after facial nerve injury in rats. The NGF injected through the stylomastoid foramen demonstrated better protective efficacy than when injected intraperitoneally.

Effects of serotonin 5-HT1A agonist in advanced Parkinson's disease.

PubMed

Bara-Jimenez, William; Bibbiani, Francesco; Morris, Michael J; Dimitrova, Tzvetelina; Sherzai, Abdullah; Mouradian, Maral M; Chase, Thomas N

2005-08-01

Intermittent stimulation of striatal dopaminergic receptors seems to contribute to motor dysfunction in advanced Parkinson's disease (PD). With severe dopaminergic denervation, exogenous levodopa is largely decarboxylated to dopamine in serotonergic terminals. If 5-HT1A autoreceptors regulate dopamine as well as serotonin release, in parkinsonian patients inhibition of striatal serotonergic neuron firing might help maintain more physiological intrasynaptic dopamine concentrations and thus ameliorate motor fluctuations and dyskinesias. To evaluate this hypothesis, effects of a selective 5-HT1A agonist, sarizotan, given orally at 2 and 5 mg twice daily to 18 relatively advanced parkinsonian patients, were compared with baseline placebo function during a 3-week, double-blind, placebo-controlled, proof-of-concept study. Sarizotan alone or with intravenous levodopa had no effect on parkinsonian severity. But at safe and tolerable doses, sarizotan coadministration reduced levodopa-induced dyskinesias and prolonged its antiparkinsonian response (P < or = 0.05). Under the conditions of this study, our findings suggest that 5-HT1A receptor stimulation in levodopa-treated parkinsonian patients can modulate striatal dopaminergic function and that 5-HT1A agonists may be useful as levodopa adjuvants in the treatment of PD. Copyright 2005 Movement Disorder Society

Decreased catecholamine secretion from the adrenal medullae of chronically diabetic BB-Wistar rats

NASA Technical Reports Server (NTRS)

Wilke, R. A.; Riley, D. A.; Lelkes, P. I.; Hillard, C. J.

1993-01-01

Many humans with IDDM eventually lose the capacity to secrete epinephrine from their adrenal medullae. The mechanism for this pathological change is unknown. We hypothesized that this abnormality is attributable to neuropathic changes in the greater splanchnic nerves or in the chromaffin cells that they innervate. To study this hypothesis, we isolated rat adrenal glands, perfused them ex vivo, and measured the epinephrine content of the perfusate under various conditions of stimulation. We used transmural electrical stimulation (20-80 V, at 10 Hz) to induce epinephrine secretion indirectly by selectively activating residual splanchnic nerve terminals within the isolated glands. Under these conditions, epinephrine secretion was severely attenuated in glands from female BB-Wistar rats with diabetes of 4 mo duration compared with their age-matched, nondiabetic controls. These perfused diabetic adrenal medullae also demonstrated decreased catecholamine release in response to direct chromaffin cell depolarization with 20 mM K+, evidence that a functional alteration exists within the chromaffin cells themselves. Nonetheless, total catecholamine content of adrenal medullae from these diabetic rats was not significantly different from controls, indicating that the secretory defect was not simply attributable to a difference in the amount of catecholamines stored and available for release. Herein, we also provide histological evidence of degenerative changes within the cholinergic nerve terminals that innervate these glands.

Memantine Inhibits α3β2-nAChRs-Mediated Nitrergic Neurogenic Vasodilation in Porcine Basilar Arteries

PubMed Central

Wu, Celeste Yin-Chieh; Chen, Po-Yi; Chen, Mei-Fang; Kuo, Jon-Son; Lee, Tony Jer-Fu

2012-01-01

Memantine, an NMDA receptor antagonist used for treatment of Alzheimer’s disease (AD), is known to block the nicotinic acetylcholine receptors (nAChRs) in the central nervous system (CNS). In the present study, we examined by wire myography if memantine inhibited α3β2-nAChRs located on cerebral perivascular sympathetic nerve terminals originating in the superior cervical ganglion (SCG), thus, leading to inhibition of nicotine-induced nitrergic neurogenic dilation of isolated porcine basilar arteries. Memantine concentration-dependently blocked nicotine-induced neurogenic dilation of endothelium-denuded basilar arteries without affecting that induced by transmural nerve stimulation, sodium nitroprusside, or isoproterenol. Furthermore, memantine significantly inhibited nicotine-elicited inward currents in Xenopous oocytes expressing α3β2-, α7- or α4β2-nAChR, and nicotine-induced calcium influx in cultured rat SCG neurons. These results suggest that memantine is a non-specific antagonist for nAChR. By directly inhibiting α3β2-nAChRs located on the sympathetic nerve terminals, memantine blocks nicotine-induced neurogenic vasodilation of the porcine basilar arteries. This effect of memantine is expected to reduce the blood supply to the brain stem and possibly other brain regions, thus, decreasing its clinical efficacy in the treatment of Alzheimer’s disease. PMID:22792283

Effects of hyperglycemia on rat cavernous nerve axons: a functional and ultrastructural study.

PubMed

Zotova, Elena G; Schaumburg, Herbert H; Raine, Cedric S; Cannella, Barbara; Tar, Moses; Melman, Arnold; Arezzo, Joseph C

2008-10-01

The present study explored parallel changes in the physiology and structure of myelinated (Adelta) and unmyelinated (C) small diameter axons in the cavernous nerve of rats associated with streptozotocin-induced hyperglycemia. Damage to these axons is thought to play a key role in diabetic autonomic neuropathy and erectile dysfunction, but their pathophysiology has been poorly studied. Velocities in slow conducting fibers were measured by applying multiple unit procedures; histopathology was evaluated with both light and electron microscopy. To our knowledge, these are the initial studies of slow nerve conduction velocities in the distal segments of the cavernous nerve. We report that hyperglycemia is associated with a substantial reduction in the amplitude of the slow conducting response, as well as a slowing of velocities within this very slow range (< 2.5 m/s). Even with prolonged hyperglycemia (> 4 months), histopathological abnormalities were mild and limited to the distal segments of the cavernous nerve. Structural findings included dystrophic changes in nerve terminals, abnormal accumulations of glycogen granules in unmyelinated and preterminal axons, and necrosis of scattered smooth muscle fibers. The onset of slowing of velocity in the distal cavernous nerve occurred subsequent to slowing in somatic nerves in the same rats. The functional changes in the cavernous nerve anticipated and exceeded the axonal degeneration detected by morphology. The physiologic techniques outlined in these studies are feasible in most electrophysiologic laboratories and could substantially enhance our sensitivity to the onset and progression of small fiber diabetic neuropathy.

EFFECTS OF HYPERGLYCEMIA ON RAT CAVERNOUS NERVE AXONS: A FUNCTIONAL AND ULTRASTRUCTURAL STUDY

PubMed Central

Zotova, Elena G.; Schaumburg, Herbert H.; Raine, Cedric S.; Cannella, Barbara; Tar, Moses; Melman, Arnold; Arezzo, Joseph C.

2008-01-01

The present study explored parallel changes in the physiology and structure of myelinated (Aδ) and unmyelinated (C) small diameter axons in the cavernous nerve of rats associated with streptozotocin-induced hyperglycemia. Damage to these axons is thought to play a key role in diabetic autonomic neuropathy and erectile dysfunction, but their pathophysiology has been poorly studied. Velocities in slow conducting fibers were measured by applying multiple unit procedures; histopathology was evaluated with both light and electron microscopy. To our knowledge, these are the initial studies of slow nerve conduction velocities in the distal segments of the cavernous nerve. We report that hyperglycemia is associated with a substantial reduction in the amplitude of the slow conducting response, as well as a slowing of velocities within this very slow range (<2.5 m/sec). Even with prolonged hyperglycemia (> 4 months), histopathological abnormalities were mild and limited to the distal segments of the cavernous nerve. Structural findings included dystrophic changes in nerve terminals, abnormal accumulations of glycogen granules in unmyelinated and preterminal axons, and necrosis of scattered smooth muscle fibers. The onset of slowing of velocity in the distal cavernous nerve occurred subsequent to slowing in somatic nerves in the same rats. The functional changes in the cavernous nerve anticipated and exceeded the axonal degeneration detected by morphology. The physiologic techniques outlined in these studies are feasible in most electrophysiologic laboratories and could substantially enhance our sensitivity to the onset and progression of small fiber diabetic neuropathy. PMID:18687329

The Course of the Terminal Posterior Interosseous Nerve and Its Relationship with Wrist Arthroscopy Portals

PubMed Central

Pan, Yongwei; Hung, Leung-kim

2016-01-01

Purpose The terminal branches of the posterior interosseous nerve (PIN) are the main articular branch on the dorsal aspect of the wrist. Its relationship to dorsal wrist arthroscopic portals has not yet been elucidated. The purpose of this study was to quantitatively describe the anatomical relationships between the dorsal wrist arthroscopic portals and the PIN. Methods Dorsal wrist arthroscopic portals were established in 28 cadaver extremities, after which the limbs were dissected. Measurements were taken from the portals to the PIN. Results The PIN passed ulnar to the 3/4 portal with a mean distance of 4.8 mm (range: 1.2–12.0, standard deviation [SD] = 2.6). The PIN passed radial to the 4/5 portal with a mean interval of 9.0 mm (range: 3.8–12.7, SD = 2.3). The main trunk of PIN or its closest terminal branch was a mean of 7.2 mm (range: 0.0–13.2 mm, SD = 3.1) radial to the midcarpal radial (MCR) portal. In 2 of the 28 specimens, one terminal branch of PIN lay directly over this portal. The distance between the midcarpal ulnar (MCU) portal and the PIN or its closest terminal branch was only a mean of 1.6 mm (range: 0–6.4 mm, SD = 2.0). In 15 of the 28 specimens, the PIN lay directly over the MCU portal, or the portal was located between the terminal branches of PIN. Conclusion The MCU portal was the most precarious, due to the close proximity of PIN and its terminal branches. The 3/4 and MCR portals were also at risk, while the 4/5 portal was relatively safe for the PIN. PMID:27777824

Patterns of fast synaptic cholinergic activation of neurons in the celiac ganglia of cats.

PubMed

Niel, J P; Clerc, N; Jule, Y

1988-12-01

Fast nicotinic transmission was studied in vitro in neurons of isolated cat celiac ganglia. In the absence of nerve stimulation, neurons could be classified into three types: silent neurons, synaptically activated neurons, and spontaneously discharging neurons. In all three types, fast synaptic activation could be obtained in single neurons by stimulating with a single pulse both the splanchnic nerves or one of the peripheral nerves connected to the ganglia. During repetitive nerve stimulation, a gradual depression of the central and peripheral fast nicotinic activation occurred, which was not affected by phentolamine plus propranolol, domperidone, atropine, or naloxone. Repetitive nerve stimulation was followed by a long lasting discharge of excitatory postsynaptic potentials and action potentials that decreased gradually with time. This discharge, which was probably due to presynaptic or prejunctional facilitation of acetylcholine release from cholinergic terminals, was reduced by the application of phentolamine plus propranolol, domperidone, or atropine and increased with naloxone. The existence of the mechanisms described in this study reflects the complexity of the integrative processes at work in neurons of the cat celiac ganglia that involve fast synaptic cholinergic activation.

Anatomical Variability in the Termination of the Basilar Artery in the Human Cadaveric Brain.

PubMed

Gunnal, Sandhya; Farooqui, Mujeebuddin; Wabale, Rajendra

2015-01-01

The basilar artery (BA) is the prominent median vessel of the vertebrobasilar circulation and usually terminates into two posterior cerebral arteries forming the posterior angle of the Circle of Willis (CW). To tackle different variations of CW, basilar artery acts as a guideline for neuroradiologists and neurosurgeons. Basilar termination is the most frequent site of aneurysm. Abnormalities at the site of termination may compress the oculomotor nerve. Variations at the termination may complicate surgeries at the base of brain. The present study aims to add to the knowledge regarding the termination pattern of the BA. 170 BA terminations were studied. Morphological variations in the termination pattern were noted. Frequency of variations in termination patterns was recorded. Dimensions of BA were measured. Data were analyzed. Morphological variations in termination were seen in 17.64%. Bifurcation, Trifurcation, Quadrifurcation, Pentafurcation and Nonfurcation of BA was seen in 82.35%, 5.29%, 5.88%, 3.52% and 2.94% respectively. BA associated with aneurysm and Fenestration was seen in 3.52% and 1.17% respectively. Mean length and diameter of BA was 30.27 mm and 4.8 mm respectively. Awareness of these anatomical variations in termination patterns of BA is important in neurovascular procedures.

Hibernating myocardium results in partial sympathetic denervation and nerve sprouting.

PubMed

Fernandez, Stanley F; Ovchinnikov, Vladislav; Canty, John M; Fallavollita, James A

2013-01-15

Hibernating myocardium due to chronic repetitive ischemia is associated with regional sympathetic nerve dysfunction and spontaneous arrhythmic death in the absence of infarction. Although inhomogeneity in regional sympathetic innervation is an acknowledged substrate for sudden death, the mechanism(s) responsible for these abnormalities in viable, dysfunctional myocardium (i.e., neural stunning vs. sympathetic denervation) and their association with nerve sprouting are unknown. Accordingly, markers of sympathetic nerve function and nerve sprouting were assessed in subendocardial tissue collected from chronically instrumented pigs with hibernating myocardium (n = 18) as well as sham-instrumented controls (n = 7). Hibernating myocardium exhibited evidence of partial sympathetic denervation compared with the normally perfused region and sham controls, with corresponding regional reductions in tyrosine hydroxylase protein (-32%, P < 0.001), norepinephrine uptake transport protein (-25%, P = 0.01), and tissue norepinephrine content (-45%, P < 0.001). Partial denervation induced nerve sprouting with regional increases in nerve growth factor precursor protein (31%, P = 0.01) and growth associated protein-43 (38%, P < 0.05). All of the changes in sympathetic nerve markers were similar in animals that developed sudden death (n = 9) compared with electively terminated pigs with hibernating myocardium (n = 9). In conclusion, sympathetic nerve dysfunction in hibernating myocardium is most consistent with partial sympathetic denervation and is associated with regional nerve sprouting. The extent of sympathetic remodeling is similar in animals that develop sudden death compared with survivors; this suggests that sympathetic remodeling in hibernating myocardium is not an independent trigger for sudden death. Nevertheless, sympathetic remodeling likely contributes to electrical instability in combination with other factors.

Hibernating myocardium results in partial sympathetic denervation and nerve sprouting

PubMed Central

Fernandez, Stanley F.; Ovchinnikov, Vladislav; Canty, John M.

2013-01-01

Hibernating myocardium due to chronic repetitive ischemia is associated with regional sympathetic nerve dysfunction and spontaneous arrhythmic death in the absence of infarction. Although inhomogeneity in regional sympathetic innervation is an acknowledged substrate for sudden death, the mechanism(s) responsible for these abnormalities in viable, dysfunctional myocardium (i.e., neural stunning vs. sympathetic denervation) and their association with nerve sprouting are unknown. Accordingly, markers of sympathetic nerve function and nerve sprouting were assessed in subendocardial tissue collected from chronically instrumented pigs with hibernating myocardium (n = 18) as well as sham-instrumented controls (n = 7). Hibernating myocardium exhibited evidence of partial sympathetic denervation compared with the normally perfused region and sham controls, with corresponding regional reductions in tyrosine hydroxylase protein (−32%, P < 0.001), norepinephrine uptake transport protein (−25%, P = 0.01), and tissue norepinephrine content (−45%, P < 0.001). Partial denervation induced nerve sprouting with regional increases in nerve growth factor precursor protein (31%, P = 0.01) and growth associated protein-43 (38%, P < 0.05). All of the changes in sympathetic nerve markers were similar in animals that developed sudden death (n = 9) compared with electively terminated pigs with hibernating myocardium (n = 9). In conclusion, sympathetic nerve dysfunction in hibernating myocardium is most consistent with partial sympathetic denervation and is associated with regional nerve sprouting. The extent of sympathetic remodeling is similar in animals that develop sudden death compared with survivors; this suggests that sympathetic remodeling in hibernating myocardium is not an independent trigger for sudden death. Nevertheless, sympathetic remodeling likely contributes to electrical instability in combination with other factors. PMID:23125211

Autoregulation of Neuromuscular Transmission by Nerve Terminals.

DTIC Science & Technology

1985-09-01

prejunctional cholinoceptor. Nicotine, carbachol , ACh and suberyl- dicholine have been used as agonists. 1 , 2 Neostigmine (NEO) and related acetylcholinesterase...bromide, aminopyridine, aBGT, DFP, nicotine, carnitine, dTC, physostigmine and carbachol . A one-way analysis of variance of these data indicated a lack

Progressive nigrostriatal terminal dysfunction and degeneration in the engrailed1 heterozygous mouse model of Parkinson's disease.

