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Sample records for 5-hydroxytryptamine dorsal raphe

  1. Lack of 5-hydroxytryptamine1A-mediated inhibition of adenylyl cyclase in dorsal raphe of male and female rats.

    PubMed

    Clarke, W P; Yocca, F D; Maayani, S

    1996-06-01

    In the rat hippocampus, 5-hydroxytryptamine (5-HT)1A receptors couple to two independent effector mechanisms, the inhibition of adenylyl cyclase activity and the opening of a K+ channel. In the dorsal raphe, 5-HT1A receptors also open K+ channels; however, coupling to adenylyl cyclase has not been demonstrated. In this study, the selective 5-HT1A agonists (+/-)- 8-hydroxy-2-(di-n-propylamino)tetralin, (R+)-8-hydroxy-2-(di-n-propylamino)tetralin and dipropyl-5-carboxamidotryptamine, did not inhibit forskolin-stimulated adenylyl cyclase (FSAC) activity in raphe region homogenates, although these drugs were efficacious in hippocampal homogenates. Other 5-HT1A agonists, NAN-190, BMY-7378, buspirone and gepirone, were also ineffective in raphe region homogenates. Estrogen-treatment of ovariectomized female rats, which is known to enhance 5-HT1A-mediated inhibition of FSAC in the hippocampus, did not promote the action of 5-HT1A agonists. Nor did activation of 5-HT1A receptors stimulate basal adenylyl cyclase activity in raphe homogenates as it does in the hippocampus. FSAC activity was inhibited in raphe region homogenates by activation of adenosine A1 or gamma-aminobutyric acidB receptors or by direct activation of the inhibitor G-protein, Gi, with guanyl-5'-6'-imidodiphosphate, indicating that the raphe homogenates have the biochemical machinery for inhibition of FSAC. High affinity binding studies showed that, in raphe homogenates, 5-HT1A receptors were expressed at a density comparable to that of adenosine A1 receptors and that they were coupled to G-proteins. It should be noted that our failure to observe 5-HT1A-mediated inhibition of adenylyl cyclase in the raphe does not prove that such coupling does not exist. However, a lack of 5-HT1A receptor coupling to adenylyl cyclase in the raphe would support contentions that coupling of the 5-HT1A receptor to adenylyl cyclase may be independent of its coupling to the K+ channel and that there may be distinct differences

  2. Corticotropin-releasing factor increases GABA synaptic activity and induces inward current in 5-hydroxytryptamine dorsal raphe neurons.

    PubMed

    Kirby, Lynn G; Freeman-Daniels, Emily; Lemos, Julia C; Nunan, John D; Lamy, Christophe; Akanwa, Adaure; Beck, Sheryl G

    2008-11-26

    Stress-related psychiatric disorders such as anxiety and depression involve dysfunction of the serotonin [5-hydroxytryptamine (5-HT)] system. Previous studies have found that the stress neurohormone corticotropin-releasing factor (CRF) inhibits 5-HT neurons in the dorsal raphe nucleus (DRN) in vivo. The goals of the present study were to characterize the CRF receptor subtypes (CRF-R1 and -R2) and cellular mechanisms underlying CRF-5-HT interactions. Visualized whole-cell patch-clamp recording techniques in brain slices were used to measure spontaneous or evoked GABA synaptic activity in DRN neurons of rats and CRF effects on these measures. CRF-R1 and -R2-selective agonists were bath applied alone or in combination with receptor-selective antagonists. CRF increased presynaptic GABA release selectively onto 5-HT neurons, an effect mediated by the CRF-R1 receptor. CRF increased postsynaptic GABA receptor sensitivity selectively in 5-HT neurons, an effect to which both receptor subtypes contributed. CRF also had direct effects on DRN neurons, eliciting an inward current in 5-HT neurons mediated by the CRF-R2 receptor and in non-5-HT neurons mediated by the CRF-R1 receptor. These results indicate that CRF has direct membrane effects on 5-HT DRN neurons as well as indirect effects on GABAergic synaptic transmission that are mediated by distinct receptor subtypes. The inhibition of 5-HT DRN neurons by CRF in vivo may therefore be primarily an indirect effect via stimulation of inhibitory GABA synaptic transmission. These results regarding the cellular mechanisms underlying the complex interaction between CRF, 5-HT, and GABA systems could contribute to the development of novel treatments for stress-related psychiatric disorders.

  3. CORTICOTROPIN-RELEASING FACTOR INCREASES GABA SYNAPTIC ACTIVITY AND INDUCES INWARD CURRENT IN 5-HYDROXYTRYPTAMINE DORSAL RAPHE NEURONS

    PubMed Central

    Kirby, Lynn G.; Freeman-Daniels, Emily; Lemos, Julia C.; Nunan, John D.; Lamy, Christophe; Akanwa, Adaure; Beck, Sheryl G.

    2008-01-01

    Stress-related psychiatric disorders such as anxiety and depression involve dysfunction of the serotonin (5-hydroxytryptamine; 5-HT) system. Previous studies have found that the stress neurohormone corticotropin-releasing factor (CRF) inhibits 5-HT neurons in the dorsal raphe nucleus (DRN) in vivo. The goals of the present study were to characterize the CRF receptor subtypes (CRF-R1 and R2) and cellular mechanisms underlying CRF-5-HT interactions. Visualized whole-cell patch clamp recording techniques in brain slices were used to measure spontaneous or evoked GABA synaptic activity in DRN neurons of rats and CRF effects on these measures. CRF-R1 and -R2-selective agonists were bath applied alone or in combination with receptor-selective antagonists. CRF increased presynaptic GABA release selectively onto 5-HT neurons, an effect mediated by the CRF-R1 receptor. CRF increased postsynaptic GABA receptor sensitivity selectively in 5-HT neurons, an effect to which both receptor subtypes contributed. CRF also had direct effects on DRN neurons, eliciting an inward current in 5-HT neurons mediated by the CRF-R2 receptor and in non 5-HT neurons mediated by the CRF-R1 receptor. These results indicate that CRF has direct membrane effects on 5-HT DRN neurons as well as indirect effects on GABAergic synaptic transmission that are mediated by distinct receptor subtypes. The inhibition of 5-HT DRN neurons by CRF in vivo may therefore be largely an indirect effect via stimulation of inhibitory GABA synaptic transmission. These results regarding the cellular mechanisms underlying the complex interaction between CRF, 5-HT and GABA systems could contribute to the development of novel treatments for stress-related psychiatric disorders. PMID:19036986

  4. 5-Hydroxytryptamine 1A receptors in the dorsomedial hypothalamus connected to dorsal raphe nucleus inputs modulate defensive behaviours and mediate innate fear-induced antinociception.

    PubMed

    Biagioni, Audrey Franceschi; de Oliveira, Rithiele Cristina; de Oliveira, Ricardo; da Silva, Juliana Almeida; dos Anjos-Garcia, Tayllon; Roncon, Camila Marroni; Corrado, Alexandre Pinto; Zangrossi, Hélio; Coimbra, Norberto Cysne

    2016-03-01

    The dorsal raphe nucleus (DRN) is an important brainstem source of 5-hydroxytryptamine (5-HT), and 5-HT plays a key role in the regulation of panic attacks. The aim of the present study was to determine whether 5-HT1A receptor-containing neurons in the medial hypothalamus (MH) receive neural projections from DRN and to then determine the role of this neural substrate in defensive responses. The neurotracer biotinylated dextran amine (BDA) was iontophoretically microinjected into the DRN, and immunohistochemical approaches were then used to identify 5HT1A receptor-labelled neurons in the MH. Moreover, the effects of pre-treatment of the dorsomedial hypothalamus (DMH) with 8-OH-DPAT and WAY-100635, a 5-HT1A receptor agonist and antagonist, respectively, followed by local microinjections of bicuculline, a GABAA receptor antagonist, were investigated. We found that there are many projections from the DRN to the perifornical lateral hypothalamus (PeFLH) but also to DMH and ventromedial (VMH) nuclei, reaching 5HT1A receptor-labelled perikarya. DMH GABAA receptor blockade elicited defensive responses that were followed by antinociception. DMH treatment with 8-OH-DPAT decreased escape responses, which strongly suggests that the 5-HT1A receptor modulates the defensive responses. However, DMH treatment with WAY-100635 failed to alter bicuculline-induced defensive responses, suggesting that 5-HT exerts a phasic influence on 5-HT1A DMH neurons. The activation of the inhibitory 5-HT1A receptor had no effect on antinociception. However, blockade of the 5-HT1A receptor decreased fear-induced antinociception. The present data suggest that the ascending pathways from the DRN to the DMH modulate panic-like defensive behaviours and mediate antinociceptive phenomenon by recruiting 5-HT1A receptor in the MH.

  5. Influence of AMPA/kainate receptors on extracellular 5-hydroxytryptamine in rat midbrain raphe and forebrain

    PubMed Central

    Tao, Rui; Ma, Zhiyuan; Auerbach, Sidney B

    1997-01-01

    The regulation of 5-hydroxytryptamine (5-HT) release by excitatory amino acid (EAA) receptors was examined by use of microdialysis in the CNS of freely behaving rats. Extracellular 5-HT was measured in the dorsal raphe nucleus (DRN), median raphe nucleus (MRN), nucleus accumbens, hypothalamus, frontal cortex, dorsal and ventral hippocampus. Local infusion of kainate produced increases in extracellular 5-HT in the DRN and MRN. Kainate infusion into forebrain sites had a less potent effect. In further studies of the DRN and nucleus accumbens, kainate-induced increases in extracellular 5-HT were blocked by the EAA receptor antagonists, kynurenate and 6,7-dinitroquinoxaline-2,3-dione (DNQX). The effect of infusing kainate into the DRN or nucleus accumbens was attenuated or abolished by tetrodotoxin (TTX), suggesting that the increase in extracellular 5-HT is dependent on 5-HT neuronal activity. In contrast, ibotenate-induced lesion of intrinsic neurones did not attenuate the effect of infusing kainate into the nucleus accumbens. Thus, the effect of kainate in the nucleus accumbens does not depend on intrinsic neurones. Infusion of α-amino-3-hydroxy-5-methyl-4-isoxazolaproprionate (AMPA) into the DRN and nucleus accumbens induced nonsignificant changes in extracellular 5-HT. Cyclothiazide and diazoxide, which attenuate receptor desensitization, greatly enhanced the effect of AMPA on 5-HT in the DRN, but not in the nucleus accumbens. In conclusion, AMPA/kainate receptors regulate 5-HT in the raphe and in forebrain sites. PMID:9283707

  6. Effects of morphine, physostigmine and raphe nuclei stimulation on 5-hydroxytryptamine release from the cerebral cortex of the cat.

    PubMed Central

    Aiello-Malmberg, P; Bartolini, A; Bartolini, R; Galli, A

    1979-01-01

    1. The release of 5-hydroxytryptamine (5-HT) from the cerebral cortex and caudate nucleus of brainstem-transected cats and from the cerebral cortex of rats anaesthetized with urethane was determined by radioenzymatic and biological assay. 2. The stimulation of nucleus linearis intermedius of raphe doubles the basal 5-HT release in the caudate nucleus and increases it 3 fold in the cerebral cortex. The effects of the electrical stimulation of the raphe are potentiated by chlorimipramine. 3. Brain 5-HT release is greatly increased by morphine hydrochloride (6 mg/kg i.v.) and by physostigmine (100 microgram/kg i.v.), but not by DL-DOPA (50 mg/kg i.v.). 4. It is suggested that the 5-HT releasing action of physostigmine can contribute to some of its pharmacological effects such as the analgesic effect so far attributed exclusively to its indirect cholinomimetic activity. 5. The 5-HT releasing action of physostigmine seems unrelated to its anticholinesterase activity. PMID:435680

  7. Effects of 5-hydroxytryptamine on the dorsal muscle of the leech (hirudo medicinalis)

    PubMed Central

    Schain, R. J.

    1961-01-01

    5-Hydroxytryptamine has an inhibiting effect on the leech muscle. It reduces the contractions produced by acetylcholine or nicotine and accelerates the relaxation of the muscle when these substances are washed out. This acceleration of relaxation allows a more rapid assay of acetylcholine in this preparation. PMID:13747232

  8. Serotonin neuronal release from dorsal hippocampus following electrical stimulation of the dorsal and median raphé nuclei in conscious rats.

    PubMed

    Mokler, D J; Lariviere, D; Johnson, D W; Theriault, N L; Bronzino, J D; Dixon, M; Morgane, P J

    1998-01-01

    We have studied 5-hydroxytryptamine (5-HT) release in the hippocampal formation following electrical stimulation of the dorsal and median raphé nuclei in the behaving rat. The primary finding in this study is a decrease in neuronal release of serotonin in the dorsal hippocampal formation following electrical stimulation of either the dorsal or median raphé nucleus in conscious rats. At no time did electrical stimulation of either raphé nucleus result in behavioral, including vigilance state, changes. The amount of 5-HT released was found to be frequency dependent with higher frequencies (20 Hz) producing larger decreases in release of 5-HT. However, the pattern of release differs between the two raphé nuclei. Extracellular levels of 5-HT decrease during stimulation of the dorsal raphé, whereas levels decrease only following cessation of stimulation of the median raphé nucleus. This may relate to the patterns of innervation of the dorsal hippocampal formation by these two midbrain raphé nuclei and also may reflect an inhibition of median raphé cell firing during stimulation of the dorsal raphé. Electrical stimulation of the dorsal raphé in anesthetized animals resulted in an enhanced release of 5-HT. The suppression of 5-HT release in the dorsal hippocampal formation in behaving animals was long-lasting (over 2 h), suggesting that the control mechanisms that regulate 5-HT release operate over a long time-course. This difference in release between non-anesthetized and anesthetized animals may relate to anesthesia blocking long- and/or short-loop serotonin recurrent axonal collaterals negatively feeding back onto 5-HT1A and 5-HT1D somatodendritic autoreceptors on raphé neurons. Further, the anesthetized animal has diminished monoaminergic "gating" influences on the hippocampal formation, whereas the behaving animal is more complex with behavioral (vigilance) states associated with different patterns of gating of information flow through the hippocampal

  9. 5-Hydroxytryptamine2A/2C receptors of nucleus raphe magnus and gigantocellularis/paragigantocellularis pars α reticular nuclei modulate the unconditioned fear-induced antinociception evoked by electrical stimulation of deep layers of the superior colliculus and dorsal periaqueductal grey matter.

    PubMed

    de Oliveira, Ricardo; de Oliveira, Rithiele Cristina; Falconi-Sobrinho, Luiz Luciano; da Silva Soares, Raimundo; Coimbra, Norberto Cysne

    2017-01-01

    The electrical stimulation of the dorsolateral columns of the periaquedutal grey matter (dlPAG) or deep layers of the superior colliculus (dlSC) evokes defensive behaviours followed by an antinociceptive response. Monoaminergic brainstem reticular nuclei are suggested to comprise the endogenous pain modulatory system. The aim of the present work was to investigate the role played by 5-HT2 subfamily of serotonergic receptors of the nucleus raphe magnus (NRM) and the gigantocellularis/paragigantocellularis pars α reticular nuclei (Gi/PGiα) in the elaboration of instinctive fear-induced antinociception elicited by electrical stimulation of dlPAG or of dlSC. The nociceptive thresholds were measured by the tail-flick test in Wistar rats. The 5-HT2A/2C-serotonergic receptors antagonist ritanserin was microinjected at different concentrations (0.05, 0.5 and 5.0μg/0.2μL) either in Gi/PGiα or in NRM. The blockade of 5-HT2 receptors in both Gi/PGiα and NRM decreased the innate fear-induced antinociception elicited by electrical stimulation of the dlSC or the dlPAG. These findings indicate that serotonin is involved in the hypo-algesia induced by unconditioned fear-induced behavioural responses and the 5-HT2A/2C-serotonergic receptor subfamily in neurons situated in the Gi/PGiα complex and NRM are critically recruited in pain modulation during the panic-like emotional behaviour. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. The dorsal raphe modulates sensory responsiveness during arousal in zebrafish

    PubMed Central

    Yokogawa, Tohei; Hannan, Markus C.; Burgess, Harold A.

    2012-01-01

    During waking behavior animals adapt their state of arousal in response to environmental pressures. Sensory processing is regulated in aroused states and several lines of evidence imply that this is mediated at least partly by the serotonergic system. However there is little information directly showing that serotonergic function is required for state-dependent modulation of sensory processing. Here we find that zebrafish larvae can maintain a short-term state of arousal during which neurons in the dorsal raphe modulate sensory responsiveness to behaviorally relevant visual cues. Following a brief exposure to water flow, larvae show elevated activity and heightened sensitivity to perceived motion. Calcium imaging of neuronal activity after flow revealed increased activity in serotonergic neurons of the dorsal raphe. Genetic ablation of these neurons abolished the increase in visual sensitivity during arousal without affecting baseline visual function or locomotor activity. We traced projections from the dorsal raphe to a major visual area, the optic tectum. Laser ablation of the tectum demonstrated that this structure, like the dorsal raphe, is required for improved visual sensitivity during arousal. These findings reveal that serotonergic neurons of the dorsal raphe have a state-dependent role in matching sensory responsiveness to behavioral context. PMID:23100441

  11. Alcohol and nicotine administration inhibits serotonin synthesis and tryptophan hydroxylase expression in dorsal and median raphe of young rats.

    PubMed

    Jang, Mi-Hyeon; Shin, Min-Chul; Lee, Taeck-Hyun; Kim, Young-Pyo; Jung, Sae-Bin; Shin, Dong-Hoon; Kim, Hong; Kim, Sung-Soo; Kim, Ee-Hwa; Kim, Chang-Ju

    2002-08-30

    Serotonin (5-hydroxytryptamine, 5-HT) has been implicated in the pathophysiology of various neuropsychiatric disorders. In the present study, the effects of alcohol and nicotine on the synthesis of 5-HT and the expression of tryptophan hydroxylase (TPH), the rate-limiting enzyme of 5-HT synthesis, in the dorsal and median raphe of young rats were investigated via immunohistochemistry. The numbers of the 5-HT-positive and TPH-positive cells were reduced by alcohol and nicotine treatment in a dose-dependent manner. Based on the results, it can be suggested that the pathogenesis of alcohol- and nicotine-induced neuropsychological disorders involves alcohol- and nicotine-induced suppression of 5-HT synthesis and TPH expression in raphe, and that this may be of particular relevance in the consumption of alcohol and nicotine during adolescence.

  12. Toxin-insensitive Ca current in dorsal raphe neurons.

    PubMed

    Penington, N J; Fox, A P

    1995-08-01

    About 54% of the whole-cell Ca current recorded in dorsal raphe neurons cannot be categorized as N-, L-, or P-type Ca current. This current, ICa-Raphe, was not blocked by a combination of nimodipine, omega-CgTx-GVIA, and omega-AGA-IVA. Differences in toxin sensitivity and voltage dependence suggest that ICa-Raphe is distinct from Q- or R-type Ca currents. In raphe neurons activation of 5-HT1A receptors by 5-HT inhibits approximately 50% of the Ca current and slows activation. 5-HT inhibits both N-type Ca channels and ICa-Raphe channels by approximately 50% and slows the activation of both currents to a similar extent. Other similarities between ICa-Raphe and N-type Ca current were observed; they are both blocked to a similar extent by Ni2+, their activation properties, their current kinetics and channel availability as a function of holding potential are almost identical. Thus, ICa-Raphe represents a current that is not sensitive to known antagonists, but which is similar to N-type Ca current. Although it is possible that ICa-Raphe belongs to a heretofore undiscovered family of Ca channels it is also possible that it represents an omega-CgTx GVIA-insensitive isoform of the N-type Ca channel family.

  13. Burst-firing activity of presumed 5-HT neurones of the rat dorsal raphe nucleus: electrophysiological analysis by antidromic stimulation.

    PubMed

    Hajós, M; Sharp, T

    1996-11-18

    We recently reported raphe neurones which frequently fired spikes in short bursts. However, the action potentials were broad and the neurones fired in a slow and regular pattern, suggesting they were an unusual type of 5-hydroxytryptamine (5-HT) neurone. In the present study, we investigated whether these putative burst-firing 5-HT neurones project to the forebrain and whether all spikes fired in bursts propagate along the axon. In anaesthetised rats, electrical stimulation of the medial forebrain bundle evoked antidromic spikes in both burst-firing neurones and in single-spiking, classical 5-HT neurones recorded in the dorsal raphe nucleus. Although the antidromic spike latency of the single-spiking and burst-firing neurones showed a clear overlap, burst-firing neurones had a significantly shorter latency than single-spiking neurones. For both burst-firing neurones and classical 5-HT neurones, antidromic spikes made collisions with spontaneously occurring spikes. Furthermore, in all burst-firing neurones tested, first, second and third order spikes in a burst could be made to collide with antidromic spike. Interestingly, in a small number of burst-firing neurones, antidromic stimulation evoked spike doublets, similar to those recorded spontaneously. From these data we conclude that burst-firing neurones in the dorsal raphe nucleus project to the forebrain, and each spike generated by the burst propagates along the axon and could thereby release transmitter (5-HT).

  14. 5-HT1A Autoreceptors in the Dorsal Raphe Nucleus Convey Vulnerability to Compulsive Cocaine Seeking.

    PubMed

    You, In-Jee; Wright, Sherie R; Garcia-Garcia, Alvaro L; Tapper, Andrew R; Gardner, Paul D; Koob, George F; David Leonardo, E; Bohn, Laura M; Wee, Sunmee

    2016-04-01

    Cocaine addiction and depression are comorbid disorders. Although it is well recognized that 5-hydroxytryptamine (5-HT; serotonin) plays a central role in depression, our understanding of its role in addiction is notably lacking. The 5-HT system in the brain is carefully controlled by a combined process of regulating 5-HT neuron firing through 5-HT autoreceptors, neurotransmitter release, enzymatic degradation, and reuptake by transporters. This study tests the hypothesis that activation of 5-HT1A autoreceptors, which would lessen 5-HT neuron firing, contributes to cocaine-seeking behaviors. Using 5-HT neuron-specific reduction of 5-HT1A autoreceptor gene expression in mice, we demonstrate that 5-HT1A autoreceptors are necessary for cocaine conditioned place preference. In addition, using designer receptors exclusively activated by designer drugs (DREADDs) technology, we found that stimulation of the serotonergic dorsal raphe nucleus (DRN) afferents to the nucleus accumbens (NAc) abolishes cocaine reward and promotes antidepressive-like behaviors. Finally, using a rat model of compulsive-like cocaine self-administration, we found that inhibition of dorsal raphe 5-HT1A autoreceptors attenuates cocaine self-administration in rats with 6 h extended access, but not 1 h access to the drug. Therefore, our findings suggest an important role for 5-HT1A autoreceptors, and thus DRNNAc 5-HT neuronal activity, in the etiology and vulnerability to cocaine reward and addiction. Moreover, our findings support a strategy for antagonizing 5-HT1A autoreceptors for treating cocaine addiction.

  15. 5-HT1A Autoreceptors in the Dorsal Raphe Nucleus Convey Vulnerability to Compulsive Cocaine Seeking

    PubMed Central

    You, In-Jee; Wright, Sherie R; Garcia-Garcia, Alvaro L; Tapper, Andrew R; Gardner, Paul D; Koob, George F; David Leonardo, E; Bohn, Laura M; Wee, Sunmee

    2016-01-01

    Cocaine addiction and depression are comorbid disorders. Although it is well recognized that 5-hydroxytryptamine (5-HT; serotonin) plays a central role in depression, our understanding of its role in addiction is notably lacking. The 5-HT system in the brain is carefully controlled by a combined process of regulating 5-HT neuron firing through 5-HT autoreceptors, neurotransmitter release, enzymatic degradation, and reuptake by transporters. This study tests the hypothesis that activation of 5-HT1A autoreceptors, which would lessen 5-HT neuron firing, contributes to cocaine-seeking behaviors. Using 5-HT neuron-specific reduction of 5-HT1A autoreceptor gene expression in mice, we demonstrate that 5-HT1A autoreceptors are necessary for cocaine conditioned place preference. In addition, using designer receptors exclusively activated by designer drugs (DREADDs) technology, we found that stimulation of the serotonergic dorsal raphe nucleus (DRN) afferents to the nucleus accumbens (NAc) abolishes cocaine reward and promotes antidepressive-like behaviors. Finally, using a rat model of compulsive-like cocaine self-administration, we found that inhibition of dorsal raphe 5-HT1A autoreceptors attenuates cocaine self-administration in rats with 6 h extended access, but not 1 h access to the drug. Therefore, our findings suggest an important role for 5-HT1A autoreceptors, and thus DRN→NAc 5-HT neuronal activity, in the etiology and vulnerability to cocaine reward and addiction. Moreover, our findings support a strategy for antagonizing 5-HT1A autoreceptors for treating cocaine addiction. PMID:26324408

  16. 5-hydroxytryptamine 2C receptors in the dorsal striatum mediate stress-induced interference with negatively reinforced instrumental escape behavior.

    PubMed

    Strong, P V; Christianson, J P; Loughridge, A B; Amat, J; Maier, S F; Fleshner, M; Greenwood, B N

    2011-12-01

    Uncontrollable stress can interfere with instrumental learning and induce anxiety in humans and rodents. While evidence supports a role for serotonin (5-HT) and serotonin 2C receptors (5-HT(2C)R) in the behavioral consequences of uncontrollable stress, the specific sites of action are unknown. These experiments sought to delineate the role of 5-HT and 5-HT(2C)R in the dorsal striatum (DS) and the lateral/basolateral amygdala (BLA) in the expression of stress-induced instrumental escape deficits and exaggerated fear, as these structures are critical to instrumental learning and fear behaviors. Using in vivo microdialysis, we first demonstrated that prior uncontrollable, but not controllable, stress sensitizes extracellular 5-HT in the dorsal striatum, a result that parallels prior work in the BLA. Additionally, rats were implanted with bi-lateral cannula in either the DS or the BLA and exposed to uncontrollable tail shock stress. One day later, rats were injected with 5-HT(2C)R antagonist (SB242084) and fear and instrumental learning behaviors were assessed in a shuttle box. Separately, groups of non-stressed rats received an intra-DS or an intra-BLA injection of the 5-HT(2C)R agonist (CP809101) and behavior was observed. Intra-DS injections of the 5-HT(2C)R antagonist prior to fear/escape tests completely blocked the stress-induced interference with instrumental escape learning; a partial block was observed when injections were in the BLA. Antagonist administration in either region did not influence stress-induced fear behavior. In the absence of prior stress, intra-DS administration of the 5-HT(2C)R agonist was sufficient to interfere with escape behavior without enhancing fear, while intra-BLA administration of the 5-HT(2C)R agonist increased fear behavior but had no effect on escape learning. Results reveal a novel role of the 5-HT(2C)R in the DS in the expression of instrumental escape deficits produced by uncontrollable stress and demonstrate that the

  17. Reward processing by the dorsal raphe nucleus: 5-HT and beyond

    PubMed Central

    Zhou, Jingfeng; Liu, Zhixiang

    2015-01-01

    The dorsal raphe nucleus (DRN) represents one of the most sensitive reward sites in the brain. However, the exact relationship between DRN neuronal activity and reward signaling has been elusive. In this review, we will summarize anatomical, pharmacological, optogenetics, and electrophysiological studies on the functions and circuit mechanisms of DRN neurons in reward processing. The DRN is commonly associated with serotonin (5-hydroxytryptamine; 5-HT), but this nucleus also contains neurons of the neurotransmitter phenotypes of glutamate, GABA and dopamine. Pharmacological studies indicate that 5-HT might be involved in modulating reward- or punishment-related behaviors. Recent optogenetic stimulations demonstrate that transient activation of DRN neurons produces strong reinforcement signals that are carried out primarily by glutamate. Moreover, activation of DRN 5-HT neurons enhances reward waiting. Electrophysiological recordings reveal that the activity of DRN neurons exhibits diverse behavioral correlates in reward-related tasks. Studies so far thus demonstrate the strong power of DRN neurons in reward signaling and at the same time invite additional efforts to dissect the roles and mechanisms of different DRN neuron types in various processes of reward-related behaviors. PMID:26286655

  18. Dorsal Raphe Dopamine Neurons Represent the Experience of Social Isolation

    PubMed Central

    Matthews, Gillian A.; Nieh, Edward H.; Vander Weele, Caitlin M.; Halbert, Sarah A.; Pradhan, Roma V.; Yosafat, Ariella S.; Glober, Gordon F.; Izadmehr, Ehsan M.; Thomas, Rain E.; Lacy, Gabrielle D.; Wildes, Craig P.; Ungless, Mark A.; Tye, Kay M.

    2016-01-01

    Summary The motivation to seek social contact may arise from either positive or negative emotional states, as social interaction can be rewarding and social isolation can be aversive. While ventral tegmental area (VTA) dopamine (DA) neurons may mediate social reward, a cellular substrate for the negative affective state of loneliness has remained elusive. Here, we identify a functional role for DA neurons in the dorsal raphe nucleus (DRN), in which we observe synaptic changes following acute social isolation. DRN DA neurons show increased activity upon social contact following isolation, revealed by in vivo calcium imaging. Optogenetic activation of DRN DA neurons increases social preference but causes place avoidance. Furthermore, these neurons are necessary for promoting rebound sociability following an acute period of isolation. Finally, the degree to which these neurons modulate behavior is predicted by social rank, together supporting a role for DRN dopamine neurons in mediating a loneliness-like state. PaperClip PMID:26871628

  19. Serotonin neurons in the dorsal raphe nucleus encode reward signals

    PubMed Central

    Li, Yi; Zhong, Weixin; Wang, Daqing; Feng, Qiru; Liu, Zhixiang; Zhou, Jingfeng; Jia, Chunying; Hu, Fei; Zeng, Jiawei; Guo, Qingchun; Fu, Ling; Luo, Minmin

    2016-01-01

    The dorsal raphe nucleus (DRN) is involved in organizing reward-related behaviours; however, it remains unclear how genetically defined neurons in the DRN of a freely behaving animal respond to various natural rewards. Here we addressed this question using fibre photometry and single-unit recording from serotonin (5-HT) neurons and GABA neurons in the DRN of behaving mice. Rewards including sucrose, food, sex and social interaction rapidly activate 5-HT neurons, but aversive stimuli including quinine and footshock do not. Both expected and unexpected rewards activate 5-HT neurons. After mice learn to wait for sucrose delivery, most 5-HT neurons fire tonically during waiting and then phasically on reward acquisition. Finally, GABA neurons are activated by aversive stimuli but inhibited when mice seek rewards. Thus, DRN 5-HT neurons positively encode a wide range of reward signals during anticipatory and consummatory phases of reward responses. Moreover, GABA neurons play a complementary role in reward processing. PMID:26818705

  20. Presynaptic partners of dorsal raphe serotonergic and GABAergic neurons.

    PubMed

    Weissbourd, Brandon; Ren, Jing; DeLoach, Katherine E; Guenthner, Casey J; Miyamichi, Kazunari; Luo, Liqun

    2014-08-06

    The serotonin system powerfully modulates physiology and behavior in health and disease, yet the circuit mechanisms underlying serotonin neuron activity are poorly understood. The major source of forebrain serotonergic innervation is from the dorsal raphe nucleus (DR), which contains both serotonin and GABA neurons. Using viral tracing combined with electrophysiology, we found that GABA and serotonin neurons in the DR receive excitatory, inhibitory, and peptidergic inputs from the same specific brain regions. Embedded in this overall similarity are important differences. Serotonin neurons are more likely to receive synaptic inputs from anterior neocortex while GABA neurons receive disproportionally higher input from the central amygdala. Local input mapping revealed extensive serotonin-serotonin as well as GABA-serotonin connectivity with a distinct spatial organization. Covariance analysis suggests heterogeneity of both serotonin and GABA neurons with respect to the inputs they receive. These analyses provide a foundation for further functional dissection of the serotonin system.

  1. Presynaptic Partners of Dorsal Raphe Serotonergic and GABAergic Neurons

    PubMed Central

    Weissbourd, Brandon; Ren, Jing; DeLoach, Katherine E.; Guenthner, Casey J.; Miyamichi, Kazunari; Luo, Liqun

    2016-01-01

    SUMMARY The serotonin system powerfully modulates physiology and behavior in health and disease, yet the circuit mechanisms underlying serotonin neuron activity are poorly understood. The major source of forebrain serotonergic innervation is from the dorsal raphe nucleus (DR), which contains both serotonin and GABA neurons. Using viral tracing combined with electrophysiology, we found that GABA and serotonin neurons in the DR receive excitatory, inhibitory, and peptidergic inputs from the same specific brain regions. Embedded in this overall similarity are important differences. Serotonin neurons are more likely to receive synaptic inputs from anterior neocortex while GABA neurons receive disproportionally higher input from the central amygdala. Local input mapping revealed extensive serotonin-serotonin as well as GABA-serotonin connectivity with a distinct spatial organization. Covariance analysis suggests heterogeneity of both serotonin and GABA neurons with respect to the inputs they receive. These analyses provide a foundation for further functional dissection of the serotonin system. PMID:25102560

  2. Two Major Network Domains within the Dorsal Raphe Nucleus

    PubMed Central

    Commons, Kathryn G.

    2015-01-01

    Serotonin neurons in the dorsal and median raphe nuclei (DR and MR) are clustered into heterogeneous groups that give rise to topographically organized forebrain projections. However, a compelling definition of the key subgroups of serotonin neurons within these areas has remained elusive. In order to be functionally distinct, neurons must participate in distinct networks. Therefore we analyzed subregions of the DR and MR by their afferent input. Clustering methods and principal component analysis were applied to anterograde tract-tracing experiments in mouse available from the Allen Mouse Brain Connectivity Atlas. The results revealed a major break in the networks of the DR such that the caudal third of the DR was more similar in afferent innervation to the MR than it was to the rostral two thirds of the DR. The rostral part of the DR is associated with networks controlling motor and motivated behavior, while the caudal DR is more closely aligned with regions that regulate rhythmic hippocampal activity. Thus a major source of heterogeneity within the DR is inclusion of the caudal component, which may be more accurately viewed as a dorsal extension of the MR. PMID:25652113

  3. Two major network domains in the dorsal raphe nucleus.

    PubMed

    Commons, Kathryn G

    2015-07-01

    Serotonin neurons in the dorsal and median raphe nuclei (DR and MR) are clustered into heterogeneous groups that give rise to topographically organized forebrain projections. However, a compelling definition of the key subgroups of serotonin neurons within these areas has remained elusive. In order to be functionally distinct, neurons must participate in distinct networks. Therefore, we analyzed subregions of the DR and MR by their afferent input. Clustering methods and principal component analysis were applied in mouse to anterograde tract-tracing experiments available from the Allen Mouse Brain Connectivity Atlas. The results revealed a major break in the networks of the DR such that the caudal third of the DR was more similar in afferent innervation to the MR than it was to the rostral two-thirds of the DR. The rostral part of the DR is associated with networks controlling motor and motivated behavior, while the caudal DR is more closely aligned with regions that regulate rhythmic hippocampal activity. Thus, a major source of heterogeneity within the DR is inclusion of the caudal component, which may be more accurately viewed as a dorsal extension of the MR.

  4. Neuropharmacology of 5-hydroxytryptamine

    PubMed Central

    Richard Green, A

    2006-01-01

    This review outlines the history of our knowledge of the neuropharmacology of 5-hydroxytryptamine (5-HT; serotonin), focusing primarily on the work of U.K. scientists. The existence of a vasoconstrictive substance in the blood has been known for over 135 years. The substance was named serotonin and finally identified as 5-HT in 1949. The presence of 5-HT in the brain was reported by Gaddum in 1954 and it was Gaddum who also demonstrated that the action of 5-HT (in the gut) was antagonised by the potent hallucinogen lysergic acid diethylamide. This provoked the notion that 5-HT played a pivotal role in the control of mood and subsequent investigations have generally confirmed this hypothesis. Over the last 50 years a good understanding has been gained of the mechanisms involved in control of the storage, synthesis and degradation of 5-HT in the brain. Knowledge has also been gained on control of the functional activity of this monoamine, often by the use of behavioural models. A considerable literature also now exists on the mechanisms by which many of the drugs used to treat psychiatric illness alter the functional activity of 5-HT, particularly the drugs used to treat depression. Over the last 20 years the number of identified 5-HT receptor subtypes has increased from 2 to 14, or possibly more. A major challenge now is to utilise this knowledge to develop receptor-specific drugs and use the information gained to better treat central nervous system disorders. PMID:16402098

  5. Ovarian Steroids Increase Spinogenetic Proteins in the Macaque Dorsal Raphe

    PubMed Central

    Rivera, Heidi M.; Bethea, Cynthia L.

    2012-01-01

    Dendritic spines are the basic structural units of neuronal plasticity. Intracellular signaling cascades that promote spinogenesis have centered on RhoGTPases. We found that ovarian steroids increase gene expression of RhoGTPases (RhoA, Cdc42 and Rac) in laser-captured serotonin neurons. We sought to confirm that the increases observed in gene expression translate to the protein level. In addition, a preliminary study was conducted to determine whether an increase in spines occurs via detection of the spine marker protein, PSD-95. Adult ovariectomized (Ovx) monkeys were treated with estradiol (E), progesterone (P) or E+P for 1 month. Sections through the dorsal raphe nucleus were immunostained for RhoA and Cdc42 (n = 3-4/group). The number and positive pixel area of RhoA-positive cells, and the positive pixel area of Cdc42-positive fibers were determined. Upon combining E and E+P treated groups, there was a significant increase in the average and total cell number and positive pixel area of RhoA-positive cells. E, P and E+P treatments individually or combined, also increased the average and total positive pixel area of Cdc42-positive fibers. With remaining sections from 2 animals in each group, we conducted a preliminary examination of the regulation of PSD-95 protein expression. PSD-95, a postsynaptic scaffold protein, was examined with immunogold silver staining (n = 2/group) and the total number of PSD-95-positive puncta was determined with stereology across 4 levels of the dorsal raphe. E, P and E+P treatment significantly increased the total number of PSD-95-positive puncta. Together, these findings indicate that ovarian steroids act to increase gene and protein expression of two pivotal RhoGTPases involved in spinogenesis and preliminarily indicate that an increased number of spines and/or synapses result from this action. Increased spinogenesis on serotonin dendrites would facilitate excitatory glutamatergic input and in turn, increase serotonin neuronal

  6. Dorsal raphe nucleus projecting retinal ganglion cells: Why Y cells?

    PubMed Central

    Pickard, Gary E.; So, Kwok-Fai; Pu, Mingliang

    2015-01-01

    Retinal ganglion Y (alpha) cells are found in retinas ranging from frogs to mice to primates. The highly conserved nature of the large, fast conducting retinal Y cell is a testament to its fundamental task, although precisely what this task is remained ill-defined. The recent discovery that Y-alpha retinal ganglion cells send axon collaterals to the serotonergic dorsal raphe nucleus (DRN) in addition to the lateral geniculate nucleus (LGN), medial interlaminar nucleus (MIN), pretectum and the superior colliculus (SC) has offered new insights into the important survival tasks performed by these cells with highly branched axons. We propose that in addition to its role in visual perception, the Y-alpha retinal ganglion cell provides concurrent signals via axon collaterals to the DRN, the major source of serotonergic afferents to the forebrain, to dramatically inhibit 5-HT activity during orientation or alerting/escape responses, which dis-facilitates ongoing tonic motor activity while dis-inhibiting sensory information processing throughout the visual system. The new data provide a fresh view of these evolutionarily old retinal ganglion cells. PMID:26363667

  7. Effects on serotonin of (-)nicotine and dimethylphenylpiperazinium in the dorsal raphe and nucleus accumbens of freely behaving rats.

    PubMed

    Ma, Z; Strecker, R E; McKenna, J T; Thakkar, M M; McCarley, R W; Tao, R

    2005-01-01

    The aim of this study was to investigate the neurochemical mechanism underlying the effect of nicotine and dimethylphenylpiperazinium (DMPP) on 5-hydroxytryptamine (5-HT) release in the dorsal raphe nucleus and nucleus accumbens of freely behaving rats. For comparison, lobeline, cytisine and RJR-2403 were also investigated. It was found that all drugs, when infused locally, evoked an increase of 5-HT in the dorsal raphe nucleus. However, the magnitudes of the 5-HT increase were comparatively different between the drugs in the ranking of their potency: DMPP>RJR 2403>nicotine>lobeline>cytisine. Both methyllycaconitine, a nicotinic acetylcholine receptor (nAChR) antagonist and methyllycaconitine, a selective alpha7-containing nAChR antagonist blocked the effects of nicotine and DMPP, suggesting that alpha7 subunit mediated the increases in 5-HT. However, DMPP was reported to increase 5-HT using non-nAChR mechanism [Lendvai B, Sershen H, Lajtha A, Santha E, Baranyi M, Vizi ES (1996) Differential mechanisms involved in the effect of nicotinic agonists DMPP and lobeline to release [3H]5-HT from rat hippocampal slices. Neuropharmacology 35:1769-1777]. To test if 5-HT carriers were involved, a selective 5-HT reuptake inhibitor citalopram (1 microM) was infused into the dorsal raphe nucleus before administration of nicotine or DMPP. As a result, citalopram significantly blocked the effect of DMPP, whereas it had no influence on nicotine. Finally, the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) was used to test whether the increases in 5-HT were depolarization-dependent. Administration of 8-OH-DPAT (0.1 mg/kg, s.c.) produced significant decreases in 5-HT in the animals treated with nicotine. In contrast, the effect of DMPP was not altered by 8-OH-DPAT, suggesting that the increases in 5-HT were independent of cell membrane depolarization. In conclusion, there are different mechanisms involved in nicotine- and DMPP-evoked increases in 5-HT. This

  8. The effects of median raphé electrical stimulation on serotonin release in the dorsal hippocampal formation of prenatally protein malnourished rats.