PubMed

Nordströma, Ulrika; Beauvais, Geneviève; Ghosh, Anamitra; Pulikkaparambil Sasidharan, Baby Chakrapani; Lundblad, Martin; Fuchs, Julia; Joshi, Rajiv L; Lipton, Jack W; Roholt, Andrew; Medicetty, Satish; Feinstein, Timothy N; Steiner, Jennifer A; Escobar Galvis, Martha L; Prochiantz, Alain; Brundin, Patrik

2015-01-01

Current research on Parkinson's disease (PD) pathogenesis requires relevant animal models that mimic the gradual and progressive development of neuronal dysfunction and degeneration that characterizes the disease. Polymorphisms in engrailed 1 (En1), a homeobox transcription factor that is crucial for both the development and survival of mesencephalic dopaminergic neurons, are associated with sporadic PD. This suggests that En1 mutant mice might be a promising candidate PD model. Indeed, a mouse that lacks one En1 allele exhibits decreased mitochondrial complex I activity and progressive midbrain dopamine neuron degeneration in adulthood, both features associated with PD. We aimed to further characterize the disease-like phenotype of these En1(+/-) mice with a focus on early neurodegenerative changes that can be utilized to score efficacy of future disease modifying studies. We observed early terminal defects in the dopaminergic nigrostriatal pathway in En1(+/-) mice. Several weeks before a significant loss of dopaminergic neurons in the substantia nigra could be detected, we found that striatal terminals expressing high levels of dopaminergic neuron markers TH, VMAT2, and DAT were dystrophic and swollen. Using transmission electron microscopy, we identified electron dense bodies consistent with abnormal autophagic vacuoles in these terminal swellings. In line with these findings, we detected an up-regulation of the mTOR pathway, concurrent with a downregulation of the autophagic marker LC3B, in ventral midbrain and nigral dopaminergic neurons of the En1(+/-) mice. This supports the notion that autophagic protein degradation is reduced in the absence of one En1 allele. We imaged the nigrostriatal pathway using the CLARITY technique and observed many fragmented axons in the medial forebrain bundle of the En1(+/-) mice, consistent with axonal maintenance failure. Using in vivo electrochemistry, we found that nigrostriatal terminals in the dorsal striatum were severely deficient in dopamine release and reuptake. Our findings support a progressive retrograde degeneration of En1(+/-) nigrostriatal neurons, akin to what is suggested to occur in PD. We suggest that using the En1(+/-) mice as a model will provide further key insights into PD pathogenesis, and propose that axon terminal integrity and function can be utilized to estimate dopaminergic neuron health and efficacy of experimental PD therapies. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Structure activity relationship of synaptic and junctional neurotransmission.

PubMed

Goyal, Raj K; Chaudhury, Arun

2013-06-01

Chemical neurotransmission may include transmission to local or remote sites. Locally, contact between 'bare' portions of the bulbous nerve terminal termed a varicosity and the effector cell may be in the form of either synapse or non-synaptic contact. Traditionally, all local transmissions between nerves and effector cells are considered synaptic in nature. This is particularly true for communication between neurons. However, communication between nerves and other effectors such as smooth muscles has been described as nonsynaptic or junctional in nature. Nonsynaptic neurotransmission is now also increasingly recognized in the CNS. This review focuses on the relationship between structure and function that orchestrate synaptic and junctional neurotransmissions. A synapse is a specialized focal contact between the presynaptic active zone capable of ultrafast release of soluble transmitters and the postsynaptic density that cluster ionotropic receptors. The presynaptic and the postsynaptic areas are separated by the 'closed' synaptic cavity. The physiological hallmark of the synapse is ultrafast postsynaptic potentials lasting milliseconds. In contrast, junctions are juxtapositions of nerve terminals and the effector cells without clear synaptic specializations and the junctional space is 'open' to the extracellular space. Based on the nature of the transmitters, postjunctional receptors and their separation from the release sites, the junctions can be divided into 'close' and 'wide' junctions. Functionally, the 'close' and the 'wide' junctions can be distinguished by postjunctional potentials lasting ~1s and tens of seconds, respectively. Both synaptic and junctional communications are common between neurons; however, junctional transmission is the rule at many neuro-non-neural effectors. Published by Elsevier B.V.

Structure activity relationship of synaptic and junctional neurotransmission

PubMed Central

Goyal, Raj K; Chaudhury, Arun

2013-01-01

Chemical neurotransmission may include transmission to local or remote sites. Locally, contact between ‘bare’ portions of the bulbous nerve terminal termed a varicosity and the effector cell may be in the form of either synapse or non-synaptic contact. Traditionally, all local transmissions between nerves and effector cells are considered synaptic in nature. This is particularly true for communication between neurons. However, communication between nerves and other effectors such as smooth muscles has been described as nonsynaptic or junctional in nature. Nonsynaptic neurotransmission is now also increasing recognized in the CNS. This review focuses on the relationship between structure and function that orchestrate synaptic and junctional neurotransmissions. A synapse is a specialized focal contact between the presynaptic active zone capable for ultrafast release of soluble transmitters and the postsynaptic density that cluster ionotropic receptors. The presynaptic and the postsynaptic areas are separated by the ‘closed’ synaptic cavity. The physiological hallmark of the synapse is ultrafast postsynaptic potentials lasting in milliseconds. In contrast, junctions are juxtapositions of nerve terminals and the effector cells without clear synaptic specializations and the junctional space is ‘open’ to the extracellular space. Based on the nature of the transmitters, postjunctional receptors and their separation from the release sites, the junctions can be divided into ‘close’ and ‘wide’ junctions. Functionally, the ‘close’ and the ‘wide’ junctions can be distinguished by postjunctional potentials lasting ~1 second and 10s of seconds, respectively. Both synaptic and junctional communications are common between neurons; however, junctional transmission is the rule at many neuro-non-neural effectors. PMID:23535140

Alpha-Synuclein Pathology in Sensory Nerve Terminals of the Upper Aerodigestive Tract of Parkinson’s Disease Patients

PubMed Central

Mu, Liancai; Chen, Jingming; Sobotka, Stanislaw; Nyirenda, Themba; Benson, Brian; Gupta, Fiona; Sanders, Ira; Adler, Charles H.; Caviness, John N.; Shill, Holly A.; Sabbagh, Marwan; Samanta, Johan E.; Sue, Lucia I.; Beach, Thomas G.

2015-01-01

Dysphagia is common in Parkinson’s disease (PD) and causes significant morbidity and mortality. PD dysphagia has usually been explained as dysfunction of central motor control, much like other motor symptoms that are characteristic of the disease. However, PD dysphagia does not correlate with severity of motor symptoms nor does it respond to motor therapies. It is known that PD patients have sensory deficits in the pharynx, and that impaired sensation may contribute to dysphagia. However, the underlying cause of the pharyngeal sensory deficits in PD is not known. We hypothesized that PD dysphagia with sensory deficits may be due to degeneration of the sensory nerve terminals in the upper aerodigestive tract (UAT). We have previously shown that Lewy-type synucleinopathy (LTS) is present in the main pharyngeal sensory nerves of PD patients, but not in controls. In this study, the sensory terminals in UAT mucosa were studied to discern the presence and distribution of LTS. Whole-mount specimens (tongue-pharynx-larynx-upper esophagus) were obtained from 10 deceased human subjects with clinically diagnosed and neuropathologically confirmed PD (five with dysphagia and five without) and four age-matched healthy controls. Samples were taken from six sites and immunostained for phosphorylated α-synuclein (PAS). The results showed the presence of PAS-immunoreactive (PAS-ir) axons in all the PD subjects and in none of the controls. Notably, PD patients with dysphagia had more PAS-ir axons in the regions that are critical for initiating the swallowing reflex. These findings suggest that Lewy pathology affects mucosal sensory axons in specific regions of the UAT and may be related to PD dysphagia. PMID:26041249

Alpha-Synuclein Pathology in Sensory Nerve Terminals of the Upper Aerodigestive Tract of Parkinson's Disease Patients.

PubMed

Mu, Liancai; Chen, Jingming; Sobotka, Stanislaw; Nyirenda, Themba; Benson, Brian; Gupta, Fiona; Sanders, Ira; Adler, Charles H; Caviness, John N; Shill, Holly A; Sabbagh, Marwan; Samanta, Johan E; Sue, Lucia I; Beach, Thomas G

2015-08-01

Dysphagia is common in Parkinson's disease (PD) and causes significant morbidity and mortality. PD dysphagia has usually been explained as dysfunction of central motor control, much like other motor symptoms that are characteristic of the disease. However, PD dysphagia does not correlate with severity of motor symptoms nor does it respond to motor therapies. It is known that PD patients have sensory deficits in the pharynx, and that impaired sensation may contribute to dysphagia. However, the underlying cause of the pharyngeal sensory deficits in PD is not known. We hypothesized that PD dysphagia with sensory deficits may be due to degeneration of the sensory nerve terminals in the upper aerodigestive tract (UAT). We have previously shown that Lewy-type synucleinopathy (LTS) is present in the main pharyngeal sensory nerves of PD patients, but not in controls. In this study, the sensory terminals in UAT mucosa were studied to discern the presence and distribution of LTS. Whole-mount specimens (tongue-pharynx-larynx-upper esophagus) were obtained from 10 deceased human subjects with clinically diagnosed and neuropathologically confirmed PD (five with dysphagia and five without) and four age-matched healthy controls. Samples were taken from six sites and immunostained for phosphorylated α-synuclein (PAS). The results showed the presence of PAS-immunoreactive (PAS-ir) axons in all the PD subjects and in none of the controls. Notably, PD patients with dysphagia had more PAS-ir axons in the regions that are critical for initiating the swallowing reflex. These findings suggest that Lewy pathology affects mucosal sensory axons in specific regions of the UAT and may be related to PD dysphagia.

Nucleus of the solitary tract in the C57BL/6J mouse: Subnuclear parcellation, chorda tympani nerve projections, and brainstem connections.

PubMed

Ganchrow, Donald; Ganchrow, Judith R; Cicchini, Vanessa; Bartel, Dianna L; Kaufman, Daniel; Girard, David; Whitehead, Mark C

2014-05-01

The nucleus of the solitary tract (NST) processes gustatory and related somatosensory information rostrally and general viscerosensory information caudally. To compare its connections with those of other rodents, this study in the C57BL/6J mouse provides a subnuclear cytoarchitectonic parcellation (Nissl stain) of the NST into rostral, intermediate, and caudal divisions. Subnuclei are further characterized by NADPH staining and P2X2 immunoreactivity (IR). Cholera toxin subunit B (CTb) labeling revealed those NST subnuclei receiving chorda tympani nerve (CT) afferents, those connecting with the parabrachial nucleus (PBN) and reticular formation (RF), and those interconnecting NST subnuclei. CT terminals are densest in the rostral central (RC) and medial (M) subnuclei; less dense in the rostral lateral (RL) subnucleus; and sparse in the ventral (V), ventral lateral (VL), and central lateral (CL) subnuclei. CTb injection into the PBN retrogradely labels cells in the aforementioned subnuclei; RC and M providing the largest source of PBN projection neurons. Pontine efferent axons terminate mainly in V and rostral medial (RM) subnuclei. CTb injection into the medullary RF labels cells and axonal endings predominantly in V at rostral and intermediate NST levels. Small CTb injections within the NST label extensive projections from the rostral division to caudal subnuclei. Projections from the caudal division primarily interconnect subnuclei confined to the caudal division of the NST; they also connect with the area postrema. P2X2 -IR identifies probable vagal nerve terminals in the central (Ce) subnucleus in the intermediate/caudal NST. Ce also shows intense NADPH staining and does not project to the PBN. Copyright © 2013 Wiley Periodicals, Inc.

Nucleus of the solitary tract in the C57BL/6J mouse: Subnuclear parcellation, chorda tympani nerve projections, and brainstem connections

PubMed Central

Ganchrow, Donald; Ganchrow, Judith R; Cicchini, Vanessa; Bartel, Dianna L; Kaufman, Daniel; Girard, David; Whitehead, Mark C

2013-01-01

The nucleus of the solitary tract (NST) processes gustatory and related somatosensory information rostrally and general viscerosensory information caudally. To compare its connections with those of other rodents, this study in the C57BL/6J mouse provides a subnuclear cytoarchitectonic parcellation (Nissl stain) of the NST into rostral, intermediate, and caudal divisions. Subnuclei are further characterized by NADPH staining and P2X2 immunoreactivity (IR). Cholera toxin subunit B (CTb) labeling revealed those NST subnuclei receiving chorda tympani nerve (CT) afferents, those connecting with the parabrachial nucleus (PBN) and reticular formation (RF), and those interconnecting NST subnuclei. CT terminals are densest in the rostral central (RC) and medial (M) subnuclei; less dense in the rostral lateral (RL) subnucleus; and sparse in the ventral (V), ventral lateral (VL), and central lateral (CL) subnuclei. CTb injection into the PBN retrogradely labels cells in the aforementioned subnuclei; RC and M providing the largest source of PBN projection neurons. Pontine efferent axons terminate mainly in V and rostral medial (RM) subnuclei. CTb injection into the medullary RF labels cells and axonal endings predominantly in V at rostral and intermediate NST levels. Small CTb injections within the NST label extensive projections from the rostral division to caudal subnuclei. Projections from the caudal division primarily interconnect subnuclei confined to the caudal division of the NST; they also connect with the area postrema. P2X2-IR identifies probable vagal nerve terminals in the central (Ce) subnucleus in the intermediate/caudal NST. Ce also shows intense NADPH staining and does not project to the PBN. J. Comp. Neurol. 522:1565–1596, 2014. PMID:24151133

Visualization of endosome dynamics in living nerve terminals with four-dimensional fluorescence imaging.

PubMed

Stewart, Richard S; Kiss, Ilona M; Wilkinson, Robert S

2014-04-16

Four-dimensional (4D) light imaging has been used to study behavior of small structures within motor nerve terminals of the thin transversus abdominis muscle of the garter snake. Raw data comprises time-lapse sequences of 3D z-stacks. Each stack contains 4-20 images acquired with epifluorescence optics at focal planes separated by 400-1,500 nm. Steps in the acquisition of image stacks, such as adjustment of focus, switching of excitation wavelengths, and operation of the digital camera, are automated as much as possible to maximize image rate and minimize tissue damage from light exposure. After acquisition, a set of image stacks is deconvolved to improve spatial resolution, converted to the desired 3D format, and used to create a 4D "movie" that is suitable for variety of computer-based analyses, depending upon the experimental data sought. One application is study of the dynamic behavior of two classes of endosomes found in nerve terminals-macroendosomes (MEs) and acidic endosomes (AEs)-whose sizes (200-800 nm for both types) are at or near the diffraction limit. Access to 3D information at each time point provides several advantages over conventional time-lapse imaging. In particular, size and velocity of movement of structures can be quantified over time without loss of sharp focus. Examples of data from 4D imaging reveal that MEs approach the plasma membrane and disappear, suggesting that they are exocytosed rather than simply moving vertically away from a single plane of focus. Also revealed is putative fusion of MEs and AEs, by visualization of overlap between the two dye-containing structures as viewed in each three orthogonal projections.

Calcium channel blockers and transmitter release at the normal human neuromuscular junction.

PubMed

Protti, D A; Reisin, R; Mackinley, T A; Uchitel, O D

1996-05-01

Transmitter release evoked by nerve stimulation is highly dependent on Ca2+ entry through voltage-activated plasma membrane channels. Calcium influx may be modified in some neuromuscular diseases like Lambert-Eaton syndrome and amyotrophic lateral sclerosis. We studied the pharmacologic sensitivity of the transmitter release process to different calcium channel blockers in normal human muscles and found that funnel web toxin and omega-Agatoxin-IVA, both P-type calcium channel blockers, blocked nerve-elicited muscle action potentials and inhibited evoked synaptic transmission. The transmitter release was not affected either by nitrendipine, an L-type channel blocker, or omega-Conotoxin-GVIA, an N-type channel blocker. The pharmacologic profile of neuromuscular transmission observed in normal human muscles indicates that P-like channels mediate transmitter release at the motor nerve terminals.

Ultrastructural identification of noradrenergic nerve terminals and vasopressin-containing neurons of the paraventricular nucleus in the same thin section.

PubMed

Silverman, A J; Hou-Yu, A; Oldfield, B J

1983-09-01

Since many peptidergic cell groups receive a diverse and complex monoaminergic innervation, we have developed a double-label procedure to visualize a peptide and a catecholamine in the same ultrathin section. Radiolabeled norepinephrine (NE) is applied locally and its reuptake into NE terminals is demonstrated by ultrastructural radioautography. Controls in this and other studies demonstrate that the NE labels only NE (and possibly epinephrine) terminals and not dopaminergic or serotonergic terminals. In the same tissue, vasopressin is localized by immunocytochemistry on unembedded sections that are subsequently embedded in epoxy resins for thin sectioning. The procedure as described here shows that NE terminals in the periventricular zone of the paraventricular nucleus of the hypothalamus innervate both vasopressin-positive and vasopressin-negative structures. This technique is useful in determining the chemical connectivity of the hypothalamus.

The thoracic muscular system and its innervation in third instar Calliphora vicina Larvae. II. Projection patterns of the nerves associated with the pro- and mesothorax and the pharyngeal complex.

PubMed

Schoofs, Andreas; Hanslik, Ulrike; Niederegger, Senta; Heinzel, Hans-Georg; Spiess, Roland

2010-08-01

We describe the anatomy of the nerves that project from the central nervous system (CNS) to the pro- and mesothoracic segments and the cephalopharyngeal skeleton (CPS) for third instar Calliphora larvae. Due to the complex branching pattern we introduce a nomenclature that labels side branches of first and second order. Two fine nerves that were not yet described are briefly introduced. One paired nerve projects to the ventral arms (VAs) of the CPS. The second, an unpaired nerve, projects to the ventral surface of the cibarial part of the esophagus (ES). Both nerves were tentatively labeled after the structures they innervate. The antennal nerve (AN) innervates the olfactory dorsal organ (DO). It contains motor pathways that project through the frontal connectives (FC) to the frontal nerve (FN) and innervate the cibarial dilator muscles (CDM) which mediate food ingestion. The maxillary nerve (MN) innervates the sensory terminal organ (TO), ventral organ (VO), and labial organ (LO) and comprises the motor pathways to the mouth hook (MH) elevator, MH depressor, and the labial retractor (LR) which opens the mouth cavity. An anastomosis of unknown function exists between the AN and MN. The prothoracic accessory nerve (PaN) innervates a dorsal protractor muscle of the CPS and sends side branches to the aorta and the bolwig organ (BO) (stemmata). In its further course, this nerve merges with the prothoracic nerve (PN). The architecture of the PN is extremely complex. It innervates a set of accessory pharyngeal muscles attached to the CPS and the body wall musculature of the prothorax. Several anastomoses exist between side branches of this nerve which were shown to contain motor pathways. The mesothoracic nerve (MeN) innervates a MH accessor and the longitudinal and transversal body wall muscles of the second segment. J. Morphol. 271:969-979, 2010. (c) 2010 Wiley-Liss, Inc.

A common neural circuit mechanism for internally guided and externally reinforced forms of motor learning.

PubMed

Hisey, Erin; Kearney, Matthew Gene; Mooney, Richard

2018-04-01

The complex skills underlying verbal and musical expression can be learned without external punishment or reward, indicating their learning is internally guided. The neural mechanisms that mediate internally guided learning are poorly understood, but a circuit comprising dopamine-releasing neurons in the midbrain ventral tegmental area (VTA) and their targets in the basal ganglia are important to externally reinforced learning. Juvenile zebra finches copy a tutor song in a process that is internally guided and, in adulthood, can learn to modify the fundamental frequency (pitch) of a target syllable in response to external reinforcement with white noise. Here we combined intersectional genetic ablation of VTA neurons, reversible blockade of dopamine receptors in the basal ganglia, and singing-triggered optogenetic stimulation of VTA terminals to establish that a common VTA-basal ganglia circuit enables internally guided song copying and externally reinforced syllable pitch learning.

Fibroblast Growth Factor 22 Contributes to the Development of Retinal Nerve Terminals in the Dorsal Lateral Geniculate Nucleus

PubMed Central

Singh, Rishabh; Su, Jianmin; Brooks, Justin; Terauchi, Akiko; Umemori, Hisashi; Fox, Michael A.

2012-01-01

At least three forms of signaling between pre- and postsynaptic partners are necessary during synapse formation. First, “targeting” signals instruct presynaptic axons to recognize and adhere to the correct portion of a postsynaptic target cell. Second, trans-synaptic “organizing” signals induce differentiation in their synaptic partner so that each side of the synapse is specialized for synaptic transmission. Finally, in many regions of the nervous system an excess of synapses are initially formed, therefore “refinement” signals must either stabilize or destabilize the synapse to reinforce or eliminate connections, respectively. Because of both their importance in processing visual information and their accessibility, retinogeniculate synapses have served as a model for studying synaptic development. Molecular signals that drive retinogeniculate “targeting” and “refinement” have been identified, however, little is known about what “organizing” cues are necessary for the differentiation of retinal axons into presynaptic terminals. To identify such “organizing” cues, we used microarray analysis to assess whether any target-derived “synaptic organizers” were enriched in the mouse dorsal lateral geniculate nucleus (dLGN) during retinogeniculate synapse formation. One candidate “organizing” molecule enriched in perinatal dLGN was FGF22, a secreted cue that induces the formation of excitatory nerve terminals in muscle, hippocampus, and cerebellum. In FGF22 knockout mice, the development of retinal terminals in dLGN was impaired. Thus, FGF22 is an important “organizing” cue for the timely development of retinogeniculate synapses. PMID:22363257

GLUT4 Mobilization Supports Energetic Demands of Active Synapses.

PubMed

Ashrafi, Ghazaleh; Wu, Zhuhao; Farrell, Ryan J; Ryan, Timothy A

2017-02-08

The brain is highly sensitive to proper fuel availability as evidenced by the rapid decline in neuronal function during ischemic attacks and acute severe hypoglycemia. We previously showed that sustained presynaptic function requires activity-driven glycolysis. Here, we provide strong evidence that during action potential (AP) firing, nerve terminals rely on the glucose transporter GLUT4 as a glycolytic regulatory system to meet the activity-driven increase in energy demands. Activity at synapses triggers insertion of GLUT4 into the axonal plasma membrane driven by activation of the metabolic sensor AMP kinase. Furthermore, we show that genetic ablation of GLUT4 leads to an arrest of synaptic vesicle recycling during sustained AP firing, similar to what is observed during acute glucose deprivation. The reliance on this biochemical regulatory system for "exercising" synapses is reminiscent of that occurring in exercising muscle to sustain cellular function and identifies nerve terminals as critical sites of proper metabolic control. Copyright © 2017 Elsevier Inc. All rights reserved.

Recycling of Kinesin-1 Motors by Diffusion after Transport

PubMed Central

Blasius, T. Lynne; Reed, Nathan; Slepchenko, Boris M.; Verhey, Kristen J.

2013-01-01

Kinesin motors drive the long-distance anterograde transport of cellular components along microtubule tracks. Kinesin-dependent transport plays a critical role in neurogenesis and neuronal function due to the large distance separating the soma and nerve terminal. The fate of kinesin motors after delivery of their cargoes is unknown but has been postulated to involve degradation at the nerve terminal, recycling via retrograde motors, and/or recycling via diffusion. We set out to test these models concerning the fate of kinesin-1 motors after completion of transport in neuronal cells. We find that kinesin-1 motors are neither degraded nor returned by retrograde motors. By combining mathematical modeling and experimental analysis, we propose a model in which the distribution and recycling of kinesin-1 motors fits a “loose bucket brigade” where individual motors alter between periods of active transport and free diffusion within neuronal processes. These results suggest that individual kinesin-1 motors are utilized for multiple rounds of transport. PMID:24098765

Reduced 3,4-Methylenedioxymethamphetamine (MDMA, Ecstasy)-Initiated Oxidative DNA Damage and Neurodegeneration in Prostaglandin H Synthase-1 Knockout Mice

PubMed Central

2010-01-01

The neurodegenerative potential of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) and underlying mechanisms are under debate. Here, we show that MDMA is a substrate for CNS prostaglandin H synthase (PHS)-catalyzed bioactivation to a free radical intermediate that causes reactive oxygen species (ROS) formation and neurodegenerative oxidative DNA damage. In vitro PHS-1-catalyzed bioactivation of MDMA stereoselectively produced free radical intermediate formation and oxidative DNA damage that was blocked by the PHS inhibitor eicosatetraynoic acid. In vivo, MDMA stereoselectively caused gender-independent DNA oxidation and dopaminergic nerve terminal degeneration in several brain regions, dependent on regional PHS-1 levels. Conversely, MDMA-initiated striatal DNA oxidation, nerve terminal degeneration, and motor coordination deficits were reduced in PHS-1 +/− and −/− knockout mice in a gene dose-dependent fashion. These results confirm the neurodegenerative potential of MDMA and provide the first direct evidence for a novel molecular mechanism involving PHS-catalyzed formation of a neurotoxic MDMA free radical intermediate. PMID:22778832

Collagen-derived matricryptins promote inhibitory nerve terminal formation in the developing neocortex

PubMed Central

Su, Jianmin; Chen, Jiang; Lippold, Kumiko; Monavarfeshani, Aboozar; Carrillo, Gabriela Lizana; Jenkins, Rachel

2016-01-01

Inhibitory synapses comprise only ∼20% of the total synapses in the mammalian brain but play essential roles in controlling neuronal activity. In fact, perturbing inhibitory synapses is associated with complex brain disorders, such as schizophrenia and epilepsy. Although many types of inhibitory synapses exist, these disorders have been strongly linked to defects in inhibitory synapses formed by Parvalbumin-expressing interneurons. Here, we discovered a novel role for an unconventional collagen—collagen XIX—in the formation of Parvalbumin+ inhibitory synapses. Loss of this collagen results not only in decreased inhibitory synapse number, but also in the acquisition of schizophrenia-related behaviors. Mechanistically, these studies reveal that a proteolytically released fragment of this collagen, termed a matricryptin, promotes the assembly of inhibitory nerve terminals through integrin receptors. Collectively, these studies not only identify roles for collagen-derived matricryptins in cortical circuit formation, but they also reveal a novel paracrine mechanism that regulates the assembly of these synapses. PMID:26975851

[Roles of biologically active peptide in regulation of feeding behavior and energy homeostasis].

PubMed

Sakurai, Takeshi

2003-09-01

The mechanisms for regulating food intake involve a complicated interplay between peripheral systems (including gastrointestinal peptide secretion, leptin, and vagal afferent nerve responses) and central nervous system (CNS) neuropeptides and/or monoamines. Many hypothalamic neuropeptides are involved in the regulation of energy homeostasis and feeding behavior, including melanocortins, Agouti-related peptide, neuropeptide-Y, cocaine, and amphetamine-regulated transcript, orexin, and melanine concentrating hormone (MCH) as well as monamines (serotonin, dopamine, norepinephrine). Many of these systems are regulated by peripheral metabolic cues including plasma leptin levels. This review summarizes roles of neuropeptides in the regulatory mechanism of feeding and energy homeostasis.

Innervation of arteriovenous anastomoses in the sheep tongue: immunocytochemical evidence for coexistence of neural transmitters.

PubMed Central

Molyneux, G S; Haller, C J

1988-01-01

In this study structural and immunocytochemical evidence has shown that arterial vessels, particularly AVAs, are associated with nerves containing peptidergic vasodilators, viz. VIP, CGRP and SP. The presence of VIP-like immunoreactivity in both P-type and C-type nerves is evidence of the coexistence of VIP and acetylcholine in cholinergic nerves and suggests the action of VIP in maintaining the opening of AVAs in heat stress conditions. The evidence for the co-existence of CGRP and SP is more direct as immunoreactivity for both peptides has been demonstrated in serial sections of the same nerve terminal. Although SP is a potent vasodilator there is little evidence of its role in thermoregulation; however it may be involved in a local axon reflex and cause antidromic vasodilatation of local vessels particularly AVAs. Images Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 4 Fig. 5 Fig. 1 Fig. 2 Fig. 3 PMID:2461925

Neural control of renal tubular sodium reabsorption of the dog.

PubMed

DiBona, G F

1978-04-01

The evidence supporting a role for direct neurogenic control of renal tubular sodium reabsorption is reviewed. Electron microscopic and fluorescence histochemical studies demonstrate adrenergic nerve terminals in direct contact with basement membranes of mammalian renal tubular epithelial cells. Low level direct or baroreceptor reflex stimulation of renal sympathetic nerves produces an increase in renal tubular sodium reabsorption without alterations in glomerular filtration rate, renal blood flow, or intrarenal distribution of blood flow. The antinatriuresis is prevented by prior treatment of the kidney with guanethidine or phenoxybenzamine. Possible indirect mediation of the antinatriuresis by other humoral agents known to be released from the kidney upon renal nerve stimulation (angiotensin II, prostaglandin) was excluded by experiments with appropriate blocking agents. Reflex diminutions in renal nerve activity (left atrial distention, stellate ganglion stimulation) produce a decrease in renal tubular sodium reabsorption independent of glomerular filtration rate or renal blood flow. The anatomically described adrenergic innervation of the renal tubules participates in the direct regulation of renal tubular sodium reabsorption.

Peripheral innervation patterns of vestibular nerve afferents in the bullfrog utriculus

NASA Technical Reports Server (NTRS)

Baird, Richard A.; Schuff, N. R.

1994-01-01

Vestibular nerve afferents innervating the bullfrog utriculus differ in their response dynamics and sensitivity to natural stimulation. They also supply hair cells that differ markedly in hair bundle morphology. To examine the peripheral innervation patterns of individual utricular afferents more closely, afferent fibers were labeled by the extracellular injection of horseradish peroxidase (HRP) into the vestibular nerve after sectioning the vestibular nerve medial to Scarpa's ganglion to allow the degeneration of sympathetic and efferent fibers. The peripheral arborizations of individual afferents were then correlated with the diameters of their parent axons, the regions of the macula they innervate, and the number and type of hair cells they supply. The utriculus is divided by the striola, a narrow zone of distinctive morphology, into media and lateral parts. Utiricular afferents were classified as striolar or extrastriolar according to the epithelial entrance of their parent axons and the location of their terminal fields. In general, striolar afferents had thicker parent axons, fewer subepithelial bifurcations, larger terminal fields, and more synaptic endings than afferents in extrstriolar regions. Afferents in a juxtastriolar zone, immediately adjacent to the medial striola, had innervation patterns transitional between those in the striola and more peripheral parts of the medial extrastriola. moast afferents innervated only a single macular zone. The terminal fields of striolar afferents, with the notable exception of a few afferents with thin parent axons, were generally confined to one side of the striola. Hair cells in the bullfrog utriculus have perviously been classified into four types based on hair bundle morphology. Afferents in the extrastriolar and juxtastriolar zones largely or exclusively innervated Type B hair cells, the predominant hair cell type in the utricular macula. Striolar afferents supplied a mixture of four hair cell types, but largely contacted Type B and Type C hair cells, particularly on the outer rows of the medial striola. Afferents supplying more central striolar regions innervated fewer Type B and larger numbers of Type E and Type F hair cells. Striolar afferents with thin parent axons largely supplied Type E hair cells with bulbed kniocilia in the innermost striolar rows.

Effect of cochlear nerve electrocautery on the adult cochlear nucleus.

PubMed

Iseli, Claire E; Merwin, William H; Klatt-Cromwell, Cristine; Hutson, Kendall A; Ewend, Matthew G; Adunka, Oliver F; Fitzpatrick, Douglas C; Buchman, Craig A

2015-04-01

Electrocauterization and subsequent transection of the cochlear nerve induce greater injury to the cochlear nucleus than sharp transection alone. Some studies show that neurofibromatosis Type 2 (NF2) patients fit with auditory brainstem implants (ABIs) fail to achieve speech perception abilities similar to ABI recipients without NF2. Reasons for these differences remain speculative. One hypothesis posits poorer performance to surgically induced trauma to the cochlear nucleus from electrocautery. Sustained electrosurgical depolarization of the cochlear nerve may cause excitotoxic-induced postsynaptic nuclear injury. Equally plausible is that cautery in the vicinity of the cochlear nucleus induces necrosis. The cochlear nerve was transected in anesthetized adult gerbils sharply with or without bipolar electrocautery at varying intensities. Gerbils were perfused at 1, 3, 5, and 7 days postoperatively; their brainstem and cochleas were embedded in paraffin and sectioned at 10 μm. Alternate sections were stained with flourescent markers for neuronal injury or Nissl substance. In additional experiments, anterograde tracers were applied directly to a sectioned eighth nerve to verify that fluorescent-labeled profiles seen were terminating auditory nerve fibers. Cochlear nerve injury was observed from 72 hours postoperatively and was identical across cases regardless of surgical technique. Postsynaptic cochlear nucleus injury was not seen after distal transection of the nerve. By contrast, proximal transection was associated with trauma to the cochlear nucleus. Distal application of bipolar electrocautery seems safe for the cochlear nucleus. Application near the root entry zone must be used cautiously because this may compromise nuclear viability needed to support ABI stimulation.

The use of targeted muscle reinnervation for improved myoelectric prosthesis control in a bilateral shoulder disarticulation amputee.