    PubMed

    Mokler, D J; Bronzino, J D; Galler, J R; Morgane, P J

    1999-08-14

    Our previous work had shown an enhanced inhibition in the hippocampal formation of prenatally protein malnourished rats. We have also found a diminishment in 5-hydroxytryptamine (5-HT) fibers in the hippocampal formation of malnourished rats as well as increased levels of 5-HT in the brain. The purpose of the present study was to determine 5-HT release in the dorsal hippocampal formation following electrical stimulation of the median raphé nucleus (MRN) in unanesthetized prenatally malnourished rats. Stimulation of this nucleus at 20 Hz in malnourished rats resulted in a significantly diminished release of 5-HT compared to well-nourished rats. The latter group showed a lesser, though still significant, decrease in 5-HT release following raphé stimulation. Basal release of 5-HT prior to stimulation was significantly higher in malnourished rats as compared to well-nourished controls. This may be the result of a decreased density of 5-HT neurons leading to a diminished control of release. Stimulation of the MRN in behaving malnourished animals may markedly affect the recurrent negative feedback collaterals onto somatodendritic 5-HT(1A) and 5-HT(1D) autoreceptors thus enhancing the inhibitory effects of stimulation of the median raphé on 5-HT release. Studies are underway to examine the sensitivity of both the somatodendritic and terminal 5-HT autoreceptors in malnourished animals, in order to understand possible mechanisms for our findings.

  9. Patterned expression of ion channel genes in mouse dorsal raphe nucleus determined with the Allen Mouse Brain Atlas

    PubMed Central

    Templin, J. Scott; Bang, Sun Jung; Soiza-Reilly, Mariano; Berde, Charles B.; Commons, Kathryn G.

    2012-01-01

    The dorsal raphe nucleus (DR) is the major source of serotonin (5-hydroxytryptamine, 5-HT) in the forebrain and dysfunction of this midbrain structure is implicated in affective disorders. The DR is composed of several types of 5-HT and non-5-HT neurons and their excitable-membrane properties are heterogeneous and overlapping. In order to understand how these properties may be generated, we examined the mRNA expression patterns of voltage- and ligand-gated ion channels in the DR using the Allen Mouse Brain Atlas. Since DR cytoarchitecture is organized with respect to the midline, we sought to identify genes that were expressed in a pattern with respect to the midline, either enriched or depleted, rather than those that were homogenously expressed throughout the DR. Less than 10% of the screened genes for voltage-gated ion channels showed patterned expression within the DR. Identified genes included voltage-gated sodium channel beta subunits, potassium channels, P/Q-, N-type calcium channels, as well as the alpha2/delta-1 calcium channel. Several voltage-gated chloride channels were also identified, although these may function within intracellular compartments. Of the ligand-gated ion channels examined, 20% showed patterned expression. These consisted primarily of glutamate and GABA-A receptor subunits. The identified genes likely contribute to unique excitable properties of different groups of neurons in the DR and may include novel pharmacologic targets for affective disorders. PMID:22534482

  10. Dorsal Raphe Neuroinflammation Promotes Dramatic Behavioral Stress Dysregulation

    PubMed Central

    Howerton, Alexis R.; Roland, Alison V.

    2014-01-01

    Impulsivity, risk-taking behavior, and elevated stress responsivity are prominent symptoms of mania, a behavioral state common to schizophrenia and bipolar disorder. Though inflammatory processes activated within the brain are involved in the pathophysiology of both disorders, the specific mechanisms by which neuroinflammation drives manic behavior are not well understood. Serotonin cell bodies originating within the dorsal raphe (DR) play a major role in the regulation of behavioral features characteristic of mania. Therefore, we hypothesized that the link between neuroinflammation and manic behavior may be mediated by actions on serotonergic neurocircuitry. To examine this, we induced local neuroinflammation in the DR by viral delivery of Cre recombinase into interleukin (IL)-1βXAT transgenic male and female mice, resulting in overexpressing of the proinflammatory cytokine, IL-1β. For assertion of brain-region specificity of these outcomes, the prefrontal cortex (PFC), as a downstream target of DR serotonergic projections, was also infused. Inflammation within the DR, but not the PFC, resulted in a profound display of manic-like behavior, characterized by increased stress-induced locomotion and responsivity, and reduced risk-aversion/fearfulness. Microarray analysis of the DR revealed a dramatic increase in immune-related genes, and dysregulation of genes important in GABAergic, glutamatergic, and serotonergic neurotransmission. Behavioral and physiological changes were driven by a loss of serotonergic neurons and reduced output as measured by high-performance liquid chromatography, demonstrating inflammation-induced serotonergic hypofunction. Behavioral changes were rescued by acute selective serotonin reuptake inhibitor treatment, supporting the hypothesis that serotonin dysregulation stemming from neuroinflammation in the DR underlies manic-like behaviors. PMID:24849347

  11. Reward Processing by the Dorsal Raphe Nucleus: 5-HT and Beyond

    ERIC Educational Resources Information Center

    Luo, Minmin; Zhou, Jingfeng; Liu, Zhixiang

    2015-01-01

    The dorsal raphe nucleus (DRN) represents one of the most sensitive reward sites in the brain. However, the exact relationship between DRN neuronal activity and reward signaling has been elusive. In this review, we will summarize anatomical, pharmacological, optogenetics, and electrophysiological studies on the functions and circuit mechanisms of…

  12. Reward Processing by the Dorsal Raphe Nucleus: 5-HT and Beyond

    ERIC Educational Resources Information Center

    Luo, Minmin; Zhou, Jingfeng; Liu, Zhixiang

    2015-01-01

    The dorsal raphe nucleus (DRN) represents one of the most sensitive reward sites in the brain. However, the exact relationship between DRN neuronal activity and reward signaling has been elusive. In this review, we will summarize anatomical, pharmacological, optogenetics, and electrophysiological studies on the functions and circuit mechanisms of…

  13. Effects of electrical stimulation of the dorsal raphe nucleus on local cerebral blood flow in the rat

    SciTech Connect

    Bonvento, G.; Lacombe, P.; Seylaz, J. )

    1989-06-01

    We have studied the effects of electrical stimulation of the dorsal raphe nucleus on local cerebral blood flow (LCBF), as assessed by the quantitative ({sup 14}C)-iodoantipyrine autoradiographic technique. Stimulation of the dorsal raphe nucleus in the alpha-chloralose anesthetized rat caused a significant decrease in LCBF, ranging from -13 to -26% in 24 brain structures out of 33 investigated. The most pronounced decreases (-23 to -26%) were observed in the accumbens, amygdaloid, interpeduncular nuclei and in the median raphe nucleus, limbic system relays. The decreases also concerned cortical regions and the extrapyramidal system. These results indicate that activation of ascending serotonergic system produces a vasoconstriction and that the dorsal raphe nucleus has a widespread modulatory influence on the cerebral circulation.

  14. 5-HT1A/1B, 5-HT6, and 5-HT7 serotonergic receptors recruitment in tonic-clonic seizure-induced antinociception: role of dorsal raphe nucleus.

    PubMed

    Freitas, Renato Leonardo; Ferreira, Célio Marcos dos Reis; Urbina, Maria Angélica Castiblanco; Mariño, Andrés Uribe; Carvalho, Andressa Daiane; Butera, Giuseppe; de Oliveira, Ana Maria; Coimbra, Norberto Cysne

    2009-05-01

    Pharmacological studies have been focused on the involvement of different neural pathways in the organization of antinociception that follows tonic-clonic seizures, including 5-hydroxytryptamine (5-HT)-, norepinephrine-, acetylcholine- and endogenous opioid peptide-mediated mechanisms, giving rise to more in-depth comprehension of this interesting post-ictal antinociceptive phenomenon. The present work investigated the involvement of 5-HT(1A/1B), 5-HT(6), and 5-HT(7) serotonergic receptors through peripheral pretreatment with methiothepin at doses of 0.5, 1.0, 2.0 and 3.0 mg/kg in the organization of the post-ictal antinociception elicited by pharmacologically (with pentylenetetrazole at 64 mg/kg)-induced tonic-clonic seizures. Methiothepin at 1.0 mg/kg blocked the post-ictal antinociception recorded after the end of seizures, whereas doses of 2.0 and 3.0 mg/kg potentiated the post-ictal antinociception. The nociceptive thresholds were kept higher than those of the control group. However, when the same 5-hydroxytryptamine receptors antagonist was microinjected (at 1.0, 3.0 and 5.0 microg/0.2 microL) in the dorsal raphe nucleus, a mesencephalic structure rich in serotonergic neurons and 5-HT receptors, the post-ictal hypo-analgesia was consistently antagonized. The present findings suggest a dual effect of methiothepin, characterized by a disinhibitory effect on the post-ictal antinociception when peripherally administered (possibly due to an antagonism of pre-synaptic 5-HT(1A) serotonergic autoreceptors in the pain endogenous inhibitory system) and an inhibitory effect (possibly due to a DRN post-synaptic 5-HT(1B), 5-HT(6), and 5-HT(7) serotonergic receptors blockade) when centrally administered. The present data also suggest that serotonin-mediated mechanisms of the dorsal raphe nucleus exert a key-role in the modulation of the post-ictal antinociception.

  15. 5-HT in the dorsal raphe nucleus is involved in the effects of 100-Hz electro-acupuncture on the pain-depression dyad in rats

    PubMed Central

    Wu, Yuan-Yuan; Jiang, Yong-Liang; He, Xiao-Fen; Zhao, Xiao-Yun; Shao, Xiao-Mei; Sun, Jing; Shen, Zui; Shou, Shen-Yun; Wei, Jun-Jun; Ye, Jia-Yu; Yan, Si-Si; Fang, Jian-Qiao

    2017-01-01

    The pain-depression dyad is becoming widespread in the clinic and is attracting increasing attention. A previous study by our group found that 100-Hz electro-acupuncture (EA), but not 2-, 50- and 2/100-Hz EA, was effective against the reserpine-induced pain-depression dyad. This finding is in contrast to the fact that low-frequency EA is commonly used to treat supraspinal-originating diseases. The present study aimed to investigate the mechanism underlying the effects of 100-Hz EA on the pain-depression dyad. Repeated reserpine injection was found to induce allodynia and depressive behaviors in rats. It decreased 5-hydroxytryptamine (5-HT) levels and immunoreactive expressions in the dorsal raphe nucleus (DRN). 100-Hz EA alleviated the pain-depression dyad and upregulated 5-HT in the DRN of reserpine-injected rats. Intracerebroventricular injection of para-chlorophenylalanine, an inhibitor of 5-HT resynthesis, suppressed the upregulation of 5-HT in the DRN by 100-Hz EA and partially counteracted the analgesic and anti-depressive effects of 100-Hz EA. The present study was the first to demonstrate that 5-HT in the DRN is involved in mediating the analgesic and anti-depressive effects of 100-Hz EA on the pain-depression dyad. This finding provided a scientific basis for high-frequency EA as a potential treatment for the pain-depression dyad. PMID:28672900

  16. A morphometric, immunohistochemical, and in situ hybridization study of the dorsal raphe nucleus in major depression, bipolar disorder, schizophrenia, and suicide

    PubMed Central

    Matthews, Paul R.; Harrison, Paul J.

    2012-01-01

    Background Several lines of evidence implicate 5-hydroxytryptamine (5-HT, serotonin) in the pathophysiology of mood disorders and suicide. However, it is unclear whether these conditions include morphological involvement of the dorsal raphe nucleus (DRN), the origin of most forebrain 5-HT innervation. Method We used morphometric, immunohistochemical, and molecular methods to compare the DRN in post-mortem tissue of 50 subjects (13 controls, 14 major depressive disorder [MDD], 13 bipolar disorder, 10 schizophrenia; 17 of the cases died by suicide). NeuN and PH8 antibodies were used to assess all neurons and serotonergic neurons respectively; 5-HT1A autoreceptor expression was investigated by regional and cellular in situ hybridization. Measurements were made at three rostrocaudal levels of the DRN. Results In MDD, the area of the DRN was decreased. In bipolar disorder, serotonergic neuronal size was decreased. Suicide was associated with an increased DRN area, and with a higher density but decreased size of serotonergic neurons. Total neuronal density and 5-HT1A receptor mRNA abundance were unaffected by diagnosis or suicide. No changes were seen in schizophrenia. Conclusion The results show that mood disorders and suicide are associated with differential, limited morphological alterations of the DRN. The contrasting influences of MDD and suicide may explain some of the discrepancies between previous studies, since their design precluded detection of the effect. PMID:22129767

  17. In Vivo Effect of a 5-HT7 Receptor Agonist on 5-HT Neurons and GABA Interneurons in the Dorsal Raphe Nuclei of Sham and PD Rats.

    PubMed

    Wang, Shuang; Zhao, Yan; Gao, Jie; Guo, Yufang; Wang, Xiang; Huo, Jian; Wei, Ping; Cao, Jian

    2017-03-01

    The 5-hydroxytryptamine (5-HT; serotonin) neurotransmission is severely affected by the degeneration of nigrostriatal dopaminergic neurons. Here, we report the effects of the systemic administration of the 5-HT7 receptor agonist AS-19. In sham rats, the mean response of the 5-HT neurons in the dorsal raphe nucleus (DRN) to systemic AS-19 was excitatory and the mean response of the γ-aminobutyric acid (GABA) interneurons was inhibitory. In Parkinson disease (PD) rats, the same dose did not affect the 5-HT neurons and only high doses (640 μg/kg intravenous) were able to the increase GABA interneuron activity. These results indicate that DRN 5-HT neurons and GABA interneurons are regulated by the activation of 5-HT7 receptors and that the degeneration of the nigrostriatal pathway leads to decreased responses of these neurons to AS-19, which in turn suggests that the 5-HT7 receptors on 5-HT neurons and GABA interneurons in PD rats are dysfunctional and downregulated.

  18. Shifting topographic activation and 5-HT1A receptor-mediated inhibition of dorsal raphe serotonin neurons produced by nicotine exposure and withdrawal.

    PubMed

    Sperling, Robin; Commons, Kathryn G

    2011-05-01

    Nicotine activates serotonin [5-hydroxytryptamine (5-HT)] neurons innervating the forebrain, and this is thought to reduce anxiety. Nicotine withdrawal has also been associated with an activation of 5-HT neurotransmission, although withdrawal increases anxiety. In each case, 5-HT1A receptors have been implicated in the response. To determine whether there are different subgroups of 5-HT cells activated during nicotine administration and withdrawal, we mapped the appearance of Fos, a marker of neuronal activation, in 5-HT cells of the dorsal raphe nucleus (DR) and median raphe nucleus (MR). To understand the role of 5-HT1A receptor feedback inhibitory pathways in 5-HT cell activity during these conditions, we administered a selective 5-HT1A receptor antagonist and measured novel disinhibited Fos expression within 5-HT cells. Using these approaches, we found evidence that acute nicotine exposure activates 5-HT neurons rostrally and in the lateral wings of the DR, whereas there is 5-HT1A receptor-dependent inhibition of cells located ventrally at both the rostral level and mid-level. Previous chronic nicotine exposure did not modify the pattern of activation produced by acute nicotine exposure, but increased 5-HT1A receptor-dependent inhibition of 5-HT cells in the caudal DR. This pattern was nearly reversed during nicotine withdrawal, when there was evidence for caudal activation and mid-level and rostral 5-HT1A receptor-dependent inhibition. These results suggest that the distinct behavioral states produced by nicotine exposure and withdrawal correlate with reciprocal rostral-caudal patterns of activation and 5-HT1A receptor-mediated inhibition of DR 5-HT neurons. The complementary patterns of activation and inhibition suggest that 5-HT1A receptors may help to shape distinct topographic patterns of activation within the DR.

  19. Activation of dorsal raphe serotonin neurons is necessary for waiting for delayed rewards.

    PubMed

    Miyazaki, Kayoko W; Miyazaki, Katsuhiko; Doya, Kenji

    2012-08-01

    The forebrain serotonergic system is a crucial component in the control of impulsive behaviors. We previously reported that the activity of serotonin neurons in the midbrain dorsal raphe nucleus increased when rats performed a task that required them to wait for delayed rewards. However, the causal relationship between serotonin neural activity and the tolerance for the delayed reward remained unclear. Here, we test whether the inhibition of serotonin neural activity by the local application of the 5-HT(1A) receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin in the dorsal raphe nucleus impairs rats' tolerance for delayed rewards. Rats performed a sequential food-water navigation task that required them to visit food and water sites alternately via a tone site to get rewards at both sites after delays. During the short (2 s) delayed reward condition, the inhibition of serotonin neural activity did not significantly influence the numbers of reward choice errors (nosepoke at an incorrect reward site following a conditioned reinforcer tone), reward wait errors (failure to wait for the delayed rewards), or total trials (sum of reward choice errors, reward wait errors, and acquired rewards). By contrast, during the long (7-11 s) delayed reward condition, the number of wait errors significantly increased while the numbers of total trials and choice errors did not significantly change. These results indicate that the activation of dorsal raphe serotonin neurons is necessary for waiting for long delayed rewards and suggest that elevated serotonin activity facilitates waiting behavior when there is the prospect of forthcoming rewards.

  20. Serotonergic systems, anxiety, and affective disorder: focus on the dorsomedial part of the dorsal raphe nucleus.

    PubMed

    Lowry, Christopher A; Hale, Matthew W; Evans, Andrew K; Heerkens, Jasper; Staub, Daniel R; Gasser, Paul J; Shekhar, Anantha

    2008-12-01

    Depressed suicide patients have elevated expression of neuronal tryptophan hydroxylase 2 (TPH2) mRNA and protein in midbrain serotonergic neurons, as well as increases in brain serotonin turnover. The mechanisms underlying these changes are uncertain, but increased TPH2 expression and serotonin turnover could result from genetic influences, adverse early life experiences, or acute stressful life events, all of which can alter serotonergic neurotransmission and have been implicated in determining vulnerability to major depression. Emerging evidence suggests that there are several different stress-related subsets of serotonergic neurons, each with a unique role in the integrated stress response. Here we review our current understanding of how genetic and environmental factors may influence TPH2 mRNA expression and serotonergic neurotransmission, focusing in particular on the dorsomedial part of the dorsal raphe nucleus. This subdivision of the dorsal raphe nucleus is selectively innervated by key forebrain structures implicated in regulation of anxiety states, it gives rise to projections to a distributed neural system mediating anxiety states, and serotonergic neurons within this subdivision are selectively activated by a number of stress- and anxiety-related stimuli. A better understanding of the anatomical and functional properties of specific stress- or anxiety-related serotonergic systems should aid our understanding of the neural mechanisms underlying the etiology of anxiety and affective disorders.

  1. The effect of the selective 5-HT1A agonists alnespirone (S-20499) and 8-OH-DPAT on extracellular 5-hydroxytryptamine in different regions of rat brain

    PubMed Central

    Casanovas, J M; Lésourd, M; Artigas, F

    1997-01-01

    We have examined the effects of the systemic administration of the selective 5-HT1A agonist alnespirone (S-20499) on in vivo 5-hydroxytryptamine (5-HT) release in the dorsal raphe nucleus, the median raphe nucleus and four forebrain areas innervated differentially by both (dorsal striatum, frontal cortex, ventral hippocampus and dorsal hippocampus). Alnespirone (0.1–3 mg kg−1, s.c.) dose-dependently reduced extracellular 5-HT in the six areas examined. In forebrain, the maximal reductions occurred in striatum and frontal cortex (maximal reduction to 23 and 29% of baseline, respectively). Those in dorsal and ventral hippocampus were more moderate (to ca 65% of baseline). In contrast, the decrease in 5-HT elicited in the median raphe nucleus was more marked than that in the dorsal raphe nucleus (to ca 30 and 60% of baseline, respectively). The selective 5-HT1A antagonist WAY-100635 (0.5 mg kg−1, s.c.) prevented the decrease in 5-HT induced by alnespirone (0.3 mg kg−1, s.c.) in frontal cortex. 8-OH-DPAT (0.025, 0.1 and 0.3 mg kg−1, s.c.) also reduced extracellular 5-HT in a regionally-selective manner (e.g., to 32% of baseline in striatum and to 69% in dorsal hippocampus at 0.1 mg kg−1, s.c.). In midbrain, 8-OH-DPAT reduced the dialysate 5-HT slightly more in the median than in the dorsal raphe nucleus at all doses examined. Doses of both compounds close to their respective ED50 values (0.3 mg kg−1 alnespirone, 0.025 mg kg−1 8-OH-DPAT) reduced 5-HT to a comparable extent in all regions examined. However, the reductions attained at higher doses were more pronounced for 8-OH-DPAT. These data show that the reduction of 5-HT release elicited by alnespirone and 8-OH-DPAT is more important in forebrain areas innervated by 5-hydroxytryptaminergic neurones of the dorsal raphe nucleus. This regional selectivity seems unlikely to be accounted for by differences in the sensitivity of 5-HT1A autoreceptors controlling 5-HT release, given

  2. Effects of cocaine history on postsynaptic GABA receptors on dorsal raphe serotonin neurons in a stress-induced relapse model in rats.

    PubMed

    Li, Chen; Kirby, Lynn G

    2016-01-01

    The serotonin (5-hydroxytryptamine, 5-HT) system plays an important role in stress-related psychiatric disorders and substance abuse. Stressors and stress hormones can inhibit the dorsal raphe nucleus (DRN)-5-HT system, which composes the majority of forebrain-projecting 5-HT. This inhibition is mediated via stimulation of GABA synaptic activity at DRN-5-HT neurons. Using swim stress-induced reinstatement of morphine conditioned place-preference, recent data from our laboratory indicate that morphine history sensitizes DRN-5-HT neurons to GABAergic inhibitory effects of stress. Moreover, GABAA receptor-mediated inhibition of the serotonergic DRN is required for this reinstatement. In our current experiment, we tested the hypothesis that GABAergic sensitization of DRN-5-HT neurons is a neuroadaptation elicited by multiple classes of abused drugs across multiple models of stress-induced relapse by applying a chemical stressor (yohimbine) to induce reinstatement of previously extinguished cocaine self-administration in Sprague-Dawley rats. Whole-cell patch-clamp recordings of GABA synaptic activity in DRN-5-HT neurons were conducted after the reinstatement. Behavioral data indicate that yohimbine triggered reinstatement of cocaine self-administration. Electrophysiology data indicate that 5-HT neurons in the cocaine group exposed to yohimbine had increased amplitude of inhibitory postsynaptic currents compared to yoked-saline controls exposed to yohimbine or unstressed animals in both drug groups. These data, together with previous findings, indicate that interaction between psychostimulant or opioid history and chemical or physical stressors may increase postsynaptic GABA receptor density and/or sensitivity in DRN-5-HT neurons. Such mechanisms may result in serotonergic hypofunction and consequent dysphoric mood states which confer vulnerability to stress-induced drug reinstatement. Copyright © 2015 Elsevier B.V. and ECNP. All rights reserved.

  3. Glucagon-Like Peptide 1 and Its Analogs Act in the Dorsal Raphe and Modulate Central Serotonin to Reduce Appetite and Body Weight.

    PubMed

    Anderberg, Rozita H; Richard, Jennifer E; Eerola, Kim; López-Ferreras, Lorena; Banke, Elin; Hansson, Caroline; Nissbrandt, Hans; Berqquist, Filip; Gribble, Fiona M; Reimann, Frank; Wernstedt Asterholm, Ingrid; Lamy, Christophe M; Skibicka, Karolina P

    2017-04-01

    Glucagon-like peptide 1 (GLP-1) and serotonin play critical roles in energy balance regulation. Both systems are exploited clinically as antiobesity strategies. Surprisingly, whether they interact in order to regulate energy balance is poorly understood. Here we investigated mechanisms by which GLP-1 and serotonin interact at the level of the central nervous system. Serotonin depletion impaired the ability of exendin-4, a clinically used GLP-1 analog, to reduce body weight in rats, suggesting that serotonin is a critical mediator of the energy balance impact of GLP-1 receptor (GLP-1R) activation. Serotonin turnover and expression of 5-hydroxytryptamine (5-HT) 2A (5-HT2A) and 5-HT2C serotonin receptors in the hypothalamus were altered by GLP-1R activation. We demonstrate that the 5-HT2A, but surprisingly not the 5-HT2C, receptor is critical for weight loss, anorexia, and fat mass reduction induced by central GLP-1R activation. Importantly, central 5-HT2A receptors are also required for peripherally injected liraglutide to reduce feeding and weight. Dorsal raphe (DR) harbors cell bodies of serotonin-producing neurons that supply serotonin to the hypothalamic nuclei. We show that GLP-1R stimulation in DR is sufficient to induce hypophagia and increase the electrical activity of the DR serotonin neurons. Finally, our results disassociate brain metabolic and emotionality pathways impacted by GLP-1R activation. This study identifies serotonin as a new critical neural substrate for GLP-1 impact on energy homeostasis and expands the current map of brain areas impacted by GLP-1R activation.

  4. SDF-1α/CXCL12 enhances GABA and glutamate synaptic activity at serotonin neurons in the rat dorsal raphe nucleus

    PubMed Central

    Heinisch, Silke; Kirby, Lynn G.

    2009-01-01

    Summary The serotonin (5-hydroxytryptamine; 5-HT) system has a well-characterized role in depression. Recent reports describe comorbidities of mood-immune disorders, suggesting an immunological component may contribute to the pathogenesis of depression as well. Chemokines, immune proteins which mediate leukocyte trafficking, and their receptors are widely distributed in the brain, mediate neuronal patterning, and modulate various neuropathologies. The purpose of this study was to investigate the neuroanatomical relationship and functional impact of the chemokine stromal cell-derived factor-1α/CXCL12 and its receptor, CXCR4, on the serotonin dorsal raphe nucleus (DRN) system in the rat using anatomical and electrophysiological techniques. Immunohistochemical analysis indicates that over 70% of 5-HT neurons colocalize with CXCL12 and CXCR4. At a subcellular level, CXCL12 localizes throughout the cytoplasm whereas CXCR4 concentrates to the outer membrane and processes of 5-HT neurons. CXCL12 and CXCR4 also colocalize on individual DRN cells. Furthermore, electrophysiological studies demonstrate CXCL12 depolarization of 5-HT neurons indirectly via glutamate synaptic inputs. CXCL12 also enhances the frequency of spontaneous inhibitory and excitatory postsynaptic currents (sIPSC and sEPSC). CXCL12 concentration-dependently increases evoked IPSC amplitude and decreases evoked IPSC paired-pulse ratio selectively in 5-HT neurons, effects blocked by the CXCR4 antagonist AMD3100. These data indicate presynaptic enhancement of GABA and glutamate release at 5-HT DRN neurons by CXCL12. Immunohistochemical analysis further shows CXCR4 localization to DRN GABA neurons, providing an anatomical basis for CXCL12 effects on GABA release. Thus, CXCL12 indirectly modulates 5-HT neurotransmission via GABA and glutamate synaptic afferents. Future therapies targeting CXCL12 and other chemokines may treat serotonin related mood disorders, particularly depression experienced by immune

  5. Further pharmacological characterization of 5-HT2C receptor agonist-induced inhibition of 5-HT neuronal activity in the dorsal raphe nucleus in vivo

    PubMed Central

    Quérée, P; Peters, S; Sharp, T

    2009-01-01

    Background and purpose: Recent experiments using non-selective 5-hydroxytryptamine (5-HT)2C receptor agonists including WAY 161503 suggested that midbrain 5-HT neurones are under the inhibitory control of 5-HT2C receptors, acting via neighbouring gamma-aminobutyric acid (GABA) neurones. The present study extended this pharmacological characterization by comparing the actions of WAY 161503 with the 5-HT2C receptor agonists, Ro 60-0275 and 1-(3-chlorophenyl) piperazine (mCPP), as well as the non-selective 5-HT agonist lysergic acid diethylamide (LSD) and the 5-HT releasing agent 3,4-methylenedioxymethamphetamine (MDMA). Experimental approach: 5-HT neuronal activity was measured in the dorsal raphe nucleus (DRN) using extracellular recordings in anaesthetized rats. The activity of DRN GABA neurones was assessed using double-label immunohistochemical measurements of Fos and glutamate decarboxylase (GAD). Key results: Ro 60-0175, like WAY 161503, inhibited 5-HT neurone firing, and the 5-HT2C antagonist SB 242084 reversed this effect. mCPP also inhibited 5-HT neurone firing (∼60% neurones) in a SB 242084-reversible manner. LSD inhibited 5-HT neurone firing; however, this effect was not altered by either SB 242084 or the 5-HT2A/C receptor antagonist ritanserin but was reversed by the 5-HT1A receptor antagonist WAY 100635. Similarly, MDMA inhibited 5-HT neurone firing in a manner reversible by WAY 100635, but not SB 242084 or ritanserin. Finally, both Ro 60-0275 and mCPP, like WAY 161503, increased Fos expression in GAD-positive DRN neurones. Conclusions and implications: These data strengthen the hypothesis that midbrain 5-HT neurones are under the inhibitory control of 5-HT2C receptors, and suggest that the 5-HT2C agonists Ro 60-0175, mCPP and WAY 161503, but not LSD or MDMA, are useful probes of the mechanism(s) involved. PMID:19845681

  6. Cigarette Smoking and Tryptophan Hydroxylase 2 mRNA in the Dorsal Raphe Nucleus in Suicides

    PubMed Central

    Bach, Helene; Arango, Victoria; Kassir, Suham A.; Dwork, Andrew J.; Mann, J. John; Underwood, Mark D.

    2016-01-01

    Cigarette smoking is associated with suicide and mood disorders and stimulates serotonin release. Tryptophan hydroxylase (TPH2) synthesizes serotonin and is over-expressed in suicides. We determined whether smoking is associated with TPH2 mRNA in suicides and controls. TPH2 mRNA was measured postmortem in the dorsal raphe nucleus (DRN) of controls (N=26, 17 nonsmokers and nine smokers) and suicides (N=23, 5 nonsmokers and 18 smokers). Psychiatric history was obtained by psychological autopsy. TPH2 mRNA was greater in suicide nonsmokers than suicide smokers, control smokers and control nonsmokers (p=0.006). There was more TPH2 mRNA throughout the DRN. Smoking interferes with the TPH2 mRNA increase observed in suicide nonsmokers. The absence of altered TPH2 expression in non-suicide smokers suggests no pharmacological effect of smoking. PMID:26954509

  7. Ovarian Steroids Increase PSD-95 Expression and Dendritic Spines in the Dorsal Raphe of Ovariectomized Macaques

    PubMed Central

    Rivera, Heidi M.; Bethea, Cynthia L.

    2014-01-01

    Estradiol (E) and progesterone (P) promote spinogenesis in several brain areas. Intracellular signaling cascades that promote spinogenesis involve RhoGTPases, glutamate signaling and synapse assembly. We found that in serotonin neurons, E±P administration increases (a) gene and protein expression of RhoGTPases, (b) gene expression of glutamate receptors (c) gene expression of pivotal synapse assembly proteins. Therefore, in this study we determined whether structural changes in dendritic spines in the dorsal raphe follow the observed changes in gene and protein expression. Dendritic spines were examined with immunogold silver staining of a spine marker protein, postsynaptic density-95 (PSD-95) and with Golgi staining. In the PSD-95 study, adult Ovx monkeys received placebo, E, P, or E+P for 1 month (n=3/group). Sections were immunostained for PSD-95 and the number of PSD-95-positive puncta was determined with stereology. E, P and E+P treatment significantly increased the total number of PSD-95-positive puncta (ANOVA, P=0.04). In the Golgi study, adult Ovx monkeys received placebo, E or E+P for 1 month (n=3–4) and the midbrain was Golgi-stained. A total of 80 neurons were analyzed with Neurolucida software. There was a significant difference in spine density that depended on branch order (two-way ANOVA). E+P treatment significantly increased spine density in higher-order (3–5°) dendritic branches relative to Ovx group (Bonferroni, P<0.05). In summary, E+P leads to the elaboration of dendritic spines on dorsal raphe neurons. The ability of E to induce PSD-95, but not actual spines, suggests either a sampling or time lag issue. Increased spinogenesis on serotonin dendrites would facilitate excitatory glutamatergic input and, in turn, increase serotonin neurotransmission throughout the brain. PMID:23959764

  8. Ovarian steroids increase PSD-95 expression and dendritic spines in the dorsal raphe of ovariectomized macaques.

    PubMed

    Rivera, Heidi M; Bethea, Cynthia L

    2013-12-01

    Estradiol (E) and progesterone (P) promote spinogenesis in several brain areas. Intracellular signaling cascades that promote spinogenesis involve RhoGTPases, glutamate signaling and synapse assembly. We found that in serotonin neurons, E ± P administration increases (a) gene and protein expression of RhoGTPases, (b) gene expression of glutamate receptors, and (c) gene expression of pivotal synapse assembly proteins. Therefore, in this study we determined whether structural changes in dendritic spines in the dorsal raphe follow the observed changes in gene and protein expression. Dendritic spines were examined with immunogold silver staining of a spine marker protein, postsynaptic density-95 (PSD-95) and with Golgi staining. In the PSD-95 study, adult Ovx monkeys received placebo, E, P, or E + P for 1 month (n = 3/group). Sections were immunostained for PSD-95 and the number of PSD-95-positive puncta was determined with stereology. E, P, and E + P treatment significantly increased the total number of PSD-95-positive puncta (ANOVA, P = 0.04). In the golgi study, adult Ovx monkeys received placebo, E or E + P for 1 month (n = 3-4) and the midbrain was golgi-stained. A total of 80 neurons were analyzed with Neurolucida software. There was a significant difference in spine density that depended on branch order (two-way ANOVA). E + P treatment significantly increased spine density in higher-order (3°-5°) dendritic branches relative to Ovx group (Bonferroni, P < 0.05). In summary, E + P leads to the elaboration of dendritic spines on dorsal raphe neurons. The ability of E to induce PSD-95, but not actual spines, suggests either a sampling or time lag issue. Increased spinogenesis on serotonin dendrites would facilitate excitatory glutamatergic input and, in turn, increase serotonin neurotransmission throughout the brain. Copyright © 2013 Wiley Periodicals, Inc.

  9. [The role of neurochemical mechanisms of the dorsal raphe nucleus in various models of anxiety states in rats].

    PubMed

    Talalaenko, A N

    1989-01-01

    Dopamine and serotonin microinjection in the dorsal raphe nucleus of rats does not influence the alarm state in the test of "threatening situation" avoidance, but increases or weakens the state of alarm in the rest of "illuminated site" avoidance. Local injection of GABA in this midbrain formation weakens the alarm state in the test of "threatening situation" avoidance but is not effective in the test of "illuminated site" avoidance. Chemical stimulation of the raphe nucleus by glutaminic acid does not influence the two different experimentally modelled states of alarm, but modulates the mechanisms controlling the instinct of darkness preference by rats.

  10. Functional connectivity of the dorsal and median raphe nuclei at rest.

    PubMed

    Beliveau, Vincent; Svarer, Claus; Frokjaer, Vibe G; Knudsen, Gitte M; Greve, Douglas N; Fisher, Patrick M

    2015-08-01

    Serotonin (5-HT) is a neurotransmitter critically involved in a broad range of brain functions and implicated in the pathophysiology of neuropsychiatric illnesses including major depression, anxiety and sleep disorders. Despite being widely distributed throughout the brain, there is limited knowledge on the contribution of 5-HT to intrinsic brain activity. The dorsal raphe (DR) and median raphe (MR) nuclei are the source of most serotonergic neurons projecting throughout the brain and thus provide a compelling target for a seed-based probe of resting-state activity related to 5-HT. Here we implemented a novel multimodal neuroimaging approach for investigating resting-state functional connectivity (FC) between DR and MR and cortical, subcortical and cerebellar target areas. Using [(11)C]DASB positron emission tomography (PET) images of the brain serotonin transporter (5-HTT) combined with structural MRI from 49 healthy volunteers, we delineated DR and MR and performed a seed-based resting-state FC analysis. The DR and MR seeds produced largely similar FC maps: significant positive FC with brain regions involved in cognitive and emotion processing including anterior cingulate, amygdala, insula, hippocampus, thalamus, basal ganglia and cerebellum. Significant negative FC was observed within pre- and postcentral gyri for the DR but not for the MR seed. We observed a significant association between DR and MR FC and regional 5-HTT binding. Our results provide evidence for a resting-state network related to DR and MR and comprising regions receiving serotonergic innervation and centrally involved in 5-HT related behaviors including emotion, cognition and reward processing. These findings provide a novel advance in estimating resting-state FC related to 5-HT signaling, which can benefit our understanding of its role in behavior and neuropsychiatric illnesses.

  11. Functional connectivity of the dorsal and median raphe nuclei at rest

    PubMed Central

    Beliveau, Vincent; Svarer, Claus; Frokjaer, Vibe G.; Knudsen, Gitte M.; Greve, Douglas N.; Fisher, Patrick M.

    2015-01-01

    Serotonin (5-HT) is a neurotransmitter critically involved in a broad range of brain functions and implicated in the pathophysiology of neuropsychiatric illnesses including major depression, anxiety and sleep disorders. Despite being widely distributed throughout the brain, there is limited knowledge on the contribution of 5-HT to intrinsic brain activity. The dorsal raphe (DR) and median raphe (MR) nuclei are the source of most serotonergic neurons projecting throughout the brain and thus provide a compelling target for a seed-based probe of resting-state activity related to 5-HT. Here we implemented a novel multimodal neuroimaging approach for investigating resting-state functional connectivity (FC) between DR and MR and cortical, subcortical and cerebellar target areas. Using [11C]DASB positron emission tomography (PET) images of the brain serotonin transporter (5-HTT) combined with structural MRI from 49 healthy volunteers, we delineated DR and MR and performed a seed-based resting-state FC analysis. The DR and MR seeds produced largely similar FC maps: significant positive FC with brain regions involved in cognitive and emotion processing including anterior cingulate, amygdala, insula, hippocampus, thalamus, basal ganglia and cerebellum. Significant negative FC was observed within pre- and postcentral gyri for the DR but not for the MR seed. We observed a significant association between DR and MR FC and regional 5-HTT binding. Our results provide evidence for a resting-state network related to DR and MR and comprising regions receiving serotonergic innervation and centrally involved in 5-HT related behaviors including emotion, cognition and reward processing. These findings provide a novel advance in estimating resting-state FC related to 5-HT signaling, which can benefit our understanding of its role in behavior and neuropsychiatric illnesses. PMID:25963733

  12. The role of the dorsal raphe nucleus in the development, expression and treatment of LID in hemiparkinsonian rats

    PubMed Central

    Eskow, Karen L.; Dupre, Kristin B.; Barnum, Christopher J.; Dickinson, Sando O.; Park, John Y.; Bishop, Christopher

    2009-01-01

    Convergent evidence indicates that in later stages of Parkinson's disease raphestriatal serotonin neurons compensate for the loss of nigrostriatal dopamine neurons by converting and releasing dopamine derived from exogenous administration of the pharmacotherapeutic L-3,4-dihydroxyphenyl-L-alanine (L-DOPA). Because the serotonin system is not equipped with dopamine autoregulatory mechanisms, it has been postulated that raphe-mediated striatal dopamine release may fluctuate dramatically. These fluctuations may portend the development of abnormal involuntary movements called L-DOPA-induced dyskinesia (LID). As such, it has been hypothesized that reducing the activity of raphestriatal neurons could dampen supraphysiological stimulation of striatal dopamine receptors thereby alleviating LID. To directly address this, the current study employed the rodent model of LID to investigate the contribution of the rostral raphe nuclei (RRN) in the development, expression and treatment of LID. In the first study, dual serotonin/dopamine selective lesions of the RRN and medial forebrain bundle, respectively, verified that the RRN are essential for the development of LID. In a direct investigation into the neuroanatomical specificity of these effects, microinfusions of ±8-OH-DPAT into the intact dorsal raphe nucleus dose-dependently attenuated the expression of LID without affecting the anti-parkinsonian efficacy of L-DOPA. These current findings reveal the integral contribution of the RRN in the development and expression of LID and implicate a prominent role for dorsal raphe 5-HT1AR in the efficacious properties of 5-HT1AR agonists. PMID:19309758

  13. Acute selective serotonin reuptake inhibitors regulate the dorsal raphe nucleus causing amplification of terminal serotonin release.

    PubMed

    Dankoski, Elyse C; Carroll, Susan; Wightman, Robert Mark

    2016-01-09

    Selective serotonin reuptake inhibitors (SSRIs) were designed to treat depression by increasing serotonin levels throughout the brain via inhibition of clearance from the extracellular space. Although increases in serotonin levels are observed after acute SSRI exposure, 3-6 weeks of continuous use is required for relief from the symptoms of depression. Thus, it is now believed that plasticity in multiple brain systems that are downstream of serotonergic inputs contributes to the therapeutic efficacy of SSRIs. The onset of antidepressant effects also coincides with desensitization of somatodendritic serotonin autoreceptors in the dorsal raphe nucleus (DRN), suggesting that disrupting inhibitory feedback within the serotonin system may contribute to the therapeutic effects of SSRIs. Previously, we showed that chronic SSRI treatment caused a frequency-dependent facilitation of serotonin signaling that persisted in the absence of uptake inhibition. In this work, we use in vivo fast-scan cyclic voltammetry in mice to investigate a similar facilitation after a single treatment of the SSRI citalopram hydrobromide. Acute citalopram hydrobromide treatment resulted in frequency-dependent increases of evoked serotonin release in the substantia nigra pars reticulata. These increases were independent of changes in uptake velocity, but required SERT expression. Using microinjections, we show that the frequency-dependent enhancement in release is because of SERT inhibition in the DRN, demonstrating that SSRIs can enhance serotonin release by inhibiting uptake in a location distal to the terminal release site. The novel finding that SERT inhibition can disrupt modulatory mechanisms at the level of the DRN to facilitate serotonin release will help future studies investigate serotonin's role in depression and motivated behavior. In this work, stimulations of the dorsal raphe nucleus (DRN) evoke serotonin release that is recorded in the substantia nigra pars reticulata (SNpr) using

  14. Effects of obesogenic diet and estradiol on dorsal raphe gene expression in old female macaques

    PubMed Central

    Mueller, Kevin; Reddy, Arubala P.; Kohama, Steven G.; Urbanski, Henryk F.