PubMed

Kuiken, T A; Dumanian, G A; Lipschutz, R D; Miller, L A; Stubblefield, K A

2004-12-01

A novel method for the control of a myoelectric upper limb prosthesis was achieved in a patient with bilateral amputations at the shoulder disarticulation level. Four independently controlled nerve-muscle units were created by surgically anastomosing residual brachial plexus nerves to dissected and divided aspects of the pectoralis major and minor muscles. The musculocutaneous nerve was anastomosed to the upper pectoralis major; the median nerve was transferred to the middle pectoralis major region; the radial nerve was anastomosed to the lower pectoralis major region; and the ulnar nerve was transferred to the pectoralis minor muscle which was moved out to the lateral chest wall. After five months, three nerve-muscle units were successful (the musculocutaneous, median and radial nerves) in that a contraction could be seen, felt and a surface electromyogram (EMG) could be recorded. Sensory reinnervation also occurred on the chest in an area where the subcutaneous fat was removed. The patient was fitted with a new myoelectric prosthesis using the targeted muscle reinnervation. The patient could simultaneously control two degrees-of-freedom with the experimental prosthesis, the elbow and either the terminal device or wrist. Objective testing showed a doubling of blocks moved with a box and blocks test and a 26% increase in speed with a clothes pin moving test. Subjectively the patient clearly preferred the new prosthesis. He reported that it was easier and faster to use, and felt more natural.

Dietary correlates associated with the mental foramen in primates: implications for interpreting the fossil record.

PubMed

Muchlinski, Magdalena N; Deane, Andrew S

2016-07-01

The mandibular nerve is a sensory and motor nerve that innervates the muscles of mastication, the lower dentition, and the lower lip and surrounding structures. Although this nerve contains both efferent and afferent fibers, the mental nerve, a terminal branch of the mandibular nerve, is a strictly sensory nerve that exits the mental foramen and innervates the lower lip, the skin overlaying the mandible, and the oral mucosa around the mandible. Osteological foramina are often used as proxies for nerve cross section area and they often correlate well with some aspect of a primate's ecology (e.g., optic foramen and visual acuity). The primary objective of this study is to explore the correlation between the mental foramen and dietary preference among primates. The mental foramen of 40 primate species (n = 180) was measured from 3-D surface models of the mandible. Both conventional and phylogenetic tests indicate that although frugivores have larger mental foramina than folivores, the differences were not significant. These results show that while structures like the infraorbital foramen correlate well with diet and touch sensitivity, the mental foramen does not. Based on these findings, the mental foramen is not a suggested morphological character for interpreting of the fossil record. J. Morphol. 277:978-985, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Hypertonic enhancement of transmitter release from frog motor nerve terminals: Ca2+ independence and role of integrins

NASA Technical Reports Server (NTRS)

Kashani, A. H.; Chen, B. M.; Grinnell, A. D.

2001-01-01

Hyperosmotic solutions cause markedly enhanced spontaneous quantal release of neurotransmitter from many nerve terminals. The mechanism of this enhancement is unknown. We have investigated this phenomenon at the frog neuromuscular junction with the aim of determining the degree to which it resembles the modulation of release by stretch, which has been shown to be mediated by mechanical tension on integrins.The hypertonicity enhancement, like the stretch effect, does not require Ca2+ influx or release from internal stores, although internal release may contribute to the effect. The hypertonicity effect is sharply reduced (but not eliminated) by peptides containing the RGD sequence, which compete with native ligands for integrin bonds.There is co-variance in the magnitude of the stretch and osmotic effects; that is, individual terminals exhibiting a large stretch effect also show strong enhancement by hypertonicity, and vice versa. The stretch and osmotic enhancements also can partially occlude each other.There remain some clear-cut differences between osmotic and stretch forms of modulation: the larger range of enhancement by hypertonic solutions, the relative lack of effect of osmolarity on evoked release, and the reported higher temperature sensitivity of osmotic enhancement. Nevertheless, our data strongly implicate integrins in a significant fraction of the osmotic enhancement, possibly acting via the same mechanism as stretch modulation.

Terminal Schwann Cells Participate in Neuromuscular Synapse Remodeling during Reinnervation following Nerve Injury

PubMed Central

Kang, Hyuno; Tian, Le; Mikesh, Michelle; Lichtman, Jeff W.

2014-01-01

Schwann cells (SCs) at neuromuscular junctions (NMJs) play active roles in synaptic homeostasis and repair. We have studied how SCs contribute to reinnervation of NMJs using vital imaging of mice whose motor axons and SCs are transgenically labeled with different colors of fluorescent proteins. Motor axons most commonly regenerate to the original synaptic site by following SC-filled endoneurial tubes. During the period of denervation, SCs at the NMJ extend elaborate processes from the junction, as shown previously, but they also retract some processes from territory they previously occupied within the endplate. The degree of this retraction depends on the length of the period of denervation. We show that the topology of the remaining SC processes influences the branching pattern of regenerating axon terminals and the redistribution of acetylcholine receptors (AChRs). Upon arriving at the junction, regenerating axons follow existing SC processes within the old synaptic site. Some of the AChR loss that follows denervation is correlated with failure of portions of the old synaptic site that lack SC coverage to be reinnervated. New AChR clustering is also induced by axon terminals that follow SC processes extended during denervation. These observations show that SCs participate actively in the remodeling of neuromuscular synapses following nerve injury by their guidance of axonal reinnervation. PMID:24790203

In vitro assessment of induced phrenic nerve cryothermal injury.

PubMed

Goff, Ryan P; Bersie, Stephanie M; Iaizzo, Paul A

2014-10-01

Phrenic nerve injury, both left and right, is considered a significant complication of cryoballoon ablation for treatment of drug-refractory atrial fibrillation, and functional recovery of the phrenic nerve can take anywhere from hours to months. The purpose of this study was to focus on short periods of cooling to determine the minimal amount of cooling that may terminate nerve function related to cryo ablation. Left and/or right phrenic nerves were dissected from the pericardium and connective tissue of swine (n = 35 preparations). Nerves were placed in a recording chamber modified with a thermocouple array. This apparatus was placed in a digital water bath to maintain an internal chamber temperature of 37°C. Nerves were stimulated proximally with a 1-V, 0.1-ms square wave. Bipolar compound action potentials were recorded proximal and distal to the site of ablation both before and after ablation, then analyzed to determine changes in latency, amplitude, and duration. Temperatures were recorded at a rate of 5 Hz, and maximum cooling rates were calculated. Phrenic nerves were found to elicit compound action potentials upon stimulation for periods up to 4 hours minimum. Average conduction velocity was 56.7 ± 14.7 m/s preablation and 49.8 ± 16.6 m/s postablation (P = .17). Cooling to mild subzero temperatures ceased production of action potentials for >1 hour. Taking into account the data presented here, previous publications, and a conservative stance, during cryotherapy applications, cooling of the nerve to below 4°C should be avoided whenever possible. Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

The role of illicit drug use in sudden death in the young.

PubMed

Fischbach, Peter

2017-01-01

The recreational use of illicit drugs remains an enormous and growing problem throughout the United States of America and around the world. Cocaine is most frequently thought of when considering the cardiovascular toxicity of illicit drugs. The association of cocaine use with sudden death due to myocardial ischaemia and infarction is well recognised, and this risk appears to be amplified by concomitant cigarette smoking and alcohol consumption. Like cocaine, amphetamine and its derivatives lead to indirect stimulation of the autonomic nervous system through the release of norepinephrine, dopamine, and serotonin in nerve terminals of the central and autonomic nervous systems. However, amphetamine lacks the ion channel-blocking properties of cocaine. Also similar to cocaine, coronary artery spasm may be induced in individuals with or without atherosclerotic disease and may lead to myocardial infarction. With the movement across the United States of America to legalise marijuana, or cannabis, for medicinal and recreational purposes, it is important to consider its potential deleterious effects. Marijuana has long been thought to have very few adverse effects with the exception of long-term dependence. There are, however, scattered reports of acute adverse events up to and including sudden death. These appear to be due to myocardial infarction. In conclusion, the incidence of sudden death associated with the use of these drugs varies from rare in the case of marijuana use to not infrequent with some drugs such as cocaine. It is important for care providers to recognise the potential for drug abuse when caring for a sudden cardiac arrest survivor.

PINK1-Mediated Phosphorylation of Parkin Boosts Parkin Activity in Drosophila

PubMed Central

Shiba-Fukushima, Kahori; Inoshita, Tsuyoshi; Hattori, Nobutaka; Imai, Yuzuru

2014-01-01

Two genes linked to early onset Parkinson's disease, PINK1 and Parkin, encode a protein kinase and a ubiquitin-ligase, respectively. Both enzymes have been suggested to support mitochondrial quality control. We have reported that Parkin is phosphorylated at Ser65 within the ubiquitin-like domain by PINK1 in mammalian cultured cells. However, it remains unclear whether Parkin phosphorylation is involved in mitochondrial maintenance and activity of dopaminergic neurons in vivo. Here, we examined the effects of Parkin phosphorylation in Drosophila, in which the phosphorylation residue is conserved at Ser94. Morphological changes of mitochondria caused by the ectopic expression of wild-type Parkin in muscle tissue and brain dopaminergic neurons disappeared in the absence of PINK1. In contrast, phosphomimetic Parkin accelerated mitochondrial fragmentation or aggregation and the degradation of mitochondrial proteins regardless of PINK1 activity, suggesting that the phosphorylation of Parkin boosts its ubiquitin-ligase activity. A non-phosphorylated form of Parkin fully rescued the muscular mitochondrial degeneration due to the loss of PINK1 activity, whereas the introduction of the non-phosphorylated Parkin mutant in Parkin-null flies led to the emergence of abnormally fused mitochondria in the muscle tissue. Manipulating the Parkin phosphorylation status affected spontaneous dopamine release in the nerve terminals of dopaminergic neurons, the survivability of dopaminergic neurons and flight activity. Our data reveal that Parkin phosphorylation regulates not only mitochondrial function but also the neuronal activity of dopaminergic neurons in vivo, suggesting that the appropriate regulation of Parkin phosphorylation is important for muscular and dopaminergic functions. PMID:24901221

Linear ordered collagen scaffolds loaded with collagen-binding basic fibroblast growth factor facilitate recovery of sciatic nerve injury in rats.

PubMed

Ma, Fukai; Xiao, Zhifeng; Chen, Bing; Hou, Xianglin; Dai, Jianwu; Xu, Ruxiang

2014-04-01

Natural biological functional scaffolds, consisting of biological materials filled with promoting elements, provide a promising strategy for the regeneration of peripheral nerve defects. Collagen conduits have been used widely due to their excellent biological properties. Linear ordered collagen scaffold (LOCS) fibers are good lumen fillers that can guide nerve regeneration in an ordered direction. In addition, basic fibroblast growth factor (bFGF) is important in the recovery of nerve injury. However, the traditional method for delivering bFGF to the lesion site has no long-term effect because of its short half-life and rapid diffusion. Therefore, we fused a specific collagen-binding domain (CBD) peptide to the N-terminal of native basic fibroblast growth factor (NAT-bFGF) to retain bFGF on the collagen scaffolds. In this study, a natural biological functional scaffold was constructed using collagen tubes filled with collagen-binding bFGF (CBD-bFGF)-loaded LOCS to promote regeneration in a 5-mm rat sciatic nerve transection model. Functional evaluation, histological investigation, and morphometric analysis indicated that the natural biological functional scaffold retained more bFGF at the injury site, guided axon growth, and promoted nerve regeneration as well as functional restoration.

Serial neurophysiological and neurophysiological examinations for delayed facial nerve palsy in a patient with Fisher syndrome.

PubMed

Umekawa, Motoyuki; Hatano, Keiko; Matsumoto, Hideyuki; Shimizu, Takahiro; Hashida, Hideji

2017-05-27

The patient was a 47-year-old man who presented with diplopia and gait instability with a gradual onset over the course of three days. Neurological examinations showed ophthalmoplegia, diminished tendon reflexes, and truncal ataxia. Tests for anti-GQ1b antibodies and several other antibodies to ganglioside complex were positive. We made a diagnosis of Fisher syndrome. After administration of intravenous immunoglobulin, the patient's symptoms gradually improved. However, bilateral facial palsy appeared during the recovery phase. Brain MRI showed intensive contrast enhancement of bilateral facial nerves. During the onset phase of facial palsy, the amplitude of the compound muscle action potential (CMAP) in the facial nerves was preserved. During the peak phase, the facial CMAP amplitude was within the lower limit of normal values, or mildly decreased. During the recovery phase, the CMAP amplitude was normalized, and the R1 and R2 responses of the blink reflex were prolonged. The delayed facial nerve palsy improved spontaneously, and the enhancement on brain MRI disappeared. Serial neurophysiological and neuroradiological examinations suggested that the main lesions existed in the proximal part of the facial nerves and the mild lesions existed in the facial nerve terminals, probably due to reversible conduction failure.

Dopamine Signaling Leads to Loss of Polycomb Repression and Aberrant Gene Activation in Experimental Parkinsonism

PubMed Central

Lerdrup, Mads; Gomes, Ana-Luisa; Kryh, Hanna; Spigolon, Giada; Caboche, Jocelyne; Fisone, Gilberto; Hansen, Klaus

2014-01-01

Polycomb group (PcG) proteins bind to and repress genes in embryonic stem cells through lineage commitment to the terminal differentiated state. PcG repressed genes are commonly characterized by the presence of the epigenetic histone mark H3K27me3, catalyzed by the Polycomb repressive complex 2. Here, we present in vivo evidence for a previously unrecognized plasticity of PcG-repressed genes in terminally differentiated brain neurons of parkisonian mice. We show that acute administration of the dopamine precursor, L-DOPA, induces a remarkable increase in H3K27me3S28 phosphorylation. The induction of the H3K27me3S28p histone mark specifically occurs in medium spiny neurons expressing dopamine D1 receptors and is dependent on Msk1 kinase activity and DARPP-32-mediated inhibition of protein phosphatase-1. Chromatin immunoprecipitation (ChIP) experiments showed that increased H3K27me3S28p was accompanied by reduced PcG binding to regulatory regions of genes. An analysis of the genome wide distribution of L-DOPA-induced H3K27me3S28 phosphorylation by ChIP sequencing (ChIP-seq) in combination with expression analysis by RNA-sequencing (RNA-seq) showed that the induction of H3K27me3S28p correlated with increased expression of a subset of PcG repressed genes. We found that induction of H3K27me3S28p persisted during chronic L-DOPA administration to parkisonian mice and correlated with aberrant gene expression. We propose that dopaminergic transmission can activate PcG repressed genes in the adult brain and thereby contribute to long-term maladaptive responses including the motor complications, or dyskinesia, caused by prolonged administration of L-DOPA in Parkinson's disease. PMID:25254549

Origins, actions and dynamic expression patterns of the neuropeptide VGF in rat peripheral and central sensory neurones following peripheral nerve injury

PubMed Central

Moss, Andrew; Ingram, Rachel; Koch, Stephanie; Theodorou, Andria; Low, Lucie; Baccei, Mark; Hathway, Gareth J; Costigan, Michael; Salton, Stephen R; Fitzgerald, Maria

2008-01-01

Background The role of the neurotrophin regulated polypeptide, VGF, has been investigated in a rat spared injury model of neuropathic pain. This peptide has been shown to be associated with synaptic strengthening and learning in the hippocampus and while it is known that VGFmRNA is upregulated in dorsal root ganglia following peripheral nerve injury, the role of this VGF peptide in neuropathic pain has yet to be investigated. Results Prolonged upregulation of VGF mRNA and protein was observed in injured dorsal root ganglion neurons, central terminals and their target dorsal horn neurons. Intrathecal application of TLQP-62, the C-terminal active portion of VGF (5–50 nmol) to naïve rats caused a long-lasting mechanical and cold behavioral allodynia. Direct actions of 50 nM TLQP-62 upon dorsal horn neuron excitability was demonstrated in whole cell patch recordings in spinal cord slices and in receptive field analysis in intact, anesthetized rats where significant actions of VGF were upon spontaneous activity and cold evoked responses. Conclusion VGF expression is therefore highly modulated in nociceptive pathways following peripheral nerve injury and can cause dorsal horn cell excitation and behavioral hypersensitivity in naïve animals. Together the results point to a novel and powerful role for VGF in neuropathic pain. PMID:19077191

Effect of noxious electrical stimulation of the peroneal nerve on stretch reflex activity of the hamstring muscle in rats: possible implications of neuronal mechanisms in the development of tight hamstrings in lumbar disc herniation.

PubMed

Hirayama, Jiro; Yamagata, Masatsune; Takahashi, Kazuhisa; Moriya, Hideshige

2005-05-01

The effect of noxious electrical stimulation of the peroneal nerve on the stretch reflex electromyogram activity of the hamstring muscle (semitendinous) was studied. To verify the following hypothetical mechanisms underlying tight hamstrings in lumbar disc herniation: stretch reflex muscle activity of hamstrings is increased by painful inputs from an injured spinal nerve root and the increased stretch reflex muscle activity is maintained by central sensitization. It is reported that stretch reflex activity of the trunk muscles is induced by noxious stimulation of the sciatic nerve and maintained by central sensitization. In spinalized rats (transected spinal cord), the peroneal nerve was stimulated electrically as a conditioning stimulus. Stretch reflex electromyogram activity of the semitendinous muscle was recorded before and after the conditioning stimulus. Even after electrical stimulation was terminated, an increased stretch reflex activity of the hamstring muscle was observed. It is likely that a central sensitization mechanism at the spinal cord level was involved in the increased reflex activity. Central sensitization may play a part in the neuronal mechanisms of tight hamstrings in lumbar disc herniation.

Schwann Cell Phenotype Changes in Aging Human Dental Pulp.

PubMed

Couve, E; Lovera, M; Suzuki, K; Schmachtenberg, O

2018-03-01

Schwann cells are glial cells that support axonal development, maintenance, defense, and regeneration in the peripheral nervous system. There is limited knowledge regarding the organization, plasticity, and aging of Schwann cells within the dental pulp in adult permanent teeth. The present study sought to relate changes in the pattern of Schwann cell phenotypes between young and old adult teeth with neuronal, immune, and vascular components of the dental pulp. Schwann cells are shown to form a prominent glial network at the dentin-pulp interface, consisting of nonmyelinating and myelinating phenotypes, forming a multicellular neuroimmune interface in association with nerve fibers and dendritic cells. Schwann cell phenotypes are recognized by the expression of S100, glial fibrillary acidic protein (GFAP), myelin basic protein (MBP), Sox10, GAP43, and p75NTR markers. In young adult teeth, a dense population of nonmyelinating Schwann cells projects processes in close association with sensory nerve terminals through the odontoblast layer, reaching the adjacent predentin/dentin domain. While GAP43 and p75NTR are highly expressed in nonmyelinating Schwann cells from young adult teeth, the presence of these markers declines significantly in old adult teeth. Myelinated axons, identified by MBP expression, are mainly present at the Raschkow plexus and within nerve bundles in the dental pulp, but their density is significantly reduced in old adult versus young adult teeth. These data reveal age-related changes within the glial network of the dental pulp, in association with a reduction of coronal dental pulp innervation in old adult versus young adult teeth. The prominence of Schwann cells as a cellular component at the dentin-pulp interface supports the notion that their association with sensory nerve terminals and immune system components forms part of an integrated multicellular barrier for defense against pathogens and dentin repair.

An electrophysiological study on the effects of Pa-1G (a phospholipase A(2)) from the venom of king brown snake, Pseudechis australis, on neuromuscular function.

PubMed

Fatehi, M; Rowan, E G; Harvey, A L

2002-01-01

The effects of Pa-1G, a phospholipase A(2) (PLA(2)) from the venom of the Australian king brown snake (Pseudechis australis) were determined on the release of acetylcholine, muscle resting membrane potential and motor nerve terminal action potential at mouse neuromuscular junction. Intracellular recording from endplate regions of mouse triangularis sterni nerve-muscle preparations revealed that Pa-1G (800 nM) significantly reduced the amplitude of endplate potentials within 10 min exposure. The quantal content of endplate potentials was decreased to 58+/-6% of control after 30 min exposure to 800 nM Pa-1G. The toxin also caused a partial depolarisation of mouse muscle fibres within 60 min exposure. Extracellular recording of action potentials at motor nerve terminals showed that Pa-1G reduced the waveforms associated with both sodium and potassium conductances. To investigate whether this was a direct or indirect effect of the toxin on these ionic currents, whole cell patch clamp experiments were performed using human neuroblastoma (SK-N-SH) cells and B82 mouse fibroblasts stably transfected with rKv1.2. Patch clamp recording experiments confirmed that potassium currents sensitive to alpha-dendrotoxin recorded from B82 cells and sodium currents in SK-N-SH cells were not affected by the toxin. Since neither facilitation of acetylcholine release at mouse neuromuscular junction nor depression of potassium currents in B82 cells has been observed, the apparent blockade of potassium currents at mouse motor nerve endings induced by the toxin is unlikely to be due to a selective block of potassium channels.

Cocaine Self-Administration Produces Long-Lasting Alterations in Dopamine Transporter Responses to Cocaine

PubMed Central

Siciliano, Cody A.; Fordahl, Steve C.

2016-01-01

Cocaine addiction is a debilitating neuropsychiatric disorder characterized by uncontrolled cocaine intake, which is thought to be driven, at least in part, by cocaine-induced deficits in dopamine system function. A decreased ability of cocaine to elevate dopamine levels has been repeatedly observed as a consequence of cocaine use in humans, and preclinical work has highlighted tolerance to cocaine's effects as a primary determinant in the development of aberrant cocaine taking behaviors. Here we determined that cocaine self-administration in rats produced tolerance to the dopamine transporter-inhibiting effects of cocaine in the nucleus accumbens core, which was normalized following a 14 or 60 d abstinence period; however, although these rats appeared to be similar to controls, a single self-administered infusion of cocaine at the end of abstinence, even after 60 d, fully reinstated tolerance to cocaine's effects. A single cocaine infusion in a naive rat had no effect on cocaine potency, demonstrating that cocaine self-administration leaves the dopamine transporter in a “primed” state, which allows for cocaine-induced plasticity to be reinstated by a subthreshold cocaine exposure. Further, reinstatement of cocaine tolerance was accompanied by decreased cocaine-induced locomotion and escalated cocaine intake despite extended abstinence from cocaine. These data demonstrate that cocaine leaves a long-lasting imprint on the dopamine system that is activated by re-exposure to cocaine. Further, these results provide a potential mechanism for severe cocaine binge episodes, which occur even after sustained abstinence from cocaine, and suggest that treatments aimed at transporter sites may be efficacious in promoting binge termination following relapse. SIGNIFICANCE STATEMENT Tolerance is a DSM-V criterion for substance abuse disorders. Abusers consistently show reduced subjective effects of cocaine concomitant with reduced effects of cocaine at its main site of action, the dopamine transporter (DAT). Preclinical literature has shown that reduced cocaine potency at the DAT increases cocaine taking, highlighting the key role of tolerance in addiction. Addiction is characterized by cycles of abstinence, often for many months, followed by relapse, making it important to determine possible interactions between abstinence and subsequent drug re-exposure. Using a rodent model of cocaine abuse, we found long-lasting, possibly permanent, cocaine-induced alterations to the DAT, whereby cocaine tolerance is reinstated by minimal drug exposure, even after recovery of DAT function over prolonged abstinence periods. PMID:27466327

Co-release of noradrenaline and dopamine in the cerebral cortex elicited by single train and repeated train stimulation of the locus coeruleus

PubMed Central

Devoto, Paola; Flore, Giovanna; Saba, Pierluigi; Fà, Mauro; Gessa, Gian Luigi

2005-01-01

Background Previous studies by our group suggest that extracellular dopamine (DA) and noradrenaline (NA) may be co-released from noradrenergic nerve terminals in the cerebral cortex. We recently demonstrated that the concomitant release of DA and NA could be elicited in the cerebral cortex by electrical stimulation of the locus coeruleus (LC). This study analyses the effect of both single train and repeated electrical stimulation of LC on NA and DA release in the medial prefrontal cortex (mPFC), occipital cortex (Occ), and caudate nucleus. To rule out possible stressful effects of electrical stimulation, experiments were performed on chloral hydrate anaesthetised rats. Results Twenty min electrical stimulation of the LC, with burst type pattern of pulses, increased NA and DA both in the mPFC and in the Occ. NA in both cortices and DA in the mPFC returned to baseline within 20 min after the end of the stimulation period, while DA in the Occ reached a maximum increase during 20 min post-stimulation and remained higher than baseline values at 220 min post-stimulation. Local perfusion with tetrodotoxin (TTX, 10 μM) markedly reduced baseline NA and DA in the mPFC and Occ and totally suppressed the effect of electrical stimulation in both areas. A sequence of five 20 min stimulations at 20 min intervals were delivered to the LC. Each stimulus increased NA to the same extent and duration as the first stimulus, whereas DA remained elevated at the time next stimulus was delivered, so that baseline DA progressively increased in the mPFC and Occ to reach about 130 and 200% the initial level, respectively. In the presence of the NA transport (NAT) blocker desipramine (DMI, 100 μM), multiple LC stimulation still increased extracellular NA and DA levels. Electrical stimulation of the LC increased NA levels in the homolateral caudate nucleus, but failed to modify DA level. Conclusion The results confirm and extend that LC stimulation induces a concomitant release of DA and NA in the mPFC and Occ. The different time-course of LC-induced elevation of DA and NA suggests that their co-release may be differentially controlled. PMID:15865626

Characterization of the effects of serotonin on the release of (/sup 3/H)dopamine from rat nucleus accumbens and striatal slices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nurse, B.; Russell, V.A.; Taljaard, J.J.

1988-05-01

The effect of serotonin agonists on the depolarization (K+)-induced, calcium-dependent, release of (/sup 3/H)dopamine (DA) from rat nucleus accumbens and striatal slices was investigated. Serotonin enhanced basal /sup 3/H overflow and reduced K+-induced release of (/sup 3/H)DA from nucleus accumbens slices. The effect of serotonin on basal /sup 3/H overflow was not altered by the serotonin antagonist, methysergide, or the serotonin re-uptake blocker, chlorimipramine, but was reversed by the DA re-uptake carrier inhibitors nomifensine and benztropine. With the effect on basal overflow blocked, serotonin did not modulate K+-induced release of (/sup 3/H)DA in the nucleus accumbens or striatum. The serotoninmore » agonists, quipazine (in the presence of nomifensine) and 5-methoxytryptamine, did not significantly affect K+-induced release of (/sup 3/H)DA in the nucleus accumbens. This study does not support suggestions that serotonin receptors inhibit the depolarization-induced release of dopamine in the nucleus accumbens or striatum of the rat brain. The present results do not preclude the possibility that serotonin may affect the mesolimbic reward system at a site which is post-synaptic to dopaminergic terminals in the nucleus accumbens.« less

Acetylcholine Encodes Long-Lasting Presynaptic Plasticity at Glutamatergic Synapses in the Dorsal Striatum after Repeated Amphetamine Exposure

PubMed Central

Wang, Wengang; Darvas, Martin; Storey, Granville P.; Bamford, Ian J.; Gibbs, Jeffrey T.; Palmiter, Richard D.

2013-01-01

Locomotion and cue-dependent behaviors are modified through corticostriatal signaling whereby short-term increases in dopamine availability can provoke persistent changes in glutamate release that contribute to neuropsychiatric disorders, including Parkinson's disease and drug dependence. We found that withdrawal of mice from repeated amphetamine treatment caused a chronic presynaptic depression (CPD) in glutamate release that was most pronounced in corticostriatal terminals with a low probability of release and lasted >50 d in treated mice. An amphetamine challenge reversed CPD via a dopamine D1-receptor-dependent paradoxical presynaptic potentiation (PPP) that increased corticostriatal activity in direct pathway medium spiny neurons. This PPP was correlated with locomotor responses after a drug challenge, suggesting that it may underlie the sensitization process. Experiments in brain slices and in vivo indicated that dopamine regulation of acetylcholine release from tonically active interneurons contributes to CPD, PPP, locomotor sensitization, and cognitive ability. Therefore, a chronic decrease in corticostriatal activity during withdrawal is regulated around a new physiological range by tonically active interneurons and returns to normal upon reexposure to amphetamine, suggesting that this paradoxical return of striatal activity to a more stable, normalized state may represent an additional source of drug motivation during abstinence. PMID:23785153

Effect of dopamine agonist withdrawal after long-term therapy in prolactinomas. Studies with high-definition computerised tomography.

PubMed

Johnston, D G; Hall, K; Kendall-Taylor, P; Patrick, D; Watson, M; Cook, D B

1984-07-28

The clinical, radiological, and biochemical effects of dopamine agonist withdrawal after long-term treatment were investigated in seven women and eight men who had been treated for prolactinomas for 1.5 to 7 (mean 3.7) years. Before treatment, serum prolactin concentrations were 1473 to 115 000 mU/l, all patients had abnormal radiological findings, and six had suprasellar extensions of pituitary tumours. Treatment with either bromocriptine or pergolide relieved symptoms and suppressed prolactin secretion in most patients. The size of the residual tumour was defined by doing fourth generation computerised tomographic scans immediately before termination of therapy, and evidence of tumour re-expansion was sought on scans repeated 5-39 weeks later. After discontinuation of treatment, symptoms recurred in 13 of 15 patients and hyper-prolactinaemia redeveloped in 14. Other pituitary function tests remained unchanged or improved. In 13 of 15 patients tumour or gland size did not change after withdrawal of treatment. One man had a marginal increase in tumour size, while in another the pituitary tumour shrank. Thus, although cessation of long-term dopamine agonist therapy leads to recurrence of symptoms and hyperprolactinaemia, rapid tumour regrowth is uncommon and of small extent, and other pituitary function is not altered in the short term.

Dopamine D4 receptor, but not the ADHD-associated D4.7 variant, forms functional heteromers with the dopamine D2S receptor in the brain

PubMed Central

González, Sergio; Rangel-Barajas, Claudia; Peper, Marcela; Lorenzo, Ramiro; Moreno, Estefanía; Ciruela, Francisco; Borycz, Janusz; Ortiz, Jordi; Lluís, Carme; Franco, Rafael; McCormick, Peter J.; Volkow, Nora D.; Rubinstein, Marcelo; Floran, Benjamin; Ferré, Sergi

2011-01-01

Polymorphic variants of the dopamine D4 receptor have been consistently associated with attention-deficit hyperactivity disorder (ADHD). However the functional significance of the risk polymorphism (variable number of tandem repeats in exon 3) is still unclear. Here we show that whereas the most frequent 4-repeat (D4.4) and the 2-repeat (D4.2) variants form functional heteromers with the short isoform of the dopamine D2 receptor (D2S), the 7-repeat risk allele (D4.7) does not. D2 receptor activation in the D2S-D4 receptor heteromer potentiates D4 receptor-mediated MAPK signaling in transfected cells and in the striatum, which did not occur in cells expressing D4.7 or in the striatum of knock-in mutant mice carrying the 7 repeats of the human D4.7 in the third intracellular loop of the D4 receptor. In the striatum D4 receptors are localized in cortico-striatal glutamatergic terminals, where they selectively modulate glutamatergic neurotransmission by interacting with D2S receptors. This interaction shows the same qualitative characteristics than the D2S-D4 receptor heteromer-mediated MAPK signaling and D2S receptor activation potentiates D4 receptor-mediated inibition of striatal glutamate release. It is therefore postulated that dysfunctional D2S-D4.7 heteromers may impair presynaptic dopaminergic control of corticostriatal glutamatergic neurotransmission and explain functional deficits associated with ADHD. PMID:21844870

Site(s) and ionic basis of α-autoinhibition and facilitation of [3H]noradrenaline secretion in guinea-pig vas deferens

PubMed Central

Alberts, P.; Bartfai, T.; Stjärne, L.