    2017-01-01

    expression in the dorsal raphe. These results suggest that with regard to function and viability in the dorsal raphe, HT may not be as beneficial for obese women as normal weight women. PMID:28628658

  15. Age differences in the impact of forced swimming test on serotonin transporter levels in lateral septum and dorsal raphe

    PubMed Central

    2014-01-01

    Background Forced swimming test (FST) is an animal model which evaluates behavioral despair and the effect of antidepressants such as the selective serotonin reuptake inhibitors; the FST modifies the expression of some receptors related to antidepressant response, but it is not known whether serotonin transporter (SERT), their main target, is affected by this test in animals of different ages. Antidepressant response has shown age-dependent variations which could be associated with SERT expression. The aim of the present study was to analyze changes in the SERT immunoreactivity (SERT-IR) in dorsal raphe and lateral septum of male rats from different age groups with or without behavioral despair induced by their exposure to the FST, since these two structures are related to the expression of this behavior. Methods Prepubertal (24 PN), pubertal (40 PN), young adult (3–5 months) and middle-aged (12 months) male rats were assigned to a control group (non-FST) or depressed group (FST, two sessions separated by 24 h). Changes in SERT-IR in dorsal raphe and lateral septum were determined with immunofluorescence. Results Pubertal and middle-aged rats showed higher levels of immobility behavior compared to prepubertal rats on the FST. SERT-IR showed an age-dependent increase followed by a moderate decrease in middle-aged rats in both structures; a decreased in SERT-IR in lateral septum and dorsal raphe of pubertal rats was observed after the FST. Conclusions Age differences were observed in the SERT-IR of structures related to behavioral despair; SERT expression was modified by the FST in lateral septum and dorsal raphe of pubertal rats. PMID:24490994

  16. Elucidation of The Behavioral Program and Neuronal Network Encoded by Dorsal Raphe Serotonergic Neurons.

    PubMed

    Urban, Daniel J; Zhu, Hu; Marcinkiewcz, Catherine A; Michaelides, Michael; Oshibuchi, Hidehiro; Rhea, Darren; Aryal, Dipendra K; Farrell, Martilias S; Lowery-Gionta, Emily; Olsen, Reid H J; Wetsel, William C; Kash, Thomas L; Hurd, Yasmin L; Tecott, Laurence H; Roth, Bryan L

    2016-04-01

    Elucidating how the brain's serotonergic network mediates diverse behavioral actions over both relatively short (minutes-hours) and long period of time (days-weeks) remains a major challenge for neuroscience. Our relative ignorance is largely due to the lack of technologies with robustness, reversibility, and spatio-temporal control. Recently, we have demonstrated that our chemogenetic approach (eg, Designer Receptors Exclusively Activated by Designer Drugs (DREADDs)) provides a reliable and robust tool for controlling genetically defined neural populations. Here we show how short- and long-term activation of dorsal raphe nucleus (DRN) serotonergic neurons induces robust behavioral responses. We found that both short- and long-term activation of DRN serotonergic neurons induce antidepressant-like behavioral responses. However, only short-term activation induces anxiogenic-like behaviors. In parallel, these behavioral phenotypes were associated with a metabolic map of whole brain network activity via a recently developed non-invasive imaging technology DREAMM (DREADD Associated Metabolic Mapping). Our findings reveal a previously unappreciated brain network elicited by selective activation of DRN serotonin neurons and illuminate potential therapeutic and adverse effects of drugs targeting DRN neurons.

  17. Nicotine withdrawal upregulates nitrergic and galaninergic activity in the rat dorsal raphe nucleus and locus coeruleus.

    PubMed

    Okere, Chuma O; Waterhouse, Barry D

    2013-03-01

    The dorsal raphe nucleus (DRN), a major source of forebrain serotonin, mediates various neural functions including anxiety. The nucleus locus coeruleus (LC) is likewise involved in mediating central components of the stress response and anxiety. An anxiety-reducing effect is widely believed to underlie many cases of nicotine dependence. While much is known about nicotine-serotonin interactions, little is known about how nicotine engages the DRN non-serotonergic domain in specific physiological functions that influence organismal behavior. The aim of this study was to determine how chronic nicotine withdrawal influences neuronal nitric oxide (NO) synthase (nNOS) and galanin immunoreactivity in the DRN and LC of adult rats. Compared with saline, nicotine increased nicotinamide adenine dinucleotide phosphate diaphorase profiles within distinct DRN subregions and also enhanced intensity in nNOS and galanin cell bodies in the rostral DRN as well as galanin in the LC. Nicotine-induced nNOS/galanin staining of somata was abundant in the rostral ventromedial DRN. Galanin-positive terminals surrounded nNOS-containing cell bodies in the DRN lateral wing subregions. These observations suggest that the DRN NOS-galanin domain and galanin in the LC are engaged in the organism's neural adaptation to chronic nicotine exposure. Hence NO and galanin synthesized or released within the DRN and LC or at the respective target sites might regulate the whole animal behavioral response to nicotine exposure.

  18. Elucidation of The Behavioral Program and Neuronal Network Encoded by Dorsal Raphe Serotonergic Neurons

    PubMed Central

    Urban, Daniel J; Zhu, Hu; Marcinkiewcz, Catherine A; Michaelides, Michael; Oshibuchi, Hidehiro; Rhea, Darren; Aryal, Dipendra K; Farrell, Martilias S; Lowery-Gionta, Emily; Olsen, Reid H J; Wetsel, William C; Kash, Thomas L; Hurd, Yasmin L; Tecott, Laurence H; Roth, Bryan L

    2016-01-01

    Elucidating how the brain's serotonergic network mediates diverse behavioral actions over both relatively short (minutes–hours) and long period of time (days–weeks) remains a major challenge for neuroscience. Our relative ignorance is largely due to the lack of technologies with robustness, reversibility, and spatio-temporal control. Recently, we have demonstrated that our chemogenetic approach (eg, Designer Receptors Exclusively Activated by Designer Drugs (DREADDs)) provides a reliable and robust tool for controlling genetically defined neural populations. Here we show how short- and long-term activation of dorsal raphe nucleus (DRN) serotonergic neurons induces robust behavioral responses. We found that both short- and long-term activation of DRN serotonergic neurons induce antidepressant-like behavioral responses. However, only short-term activation induces anxiogenic-like behaviors. In parallel, these behavioral phenotypes were associated with a metabolic map of whole brain network activity via a recently developed non-invasive imaging technology DREAMM (DREADD Associated Metabolic Mapping). Our findings reveal a previously unappreciated brain network elicited by selective activation of DRN serotonin neurons and illuminate potential therapeutic and adverse effects of drugs targeting DRN neurons. PMID:26383016

  19. Corticotropin-releasing factor in the dorsal raphe nucleus: Linking stress coping and addiction.

    PubMed

    Valentino, Rita J; Lucki, Irwin; Van Bockstaele, Elisabeth

    2010-02-16

    Addiction and stress are linked at multiple levels. Drug abuse is often initiated as a maladaptive mechanism for coping with stress. It is maintained in part by negative reinforcement to prevent the aversive consequences of stress associated with abstinence. Finally, stress is a major factor leading to relapse in subjects in which drug seeking behavior has extinguished. These associations imply overlapping or converging neural circuits and substrates that underlie the processes of addiction and the expression of the stress response. Here we discuss the major brain serotonin (5-HT) system, the dorsal raphe nucleus (DRN)-5-HT system as a point of convergence that links these processes and how the stress-related neuropeptide, corticotropin-releasing factor (CRF) directs this by a bimodal regulation of DRN neuronal activity. The review begins by describing a structural basis for CRF regulation of the DRN-5-HT system. This is followed by a review of the effects of CRF and stress on DRN function based on electrophysiological and microdialysis studies. The concept that multiple CRF receptor subtypes in the DRN facilitate distinct coping behaviors is reviewed with recent evidence for a unique cellular mechanism by which stress history can determine the type of coping behavior. Finally, work on CRF regulation of the DRN-5-HT system is integrated with literature on the role of 5-HT-dopamine interactions in addiction.

  20. Extrasynaptic Glycine Receptors of Rodent Dorsal Raphe Serotonergic Neurons: A Sensitive Target for Ethanol

    PubMed Central

    Maguire, Edward P; Mitchell, Elizabeth A; Greig, Scott J; Corteen, Nicole; Balfour, David J K; Swinny, Jerome D; Lambert, Jeremy J; Belelli, Delia

    2014-01-01

    Alcohol abuse is a significant medical and social problem. Several neurotransmitter systems are implicated in ethanol's actions, with certain receptors and ion channels emerging as putative targets. The dorsal raphe (DR) nucleus is associated with the behavioral actions of alcohol, but ethanol actions on these neurons are not well understood. Here, using immunohistochemistry and electrophysiology we characterize DR inhibitory transmission and its sensitivity to ethanol. DR neurons exhibit inhibitory ‘phasic' post-synaptic currents mediated primarily by synaptic GABAA receptors (GABAAR) and, to a lesser extent, by synaptic glycine receptors (GlyR). In addition to such phasic transmission mediated by the vesicular release of neurotransmitter, the activity of certain neurons may be governed by a ‘tonic' conductance resulting from ambient GABA activating extrasynaptic GABAARs. However, for DR neurons extrasynaptic GABAARs exert only a limited influence. By contrast, we report that unusually the GlyR antagonist strychnine reveals a large tonic conductance mediated by extrasynaptic GlyRs, which dominates DR inhibition. In agreement, for DR neurons strychnine increases their input resistance, induces membrane depolarization, and consequently augments their excitability. Importantly, this glycinergic conductance is greatly enhanced in a strychnine-sensitive fashion, by behaviorally relevant ethanol concentrations, by drugs used for the treatment of alcohol withdrawal, and by taurine, an ingredient of certain ‘energy drinks' often imbibed with ethanol. These findings identify extrasynaptic GlyRs as critical regulators of DR excitability and a novel molecular target for ethanol. PMID:24264816

  1. PKC in rat dorsal raphe nucleus plays a key role in sleep-wake regulation.

    PubMed

    Li, Sheng-Jie; Cui, Su-Ying; Zhang, Xue-Qiong; Yu, Bin; Sheng, Zhao-Fu; Huang, Yuan-Li; Cao, Qing; Xu, Ya-Ping; Lin, Zhi-Ge; Yang, Guang; Cui, Xiang-Yu; Zhang, Yong-He

    2015-12-03

    Studies suggest a tight relationship between protein kinase C (PKC) and circadian clock. However, the role of PKC in sleep-wake regulation remains unclear. The present study was conducted to investigate the role of PKC signaling in sleep-wake regulation in the rat. Our results showed that the phosphorylation level of PKC in dorsal raphe nucleus (DRN) was decreased after 6h sleep deprivation, while no alterations were found in ventrolateral preoptic nucleus (VLPO) or locus coeruleus (LC). Microinjection of a pan-PKC inhibitor, chelerythrine chloride (CHEL, 5 or 10nmol), into DRN of freely moving rats promoted non rapid eye movement sleep (NREMS) without influences on rapid eye movement sleep (REMS). Especially, CHEL application at 5nmol increased light sleep (LS) time while CHEL application at 10nmol increased slow wave sleep (SWS) time and percentage. On the other hand, microinjection of CaCl2 into DRN not only increased the phosphorylation level of PKC, but also reduced NREMS time, especially SWS time and percentage. While CHEL abolished the inhibitory effect of CaCl2 on NREMS and SWS. These data provide the first direct evidence that inhibition of intracellular PKC signaling in DRN could increase NREMS time including SWS time and percentage, while activation of PKC could suppress NREMS and reduce SWS time and percentage. These novel findings further our understanding of the basic cellular and molecular mechanisms of sleep-wake regulation. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Serotonergic versus non-serotonergic dorsal raphe projection neurons: differential participation in reward circuitry

    PubMed Central

    McDevitt, Ross A; Tiran-Cappello, Alix; Shen, Hui; Balderas, Israela; Britt, Jonathan P; Marino, Rosa AM; Chung, Stephanie L; Richie, Christopher T; Harvey, Brandon K; Bonci, Antonello

    2014-01-01

    Summary The dorsal raphe nucleus (DRN) contains the largest group of serotonin-producing neurons in the brain and projects to regions controlling reward. Although pharmacological studies suggest that serotonin inhibits reward-seeking, electrical stimulation of the DRN strongly reinforces instrumental behavior. Here, we provide a targeted assessment of the behavioral, anatomical, and electrophysiological contributions of serotonergic and non-serotonergic DRN neurons to reward processes. To explore DRN heterogeneity, we used a simultaneous two-vector knockout/optogenetic stimulation strategy, as well as cre-induced and cre-silenced vectors in several cre-expressing transgenic mouse lines. We found that the DRN is capable of reinforcing behavior primarily via non-serotonergic neurons, whose main projection target is the ventral tegmental area (VTA). Furthermore, these non-serotonergic projections provide glutamatergic excitation of VTA dopamine neurons and account for a large majority of the DRN-VTA pathway. These findings help to resolve apparent discrepancies between the roles of serotonin versus the DRN in behavioral reinforcement. PMID:25242321

  3. Glutamate input in the dorsal raphe nucleus as a determinant of escalated aggression in male mice.

    PubMed

    Takahashi, Aki; Lee, Ray X; Iwasato, Takuji; Itohara, Shigeyoshi; Arima, Hiroshi; Bettler, Bernhard; Miczek, Klaus A; Koide, Tsuyoshi

    2015-04-22

    Although the dorsal raphe nucleus (DRN) has long been linked to neural control of aggression, little is known about the regulatory influences of the DRN when an animal engages in either adaptive species-typical aggressive behavior or escalated aggression. Therefore it is important to explore which neurotransmitter inputs into the DRN determine the escalation of aggression in male mice. Previously, we observed that microinjection of the GABAB receptor agonist baclofen into the DRN escalates aggressive behavior in male mice. Here, we used a serotonin (5-HT) neuron-specific GABAB receptor knock-out mouse to demonstrate that baclofen acts on nonserotonergic neurons to escalate aggression. Intra-DRN baclofen administration increased glutamate release, but did not alter GABA release, within the DRN. Microinjection of l-glutamate into the DRN escalated dose-dependently attack bites toward an intruder. In vivo microdialysis showed that glutamate release increased in the DRN during an aggressive encounter, and the level of glutamate was further increased when the animal was engaged in escalated aggressive behavior after social instigation. Finally, 5-HT release was increased within the DRN and also in the medial prefrontal cortex when animals were provoked by social instigation, and during escalated aggression after social instigation, but this increase in 5-HT release was not observed when animals were engaged in species-typical aggression. In summary, glutamate input into the DRN is enhanced during escalated aggression, which causes a phasic increase of 5-HT release from the DRN 5-HT neurons.

  4. Properties of I(A) in a neuron of the dorsal raphe nucleus.

    PubMed

    Penington, Nicholas J; Tuckwell, Henry C

    2012-04-17

    Voltage clamp data were analyzed in order to characterize the properties of the fast potassium transient current I(A) for a presumed serotonergic neuron of the rat dorsal raphe nucleus (DRN). We obtain maximal conductance, time constants of activation and inactivation, and the steady state activation and inactivation functions m(∞) and h(∞), as Boltzmann curves, defined by half-activation potentials and slope factors. I(A) is estimated as g¯(V-V(rev))m(4)h, with g¯=20.5nS. For activation, the half-activation potential is V(a)=-52.5mV with slope factor k(a)=16.5mV, whereas for inactivation the corresponding quantities are -91.5mV and -9.3mV. We discuss the results in terms of the corresponding properties of I(A) in other cell types and their possible relevance to pacemaking activity in cells of the DRN. Methods of identification of serotonergic DRN neurons and the nature of the K(v) channels underlying the A-type current are also discussed. Published by Elsevier B.V.

  5. Chronic L-dopa decreases serotonin neurons in a subregion of the dorsal raphe nucleus.

    PubMed

    Stansley, Branden J; Yamamoto, Bryan K

    2014-11-01

    L-Dopa (l-3,4-dihydroxyphenylalanine) is the precursor to dopamine and has become the mainstay therapeutic treatment for Parkinson's disease. Chronic L-dopa is administered to recover motor function in Parkinson's disease patients. However, drug efficacy decreases over time, and debilitating side effects occur, such as dyskinesia and mood disturbances. The therapeutic effect and some of the side effects of L-dopa have been credited to its effect on serotonin (5-HT) neurons. Given these findings, it was hypothesized that chronic L-dopa treatment decreases 5-HT neurons in the dorsal raphe nucleus (DRN) and the content of 5-HT in forebrain regions in a manner that is mediated by oxidative stress. Rats were treated chronically with l-dopa (6 mg/kg; twice daily) for 10 days. Results indicated that the number of 5-HT neurons was significantly decreased in the DRN after l-dopa treatment compared with vehicle. This effect was more pronounced in the caudal-extent of the dorsal DRN, a subregion found to have a significantly higher increase in the 3,4-dihydroxyphenylacetic acid/dopamine ratio in response to acute L-dopa treatment. Furthermore, pretreatment with ascorbic acid (400 mg/kg) or deprenyl (2 mg/kg) prevented the l-dopa-induced decreases in 5-HT neurons. In addition, 5-HT content was decreased significantly in the DRN and prefrontal cortex by l-dopa treatment, effects that were prevented by ascorbic acid pretreatment. Taken together, these data illustrate that chronic L-dopa causes a 5-HT neuron loss and the depletion of 5-HT content in a subregion of the DRN as well as in the frontal cortex through an oxidative-stress mechanism.

  6. Postnatal Treadmill Exercise Alleviates Prenatal Stress-Induced Anxiety in Offspring Rats by Enhancing Cell Proliferation Through 5-Hydroxytryptamine 1A Receptor Activation

    PubMed Central

    2016-01-01

    Purpose: Stress during pregnancy is a risk factor for the development of anxiety-related disorders in offspring later in life. The effects of treadmill exercise on anxiety-like behaviors and hippocampal cell proliferation were investigated using rats exposed to prenatal stress. Methods: Exposure of pregnant rats to a hunting dog in an enclosed room was used to induce stress. Anxiety-like behaviors of offspring were evaluated using the elevated plus maze test. Immunohistochemistry for the detection of 5-bromo-2ʹ- deoxyuridine and doublecortin (DCX) in the hippocampal dentate gyrus and 5-hydroxytryptamine 1A receptors (5-HT1A) in the dorsal raphe was conducted. Brain-derived neurotrophic factor (BDNF) and tyrosine kinase B (TrkB) levels in the hippocampus were evaluated by western blot analysis. Results: Offspring of maternal rats exposed to stress during pregnancy showed anxiety-like behaviors. Offspring also showed reduced expression of BDNF, TrkB, and DCX in the dentate gyrus, decreased cell proliferation in the hippocampus, and reduced 5-HT1A expression in the dorsal raphe. Postnatal treadmill exercise by offspring, but not maternal exercise during pregnancy, enhanced cell proliferation and expression of these proteins. Conclusions: Postnatal treadmill exercise ameliorated anxiety-like behaviors in offspring of stressed pregnant rats, and the alleviating effect of exercise on these behaviors is hypothesized to result from enhancement of cell proliferation through 5-HT1A activation in offspring rats. PMID:27230461

  7. Increase in antidromic excitability in presumed serotonergic dorsal raphe neurons during paradoxical sleep in the cat.

    PubMed

    Sakai, K; Crochet, S

    2001-04-20

    Putative serotonergic dorsal raphe (DRN) neurons display a dramatic state-related change in behaviour, discharging regularly at a high rate during waking and at progressively slower rates during slow-wave sleep (SWS) and ceasing firing during paradoxical sleep (PS). Using the antidromic latency technique and extracellular recording, we have examined the change in neuronal excitability of presumed serotonergic DRN neurons during the wake-sleep cycle in freely moving cats. We found that, under normal conditions, suprathreshold stimulation of the main ascending serotonergic pathway resulted in a marked decrease in both the magnitude and variability of antidromic latency during PS, while subthreshold stimulation led to a marked increase in antidromic responsiveness during PS compared with during other behavioural states. The antidromic latency shift resulted from a change in the delay between the initial segment (IS) and soma-dendritic (SD) spikes, the antidromic latency being inversely related to the interval between the stimulus and the preceding spontaneous action potential. A marked decrease in the magnitude and variability of antidromic latency was also seen following suppression of the spontaneous discharge of DRN neurons by application of 5-HT autoreceptor agonists or muscimol, a potent GABA agonist. A marked IS-SD delay or blockage of SD spikes was, however, seen in association with the PS occurring during recovery from 5-HT autoreceptor agonist or during muscimol application. The present findings are discussed in the light of previous in vitro intracellular recording data and our recent findings of the disfacilitation mechanisms responsible for the cessation of discharge of DRN neurons during PS.

  8. Nicotine increases GABAergic input on rat dorsal raphe serotonergic neurons through alpha7 nicotinic acetylcholine receptor.

    PubMed

    Hernández-Vázquez, F; Chavarría, K; Garduño, J; Hernández-López, S; Mihailescu, S P

    2014-12-15

    The dorsal raphe nucleus (DRN) contains large populations of serotonergic (5-HT) neurons. This nucleus receives GABAergic inhibitory afferents from many brain areas and from DRN interneurons. Both GABAergic and 5-HT DRN neurons express functional nicotinic acetylcholine receptors (nAChRs). Previous studies have demonstrated that nicotine increases 5-HT release and 5-HT DRN neuron discharge rate by stimulating postsynaptic nAChRs and by increasing glutamate and norepinephrine release inside DRN. However, the influence of nicotine on the GABAergic input to 5-HT DRN neurons was poorly investigated. Therefore, the aim of this work was to determine the effect of nicotine on GABAergic spontaneous inhibitory postsynaptic currents (sIPSCs) of 5-HT DRN neurons and the subtype of nAChR(s) involved in this response. Experiments were performed in coronal slices obtained from young Wistar rats. GABAergic sIPSCs were recorded from post hoc-identified 5-HT DRN neurons with the whole cell voltage patch-clamp technique. Administration of nicotine (1 μM) increased sIPSC frequency in 72% of identified 5-HT DRN neurons. This effect was not reproduced by the α4β2 nAChR agonist RJR-2403 and was not influenced by TTX (1 μM). It was mimicked by the selective agonist for α7 nAChR, PNU-282987, and exacerbated by the positive allosteric modulator of the same receptor, PNU-120596. The nicotine-induced increase in sIPSC frequency was independent on voltage-gated calcium channels and dependent on Ca(2+)-induced Ca(2+) release (CICR). These results demonstrate that nicotine increases the GABAergic input to most 5-HT DRN neurons, by activating α7 nAChRs and producing CICR in DRN GABAergic terminals.

  9. Effects of general anaesthetics on 5-HT neuronal activity in the dorsal raphe nucleus.

    PubMed

    McCardle, Caroline E; Gartside, Sarah E

    2012-03-01

    The ascending 5-HT system has been and continues to be the subject of much research. The majority of in vivo electrophysiological and neurochemical studies of 5-HT function in rodents have been conducted in animals under anaesthesia - usually chloral hydrate or urethane. However, the effects of anaesthetics, on 5-HT function have not been systematically investigated. Here we used in vitro electrophysiology in dorsal raphe slices, to determine the effects of anaesthetically relevant concentrations of chloral hydrate (100 μM and 1 mM), urethane (10 and 30 mM), pentobarbitone (10 and 100 μM) and ketamine (10, 100 and 300 μM) on regulators of 5-HT firing activity. We examined i) basal firing (driven by α(1) adrenoceptors), ii) the excitatory response to N-methyl-d-aspartate (NMDA), iii) the 5-HT(1A) autoreceptor-mediated inhibitory response to 5-HT and iv) the GABA(A) receptor-mediated inhibitory response to 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridinyl-3-ol (THIP, gaboxadol). Pentobarbitone selectively enhanced the response to THIP. Ketamine decreased basal firing, attenuated the response to NMDA, and enhanced responses to both 5-HT and THIP. Chloral hydrate had marginal effects on basal firing, slightly attenuated the NMDA response, and enhanced both the 5-HT and THIP responses. Urethane increased basal firing, decreased the NMDA response, increased the response to THIP, but had no effect on the 5-HT response. Our data indicate that all anaesthetics tested significantly affect the regulators of 5-HT neuronal function. These findings will aid in the interpretation of previous reports of in vivo studies of the 5-HT system and will allow researchers to make a rational selection of anaesthetic for future studies.

  10. Dorsal Raphe 5-HT2C Receptor and GABA Networks Regulate Anxiety Produced by Cocaine Withdrawal

    PubMed Central

    Craige, Caryne P.; Lewandowski, Stacia; Kirby, Lynn G.; Unterwald, Ellen M.

    2015-01-01

    The serotonin system is intimately linked to both the mediation of anxiety and long-term effects of cocaine, potentially through interaction of inhibitory 5-HT2C receptor and gamma-aminobutyric acid (GABA) networks. This study characterized the function of the dorsal raphe (DR) 5-HT2C receptor and GABA network in anxiety produced by chronic cocaine withdrawal. C57BL/6 mice were injected with saline or cocaine (15 mg/kg) 3 times daily for 10 days, and tested on the elevated plus maze 30 minutes, 25 hours, or 7 days after the last injection. Cocaine-withdrawn mice showed heightened anxiety-like behavior at 25 hours of withdrawal, as compared to saline controls. Anxiety-like behavior was not different when mice were tested 30 minutes or 7 days after the last cocaine injection. Electrophysiology data revealed that serotonin cells from cocaine-withdrawn mice exhibited increased GABA inhibitory postsynaptic currents (IPSCs) in specific DR subregions dependent on withdrawal time (25 h or 7 d), an effect that was absent in cells from non-withdrawn mice (30 minutes after the last cocaine injection). Increased IPSC activity was restored to baseline levels following bath application of the 5-HT2C receptor antagonist, SB 242084. In a separate cohort of cocaine-injected mice at 25 hours of withdrawal, both global and intra-DR blockade of 5-HT2C receptors prior to elevated plus maze testing attenuated anxiety-like behavior. This study demonstrates that DR 5-HT2C receptor blockade prevents anxiety-like behavior produced by cocaine withdrawal, potentially through attenuation of heightened GABA activity, supporting a role for the 5-HT2C receptor in mediating anxiety produced by cocaine withdrawal. PMID:25656481

  11. Firing Properties of Genetically Identified Dorsal Raphe Serotonergic Neurons in Brain Slices

    PubMed Central

    Mlinar, Boris; Montalbano, Alberto; Piszczek, Lukasz; Gross, Cornelius; Corradetti, Renato

    2016-01-01

    Tonic spiking of serotonergic neurons establishes serotonin levels in the brain. Since the first observations, slow regular spiking has been considered as a defining feature of serotonergic neurons. Recent studies, however, have revealed the heterogeneity of serotonergic neurons at multiple levels, comprising their electrophysiological properties, suggesting the existence of functionally distinct cellular subpopulations. In order to examine in an unbiased manner whether serotonergic neurons of the dorsal raphe nucleus (DRN) are heterogeneous, we used a non-invasive loose-seal cell-attached method to record α1 adrenergic receptor-stimulated spiking of a large sample of neurons in brain slices obtained from transgenic mice lines that express fluorescent marker proteins under the control of serotonergic system-specific Tph2 and Pet-1 promoters. We found wide homogeneous distribution of firing rates, well fitted by a single Gaussian function (r2 = 0.93) and independent of anatomical location (P = 0.45), suggesting that in terms of intrinsic firing properties, serotonergic neurons in the DRN represent a single cellular population. Characterization of the population in terms of spiking regularity was hindered by its dependence on the firing rate. For instance, the coefficient of variation of the interspike intervals (ISI), a common measure of spiking irregularity, is of limited usefulness since it correlates negatively with the firing rate (r = −0.33, P < 0.0001). Nevertheless, the majority of neurons exhibited regular, pacemaker-like activity, with coefficient of variance of the ISI lower than 0.5 in ~97% of cases. Unexpectedly, a small percentage of neurons (~1%) exhibited a particular spiking pattern, characterized by low frequency (~0.02–0.1 Hz) oscillations in the firing rate. Transitions between regular and oscillatory firing were observed, suggesting that the oscillatory firing is an alternative firing pattern of serotonergic neurons. PMID:27536220

  12. OPIATE EXPOSURE AND WITHDRAWAL DYNAMICALLY REGULATE mRNA EXPRESSION IN THE SEROTONERGIC DORSAL RAPHE NUCLEUS

    PubMed Central

    Lunden, Jason; Kirby, Lynn G.

    2013-01-01

    Previous results from our lab suggest that hypofunctioning of the serotonergic (5-HT) dorsal raphe nucleus (DRN) is involved in stress-induced opiate reinstatement. To further investigate the effects of morphine dependence and withdrawal on the 5-HT DRN system, we measured gene expression at the level of mRNA in the DRN during a model of morphine dependence, withdrawal and post withdrawal stress exposure in rats. Morphine pellets were implanted for 72h and then either removed or animals were injected with naloxone to produce spontaneous or precipitated withdrawal, respectively. Animals exposed to these conditions exhibited withdrawal symptoms including weight loss, wet dog shakes and jumping behavior. Gene expression for brain-derived neurotrophic factor (BDNF), TrkB, corticotrophin releasing-factor (CRF)-R1, CRF-R2, GABAA-α1, μ-opioid receptor (MOR), 5-HT1A, tryptophan hydroxylase2 and the 5-HT transporter was then measured using quantitative real-time PCR at multiple time-points across the model of morphine exposure, withdrawal and post withdrawal stress. Expression levels of BDNF, TrkB and CRF-R1 mRNA were decreased during both morphine exposure and following seven days of withdrawal. CRF-R2 mRNA expression was elevated after seven days of withdrawal. 5-HT1A receptor mRNA expression was decreased following 3 hours of morphine exposure, while TPH2 mRNA expression was decreased after seven days of withdrawal with swim stress. There were no changes in the expression of GABAA-α1, MOR or 5-HT transporter mRNA. Collectively these results suggest that alterations in neurotrophin support, CRF-dependent stress signaling, 5-HT synthesis and release may underlie 5-HT DRN hypofunction that can potentially lead to stress-induced opiate relapse. PMID:24055683

  13. Neuropeptide Y signaling in the dorsal raphe nucleus inhibits male sexual behavior in mice.

    PubMed

    Inaba, A; Komori, Y; Muroi, Y; Kinoshita, K; Ishii, T

    2016-04-21

    Animals change their biological activities depending on their nutritional state. Reproductive functions, including sexual behavior, are suppressed under low-energy conditions; however, the underlying neuronal mechanism is poorly understood. Neuropeptide Y (NPY) is an orexigenic molecule released in response to low-energy conditions and has an inhibitory effect on sexual behavior. We examined how NPY is involved in energy state-dependent regulation of male sexual behavior. Mounting, intromission, and ejaculation were evaluated as parameters of sexual behavior. Almost all parameters indicated that fasting for 24h suppressed male sexual behavior. Intracerebroventricular injection of NPY inhibited sexual behavior in males that free-fed for 8h following 24-h fasting (fed males). We next examined whether the dorsal raphe nucleus (DRN), in which serotonergic (5-HT) neurons are distributed, is involved in NPY-mediated inhibition of male sexual behavior. NPY-positive processes immunoreactive for a presynaptic marker, synaptophysin, were distributed in the DRN of both fed and fasted males. Expression of the NPY Y1 receptor in 5-HT neurons was also observed. Direct injection of NPY or 8-OH-DPAT (a 5-HT1A receptor agonist that inhibits the activity of 5-HT neurons) into the DRN inhibited male sexual behavior in fed males. In contrast, injection of BIBP-3226, a NPY Y1 receptor antagonist, or (+)-DOI hydrochloride (DOI), a 5-HT2A/2C receptor agonist that activates 5-HT neurons, into the DRN partially recovered male sexual behavior in 24-h fasted males. These results suggest that NPY inhibits serotonergic neuronal activity via the Y1 receptor in the DRN, resulting in suppression of male sexual behavior in low-energy conditions. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

  14. Optogenetic activation of dorsal raphe serotonin neurons enhances patience for future rewards.

    PubMed

    Miyazaki, Kayoko W; Miyazaki, Katsuhiko; Tanaka, Kenji F; Yamanaka, Akihiro; Takahashi, Aki; Tabuchi, Sawako; Doya, Kenji

    2014-09-08

    Serotonin is a neuromodulator that is involved extensively in behavioral, affective, and cognitive functions in the brain. Previous recording studies of the midbrain dorsal raphe nucleus (DRN) revealed that the activation of putative serotonin neurons correlates with the levels of behavioral arousal [1], rhythmic motor outputs [2], salient sensory stimuli [3-6], reward, and conditioned cues [5-8]. The classic theory on serotonin states that it opposes dopamine and inhibits behaviors when aversive events are predicted [9-14]. However, the therapeutic effects of serotonin signal-enhancing medications have been difficult to reconcile with this theory [15, 16]. In contrast, a more recent theory states that serotonin facilitates long-term optimal behaviors and suppresses impulsive behaviors [17-21]. To test these theories, we developed optogenetic mice that selectively express channelrhodopsin in serotonin neurons and tested how the activation of serotonergic neurons in the DRN affects animal behavior during a delayed reward task. The activation of serotonin neurons reduced the premature cessation of waiting for conditioned cues and food rewards. In reward omission trials, serotonin neuron stimulation prolonged the time animals spent waiting. This effect was observed specifically when the animal was engaged in deciding whether to keep waiting and was not due to motor inhibition. Control experiments showed that the prolonged waiting times observed with optogenetic stimulation were not due to behavioral inhibition or the reinforcing effects of serotonergic activation. These results show, for the first time, that the timed activation of serotonin neurons during waiting promotes animals' patience to wait for a delayed reward.

  15. Dorsal Raphe Nucleus Down-Regulates Medial Prefrontal Cortex during Experience of Flow

    PubMed Central

    Ulrich, Martin; Keller, Johannes; Grön, Georg

    2016-01-01

    Previous neuroimaging studies have suggested that the experience of flow aligns with a relative increase in activation of the dorsal raphe nucleus (DRN), and relative activation decreases of the medial prefrontal cortex (MPFC) and of the amygdala (AMY). In the present study, Dynamic Causal Modeling (DCM) was used to explore effective connectivity between those brain regions. To test our hypothesis that the DRN causally down-regulates activity of the MPFC and/or of the AMY, 23 healthy male students solved mental arithmetic tasks of varying difficulty during functional magnetic resonance imaging. A “flow” condition, with task demands automatically balanced with participants’ skill level, was compared with conditions of “boredom” and “overload”. DCM models were constructed modeling full reciprocal endogenous connections between the DRN, the MPFC, the AMY, and the calcarine. The calcarine was included to allow sensory input to enter the system. Experimental conditions were modeled as exerting modulatory effects on various possible connections between the DRN, the MPFC, and the AMY, but not on self-inhibitory connections, yielding a total of 64 alternative DCM models. Model space was partitioned into eight families based on commonalities in the arrangement of the modulatory effects. Random effects Bayesian Model Selection (BMS) was applied to identify a possible winning family (and model). Although BMS revealed a clear winning family, an outstanding winning model could not be identified. Therefore, Bayesian Model Averaging was performed over models within the winning family to obtain representative DCM parameters for subsequent analyses to test our hypothesis. In line with our expectations, Bayesian averaged parameters revealed stronger down-regulatory influence of the DRN on the MPFC when participants experienced flow relative to control conditions. In addition, these condition-dependent modulatory effects significantly predicted participants

  16. Dorsal Raphe Nucleus Down-Regulates Medial Prefrontal Cortex during Experience of Flow.

    PubMed

    Ulrich, Martin; Keller, Johannes; Grön, Georg

    2016-01-01

    Previous neuroimaging studies have suggested that the experience of flow aligns with a relative increase in activation of the dorsal raphe nucleus (DRN), and relative activation decreases of the medial prefrontal cortex (MPFC) and of the amygdala (AMY). In the present study, Dynamic Causal Modeling (DCM) was used to explore effective connectivity between those brain regions. To test our hypothesis that the DRN causally down-regulates activity of the MPFC and/or of the AMY, 23 healthy male students solved mental arithmetic tasks of varying difficulty during functional magnetic resonance imaging. A "flow" condition, with task demands automatically balanced with participants' skill level, was compared with conditions of "boredom" and "overload". DCM models were constructed modeling full reciprocal endogenous connections between the DRN, the MPFC, the AMY, and the calcarine. The calcarine was included to allow sensory input to enter the system. Experimental conditions were modeled as exerting modulatory effects on various possible connections between the DRN, the MPFC, and the AMY, but not on self-inhibitory connections, yielding a total of 64 alternative DCM models. Model space was partitioned into eight families based on commonalities in the arrangement of the modulatory effects. Random effects Bayesian Model Selection (BMS) was applied to identify a possible winning family (and model). Although BMS revealed a clear winning family, an outstanding winning model could not be identified. Therefore, Bayesian Model Averaging was performed over models within the winning family to obtain representative DCM parameters for subsequent analyses to test our hypothesis. In line with our expectations, Bayesian averaged parameters revealed stronger down-regulatory influence of the DRN on the MPFC when participants experienced flow relative to control conditions. In addition, these condition-dependent modulatory effects significantly predicted participants' experienced degree of

  17. ON and OFF retinal ganglion cells differentially regulate serotonergic and GABAergic activity in the dorsal raphe nucleus.

    PubMed

    Zhang, Ting; Huang, Lu; Zhang, Li; Tan, Minjie; Pu, Mingliang; Pickard, Gary E; So, Kwok-Fai; Ren, Chaoran

    2016-05-16

    The dorsal raphe nucleus (DRN), the major source of serotonergic input to the forebrain, receives excitatory input from the retina that can modulate serotonin levels and depressive-like behavior. In the Mongolian gerbil, retinal ganglion cells (RGCs) with alpha-like morphological and Y-like physiological properties innervate the DRN with ON DRN-projecting RGCs out numbering OFF DRN-projecting RGCs. The DRN neurons targeted by ON and OFF RGCs are unknown. To explore retino-raphe anatomical organization, retinal afferents labeled with Cholera toxin B were examined for association with the postsynaptic protein PSD-95. Synaptic associations between retinal afferents and DRN serotonergic and GABAergic neurons were observed. To explore retino-raphe functional organization, light-evoked c-fos expression was examined. Light significantly increased the number of DRN serotonergic and GABAergic cells expressing c-Fos. When ON RGCs were rendered silent while enhancing the firing rate of OFF RGCs, c-Fos expression was greatly increased in DRN serotonergic neurons suggesting that OFF DRN-projecting RGCs predominately activate serotonergic neurons whereas ON DRN-projecting RGCs mainly target GABAergic neurons. Direct glutamatergic retinal input to DRN 5-HT neurons contributes to the complex excitatory drive regulating these cells. Light, via the retinoraphe pathway can modify DRN 5-HT neuron activity which may play a role in modulating affective behavior.

  18. Target-specific modulation of the descending prefrontal cortex inputs to the dorsal raphe nucleus by cannabinoids

    PubMed Central

    Geddes, Sean D.; Assadzada, Saleha; Lemelin, David; Sokolovski, Alexandra; Bergeron, Richard; Haj-Dahmane, Samir; Béïque, Jean-Claude

    2016-01-01

    Serotonin (5-HT) neurons located in the raphe nuclei modulate a wide range of behaviors by means of an expansive innervation pattern. In turn, the raphe receives a vast array of synaptic inputs, and a remaining challenge lies in understanding how these individual inputs are organized, processed, and modulated in this nucleus to contribute ultimately to the core coding features of 5-HT neurons. The details of the long-range, top-down control exerted by the medial prefrontal cortex (mPFC) in the dorsal raphe nucleus (DRN) are of particular interest, in part, because of its purported role in stress processing and mood regulation. Here, we found that the mPFC provides a direct monosynaptic, glutamatergic drive to both DRN 5-HT and GABA neurons and that this architecture was conducive to a robust feed-forward inhibition. Remarkably, activation of cannabinoid (CB) receptors differentially modulated the mPFC inputs onto these cell types in the DRN, in effect regulating the synaptic excitatory/inhibitory balance governing the excitability of 5-HT neurons. Thus, the CB system dynamically reconfigures the processing features of the DRN, a mood-related circuit believed to provide a concerted and distributed regulation of the excitability of large ensembles of brain networks. PMID:27114535

  19. ON and OFF retinal ganglion cells differentially regulate serotonergic and GABAergic activity in the dorsal raphe nucleus

    PubMed Central

    Zhang, Ting; Huang, Lu; Zhang, Li; Tan, Minjie; Pu, Mingliang; Pickard, Gary E.; So, Kwok-Fai; Ren, Chaoran

    2016-01-01

    The dorsal raphe nucleus (DRN), the major source of serotonergic input to the forebrain, receives excitatory input from the retina that can modulate serotonin levels and depressive-like behavior. In the Mongolian gerbil, retinal ganglion cells (RGCs) with alpha-like morphological and Y-like physiological properties innervate the DRN with ON DRN-projecting RGCs out numbering OFF DRN-projecting RGCs. The DRN neurons targeted by ON and OFF RGCs are unknown. To explore retino-raphe anatomical organization, retinal afferents labeled with Cholera toxin B were examined for association with the postsynaptic protein PSD-95. Synaptic associations between retinal afferents and DRN serotonergic and GABAergic neurons were observed. To explore retino-raphe functional organization, light-evoked c-fos expression was examined. Light significantly increased the number of DRN serotonergic and GABAergic cells expressing c-Fos. When ON RGCs were rendered silent while enhancing the firing rate of OFF RGCs, c-Fos expression was greatly increased in DRN serotonergic neurons suggesting that OFF DRN-projecting RGCs predominately activate serotonergic neurons whereas ON DRN-projecting RGCs mainly target GABAergic neurons. Direct glutamatergic retinal input to DRN 5-HT neurons contributes to the complex excitatory drive regulating these cells. Light, via the retinoraphe pathway can modify DRN 5-HT neuron activity which may play a role in modulating affective behavior. PMID:27181078

  20. Pharmacological properties of 403U76, a new chemical class of 5-hydroxytryptamine- and noradrenaline-reuptake inhibitor.