1981-01-01

1. Mechanisms controlling the secretion of [3H]noradrenaline from the noradrenergic nerves of guinea-pig isolated vas deferens, prelabelled by incubation with [3H]noradrenaline, were studied using (a) different modes of (extramural or transmural) electrical nerve stimulation (a total of 300 shocks of varying strength, and a duration of 2 msec) at 1-30 Hz, or (b) depolarizing concentrations of K+ (60-110 mm). 2. The fractional rise in efflux of 3H-labelled material (Δt) was used to measure the secretion of [3H]noradrenaline. 3. The dependence of [3H]noradrenaline secretion on the external Ca2+ concentration (1-8 mm) was essentially hyperbolic. Double reciprocal plot analysis (1/Δt vs. 1/Ca2+) of the data yields that blockade of α-autoinhibition (phentolamine 1 μm) does not increase the maximal secretory velocity, but does enhance the apparent affinity of the secretory mechanism for external Ca2+. Exogenous noradrenaline has (qualitatively) opposite effects. The interaction between α-autoinhibition and external Ca2+ thus shows a `competitive' pattern, indicating that restriction of the utilization of external Ca2+ is a major mechanism in α-autoinhibition of noradrenaline secretion, in this system. 4. Phenoxybenzamine (10 μm) and phentolamine (1 μm) increased the secretion of [3H]noradrenaline evoked by depolarization with K+ much less than that caused by electrical nerve stimulation (frequencies up to 10 Hz). Exogenous noradrenaline (1-5 μm) depressed the secretion evoked by both modes of stimulation. The results indicate that α-autoinhibition of [3H]noradrenaline secretion is mainly operative when the secretory stimulus requires conduction of nerve impulses between varicosities. 5. The frequency dependence of [3H]noradrenaline secretion was hyperbolic, both in the presence and in the absence of α-autoinhibition; at each frequency the secretion (Δt per shock) increased with the Ca2+ concentration in the medium (0·6-8 mm). Double reciprocal plot analysis (1/Δt vs. 1/frequency) of the data yields that the pattern of interaction between external Ca2+ and facilitation depends on the presence or absence of α-autoinhibition (phentolamine 1 μm); in the former case it is `non-competitive', in the latter `competitive'. Similar analysis of the effect of facilitation by increasing the length of stimulus trains (from 5 to 300 pulses) at a constant frequency (5 Hz), on the Ca2+ dependence of Δt (1/Δt vs. 1/Ca2+) in the absence of α-autoinhibition also yields that facilitation promotes utilization of external Ca2+. These results apparently imply that a rise in external Ca2+, in the presence of α-autoinhibition, augments the secretory response to electrical nerve stimulation mainly by promoting recruitment of active units (varicosities?), without markedly altering their `affinity' for facilitation. In the absence of autoinhibition (when all units are already recruited?), the results seem to imply that facilitation promotes depolarization-secretion coupling in each, by more efficient utilization of external Ca2+. 6. The pattern of interaction between α-autoinhibition and facilitation depends on the Ca2+ concentration in the medium. At or below the physiological level of Ca2+ in extracellular fluid (1·2 mm) it is `non-competitive', indicating that α-autoinhibition and facilitation act, at least in part, at separate targets under these conditions. At high (5·4 mm) external Ca2+ the pattern becomes almost purely `competitive', indicating that facilitation can, under suitable conditions, overcome all manifestations of α-autoinhibition. 7. The secretion evoked by electrical nerve stimulation (Δt per shock, at 1 or 10 Hz) increased with the strength of applied shocks, both when applied extra- or transmurally, in the presence or absence of α-autoinhibition. In the former case the rise in (Δt per shock) vs. (current strength) was hyperbolic, in the latter it followed a biphasic pattern. Double reciprocal plot analysis (1/Δt vs. 1/current) of the data yields a `non-competitive' pattern of interaction between facilitation or α-autoinhibition, and exogenous current, when stimulation was extramural. When it was transmural the pattern is `competitive'. The results seem to imply that hyperpolarization, or depolarization, of nerve terminals are major mechanisms whereby α-autoinhibition and facilitation, respectively, exert their effects on the secretory response to electrical nerve stimulation. 8. Neither activation of Na+, K+-ATPase, nor promotion of GCl appear to be critically involved in α-autoinhibition. Experiments with known blockers of GK (tetraethylammonium, 4-aminopyridine and Rb+) did not give support to the notion that promotion of K+ efflux is a mechanism whereby prejunctional α-adrenoceptors cause (hyperpolarization of nerve terminals and) autoinhibition of secretion. If α-autoinhibition does involve K+ channels in the nerve terminal membrane, then these must be different from the (voltage-sensitive) K+ channels blocked by the above mentioned inhibitors of K+ efflux. 9. The results are discussed in the context of a model that assumes that local control of noradrenaline secretion from noradrenergic nerves may be exerted both by control of invasion of terminals, and by control of depolarization—secretion coupling in each invaded varicosity. Under suitable conditions facilitation and α-autoinhibition may interact at both levels. It proposed that utilization of external Ca2+ plays a pivotal role for both, and that restriction of invasion of nerve terminal varicosities is the main effect of α-autoinhibition, while promotion of depolarization—secretion coupling is the main effect of facilitation, at physiological concentrations of Ca2+ in the medium. For the nerve the role of this dual control system is proposed to be to ensure `rotational' activation of varicosities, and for the effector cell of noradrenergic junctions, to increase the signal/noise ratio. PMID:6267264

Early Exposure to General Anesthesia Disrupts Spatial Organization of Presynaptic Vesicles in Nerve Terminals of the Developing Rat Subiculum.

PubMed

Lunardi, N; Oklopcic, A; Prillaman, M; Erisir, A; Jevtovic-Todorovic, V

2015-10-01

Exposure to general anesthesia (GA) during critical stages of brain development induces widespread neuronal apoptosis and causes long-lasting behavioral deficits in numerous animal species. Although several studies have focused on the morphological fate of neurons dying acutely by GA-induced developmental neuroapoptosis, the effects of an early exposure to GA on the surviving synapses remain unclear. The aim of this study is to study whether exposure to GA disrupts the fine regulation of the dynamic spatial organization and trafficking of synaptic vesicles in presynaptic terminals. We exposed postnatal day 7 (PND7) rat pups to a clinically relevant anesthetic combination of midazolam, nitrous oxide, and isoflurane and performed a detailed ultrastructural analysis of the synaptic vesicle architecture at presynaptic terminals in the subiculum of rats at PND 12. In addition to a significant decrease in the density of presynaptic vesicles, we observed a reduction of docked vesicles, as well as a reduction of vesicles located within 100 nm from the active zone, in animals 5 days after an initial exposure to GA. We also found that the synaptic vesicles of animals exposed to GA are located more distally with respect to the plasma membrane than those of sham control animals and that the distance between presynaptic vesicles is increased in GA-exposed animals compared to sham controls. We report that exposure of immature rats to GA during critical stages of brain development causes significant disruption of the strategic topography of presynaptic vesicles within the nerve terminals of the subiculum.

Somatic gain-of-function mutations in PIK3CA in patients with macrodactyly.

PubMed

Rios, Jonathan J; Paria, Nandina; Burns, Dennis K; Israel, Bonnie A; Cornelia, Reuel; Wise, Carol A; Ezaki, Marybeth

2013-02-01

Macrodactyly is a discrete congenital anomaly consisting of enlargement of all tissues localized to the terminal portions of a limb, typically within a 'nerve territory'. The classic terminology for this condition is 'lipofibromatous hamartoma of nerve' or Type I macrodactyly. The peripheral nerve, itself, is enlarged both in circumference and in length. It is not related to neurofibromatosis (NF1), nor is it associated with vascular malformations, such as in the recently reported CLOVES syndrome. The specific nerve pathophysiology in this form of macrodactyly has not been well described and a genetic etiology for this specific form of enlargement is unknown. To identify the genetic cause of macrodactyly, we used whole-exome sequencing to identify somatic mutations present in the affected nerve of a single patient. We confirmed a novel mutation in PIK3CA (R115P) present in the patient's affected nerve tissue but not in blood DNA. Sequencing PIK3CA exons identified gain-of-function mutations (E542K, H1047L or H1047R) in the affected tissue of five additional unrelated patients; mutations were absent in blood DNA available from three patients. Immunocytochemistry confirmed AKT activation in cultured cells from the nerve of a macrodactyly patient. Additionally, we found that the most abnormal structure within the involved nerve in a macrodactylous digit is the perineurium, with additional secondary effects on the axon number and size. Thus, isolated congenital macrodactyly is caused by somatic activation of the PI3K/AKT cell-signaling pathway and is genetically and biochemically related to other overgrowth syndromes.

Peptidergic innervation of the human male genital tract.

PubMed

Gu, J; Polak, J M; Probert, L; Islam, K N; Marangos, P J; Mina, S; Adrian, T E; McGregor, G P; O'Shaughnessy, D J; Bloom, S R

1983-08-01

Four peptides--vasoactive intestinal polypeptide, substance P, somatostatin and a peptide-like avian pancreatic polypeptide--have been found in nerves of the human male genitalia using highly sensitive and specific methods of immunocytochemistry and radioimmunoassay. Five other peptides (met-enkephalin, leu-enkephalin, neurotensin, bombesin and cholecystokinin-8) were absent. Vasoactive intestinal polypeptide was the most abundant peptide, its highest concentration being in the proximal corpus cavernosum. Immunoelectron microscopy localized this peptide to large (97 +/- 20 nm), round, electron-dense granules of p-type nerve terminals. Vasoactive intestinal polypeptide-immunoreactive neuronal cell bodies were found in the prostate gland and the root of the corpus cavernosum. Substance P immunoreactive material was present in smaller concentration and was mainly localized in nerves around the corpuscular receptors of the glans penis. Somatostatin immunoreactive nerves were associated mainly with the smooth muscle of the seminal vesicle and the vas deferens. When antiserum to avian pancreatic polypeptide was applied, certain nerves were stained, particularly in the vas deferens, the prostate gland and the seminal vesicle. However, chromatography detected no pure avian pancreatic polypeptide suggesting the presence of a structurally related substance, possibly neuropeptide Y, which cross-reacts with the avian pancreatic polypeptide antiserum. Similar distributions between vasoactive intestinal polypeptide-immunoreactive and acetylcholinesterase-positive nerves and between avian pancreatic polypeptide-immunoreactive and adrenergic nerves were observed. A general neuronal marker, neuron-specific enolase, was used to investigate the general pattern of the organ's innervation. The abundance and distribution patterns of these peptide-immunoreactive nerves indicate that they may play important roles in the male sexual physiology.

Distribution of CGRP and TRPV2 in Human Paranasal Sinuses.

PubMed

Sato, Tadasu; Sasahara, Nobuyuki; Kanda, Noriyuki; Sasaki, Yu; Yamaguma, Yu; Kokubun, Souichi; Yajima, Takehiro; Ichikawa, Hiroyuki

2017-01-01

Immunohistochemistry for protein gene product 9.5 (PGP 9.5), calcitonin gene-related peptide (CGRP) and the transient receptor potential cation channel subfamily V member 2 (TRPV2) was performed on human paranasal sinuses. It was found that in the paranasal sinuses, mucous membranes contain PGP 9.5-immunoreactive (PGP 9.5-IR) nerve fibers. Such nerve fibers terminated around large blood vessels as fine varicosities. Isolated PGP 9.5-IR nerve fibers were scattered beneath the epithelium. Glandular tissues were also innervated by PGP 9.5-IR nerve fibers. These fibers were numerous in the maxillary and ethmoid sinuses, and relatively rare in the frontal and sphenoid sinuses. CGRP-IR nerve fibers were common in the maxillary sinus whereas TRPV2-IR nerve fibers were abundant in the ethmoid sinus. They were located around large blood vessels in the lamina propria. Many subepithelial nerve fibers contained TRPV2 immunoreactivity in the ethmoid sinus. CGRP- and TRPV2-IR nerve fibers were very infrequent in the frontal and sphenoid sinuses. In the human trigeminal ganglion (TG), sensory neurons contained CGRP or TRPV2 immunoreactivity. CGRP-IR TG neurons were more common than TRPV2-IR TG neurons. CGRP-IR TG neurons were of various cell body sizes, whereas TRPV2-IR TG neurons were mostly medium-to-large. In addition, human spinal and principal trigeminal sensory nuclei contained abundant CGRP- and TRPV2-IR varicosities. This study indicates that CGRP- and TRPV2-containing TG neurons probably innervate the paranasal sinus mucosae, and project into spinal and principal trigeminal sensory nuclei. © 2016 S. Karger AG, Basel.

Recruitment order of quadriceps motor units: femoral nerve vs. direct quadriceps stimulation.

PubMed

Rodriguez-Falces, Javier; Place, Nicolas

2013-12-01

To investigate potential differences in the recruitment order of motor units (MUs) in the quadriceps femoris when electrical stimulation is applied over the quadriceps belly versus the femoral nerve. M-waves and mechanical twitches were evoked using femoral nerve stimulation and direct quadriceps stimulation of gradually increasing intensity from 20 young, healthy subjects. Recruitment order was investigated by analysing the time-to-peak twitch and the time interval from the stimulus artefact to the M-wave positive peak (M-wave latency) for the vastus medialis (VM) and vastus lateralis (VL) muscles. During femoral nerve stimulation, time-to-peak twitch and M-wave latency decreased consistently (P < 0.05) with increasing stimulus intensity, whereas, during graded direct quadriceps stimulation, time-to-peak twitch and VL M-wave latency did not show a clear trend (P > 0.05). For the VM muscle, M-wave latency decreased with increasing stimulation level for both femoral nerve and direct quadriceps stimulation, whereas, for the VL muscle, the variation of M-wave latency with stimulus intensity was different for the two stimulation geometries (P < 0.05). Femoral nerve stimulation activated MUs according to the size principle, whereas the recruitment order during direct quadriceps stimulation was more complex, depending ultimately on the architecture of the peripheral nerve and its terminal branches below the stimulating electrodes for each muscle. For the VM, MUs were orderly recruited for both stimulation geometries, whereas, for the VL muscle, MUs were orderly recruited for femoral nerve stimulation, but followed no particular order for direct quadriceps stimulation.

The course of the superficial peroneal nerve in relation to the ankle position: anatomical study with ankle arthroscopic implications

PubMed Central

Golanó, Pau; Sierevelt, Inger N.; van Dijk, C. Niek

2010-01-01

Despite the fact that the superficial peroneal nerve is the only nerve in the human body that can be made visible; iatrogenic damage to this nerve is the most frequently reported complication in anterior ankle arthroscopy. One of the methods to visualize the nerve is combined ankle plantar flexion and inversion. In the majority of cases, the superficial peroneal nerve can be made visible. The portals for anterior ankle arthroscopy are however created with the ankle in the neutral or slightly dorsiflexed position and not in combined plantar flexion and inversion. The purpose of this study was to undertake an anatomical study to the course of the superficial peroneal nerve in different positions of the foot and ankle. We hypothesize that the anatomical localization of the superficial peroneal nerve changes with different foot and ankle positions. In ten fresh frozen ankle specimens, a window, only affecting the skin, was made at the level of the anterolateral portal for anterior ankle arthroscopy in order to directly visualize the superficial peroneal nerve, or if divided, its terminal branches. Nerve movement was assessed from combined 10° plantar flexion and inversion to 5° dorsiflexion, standardized by the Telos stress device. Also for the 4th toe flexion, flexion of all the toes and for skin tensioning possible nerve movement was determined. The mean superficial peroneal nerve movement was 2.4 mm to the lateral side when the ankle was moved from 10° plantar flexion and inversion to the neutral ankle position and 3.6 mm to the lateral side from 10° plantar flexion and inversion to 5° dorsiflexion. Both displacements were significant (P < 0.01). The nerve consistently moves lateral when the ankle is manoeuvred from combined plantar flexion and inversion to the neutral or dorsiflexed position. If visible, it is therefore advised to create the anterolateral portal medial from the preoperative marking, in order to prevent iatrogenic damage to the superficial peroneal nerve. PMID:20224993

Multiple sites and actions of gabapentin-induced relief of ongoing experimental neuropathic pain

PubMed Central

Bannister, Kirsty; Qu, Chaoling; Navratilova, Edita; Oyarzo, Janice; Xie, Jennifer Yanhua; King, Tamara; Dickenson, Anthony H.; Porreca, Frank

2017-01-01

Gabapentin is a first-line therapy for neuropathic pain but its mechanisms and sites of action remain uncertain. We investigated gabapentin-induced modulation of neuropathic pain following spinal nerve ligation (SNL) in rats. Intravenous or intrathecal gabapentin reversed evoked mechanical hypersensitivity, produced conditioned place preference (CPP) and dopamine release in the nucleus accumbens (NAc) selectively in SNL rats. Spinal gabapentin also significantly inhibited dorsal horn wide dynamic range (WDR) neuronal responses to a range of evoked stimuli in SNL rats. In contrast, gabapentin microinjected bilaterally into the rostral anterior cingulate cortex (rACC), produced CPP and elicited NAc dopamine release selectively in SNL rats but did not reverse tactile allodynia and had marginal effects on WDR neuronal activity. Moreover, blockade of endogenous opioid signaling in the rACC prevented intravenous gabapentin-induced CPP and NAc dopamine release but failed to block its inhibition of tactile allodynia. Gabapentin therefore can potentially act to produce its pain relieving effects by (a) inhibition of injury-induced spinal neuronal excitability, evoked hypersensitivity and ongoing pain and (b) selective supraspinal modulation of affective qualities of pain, without alteration of reflexive behaviors. Consistent with previous findings of pain relief from non-opioid analgesics, gabapentin requires engagement of rACC endogenous opioid circuits and downstream activation of mesolimbic reward circuits reflected in learned pain motivated behaviors. These findings support the partial separation of sensory and affective dimensions of pain in this experimental model and suggest that modulation of affective-motivational qualities of pain may be the preferential mechanism of gabapentin’s analgesic effects in patients. PMID:28832395

Bayesian analysis of the kinetics of quantal transmitter secretion at the neuromuscular junction.

PubMed

Saveliev, Anatoly; Khuzakhmetova, Venera; Samigullin, Dmitry; Skorinkin, Andrey; Kovyazina, Irina; Nikolsky, Eugeny; Bukharaeva, Ellya

2015-10-01

The timing of transmitter release from nerve endings is considered nowadays as one of the factors determining the plasticity and efficacy of synaptic transmission. In the neuromuscular junction, the moments of release of individual acetylcholine quanta are related to the synaptic delays of uniquantal endplate currents recorded under conditions of lowered extracellular calcium. Using Bayesian modelling, we performed a statistical analysis of synaptic delays in mouse neuromuscular junction with different patterns of rhythmic nerve stimulation and when the entry of calcium ions into the nerve terminal was modified. We have obtained a statistical model of the release timing which is represented as the summation of two independent statistical distributions. The first of these is the exponentially modified Gaussian distribution. The mixture of normal and exponential components in this distribution can be interpreted as a two-stage mechanism of early and late periods of phasic synchronous secretion. The parameters of this distribution depend on both the stimulation frequency of the motor nerve and the calcium ions' entry conditions. The second distribution was modelled as quasi-uniform, with parameters independent of nerve stimulation frequency and calcium entry. Two different probability density functions for the distribution of synaptic delays suggest at least two independent processes controlling the time course of secretion, one of them potentially involving two stages. The relative contribution of these processes to the total number of mediator quanta released depends differently on the motor nerve stimulation pattern and on calcium ion entry into nerve endings.

Fornix deep brain stimulation circuit effect is dependent on major excitatory transmission via the nucleus accumbens.

PubMed

Ross, Erika K; Kim, Joo Pyung; Settell, Megan L; Han, Seong Rok; Blaha, Charles D; Min, Hoon-Ki; Lee, Kendall H

2016-03-01

Deep brain stimulation (DBS) is a circuit-based treatment shown to relieve symptoms from multiple neurologic and neuropsychiatric disorders. In order to treat the memory deficit associated with Alzheimer's disease (AD), several clinical trials have tested the efficacy of DBS near the fornix. Early results from these studies indicated that patients who received fornix DBS experienced an improvement in memory and quality of life, yet the mechanisms behind this effect remain controversial. It is known that transmission between the medial limbic and corticolimbic circuits plays an integral role in declarative memory, and dysfunction at the circuit level results in various forms of dementia, including AD. Here, we aimed to determine the potential underlying mechanism of fornix DBS by examining the functional circuitry and brain structures engaged by fornix DBS. A multimodal approach was employed to examine global and local temporal changes that occur in an anesthetized swine model of fornix DBS. Changes in global functional activity were measured by functional MRI (fMRI), and local neurochemical changes were monitored by fast scan cyclic voltammetry (FSCV) during electrical stimulation of the fornix. Additionally, intracranial microinfusions into the nucleus accumbens (NAc) were performed to investigate the global activity changes that occur with dopamine and glutamate receptor-specific antagonism. Hemodynamic responses in both medial limbic and corticolimbic circuits measured by fMRI were induced by fornix DBS. Additionally, fornix DBS resulted in increases in dopamine oxidation current (corresponding to dopamine efflux) monitored by FSCV in the NAc. Finally, fornix DBS-evoked hemodynamic responses in the amygdala and hippocampus decreased following dopamine and glutamate receptor antagonism in the NAc. The present findings suggest that fornix DBS modulates dopamine release on presynaptic dopaminergic terminals in the NAc, involving excitatory glutamatergic input, and that the medial limbic and corticolimbic circuits interact in a functional loop. Copyright © 2016 Elsevier Inc. All rights reserved.

Muscarinic receptors acting at pre- and post-synaptic sites differentially regulate dopamine/DARPP-32 signaling in striatonigral and striatopallidal neurons.

PubMed

Kuroiwa, Mahomi; Hamada, Miho; Hieda, Eriko; Shuto, Takahide; Sotogaku, Naoki; Flajolet, Marc; Snyder, Gretchen L; Hendrick, Joseph P; Fienberg, Allen; Nishi, Akinori

2012-12-01

Muscarinic receptors, activated by acetylcholine, play critical roles in the functional regulation of medium spiny neurons in the striatum. However, the muscarinic receptor signaling pathways are not fully elucidated due to their complexity. In this study, we investigated the function of muscarinic receptors in the striatum by monitoring DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of M(r) 32 kDa) phosphorylation at Thr34 (the PKA-site) using mouse striatal slices. Treatment of slices with a non-selective muscarinic receptor agonist, oxotremorine (10 μM), rapidly and transiently increased DARPP-32 phosphorylation. The increase in DARPP-32 phosphorylation was completely abolished either by a dopamine D(1) receptor antagonist (SCH23390), tetrodotoxin, genetic deletion of M5 receptors, muscarinic toxins for M1 and M4 receptors, or 6-hydroxydopamine lesioning of dopaminergic neurons, whereas it was enhanced by nicotine. Analysis in D(1)-DARPP-32-Flag/D(2)-DARPP-32-Myc transgenic mice revealed that oxotremorine increases DARPP-32 phosphorylation selectively in D(1)-type/striatonigral, but not in D(2)-type/striatopallidal, neurons. When D(1) and D(2) receptors were blocked by selective antagonists to exclude the effects of released dopamine, oxotremorine increased DARPP-32 Thr34 phosphorylation only in D(2)-type/striatopallidal neurons. This increase required activation of M1 receptors and was dependent upon adenosine A(2A) receptor activity. The results demonstrate that muscarinic receptors, especially M5 receptors, act at presynaptic dopaminergic terminals, regulate the release of dopamine in cooperation with nicotinic receptors, and activate D(1) receptor/DARPP-32 signaling in the striatonigral neurons. Muscarinic M1 receptors expressed in striatopallidal neurons interact with adenosine A(2A) receptors and activate DARPP-32 signaling. Copyright © 2012 Elsevier Ltd. All rights reserved.

Prostaglandin action on transmitter release of adrenergic neuroeffector junctions.

PubMed

Hedqvist, P

1976-01-01

The results presented here indicate that 1. The inhibitory action of the endoperoxides on NE release can be at least partly explained in terms of formation of degradation products, presumably mainly PGE2. 2. PGA2 is less active and the PG analogue 16,16-dimethyl-PGE2 more active than PGEs on transmitter release from adrenergic nerves. 3. PGF2alpha seems to enhance vascular responses to renal nerve activity solely by a postjunctional action. 4. PG synthesis inhibition augments NE turnover in a number of rat organs, thereby increasing the probability of PGs being involved in the control of adrenergic neurotransmission in vivo. 5. Prolongation of the duration of the impulse and action potential counteracts the effect of PGE on NE release, thereby strengthening the view that PGs operate on NE release from adrenergic nerve terminals by interfering with Ca2+ influx.

Surgical anatomy of the hypoglossal nerve: A new classification system for selective upper airway stimulation.

PubMed

Heiser, Clemens; Knopf, Andreas; Hofauer, Benedikt

2017-12-01

Selective upper airway stimulation (UAS) has shown effectiveness in treating patients with obstructive sleep apnea (OSA). The terminating branches of the hypoglossal nerve show a wide complexity, requiring careful discernment of a functional breakpoint between branches for inclusion and exclusion from the stimulation cuff electrode. The purpose of this study was to describe and categorize the topographic phenotypes of these branches. Thirty patients who received an implant with selective UAS from July 2015 to June 2016 were included. All implantations were recorded using a microscope and resultant tongue motions were captured perioperatively for comparison. Eight different variations of the branches were encountered and described, both in a tabular numeric fashion and in pictorial schema. The examinations showed the complex phenotypic surgical anatomy of the hypoglossal nerve. A schematic classification system has been developed to help surgeons identify the optimal location for cuff placement in UAS. © 2017 Wiley Periodicals, Inc.

Extra- and intramuscular nerve supply of the muscles of the anterior antebrachial compartment: applications for selective neurotomy and for botulinum toxin injection.

PubMed

Lepage, D; Parratte, B; Tatu, L; Vuiller, F; Monnier, G

2005-12-01

Hypertonia of the upper limb due to spasticity causes pronation of the forearm and flexion of wrist and fingers. Nowadays this spasticity is often treated with injections of botulinum toxin and sometimes with selective fascicular neurotomy. To correctly perform this microsurgical technique, it is necessary to get precise knowledge of the extramuscular nerve branching in order to be better able to select the motor branches which supply the muscles involved in spasticity. The same knowledge is required for botulinum toxin injections which must be made as near as possible to the zones where intramuscular nerve endings are the densest, which is also where neuromuscular junctions are the most numerous. Thus, it is necessary to better know these zones, but their knowledge remains today imprecise. The muscles of the anterior compartment of 30 forearms were dissected, first macroscopically, then microscopically, to study the extra- and intramuscular nerve supply and the distribution of terminal nerve ramifications. The results were then linked to surface topographical landmarks to indicate the precise location of motor branches for each muscle with the aim of proposing appropriate surgical approaches for selective neurotomies. Then for each muscle, the zones with the highest density of nerve endings were divided into segments, thus determining the optimal zones for botulinim toxin injections.

Capsaicin modulates acetylcholine release at the myoneural junction.

PubMed

Thyagarajan, Baskaran; Potian, Joseph G; Baskaran, Padmamalini; McArdle, Joseph J

2014-12-05

Transient receptor potential (TRP) proteins are non-selective cation channel proteins that are expressed throughout the body. Previous studies demonstrated the expression of TRP Vanilloid 1 (TRPV1), capsaicin (CAP) receptor, in sensory neurons. Recently, we reported TRPV1 expression in mouse motor nerve terminals [MNTs; (Thyagarajan et al., 2009)], where we observed that CAP protected MNTs from botulinum neurotoxin A (BoNT/A). Phrenic nerve diaphragm nerve muscle preparations (NMP) isolated from isoflurane anesthetized adult mice were analyzed for twitch tension, spontaneous (mEPCs) and nerve stimulus evoked (EPCs) acetylcholine release. When acutely applied to isolated NMP, CAP produced a concentration-dependent decline of twitch tension and produced a significant decline in the amplitude of EPCs and quantal content without any effect on the mEPCs. The suppression of nerve stimulus evoked acetylcholine release by CAP was antagonized by capsazepine (CPZ), a TRPV1 antagonist. CAP did not suppress phrenic nerve stimulus evoked acetylcholine release in TRPV1 knockout mice. Also, CAP treatment, in vitro, interfered with the localization of adapter protein 2 in cholinergic Neuro 2a cells. Wortmannin, (WMN; non-selective phosphoinositol kinase inhibitor), mimicked the effects of CAP by inhibiting the acetylcholine exocytosis. Our data suggest that TRPV1 proteins expressed at the MNT are coupled to the exo-endocytic mechanisms to regulate neuromuscular functions. Copyright © 2014 Elsevier B.V. All rights reserved.

[Clinical and electrophysiological findings in carpal tunnel syndrome].

PubMed

Kohara, Nobuo

2007-11-01

Carpal tunnel syndrome (CTS) is the most common nerve entrapment disorder. The clinical features of CTS are variable, but usually include pain and paresthesia in the thumb, first two fingers, and the radial-half of the ring finger. Paresthesia and sensory deficits might involve the entire palm area in some cases. Pain frequently radiate proximally into the forearm, and occasionally to the shoulder. Many patients experience pain at night and are awakened by abnormal sensations. Shaking hand relief the symptom. The two classic tests for nerve compression at the wrist are the Tinel test and the Phalen maneuver, which diagnostic value is limited. Golden standard for the diagnosis is the combination of the clinical findings and the electrophysiological study. Routine median nerve conduction study is valuable. Prolonged terminal latency of motor or sensory nerve would be found in most CTS hands. If the routine study showed equivocal, more sensitive methods are needed. Those include segmental sensory conduction study across the carpal tunnel by median stimulation at midpalm, a comparison of median and ulnar sensory nerve latencies at ring finger and a comparison of median and radial sensory nerve latencies at thumb. A difference between the median motor latency to the second lumbrical and the ulnar motor latency to the interossei muscles has also diagnostic value in some cases. In addition, inching method can localized the compression site. Using these techniques, the diagnosis of CTS would become more reliable.

Extracellular truncated tau causes early presynaptic dysfunction associated with Alzheimer’s disease and other tauopathies

PubMed Central

Florenzano, Fulvio; Veronica, Corsetti; Ciasca, Gabriele; Ciotti, Maria Teresa; Pittaluga, Anna; Olivero, Gunedalina; Feligioni, Marco; Iannuzzi, Filomena; Latina, Valentina; Maria Sciacca, Michele Francesco; Sinopoli, Alessandro; Milardi, Danilo; Pappalardo, Giuseppe; Marco, De Spirito; Papi, Massimiliano; Atlante, Anna; Bobba, Antonella; Borreca, Antonella; Calissano, Pietro; Amadoro, Giuseppina

2017-01-01

The largest part of tau secreted from AD nerve terminals and released in cerebral spinal fluid (CSF) is C-terminally truncated, soluble and unaggregated supporting potential extracellular role(s) of NH2 -derived fragments of protein on synaptic dysfunction underlying neurodegenerative tauopathies, including Alzheimer’s disease (AD). Here we show that sub-toxic doses of extracellular-applied human NH2 tau 26-44 (aka NH 2 htau) -which is the minimal active moiety of neurotoxic 20-22kDa peptide accumulating in vivo at AD synapses and secreted into parenchyma- acutely provokes presynaptic deficit in K+ -evoked glutamate release on hippocampal synaptosomes along with alteration in local Ca2+ dynamics. Neuritic dystrophy, microtubules breakdown, deregulation in presynaptic proteins and loss of mitochondria located at nerve endings are detected in hippocampal cultures only after prolonged exposure to NH 2 htau. The specificity of these biological effects is supported by the lack of any significant change, either on neuronal activity or on cellular integrity, shown by administration of its reverse sequence counterpart which behaves as an inactive control, likely due to a poor conformational flexibility which makes it unable to dynamically perturb biomembrane-like environments. Our results demonstrate that one of the AD-relevant, soluble and secreted N-terminally truncated tau forms can early contribute to pathology outside of neurons causing alterations in synaptic activity at presynaptic level, independently of overt neurodegeneration. PMID:29029390

P/Q-type calcium channels activate neighboring calcium-dependent potassium channels in mouse motor nerve terminals.

PubMed

Protti, D A; Uchitel, O D

1997-08-01

The identity of the voltage-dependent calcium channels (VDCC), which trigger the Ca2+-gated K+ currents (IK(Ca)) in mammalian motor nerve terminals, was investigated by means of perineurial recordings. The effects of Ca2+ chelators with different binding kinetics on the activation of IK(Ca) were also examined. The calcium channel blockers of the P/Q family, omega-agatoxin IVA (omega-Aga-IVA) and funnel-web spider toxin (FTX), have been shown to exert a strong blocking effect on IK(Ca). In contrast, nitrendipine and omega-conotoxin GVIA (omega-CgTx) did not affect the Ca2+-activated K+ currents. The intracellular action of the fast Ca2+ buffers BAPTA and DM-BAPTA prevented the activation of the IK(Ca), while the slow Ca2+ buffer EGTA was ineffective at blocking it. These data indicate that P/Q-type VDCC mediate the Ca2+ influx which activates IK(Ca). The spatial association between Ca2+ and Ca2+-gated K+ channels is discussed, on the basis of the differential effects of the fast and slow Ca2+ chelators.

Synapsin I is associated with cholinergic nerve terminals in the electric organs of Torpedo, Electrophorus, and Malapterurus and copurifies with Torpedo synaptic vesicles.

PubMed

Volknandt, W; Naito, S; Ueda, T; Zimmermann, H

1987-08-01

Using an affinity-purified monospecific polyclonal antibody against bovine brain synapsin I, the distribution of antigenically related proteins was investigated in the electric organs of the three strongly electric fish Torpedo marmorata, Electrophorus electricus, Malapterurus electricus and in the rat diaphragm. On application of indirect fluorescein isothiocyanate-immunofluorescence and using alpha-bungarotoxin for identification of synaptic sites, intense and very selective staining of nerve terminals was found in all of these tissues. Immunotransfer blots of tissue homogenates revealed specific bands whose molecular weights are similar to those of synapsin Ia and synapsin Ib. Moreover, synapsin I-like proteins are still attached to the synaptic vesicles that were isolated in isotonic glycine solution from Torpedo electric organ by density gradient centrifugation and chromatography on Sephacryl-1000. Our results suggest that synapsin I-like proteins are also associated with cholinergic synaptic vesicles of electric organs and that the electric organ may be an ideal source for studying further the functional and molecular properties of synapsin.

Micromolar-Affinity Benzodiazepine Receptors Regulate Voltage-Sensitive Calcium Channels in Nerve Terminal Preparations

NASA Astrophysics Data System (ADS)

Taft, William C.; Delorenzo, Robert J.

1984-05-01

Benzodiazepines in micromolar concentrations significantly inhibit depolarization-sensitive Ca2+ uptake in intact nerve-terminal preparations. Benzodiazepine inhibition of Ca2+ uptake is concentration dependent and stereospecific. Micromolar-affinity benzodiazepine receptors have been identified and characterized in brain membrane and shown to be distinct from nanomolar-affinity benzodiazepine receptors. Evidence is presented that micromolar, and not nanomolar, benzodiazepine binding sites mediate benzodiazepine inhibition of Ca2+ uptake. Irreversible binding to micromolar benzodiazepine binding sites also irreversibly blocked depolarization-dependent Ca2+ uptake in synaptosomes, indicating that these compounds may represent a useful marker for identifying the molecular components of Ca2+ channels in brain. Characterization of benzodiazepine inhibition of Ca2+ uptake demonstrates that these drugs function as Ca2+ channel antagonists, because benzodiazepines effectively blocked voltage-sensitive Ca2+ uptake inhibited by Mn2+, Co2+, verapamil, nitrendipine, and nimodipine. These results indicate that micromolar benzodiazepine binding sites regulate voltage-sensitive Ca2+ channels in brain membrane and suggest that some of the neuronal stabilizing effects of micromolar benzodiazepine receptors may be mediated by the regulation of Ca2+ conductance.