    PubMed

    Ferris, R M; Brieaddy, L; Mehta, N; Hollingsworth, E; Rigdon, G; Wang, C; Soroko, F; Wastila, W; Cooper, B

    1995-09-01

    403U76 (5-chloro-[[2-[(dimethylamino)methyl]phenyl]thio]benzene- methanol hydrochloride) is a potent, competitive, inhibitor of 5-hydroxytryptamine (5-HT) and noradenaline reuptake into rat brain synaptosomes. Inhibition of 5-HT uptake in-vivo by 403U76 was demonstrated by potentiation of the behavioural effects of 5-hydroxytryptophan in rats and mice and blockade of p-induced depletion of 5-HT in rats. The firing of 5-HT-ergic dorsal raphe neurons in rats was decreased after intravenous administration of low doses of 403U76 as would be predicted for a 5-HT uptake inhibitor. 403U76 antagonized tetrabenazine-induced sedation, an effect associated with inhibitors of noradrenaline uptake, but not with inhibitors of 5-HT uptake. Thus 403U76 affects noradrenergic as well as 5-HT-ergic neurotransmission in-vivo. Potential anxiolytic activity was indicated by reductions in isolation-induced vocalizations in neonates after 403U76 treatment. Low intravenous doses of 403U76 were well tolerated and had no sustained cardiovascular effects. There were no deleterious behavioural side-effects at active doses. Effects observed on isolated tissues or transmitter receptors occurred only at very high concentrations and were pharmacologically unimportant. Thus 403U76 can be considered a potential antidepressant/anxiolytic agent that is a potent, selective inhibitor of 5-HT and noradrenaline reuptake.

  1. Single-prolonged stress induce changes of CaM/CaMKIIα in the rats of dorsal raphe nucleus.

    PubMed

    Xie, Huaju; Han, Fang; Shi, Xiuyu

    2012-05-01

    Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα) is identified as a Ca2+-dependent kinase in brain involved in the activation of Tryptophan hydroxylase (TPH) acting through direct phosphorylation of TPH, and playing key roles in the signaling pathways initiated by various G protein-coupled 5-HT receptors. The goal of this study is to detect whether there are changes of CaM and CaMKIIα in dorsal raphe nucleus in the rats exposed to single-prolonged stress (SPS), which is a model employed in post-traumatic stress disorder (PTSD) study extensively. A total of 90 male Wistar rats were randomly divided into a normal control group and SPS groups of 7d, 14d. The changes of CaM/CaMKIIα were detected by immunohistochemistry, reverse transcription-polymerase chain reaction and western blot. Our results demonstrate that both expressions of CaM and CaMKIIα significantly increase (P < 0.001) in the SPS 7d group than that in the control group, and then decreased dramatically (P < 0.001) 14 days after SPS. Our results confirm that SPS induce changes of CaM/CaMKIIα in the dorsal raphe nucleus. Changes of CaM/CaMKIIα may be associated with the activation of 5-HT1A receptor, and may contribute to the progress of molecular mechanism of PTSD.

  2. Neurons in monkey dorsal raphe nucleus code beginning and progress of step-by-step schedule, reward expectation, and amount of reward outcome in the reward schedule task.

    PubMed

    Inaba, Kiyonori; Mizuhiki, Takashi; Setogawa, Tsuyoshi; Toda, Koji; Richmond, Barry J; Shidara, Munetaka

    2013-02-20

    The dorsal raphe nucleus is the major source of serotonin in the brain. It is connected to brain regions related to reward processing, and the neurons show activity related to predicted reward outcome. Clinical observations also suggest that it is important in maintaining alertness and its apparent role in addiction seems to be related to reward processing. Here, we examined whether the neurons in dorsal raphe carry signals about reward outcome and task progress during multitrial schedules. We recorded from 98 single neurons in dorsal raphe of two monkeys. The monkeys perform one, two, or three visual discrimination trials (schedule), obtaining one, two, or three drops of liquid. In the valid cue condition, the length and brightness of a visual cue indicated schedule progress and reward amount, respectively. In the random cue condition, the visual cue was randomly presented with respect to schedule length and reward amount. We found information encoded about (1) schedule onset, (2) reward expectation, (3) reward outcome, and (4) reward amount in the mean firing rates. Information theoretic analysis showed that the temporal variation of the neuronal responses contained additional information related to the progress of the schedule toward the reward rather than only discriminating schedule onset or reward/no reward. When considered in light of all that is known about the raphe in anatomy, physiology, and behavior, the rich encoding about both task progress and predicted reward outcome makes the raphe a strong candidate for providing signals throughout the brain to coordinate persistent goal-seeking behavior.

  3. Investigation of a central nucleus of the amygdala/dorsal raphe nucleus serotonergic circuit implicated in fear-potentiated startle

    PubMed Central

    Spannuth, Benjamin M.; Hale, Matthew W.; Evans, Andrew K.; Lukkes, Jodi L.; Campeau, Serge; Lowry, Christopher A.

    2011-01-01

    Serotonergic systems are thought to play an important role in control of motor activity and emotional states. We used a fear-potentiated startle paradigm to investigate the effects of a motor-eliciting stimulus in the presence or absence of induction of an acute fear state on serotonergic neurons in the dorsal raphe nucleus (DR) and cells in subdivisions of the central amygdaloid nucleus (CE), a structure that plays an important role in fear responses, using induction of the protein product of the immediate-early gene, c-fos. In Experiment 1 we investigated the effects of fear conditioning training, by training rats to associate a light cue (conditioned stimulus, CS; 1000 lx, 2 sec) with foot shock (0.5 s, 0.5 mA) in a single session. In Experiment 2 rats were given two training sessions identical to Experiment 1 on days 1 and 2, then tested in one of four conditions on day 3: 1) placement in the training context without exposure to either the CS or acoustic startle (AS), 2) exposure to 10 trials of the 2 s CS, 3) exposure to 40 110 dB AS trials, or 4) exposure to 40 110 dB AS trials with 10 of the trials preceded by and co-terminating with the CS. All treatments were conducted during a 20 min session. Fear conditioning training, by itself, increased c-Fos expression in multiple subdivisions of the CE and throughout the DR. In contrast, fear-potentiated startle selectively increased c-Fos expression in the medial subdivision of the CE and in serotonergic neurons in the dorsal part of the dorsal raphe nucleus (DRD). These data are consistent with previous studies demonstrating that fear-related stimuli selectively activate DRD serotonergic neurons. Further studies of this mesolimbocortical serotonergic system could have important implications for understanding mechanisms underlying vulnerability to stress-related psychiatric disorders, including anxiety and affective disorders. PMID:21277950

  4. Fluvoxamine, a specific 5-hydroxytryptamine uptake inhibitor.

    PubMed

    Claassen, V; Davies, J E; Hertting, G; Placheta, P

    1977-08-01

    1. On the basis of both in vitro and in vivo experiments fluvoxamine has been characterized as a potential anti-depressant drug with almost exclusively 5-hydroxytryptamine (5-HT) uptake inhibiting properties. 2. Fluvoxamine is effective in inhibiting 5-ht uptake by blood platelets and brain synaptosomes. Due to inhibition of the membrane pump the compound prevents 5-HT depletion by the tyramine-derivatives H 75/12 and H 77/77. As a result of the interference with the neuronal re-uptake mechanism for 5-HT, fluvoxamine produces a decreased 5-HT turnover in the brain. Effects of 5-hydroxytryptophan (5-HTP) are potentiated in mice and in combination with pargyline, fluvoxamine induces 5-HT-like behavioural effects. 3. In contrast to tricyclic antidepressants, noradrenaline uptake processes are either unaffected or only slightly inhibited by fluvoxamine. The noradrenaline depleting effects of tyramine derivates are not influenced by fluvoxamine. Reserpine effects, such as ptosis are affected only at very high doses of the test compound. The antagonism by fluvoxamine of the reserpine-induced lowering of the pentamethylenetetrazole convulsive threshold can be regarded as due to an effect upon 5-HT uptake. In contrast to the effects of desmethylimipramine and imipramine, no stimulatory effects are found in rats when rapidly acting reserpine-like compounds are given following a dose of fluvoxamine.

  5. Fluvoxamine, a specific 5-hydroxytryptamine uptake inhibitor.

    PubMed Central

    Claassen, V; Davies, J E; Hertting, G; Placheta, P

    1977-01-01

    1. On the basis of both in vitro and in vivo experiments fluvoxamine has been characterized as a potential anti-depressant drug with almost exclusively 5-hydroxytryptamine (5-HT) uptake inhibiting properties. 2. Fluvoxamine is effective in inhibiting 5-ht uptake by blood platelets and brain synaptosomes. Due to inhibition of the membrane pump the compound prevents 5-HT depletion by the tyramine-derivatives H 75/12 and H 77/77. As a result of the interference with the neuronal re-uptake mechanism for 5-HT, fluvoxamine produces a decreased 5-HT turnover in the brain. Effects of 5-hydroxytryptophan (5-HTP) are potentiated in mice and in combination with pargyline, fluvoxamine induces 5-HT-like behavioural effects. 3. In contrast to tricyclic antidepressants, noradrenaline uptake processes are either unaffected or only slightly inhibited by fluvoxamine. The noradrenaline depleting effects of tyramine derivates are not influenced by fluvoxamine. Reserpine effects, such as ptosis are affected only at very high doses of the test compound. The antagonism by fluvoxamine of the reserpine-induced lowering of the pentamethylenetetrazole convulsive threshold can be regarded as due to an effect upon 5-HT uptake. In contrast to the effects of desmethylimipramine and imipramine, no stimulatory effects are found in rats when rapidly acting reserpine-like compounds are given following a dose of fluvoxamine. PMID:302726

  6. Evidence that PGE2 in the dorsal and median raphe nuclei is involved in LPS-induced anorexia in rats.

    PubMed

    Kopf, Brigitte S; Langhans, Wolfgang; Geary, Nori; Hrupka, Brian; Asarian, Lori

    2011-09-01

    Anorexia is an element of the acute-phase immune response. Its mechanisms remain poorly understood. Activation of inducible cyclooxygenase-2 (COX-2) in blood-brain-barrier endothelial cells and subsequent release of prostaglandins (e.g., prostaglandin E2, PGE2) may be involved. Therefore, we sought to relate the effects of prostaglandins on the anorexia following gram-negative bacterial lipopolysaccharide treatment (LPS) to neural activity in the dorsal and median raphe nuclei (DRN and MnR) in rats. COX-2 antagonist (NS-398, 10mg/kg; IP) administration prior to LPS (100μg/kg; IP) prevented anorexia and reduced c-Fos expression the DRN, MnR, nucleus tractus solitarii and several related forebrain areas. These data indicate that COX-2-mediated prostaglandin synthesis is necessary for LPS anorexia and much of the initial LPS-induced neural activation. Injection of NS-398 into the DRN and MnR (1ng/site) attenuated LPS-induced anorexia to nearly the same extent as IP NS-398, suggesting that prostaglandin signaling in these areas is necessary for LPS anorexia. Because the DRN and MnR are sources of major serotonergic projections to the forebrain, these data suggest that serotonergic neurons originating in the midbrain raphe play an important role in acute-phase response anorexia. Copyright © 2011 Elsevier Inc. All rights reserved.

  7. Organization of Functional Long-Range Circuits Controlling the Activity of Serotonergic Neurons in the Dorsal Raphe Nucleus.

    PubMed

    Zhou, Li; Liu, Ming-Zhe; Li, Qing; Deng, Juan; Mu, Di; Sun, Yan-Gang

    2017-03-21

    Serotonergic neurons play key roles in various biological processes. However, circuit mechanisms underlying tight control of serotonergic neurons remain largely unknown. Here, we systematically investigated the organization of long-range synaptic inputs to serotonergic neurons and GABAergic neurons in the dorsal raphe nucleus (DRN) of mice with a combination of viral tracing, slice electrophysiological, and optogenetic techniques. We found that DRN serotonergic neurons and GABAergic neurons receive largely comparable synaptic inputs from six major upstream brain areas. Upon further analysis of the fine functional circuit structures, we found both bilateral and ipsilateral patterns of topographic connectivity in the DRN for the axons from different inputs. Moreover, the upstream brain areas were found to bidirectionally control the activity of DRN serotonergic neurons by recruiting feedforward inhibition or via a push-pull mechanism. Our study provides a framework for further deciphering the functional roles of long-range circuits controlling the activity of serotonergic neurons in the DRN.

  8. TrkB Signaling in Dorsal Raphe Nucleus is Essential for Antidepressant Efficacy and Normal Aggression Behavior.

    PubMed

    Adachi, Megumi; Autry, Anita E; Mahgoub, Melissa; Suzuki, Kanzo; Monteggia, Lisa M

    2017-03-01

    Brain-derived neurotrophic factor (BDNF) and its high affinity receptor, tropomyosin receptor kinase B (TrkB), have important roles in neural plasticity and are required for antidepressant efficacy. Studies examining the role of BDNF-TrkB signaling in depression and antidepressant efficacy have largely focused on the limbic system, leaving it unclear whether this signaling is important in other brain regions. BDNF and TrkB are both highly expressed in the dorsal raphe nucleus (DRN), a brain region that has been suggested to have a role in depression and antidepressant action, although it is unknown whether BDNF and TrkB in the dorsal raphe nucleus are involved in these processes. We combined the adeno-associated virus (AAV) with the Cre-loxP site-specific recombination system to selectively knock down either Bdnf or TrkB in the DRN. These mice were then characterized in several behavioral paradigms including measures of depression-related behavior and antidepressant efficacy. We show that knockdown of TrkB, but not Bdnf, in the DRN results in loss of antidepressant efficacy and increased aggression-related behavior. We also show that knockdown of TrkB or Bdnf in this brain region does not have an impact on weight, activity levels, anxiety, or depression-related behaviors. These data reveal a critical role for TrkB signaling in the DRN in mediating antidepressant responses and normal aggression behavior. The results also suggest a non-cell autonomous role for BDNF in the DRN in mediating antidepressant efficacy.

  9. Phosphorylation of CaMKII in the rat dorsal raphe nucleus plays an important role in sleep-wake regulation.

    PubMed

    Cui, Su-Ying; Li, Sheng-Jie; Cui, Xiang-Yu; Zhang, Xue-Qiong; Yu, Bin; Sheng, Zhao-Fu; Huang, Yuan-Li; Cao, Qing; Xu, Ya-Ping; Lin, Zhi-Ge; Yang, Guang; Song, Jin-Zhi; Ding, Hui; Wang, Zi-Jun; Zhang, Yong-He

    2016-02-01

    The Ca(2+) modulation in the dorsal raphe nucleus (DRN) plays an important role in sleep-wake regulation. Calmodulin-dependent kinase II (CaMKII) is an important signal-transducing molecule that is activated by Ca(2+) . This study investigated the effects of intracellular Ca(2+) /CaMKII signaling in the DRN on sleep-wake states in rats. Maximum and minimum CaMKII phosphorylation was detected at Zeitgeber time 21 (ZT 21; wakefulness state) and ZT 3 (sleep state), respectively, across the light-dark rhythm in the DRN in rats. Six-hour sleep deprivation significantly reduced CaMKII phosphorylation in the DRN. Microinjection of the CAMKII activation inhibitor KN-93 (5 or 10 nmol) into the DRN suppressed wakefulness and enhanced rapid-eye-movement sleep (REMS) and non-REM sleep (NREMS). Application of a high dose of KN-93 (10 nmol) increased slow-wave sleep (SWS) time, SWS bouts, the mean duration of SWS, the percentage of SWS relative to total sleep, and delta power density during NREMS. Microinjection of CaCl2 (50 nmol) in the DRN increased CaMKII phosphorylation and decreased NREMS, SWS, and REMS. KN-93 abolished the inhibitory effects of CaCl2 on NREMS, SWS, and REMS. These data indicate a novel wake-promoting and sleep-suppressing role for the Ca(2+) /CaMKII signaling pathway in DRN neurons. We propose that the intracellular Ca(2+) /CaMKII signaling in the dorsal raphe nucleus (DRN) plays wake-promoting and sleep-suppressing role in rats. Intra-DRN application of KN-93 (CaMKII activation inhibitor) suppressed wakefulness and enhanced rapid-eye-movement sleep (REMS) and non-REMS (NREMS). Intra-DRN application of CaCl2 attenuated REMS and NREMS. We think these findings should provide a novel cellular and molecular mechanism of sleep-wake regulation. © 2015 International Society for Neurochemistry.

  10. Increased 5-hydroxytryptamine mediates post-inflammatory visceral hypersensitivity via the 5-hydroxytryptamine 3 receptor in rats.

    PubMed

    Choi, Yun-Dong; Sung, Tae-Sik; Kim, Hyun-Ju; La, Jun-Ho; Kim, Tae-Wan; Yang, Il-Suk

    2008-11-01

    Visceral hypersensitivity often develops after intestinal inflammation, but the pathogenic mechanism has not been clearly elucidated. We investigated whether this post-inflammatory visceral hypersensitivity is mediated by 5-hydroxytryptamine through activation of the 5-hydroxytryptamine 3 receptor. In male Sprague-Dawley rats recovered from acetic acid-induced colitis, we monitored visceral nociceptive response by scoring the abdominal withdrawal reflex and simultaneously measuring the changes in arterial pulse rate. Seven days after induction of colitis, 52% of the rats showed an increased abdominal withdrawal reflex score and arterial pulse rate changes to colorectal distension, indicating that they had post-inflammatory visceral hypersensitivity. The 5-hydroxytryptamine 3 receptor antagonists, alosetron (20 mg/kg, p.o.) and granisetron (10 microg/kg, s.c.), inhibited post-inflammatory visceral hypersensitivity. Administration of a 5-hydroxytryptamine precursor, 5-hydroxytryptophan; 10 mg/kg, s.c.), induced visceral hypersensitivity in naïve rats, which was antagonized by granisetron. Increase in 5-hydroxytryptamine immunoreactive cells in colonic mucosal layer was found both in the rats with post-inflammatory visceral hypersensitivity and in the 5-hydroxytryptophan-treated rats. These results suggest that increased 5-hydroxytryptamine in colonic mucosa mediates post-inflammatory visceral hypersensitivity through activation of the 5-hydroxytryptamine 3 receptor.

  11. The hippocampus and dorsal raphe nucleus are key brain areas associated with the antidepressant effects of lithium augmentation of desipramine.

    PubMed

    Cussotto, Sofia; Cryan, John F; O'Leary, Olivia F

    2017-03-27

    Approximately 50% of depressed individuals fail to achieve remission with first-line antidepressant drugs and a third remain treatment-resistant. When first-line antidepressant treatment is unsuccessful, second-line strategies include dose optimisation, switching to another antidepressant, combination with another antidepressant, or augmentation with a non-antidepressant medication. Much of the evidence for the efficacy of augmentation strategies comes from studies using lithium to augment the effects of tricyclic antidepressants. The neural circuitry underlying the therapeutic effects of lithium augmentation is not yet fully understood. Recently, we reported that chronic treatment with a combination of lithium and the antidepressant desipramine, exerted antidepressant-like behavioural effects in a mouse strain (BALB/cOLaHsd) that did not exhibit an antidepressant-like behavioural response to either drug alone. In the present study, we used this model in combination with ΔFosB/FosB immunohistochemistry to identify brain regions chronically affected by lithium augmentation of desipramine when compared to either treatment alone. The data suggest that the dorsal raphe nucleus and the CA3 regions of the dorsal hippocampus are key nodes in the neural circuitry underlying antidepressant action of lithium augmentation of desipramine. These data give new insight into the neurobiology underlying the mechanism of lithium augmentation in the context of treatment-resistant depression.

  12. The role of the dorsal raphe nucleus in the development, expression, and treatment of L-dopa-induced dyskinesia in hemiparkinsonian rats.

    PubMed

    Eskow, Karen L; Dupre, Kristin B; Barnum, Christopher J; Dickinson, Sando O; Park, John Y; Bishop, Christopher

    2009-07-01

    Convergent evidence indicates that in later stages of Parkinson's disease raphestriatal serotonin neurons compensate for the loss of nigrostriatal dopamine neurons by converting and releasing dopamine derived from exogenous administration of the pharmacotherapeutic L-3,4-dihydroxyphenyl-L-alanine (L-dopa). Because the serotonin system is not equipped with dopamine autoregulatory mechanisms, it has been postulated that raphe-mediated striatal dopamine release may fluctuate dramatically. These fluctuations may portend the development of abnormal involuntary movements called L-dopa-induced dyskinesia (LID). As such, it has been hypothesized that reducing the activity of raphestriatal neurons could dampen supraphysiological stimulation of striatal dopamine receptors thereby alleviating LID. To directly address this, the current study employed the rodent model of LID to investigate the contribution of the rostral raphe nuclei (RRN) in the development, expression and treatment of LID. In the first study, dual serotonin/dopamine selective lesions of the RRN and medial forebrain bundle, respectively, verified that the RRN are essential for the development of LID. In a direct investigation into the neuroanatomical specificity of these effects, microinfusions of +/-8-OH-DPAT into the intact dorsal raphe nucleus dose-dependently attenuated the expression of LID without affecting the antiparkinsonian efficacy of L-dopa. These current findings reveal the integral contribution of the RRN in the development and expression of LID and implicate a prominent role for dorsal raphe 5-HT1AR in the efficacious properties of 5-HT1AR agonists.

  13. Characterization of U-92016A as a selective, orally active, high intrinsic activity 5-hydroxytryptamine1A agonist.

    PubMed

    McCall, R B; Romero, A G; Bienkowski, M J; Harris, D W; McGuire, J C; Piercey, M F; Shuck, M E; Smith, M W; Svensson, K A; Schreur, P J

    1994-11-01

    The purpose of the present study was to characterize U-92016A [(+)-R)-2-cyano-N,N-dipropyl-8-amino-6,7,8,9-tetrahydro-3H-benz[e] indole] as a 5-hydroxytryptamine (5-HT)1A receptor agonist and to compare its activity with that of standard 5-HT1A receptor agonists. U-92016A binds with high affinity to human 5-HT1A receptors expressed in Chinese hamster ovary cells (Ki = 0.2 nM). Radioligand binding studies also indicate that U-92016A is selective for the 5-HT1A receptor over other biogenic amine receptors. In Chinese hamster ovary cells expressing the human 5HT1A receptor, U-92016A decreased the forskolin-induced increase in cyclic AMP synthesis and had an intrinsic activity of 0.82 relative to 5-HT. U-92016A potently decreased rectal temperature in mice. The maximum temperature decrease was significantly greater than that observed for 8-hydroxy-di-n-propyl aminotetralin, buspirone, gepirone, ipsapirone or flesinoxan. U-92016A also elicited the 5-HT-mediated syndrome in rats and resulted in a dose-related decrease in 5-hydroxytryptophan accumulation. The compound also decreased arterial blood pressure in spontaneously hypertensive rats and inhibited sympathetic nerve activity in cats. In these assays U-92016A displayed excellent potency and a long duration of action. U-92016A also inhibited the firing of dorsal raphe 5-HT neurons and was active in two social interaction assays. The p.o. bioavailability of U-92016A was calculated to be 45%. Taken together, these data indicate that U-92016A is a metabolically stable, p.o. active 5-HT1A receptor agonist with an exceptionally high degree of intrinsic activity.

  14. Estradiol Valerate and Remifemin ameliorate ovariectomy-induced decrease in a serotonin dorsal raphe-preoptic hypothalamus pathway in rats.

    PubMed

    Wang, Wenjuan; Cui, Guangxia; Jin, Biao; Wang, Ke; Chen, Xing; Sun, Yu; Qin, Lihua; Bai, Wenpei

    2016-11-01

    Perimenopausal syndromes begin as ovarian function ceases and the most common symptoms are hot flushes. Data indicate that the projections of serotonin to hypothalamus may be involved in the mechanism of hot flushes. Therefore, the aim of this study is to investigate the potential role of the serotonin dorsal raphe-preoptic hypothalamus pathway for hot flushes in an animal model of menopause. We determined the changes in serotonin expression in the dorsal raphe (DR) and preoptic anterior hypothalamus (POAH) in ovariectomized rats. We also explored the therapeutical effects of estradiol valerate and Remifemin in this model. Eighty female Sprague-Dawley rats were randomly assigned to sham-operated (SHAM) group, ovariectomy (OVX) group with vehicle, ovariectomy with estradiol valerate treatment (OVX+E) group and ovariectomy with Remifemin (OVX+ICR) group. Serotonin expression was evaluated in the DR and POAH using immunofluorescence and quantified in the DR using an enzyme-linked immunosorbent assay (ELISA). Apoptosis was analyzed in the DR by TUNEL assay. The number of serotonin immunoreactive neurons and the level of serotonin expression in the DR decreased significantly following OVX compared to the SHAM group. No TUNEL-positive cells were detected in the DR in any group. In addition, following OVX, the number of serotonin-positive fibers decreased significantly in the ventromedial preoptic nucleus (VMPO), especially in the ventrolateral preoptic nucleus (VLPO). Treatment with either estradiol or Remifemin for 4 weeks countered the OVX-induced decreases in serotonin levels in both the DR and the hypothalamus, with levels in the treated rats similar to those in the SHAM group. A fluorescently labeled retrograde tracer was injected into the VLPO at the 4-week time point. A significantly lower percentage of serotonin with CTB double-labeled neurons in CTB-labeled neurons was demonstrated after ovariectomy, and both estradiol and Remifemin countered this OVX

  15. Electrophysiological Assessment of Serotonin and GABA Neuron Function in the Dorsal Raphe during the Third Trimester Equivalent Developmental Period in Mice123

    PubMed Central

    Morton, Russell A.; Yanagawa, Yuchio

    2015-01-01

    Abstract Alterations in the development of the serotonin system can have prolonged effects, including depression and anxiety disorders later in life. Serotonin axonal projections from the dorsal raphe undergo extensive refinement during the first 2 weeks of postnatal life in rodents (equivalent to the third trimester of human pregnancy). However, little is known about the functional properties of serotonin and GABA neurons in the dorsal raphe during this critical developmental period. We assessed the functional properties and synaptic connectivity of putative serotoninergic neurons and GABAergic neurons in the dorsal raphe during early [postnatal day (P) P5–P7] and late (P15–P17) stages of the third trimester equivalent period using electrophysiology. Our studies demonstrate that GABAergic neurons are hyperexcitable at P5–P7 relative to P15–P17. Furthermore, putative serotonin neurons exhibit an increase in both excitatory and GABAA receptor-mediated spontaneous postsynaptic currents during this developmental period. Our data suggest that GABAergic neurons and putative serotonin neurons undergo significant electrophysiological changes during neonatal development. PMID:26730407

  16. Inter- and intracellular relationship of substance P-containing neurons with serotonin and GABA in the dorsal raphe nucleus: combination of autoradiographic and immunocytochemical techniques

    SciTech Connect

    Magoul, R.; Onteniente, B.; Oblin, A.; Calas, A.

    1986-06-01

    Double-labeling experiments were performed at the electron microscopic level in the dorsal raphe nucleus of rat, in order to study the inter- and intracellular relationship of substance P with gamma-aminobutyric acid (GABA) and serotonin. Autoradiography for either (/sup 3/H)serotonin or (/sup 3/H)GABA was coupled, on the same tissue section, with peroxidase-antiperoxidase immunocytochemistry for substance P in colchicine-treated animals. Intercellular relationships were represented by synaptic contacts made by (/sup 3/H)serotonin-labeled terminals on substance P-containing somata and dendrites, and by substance P-containing terminals on (/sup 3/H)GABA-labeled cells. Intracellular relationships were suggested by the occurrence of the peptide within (/sup 3/H)serotonin-containing and (/sup 3/H)GABA-containing cell bodies and fibers. Doubly labeled varicosities of the two kinds were also observed in the supraependymal plexus adjacent to the dorsal raphe nucleus. The results demonstrated that, in addition to reciprocal synaptic interactions made by substance P with serotonin and GABA, the dorsal raphe nucleus is the site of intracellular relationships between the peptide and either the amine or the amino acid.

  17. Lack of response of serotonergic neurons in the dorsal raphe nucleus of freely moving cats to stressful stimuli.

    PubMed

    Wilkinson, L O; Jacobs, B L

    1988-09-01

    Changes in brain serotonin (5-HT) neurotransmission have been implicated in the mammalian response to stressful stimuli. The purpose of this study was to examine the extracellular single-unit activity of 5-HT neurons in cats exposed to three stressors: loud (100 dB) white noise, restraint, and confrontation with a dog. Serotonergic neurons were recorded in the dorsal raphe nucleus (DRN) and were identified by (i) slow and regular spontaneous activity, (ii) long duration (approximately 2 ms) waveform, (iii) complete suppression of activity during REM sleep and after systemic administration of 5-methoxy-N-N-dimethyltryptamine (250 micrograms/kg i.m.), and (iv) histological localization in the DRN. Despite behavioral and physiological evidence that all three manipulations induced a stress response, the maximal firing rate of 5-HT neurons was not significantly different from that observed under unstressed conditions. These data are consistent with previous studies from our laboratory which have indicated that very few manipulations are able to perturb the slow and regular activity of these neurons. In contrast, previous work has shown that the firing rate of noradrenergic neurons in the locus ceruleus is dramatically increased by these stressors. The relative imbalance in the activity of these two neuronal groups observed during stress may affect postsynaptic neuronal processing patterns and have adaptive significance during stressful conditions.

  18. Ribosomal DNA transcription in the dorsal raphe nucleus is increased in residual but not in paranoid schizophrenia.

    PubMed

    Krzyżanowska, Marta; Steiner, Johann; Brisch, Ralf; Mawrin, Christian; Busse, Stefan; Braun, Katharina; Jankowski, Zbigniew; Bernstein, Hans-Gert; Bogerts, Bernhard; Gos, Tomasz

    2015-03-01

    The central serotonergic system is implicated in the pathogenesis of schizophrenia, where the imbalance between dopamine, serotonin and glutamate plays a key pathophysiological role. The dorsal raphe nucleus (DRN) is the main source of serotonergic innervation of forebrain limbic structures disturbed in schizophrenia patients. The study was carried out on paraffin-embedded brains from 17 (8 paranoid and 9 residual) schizophrenia patients and 28 matched controls without mental disorders. The transcriptional activity of ribosomal DNA (rDNA) in DRN neurons was evaluated by the AgNOR silver-staining method. An increased rDNA transcriptional activity was found in schizophrenia patients in the cumulative analysis of all DRN subnuclei (t test, P = 0.02). Further subgroup analysis revealed that it was an effect specific for residual schizophrenia versus paranoid schizophrenia or control groups (ANOVA, P = 0.002). This effect was confounded neither by suicide nor by antipsychotic medication. Our findings suggest that increased activity of rDNA in DRN neurons is a distinct phenomenon in schizophrenia, particularly in residual patients. An activation of the rDNA transcription in DRN neurons may represent a compensatory mechanism to overcome the previously described prefrontal serotonergic hypofunction in this diagnostic subgroup.

  19. Dorsal raphe nucleus and locus coeruleus neural networks and the elaboration of the sweet-substance-induced antinociception.

    PubMed

    Kishi, Renato; Bongiovanni, Renata; de Nadai, Tales Rubens; Freitas, Renato Leonardo; de Oliveira, Ricardo; Ferreira, Célio Marcos Dos Reis; Coimbra, Norberto Cysne

    2006-02-27

    In order to investigate the effects of monoaminergic neurons of the dorsal raphe nucleus (DRN) and locus coeruleus (LC) on the elaboration and control of sweet-substance-induced antinociception, male albino Wistar rats weighing 180-200 g received sucrose solution (250 g/L) for 7-14 days as their only source of liquid. After the chronic consumption of sucrose solution, each animal was pretreated with unilateral microinjection of ibotenic acid (1.0 microg/0.2 microL) in the DRN or in the LC. The tail withdrawal latencies of the rats in the tail-flick test were measured immediately before and 7 days after this treatment. The neurochemical lesion of locus coeruleus, but not of DRN neural networks with ibotenic acid, after the chronic intake of sweetened solution, decreased the sweet-substance-induced antinociception. These results indicate the involvement of noradrenaline-containing neurons of the LC in the sucrose-induced antinociception. We also consider the possibility of DRN serotonergic neurons exerting some inhibitory effect on the LC neural networks involved with the elaboration of the sweet-substance-induced antinociception.

  20. Y-Like Retinal Ganglion Cells Innervate the Dorsal Raphe Nucleus in the Mongolian Gerbil (Meriones unguiculatus)

    PubMed Central

    Lau, Benson Wui-Man; Yang, Jian; Pickard, Gary E.; So, Kwok-Fai; Pu, Mingliang

    2011-01-01

    Background The dorsal raphe nucleus (DRN) of the mesencephalon is a complex multi-functional and multi-transmitter nucleus involved in a wide range of behavioral and physiological processes. The DRN receives a direct input from the retina. However little is known regarding the type of retinal ganglion cell (RGC) that innervates the DRN. We examined morphological characteristics and physiological properties of these DRN projecting ganglion cells. Methodology/Principal Findings The Mongolian gerbils are highly visual rodents with a diurnal/crepuscular activity rhythm. It has been widely used as experimental animals of various studies including seasonal affective disorders and depression. Young adult gerbils were used in the present study. DRN-projecting RGCs were identified following retrograde tracer injection into the DRN, characterized physiologically by extracellular recording and morphologically after intracellular filling. The result shows that DRN-projecting RGCs exhibit morphological characteristics typical of alpha RGCs and physiological response properties of Y-cells. Melanopsin was not detected in these RGCs and they show no evidence of intrinsic photosensitivity. Conclusions/Significance These findings suggest that RGCs with alpha-like morphology and Y-like physiology appear to perform a non-imaging forming function and thus may participate in the modulation of DRN activity which includes regulation of sleep and mood. PMID:21552551

  1. Selective activation of dorsal raphe nucleus-projecting neurons in the ventral medial prefrontal cortex by controllable stress

    PubMed Central

    Baratta, Michael V.; Zarza, Christina M.; Gomez, Devan M.; Campeau, Serge; Watkins, Linda R.; Maier, Steven F.

    2009-01-01

    Exposure to uncontrollable stressors produces a variety of behavioral consequences (e.g. exaggerated fear, reduced social exploration) that do not occur if the stressor is controllable. In addition, an initial experience with a controllable stressor can block the behavioral and neural responses to a later uncontrollable stressor. The serotonergic (5-HT) dorsal raphe nucleus (DRN) has come to be viewed as a critical structure in mediating the behavioral effects of uncontrollable stress. Recent work suggests that the buffering effects of behavioral control on the DRN-dependent behavioral outcomes of uncontrollable stress require ventral medial prefrontal cortex (mPFCv) activation at the time of behavioral control. The present studies were conducted to directly determine whether or not controllable stress selectively activates DRN-projecting neurons within the mPFCv. To examine this possibility in the rat, we combined retrograde tracing (fluorogold iontophoresed into the DRN) with Fos immunohistochemistry, a marker for neural activation. Exposure to controllable, relative to uncontrollable, stress increased Fos expression in fluorogold-labeled neurons in the prelimbic region (PL) of the mPFCv. Furthermore, in a separate experiment, a prior experience with controllable stress led to potentiation of Fos expression in retrogradely labeled PL neurons in response to an uncontrollable stressor one week later. These results suggest that the PL selectively responds to behavioral control and utilizes such information to regulate the brainstem response to ongoing and subsequent stressors. PMID:19686468

  2. Ca(2+) in the dorsal raphe nucleus promotes wakefulness via endogenous sleep-wake regulating pathway in the rats.

    PubMed

    Cui, Su-Ying; Li, Sheng-Jie; Cui, Xiang-Yu; Zhang, Xue-Qiong; Yu, Bin; Huang, Yuan-Li; Cao, Qing; Xu, Ya-Ping; Yang, Guang; Ding, Hui; Song, Jin-Zhi; Ye, Hui; Sheng, Zhao-Fu; Wang, Zi-Jun; Zhang, Yong-He

    2016-07-26

    Serotonergic neurons in the dorsal raphe nucleus (DRN) are involved in the control of sleep-wake states. Our previous studies have indicated that calcium (Ca(2+)) modulation in the DRN plays an important role in rapid-eye-movement sleep (REMS) and non-REMS (NREMS) regulation during pentobarbital hypnosis. The present study investigated the effects of Ca(2+) in the DRN on sleep-wake regulation and the related neuronal mechanism in freely moving rats. Our results showed that microinjection of CaCl2 (25 or 50 nmol) in the DRN promoted wakefulness and suppressed NREMS including slow wave sleep and REMS in freely moving rats. Application of CaCl2 (25 or 50 nmol) in the DRN significantly increased serotonin in the DRN and hypothalamus, and noradrenaline in the locus coeruleus and hypothalamus. Immunohistochemistry study indicated that application of CaCl2 (25 or 50 nmol) in the DRN significantly increased c-Fos expression ratio in wake-promoting neurons including serotonergic neurons in the DRN, noradrenergic neurons in the locus coeruleus, and orxinergic neurons in the perifornical nucleus, but decreased c-Fos expression ratio of GABAergic sleep-promoting neurons in the ventrolateral preoptic nucleus. These results suggest that Ca(2+) in the DRN exert arousal effects via up-regulating serotonergic functions in the endogenous sleep-wake regulating pathways.

  3. Chronic alcoholics without Wernicke-Korsakoff syndrome or cirrhosis do not lose serotonergic neurons in the dorsal raphe nucleus.

    PubMed

    Baker, K G; Halliday, G M; Kril, J J; Harper, C G

    1996-02-01

    Despite the considerable evidence that alcoholics have perturbation of serotonergic function, there is little pathological evidence for alcohol directly affecting the nervous system. The present study aims to assess neuronal loss that occurs as a consequence of alcohol neurotoxicity in the serotonergic dorsal raphe nucleus (DRN). To that end, the brains of eight alcoholics and eight age-matched control cases were carefully screened to eliminate serious liver disease, the sequela of thiamine deficiency, Wernicke-Korsakoff syndrome (WKS), and other pathological abnormalities. Brains were formalin-fixed for 2 weeks, cut, and then immunohistochemically stained using a monoclonal PH8 antibody specific for the rate-limiting enzyme of serotonin synthesis, tryptophan hydroxylase. The morphology of the serotonin-synthesizing neurons and their average size was similar in all cases. However, there was a reduction in the staining intensity of the reaction product in the DRN serotonergic neurons of most alcoholics. Neuronal counts on spaced serial sections revealed that there were an estimated average total of 106,100 +/- 19,500 serotonergic neurons in the DRN of alcoholics and 108,300 +/- 11,800 in the DRN of controls, indicating that in most alcoholics there is no reduction in the number of these neurons. Therefore, the effect of chronic alcohol consumption on the serotonergic system, in the absence of WKS or liver disease, seems to be functional rather than neuropathological.

  4. Reciprocal connections between CART-immunoreactive, hypothalamic paraventricular neurons and serotonergic dorsal raphe cells in the rat: Light microscopic study.

    PubMed

    Lee, Ji S; Lee, Hyun S

    2014-04-29

    Based on the overlapping physiological roles of cocaine- and amphetamine-regulated transcript (CART) peptides and serotonin, the present study examined the anatomical connection between the hypothalamic paraventricular nucleus (PVN) and the dorsal raphe (DR). The first series of experiments were performed to investigate descending projections from the CART-immunoreactive (CART-ir) PVN to serotonergic DR cells. CART-ir varicosities made contact with serotonergic DR neurons. An anterograde tracing study revealed that varicosities originating from the PVN formed close appositions to serotonergic neuronal profiles along the entire rostro-caudal extent of the DR. A retrograde study demonstrated that CART neurons projecting to the DR were mainly localized in the caudal parvicellular PVN, comprising approximately 3.0%±0.4% (n=8) of total CART cells. A second series of experiments was performed to investigate ascending projections from the DR to CART-ir PVN cells. Serotonin transporter-ir boutons made contact with CART-ir PVN neurons. Anterograde tracing revealed that varicosities originating from the DR formed close appositions to CART-ir PVN cells. Retrograde examination demonstrated that serotonergic neurons projecting to the parvicellular PVN were located along the entire rostro-caudal extent of the DR. The present observation provided an anatomical basis for accumulating evidence in the literature that suggests a functional interaction between the CART and serotonin systems during the regulation of energy balance, emotional behavior, and arousal. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. The role of lateral habenula-dorsal raphe nucleus circuits in higher brain functions and psychiatric illness.

    PubMed

    Zhao, Hua; Zhang, Bei-Lin; Yang, Shao-Jun; Rusak, Benjamin

    2015-01-15

    Serotonergic neurons in the dorsal raphe nucleus (DRN) play an important role in regulation of many physiological functions. The lateral nucleus of the habenular complex (LHb) is closely connected to the DRN both morphologically and functionally. The LHb is a key regulator of the activity of DRN serotonergic neurons, and it also receives reciprocal input from the DRN. The LHb is also a major way-station that receives limbic system input via the stria medullaris and provides output to the DRN and thereby indirectly connects a number of other brain regions to the DRN. The complex interactions of the LHb and DRN contribute to the regulation of numerous important behavioral and physiological mechanisms, including those regulating cognition, reward, pain sensitivity and patterns of sleep and waking. Disruption of these functions is characteristic of major psychiatric illnesses, so there has been a great deal of interest in how disturbed LHb-DRN interactions may contribute to the symptoms of these illnesses. This review summarizes recent research related to the roles of the LHb-DRN system in regulation of higher brain functions and the possible role of disturbed LHb-DRN function in the pathogenesis of psychiatric disorders, especially depression.

  6. Dorsal raphe nucleus acetylcholine-mediated neurotransmission modulates post-ictal antinociception: The role of muscarinic and nicotinic cholinergic receptors.

    PubMed

    de Oliveira, Rithiele Cristina; de Oliveira, Ricardo; Biagioni, Audrey Francisco; Falconi-Sobrinho, Luiz Luciano; Coimbra, Norberto Cysne

    2016-01-15

    The dorsal raphe nucleus (DRN) is a key structure of the endogenous pain inhibitory system. Although the DRN is rich in serotoninergic neurons, cholinergic neurons are also found in that nucleus. Both ictal and inter-ictal states are followed by post-ictal analgesia. The present study investigated the role of cholinergic mechanisms in postictal antinociceptive processes using microinjections of atropine and mecamylamine, muscarinic and nicotinic cholinergic receptor antagonists, respectively, in the DRN of rats. Intraperitoneal injection of pentylenetetrazole (PTZ) (at 64mg/kg) caused tonic and tonic-clonic seizures. The convulsive motor reactions were followed by an increase in pain thresholds, a phenomenon known as post-ictal analgesia. Pre-treatment of the DRN with atropine or mecamylamine at 1µg, 3µg and 5µg/0.2µL decreased the post-ictal antinociceptive phenomenon. The present results showed that the post-ictal analgesia was mediated by muscarinic and nicotinic cholinergic receptors in the DRN, a structure crucially involved in the neural network that organises post-ictal hypoalgesia.

  7. Urocortin 2 increases c-Fos expression in topographically organized subpopulations of serotonergic neurons in the rat dorsal raphe nucleus.

    PubMed

    Staub, Daniel R; Spiga, Francesca; Lowry, Christopher A

    2005-05-24

    Corticotropin-releasing factor (CRF)-related peptides modulate stress-related physiology and behavior. Some of the physiological and behavioral effects of CRF-related peptides may be due to actions on CRF type 2 (CRF2) receptors modulating serotonergic systems in the dorsal raphe nucleus (DR). To determine if CRF2 receptor activation has effects on serotonergic neurons in the DR in conscious behaving rats, we gave intracerebroventricular (icv) injections of the selective CRF2 receptor agonist urocortin 2 (0, 0.01, 0.1, or 1.0 mug in 2 microl saline) to adult male Wistar rats and quantified c-Fos expression in topographically organized subpopulations of serotonergic neurons within the DR. In addition, home cage behaviors were recorded for 30 min prior to drug treatment and for 2 h following drug treatment. Two hours following drug treatment, rats were anesthetized, transcardially perfused with fixative, and brain tissues were processed for immunohistochemistry. Urocortin 2, in the absence of any effects on most behavioral endpoints studied, consistently increased c-Fos expression in subpopulations of serotonergic neurons identified by either tryptophan hydroxylase or serotonin immunostaining within specific subdivisions of the DR, particularly the dorsal region of the mid-rostrocaudal and caudal DR (-7.64, -8.18, -8.54, and -9.16 mm bregma). These studies demonstrate that urocortin 2 has selective actions on a subset of DR serotonergic neurons. Urocortin 2 actions on serotonergic systems described here may contribute to delayed behavioral effects of urocortin 2 described previously, including orexigenic, locomotor, and anxiety-related effects in a variety of behavioral tests as well as potentiation of conditioned fear and induction of escape deficits in a model of learned helplessness.

  8. Galanin subtype 1 and subtype 2 receptors mediate opposite anxiety-like effects in the rat dorsal raphe nucleus.

    PubMed

    Morais, J S; Souza, M M; Campanha, T M N; Muller, C J T; Bittencourt, A S; Bortoli, V C; Schenberg, L C; Beijamini, V

    2016-11-01

    About 40% of the dorsal raphe nucleus (DRN) neurons co-express serotonin (5-HT) and galanin. Serotonergic pathways from the DRN to the amygdala facilitate learned anxiety, while those from the DRN to the dorsal periaqueductal grey matter (DPAG) impair innate anxiety. Previously, we showed that galanin infusion in the DRN of rats induces anxiolytic effect by impairing inhibitory avoidance without changing escape behaviour in the elevated T-maze (ETM). Here, we evaluated: (1) which galanin receptors would be involved in the anxiolytic effect of galanin in the DRN of rats tested in the ETM; (2) the effects of galanin intra-DRN on panic-like behaviours evoked by electrical stimulation of the DPAG. The activation of DRN GAL1 receptors by M617 (1.0 and 3.0nmol) facilitated inhibitory avoidance, whereas the activation of GAL2 receptors by AR-M1896 (3.0nmol) impaired the inhibitory avoidance in the ETM, suggesting an anxiogenic and an anxiolytic-like effect respectively. Both agonists did not change escape behaviour in the ETM or locomotor activity in the open field. The anxiolytic effect of AR-M1896 was attenuated by the prior administration of WAY100635 (0.18nmol), a 5-HT1A antagonist. Galanin (0.3nmol) administered in the DRN increased discreetly flight behaviours induced by electrical stimulation of the DPAG, suggesting a panicolytic effect. Together, our results showed that galanin mediates opposite anxiety responses in the DRN by activation of GAL1 and GAL2 receptors. The anxiolytic effect induced by activation of Gal2 receptors may depend on serotonergic tone. Finally, the role of galanin in panic related behaviours remains uncertain. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Unpredictable chronic mild stress exerts anxiogenic-like effects and activates neurons in the dorsal and caudal region and in the lateral wings of the dorsal raphe nucleus.

    PubMed

    Lopes, Danielle A; Lemes, Jéssica A; Melo-Thomas, Liana; Schor, Herbert; de Andrade, José S; Machado, Carla M; Horta-Júnior, José A C; Céspedes, Isabel C; Viana, Milena B

    2016-01-15

    In previous studies, we verified that exposure to unpredictable chronic mild stress (UCMS) facilitates avoidance responses in the elevated T-maze (ETM) and increased Fos-immunoreactivity in different brain structures involved in the regulation of anxiety, including the dorsal raphe (DR). Since, it has been shown that the DR is composed of distinct subpopulations of serotonergic and non-serotonergic neurons, the present study investigated the pattern of activation of these different subnuclei of the region in response to this stress protocol. Male Wistar rats were either unstressed or exposed to the UCMS procedure for two weeks and, subsequently, analyzed for Fos-immunoreactivity (Fos-ir) in serotonergic cells of the DR. To verify if the anxiogenic effects observed in the ETM could be generalized to other anxiety models, a group of animals was also tested in the light/dark transition test after UCMS exposure. Results showed that the UCMS procedure decreased the number of transitions and increased the number of stretched attend postures in the model, an anxiogenic effect. UCMS exposure also increased Fos-ir and the number of double-labeled neurons in the mid-rostral subdivision of the dorsal part of the DR and in the mid-caudal region of the lateral wings. In the caudal region of the DR there was a significant increase in the number of Fos-ir. No significant effects were found in the other DR subnuclei. These results corroborate the idea that neurons of specific subnuclei of the DR regulate anxiety responses and are differently activated by chronic stress exposure. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Epigenetic regulation of dorsal raphe GABA(B1a) associated with isolation-induced abnormal responses to social stimulation in mice.

    PubMed

    Araki, Ryota; Hiraki, Yosuke; Nishida, Shoji; Kuramoto, Nobuyuki; Matsumoto, Kinzo; Yabe, Takeshi

    2016-02-01

    In isolation-reared mice, social encounter stimulation induces locomotor hyperactivity and activation of the dorsal raphe nucleus (DRN), suggesting that dysregulation of dorsal raphe function may be involved in abnormal behaviors. In this study, we examined the involvement of dorsal raphe GABAergic dysregulation in the abnormal behaviors of isolation-reared mice. We also studied an epigenetic mechanism underlying abnormalities of the dorsal raphe GABAergic system. Both mRNA and protein levels of GABA(B1a), a GABA(B) receptor subunit, were increased in the DRN of isolation-reared mice, compared with these levels in group-reared mice. In contrast, mRNA levels for other GABAergic system-related genes (GABA(A) receptor α1, β2 and γ2 subunits, GABA(B) receptor 1b and 2 subunits, and glutamate decarboxylase 67 and 65) were unchanged. Intra-DRN microinjection of 0.06 nmol baclofen (a GABA(B) receptor agonist) exacerbated encounter-induced hyperactivity and aggressive behavior, while microinjection of 0.3 nmol phaclofen (a GABA(B) receptor antagonist) attenuated encounter-induced hyperactivity and aggressive behavior in isolation-reared mice. Furthermore, microinjection of 0.06 nmol baclofen elicited encounter-induced hyperactivity in group-reared mice. Neither baclofen nor phaclofen affected immobility time in the forced swim test and hyperactivity in a novel environment of isolation reared mice. Bisulfite sequence analyses revealed that the DNA methylation level of the CpG island around the transcription start site (TSS) of GABA(B1a) was decreased in the DRN of isolation-reared mice. Chromatin immunoprecipitation analysis showed that histone H3 was hyperacetylated around the TSS of GABA(B1a) in the DRN of isolation-reared mice. These findings indicate that an increase in dorsal raphe GABA(B1a) expression via epigenetic regulation is associated with abnormal responses to social stimulation such as encounter-induced hyperactivity and aggressive behavior in isolation

  11. Swim stress activates serotonergic and non-serotonergic neurons in specific subdivisions of the rat dorsal raphe nucleus in a temperature-dependent manner

    PubMed Central

    Kelly, Kyle J.; Donner, Nina C.; Hale, Matthew W.; Lowry, Christopher A.

    2011-01-01

    Physical (exteroceptive) stimuli and emotional (interoceptive) stimuli are thought to influence stress-related physiologic and behavioral responses through different neural mechanisms. Previous studies have demonstrated that stress-induced activation of brainstem serotonergic systems is influenced by environmental factors such as temperature. In order to further investigate the effects of environmental influences on stress-induced activation of serotonergic systems, we exposed adult male Wistar rats to either home cage control conditions or a 15 min swim in water maintained at 19 °C, 25 °C, or 35 °C and conducted dual immunohistochemical staining for c-Fos, a marker of immediate-early nuclear activation, and tryptophan hydroxylase (TPH), a marker of serotonergic neurons. Changes in core body temperature were documented using biotelemetry. As expected, exposure to cold (19 °C) swim, relative to warm (35 °C) swim, increased c-Fos expression in the external lateral part of the parabrachial nucleus (LPBel), an important part of the spinoparabrachial pathway involved in sensation of cold, cutaneous stimuli, and in serotonergic neurons in the raphe pallidus nucleus (RPa), an important part of the efferent mechanisms controlling thermoregulatory warming responses. In addition, exposure to cold (19 °C) swim, relative to 35 °C swim, increased c-Fos expression in the dorsal raphe nucleus, ventrolateral part/periaqueductal gray (DRVL/VLPAG) and dorsal raphe nucleus, interfascicular part (DRI). Both of these subregions of the dorsal raphe nucleus (DR) have previously been implicated in thermoregulatory responses. Altogether, the data are consistent with the hypothesis that midbrain serotonergic neurons, possibly via activation of afferents to the DR by thermosensitive spinoparabrachial pathways, play a role in integration of physiologic and behavioral responses to interoceptive stress-related cues involved in forced swimming and exteroceptive cues related to cold

  12. Alcoholics have more Tryptophan Hydroxylase 2 mRNA and Protein in the Dorsal and Median Raphe Nuclei

    PubMed Central

    Bach, Helene; Arango, Victoria; Kassir, Suham A.; Tsaava, Tea; Dwork, Andrew J.; Mann, J. John; Underwood, Mark D.

    2014-01-01

    Background Chronic alcohol use depletes brain serotonin (5-HT), yet we previously found more tryptophan hydroxylase 2 (TPH2), the rate-limiting biosynthetic enzyme for 5-HT, in the dorsal raphe nucleus (DRN) of alcoholics. We sought to determine whether the increase in amount of TPH2 enzyme is associated with more TPH2 mRNA gene expression in the DRN of a new cohort of alcoholics and controls. Methods TPH2 mRNA and protein were measured by in situ hybridization and immunoautoradiography, respectively, in the DRN and median raphe nucleus (MRN) of ageand sex- matched pairs (n=16) of alcoholics and non-psychiatric controls. Alcohol use disorder (AUD) diagnosis and medical, psychiatric and family histories were obtained by psychological autopsy. Age and sex were covariates in the analyses. Results TPH2 mRNA in alcoholics was greater in the DRN and MRN compared to controls (DRN: Controls: 3.6±1.6, Alcoholics: 4.8±1.8 nCi/mg of tissue, F= 4.106, p=0.02; MRN: Controls: 2.6±1.2, Alcoholics: 3.5±1.1 nCi/mg of tissue, F=3.96, p=0.024). The difference in TPH2 mRNA was present in all DRN subnuclei (DRd: 135%, DRif: 139%, DRv: 135%, DRvl: 136% percent of control p<0.05) except the caudal subnucleus. Alcoholics also had more TPH2 protein in the DRN and MRN than controls (DRN: Controls: 265±47, Alcoholics: 318±47 μCi/g, F=8.72, p=0.001; MRN: Controls: 253±33, Alcoholics: 345±39 μCi/g, F=7.78, p=0.001). There is a positive correlation between TPH2 protein and mRNA expression in the DRN (r=0.815, p<0.001), suggesting that the higher amount of TPH2 protein is due to an increase in TPH2 gene expression. Conclusions These findings suggest that greater TPH2 gene expression is the basis for more TPH2 protein in the DRN and MRN in alcoholics. PMID:24942188

  13. Repeated social defeat increases reactive emotional coping behavior and alters functional responses in serotonergic neurons in the rat dorsal raphe nucleus

    PubMed Central

    Paul, Evan D.; Hale, Matthew W.; Lukkes, Jodi L.; Valentine, McKenzie J.; Sarchet, Derek M.; Lowry, Christopher A.

    2011-01-01

    Chronic stress is a vulnerability factor for a number of psychiatric disorders, including anxiety and affective disorders. Social defeat in rats has proven to be a useful paradigm to investigate the neural mechanisms underlying physiologic and behavioral adaptation to acute and chronic stress. Previous studies suggest that serotonergic systems may contribute to the physiologic and behavioral adaptation to chronic stress, including social defeat in rodent models. In order to test the hypothesis that repeated social defeat alters the emotional behavior and the excitability of brainstem serotonergic systems implicated in control of emotional behavior, we exposed adult male rats either to home cage control conditions, acute social defeat, or social defeat followed 24 h later by a second social defeat encounter. We then assessed behavioral responses during social defeat as well as the excitability of serotonergic neurons within the dorsal raphe nucleus using immunohistochemical staining of tryptophan hydroxylase, a marker of serotonergic neurons, and the protein product of the immediate-early gene, c-fos. Repeated social defeat resulted in a shift away from proactive emotional coping behaviors, such as rearing (explorative escape behavior), and toward reactive emotional coping behaviors such as freezing. Both acute and repeated defeat led to widespread increases in c-Fos expression in serotonergic neurons in the dorsal raphe nucleus. Changes in behavior following a second exposure to social defeat, relative to acute defeat, were associated with decreased c-Fos expression in serotonergic neurons within the dorsal and ventral parts of the mid-rostrocaudal dorsal raphe nucleus, regions that have been implicated in 1) serotonergic modulation of fear- and anxiety-related behavior and 2) defensive behavior in conspecific aggressive encounters, respectively. These data support the hypothesis that serotonergic systems play a role in physiologic and behavioral responses to both

  14. Repeated social defeat increases reactive emotional coping behavior and alters functional responses in serotonergic neurons in the rat dorsal raphe nucleus.

    PubMed

    Paul, Evan D; Hale, Matthew W; Lukkes, Jodi L; Valentine, McKenzie J; Sarchet, Derek M; Lowry, Christopher A

    2011-08-03

    Chronic stress is a vulnerability factor for a number of psychiatric disorders, including anxiety and affective disorders. Social defeat in rats has proven to be a useful paradigm to investigate the neural mechanisms underlying physiologic and behavioral adaptation to acute and chronic stress. Previous studies suggest that serotonergic systems may contribute to the physiologic and behavioral adaptation to chronic stress, including social defeat in rodent models. In order to test the hypothesis that repeated social defeat alters the emotional behavior and the excitability of brainstem serotonergic systems implicated in control of emotional behavior, we exposed adult male rats either to home cage control conditions, acute social defeat, or social defeat followed 24h later by a second social defeat encounter. We then assessed behavioral responses during social defeat as well as the excitability of serotonergic neurons within the dorsal raphe nucleus using immunohistochemical staining of tryptophan hydroxylase, a marker of serotonergic neurons, and the protein product of the immediate-early gene, c-fos. Repeated social defeat resulted in a shift away from proactive emotional coping behaviors, such as rearing (explorative escape behavior), and toward reactive emotional coping behaviors such as freezing. Both acute and repeated defeat led to widespread increases in c-Fos expression in serotonergic neurons in the dorsal raphe nucleus. Changes in behavior following a second exposure to social defeat, relative to acute defeat, were associated with decreased c-Fos expression in serotonergic neurons within the dorsal and ventral parts of the mid-rostrocaudal dorsal raphe nucleus, regions that have been implicated in 1) serotonergic modulation of fear- and anxiety-related behavior and 2) defensive behavior in conspecific aggressive encounters, respectively. These data support the hypothesis that serotonergic systems play a role in physiologic and behavioral responses to both

  15. Serotonin-1A receptor function in the dorsal raphe nucleus following chronic administration of the selective serotonin reuptake inhibitor sertraline.

    PubMed

    Rossi, Dania V; Burke, Teresa F; McCasland, Melissa; Hensler, Julie G

    2008-05-01

    Serotonin-1A (5-HT(1A) receptors in the dorsal raphe nucleus (DRN) function as somatodendritic autoreceptors, and therefore play a critical role in controlling serotonergic cell firing and serotonergic neurotransmission. We hypothesized that a decrease in the capacity of 5-HT(1A) receptors to activate G proteins was a general mechanism by which 5-HT(1A) receptors in the DRN are desensitized following chronic administration of selective serotonin reuptake inhibitors (SSRIs). Using in vivo microdialysis, we found that the ability of the 5-HT(1A) receptor agonist 8-hydroxydipropylaminotetralin hydrobromide (8-OH-DPAT) (0.025 mg/kg, s.c.) to decrease extracellular 5-HT levels in striatum was attenuated following chronic treatment of rats with the SSRIs sertraline or fluoxetine. This apparent desensitization of somatodendritic 5-HT(1A) autoreceptor function was not accompanied by a decrease in 5-HT(1A) receptor sites in the coupled, high-affinity agonist state as measured by the binding of [3H]8-OH-DPAT. In marked contrast to what was observed following chronic administration of fluoxetine, 5-HT(1A) receptor-stimulated [(35)S]GTPgammaS binding in the DRN was not altered following chronic sertraline treatment. Thus, desensitization of 5-HT(1A) somatodendritic autoreceptor function following chronic sertraline administration appears not to be due to a decrease in the capacity 5-HT(1A) receptors to activate G proteins in the DRN. Our findings suggest that the SSRIs may not be a homogeneous class of antidepressant drug with regard to the mechanism by which the function of somatodendritic 5-HT(1A) autoreceptors is regulated.

  16. Presynaptic α4β2 nicotinic acetylcholine receptors increase glutamate release and serotonin neuron excitability in the dorsal raphe nucleus.

    PubMed

    Garduño, Julieta; Galindo-Charles, Luis; Jiménez-Rodríguez, Javier; Galarraga, Elvira; Tapia, Dagoberto; Mihailescu, Stefan; Hernandez-Lopez, Salvador

    2012-10-24

    Several behavioral effects of nicotine are mediated by changes in serotonin (5-HT) release in brain areas that receive serotonergic afferents from the dorsal raphe nucleus (DRN). In vitro experiments have demonstrated that nicotine increases the firing activity in the majority of DRN 5-HT neurons and that DRN contains nicotinic acetylcholine receptors (nAChRs) located at both somata and presynaptic elements. One of the most common presynaptic effects of nicotine is to increase glutamate release. Although DRN receives profuse glutamatergic afferents, the effect of nicotine on glutamate release in the DRN has not been studied in detail. Using whole-cell recording techniques, we investigated the effects of nicotine on the glutamatergic input to 5-HT DRN neurons in rat midbrain slices. Low nicotine concentrations, in the presence of bicuculline and tetrodotoxin (TTX), increased the frequency but did not change the amplitude of glutamate-induced EPSCs, recorded from identified 5-HT neurons. Nicotine-induced increase of glutamatergic EPSC frequency persisted 10-20 min after drug withdrawal. This nicotinic effect was mimicked by exogenous administration of acetylcholine (ACh) or inhibition of ACh metabolism. In addition, the nicotine-induced increase in EPSC frequency was abolished by blockade of α4β2 nAChRs, voltage-gated calcium channels, or intracellular calcium signaling but not by α7 nAChR antagonists. These data suggest that both nicotine and endogenous ACh can increase glutamate release through activation of presynaptic α4β2 but not α7 nAChRs in the DRN. The effect involves long-term changes in synaptic function, and it is dependent on voltage-gated calcium channels and presynaptic calcium stores.

  17. Dorsal-to-Ventral Shift in Midbrain Dopaminergic Projections and Increased Thalamic/Raphe Serotonergic Function in Early Parkinson Disease.

    PubMed

    Joutsa, Juho; Johansson, Jarkko; Seppänen, Marko; Noponen, Tommi; Kaasinen, Valtteri

    2015-07-01

    Loss of nigrostriatal neurons leading to dopamine depletion in the dorsal striatum is the pathologic hallmark of Parkinson disease contributing to the primary motor symptoms of the disease. However, Parkinson pathology is more widespread in the brain, affecting also other dopaminergic pathways and neurotransmitter systems, but these changes are less well characterized. This study aimed to investigate the mesencephalic striatal and extrastriatal dopaminergic projections together with extrastriatal serotonin transporter binding in Parkinson disease. Two hundred sixteen patients with Parkinson disease and 204 control patients (patients without neurodegenerative parkinsonism syndromes and normal SPECT imaging) were investigated with SPECT using the dopamine/serotonin transporter ligand (123)I-N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane ((123)I-FP-CIT) in the clinical setting. The group differences and midbrain correlations were analyzed voxel by voxel over the entire brain. We found that Parkinson patients had lower (123)I-FP-CIT uptake in the striatum and ventral midbrain but higher uptake in the thalamus and raphe nuclei than control patients. In patients with Parkinson disease, the correlation of the midbrain tracer uptake was shifted from the putamen to widespread corticolimbic areas. All findings were highly significant at the voxel level familywise error-corrected P value of less than 0.05. Our findings show that Parkinson disease is associated not only with the degeneration of the nigrostriatal dopamine neurotransmission, but also with a parallel shift toward mesolimbic and mesocortical function. Furthermore, Parkinson disease patients seem to have upregulation of brain serotonin transporter function at the early phase of the disease. © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

  18. Projection patterns from the amygdaloid nuclear complex to subdivisions of the dorsal raphe nucleus in the rat.

    PubMed

    Lee, Hyun S; Eum, Yun J; Jo, Seung M; Waterhouse, Barry D

    2007-04-27

    The goal of the present study was to identify the projection from the subdivisions of the amygdaloid nuclear complex to specified subregions of the dorsal raphe (DR) nucleus and to attempt to compare the density of amygdaloid input to the DR with that of inputs from other limbic structures. Use of a retrograde tracer, gold-conjugated and inactivated wheatgerm agglutinin-horseradish peroxidase (WGA-apo-HRP-gold), demonstrated that amygdaloid input to midline DR subdivision originates mainly from the medial portion of the medial amygdaloid nucleus, whereas that to lateral wing subdivision derives from the region extending from the lateral portion of the medial amygdaloid nucleus to the commissural stria terminalis. Use of the retrograde tracer Fluorogold (FG) produced relatively large but circumscribed injection sites comprising midline DR as well as portions of lateral wing subdivision and confirmed that the medial amygdaloid nucleus provides the major input to the DR. We also demonstrated that although amygdaloid input was not as extensive as inputs from other limbic structures such as the medial prefrontal cortex or the lateral habenular nucleus, it was comparable to input from the lateral septal nucleus. Based on these observations, we suggest that the medial amygdaloid nucleus provides substantial input to the DR and may contribute an emotional influence on sleep-wakefulness cycle or pain-stress modulation. Furthermore, it seems that the medial amygdaloid-DR projection might be anatomically and functionally distinct from the well-characterized central amygdaloid-periaqeductal gray (PAG) circuit which is essential for conditioned fear.

  19. The Role of Prior Stressor Controllability and the Dorsal Raphé Nucleus in Sucrose Preference and Social Exploration

    PubMed Central

    Christianson, John P.; Paul, Evan D.; Irani, Myra; Thompson, Brittany M.; Kubala, Kenneth H.; Yirmiya, Raz; Watkins, Linda R.; Maier, Steven F.

    2008-01-01

    Research investigating how control over stressors affects behavior often utilizes freezing and shuttle escape learning as the behavioral endpoints. These endpoints have been argued to reflect anxious or depressed states, but these descriptions are problematic. The present study sought to determine the impact of stressor controllability and the dorsal raphé nucleus (DRN) on sucrose preference and juvenile social exploration, putative measures of anhedonia and anxiety that are commonly used in studies of stress per se. In Experiment 1 rats were exposed to escapable (ES) or yoked-inescapable (IS) tailshocks. In Experiment 2 ES or IS was given 7 days before all rats received IS. In Experiment 3 the DRN was inactivated during IS by microinjection of 8-OH-DPAT. Sucrose preference and social exploration were tested for several days after stress. A fourth experiment confirmed that juvenile social exploration is sensitive to traditional β-carboline and benzodiazepine manipulations. Both ES and IS reduced sucrose preference, but only IS reduced social exploration. Prior treatment with ES prevented the effect of IS on social exploration but did not prevent the effect of IS on sucrose preference and inactivation of the DRN prevented the effect of IS on social exploration but did not change sucrose preference. The present results indicate that social exploration but not sucrose preference is sensitive to prior stressor controllability, and that DRN activation mediates the effect of IS on social exploration. We argue that DRN-5-HT activation mediates a state of generalized anxiety produced by uncontrollable stress and that juvenile social exploration is a useful behavioral endpoint in stressor controllability studies. PMID:18554730

  20. GABAA receptors in the dorsal raphé nucleus of mice: escalation of aggression after alcohol consumption

    PubMed Central

    Takahashi, Aki; Kwa, Carolyn; DeBold, Joseph F.

    2010-01-01

    Rationale The dorsal raphé nucleus (DRN), the origin for serotonin (5-HT) in forebrain areas, has been implicated in the neural control of escalated aggression. Gamma aminobutyric acid type-A (GABAA) and type-B (GABAB) receptors are expressed in the DRN and modulate 5-HT neuronal activity, and both play a role in the behavioral effect of alcohol. Objective The purpose of this study is to examine the interaction between drugs acting on GABA receptors in the DRN and alcohol in their effects on aggressive behaviors. Method Male CFW mice, housed with a female, were trained to self-administer ethanol (1.0 g/kg) or water via an operant conditioning panel in their home cage. Immediately after they drank either ethanol or water, the animals were microinfused with a GABAergic drug into the DRN, and their aggressive behaviors were assessed 10 min later. Muscimol (0.006 nmol), a GABAA receptor agonist, escalated alcohol-heightened aggression but had no effect in the absence of ethanol. This effect of muscimol was prominent in the animals that showed alcohol-heightened aggression, but not the animals that reduced or did not change aggressive behavior after ethanol infusion compared to water. On the other hand, the GABAB agonist baclofen (0.06 nmol) increased aggressive behavior similarly in both water and ethanol conditions. Antagonists of the GABAA and GABAB receptors, bicuculline (0.006 nmol) and phaclofen (0.3 nmol) respectively, did not suppress heightened-aggressive behavior induced by ethanol self-administration. Conclusion GABAA receptors in the DRN are one of the neurobiological targets of alcohol-heightened aggression. Activation of the GABAB receptors in the DRN also produced escalated aggression, but that is independent of the effect of alcohol. PMID:20589493

  1. Estradiol increases α7 nicotinic receptor in serotonergic dorsal raphe and noradrenergic locus coeruleus neurons of macaques

    PubMed Central

    Centeno, Maria Luisa; Henderson, Jessica A.; Pau, K.-Y. Francis; Bethea, Cynthia L.

    2008-01-01

    Acetylcholine, acting on presynaptic nicotinic receptors (nAChRs) modulates the release of neurotransmitters in the brain. The rat dorsal raphe nucleus (DR) and the locus coeruleus (LC) receive cholinergic input and express the α7nAChR. In previous reports, we demonstrated that estradiol (E) administration stimulates DR serotonergic and LC noradrenergic function in the macaque. In addition, it has been reported that E induces the expression of the α7nAChR in rats. We questioned whether E increased the expression of the α7nAChR in the macaque DR and LC. We utilized double immunostaining to study the effect of a simulated preovulatory surge of E on the expression of the α7nAChR in the DR and the LC and to determine whether α7nAChR colocalizes with serotonin and tyrosine hydroxylase (TH) in macaques. There was no difference in the number of α7nAChR-positive neurons between ovariectomized (OVX) controls and OVX animals treated with a silastic capsule containing E (Ecap). However, supplemental infusion of E for 5–30 h to Ecap animals (Ecap+inf) significantly increased the number of α7nAChR-positive neurons in DR and LC. In addition, supplemental E infusion significantly increased the number of neurons in which α7nAChR colocalized with serotonin and TH. These results constitute an important antecedent to the study of the effects of nicotine and ovarian steroid hormones in the physiological functions regulated by the DR and the LC in woman. PMID:16736471

  2. Lateral habenula and the rostromedial tegmental nucleus innervate neurochemically distinct subdivisions of the dorsal raphe nucleus in the rat.

    PubMed

    Sego, Chemutai; Gonçalves, Luciano; Lima, Leandro; Furigo, Isadora C; Donato, Jose; Metzger, Martin

    2014-05-01

    The lateral habenula (LHb) is an epithalamic structure differentiated in a medial (LHbM) and a lateral division (LHbL). Together with the rostromedial tegmental nucleus (RMTg), the LHb has been implicated in the processing of aversive stimuli and inhibitory control of monoamine nuclei. The inhibitory LHb influence on midbrain dopamine neurons has been shown to be mainly mediated by the RMTg, a mostly GABAergic nucleus that receives a dominant input from the LHbL. Interestingly, the RMTg also projects to the dorsal raphe nucleus (DR), which also receives direct LHb projections. To compare the organization and transmitter phenotype of LHb projections to the DR, direct and indirect via the RMTg, we first placed injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin into the LHb or the RMTg. We then confirmed our findings by retrograde tracing and investigated a possible GABAergic phenotype of DR-projecting RMTg neurons by combining retrograde tracing with in situ hybridization for GAD67. We found only moderate direct LHb projections to the DR, which mainly emerged from the LHbM and were predominantly directed to the serotonin-rich caudal DR. In contrast, RMTg projections to the DR were more robust, emerged from RMTg neurons enriched in GAD67 mRNA, and were focally directed to a distinctive DR subdivision immunohistochemically characterized as poor in serotonin and enriched in presumptive glutamatergic neurons. Thus, besides its well-acknowledged role as a GABAergic control center for the ventral tegmental area (VTA)-nigra complex, our findings indicate that the RMTg is also a major GABAergic relay between the LHb and the DR.

  3. Cellular adaptations of dorsal raphe serotonin neurons associated with the development of active coping in response to social stress

    PubMed Central

    Wood, Susan K.; Zhang, Xiao-Yan; Reyes, Beverly A.S.; Lee, Catherine S.; Van Bockstaele, Elisabeth J.; Valentino, Rita J.

    2013-01-01

    Background Social stress is a risk factor for affective disorders for certain vulnerable individuals. Stress and depression are linked in part through regulation of the dorsal raphe (DR)-serotonin (5-HT) system by the stress-related neuropeptide, corticotropin-releasing factor (CRF). Here we used a rat social stress model that shows individual differences in coping strategies to determine whether differences in CRF-5-HT interactions underlie individual differences in the vulnerability to social stress. Methods Rats were exposed to the resident-intruder model of social stress for 5 days. In vivo single unit recordings assessed DR-5-HT neuronal responses to CRF and immunoelectron microscopy assessed CRF1 and CRF2 cellular localization 24 h after the last stress. Results Rats responded to social stress passively, assuming defeat with short latencies (SL, 48%) or actively with proactive behaviors and longer defeat latencies (LL, 52%). Whereas CRF (30 ng, intra-DR) inhibited 5-HT neuronal activity of control and SL rats, it activated 5-HT neurons of LL rats, an effect that was CRF2 mediated. Consistent with this, social stress promoted CRF1 internalization together with CRF2 recruitment to the plasma membrane of DR neurons selectively in LL rats. Conclusions These data suggest that a proactive coping strategy towards social stress is associated with a redistribution of CRF1 and CRF2 in DR-5-HT neurons that primes the system to be activated by subsequent stress. The lack of this adaptation in passive coping rats may contribute to their depressive-like phenotype. These studies provide a cellular mechanism for individual differences in stress responses and consequences. PMID:23452664

  4. 5-HT7 receptor modulates GABAergic transmission in the rat dorsal raphe nucleus and controls cortical release of serotonin.

    PubMed

    Kusek, Magdalena; Sowa, Joanna; Kamińska, Katarzyna; Gołembiowska, Krystyna; Tokarski, Krzysztof; Hess, Grzegorz

    2015-01-01

    The 5-HT7 receptor is one of the several serotonin (5-HT) receptor subtypes that are expressed in the dorsal raphe nucleus (DRN). Some earlier findings suggested that 5-HT7 receptors in the DRN were localized on GABAergic interneurons modulating the activity of 5-HT projection neurons. The aim of the present study was to find out how the 5-HT7 receptor modulates the GABAergic synaptic input to putative 5-HT DRN neurons, and whether blockade of the 5-HT7 receptor would affect the release of 5-HT in the target structure. Male Wistar rats with microdialysis probes implanted in the prefrontal cortex (PFC) received injections of the 5-HT7 receptor antagonist (2R)-1-[(3-hydroxyphenyl)sulfonyl]-2-[2-(4-methyl-1-piperidinyl)ethyl]pyrrolidine hydrochloride (SB 269970), which induced an increase in the levels of 5-HT and its metabolite, 5-hydroxyindoleacetic acid (5-HIAA) in the PFC. In another set of experiments whole-cell recordings from presumed projection neurons were carried out using DRN slices. SB 269970 application resulted in depolarization and in an increase in the firing frequency of the cells. In order to activate 5-HT7 receptors, 5-carboxamidotryptamine (5-CT) was applied in the presence of N-[2-[4-(2-methoxyphenyl)-1piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY100635). Hyperpolarization of cells and a decrease in the firing frequency were observed after activation of the 5-HT7 receptor. Blockade of 5-HT7 receptors caused a decrease in the mean frequency of spontaneous inhibitory postsynaptic currents (sIPSCs), while its activation induced an increase. The mechanism of these effects appears to involve tonically-active 5-HT7 receptors modulating firing and/or GABA release from inhibitory interneurons which regulate the activity of DRN serotonergic projection neurons.

  5. The cholinergic agonist carbachol increases the frequency of spontaneous GABAergic synaptic currents in dorsal raphe serotonergic neurons in the mouse.

    PubMed

    Yang, C; Brown, R E

    2014-01-31

    Dorsal raphe nucleus (DRN) serotonin (5-HT) neurons play an important role in feeding, mood control and stress responses. One important feature of their activity across the sleep-wake cycle is their reduced firing during rapid-eye-movement (REM) sleep which stands in stark contrast to the wake/REM-on discharge pattern of brainstem cholinergic neurons. A prominent model of REM sleep control posits a reciprocal interaction between these cell groups. 5-HT inhibits cholinergic neurons, and activation of nicotinic receptors can excite DRN 5-HT neurons but the cholinergic effect on inhibitory inputs is incompletely understood. Here, in vitro, in DRN brain slices prepared from GAD67-GFP knock-in mice, a brief (3 min) bath application of carbachol (50 μM) increased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) in GFP-negative, putative 5-HT neurons but did not affect miniature (tetrodotoxin-insensitive) IPSCs. Carbachol had no direct postsynaptic effect. Thus, carbachol likely increases the activity of local GABAergic neurons which synapse on 5-HT neurons. Removal of dorsal regions of the slice including the ventrolateral periaqueductal gray (vlPAG) region where GABAergic neurons projecting to the DRN have been identified, abolished the effect of carbachol on sIPSCs whereas the removal of ventral regions containing the oral region of the pontine reticular nucleus (PnO) did not. In addition, carbachol directly excited GFP-positive, GABAergic vlPAG neurons. Antagonism of both muscarinic and nicotinic receptors completely abolished the effects of carbachol. We suggest cholinergic neurons inhibit DRN 5-HT neurons when acetylcholine levels are lower i.e. during quiet wakefulness and the beginning of REM sleep periods, in part via excitation of muscarinic and nicotinic receptors located on local vlPAG and DRN GABAergic neurons. Higher firing rates or burst firing of cholinergic neurons associated with attentive wakefulness or phasic REM sleep periods

  6. [EXPRESSION OF SEROTONIN TRANSPORTER IN THE DORSAL RAPHE NUCLEUS DURING THE EARLY POSTNATAL PERIOD IN NORMAL STATE AND UNDER PRENATAL DEFICIENCY OF THE SEROTONERGIC SYSTEM IN RATS].

    PubMed

    Khozhai, L I

    2016-01-01

    The expression of the serotonin transport membrane protein (5-NTT) in the dorsal raphe nucleus (DNR) was investigated in laboratory Wistar rats during the early postnatal period. The results of the immunocytochemical study using primary antibodies--anti-Serotonin transporter antibody (AbCam, UK)--showed that during the first 3 postnatal weeks the intensity of 5-NTT expression in DNR of control animals changes. At the earliest postnatal times the main part of subnuclear neurons (dorsal, ventral and lateral ones) of the dorsal raphe nucleus (DNR-d, DNR-v, DNR-lat) was shown to intensely express 5-NTT. Sites of 5-NTT localization are found on the membrane surface of neuron bodies and processes in neuropile. The reduction in the number of neurons expressing 5-NTT and of its binding sites was observed on P10. At this time a redistribution of 5-NTT localization sites occurs: they are very few on neuron bodies and dendrites but are located rather densely on the plasma membrane of axons. The number of neurons expressing 5-NTT gradually increases with age and in neuropile the density of 5-NTT localization sites rises. It is shown that during the prenatal development the reduction of serotonin level in all parts of the DNR leads to a reduction in both the number of neurons expressing 5-NTT and sites of its localization in the early postnatal period, this trend continuing with age.

  7. Cannabidiol inhibits the reward-facilitating effect of morphine: involvement of 5-HT1A receptors in the dorsal raphe nucleus.

    PubMed

    Katsidoni, Vicky; Anagnostou, Ilektra; Panagis, George

    2013-03-01

    Cannabidiol is a non-psychotomimetic constituent of Cannabis sativa, which induces central effects in rodents. It has been shown that cannabidiol attenuates cue-induced reinstatement of heroin seeking. However, to the best of our knowledge, its effects on brain stimulation reward and the reward-facilitating effects of drugs of abuse have not yet been examined. Therefore, we investigated the effects of cannabidiol on brain reward function and on the reward-facilitating effect of morphine and cocaine using the intracranial self-stimulation (ICSS) paradigm. Rats were prepared with a stimulating electrode into the medial forebrain bundle (MFB), and a guide cannula into the dorsal raphe (microinjection experiments), and were trained to respond for electrical brain stimulation. A low dose of cannabidiol did not affect the reinforcing efficacy of brain stimulation, whereas higher doses significantly elevated the threshold frequency required for MFB ICSS. Both cocaine and morphine lowered ICSS thresholds. Cannabidiol inhibited the reward-facilitating effect of morphine, but not cocaine. This effect was reversed by pre-treatment with an intra-dorsal raphe injection of the selective 5-HT1A receptor antagonist WAY-100635. The present findings indicate that cannabidiol does not exhibit reinforcing properties in the ICSS paradigm at any of the doses tested, while it decreases the reward-facilitating effects of morphine. These effects were mediated by activation of 5-HT1A receptors in the dorsal raphe. Our results suggest that cannabidiol interferes with brain reward mechanisms responsible for the expression of the acute reinforcing properties of opioids, thus indicating that cannabidiol may be clinically useful in attenuating the rewarding effects of opioids.

  8. Chronic low dose ovine corticotropin releasing factor or urocortin II into the rostral dorsal raphe alters exploratory behavior and serotonergic gene expression in specific subregions of the dorsal raphe

    PubMed Central

    Clark, Michael S.; McDevitt, Ross A.; Hoplight, Blair J.; Neumaier, John F.