Ferulic Acid Suppresses Glutamate Release Through Inhibition of Voltage-Dependent Calcium Entry in Rat Cerebrocortical Nerve Terminals

PubMed Central

Lin, Tzu Yu; Lu, Cheng Wei; Huang, Shu-Kuei

2013-01-01

Abstract This study investigated the effects and possible mechanism of ferulic acid, a naturally occurring phenolic compound, on endogenous glutamate release in the nerve terminals of the cerebral cortex in rats. Results show that ferulic acid inhibited the release of glutamate evoked by the K+ channel blocker 4-aminopyridine (4-AP). The effect of ferulic acid on the evoked glutamate release was prevented by chelating the extracellular Ca2+ ions, but was insensitive to the glutamate transporter inhibitor DL-threo-beta-benzyl-oxyaspartate. Ferulic acid suppressed the depolarization-induced increase in a cytosolic-free Ca2+ concentration, but did not alter 4-AP–mediated depolarization. Furthermore, the effect of ferulic acid on evoked glutamate release was abolished by blocking the Cav2.2 (N-type) and Cav2.1 (P/Q-type) channels, but not by blocking ryanodine receptors or mitochondrial Na+/Ca2+ exchange. These results show that ferulic acid inhibits glutamate release from cortical synaptosomes in rats through the suppression of presynaptic voltage-dependent Ca2+ entry. PMID:23342970

Acetylcholine receptor distribution and synapse elimination at the developing neuromuscular junction of mdx mice.

PubMed

Minatel, Elaine; Neto, Humberto Santo; Marques, Maria Julia

2003-11-01

The pattern of innervation of the vertebrate neuromuscular junction is established during early development, when junctions go from multiple to single innervation in the phenomenon of synapse elimination, suggesting that changes at the molecular level in the postsynaptic cell lead to the removal of nerve terminals. The mdx mouse is deficient in dystrophin and associated proteins that are part of the postsynaptic cytoskeleton. We used rhodamine-alpha-bungarotoxin and anti-neurofilament IgG-FITC to stain acetylcholine receptors and nerve terminals of the sternomastoid muscle during postnatal development in mdx and control C57BL/10 mice. Using fluorescence confocal microscopy, we observed that, 7 days after birth, 86.7% of the endplates of mdx mice were monoinnervated (n = 200) compared with 41.4% in control mice (n = 200). By the end of the second postnatal week, all endplates were innervated singly (100% mdx and 94.7% controls, n = 200 per group). These results show that dystrophic fibers achieve single innervation earlier, perhaps because dystrophin or a normal cytoskeletal complex is implicated in this phenomenon.

Micromolar-affinity benzodiazepine receptors regulate voltage-sensitive calcium channels in nerve terminal preparations.

PubMed Central

Taft, W C; DeLorenzo, R J

1984-01-01

Benzodiazepines in micromolar concentrations significantly inhibit depolarization-sensitive Ca2+ uptake in intact nerve-terminal preparations. Benzodiazepine inhibition of Ca2+ uptake is concentration dependent and stereospecific. Micromolar-affinity benzodiazepine receptors have been identified and characterized in brain membrane and shown to be distinct from nanomolar-affinity benzodiazepine receptors. Evidence is presented that micromolar, and not nanomolar, benzodiazepine binding sites mediate benzodiazepine inhibition of Ca2+ uptake. Irreversible binding to micromolar benzodiazepine binding sites also irreversibly blocked depolarization-dependent Ca2+ uptake in synaptosomes, indicating that these compounds may represent a useful marker for identifying the molecular components of Ca2+ channels in brain. Characterization of benzodiazepine inhibition of Ca2+ uptake demonstrates that these drugs function as Ca2+ channel antagonists, because benzodiazepines effectively blocked voltage-sensitive Ca2+ uptake inhibited by Mn2+, Co2+, verapamil, nitrendipine, and nimodipine. These results indicate that micromolar benzodiazepine binding sites regulate voltage-sensitive Ca2+ channels in brain membrane and suggest that some of the neuronal stabilizing effects of micromolar benzodiazepine receptors may be mediated by the regulation of Ca2+ conductance. PMID:6328498

Lycopene depresses glutamate release through inhibition of voltage-dependent Ca2+ entry and protein kinase C in rat cerebrocortical nerve terminals.

PubMed

Lu, Cheng-Wei; Hung, Chi-Feng; Jean, Wei-Horng; Lin, Tzu-Yu; Huang, Shu-Kuei; Wang, Su-Jane

2018-05-01

Lycopene is a natural dietary carotenoid that was reported to exhibit a neuroprotective profile. Considering that excitotoxicity and cell death induced by glutamate are involved in many brain disorders, the effect of lycopene on glutamate release in rat cerebrocortical nerve terminals and the possible mechanism involved in such effect was investigated. We observed here that lycopene inhibited 4-aminopyridine (4-AP)-evoked glutamate release and intrasynaptosomal Ca 2+ concentration elevation. The inhibitory effect of lycopene on 4-AP-evoked glutamate release was markedly reduced in the presence of the Ca v 2.2 (N-type) and Ca v 2.1 (P/Q-type) channel blocker ω-conotoxin MVIIC, but was insensitive to the intracellular Ca 2+ -release inhibitors dantrolene and CGP37157. Furthermore, in the presence of the protein kinase C inhibitors GF109203X and Go6976, the action of lycopene on evoked glutamate release was prevented. These results are the first to suggest that lycopene inhibits glutamate release from rat cortical synaptosomes by suppressing presynaptic Ca 2+ entry and protein kinase C activity.

Innervation pattern of the preocular human central retinal artery.

PubMed

Bergua, Antonio; Kapsreiter, Markus; Neuhuber, Winfried L; Reitsamer, Herbert A; Schrödl, Falk

2013-05-01

The central retinal artery (CRA) is the main vessel for inner retinal oxygen and nutrition supply. While the intraocular branches lack autonomic innervation, the innervation pattern of the extra-ocular part of this vessel along its course within the optic nerve is poorly investigated. This part however is essential for maintenance of retinal blood supply, in physiological and pathological conditions. Therefore, the aim of this study was the characterization of the autonomic innervation of the preocular CRA in humans with morphological methods. Meeting the Declaration of Helsinki, eyes of body or cornea donors were processed for single or double immunohistochemistry against tyrosine hydroxilase (TH), dopamine-β-hydroxylase (DBH), choline acetyl-transferase (ChAT), vesicular acetylcholine transporter (VAChT), neuronal nitric oxide synthase (nNOS), calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP), and cytochemistry for NADPH-diaphorase (NADPH-d). For documentation, light-, fluorescence-, and confocal laser-scanning microscopy were used. TH and DBH immunoreactive nerve fibres were detected in the CRA vessel wall, although a distinct perivascular plexus was missing. Further, nerve fibres immunoreactive for ChAT and VAChT were found, while CGRP, SP, and VIP were not detected. NADPH-d staining revealed scattered nerve fibres in the adventitia of the CRA and in close vicinity; however, nNOS-immunostaining could not confirm this finding. The CRA receives adrenergic and cholinergic innervations, indicating sympathetic and parasympathetic components, respectively. Remarkably, a peptidergic primary afferent innervation was missing. Since clinical results suggest an autoregulation of intraretinal vessels, further studies are needed to clarify the impact of CRA innervation for retinal perfusion. Copyright © 2012 Elsevier Ltd. All rights reserved.

Protection but maintained dysfunction of nigral dopaminergic nerve cell bodies and striatal dopaminergic terminals in MPTP-lesioned mice after acute treatment with the mGluR5 antagonist MPEP.

PubMed

Aguirre, Jose A; Kehr, Jan; Yoshitake, Takashi; Liu, Fang-Ling; Rivera, Alicia; Fernandez-Espinola, Sergio; Andbjer, Beth; Leo, Giuseppina; Medhurst, Andrew D; Agnati, Luigi F; Fuxe, Kjell

2005-02-08

The mGluR5 antagonist MPEP was used to study the role of mGluR5 in MPTP-induced injury of the nigrostriatal DA neurons. The findings indicate that acute blockade of mGluR5 may result in neuroprotective actions against MPTP neurotoxicity on nigral DA cell bodies and striatal DA terminals using stereological analysis of TH immunoreactivity and microdensitometry. Biochemical analysis showed no restoration of DA levels and metabolism indicating a maintained reduction of DA transmission.

Cholinergic Axons in the Rat Ventral Tegmental Area Synapse Preferentially onto Mesoaccumbens Dopamine Neurons

PubMed Central

Omelchenko, Natalia; Sesack, Susan R.

2008-01-01

Cholinergic afferents to the ventral tegmental area (VTA) contribute substantially to the regulation of motivated behaviors and the rewarding properties of nicotine. These actions are believed to involve connections with dopamine (DA) neurons projecting to the nucleus accumbens (NAc). However, this direct synaptic link has never been investigated, nor is it known whether cholinergic inputs innervate other populations of DA and GABA neurons, including those projecting to the prefrontal cortex (PFC). We addressed these questions using electron microscopic analysis of retrograde tract-tracing and immunocytochemistry for the vesicular acetylcholine transporter (VAChT) and for tyrosine hydroxylase (TH) and GABA. In tissue labeled for TH, VAChT+ terminals frequently synapsed onto DA mesoaccumbens neurons but only seldom contacted DA mesoprefrontal cells. In tissue labeled for GABA, one third of VAChT+ terminals innervated GABA-labeled dendrites, including both mesoaccumbens and mesoprefrontal populations. VAChT+ synapses onto DA and mesoaccumbens neurons were more commonly of the asymmetric (presumed excitatory) morphological type, whereas VAChT+ synapses onto GABA cells were more frequently symmetric (presumed inhibitory or modulatory). These findings suggest that cholinergic inputs to the VTA mediate complex synaptic actions, with a major portion of this effect likely to involve an excitatory influence on DA mesoaccumbens neurons. As such, the results suggest that natural and drug rewards operating through cholinergic afferents to the VTA have a direct synaptic link to the mesoaccumbens DA neurons that modulate approach behaviors. PMID:16385486

Structural and Functional Characterization of the Interaction of Snapin with the Dopamine Transporter: Differential Modulation of Psychostimulant Actions.

PubMed

Erdozain, Amaia M; De Gois, Stéphanie; Bernard, Véronique; Gorgievski, Victor; Pietrancosta, Nicolas; Dumas, Sylvie; Macedo, Carlos E; Vanhoutte, Peter; Ortega, Jorge E; Meana, J Javier; Tzavara, Eleni T; Vialou, Vincent; Giros, Bruno

2018-04-01

The importance of dopamine (DA) neurotransmission is emphasized by its direct implication in several neurological and psychiatric disorders. The DA transporter (DAT), target of psychostimulant drugs, is the key protein that regulates spatial and temporal activity of DA in the synaptic cleft via the rapid reuptake of DA into the presynaptic terminal. There is strong evidence suggesting that DAT-interacting proteins may have a role in its function and regulation. Performing a two-hybrid screening, we identified snapin, a SNARE-associated protein implicated in synaptic transmission, as a new binding partner of the carboxyl terminal of DAT. Our data show that snapin is a direct partner and regulator of DAT. First, we determined the domains required for this interaction in both proteins and characterized the DAT-snapin interface by generating a 3D model. Using different approaches, we demonstrated that (i) snapin is expressed in vivo in dopaminergic neurons along with DAT; (ii) both proteins colocalize in cultured cells and brain and, (iii) DAT and snapin are present in the same protein complex. Moreover, by functional studies we showed that snapin produces a significant decrease in DAT uptake activity. Finally, snapin downregulation in mice produces an increase in DAT levels and transport activity, hence increasing DA concentration and locomotor response to amphetamine. In conclusion, snapin/DAT interaction represents a direct link between exocytotic and reuptake mechanisms and is a potential target for DA transmission modulation.

The discovery of the pressor effect of DOPS and its blunting by decarboxylase inhibitors.

PubMed

Kaufmann, H

2006-01-01

In the 1950s it was found that an artificial aminoacid, 3,4-threo-dihydroxyphenylserine (DOPS), was converted to norepinephrine (NE) in a single step by the enzyme L-aromatic amino acid decarboxylase (AADC), bypassing the need for the rate limiting enzyme dopamine beta hydroxylase. Trying to replicate the success of dihydroxyphenylalanine (DOPA) in the treatment of Parkinson disease, treatment with DOPS was attempted in patients with autonomic failure who have impaired NE release. DOPS improved orthostatic hypotension in patients with familial amyloid polyneuropathy, congenital deficiency of dopamine beta hydroxylase, pure autonomic failure and multiple system atrophy. DOPS pressor effect is due to its conversion to NE outside the central nervous system because concomitant administration of carbidopa, an inhibitor of AADC that does not cross the blood-brain barrier, blunted both the increase in plasma NE and the pressor response. DOPS pressor response is not dependent on intact sympathetic terminals because its conversion to NE also occurs in non-neuronal tissues.

In vivo dopaminergic and serotonergic dysfunction in DCTN1 gene mutation carriers

PubMed Central

Felicio, Andre C.; Dinelle, Katherine; Agarwal, Pankaj A.; McKenzie, Jessamyn; Heffernan, Nicole; Road, Jeremy D.; Appel-Cresswell, Silke; Wszolek, Zbigniew K.; Farrer, Matthew J.; Schulzer, Michael; Sossi, Vesna; Stoessl, A. Jon

2014-01-01

Introduction We have used positron emission tomography (PET) to assess dopaminergic and serotonergic terminal density in three subjects carrying a mutation in the DCT1 gene, two clinically affected with Perry syndrome. Methods All subjects had brain imaging using 18F-6-fluoro-L-dopa (FDOPA, dopamine synthesis and storage), (+)-11C-dihydrotetrabenazine (DTBZ, vesicular monoamine transporter type 2), and 11C-raclopride (RAC, dopamine D2/D3 receptors). One subject also underwent PET with 11C-3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)-benzonitrile (DASB, serotonin transporter). Results FDOPA-PET and DTBZ-PET in the affected individuals showed a reduction of striatal tracer uptake. Also, RAC-PET showed higher uptake in these area. DASB-PET showed significant uptake changes in left orbitofrontal cortex, bilateral anterior insula, left dorsolateral prefrontal cortex, left orbitofrontal cortex, left posterior cingulate cortex, left caudate and left ventral striatum. Conclusions Our data showed evidence of both striatal dopaminergic and widespread cortical/subcortical serotonergic dysfunctions in individuals carrying a mutation in the DCTN1 gene. PMID:24797316

Novel and High Affinity 2-[(Diphenylmethyl)sulfinyl]acetamide (Modafinil) Analogues as Atypical Dopamine Transporter Inhibitors

PubMed Central

Cao, Jianjing; Slack, Rachel D.; Bakare, Oluyomi M.; Burzynski, Caitlin; Rais, Rana; Slusher, Barbara S.; Kopajtic, Theresa; Bonifazi, Alessandro; Ellenberger, Michael P.; Yano, Hideaki; He, Yi; Bi, Guo-Hua; Xi, Zheng-Xiong; Loland, Claus J.; Newman, Amy Hauck

2016-01-01

The development of pharmacotherapeutic treatments of psychostimulant abuse has remained a challenge, despite significant efforts made towards relevant mechanistic targets, such as the dopamine transporter (DAT). The atypical DAT inhibitors have received attention due to their promising pharmacological profiles in animal models of cocaine and methamphetamine abuse. Herein we report a series of modafinil analogues that have an atypical DAT inhibitor profile. We extended SAR by chemically manipulating the oxidation states of the sulfoxide and the amide functional groups, halogenating the phenyl rings, and/or functionalizing the terminal nitrogen with substituted piperazines, resulting in several novel leads such as 11b, which demonstrated high DAT affinity (Ki=2.5 nM) and selectivity without producing concomitant locomotor stimulation in mice, as compared to cocaine. These results are consistent with an atypical DAT inhibitor profile and suggest that 11b may be a potential lead for development as a psychostimulant abuse medication. PMID:27933960

Joseph Rudinger memorial lecture: Unexpected functions of angiotensin converting enzyme, beyond its enzymatic activity.

PubMed

Martinez, Jean

2017-10-01

Angiotensin converting enzyme (ACE) is a well-known enzyme, largely studied for its action on hypertension, as it produces angiotensin II from angiotensin I. This paper describes two original behaviours of ACE. We showed that ACE could hydrolyse gastrin, a neuropeptide from the gastrointestinal tract, releasing the C-terminal amidated dipeptide H-Asp-Phe-NH 2 . This dipeptide is believed to be involved in the gastrin-induced acid secretion in the stomach. This hypothetic mechanism of action of gastrin resulted in a strategy to rationally design gastrin receptor antagonists. Beyond, we showed that the brain renin angiotensin system (RAS) could be activated by a new characterized peptide named acein, resulting in stimulation of dopamine release within the striatum. This new and original 'receptor-like' activity for brain membrane-bound ACE is quite significant taking into account the role of dopamine in the brain, particularly in neurodegenerative diseases. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.