    2007-01-01

    Corticotropin releasing factor (CRF) family peptides play key roles in integrating neural responses to stress. Both major CRF receptors have been pharmacologically identified in the dorsal raphe nucleus (DRN), a stress sensitive and internally heterogeneous nucleus supplying many forebrain regions with serotonergic input. Despite the involvement of chronic stress and serotonergic dysfunction in human mood and anxiety disorders, little is known about the effects of chronic CRF receptor activation on the DRN. We infused ovine CRF (1ng/hr), urocortin II (UCNII, 1ng/hr), or vehicle alone into rat DRN over 6 days. During infusion, animals were allowed to freely explore an open field for 15 minutes on each of two days, with the addition of a novel object on the second day. Following behavioral testing, 5-HT1A, 5-HT1B, serotonin transporter (SERT), and tryptophan hydroxylase-2 (Tph2) expression were examined through the DRN by in situ hybridization. Ovine CRF infusion resulted in significantly decreased novel object touches, climbs, as well as increased latency to first novel object contact. UCNII had a similar but less dramatic effect, decreasing only climbing behavior. Both ovine CRF and UCNII blunted the decrease in corner time expected on re-exposure to the open field. Both peptides also produced regionally specific changes in gene expression: 5-HT1A expression was increased 30% in the mid-rostral ventromedial DRN, while SERT was decreased by 30% in the mid-caudal shell dorsomedial DRN. There also appeared to be a shift in the relative level of Tph2 expression between the ventromedial and core dorsomedial DRN at the mid-rostral level. Changes in 5-HT1A, SERT, and relative Tph2 mRNA abundance were correlated with novel object exploration. These findings suggest chronic intra-DRN administration of CRF agonists decreases exploratory behavior, while producing subregionally limited changes in serotonergic gene expression. These studies may be relevant to mechanisms

  9. The comparative effects of environmental enrichment with exercise and serotonin transporter blockade on serotonergic neurons in the dorsal raphe nucleus.

    PubMed

    MacGillivray, Lindsey; Reynolds, Katelyn B; Rosebush, Patricia I; Mazurek, Michael F

    2012-05-01

    We have previously reported that inhibition of the serotonin transporter (SERT) by selective serotonin reuptake inhibitor (SSRI) fluoxetine significantly reduces the number of tryptophan hydroxylase (TPH)-positive cells in the dorsal raphe nucleus (DRN). We have been interested in exploring whether this SSRI-induced change in TPH might be modified by housing in an enriched environment. Like SSRI antidepressants, environmental enrichment (EE) and physical exercise have been found to have efficacy in the prevention and alleviation of depression. We postulated that EE with exercise and SERT inhibition would similarly affect TPH regulation and that EE with exercise might modify the effect of fluoxetine on TPH. Three week old male Sprague-Dawley rats were housed in either a standard cage (SE) or an enriched environment (EE). SE animals were singly housed with no access to enrichment objects. EE animals were group housed and were provided with various enrichment objects (e.g. running wheel) that were changed and rearranged regularly. Nine weeks after the experiment began, the rats were randomly assigned to one of four treatment groups: (1) SE control; (2) SE fluoxetine; (3) EE control; or (4) EE fluoxetine. Fluoxetine (5 mg/kg/day) was placed in the drinking water. Sections of DRN were processed for TPH immunohistochemistry. The number of TPH-positive cells was determined by blinded, manual counting. Results were analyzed by analysis of variance (ANOVA) followed by post-hoc Tukey tests. Significance was set at P < 0.05. For animals housed in a standard environment, fluoxetine induced a significant 29% reduction in the number of TPH-immunoreactive cells in the DRN. A similar reduction in TPH immunoreactivity was observed in animals that were housed in an enriched environment but not exposed to fluoxetine (39%). The number of TPH-positive cells in the DRN for animals housed in an enriched environment and exposed to fluoxetine was not significantly different than animals

  10. Body Sodium Overload Modulates the Firing Rate and Fos Immunoreactivity of Serotonergic Cells of Dorsal Raphe Nucleus

    PubMed Central

    Godino, Andrea; Pitra, Soledad; Carrer, Hugo F.; Vivas, Laura

    2013-01-01

    In order to determine whether serotonergic (5HT) dorsal raphe nucleus (DRN) cells are involved in body sodium status regulation, the effect of a s.c. infusion of either 2 M or 0.15 M NaCl on 5HT DRN neuron firing was studied using single unit extracellular recordings. In separate groups of 2 M and 0.15 M NaCl-infused rats, water intake, oxytocin (OT) plasma concentration, urine and plasma sodium and protein concentrations were also measured. Also, to determine the involvement of particular brain nuclei and neurochemical systems in body sodium overload (SO), animals from both groups were perfused for brain immunohistochemical detection of Fos, Fos-OT and Fos-5HT expression. SO produced a significant increase in serotonergic DRN neuron firing rate compared to baseline and 0.15 M NaCl-infused rats. As expected, 2 M NaCl s.c. infusion also induced a significant increase of water intake, diuresis and natriuresis, plasma sodium concentration and osmolality, even though plasma volume did not increase as indicated by changes in plasma protein concentration. The distribution of neurons along the forebrain and brainstem expressing Fos after SO showed the participation of the lamina terminalis, extended amygdala, supraoptic and paraventricular hypothalamic nuclei in the neural network that controls osmoregulatory responses. Both Fos-OT immunoreactive and plasma OT concentration increased after s.c. hypertonic sodium infusion. Finally, matching the “in vivo” electrophysiological study, SO doubled the number of Fos-5HT immunolabeled cells within the DRN. In summary, the results characterize the behavioral, renal and endocrine responses after body sodium overload without volume expansion and specify the cerebral nuclei that participate at different CNS levels in the control of these responses. The electrophysiological approach also allows us to determine in an “in vivo" model that DRN 5HT neurons increase their firing frequency during an increase in systemic sodium

  11. Body sodium overload modulates the firing rate and fos immunoreactivity of serotonergic cells of dorsal raphe nucleus.

    PubMed

    Godino, Andrea; Pitra, Soledad; Carrer, Hugo F; Vivas, Laura

    2013-01-01

    In order to determine whether serotonergic (5HT) dorsal raphe nucleus (DRN) cells are involved in body sodium status regulation, the effect of a s.c. infusion of either 2 M or 0.15 M NaCl on 5HT DRN neuron firing was studied using single unit extracellular recordings. In separate groups of 2 M and 0.15 M NaCl-infused rats, water intake, oxytocin (OT) plasma concentration, urine and plasma sodium and protein concentrations were also measured. Also, to determine the involvement of particular brain nuclei and neurochemical systems in body sodium overload (SO), animals from both groups were perfused for brain immunohistochemical detection of Fos, Fos-OT and Fos-5HT expression. SO produced a significant increase in serotonergic DRN neuron firing rate compared to baseline and 0.15 M NaCl-infused rats. As expected, 2 M NaCl s.c. infusion also induced a significant increase of water intake, diuresis and natriuresis, plasma sodium concentration and osmolality, even though plasma volume did not increase as indicated by changes in plasma protein concentration. The distribution of neurons along the forebrain and brainstem expressing Fos after SO showed the participation of the lamina terminalis, extended amygdala, supraoptic and paraventricular hypothalamic nuclei in the neural network that controls osmoregulatory responses. Both Fos-OT immunoreactive and plasma OT concentration increased after s.c. hypertonic sodium infusion. Finally, matching the "in vivo" electrophysiological study, SO doubled the number of Fos-5HT immunolabeled cells within the DRN. In summary, the results characterize the behavioral, renal and endocrine responses after body sodium overload without volume expansion and specify the cerebral nuclei that participate at different CNS levels in the control of these responses. The electrophysiological approach also allows us to determine in an "in vivo" model that DRN 5HT neurons increase their firing frequency during an increase in systemic sodium concentration

  12. Dorsal raphe nucleus of brain in the rats flown in space inflight and postflight alteration of structure

    NASA Astrophysics Data System (ADS)

    Krasnov, I.

    The structure of brain dorsal raphe nucleus (DRN) was studied in the rats flown in space aboard Space Shuttle "Columbia" (STS-58, SLS-2 program) and dissected on day 13 of the mission ("inflight" rats) and in 5-6 hours after finishing 14-day flight ("postflight" rats). The brain of "inflight" rats were excised after decapitation, sectioned sagitally halves of brain were fixed by immersion in 2,5 % glutaraldehyde in 0.1 M cacodylate buffer pH 7.3 at 4°C and kept in the flight at 4°C. After landing the brain frontal 0.5 mm sections from DRN area were osmificated and embedded in araldite at NASA ARC. The brains of "postflight": and control rats were underwent to the same procedure. Electronmicroscopical analysis, computer morphometry and glial cell count were performed at Moscow. In DRN neuropil of "inflight" rats the most part of axo-dendritic synapses were surrounded by glia cell processes and had decreased electron density of pre- and postsynaptic membrane and pronounced diminution of synaptic vesicle amount while dendrites were characterized by decrease in matrix electron density and microtubule quantity that in total indicates the decline of afferent flow reaching DRN neurons in microgravity. In DRN neurons of "inflight" rats all mitochondria were characterized by evenly increased dimensions, decreased matrix electron density, small amount of short and far- between located cristae and enlarged intermembrane and intercristae spaces, that in total points out low level of coupling of oxidation to phosphorilation, decrease in energy supply of neuron. Amount of ribosome in cytoplasm was significantly decreased indicating lower lever of biosynthetic processes. The last is supported by diminished dimensions of neuronal body, nucleus and nucleolus (place of r RNA synthesis), cross section area of that were reduced in DRN neurons of "inflight" rats by 18.8 % (p < 0.01), 11.1 % and 26.6 % (p <0,005) correspondingly. Ultrastructure and dimensions of intracellular

  13. Involvement of pre- and post-synaptic serotonergic receptors of dorsal raphe nucleus neural network in the control of the sweet-substance-induced analgesia in adult Rattus norvegicus (Rodentia, Muridae).

    PubMed

    Miyase, Cátia Isumi; Kishi, Renato; de Freitas, Renato Leonardo; Paz, Denise Amorim; Coimbra, Norberto Cysne

    2005-05-13

    In order to investigate the effects of monoaminergic mechanisms of the dorsal raphe nucleus on the elaboration and control of sweet-substance-induced antinociception, male albino Wistar rats weighing 180-200 g received sucrose solution (250 g/L) for 14 days as their only source of liquid. After the chronic consumption of sucrose solution, each animal was pretreated with unilateral microinjection of methiothepin mesylate (5.0 microg/0.2 microL), or methysergide maleate (5.0 microg/0.2 microL) in the dorsal raphe nucleus. Each rat consumed an average of 15.6g sucrose/day. Their tail withdrawal latencies in the tail-flick test were measured immediately before and after this treatment. An analgesia index was calculated from the withdrawal latencies before and after the pharmacological treatment. The blockade of serotonergic receptor in the dorsal raphe nucleus with methysergide after the chronic intake of sucrose decreased the sweet-induced antinociception. However, microinjections of methiothepin in the dorsal raphe nucleus did not cause a similar effect on the tail-flick latencies after the chronic intake of sucrose solution, increasing the sweet-substance-induced analgesia. These results indicate the involvement of serotonin as a neurotransmitter in the sucrose-produced antinociception. Considering that the blockade of pre-synaptic serotonergic receptors of the neural networks of the dorsal raphe nucleus with methiothepin did not decrease the sweet-substance-induced antinociception, and the central blockade of post-synaptic serotonergic receptors decreased the sucrose-induced analgesia, the modulation of the release of serotonin in the neural substrate of the dorsal raphe nucleus seems to be crucial for the organization of this interesting antinociceptive process.

  14. Differential regulation of serotonin-1A receptor-stimulated [35S]GTP gamma S binding in the dorsal raphe nucleus by citalopram and escitalopram.

    PubMed

    Rossi, Dania V; Burke, Teresa F; Hensler, Julie G

    2008-03-31

    The effect of chronic citalopram or escitalopram administration on 5-HT1A receptor function in the dorsal raphe nucleus was determined by measuring [35S]GTP gamma S binding stimulated by the 5-HT1A receptor agonist (R)-(+)-8-OH-DPAT (1nM-10 microM). Although chronic administration of citalopram or escitalopram has been shown to desensitize somatodendritic 5-HT1A autoreceptors, we found that escitalopram treatment decreased the efficacy of 5-HT1A receptors to activate G proteins, whereas citalopram treatment did not. The binding of [3H]8-OH-DPAT to the coupled, high affinity agonist state of the receptor was not altered by either treatment. Interestingly, escitalopram administration resulted in greater occupancy of serotonin transporter sites as measured by the inhibition of [3H]cyanoimipramine binding. As the binding and action of escitalopram is limited by the inactive enantiomer R-citalopram present in racemic citalopram, we propose that the regulation of 5-HT1A receptor function in the dorsal raphe nucleus at the level of receptor-G protein interaction may be a result of greater inhibition of the serotonin transporter by escitalopram.

  15. Effects of 8-OH-DPAT, 5-CT and muscimol on behaviour maintained by a DRL20 schedule of reinforcement, following microinjection into the dorsal or median raphe nuclei.

    PubMed

    Fletcher, P.J.

    1994-06-01

    Experiments were performed to investigate the effects of microinjections of the 5-HT(1A) agonist 8- hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), the non-selective 5-HT(1) agonist 5-carboxamidotryptamine (5-CT) and the GABA(A) agonist muscimol into the midbrain raphe nuclei, on behaviour maintained by a differential reinforcement of low rate (DRL) 20 schedule of food reinforcement. Following acquisition of responding under the DRL20 schedule, in which responses were reinforced only if they occurred at least 20s after the previous response, two groups of rats were prepared with a stainless steel guide cannula aimed at either the dorsal raphe nucleus or the median raphe nucleus. Injections of 8-OH-DPAT and 5-CT into the median raphe dose-dependently increased responding and reduced the number of reinforcers earned, leading to a net reduction in response efficiency from 45% to approximately 27% (5µg 8-OH-DPAT) and 22% (375ng 5-CT). Both drugs appeared to shift the frequency distribution of inter-response times (IRTs) towards shorter IRTs, and lowered the mean IRT. These effects were not observed after dorsal raphe injections of either drug. This pattern of results, together with results obtained in other paradigms measuring response inhibition, suggests that suppression of the activity of median raphe 5-HT neurones induces deficits in the ability to withhold responding. Muscimol increased responding, decreased the number of reinforcers earned and reduced response efficiency after both dorsal raphe and median raphe injections. These effects were more pronounced following median raphe injections, and were of considerably greater magnitude than those observed following treatment with the 5-HT agonists. Muscimol injected into the median raphe lowered the mean IRT, and increased the frequency of short duration IRTs. Thus, stimulation of GABA(A) receptors within the median raphe induces a pattern of behavioural disruption in the DRL task, that is more severe than that

  16. Medial hypothalamic 5-hydroxytryptamine (5-HT)1A receptors regulate neuroendocrine responses to stress and exploratory locomotor activity: application of recombinant adenovirus containing 5-HT1A sequences.

    PubMed

    Li, Qian; Holmes, Andrew; Ma, Li; Van de Kar, Louis D; Garcia, Francisca; Murphy, Dennis L

    2004-12-01

    Our previous studies found that serotonin transporter (SERT) knock-out mice showed increased sensitivity to minor stress and increased anxiety-like behavior but reduced locomotor activity. These mice also showed decreased density of 5-hydroxytryptamine (5-HT1A) receptors in the hypothalamus, amygdala, and dorsal raphe. To evaluate the contribution of hypothalamic 5-HT1A receptors to these phenotypes of SERT knock-out mice, two studies were conducted. Recombinant adenoviruses containing 5-HT1A sense and antisense sequences (Ad-1AP-sense and Ad-1AP-antisense) were used to manipulate 5-HT1A receptors in the hypothalamus. The expression of the 5-HT1A genes is controlled by the 5-HT1A promoter, so that they are only expressed in 5-HT1A receptor-containing cells. (1) Injection of Ad-1AP-sense into the hypothalamus of SERT knock-out mice restored 5-HT1A receptors in the medial hypothalamus; this effect was accompanied by elimination of the exaggerated adrenocorticotropin responses to a saline injection (minor stress) and reduced locomotor activity but not by a change in increased exploratory anxiety-like behavior. (2) To further confirm the observation in SERT-/- mice, Ad-1AP-antisense was injected into the hypothalamus of normal mice. The density and the function of 5-HT1A receptors in the medial hypothalamus were significantly reduced in Ad-1AP-antisense-treated mice. Compared with the control group (injected with Ad-track), Ad-1A-antisense-treated mice showed a significant reduction in locomotor activity, but again no changes in exploratory anxiety-like behaviors, tested by elevated plus-maze and open-field tests. Thus, the present results demonstrate that medial hypothalamic 5-HT1A receptors regulate stress responses and locomotor activity but may not regulate exploratory anxiety-like behaviors.

  17. Acute and subchronic treatments with selective serotonin reuptake inhibitors increase Nociceptin/Orphanin FQ (NOP) receptor density in the rat dorsal raphe nucleus; interactions between nociceptin/NOP system and serotonin.

    PubMed

    Le Maître, Erwan; Dourmap, Nathalie; Vilpoux, Catherine; Leborgne, Romain; Janin, François; Bonnet, Jean-Jacques; Costentin, Jean; Leroux-Nicollet, Isabelle

    2013-07-03

    Nociceptin/Orphanin FQ is the endogenous ligand of NOP receptor, formerly referred to as the Opioid Receptor-Like 1 receptor. We have previously shown that NOP receptors were located on serotonergic neurons in the rat dorsal raphe nucleus, suggesting possible direct interactions between nociceptin and serotonin in this region, which is a target for antidepressant action. In the present study, we investigated further the link between Selective Serotonin Reuptake Inhibitor (SSRI) antidepressant treatments and the nociceptin/NOP receptor system. Intraperitoneal administration of the SSRI citalopram induced an increase in NOP-receptor density, measured by autoradiographic [(3)H] nociceptin binding, in the rat dorsal raphe nucleus, from the first to the 21st day of treatment. This effect was also observed with other SSRIs (sertraline, fluoxetine), but not with two tricyclic antidepressants (imipramine, clomipramine) and was abolished by pre-treatment with para-chlorophenylalanine, an inhibitor of serotonin synthesis. Using microdialysis experiments, we demonstrated that NOP-receptor activation by infusion of nociceptin 10(-6) M or 10(-5) M increased the level of extracellular serotonin in the dorsal raphe nucleus. This effect was abolished by co-infusion of the NOP-receptor antagonist UFP 101. These results confirm the existence of reciprocal interactions between serotonin and nociceptin/NOP transmissions in the dorsal raphe nucleus.

  18. Bupropion-induced inhibition of α7 nicotinic acetylcholine receptors expressed in heterologous cells and neurons from dorsal raphe nucleus and hippocampus.

    PubMed

    Vázquez-Gómez, Elizabeth; Arias, Hugo R; Feuerbach, Dominik; Miranda-Morales, Marcela; Mihailescu, Stefan; Targowska-Duda, Katarzyna M; Jozwiak, Krzysztof; García-Colunga, Jesús

    2014-10-05

    The pharmacological activity of bupropion was compared between α7 nicotinic acetylcholine receptors expressed in heterologous cells and hippocampal and dorsal raphe nucleus neurons. The inhibitory activity of bupropion was studied on GH3-α7 cells by Ca2+ influx, as well as on neurons from the dorsal raphe nucleus and interneurons from the stratum radiatum of the hippocampal CA1 region by using a whole-cell voltage-clamp technique. In addition, the interaction of bupropion with the α7 nicotinic acetylcholine receptor was determined by [3H]imipramine competition binding assays and molecular docking. The fast component of acetylcholine- and choline-induced currents from both brain regions was inhibited by methyllycaconitine, indicating the participation of α7-containing nicotinic acetylcholine receptors. Choline-induced currents in hippocampal interneurons were partially inhibited by 10 µM bupropion, a concentration that could be reached in the brain during clinical administration. Additionally, both agonist-induced currents were reversibly inhibited by bupropion at concentrations that coincide with its inhibitory potency (IC50=54 µM) and binding affinity (Ki=63 µM) for α7 nicotinic acetylcholine receptors from heterologous cells. The [3H]imipramine competition binding and molecular docking results support a luminal location for the bupropion binding site(s). This study may help to understand the mechanisms of actions of bupropion at neuronal and molecular levels related with its therapeutic actions on depression and for smoking cessation. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Hypocretin/Orexin Peptides Alter Spike Encoding by Serotonergic Dorsal Raphe Neurons through Two Distinct Mechanisms That Increase the Late Afterhyperpolarization

    PubMed Central

    Ishibashi, Masaru; Gumenchuk, Iryna; Miyazaki, Kenichi; Inoue, Takafumi; Ross, William N.

    2016-01-01

    Orexins (hypocretins) are neuropeptides that regulate multiple homeostatic processes, including reward and arousal, in part by exciting serotonergic dorsal raphe neurons, the major source of forebrain serotonin. Here, using mouse brain slices, we found that, instead of simply depolarizing these neurons, orexin-A altered the spike encoding process by increasing the postspike afterhyperpolarization (AHP) via two distinct mechanisms. This orexin-enhanced AHP (oeAHP) was mediated by both OX1 and OX2 receptors, required Ca2+ influx, reversed near EK, and decayed with two components, the faster of which resulted from enhanced SK channel activation, whereas the slower component decayed like a slow AHP (sAHP), but was not blocked by UCL2077, an antagonist of sAHPs in some neurons. Intracellular phospholipase C inhibition (U73122) blocked the entire oeAHP, but neither component was sensitive to PKC inhibition or altered PKA signaling, unlike classical sAHPs. The enhanced SK current did not depend on IP3-mediated Ca2+ release but resulted from A-current inhibition and the resultant spike broadening, which increased Ca2+ influx and Ca2+-induced-Ca2+ release, whereas the slower component was insensitive to these factors. Functionally, the oeAHP slowed and stabilized orexin-induced firing compared with firing produced by a virtual orexin conductance lacking the oeAHP. The oeAHP also reduced steady-state firing rate and firing fidelity in response to stimulation, without affecting the initial rate or fidelity. Collectively, these findings reveal a new orexin action in serotonergic raphe neurons and suggest that, when orexin is released during arousal and reward, it enhances the spike encoding of phasic over tonic inputs, such as those related to sensory, motor, and reward events. SIGNIFICANCE STATEMENT Orexin peptides are known to excite neurons via slow postsynaptic depolarizations. Here we elucidate a significant new orexin action that increases and prolongs the postspike

  20. An examination of 5-hydroxytryptamine receptors in human saphenous vein.

    PubMed Central

    Docherty, J. R.; Hyland, L.

    1986-01-01

    We have examined the effects of antagonists on the isometric contraction of the human saphenous vein produced by 5-hydroxytryptamine (5-HT). The 5-HT2-antagonist ketanserin (1 microM) had little effect on the lower part of the concentration-response curve to 5-HT, but markedly shifted the upper part of the curve. Yohimbine caused an approximately parallel shift of the concentration-response curve to 5-HT, with a pA2 of 5.48, much lower than its pA2 against noradrenaline in the absence (6.36) or presence (7.06) of cocaine. It is concluded that there are two components to the contractile response to 5-HT in human saphenous vein: at low concentrations 5-HT activates a yohimbine-sensitive receptor, and at higher concentrations 5-HT activates a 5-HT2-receptor. PMID:3801780

  1. Pharmacological properties of phenyldiguanide and other amidine derivatives in relation to those of 5-hydroxytryptamine

    PubMed Central

    Fastier, F. N.; McDowall, M. A.; Waal, Hendrieka

    1959-01-01

    Cats in which the coronary and allied chemoreflexes could not be obtained with small intravenous doses of 5-hydroxytryptamine were insensitive also to phenyldiguanide. In cats which responded to phenyldiguanide with reflex falls of blood pressure and heart rate, abolished by vagotomy, the effects of graded doses (5 to 150 μg./kg.) of phenyldiguanide bore a striking resemblance to those produced initially by 5-hydroxytryptamine in somewhat smaller doses. Differences in the cardiovascular responses to the two drugs are attributed to additional (non-reflex) actions of 5-hydroxytryptamine. The reflex actions of both drugs were blocked reversibly also by 2-naphthylguanidine (500 μg.). Certain other drugs (bufotenine, procaine, S-decylisothiourea) antagonized the depressor action of phenyldiguanide as well as the reflex depressor action of 5-hydroxytryptamine. Like 5-hydroxytryptamine, phenyldiguanide and certain other amidine derivatives caused pain when applied to the base of blisters in human subjects. Unlike 5-hydroxytryptamine, phenyldiguanide did not constrict perfused rat blood vessels or increase the tone of the rat fundal strip preparation of Vane (1957). Phenyldiguanide did not affect the sensitivity of these smooth muscle preparations to 5-hydroxytryptamine, but other amidine derivatives proved to be moderately strong antagonists of the vasoconstrictor actions of 5-hydroxytryptamine and of adrenaline. Unlike 5-hydroxytryptamine, phenyldiguanide did not produce gastric haemorrhage in the mouse. Phenyldiguanide did not prolong chloral hydrate sleeping time in mice by the same mechanism as did 5-hydroxytryptamine. Phenyldiguanide was not highly toxic to mice (LD50 being 240 mg./kg.). It is concluded that phenyldiguanide and certain other amidine derivatives act on sensory receptors which respond to 5-hydroxytryptamine, but that they show little pharmacological resemblance to 5-hydroxytryptamine in other respects. PMID:13821683

  2. Acoustic stimulation in vivo and corticotropin-releasing factor in vitro increase tryptophan hydroxylase activity in the rat caudal dorsal raphe nucleus.

    PubMed

    Evans, Andrew K; Heerkens, Jasper L T; Lowry, Christopher A

    2009-05-08

    Exposure of rats to unpredictable loud sound pulses increases activity of the rate-limiting enzyme for serotonin synthesis, tryptophan hydroxylase (TPH), in the median raphe nucleus (MnR) and a mesolimbocortical serotonergic system. Corticotropin-releasing factor (CRF)-induced activation of a subset of serotonergic neurons in the caudal dorsal raphe nucleus (DR) may underlie stress-related increases in TPH activity in the MnR and a mesolimbocortical serotonergic system. An in vivo acoustic stimulation paradigm and an in vitro brain slice preparation were designed to test the hypothesis that stress-related stimuli and CRF receptor activation have convergent actions on TPH activity in the caudal DR (DRC). We measured 5-hydroxytryptophan (5-HTP) accumulation as an index of TPH activity following inhibition of aromatic amino acid decarboxylase (using NSD-1015). To examine effects of acoustic stimulation on TPH activity, male Wistar rats, pretreated with NSD-1015, were exposed to a 30 min sham, predictable or unpredictable acoustic stimulation paradigm; brains were frozen and microdissected for analyses of tissue 5-HTP concentrations in subregions of the DR. To examine the effect of CRF receptor activation on TPH activity, freshly prepared brain slices were exposed to CRF (0-2000 nM) for 10 min in the presence of NSD-1015, then frozen and microdissected for analysis of tissue 5-HTP concentrations. Increases in TPH activity in the DRC, but not other subregions, were observed in both paradigms. These findings are consistent with the hypothesis that stress-related increases in TPH activity are mediated via effects of CRF or CRF-related neuropeptides on a mesolimbocortical serotonergic system originating in the DRC.

  3. Early Evidence of Low Bone Density and Decreased Serotonergic Synthesis in the Dorsal Raphe of a Tauopathy Model of Alzheimer’s Disease

    PubMed Central

    Dengler-Crish, Christine M.; Smith, Matthew A.; Wilson, Gina N.

    2016-01-01

    Reduced bone mineral density (BMD) and its clinical sequelae, osteoporosis, occur at a much greater rate in patients with Alzheimer’s disease (AD), often emerging early in the disease before significant cognitive decline is seen. Reduced BMD translates to increased bone fracture risk, decreased quality of life, and increased mortality for AD patients. However, the mechanism responsible for this observation is unclear. We hypothesize that bone loss is an additional component of an AD prodrome-changes that emerge prior to dementia and are mediated by dysfunction of the central serotonergic pathways. We characterized the skeletal phenotype of htau mice that express human forms of the microtubule-associated protein tau that become pathologically hyperphosphorylated in AD. Using radiographic densitometry, we measured BMD in female and male htau mice from 2–6 months of age–time-points prior to the presence of significant tauopathy in the hippocampal/entorhinal regions characteristic of this model. We found a significantly reduced BMD phenotype in htau mice that was most pronounced in males. Using western blotting and immunofluorescence, we showed overall reduced tryptophan hydroxylase (TPH) protein in htau brainstem and a 70% reduction in TPH-positive cells in the dorsal raphe nucleus (DRN)–a pivotal structure in the regulation of the adult skeleton. Elevations of hyperphosphorylated tau (ptau) proteins were also measured in brainstem, and co-labeled immunofluorescence studies showed presence of ptau in TPH-positive cells of the DRN as early as 4 months of age in htau mice. Together, these findings demonstrate that reduced BMD occurs earlier than overt degeneration in a tau-based AD model and that pathological changes in tau phosphorylation occur in the serotonin-producing neurons of the brainstem raphe in these mice. This illuminates a need to define a mechanistic relationship between bone loss and serotonergic deficits in early AD. PMID:27814296

  4. Olanzapine augments the effect of selective serotonin reuptake inhibitors by suppressing GABAergic inhibition via antagonism of 5-HT₆ receptors in the dorsal raphe nucleus.

    PubMed

    Asaoka, Nozomi; Nagayasu, Kazuki; Nishitani, Naoya; Yamashiro, Mayumi; Shirakawa, Hisashi; Nakagawa, Takayuki; Kaneko, Shuji

    2015-08-01

    The combination of the selective serotonin reuptake inhibitors (SSRIs) and atypical antipsychotic drugs shows better therapeutic efficacy than SSRI monotherapy in the treatment of depression. However, the underlying mechanisms responsible for the augmenting effects of olanzapine are not fully understood. Here, we report that olanzapine enhances the SSRI-induced increase in extracellular serotonin (5-HT) levels and antidepressant-like effects by inhibiting GABAergic neurons through 5-HT6 receptor antagonism in the dorsal raphe nucleus (DRN). In organotypic raphe slice cultures, treatment with olanzapine (1-100 μM) enhanced the increase in extracellular 5-HT levels in the presence of fluoxetine (10 μM) or citalopram (1 μM). The enhancing effect of olanzapine was not further augmented by the GABAA receptor antagonist bicuculline. Electrophysiological analysis revealed that olanzapine (50 μM) decreased the firing frequency of GABAergic neurons in acute DRN slices. Among many serotonergic agents, the 5-HT6 receptor antagonist SB399885 (1-100 μM) mimicked the effects of olanzapine by enhancing the SSRI-induced increase in extracellular 5-HT levels, which was not further augmented by bicuculline or olanzapine. SB399885 (50 μM) also decreased the firing frequency of GABAergic neurons in the DRN. In addition, an intraperitoneal administration of SB399885 (10 mg/kg) to mice significantly enhanced the antidepressant-like effect of a subeffective dose of citalopram (3 mg/kg) in the tail-suspension test. These results suggest that olanzapine decreases local inhibitory GABAergic tone in the DRN through antagonism of 5-HT6 receptors, thereby increasing the activity of at least part of serotonergic neurons, which may contribute to the augmentation of the efficacy of SSRIs.

  5. Dorsal raphe serotonin neurons in mice: immature hyperexcitability transitions to adult state during first three postnatal weeks suggesting sensitive period for environmental perturbation.

    PubMed

    Rood, Benjamin D; Calizo, Lyngine H; Piel, David; Spangler, Zachary P; Campbell, Kaitlin; Beck, Sheryl G

    2014-04-02

    Trauma during early life is a major risk factor for the development of anxiety disorders and suggests that the developing brain may be particularly sensitive to perturbation. Increased vulnerability most likely involves altering neural circuits involved in emotional regulation. The role of serotonin in emotional regulation is well established, but little is known about the postnatal development of the raphe where serotonin is made. Using whole-cell patch-clamp recording and immunohistochemistry, we tested whether serotonin circuitry in the dorsal and median raphe was functionally mature during the first 3 postnatal weeks in mice. Serotonin neurons at postnatal day 4 (P4) were hyperexcitable. The increased excitability was due to depolarized resting membrane potential, increased resistance, increased firing rate, lack of 5-HT1A autoreceptor response, and lack of GABA synaptic activity. Over the next 2 weeks, membrane resistance decreased and resting membrane potential hyperpolarized due in part to potassium current activation. The 5-HT1A autoreceptor-mediated inhibition did not develop until P21. The frequency of spontaneous inhibitory and excitatory events increased as neurons extended and refined their dendritic arbor. Serotonin colocalized with vGlut3 at P4 as in adulthood, suggesting enhanced release of glutamate alongside enhanced serotonin release. Because serotonin affects circuit development in other brain regions, altering the developmental trajectory of serotonin neuron excitability and release could have many downstream consequences. We conclude that serotonin neuron structure and function change substantially during the first 3 weeks of life during which external stressors could potentially alter circuit formation.

  6. Kinetics of platelet 5-hydroxytryptamine uptake in headache patients.

    PubMed

    Hannah, P; Jarman, J; Glover, V; Sandler, M; Davies, P T; Clifford Rose, F

    1991-07-01

    Platelet 5-hydroxytryptamine (5-HT) uptake was measured in asymptomatic headache patients attending a specialist migraine clinic, and in hospital staff who did not suffer from regular or severe headache. Current levels of anxiety and depression were assessed in all subjects using the Hospital Anxiety and Depression (HAD) scale and their possible influence on the uptake kinetics taken into account during the analysis of results. The Michaelis-Menten constant (Km) was significantly raised in common migraine and tension headache compared with controls (p less than 0.001 and p less than 0.01, respectively), but not in classical migraine or cluster headache. The increase remained significant after adjusting for differences in age, sex, presence of anxiety or depression (HAD sub-scale score greater than or equal to 8), drug intake during the week before testing, time elapsed since last attack and time of assay (am or pm). No differences were observed between patients and controls in the maximal rate of uptake (Vmax) or platelet count, and previous reports of a reduction in Vmax in patients experiencing attack within 5 days prior to testing could not be confirmed. The cause and significance of an increased Km are not clear, but plasma factors acting as competitive inhibitors for the uptake site or an alteration in the configuration of the uptake site are possible explanations. If confirmed, the shared biochemical abnormality may suggest that common migraine and tension headache have a common pathogenesis.

  7. 5-Hydroxytryptamine receptor in rabbit aorta: characterization by butyrophenone analogs.

    PubMed

    Maayani, S; Wilkinson, C W; Stollak, J S

    1984-05-01

    The contractile response of isolated rabbit aorta rings to 5-hydroxytryptamine (5-HT) was antagonized by spiperone and four other butyrophenone analogs in a competitive manner. The Kb values were (nanomolar):spiperone, 0.8; spirilene , 2.1; benperidol , 4.4; azaperone, 16.6; and haloperidol, 96.6. The Kd values for four of these drugs, whose affinities for [3H]ketanserin and [3H]spiperone binding sites in rat brain membranes have been measured, are almost indistinguishable from the Kb values in inhibiting 5-HT-induced contraction of the rabbit aorta. This suggests a congruence between the aortic "D" receptors and 5-HT2 type binding sites in rat brain. Among the drugs we tested, one portion of the molecule is almost identical; the other portion of the molecule differs in four of the five compounds. It is suggested that their rank order as antagonists of the 5-HT receptor in the aorta depends on the degree of recognition of the nonbutyrophenone part of the molecules by the receptor.

  8. Amantadin e tremor, a 5-hydroxytryptamine-mediated response?

    PubMed

    Cox, B; Tha, S J

    1975-02-01

    Amantadine-induced tremor has been investigated using mice. Experiments with, mebanazine, reserpine, diethyldithiocarbamate, and p-chlorophenylalanine suggest that the tremorgenic action of amantadine is influenced by a balance between three putative central nervous system (CNS) transmitters: noradrenaline, dopamine and 5-hydroxytryptamine (5-HT). Drugs which reduce the concentration of the catecholamines in brain increase amantadine induced tremor. p-Chlorophenylalanine, which specifically depletes brain 5-HT, antagonises amantadine-induced tremor. An ED50 (tremor) dose of amantadine decreases the concentration of 5-hydroxy-indoleacetic acid (5-HIAA) in rat brain, particularly when this elevated due to pretreatment with 5-hydroxytryptophan. Neither inhibition of monoamine oxidase nor reduction of 5-HT-reuptake appear to be responsible for this decrease. Experiments on rat fundus suggest that amantadine increased the sensitivity of receptors to 5-HT. A similar mechanism of action in the CNS could explain both the tremor and the decrease in brain 5-HIAA. The possible relevance of these findings is discussed with respect to the known anti-Parkinson action of amantadine.

  9. The interplay between brain 5-hydroxytryptamine levels and cocaine addiction.

    PubMed

    Nonkes, Lourens J P; van Bussel, Inge P G; Verheij, Michel M M; Homberg, Judith R

    2011-12-01

    Cocaine addiction is a major health problem that affects millions of people. Cocaine acts by inhibiting dopamine, noradrenaline and serotonin [5-hydroxytryptamine(5-HT)] reuptake. The dopaminergic system is generally assumed to be involved in the reinforcing aspects of the drug, but the role of 5-HT in the addictive potential of cocaine is unclear. In light of pharmacological manipulations and cocaine use-related disease states affecting brain 5-HT levels, we review studies on the effect of cocaine on central 5-HT function. In addition, the contribution of 5-HT to the rewarding, aversive, discriminative and subjective, as well as the motivational and reinforcing effects of cocaine is discussed. We specifically focus on net changes in the extracellular 5-HT levels that occur as a consequence of acute and chronic cocaine exposure and how these influence cocaine abuse-related behaviour. Overall, the data indicate that 5-HT plays a major role in the psychomotor stimulant, rewarding and discriminative stimulant effects of cocaine, but also affects the motivational and reinforcing effects of the drug. In addition, 5-HT mediates, to some extent, the aversive effects of cocaine. Difficulties with data interpretation are discussed.

  10. Effects of 5-hydroxytryptamine on canine isolated coronary arteries.

    PubMed Central

    Porquet, M. F.; Pourrias, B.; Santamaria, R.

    1982-01-01

    The effects of 5-hydroxytryptamine (5-HT) were studied in vitro on proximal and distal portions of canine interventricular and circumflex coronary arterial strips. 5-HT produced concentration-related contractions in the proximal portion whether contracted previously with KCl or not. These responses were still present after either chemical sympathetic denervation or release of noradrenaline induced by K+-free salt solution. In contrast, the distal portions of coronary arteries did not respond to 5-HT. Concentration-response curves to 5-HT exhibited a classical hyperbolic shape with a calculated Hill-coefficient of approximately 1. Methysergide and phentolamine but not morphine shifted to the right and depressed the maximum of the dose-response curves to 5-HT. It is concluded that the contractions produced by 5-HT in the proximal portion of the interventricular and circumflex coronary arteries are not due to the release of endogenous noradrenaline. The vessels appear to possess separate receptors for 5-HT and noradrenaline and the 5-HT responses belong to neither the M nor the D type. PMID:7186819

  11. The serotonin 5-HT7 receptor agonist LP-44 microinjected into the dorsal raphe nucleus suppresses REM sleep in the rat.

    PubMed

    Monti, Jaime M; Leopoldo, Marcello; Jantos, Héctor

    2008-08-22

    The effects of LP-44, a selective 5-HT7 receptor agonist, and of SB-269970, a selective 5-HT7 receptor antagonist, on spontaneous sleep were studied in adult rats implanted for chronic sleep recordings. The 5-HT7 receptor ligands were microinjected directly into the dorsal raphe nucleus (DRN) during the light period of the 12-h light/12-h dark cycle. Infusion of LP-44 (1.25-5.0 mM) into the DRN induced a significant reduction of rapid-eye-movement sleep (REMS) and of the number of REM periods. Similar effects were observed after the direct administration into the DRN of SB-269970 (0.5-1.0 mM). Pretreatment with a dose of SB-269970 (0.5 mM) that significantly affects sleep variables antagonized the LP-44 (2.5 mM)-induced suppression of REMS and of the number of REM periods. It is proposed that the suppression of REMS after microinjection of LP-44 into the DRN is related, at least in part, to the activation of GABAergic neurons in the DRN that contribute to long projections that reach, among others, the laterodorsal and pedunculopontine tegmental nuclei involved in the promotion of REMS.

  12. Brief pup exposure induces Fos expression in the lateral habenula and serotonergic caudal dorsal raphe nucleus of paternally experienced male California mice (Peromyscus californicus).

    PubMed

    de Jong, T R; Measor, K R; Chauke, M; Harris, B N; Saltzman, W

    2010-09-01

    Fathers play a substantial role in infant care in a small but significant number of mammalian species, including humans. However, the neural circuitry controlling paternal behavior is much less understood than its female counterpart. In order to characterize brain areas activated by paternal care, male California mice were separated from their female mate and litter for 3 h and then exposed to a pup or a control object (a glass pebble with the approximate size and oblong shape of a newborn pup) for 10 min. All males receiving a pup showed a strong paternal response towards it, whereas males receiving a pebble interacted with it only occasionally. Despite the clear behavioral differences, exposure to a pup did not increase Fos-like immunoreactivity (Fos-LIR) compared to a pebble in brain areas previously found to be associated with parental care, including the medial preoptic nucleus and medial bed nucleus of the stria terminalis. Pup exposure did, however, significantly increase Fos-LIR in the lateral habenula (LHb) and in predominantly serotonergic neurons in the caudal dorsal raphe nucleus (DRC), as compared to pebble exposure. Both the LHb and DRC are known to be involved in the behavioral responses to strong emotional stimuli; therefore, these areas might play a role in controlling parental behavior in male California mice.

  13. Role of dorsal raphe nucleus 5-HT(1A) and 5-HT(2) receptors in tonic immobility modulation in guinea pigs.

    PubMed

    Ferreira, Mateus Dalbem; Menescal-de-Oliveira, Leda

    2009-08-18

    Tonic immobility (TI) is an innate defensive behavior characterized by a state of physical inactivity and diminished responsiveness to environmental stimuli. Behavioral adaptations to changes in the external and internal milieu involve complex neuronal network activity and a large number of chemical neurotransmitters. The TI response is thought to be influenced by serotonin (5-HT) activity in the central nervous system (CNS) of vertebrates, but the neuronal groups involved in the mechanisms underlying this behavior are poorly understood. Owing to its extensive afferents and efferents, the dorsal raphe nucleus (DRN) has been implicated in a great variety of physiological and behavioral functions. In the current study, we investigated the influence of serotonergic 5-HT(1A) and 5-HT(2) receptor activity within the DRN on the modulation of TI behavior in the guinea pig. Microinjection of a 5-HT(1A) receptor agonist (8-OH-DPAT, 0.01 and 0.1 microg) decreased TI behavior, an effect blocked by pretreatment with WAY-100635 (0.033 microg), a 5-HT(1A) antagonist. In contrast, activation of 5-HT(2) receptors within the DRN (alpha-methyl-5-HT, 0.5 microg) increased the TI duration, and this effect could be reversed by pretreatment with an ineffective dose (0.01 microg) of ketanserine. Since the 5-HT(1A) and 5-HT(2) agonists decreased and increased, respectively, the duration of TI, different serotonin receptor subtypes may play distinct roles in the modulation of TI in the guinea pig.

  14. Serotonin levels in the dorsal raphe nuclei of both chipmunks and mice are enhanced by long photoperiod, but brain dopamine level response to photoperiod is species-specific.

    PubMed

    Goda, Ryosei; Otsuka, Tsuyoshi; Iwamoto, Ayaka; Kawai, Misato; Shibata, Satomi; Furuse, Mitsuhiro; Yasuo, Shinobu

    2015-04-23

    Seasonal affective disorder (SAD) is a subtype of major depressive or bipolar disorders associated with the shortened photoperiod in winter. This depressive disorder is integrally tied to the seasonal regulation of the brain's serotonergic system. Recently, we found that C57BL/6J mice subjected to a forced-swim test exhibited immobility, a photoperiod-dependent depression-associated behavior, and suppression of brain serotonin levels. However, mice are nocturnal animals, and it is unclear whether the brain serotonergic system responds similarly to photoperiod in nocturnal and diurnal species. This study compared the responses of brain serotonergic and dopaminergic systems to photoperiod in diurnal chipmunks and nocturnal C57BL/6J mice. In both species, serotonin levels in the dorsal raphe nuclei were higher under long-day conditions than short-day conditions, suggesting a similarity in the photoperiod responses of the serotonergic systems. However, photoperiod affected dopamine levels in various brain regions differently in the two species. Some chipmunk brain regions exhibited stronger photoperiod-induced changes in dopamine levels than those of C57BL/6J mice, and the direction of the changes in the hypothalamus was opposite. In conclusion, photoperiod may regulate the brain serotonergic system through similar mechanisms, regardless of whether the animals are diurnal or nocturnal, but photoperiod-dependent regulation of brain dopamine is species-specific.

  15. Single-prolonged stress activates the transcription factor ATF6α branch of the unfolded protein response in rat neurons of dorsal raphe nucleus.

    PubMed

    Xie, Juhua; Han, Fang; Shi, Yuxiu

    2015-01-01

    In our previous studies, we have found that endoplasmic reticulum (ER) stress is associated with post-traumatic stress disorder (PTSD), however, the activation of ER stress sensors in PTSD remains unclear. ATF6 alpha (ATF6α) is an ER-membrane-bound transcription factor and functions as a critical sensor and regulator of ER stress in mammalian cells. The goal of this study is to detect whether there is activation of the transcription factor ATF6α branch of the unfolded protein response in the dorsal raphe nucleus neurons of the rats exposed to single-prolonged stress (SPS), which is a model employed extensively in PTSD study. Our results have demonstrated that SPS activated the ER transmembrane protein ATF6α via its cleavage; and induced the up-regulation of the downstream targets of ATF6α, the mRNA of XBP1 and GRP94. To the best of our knowledge, this is the first study to investigate the relationship between the ATF6α pathways and PTSD, and our results show that SPS activates the ATF6α branch of the ER stress response, which may be contributed to the pathogenesis of PTSD.

  16. Chronic aluminum intoxication in rat induced both serotonin changes in the dorsal raphe nucleus and alteration of glycoprotein secretion in the subcommissural organ: Immunohistochemical study.

    PubMed

    Laabbar, Wafaa; Elgot, Abdeljalil; Kissani, Najib; Gamrani, Halima

    2014-08-08

    Aluminum (Al) causes multiple impairments in several body systems including the central nervous system. In fact, Al exposure has been mostly associated with neurological dysfunctions that occur in some brain diseases. The effect of Al neurotoxicity on the dopaminergic system is well documented, but this effect on the serotoninergic system is poorly studied. The aim of this work is to evaluate the effect of chronic Al intoxication (0.3% of aluminum chloride exposure from the intra-uterine age until 4 months of adult age) on dorsal raphe nucleus (DRN) which is the main source of serotonin, and also on the glycoprotein secretion of subcomissural organ (SCO), receiving important serotoninergic innervation. This will be executed using immunohistochemistry procedure, with both the anti serotonin and the anti Reissner's fiber antibodies in the rat. Our results showed a significant increase of serotonin immunoreactivity in the DRN, accompanied by a noticeable decrease of RF immunoreactivity in the SCO ependymocytes. This study provides further evidence confirming the toxic effect of Al exposure on serotonin neurotransmission in the brain likely through increased synthesis or decreased release. Al exposure was also shown to decrease RF glycoprotein which is involved in the detoxification of cerebrospinal fluid. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  17. Fear behavior and regional brain monoamines distribution after R(+)-8-OHDPAT and R(+)-UH-301 injections into the dorsal raphe nucleus in rats.

    PubMed

    Koprowska, Milena; Krotewicz, Maria; Romaniuk, Andrzej; Strzelczuk, Magdalena; Wieczorek, Marek

    2002-01-01

    The effects of 8-OHDPAT and UH-301 injection into the dorsal raphe nucleus (DRN) on fear behavior of the light-dark transitions test and regional brain monoamines (NA, DA, 5-HT) and their metabolites (MHPG, DOPAC, 5-HIAA) in the hypothalamus (HPT), midbrain central gray matter (MID), amygdala (AMY), hippocampus (HIP) and pons (PO) were examined. An injection of 8-OHDPAT (300 ng) as well UH-301 (300 ng) into the DRN evoked an increase in the number of head dipping from dark to the illuminated compartment of chamber, an increase of time of motionless in the dark compartment and decrease of time of locomotion activity in the illuminated compartment. HPLC analysis showed reduction of 5-HIAA/5-HT ratio in the HPT, HIP and PO, increase of MHPG/NA ratio in the HIP and PO, and increase of DA content in the HPT, AMY and HIP after 8-OHDPAT injection. But injection of UH-301 reduced 5-HT in the MID and increased in the AMY, reduced 5-HIAA content in the HIP and increased in the MID and decreased MHPG/NA ratio in the PO. These results indicate that both 5-HT1A receptor agonists, acting on the 5HT1A autoreceptors caused the anxiolytic effects, reduced fear behavior on the rat connected with infringement of dynamic balance between the serotonergic and catecholaminergics systems.

  18. Upregulation of the dorsal raphe nucleus-prefrontal cortex serotonin system by chronic treatment with escitalopram in hyposerotonergic Wistar-Kyoto rats.

    PubMed

    Yamada, Makiko; Kawahara, Yukie; Kaneko, Fumi; Kishikawa, Yuki; Sotogaku, Naoki; Poppinga, Wilfred J; Folgering, Joost H A; Dremencov, Eliyahu; Kawahara, Hiroshi; Nishi, Akinori

    2013-09-01

    Wistar-Kyoto (WKY) rats are sensitive to chronic stressors and exhibit depression-like behavior. Dorsal raphe nucleus (DRN) serotonin (5-HT) neurons projecting to the prefrontal cortex (PFC) comprise the important neurocircuitry underlying the pathophysiology of depression. To evaluate the DRN-PFC 5-HT system in WKY rats, we examined the effects of escitalopram (ESCIT) on the extracellular 5-HT level in comparison with Wistar rats using dual-probe microdialysis. The basal levels of 5-HT in the DRN, but not in the PFC, in WKY rats was reduced as low as 30% of Wistar rats. Responses of 5-HT in the DRN and PFC to ESCIT administered systemically and locally were attenuated in WKY rats. Feedback inhibition of DRN 5-HT release induced by ESCIT into the PFC was also attenuated in WKY rats. Chronic ESCIT induced upregulation of the DRN-PFC 5-HT system in WKY rats, with increases in basal 5-HT in the DRN, responsiveness to ESCIT in the DRN and PFC, and feedback inhibition, whereas downregulation of these effects was induced in Wistar rats. Thus, the WKY rat is an animal model of depression with low activity of the DRN-PFC 5HT system. The finding that chronic ESCIT upregulates the 5-HT system in hyposerotonergic WKY rats may contribute to improved understanding of mechanisms of action of antidepressants, especially in depression with 5-HT deficiency. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Mirtazapine exerts an anxiolytic-like effect through activation of the median raphe nucleus-dorsal hippocampal 5-HT pathway in contextual fear conditioning in rats.

    PubMed

    An, Yan; Chen, Chong; Inoue, Takeshi; Nakagawa, Shin; Kitaichi, Yuji; Wang, Ce; Izumi, Takeshi; Kusumi, Ichiro

    2016-10-03

    The functional role of serotonergic projections from the median raphe nucleus (MRN) to the dorsal hippocampus (DH) in anxiety remains understood poorly. The purpose of the present research was to examine the functional role of this pathway, using the contextual fear conditioning (CFC) model of anxiety. We show that intra-MRN microinjection of mirtazapine, a noradrenergic and specific serotonergic antidepressant, reduced freezing in CFC without affecting general motor activity dose-dependently, suggesting an anxiolytic-like effect. In addition, intra-MRN microinjection of mirtazapine dose-dependently increased extracellular concentrations of serotonin (5-HT) but not dopamine in the DH. Importantly, intra-DH pre-microinjection of WAY-100635, a 5-HT1A antagonist, significantly attenuated the effect of mirtazapine on freezing. These results, for the first time, suggest that activation of the MRN-DH 5-HT1A pathway exerts an anxiolytic-like effect in CFC. This is consistent with the literature that the hippocampus is essential for retrieval of contextual memory and that 5-HT1A receptor activation in the hippocampus primarily exerts an inhibitory effect on the neuronal activity. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Somatosensory regulation of serotonin release in the central nucleus of the amygdala is mediated via corticotropin releasing factor and gamma-aminobutyric acid in the dorsal raphe nucleus.

    PubMed

    Tokunaga, Ryota; Shimoju, Rie; Shibata, Hideshi; Kurosawa, Mieko

    2016-10-15

    Noxious cutaneous stimulation increases, whereas innocuous cutaneous stimulation decreases serotonin (5-HT) release in the central nucleus of the amygdala (CeA) in anesthetized rats. In the present study, we investigated the contribution of corticotropin releasing factor (CRF) receptors and gamma-aminobutyric acid (GABA) receptors in the dorsal raphe nucleus (DRN) to those responses. Release of 5-HT in the CeA was monitored by microdialysis before and after 10-min stimulation by pinching or stroking. Increased 5-HT release in the CeA in response to pinching was abolished by CRF2 receptor antagonism in the DRN. Decreased 5-HT release in the CeA in response to stroking was abolished by either CRF1 receptor antagonism or GABAA receptor antagonism in the DRN. These results suggest that opposite responses of 5-HT release in the CeA to noxious versus innocuous stimulation of the skin are due to separate contributions of CRF2, CRF1 and GABAA receptors in the DRN.

  1. The vigilance promoting drug modafinil modulates serotonin transmission in the rat prefrontal cortex and dorsal raphe nucleus. Possible relevance for its postulated antidepressant activity.

    PubMed

    Ferraro, Luca; Antonelli, Tiziana; Beggiato, Sarah; Cristina Tomasini, Maria; Fuxe, Kjell; Tanganelli, Sergio

    2013-04-01

    Modafinil, (RS)-2-(diphenylmethylsulfinyl)acetamide derivative (Modiodal, Provigil), is a vigilance-promoting agent which reduces sleep episodes by improving wakefulness. It is approved by the USA FDA for narcolepsy, shiftwork sleep disorder and obstructive sleep apnoea with residual excessive sleepiness despite optimal use of continuous positive airway pressure. Unlike classical psychostimulants such as amphetamine and amphetamine-like compounds, the awaking effect of modafinil is not associated with a disturbance of nighttime sleep, tolerance, and sensitization. Its precise mechanism of action is still unclear. In animal studies, modafinil and its analogues have been shown to modify dopaminergic, noradrenergic, glutamatergic, GABAergic, serotoninergic, orexinergic, and histaminergic pathways. Besides the approved use in sleep disorders, modafinil has been investigated for the treatment of fatigue, impaired cognition and some symptoms in a number of other disorders. In particular, clinical studies seem to indicate that the drug could be particularly successful in the treatment of depression and its use in major depressive and bipolar disorders, has been suggested. However, the molecular mechanisms underlying this possible effect are still unknown. The present review firstly summarizes the structure-activity relationship studies and the mechanism of action of modafinil and its related compounds. Then, it focuses on data demonstrating that modafinil interacts with serotonin neuronal activity in rat frontal cortex and dorsal raphe nucleus, two brain areas linked together and involved in depression. Preclinical and clinical evidence of a positive interaction between modafinil and classical antidepressant drugs, is also summarized.

  2. Attenuation of hyperalgesia responses via the modulation of 5-hydroxytryptamine signalings in the rostral ventromedial medulla and spinal cord in a 6-hydroxydopamine-induced rat model of Parkinson’s disease

    PubMed Central

    Wang, Chen-Tao; Mao, Cheng-Jie; Zhang, Xiao-Qi; Zhang, Cai-Yi; Lv, Dong-Jun; Yang, Ya-Ping; Xia, Kai-Lin; Liu, Jun-Yi; Wang, Fen; Hu, Li-Fang; Xu, Guang-Yin

    2017-01-01

    Background Although pain is one of the most distressing non-motor symptoms among patients with Parkinson’s disease, the underlying mechanisms of pain in Parkinson’s disease remain elusive. The aim of the present study was to investigate the role of serotonin (5-hydroxytryptamine) in the rostral ventromedial medulla (RVM) and spinal cord in pain sensory abnormalities in a 6-hydroxydopamine-treated rat model of Parkinson’s disease. Methods The rotarod test was used to evaluate motor function. The radiant heat test and von Frey test were conducted to evaluate thermal and mechanical pain thresholds, respectively. Immunofluorescence was used to examine 5-hydroxytryptamine neurons and fibers in the rostral ventromedial medulla and spinal cord. High-performance liquid chromatography was used to determine 5-hydroxytryptamine and 5-hydroxyindoleacetic acid levels. Results The duration of running time on the rotarod test was significantly reduced in 6-hydroxydopamine-treated rats. Nociceptive thresholds of both mechanical and heat pain were reduced compared to sham-treated rats. In addition to the degeneration of cell bodies and fibers in the substantia nigra pars compacta, the number of rostral ventromedial medulla 5-hydroxytryptamine neurons and 5-hydroxytryptamine fibers in the spinal dorsal horn was dramatically decreased. 5-Hydroxytryptamine concentrations in both the rostral ventromedial medulla and spinal cord were reduced. Furthermore, the administration of citalopram significantly attenuated pain hypersensitivity. Interestingly, Intra-rostral ventromedial medulla (intra-RVM) microinjection of 5,7-dihydroxytryptamine partially reversed pain hypersensitivity of 6-hydroxydopamine-treated rats. Conclusions These results suggest that the decreased 5-hydroxytryptamine contents in the rostral ventromedial medulla and spinal dorsal horn may be involved in hyperalgesia in the 6-hydroxydopamine-induced rat model of Parkinson’s disease. PMID:28326933

  3. Nerve terminal effects of indoleamine psychotomimetics on 5-hydroxytryptamine.

    PubMed

    Halaris, A E

    1982-01-01

    The mode of action of indoleamine psychotomimetics has been closely linked to 5-HT. Early work showed increases in rat brain levels of 5-HT which were later localized to the nerve-ending fraction. With improved methodology, the 5-HT increment was further detected in the synaptic vesicle fraction. These effects were obtained with several indoleamine hallucinogens but not with mescaline. LSD has been most thoroughly studied and has served as the prototypical compound in ascertaining the mode of action of these drugs. Pretreatment with reserpine abolished the 5-HT effects of LSD in the vesicular fraction. However, a new compartment, termed "juxtavesicular," displayed 5-HT increases following reserpine and LSD. A soluble binding site for 5-HT within the synaptoplasm has been postulated in confirmation of independent results by other groups of investigators. The origin of the 5-HT increment appears to be associated with newly synthesized amine. This was deduced from experiments involving various 5-HT synthesis blockers. To ascertain whether inhibition of raphé neuronal firing is responsible for the accumulation of 5-HT at the nerve terminal, two sets of experiments were performed. Destruction of the raphé cell bodies by radiofrequency lesions failed to abolish the LSD-induced 5-HT increase early after the lesion. Destruction of cortical 5-HT neurons with the neurotoxin 5,7-dihydroxytryptamine completely abolished the 5-HT effect of LSD. It was concluded that an intact nerve terminal is necessary for the expression of the LSD-mediated increases in 5-HT. A LSD "autoreceptor" is postulated, possibly identical to a 5-HT presynaptic receptor inhibiting the release of 5-HT.

  4. 5-Hydroxytryptamine-induced tachycardia in the pig: possible involvement of a new type of 5-hydroxytryptamine receptor.

    PubMed Central

    Bom, A. H.; Duncker, D. J.; Saxena, P. R.; Verdouw, P. D.

    1988-01-01

    1. The mechanism of 5-hydroxytryptamine (5-HT)-induced tachycardia is species-dependent and is mediated directly or indirectly either by '5-HT1-like' (cat), 5-HT2 (rat, dog) or 5-HT3 (rabbit) receptors, or by an action similar to tyramine (guinea-pig). The present investigation is devoted to the analysis of the positive chronotropic effect of 5-HT in the pentobarbitone-anaesthetized pig. 2. Intravenous bolus injections of 5-HT (3, 10 and 30 micrograms kg-1) in pigs resulted in dose-dependent increases in heart rate of 24 +/- 2, 38 +/- 3 and 51 +/- 3 beats min-1, respectively (n = 39). Topical application of a high concentration of 5-HT (150 micrograms kg-1 in 5 ml) on the right atrium was also followed by tachycardia (38 +/- 6 beats min-1, n = 4). 3. A number of drugs which antagonize responses mediated by different 5-HT receptors--phenoxybenzamine, methiothepin, metergoline, methysergide and mesulergine ('5-HT1-like' and 5-HT2 receptors), ketanserin, cyproheptadine, pizotifen and mianserin (5-HT2 receptors), and MDL 72222 and ICS 205-930 (5-HT3 receptors)--did not attenuate the chronotropic responses to 5-HT. 4. The 5-HT-induced tachycardia was also not affected by antagonists at alpha- and beta-adrenoceptors, muscarinic, nicotinic, histamine and dopamine receptors, and calcium channels. 5. Selective inhibitors of 5-HT-uptake, indalpine and fluvoxamine, themselves increased porcine heart rate and facilitated 5-HT-induced tachycardia both in magnitude and in duration.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3370393

  5. Interaction between tricyclic and nontricyclic 5-hydroxytryptamine uptake inhibitors and the presynaptic 5-hydroxytryptamine inhibitory autoreceptors in the rat hypothalamus.

    PubMed

    Galzin, A M; Moret, C; Verzier, B; Langer, S Z

    1985-10-01

    In slices of the rat hypothalamus prelabeled with [3H]-5-hydroxytryptamine [( 3H]-5-HT), exposure to lysergic acid diethylamide or 5-methoxytryptamine decreased, in a concentration-dependent manner, the release of 3H-transmitter elicited by electrical stimulation. These inhibitory effects were antagonized by the 5-HT receptor antagonist methiothepin (1 microM). Exposure to methiothepin on its own increased in a concentration-dependent manner the electrically evoked overflow of [3H]-5-HT. Exposure to tricyclic antidepressants, like imipramine and amitriptyline, and to nontricyclic 5-HT uptake inhibitors, like paroxetine and citalopram, did not modify by themselves the electrically evoked overflow of [3H]-5-HT. Yet, the four inhibitors of neuronal uptake of 5-HT, antagonized the inhibition by lysergic acid diethylamide or 5-methoxytryptamine of the electrically induced release of [3H]-5-HT. After depletion of endogenous stores of 5-HT by pretreatment with para-chlorophenylalanine (300 mg/kg i.p.), the inhibitors of 5-HT uptake increased the electrically evoked release of [3H]-5-HT in a concentration-dependent manner. Their order of potency to enhance 5-HT overflow after pretreatment with parachlorophenylalanine paralleled their potency at inhibiting neuronal uptake of 5-HT (paroxetine = citalopram greater than imipramine greater than amitriptyline). In para-chlorophenylalanine-treated rat hypothalamic slices, these inhibitors of 5-HT uptake antagonized the inhibition by 5-HT autoreceptor agonists of the electrically evoked release of [3H]-5-HT to a similar extent than was observed in control rats. It is concluded that inhibition of 5-HT uptake reduces the effectiveness of 5-HT autoreceptor agonists to inhibit the electrically evoked release of [3H]-5-HT, irrespective of the chemical structure of the uptake inhibitor or of the levels of endogenous 5-HT achieved in the synaptic gap.

  6. 5-hydroxytryptamine induced relaxation in the pig urinary bladder neck

    PubMed Central

    Recio, Paz; Barahona, María Victoria; Orensanz, Luis M; Bustamante, Salvador; Martínez, Ana Cristina; Benedito, Sara; García-Sacristán, Albino; Prieto, Dolores; Hernández, Medardo

    2009-01-01

    Background and purpose 5-Hydroxytryptamine (5-HT) is one of the inhibitory mediators in the urinary bladder outlet region. Here we investigated mechanisms involved in 5-HT-induced relaxations of the pig bladder neck. Experimental approach Urothelium-denuded strips of pig bladder were mounted in organ baths for isometric force recordings of responses to 5-HT and electrical field stimulation (EFS). Key results After phenylephrine-induced contraction, 5-HT and 5-HT receptor agonists concentration-dependently relaxed the preparations, with the potency order: 5-carboxamidotryptamine (5-CT) > 5-HT = RS67333 > (±)-8-hydroxy-2-dipropylaminotetralinhydrobromide > m-chlorophenylbiguanide > α-methyl-5-HT > ergotamine. 5-HT and 5-CT relaxations were reduced by the 5-HT7 receptor antagonist (2R)-1-[(3-hydroxyphenyl)sulphonyl]-2-[2-(4-methyl-1-piperidinyl)ethyl]pyrrolidine hydrochloride and potentiated by (S)-N-tert-butyl-3-(4-(2-methoxyphenyl)-piperazin-1-yl)-2-phenylpropanamide dihydrochloride (WAY 100135) and cyanopindolol, 5-HT1A and 5-HT1A/1B receptor antagonists respectively. Inhibitors of 5-HT1B/1D, 5-HT2, 5-HT2B/2C, 5-HT3, 5-HT4, 5-HT5A and 5-HT6 receptors failed to modify 5-HT responses. Blockade of monoamine oxidase A/B, noradrenergic neurotransmission, α-adrenoceptors, muscarinic and purinergic receptors, nitric oxide synthase, guanylate cyclase and prostanoid synthesis did not alter relaxations to 5-HT. Inhibitors of Ca2+-activated K+ and ATP-dependent K+ channels failed to modify 5-HT responses but blockade of neuronal voltage-gated Na+-, Ca2+-and voltage-gated K+ (Kv)-channels potentiated these relaxations. Adenylyl cyclase activation and cAMP-dependent protein kinase (PKA) inhibition potentiated and reduced, respectively, 5-HT-induced responses. Under non-adrenergic, non-cholinergic, non-nitrergic conditions, EFS induced neurogenic, frequency-dependent, relaxations which were resistant to WAY 100135 and cyanopindolol. Conclusions and implications 5-HT relaxed

  7. 5-hydroxytryptamine2C receptor activation inhibits 5-hydroxytryptamine1B-like receptor function via arachidonic acid metabolism.

    PubMed

    Berg, K A; Maayani, S; Clarke, W P

    1996-10-01

    We previously reported that in Chinese hamster ovary (CHO) cells, 5-hydroxytryptamine (5-HT)1B-like (CHO/5-HT1B) receptor-mediated inhibition of forskolin-stimulated cAMP accumulation is inhibited by activation of transfected human 5-HT2C receptors but not 5-HT2A receptors. In the current study, we investigated the mechanism involved in the regulation of receptor-mediated inhibition of adenylyl cyclase as a means to further elucidate differences between the signal transduction cascades of the 5-HT2A and 5-HT2C receptor subtypes. Activation of 5-HT2C receptors with 5-HT or (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane increased release of arachidonic acid via a phospholipase A2 (PLA2)-dependent mechanism. Incubation with (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (1 microM) abolished 5-carboxamidotryptamine (5 nM)-mediated inhibition of forskolin-stimulated cAMP accumulation, which was blocked by the PLA2 inhibitor mepacrine (100 microM) and the cyclooxygenase inhibitor indomethacin (2 microM). Furthermore, purinergic receptor-mediated PLA2 activation as well as direct activation of PLA2 with melittin reduced CHO/5-HT1B responsiveness. These data indicate that activation of the PLA2/arachidonic acid signaling cascade mediates 5-HT2C receptor regulation of the CHO/5-HT1B receptor pathway. Consistent with our previous report and in contrast to activation of 5-HT2C or purinergic receptors, activation of 5-HT2A receptors had no effect on CHO/5-HT1B receptor function, although 5-HT2A receptor-mediated activation of PLA2 was measured. Interestingly, purinergic receptor-mediated inhibition of CHO/5-HT1B receptor function was blocked when 5-HT2A receptors were activated simultaneously. These data suggest that the lack of 5-HT2A mediated regulation of CHO/5-HT1B receptors may be due to activation of a third pathway (in addition to PLC and PLA2 pathways), which results in the inhibition of the production or the actions of a cyclooxygenase-dependent arachidonic

  8. Effect of α-alkylated tryptamine derivatives on 5-hydroxytryptamine metabolism in vivo

    PubMed Central

    Gey, K. F.; Pletscher, A.

    1962-01-01

    In rats, three α-alkylated tryptamine derivatives (α-methyl, α-ethyl, and αα-dimethyltryptamine) caused alterations of 5-hydroxytryptamine metabolism typical of monoamine-oxidase inhibitors with short duration of action, viz., an increase of endogenous 5-hydroxytryptamine in brain, enhancement of the increase of 5-hydroxytryptamine in brain and heart after 5-hydroxytryptophan administration, an inhibition of the decrease in 5-hydroxytryptamine in brain induced by a benzoquinolizine derivative and of the increase induced by iproniazid. The increase after iproniazid was antagonized to the same extent by all the tryptamine derivatives and by harmaline, whereas dexamphetamine showed less effect. In the other experiments with brain, the tryptamine derivatives were less potent than harmaline, but somewhat more active than dexamphetamine. α-Methyltryptamine and α-ethyltryptamine were relatively more effective in the heart than in the brain. Among the tryptamine derivatives αα-dimethyltryptamine had the weakest activity in brain and in heart. PMID:13898151

  9. Receptor reserve for 5-hydroxytryptamine1A-mediated inhibition of serotonin synthesis: possible relationship to anxiolytic properties of 5-hydroxytryptamine1A agonists.

    PubMed

    Meller, E; Goldstein, M; Bohmaker, K

    1990-02-01

    The irreversible receptor antagonist N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) was used to determine the relationship between receptor occupancy and response at central 5-hydroxytryptamine1A (5-HT1A) serotonin receptors mediating the inhibition of serotonin synthesis in rat cortex and hippocampus. Rats were treated with vehicle or EEDQ (2 or 6 mg/kg) and 24 hr later dose-response curves were constructed for inhibition of 5-hydroxytrytophan (5-HTP) accumulation (after decarboxylase inhibition with NSD-1015) by the selective 5-HT1A agonists 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT) (0.01-3 mg/kg), buspirone (0.1-7.5 mg/kg), and ipsapirone (0.1-6.25 mg/kg) and the 5-HT1A agonist/antagonist BMY 7378 (0.015-5 mg/kg). In vehicle-pretreated rats, a similar maximal inhibition of 5-HT synthesis (range, 52-59%) was observed in both brain areas with 8-OH-DPAT, buspirone, and ipsapirone. These three agonists were also more potent in reducing 5-HTP accumulation in the cortex than in the hippocampus (ED50, 8-OH-DPAT, 14 and 30 microgram/kg; buspirone, 0.42 and 0.63 mg/kg; ipsapirone, 0.44 and 1.26 mg/kg, respectively). In the cortex, EEDQ treatment shifted the dose-response curves for 8-OH-DPAT, buspirone, and ipsapirone 8.6-, 2.0-, and 2.8-fold to the right, respectively. Corresponding rightward shifts in the hippocampus were smaller, 6.0-, 1.6-, and 2.1-fold, respectively. The EEDQ-induced shifts in the dose-response curves were accompanied by reductions in maximal response. In contrast, whereas the maximal inhibition of cortical 5-HTP accumulation by BMY 7378 (55%) was similar to that obtained with the agonists, maximal response in the hippocampus was much smaller (32%). Furthermore, in both brain regions EEDQ reduced the maximal response to BMY 7378 without shifting the dose-response curves. Analysis of the data by the double-reciprocal method of Furchgott, followed by calculation of fractional receptor occupancy for each dose of agonist, revealed a

  10. Effects of standardized extracts of St. John's wort on the single-unit activity of serotonergic dorsal Raphe neurons in awake cats: comparisons with fluoxetine and sertraline.

    PubMed

    Fornal, C A; Metzler, C W; Mirescu, C; Stein, S K; Jacobs, B L

    2001-12-01

    St. John's wort is widely used as an herbal remedy for depression. Although its mechanism of action remains unknown, some evidence suggests that St. John's wort might act via brain serotonin (e.g., as a serotonin reuptake inhibitor). To determine whether St. John's wort affects the central serotonergic system, we monitored the discharge rate of serotonin-containing neurons in the dorsal raphe nucleus of awake cats following systemic administration of two clinical preparations of St. John's wort, Jarsin 300 (15-600 mg/kg, p.o.) and Hyperforat (0.5-4.0 ml, i.v.). Both preparations were found to have no effect on neuronal activity. This contrasts sharply with the action of fluoxetine and sertraline (2 mg/kg, p.o.), two selective serotonin reuptake inhibitors (SSRIs), which markedly depressed neuronal activity by increasing the synaptic availability of serotonin at inhibitory somatodendritic 5-HT(1A) autoreceptors. The failure of St. John's wort to depress neuronal activity cannot be attributed to an impairment of the 5-HT(1A) autoreceptor mechanism, since pretreatment with Jarsin 300 (300 mg/kg, p.o.) did not alter the responsiveness of serotonergic neurons to the 5-HT(1A) agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (10 microg/kg, i.v.). Overall, these findings indicate that the mode of action of St. John's wort is different from that of conventional antidepressant drugs, which elevate brain serotonin and evoke negative feedback control of serotonergic neurons.

  11. Serotonergic neural links from the dorsal raphe nucleus modulate defensive behaviours organised by the dorsomedial hypothalamus and the elaboration of fear-induced antinociception via locus coeruleus pathways.

    PubMed

    Biagioni, Audrey Francisco; de Freitas, Renato Leonardo; da Silva, Juliana Almeida; de Oliveira, Rithiele Cristina; de Oliveira, Ricardo; Alves, Vani Maria; Coimbra, Norberto Cysne

    2013-04-01

    Decrease of γ-aminobutyric acid (GABA)-mediated neurotransmission in the dorsomedial hypothalamus (DMH) evokes instinctive fear-like responses. The aim of the present study was to investigate the involvement of the serotonin (5-HT)- and norepinephrine-mediated pathways of the endogenous pain inhibitory system, including the dorsal raphe nucleus (DRN) and the locus coeruleus (LC), in the defensive responses and antinociceptive processes triggered by the blockade of GABAergic receptors in the DMH. The intra-hypothalamic microinjection of the GABA(A) receptor antagonist bicuculline (40 ng/200 nL) elicited elaborate defensive behaviours interspersed with exploratory responses. This escape behaviour was followed by significantly increased pain thresholds, a phenomenon known as fear-induced antinociception. Furthermore, at 5 and 14 days after DRN serotonin-containing neurons were damaged using the selective neurotoxin 5,7-dihydroxytryptamine (5,7-DHT), the frequency and duration of alertness and escape behaviour evoked by the GABA(A) receptor blockade in the DMH decreased, as well as fear-induced antinociception. Pre-treatment with the non-selective 5-HT receptor antagonist methysergide, the 5-HT(2A/2C) receptor antagonist ketanserin and the 5-HT(2A) receptor selective antagonist R-96544 in the LC also decreased fear-induced antinociception, without significant changes in the expression of defensive behaviours. These data suggest that the serotonergic neurons of the DRN are directly involved in the organisation of defensive responses as well as in the elaboration of the innate fear-induced antinociception. However, serotonin-mediated inputs from the NDR to the LC modulate only fear-induced antinociception and not the defensive behaviours evoked by GABA(A) receptor blockade in the DMH. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Effects of chemical stimulation of the lateral wings of the dorsal raphe nucleus on panic-like defensive behaviors and Fos protein expression in rats.

    PubMed

    Matthiesen, Melina; Spiacci, Ailton; Zangrossi, Hélio

    2017-03-06

    The lateral wings subnucleus of the dorsal raphe nucleus (lwDR) has been implicated in the modulation of panic-like behaviors, such as escape. Infusion of non- excitotoxic doses of the excitatory amino acid kainic acid into this subnucleus promptly evokes a vigorous escape response. In addition, rats exposed to panic-inducing situations show an increase in Fos protein expression in neurons within the lwDR. In the present study, we first investigated whether key structures associated with the mediation of escape behavior are recruited after chemical stimulation of the lwDR with kainic acid. We next investigated whether the infusion of the GABAA receptor antagonist bicuculline into the lwDR also evoked escape responses measured both in a circular arena and in the rat elevated T-maze. The effects of bicuculline in the circular arena were compared to those caused by the infusion of this antagonist into the ventrolateral periaqueductal gray (vlPAG), an area in close vicinity to the lwDR. The results showed that kainic acid infusion into the lwDR increased Fos protein immunostaining in brain structures deeply involved in panic-like defensive behaviors, such as the periaqueductal gray and hypothalamus, but not the amygdala. As observed with kainic acid, bicuculline evoked a pronounced escape response in the circular arena when microinjected in the lwDR, but not in the vlPAG. The escape-promoting effect of bicuculline in the lwDR was also evidenced in the elevated T-maze. These findings strength the view that dysfunction in mechanisms controlling escape in the lwDR is critically implicated in the pathophysiology of panic disorder.

  13. Glucocorticoid receptor deletion from the dorsal raphé nucleus of mice reduces dysphoria-like behavior and impairs hypothalamic-pituitary-adrenocortical axis feedback inhibition.

    PubMed

    Vincent, Melanie Y; Jacobson, Lauren

    2014-05-01

    Glucocorticoids can cause depression and anxiety. Mechanisms for glucocorticoid effects on mood are largely undefined. The dorsal raphé nucleus (DRN) produces the majority of serotonin in the brain, and expresses glucocorticoid receptors (GR). Because we previously showed that antidepressants used to treat depression and anxiety decrease DRN GR expression, we hypothesized that deleting DRN GR would have anxiolytic- and antidepressant-like effects. We also hypothesized that DRN GR deletion would disinhibit activity of the hypothalamic-pituitary-adrenal (HPA) axis. Adeno-associated virus pseudotype AAV2/9 expressing either Cre recombinase (DRNGRKO mice) or GFP (DRN-GFP mice) was injected into the DRN of floxed GR mice to test these hypotheses. Three weeks after injection, mice underwent 21 days of social defeat or control handling and were tested for anxiety-like behavior (open-field test, elevated-plus maze), depression-like behavior [sucrose preference, forced-swim test (FST), tail-suspension test (TST)], social interaction, and circadian and stress-induced HPA activity. DRN GR deletion decreased anxiety-like behavior in control but not in defeated mice. DRN GR deletion decreased FST and tended to decrease TST despair-like behavior in both control and defeated mice, but did not affect sucrose preference. Exploration of social (a novel mouse) as well as neutral (an empty box) targets was increased in DRNGRKO mice, suggesting that DRN GR deletion also promotes active coping. DRN GR deletion increased stress-induced HPA activity without strongly altering circadian HPA activity. We have shown a novel role for DRN GR to mediate anxiety- and despair-like behavior and to regulate HPA negative feedback during acute stress.

  14. Prenatal expression of MET receptor tyrosine kinase in the fetal mouse dorsal raphe nuclei and the visceral motor/sensory brainstem.

    PubMed

    Wu, Hsiao-Huei; Levitt, Pat

    2013-01-01

    Signaling via MET receptor tyrosine kinase (MET) has been implicated in a number of neurodevelopmental events, including cell migration, dendritic and axonal development and synaptogenesis. Related to its role in the development of forebrain circuitry, we recently identified a functional promoter variant of the MET gene that is associated with autism spectrum disorder (ASD). The association of the MET promoter variant rs1858830 C allele is significantly enriched in families with a child who has ASD and co-occurring gastrointestinal conditions. The expression of MET in the forebrain had been mapped in detail in the developing mouse and rhesus macaque. However, in mammals, its expression in the developing brainstem has not been studied extensively throughout developmental stages. Brainstem and autonomic circuitry are implicated in ASD pathophysiology and in gastrointestinal dysfunction. To advance our understanding of the neurodevelopmental influences of MET signaling in brainstem circuitry development, we employed in situ hybridization and immunohistochemistry to map the expression of Met and its ligand, Hgf, through prenatal development of the mouse midbrain and hindbrain. Our results reveal a highly selective expression pattern of Met in the brainstem, including a subpopulation of neurons in cranial motor nuclei (nVII, nA and nXII), B6 subgroup of the dorsal raphe, Barrington's nucleus, and a small subset of neurons in the nucleus of solitary tract. In contrast to Met, neither full-length nor known splice variants of Hgf were localized in the prenatal brainstem. RT-PCR revealed Hgf expression in target tissues of Met-expressing brainstem neurons, suggesting that MET in these neurons may be activated by HGF from peripheral sources. Together, these data suggest that MET signaling may influence the development of neurons that are involved in central regulation of gastrointestinal function, tongue movement, swallowing, speech, stress and mood.

  15. Corticotropin-releasing Factor in the Rat Dorsal Raphe Nucleus Promotes Different Forms of Behavioral Flexibility Depending on Social Stress History

    PubMed Central

    Snyder, Kevin P; Hill-Smith, Tiffany E; Lucki, Irwin; Valentino, Rita J

    2015-01-01

    The stress-related neuropeptide, corticotropin-releasing factor (CRF) regulates the dorsal raphe nucleus–serotonin (DRN–5-HT) system during stress and this may underlie affective and cognitive dysfunctions that characterize stress-related psychiatric disorders. CRF acts on both CRF1 and CRF2 receptor subtypes in the DRN that exert opposing inhibitory and excitatory effects on DRN-5-HT neuronal activity and 5-HT forebrain release, respectively. The current study first assessed the cognitive effects of intra-DRN microinfusion of CRF or the selective CRF2 agonist, urocortin II in stress-naive rats on performance of an operant strategy set-shifting task that is mediated by the medial prefrontal cortex (mPFC). CRF (30 ng) facilitated strategy set-shifting performance, whereas higher doses of CRF and urocortin II that would interact with CRF2 were without effect, consistent with a CRF1-mediated action. This dose decreased 5-HT extracellular levels in the mPFC, further supporting a role for CRF1. The effects of CRF were then assessed in rats exposed to repeated social stress using the resident–intruder model. Repeated social stress shifted the CRF effect from facilitation of strategy set shifting to facilitation of reversal learning and this was most prominent in a subpopulation of rats that resist defeat. Notably, in this subpopulation of rats 5-HT neuronal responses to CRF have been demonstrated to shift from CRF1-mediated inhibition to CRF2-mediated excitation. Because 5-HT facilitates reversal learning, the present results suggest that stress-induced changes in the cellular effects of CRF in the DRN translate to changes in cognitive effects of CRF. Together, the results underscore the potential for stress history to shift cognitive processing through changes in CRF neurotransmission in the DRN and the association of this effect with coping strategy. PMID:25865931

  16. Markers of Serotonergic Function in the Orbitofrontal Cortex and Dorsal Raphé Nucleus Predict Individual Variation in Spatial-Discrimination Serial Reversal Learning

    PubMed Central

    Barlow, Rebecca L; Alsiö, Johan; Jupp, Bianca; Rabinovich, Rebecca; Shrestha, Saurav; Roberts, Angela C; Robbins, Trevor W; Dalley, Jeffrey W

    2015-01-01

    Dysfunction of the orbitofrontal cortex (OFC) impairs the ability of individuals to flexibly adapt behavior to changing stimulus-reward (S-R) contingencies. Impaired flexibility also results from interventions that alter serotonin (5-HT) and dopamine (DA) transmission in the OFC and dorsomedial striatum (DMS). However, it is unclear whether similar mechanisms underpin naturally occurring variations in behavioral flexibility. In the present study, we used a spatial-discrimination serial reversal procedure to investigate interindividual variability in behavioral flexibility in rats. We show that flexibility on this task is improved following systemic administration of the 5-HT reuptake inhibitor citalopram and by low doses of the DA reuptake inhibitor GBR12909. Rats in the upper quintile of the distribution of perseverative responses during repeated S-R reversals showed significantly reduced levels of the 5-HT metabolite, 5-hydroxy-indoleacetic acid, in the OFC. Additionally, 5-HT2A receptor binding in the OFC of mid- and high-quintile rats was significantly reduced compared with rats in the low-quintile group. These perturbations were accompanied by an increase in the expression of monoamine oxidase-A (MAO-A) and MAO-B in the lateral OFC and by a decrease in the expression of MAO-A, MAO-B, and tryptophan hydroxylase in the dorsal raphé nucleus of highly perseverative rats. We found no evidence of significant differences in markers of DA and 5-HT function in the DMS or MAO expression in the ventral tegmental area of low- vs high-perseverative rats. These findings indicate that diminished serotonergic tone in the OFC may be an endophenotype that predisposes to behavioral inflexibility and other forms of compulsive behavior. PMID:25567428

  17. Glucocorticoid receptor deletion from the dorsal raphé nucleus of mice reduces dysphoria-like behavior and impairs hypothalamic-pituitary-adrenocortical axis feedback inhibition

    PubMed Central

    Vincent, Melanie Y.; Jacobson, Lauren

    2014-01-01

    Glucocorticoids can cause depression and anxiety. Mechanisms for glucocorticoid effects on mood are largely undefined. The dorsal raphé nucleus (DRN) produces the majority of serotonin in the brain, and expresses glucocorticoid receptors (GR). Since we previously showed that antidepressants used to treat depression and anxiety decrease DRN GR expression, we hypothesized that deleting DRN GR would have anxiolytic- and antidepressant-like effects. We also hypothesized that DRN GR deletion would disinhibit activity of the hypothalamic pituitary adrenal (HPA) axis. Adeno-associated virus pseudotype AAV2/9 expressing either Cre recombinase (DRNGRKO mice) or GFP (DRN-GFP mice) was injected into the DRN of floxed GR mice to test these hypotheses. Three weeks after injection, mice underwent 10d of social defeat or control handling and tested for anxiety-like behavior (open field test, elevated plus maze), depression-like behavior (sucrose preference, forced swim test (FST), tail suspension (TST)), social interaction, and circadian and stress-induced HPA activity. DRN GR deletion decreased anxiety-like behavior in control but not in defeated mice. DRN GR deletion decreased FST and tended to decrease TST despair-like behavior in both control and defeated mice, but did not affect sucrose preference. Exploration of social (a novel mouse) as well as neutral targets (an empty box) was increased in DRNGRKO mice, suggesting that DRN GR deletion also promotes active coping. DRN GR deletion increased stress-regulated HPA activity without strongly altering circadian HPA activity. We have shown a novel role for DRN GR to mediate anxiety- and despair-like behavior and to regulate HPA negative feedback during acute stress. PMID:24684372

  18. Aggressive Encounters Alter the Activation of Serotonergic Neurons and the Expression of 5-HT1A mRNA in the Hamster Dorsal Raphe Nucleus

    PubMed Central

    Cooper, Matthew A.; Grober, Matthew S.; Nicholas, Christopher; Huhman, Kim L.

    2009-01-01

    Serotonergic (5-HT) neurons in the dorsal raphe nucleus (DRN) have been implicated in stress-induced changes in behavior. Previous research indicates that stressful stimuli activate 5-HT neurons in select subregions of the DRN. Uncontrollable stress is thought to sensitize 5-HT neurons in the DRN and allow for an exaggerated 5-HT response to future stimuli. In the current study, we tested the hypothesis that following aggressive encounters, losing male Syrian hamsters would exhibit increased c-Fos immunoreactivity in 5-HT DRN neurons compared to winners or controls. In addition, we tested the hypothesis that losers would have decreased 5-HT1A mRNA levels in the DRN compared to winners or controls. We found that a single 15-min aggressive encounter increased c-Fos expression in 5-HT and non-5-HT neurons in losers compared to winners and controls. The increased c-Fos expression in losers was restricted to ventral regions of the rostral DRN. We also found that four 5-min aggressive encounters reduced total 5-HT1A mRNA levels in the DRN in losers compared to winners and controls, and that differences in mRNA levels were not restricted to specific DRN subregions. These results suggest that social defeat activates neurons in select subregions of the DRN and reduces message for DRN 5-HT1A autoreceptors. Our results support the hypothesis that social stress can activate 5-HT neurons in the DRN, reduce 5-HT1A autoreceptor-mediated inhibition, and lead to hyperactivity of 5-HT neurons. PMID:19362123

  19. Effect of hemorrhagic shock on 5-hydroxytryptamine removal by the lung

    SciTech Connect

    Kerstein, M.D.; Cronau, L.H.; Mandel, S.D.; Gillis, C.N.

    1982-12-01

    The biogenic amine, radioactive 5-hydroxytryptamine, is removed from the blood during passage through the pulmonary vasculature. After one hour of hemorrhagic shock, the extraction rate increased from 74 to 89 per cent. One and two hours after resuscitation, the lung extracted only 30 per cent of the 5-hydroxytryptamine. The relationship between the pathophysiologic state and altered amine removal is a reflection of prolonged exposure to receptor sites or increased diffusion of serotonin across the endothelium.

  20. Prior cold water swim stress alters immobility in the forced swim test and associated activation of serotonergic neurons in the rat dorsal raphe nucleus.

    PubMed

    Drugan, R C; Hibl, P T; Kelly, K J; Dady, K F; Hale, M W; Lowry, C A

    2013-12-03

    Prior adverse experience alters behavioral responses to subsequent stressors. For example, exposure to a brief swim increases immobility in a subsequent swim test 24h later. In order to determine if qualitative differences (e.g. 19°C versus 25°C) in an initial stressor (15-min swim) impact behavioral, physiological, and associated neural responses in a 5-min, 25°C swim test 24h later, rats were surgically implanted with biotelemetry devices 1 week prior to experimentation then randomly assigned to one of six conditions (Day 1 (15 min)/Day 2 (5 min)): (1) home cage (HC)/HC, (2) HC/25°C swim, (3) 19°C swim/HC, (4) 19°C swim/25°C swim, (5) 25°C swim/HC, (6) 25°C swim/25°C swim. Core body temperature (Tb) was measured on Days 1 and 2 using biotelemetry; behavior was measured on Day 2. Rats were transcardially perfused with fixative 2h following the onset of the swim on Day 2 for analysis of c-Fos expression in midbrain serotonergic neurons. Cold water (19°C) swim on Day 1 reduced Tb, compared to both 25°C swim and HC groups on Day 1, and, relative to rats exposed to HC conditions on Day 1, reduced the hypothermic response to the 25°C swim on Day 2. The 19°C swim on Day 1, relative to HC exposure on Day 1, increased immobility during the 5-min swim on Day 2. Also, 19°C swim, relative to HC conditions, on Day 1 reduced swim (25°C)-induced increases in c-Fos expression in serotonergic neurons within the dorsal and interfascicular parts of the dorsal raphe nucleus. These results suggest that exposure to a 5-min 19°C cold water swim, but not exposure to a 5-min 25°C swim alters physiological, behavioral and serotonergic responses to a subsequent stressor.

  1. [Neuropeptides in the raphe nuclei: an immunocytochemical study].

    PubMed

    Coveñas, R; Marcos, P; Belda, M; de León, M; Narváez, J A; Aguirre, J A; González-Barón, S

    The raphe nuclei are involved in numerous mechanisms, included the antinociceptives. In the raphe nuclei of the cat, the distribution of neuropeptides is not very studied. Aim. To know the distribution of peptidergic fibers and cell bodies in the raphe nuclei of the cat. We studied a total of fifteen neuropeptides. We used four control cats (without colchicine) and six with colchicine (administered into the Sylvian aqueduct). We used an indirect immunocytochemical technique. The histologic controls carried out confirm the specificity of the primary and secondary antibodies used. We observed in the fibers and/or the cell bodies located in the dorsal raphe nucleus a total of 14 neuropeptides, 12 in the raphe pallidus, 11 in the medial raphe, 10 in the raphe magnus, 8 in the raphe pontis and 7 in the raphe obscurus. We observed immunoreactive cell bodies in the raphe pallidus (with neurokinin A/leucine enkephalin), in the medial raphe (beta endorphin/alpha neo endorphin), in the raphe magnus (leucine enkephalin) and in the dorsal raphe (beta endorphin/alpha neo endorphin/methionine enkephalin Arg6 Gly7 Leu8/leucine enkephalin/neurokinin A/neurotensin). 1. There are differences on the distribution of the peptidergic fibers/cell bodies observed in the raphe nuclei of the rat, the cat and the man; 2. The raphe nuclei could receive peptidergic afferences containing dynorphin A, galanin, neuropeptide Y, somatostatin ; 3. The cell bodies located in the medial raphe and containing beta endorphin or alpha neo endorphin could be projecting neurons; 4. There is a great functional complexity in the raphe nuclei due to the great number of neuropeptides observed in them; 5. The neuropeptides could interact between them, and 6. The neuropeptides located in the raphe nuclei could be involved in the control of the nociceptive information.

  2. Escalated aggression after alcohol drinking in male mice: dorsal raphé and prefrontal cortex serotonin and 5-HT(1B) receptors.

    PubMed

    Faccidomo, Sara; Bannai, Makoto; Miczek, Klaus A

    2008-11-01

    A significant minority of individuals engages in escalated levels of aggression after consuming moderate doses of alcohol (Alc). Neural modulation of escalated aggression involves altered levels of serotonin (5-HT) and the activity of 5-HT(1B) receptors. The aim of these studies was to determine whether 5-HT(1B) receptors in the dorsal raphé (DRN), orbitofrontal (OFC), and medial prefrontal (mPFC) cortex attenuate heightened aggression and regulate extracellular levels of 5-HT. Male mice were trained to self-administer Alc by performing an operant response that was reinforced with a delivery of 6% Alc. To identify Alc-heightened aggressors, each mouse was repeatedly tested for aggression after consuming either 1.0 g/kg Alc or H2O. Next, a cannula was implanted into either the DRN, OFC, or mPFC, and subsets of mice were tested for aggression after drinking either Alc or H(2)O prior to a microinjection of the 5-HT(1B) agonist, CP-94,253. Additional mice were implanted with a microdialysis probe into the mPFC, through which CP-94,253 was perfused and samples were collected for 5-HT measurement. Approximately 60% of the mice were more aggressive after drinking Alc, confirming the aggression-heightening effects of 1.0 g/kg Alc. Infusion of 1 microg CP-94,253 into the DRN reduced both aggressive and motor behaviors. However, infusion of 1 microg CP-94,253 into the mPFC, but not the OFC, after Alc drinking, increased aggressive behavior. In the mPFC, reverse microdialysis of CP-94,253 increased extracellular levels of 5-HT; levels decreased immediately after the perfusion. This 5-HT increase was attenuated in self-administering mice. These results suggest that 5-HT(1B) receptors in the mPFC may serve to selectively disinhibit aggressive behavior in mice with a history of Alc self-administration.

  3. Competition between internal AlF(4)(-) and receptor-mediated stimulation of dorsal raphe neuron G-proteins coupled to calcium current inhibition.

    PubMed

    Chen, Y; Penington, N J

    2000-03-01

    Intracellular aluminum fluoride (AlF(4)(-)), placed in a patch pipette, activated a G-protein, resulting in a "tonic" inhibition of the Ca(2+) current of isolated serotonergic neurons of the rat dorsal raphe nucleus. Serotonin (5-HT) also inhibits the Ca(2+) current of these cells. After external bath application and quick removal of 5-HT to an AlF(4)(-) containing cell, there was a reversal or transient disinhibition (TD) of the inhibitory effect of AlF(4)(-) on Ca(2+) current. A short predepolarization of the membrane potential to +70 mV, a condition that is known to reverse G-protein-mediated inhibition, reversed the inhibitory effect of AlF(4)(-) on Ca(2+) current and brought the Ca(2+) current to the same level as that seen at the peak of the TD current. With AlF(4)(-) in the pipette, the TD phenomenon could be eliminated by lowering pipette MgATP, or by totally chelating pipette Al(3+). In the presence of AlF(4)(-), but with either lowered MgATP or extreme efforts to eliminate pipette Al(3+), the rate of recovery from 5-HT on wash was slowed, a condition opposite to that where a TD occurred. The putative complex of AlF(4)(-)-bound G-protein (Galpha.GDP. AlF(4)(-)) appeared to free G-betagamma-subunits, mimicking the effect on Ca(2+) channels of the G.GTP complex. The ON-rate of the inhibition of Ca(2+) current, after a depolarizing pulse, by betagamma-subunits released by AlF(4)(-) in the pipette was significantly slower than that of the agonist-activated G-protein. The OFF-rate of the AlF(4)(-)-mediated inhibition in response to a depolarizing pulse, a measure of the affinity of the free G-betagamma-subunit for the Ca(2+) channel, was slightly slower than that of the agonist stimulated G-protein. In summary, AlF(4)(-) modified the OFF-rate kinetics of G-protein activation by agonists, but had little effect on the kinetics of the interaction of the betagamma-subunit with Ca(2+) channels. Agonist application temporarily reversed the effects of AlF(4

  4. Cerebral circulatory and metabolic effects of 5-hydroxytryptamine in anesthetized baboons.

    PubMed Central

    Harper, M A; MacKenzie, E T

    1977-01-01

    1. The cerebral circulatory effects of the intracarotid administration of 5-hydroxytryptamine were examined in anaesthetized baboons. Cerebral blood flow was measured by the intracarotid 133Xe technique, cerebral O2 consumption and glucose uptake were measured as indices of brain metabolism and electrocortical activity was continuously monitored. 2. Despite a marked reduction in the calibre of the internal carotid artery (assessed angiographically), the intracarotid infusion of 5-hydroxytryptamine 0-1 microgram/kg. min did not effect any significant changes in cerebral blood flow, O2 consumption or glucose uptake. 3. Following transient osmotic disruption of the blood-brain barrier with the intracarotid infusion of hypertonic urea, the same dose of 5-hydroxytryptamine effected a marked reduction in cerebral blood flow from 51 +/- 2 to 36 +/- 2 ml./100 g. min (mean +/- S.E.; P less than 0-01). Both indices of cerebral metabolism were reduced significantly and the e.e.g. showed a more pronounced suppression-burst pattern. 4. We postulate that the cerebral circulatory responses to 5-hydroxytryptamine are dependent upon the integrity of the blood-brain barrier and the predominant effect of the intravascular administration of 5-hydroxytryptamine is on cortical activity or metabolism, rather than on cerebrovascular smooth muscle. Images Plate 1 PMID:411921

  5. The bacterial flora of the intestine of Ascaris suum and 5-hydroxytryptamine production.

    PubMed

    Hsu, S C; Johansson, K R; Donahue, M J

    1986-08-01

    Representative facultative anaerobes of the bacterial flora from the intestine of female Ascaris suum were isolated and identified. The number of bacteria in the intestine was approximately 4 X 10(9) per g wet weight of intestine. Seventeen of 19 of the isolated colonies were found to secrete 5-hydroxytryptamine in culture. Holding A. suum in an antibiotic-containing medium did not affect the levels of 5-hydroxytryptamine in the worm, which were 231 +/- 14 ng/g in antibiotic-media as compared to 250 +/- 16 ng/g in control media. This implied that the bacteria may not be contributing to the level of 5-hydroxytryptamine in the tissues of A. suum.

  6. 5-Hydroxytryptamine selectively activates the vagal nodose C-fibre subtype in the guinea-pig oesophagus.

    PubMed

    Yu, S; Ru, F; Ouyang, A; Kollarik, M

    2008-09-01

    The afferent neurons innervating the oesophagus originate from two embryonic sources: neurons located in vagal nodose ganglia originate from embryonic placodes and neurons located in vagal jugular and spinal dorsal root ganglia (DRG) originate from the neural crest. Here, we address the hypothesis that 5-hydroxytryptamine (5-HT) differentially stimulates afferent nerve subtypes in the oesophagus. Extracellular recordings of single unit activity originating from nerve terminals were made in the isolated innervated guinea-pig oesophagus. Whole cell patch clamp recordings (35 degrees C) were made from the primary afferent neurons retrogradely labelled from the oesophagus. 5-Hydroxytryptamine (10 micromol L(-1)) activated vagal nodose C-fibres (70%) in the oesophagus but failed to activate overtly vagal jugular nerve fibres and oesophagus-specific spinal DRG neurons. The response to 5-HT in nodose C-fibre nerve terminals was mimicked by the selective 5-HT(3) receptor agonist 2-methyl-5-HT (10 micromol L(-1)) and nearly abolished by the 5-HT(3) receptor antagonists ondansetron (10 micromol L(-1)) and Y-25130 (10 micromol L(-1)). In patch clamp studies, 2-methyl-5-HT (10 micromol L(-1)) activated a proportion of isolated oesophagus-specific nodose capsaicin-sensitive neurons (putative cell bodies of nodose C-fibres). We conclude that the responsiveness to 5-HT discriminates placode-derived (vagal nodose) C-fibres from the neural crest-derived (vagal jugular and spinal DRG) afferent nerves in the oesophagus. The response to 5-HT in nodose C-fibres is mediated by the 5-HT(3) receptor in their neuronal membrane.

  7. Effect of MDMA-Induced Axotomy on the Dorsal Raphe Forebrain Tract in Rats: An In Vivo Manganese-Enhanced Magnetic Resonance Imaging Study

    PubMed Central

    Chiu, Chuang-Hsin; Siow, Tiing-Yee; Weng, Shao-Ju; Hsu, Yi-Hua; Huang, Yuahn-Sieh; Chang, Kang-Wei; Cheng, Cheng-Yi; Ma, Kuo-Hsing

    2015-01-01

    3,4-Methylenedioxymethamphetamine (MDMA), also known as “Ecstasy”, is a common recreational drug of abuse. Several previous studies have attributed the central serotonergic neurotoxicity of MDMA to distal axotomy, since only fine serotonergic axons ascending from the raphe nucleus are lost without apparent damage to their cell bodies. However, this axotomy has never been visualized directly in vivo. The present study examined the axonal integrity of the efferent projections from the midbrain raphe nucleus after MDMA exposure using in vivo manganese-enhanced magnetic resonance imaging (MEMRI). Rats were injected subcutaneously six times with MDMA (5 mg/kg) or saline once daily. Eight days after the last injection, manganese ions (Mn2+) were injected stereotactically into the raphe nucleus, and a series of MEMRI images was acquired over a period of 38 h to monitor the evolution of Mn2+-induced signal enhancement across the ventral tegmental area, the medial forebrain bundle (MFB), and the striatum. The MDMA-induced loss of serotonin transporters was clearly evidenced by immunohistological staining consistent with the Mn2+-induced signal enhancement observed across the MFB and striatum. MEMRI successfully revealed the disruption of the serotonergic raphe-striatal projections and the variable effect of MDMA on the kinetics of Mn2+ accumulation in the MFB and striatum. PMID:26378923

  8. Viral vector mediated expression of mutant huntingtin in the dorsal raphe produces disease-related neuropathology but not depressive-like behaviors in wildtype mice.

    PubMed

    Pitzer, Mark; Lueras, Jordan; Warden, Anna; Weber, Sydney; McBride, Jodi

    2015-05-22

    Huntington׳s disease (HD) is a neurodegenerative disorder caused by a mutation in the HTT gene (mHTT) encoding the protein huntingtin. An expansion in the gene׳s CAG repeat length renders a misfolded, dysfunctional protein with an abnormally long glutamine (Q) stretch at the N terminus that often incorporates into inclusion bodies and leads to neurodegeneration in many regions of the brain. HD is characterized by motor and cognitive decline as well as mood disorders, with depression being particularly common. Approximately 40% of the HD population suffers from depressive symptoms. Because these symptoms often manifest a decade or more prior to the knowledge that the person is at risk for the disease, a portion of the early depression in HD appears to be a consequence of the pathology arising from expression of the mutant gene. While the depression in HD patients is often treated with serotonin agonists, there is scant experimental evidence that the depression in HD responds well to these serotonin treatments or in a similar manner to how non-HD depression tends to respond. Additionally, at very early sub-threshold depression levels, abnormal changes in several neuronal populations are already detectable in HD patients, suggesting that a variety of brain structures may be involved. Taken together, the serotonin system is a viable candidate. However, at present there is limited evidence of the precise nuclei or circuits that play a role in HD depression. With this in mind, the current study was designed to control for the widespread brain neuropathology that occurs in HD and in transgenic mouse models of HD and focuses specifically on the influence of the midbrain dorsal raphe nucleus (DRN). The DRN provides the majority of the serotonin to the forebrain and exhibits cell loss in non-HD depression. Therefore, we employed a viral vector delivery system to investigate whether the over-expression of mHTT in the DRN׳s ventral sub-nuclei alone is sufficient to produce

  9. Viral vector mediated expression of mutant huntingtin in the dorsal raphe produces disease-related neuropathology but not depressive-like behaviors in wildtype mice

    PubMed Central

    Pitzer, Mark; Lueras, Jordan; Warden, Anna; Weber, Sydney; McBride, Jodi

    2017-01-01

    Huntington's disease (HD) is a neurodegenerative disorder caused by a mutation in the HTT gene (mHTT) encoding the protein huntingtin. An expansion in the gene's CAG repeat length renders a misfolded, dysfunctional protein with an abnormally long glutamine (Q) stretch at the N terminus that often incorporates into inclusion bodies and leads to neurodegeneration in many regions of the brain. HD is characterized by motor and cognitive decline as well as mood disorders, with depression being particularly common. Approximately 40% of the HD population suffers from depressive symptoms. Because these symptoms often manifest a decade or more prior to the knowledge that the person is at risk for the disease, a portion of the early depression in HD appears to be a consequence of the pathology arising from expression of the mutant gene. While the depression in HD patients is often treated with serotonin agonists, there is scant experimental evidence that the depression in HD responds well to these serotonin treatments or in a similar manner to how non-HD depression tends to respond. Additionally, at very early sub-threshold depression levels, abnormal changes in several neuronal populations are already detectable in HD patients, suggesting that a variety of brain structures may be involved. Taken together, the serotonin system is a viable candidate. However, at present there is limited evidence of the precise nuclei or circuits that play a role in HD depression. With this in mind, the current study was designed to control for the widespread brain neuropathology that occurs in HD and in transgenic mouse models of HD and focuses specifically on the influence of the midbrain dorsal raphe nucleus (DRN). The DRN provides the majority of the serotonin to the forebrain and exhibits cell loss in non-HD depression. Therefore, we employed a viral vector delivery system to investigate whether the over-expression of mHTT in the DRN's ventral sub-nuclei alone is sufficient to produce

  10. 5-Hydroxytryptamine receptor in isolated rabbit aorta: characterization with tryptamine analogs.

    PubMed

    Clancy, B M; Maayani, S

    1985-06-01

    The 5-HT2 receptor in isolated rabbit thoracic aorta was characterized by examining the relationships between structure and activity of nine tryptamine analogs. All assays were conducted after blockade of the alpha adrenergic receptor and inactivation of the neuronal uptake-1 system and monoamine oxidase. Seven of the analogs tested were agonists. 6-Hydroxytryptamine and 7-hydroxytryptamine showed little or no agonist activity in this preparation. The pA2 of spiperone was independent of the agonist assayed and defined the receptor activated by each agonist as the 5-HT2 receptor. The dissociation constant (KA) and relative intrinsic efficacy were determined for each agonist. The KA and relative intrinsic efficacy values for 5-hydroxytryptamine were 0.25 microM and 1, respectively. The KA and relative intrinsic efficacy values for 5-methoxytryptamine were 0.14 microM and 0.86, respectively, and were not significantly different from those for 5-hydroxytryptamine. The other five analogs were partial agonists. N-Methyl-5-hydroxytryptamine and bufotenine had relative intrinsic efficacies of about 0.3 and KA values not statistically different from the KA value for 5-hydroxytryptamine. Tryptamine, 5-methyltryptamine and alpha-methyl-tryptamine had KA values of about 1 microM and relative intrinsic efficacies of 0.6, 0.6 and 0.4, respectively. These results revealed the differential effects of structural changes on drug affinity and intrinsic efficacy. This information will be applicable in the design of selective agonists or antagonists for the classification of less well defined 5-hydroxytryptamine receptors.

  11. Antinociception induced by intravenous dipyrone (metamizol) upon dorsal horn neurons: involvement of endogenous opioids at the periaqueductal gray matter, the nucleus raphe magnus, and the spinal cord in rats.

    PubMed

    Vazquez, Enrique; Hernandez, Norma; Escobar, William; Vanegas, Horacio

    2005-06-28

    Microinjection of dipyrone (metamizol) into the periaqueductal gray matter (PAG) in rats causes antinociception. This is mediated by endogenous opioidergic circuits located in the PAG itself, in the nucleus raphe magnus and adjacent structures, and in the spinal cord. The clinical relevance of these findings, however, is unclear. Therefore, in the present study, dipyrone was administered intravenously, and the involvement of endogenous opioidergic circuits in the so-induced antinociception was investigated. In rats, responses of dorsal spinal wide-dynamic range neurons to mechanical noxious stimulation of a hindpaw were strongly inhibited by intravenous dipyrone (200 mg/kg). This effect was abolished by microinjection of naloxone (0.5 microg/0.5 microl) into the ventrolateral and lateral PAG or into the nucleus raphe magnus or by direct application of naloxone (50 microg/50 microl) onto the spinal cord surface above the recorded neuron. These results show that dipyrone, a non-opioid analgesic with widespread use in Europe and Latin America, when administered in a clinically relevant fashion causes antinociception by activating endogenous opioidergic circuits along the descending pain control system.

  12. Redistribution by 5-hydroxytryptamine of carotid arterial blood at the expense of arteriovenous anastomotic blood flow

    PubMed Central

    Saxena, Pramod R.; Verdouw, Pieter D.

    1982-01-01

    1. The effects of 5-hydroxytryptamine by intravenous (1, 5 and 10 μg kg-1 min-1 in cats) and intracarotid (0·5 and 2 μg kg-1 min-1 in pigs) routes were studied on the complete distribution of common carotid artery blood flow, measured with radioactive microspheres (15 μm). In addition, the amine was also infused (0·75-3 μg kg-1 min-1) into the carotid artery of cats to observe its influence on the shunting of microspheres in the jugular venous blood. 2. The basal total common carotid blood flow was distributed ipsilaterally mainly to extracerebral tissues and only little blood entered the brain. As shown by the presence of microspheres in the lungs after injection into the carotid artery (52% in cats; 82% in pigs), a major fraction of the carotid blood by-passed the capillary bed through arteriovenous anastomoses in the head (non-nutrient fraction). 3. 5-Hydroxytryptamine redistributed the blood in favour of the nutrient compartment at the expense of arteriovenous anastomotic fraction. In cats, tissue blood flow did not significantly change but, in the pig, blood flow to all tissues, particularly to skin and ears, was substantially increased despite a reduction in total carotid blood flow. This reduction was entirely due to a change in the non-nutrient fraction. 4. Intracarotid infusion of 5-hydroxytryptamine in vagosympathectomized intact or spinal cats decreased the number of microspheres appearing in the jugular venous blood, again indicating a reduction in arteriovenous anastomotic flow due to a constriction of these non-nutrient vessels. 5. Cyproheptadine (1 mg kg-1) completely reversed the effect of 5-hydroxytryptamine on the total carotid blood flow. However, the vasoconstriction of arteriovenous anastomoses was only partially attenuated and the vasodilatatory response was either unchanged (muscle) or even enhanced (skin, ear and bones). 6. It is suggested that 5-hydroxytryptamine causes vasoconstriction of the large arteries via D-receptors which are

  13. Age-related deficit in behavioural extinction is counteracted by long-term ethanol consumption: correlation between 5-HIAA/5HT ratio in dorsal raphe nucleus and cognitive parameters.

    PubMed

    Oliveira-Silva, Ieda F; Pinto, Lucas; Pereira, Silvia R C; Ferraz, Vany P; Barbosa, Alfredo J A; Coelho, Vivian A A; Gualberto, Felipe F A S; Souza, Valeria F; Faleiro, Rosiane R M; Franco, Glaura C; Ribeiro, Angela M

    2007-06-18

    We investigated age-related changes in learning and memory performance and behavioural extinction in the water maze; and in endogenous levels of serotonin (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in the neocortex, hippocampus, thalamus and dorsal raphe nucleus of Wistar rats. Another aim was to assess the correlation between behavioural and biochemical parameters, which were measured in rodents of two different ages: 5 months (adults) and 16 months (middle-aged). The middle-aged subjects succeeded in learning the behavioural task, albeit with significantly worse performance when compared to adult animals. Aging also had significant main effects on memory and extinction. An age-dependent decrease in 5-HIAA levels was observed in both hippocampus and dorsal raphe nucleus (DRN). The decrease in DRN 5-HIAA was paralleled by a decrease in 5-HIAA/5-HT ratio in this brain area, which was significantly correlated to the animals' spatial memory performance and behavioural extinction. In addition, using middle-aged rats, a 2x2 factorial study was carried out to examine the effects of food restriction and chronic ethanol consumption on rat's performance in a spatial behavioural task and on central serotonergic parameters. None of these two treatments had a significant effect on the behavioural and biochemical parameters assessed, with the exception of extinction index, which was significantly affected by ethanol consumption. Long-term ethanol ameliorated the impairment in behavioural flexibility caused by aging. In conclusion, long-term ethanol consumption may have a role in protecting against age-related deficit in behavioural extinction. Moreover, the present results also indicate that DRN serotonergic system is involved in spatial memory and behavioural extinction.

  14. Evidence for a central 5-hydroxytryptamine receptor stimulation by lysergic acid diethylamide

    PubMed Central

    Andén, N.-E.; Corrodi, H.; Fuxe, K.; Hökfelt, T.

    1968-01-01

    1. Lysergic acid diethylamide (LSD) and the 5-hydroxytryptamine (5-HT) precursor, 5-hydroxytryptophan produced similar functional effects in rat spinal cord and brain to the 5-hydroxytryptamine precursor 5-hydroxytryptophan, which indicates that LSD stimulates central 5-HT receptors. 2. By means of combined histochemical and biochemical techniques it was found that LSD reduced the turnover rate of brain and spinal cord 5-HT, studied after inhibition of the tryptophan hydroxylase by α-propyldopacetamide. The turnover of brain noradrenaline but not dopamine was somewhat accelerated. 3. The functional and chemical effects by LSD were related to dose and to time. They were not observed after the LSD analogues 2-bromo-LSD and methylsergide. 4. The retardation of the 5-HT turnover by LSD may be due to negative feed-back mechanisms evoked by direct stimulation of the central 5-HT receptors. ImagesFIG. 1FIG. 2 PMID:5302837

  15. Release of ( sup 14 C)5-hydroxytryptamine from human platelets by red wine

    SciTech Connect

    Jarman, J.; Glover, V.; Sandler, M. )

    1991-01-01

    Red wine, at a final dilution of 1/50, caused released of ({sup 14}C)5-hydroxytryptamine (5-HT) from preloaded platelets, an effect which was not observed with any white wines or beers tested. Since 5-HT, is probably released from body stores during migraine attacks and red wine is known to provoke migraine episodes in susceptible individuals, release of 5-HT, possibly from central stores, could represent a plausible mechanism for its mode of action.

  16. The distribution of 5-hydroxytryptamine in the gastrointestinal tract of reptiles, birds and a prototherian mammal. An immunohistochemical study.

    PubMed

    Adamson, S; Campbell, G

    1988-03-01

    The distribution of 5-hydroxytryptamine in the gut of several species of birds and reptiles, and of a prototherian mammal, the platypus, was studied using a monoclonal antibody. 5-Hydroxytryptamine-like immunoreactivity was found in enterochromaffin cells and, in birds, in thrombocytes. Immunoreactivity was not found in enteric neurons fixed immediately after dissection. A detailed study was made on one avian species, the budgerigar. Following incubation of intestine in physiological solution, immunoreactivity was found in nerve fibres in the gut wall that was more marked after incubation with the monoamine oxidase inhibitor pargyline. These fibres took up exogenous 5-hydroxytryptamine. Similar fibres were found in the intestinal nerves and in perivascular plexuses on mesenteric arteries. Both the uptake of 5-hydroxytryptamine and the appearance of neuronal immunoreactivity after incubation were inhibited by the amine uptake inhibitors desmethylimipramine or fluoxetine. Fibres taking up 5-hydroxytryptamine were damaged by pretreatment with 6-hydroxydopamine. It was concluded that the fibres showing immunoreactivity after incubation were adrenergic fibres that had taken up 5-hydroxytryptamine released in vitro from enterochromaffin cells or thrombocytes. These, and more limited observations made on the other species, suggest that birds, reptiles and prototherian mammals lack enteric neurons that use 5-hydroxytryptamine as a transmitter substance.

  17. Evidence for serotonin synthesis-dependent regulation of in vitro neuronal firing rates in the midbrain raphe complex.

    PubMed

    Evans, Andrew K; Reinders, Niels; Ashford, Katie A; Christie, Isabel N; Wakerley, Jonathan B; Lowry, Christopher A

    2008-08-20

    Evidence suggests that 5-hydroxytryptamine 1A (5-HT(1A)) receptor-mediated autoregulation of serotonergic neuronal firing rates is impaired in stress-related neuropsychiatric disorders. In vitro models may provide insight into neural mechanisms underlying regulation of serotonergic systems. However, serotonin synthesis and tonic autoregulation of serotonergic neuronal firing rates are impaired in in vitro preparations lacking tryptophan. We describe the effects of perfusion of living rat brain slices with tryptophan on both 1) tissue concentrations of serotonin metabolites and 2) neuronal firing rates within the dorsal raphe nucleus. Brain slices were perfused with artificial cerebrospinal fluid lacking tryptophan for 4 h, followed by exposure to 1) 40 microM tryptophan (0-60 min) or 2) 0-400 microM tryptophan (23 min) and microdissected for analysis of indole concentrations. Parallel studies examined effects of tryptophan on neuronal firing rates and interactions with drugs expected to alter synaptic concentrations of serotonin. Tryptophan resulted in time-dependent and concentration-dependent increases in serotonin and serotonin metabolites, effects that were correlated with restoration of tonic autoinhibition of dorsal raphe nucleus neuronal firing rates. Inhibition of serotonin synthesis resulted in time-dependent and concentration-dependent increases in 5-hydroxtryptophan that correlated with reversal of the tryptophan-mediated autoinhibition of neuronal firing rates. Tryptophan modulated effects of several drugs on neuronal firing rates, including a selective 5-HT(1A) receptor antagonist (WAY-100635), a monoamine oxidase inhibitor (pargyline), a selective serotonin reuptake inhibitor (fluoxetine), and a serotonin-releasing agent (methylenedioxymethamphetamine). These studies support the hypothesis that tonic autoregulation of serotonergic neuronal firing rates is dependent on tryptophan availability and characterise conditions necessary to study this process

  18. Influence of 5-hydroxytryptamine (serotonin) on blood flow in the dog pulp

    SciTech Connect

    Kim, S.; Trowbridge, H.O.; Dorscher-Kim, J.E.

    1986-05-01

    The effect of intra-arterial injection of 5-hydroxytryptamine (5-HT) on pulpal blood flow of the dog was determined using the 15-micron radioisotope-labeled microsphere injection method. Pulpal blood flow was significantly reduced following the 5-HT injection. This decrease in blood flow appeared to be due to vasoconstriction as determined by an increase in pulpal vascular hindrance. However, our findings do not preclude the possibility that blood flow was reduced as a result of passive compression of venules produced by vasodilation in a low-compliance environment.

  19. Alterations of central serotonin and dopamine turnover in rats treated with ipsapirone and other 5-hydroxytryptamine1A agonists with potential anxiolytic properties.

    PubMed

    Hamon, M; Fattaccini, C M; Adrien, J; Gallissot, M C; Martin, P; Gozlan, H

    1988-08-01

    Measurements of tissue levels of monoamines and their metabolites, and of the rates of 5-hydroxytryptophan and dihydroxy-phenylalanine accumulation after blockade of aromatic amino acid decarboxylase by benserazid indicated that ipsapirone (1-10 mg/kg i.p.) decreased 5-hydroxytryptamine (5-HT) turnover and accelerated dopamine (DA) turnover in various brain regions. The reduced 5-HT turnover probably resulted from the stimulation of 5-HT1A autoreceptors within the anterior raphe nuclei as in vitro tests [( 3H]-8-hydroxy-2-[di-n-propylamino]tetralin binding and adenylate cyclase assays) demonstrated that ipsapirone was a 5-HT1A agonist almost as potent as 8-OH-DPAT, and the same decrease in 5-hydroxytryptophan accumulation could be induced by the i.p. (5 mg/kg) or intraraphe (1 microgram) injection of ipsapirone. Ipsapirone-induced acceleration of DA turnover persisted after the selective degeneration of serotoninergic neurons by intraraphe 5,7-dihydroxytryptamine infusion, and could be reproduced by i.p. administration of other 5-HT1A agonists like buspirone and gepirone, but not 8-OH-DPAT. These results demonstrate that ipsapirone-induced acceleration of DA turnover did not result from the stimulation of 5-HT1A (auto)receptors, but involved additional target(s) of the drug. The possible participation of dopaminergic systems in the "anxiolytic" properties of ipsapirone should deserve further investigations.

  20. Participation of a transmembrane proton gradient in 5-hydroxytryptamine transport by platelet dense granules and dense-granule ghosts.

    PubMed Central

    Wilkins, J A; Salganicoff, L

    1981-01-01

    Dense granules, the storage organelles for 5-hydroxytryptamine in blood platelets, have been isolated from porcine platelets and are shown to transport 5-hydroxytryptamine in response to a transmembrane proton gradient (delta pH). Transport in the absence of delta pH is minimal, and it is shown that a rapid increase in transport takes place as delta pH increases. Direct measurements with [14C]methylamine show a delta pH of 1.1 units (acid inside) for intact granules. Osmotically active ghosts of dense granules from which 95% of the endogenous 5-hydroxytryptamine content has been released have also been prepared. Ghosts swell in the presence of ATP and Mg2+, and this swelling is shown to be due to the entry of protons via a process linked to ATP hydrolysis. Proton entry is also apparently linked to anion penetration in ghosts. Steady-state 5-hydroxytryptamine transport in ghosts is stimulated approx. 3-fold on the addition of ATP to the incubation medium, and the stimulation of 5-hydroxytryptamine transport in ghosts correlates with the formation of a transmembrane delta pH. Ghosts generate a delta pH of 1.1-1.3 pH units (acid inside) in the presence of 5 mM-ATP/2.5 mM-MgSO4. delta pH is generated within 3 min at 37 degrees C and is dissipated by the ionophore nigericin and by NH4Cl. It is shown that an Mg2+-stimulated ATPase activity is present on the ghost membrane, and inhibition of the ATPase leads to a corresponding decrease in 5-hydroxytryptamine transport. The results presented support the idea that 5-hydroxytryptamine transport into platelet dense granules is dependent on the presence of a transmembrane delta pH and, together with previous findings by others, suggest a generalized mechanism for biogenic amine transport into subcellular storage organelles. Images Fig. 2. PMID:6459780

  1. Gene expression changes in serotonin, GABA-A receptors, neuropeptides and ion channels in the dorsal raphe nucleus of adolescent alcohol-preferring (P) rats following binge-like alcohol drinking.

    PubMed

    McClintick, Jeanette N; McBride, William J; Bell, Richard L; Ding, Zheng-Ming; Liu, Yunlong; Xuei, Xiaoling; Edenberg, Howard J

    2015-02-01

    Alcohol binge-drinking during adolescence is a serious public health concern with long-term consequences. We used RNA sequencing to assess the effects of excessive adolescent ethanol binge-drinking on gene expression in the dorsal raphe nucleus (DRN) of alcohol preferring (P) rats. Repeated binges across adolescence (three 1h sessions across the dark-cycle per day, 5 days per week for 3 weeks starting at 28 days of age; ethanol intakes of 2.5-3 g/kg/session) significantly altered the expression of approximately one-third of the detected genes. Multiple neurotransmitter systems were altered, with the largest changes in the serotonin system (21 of 23 serotonin-related genes showed decreased expression) and GABA-A receptors (8 decreased and 2 increased). Multiple neuropeptide systems were also altered, with changes in the neuropeptide Y and corticotropin-releasing hormone systems similar to those associated with increased drinking and decreased resistance to stress. There was increased expression of 21 of 32 genes for potassium channels. Expression of downstream targets of CREB signaling was increased. There were also changes in expression of genes involved in inflammatory processes, axonal guidance, growth factors, transcription factors, and several intracellular signaling pathways. These widespread changes indicate that excessive binge drinking during adolescence alters the functioning of the DRN and likely its modulation of many regions of the central nervous system, including the mesocorticolimbic system. Copyright © 2014 Elsevier Inc. All rights reserved.

  2. QEHA27, a peptide that binds to G-protein beta gamma-subunits, reduces the inhibitory effect of 5-HT on the Ca2+ current of rat dorsal raphe neurons.

    PubMed

    Chen, Y; Penington, N J

    1997-03-14

    We studied a 27 amino acid peptide (QEHA27) containing the G beta gamma binding motif QXXER, found in adenylyl cyclase 2 and several effector proteins of the G beta gamma-subunit. The patch-clamp technique was utilized to record Ca2+ current from serotonergic dorsal raphe neurons and to introduce the peptide QEHA27 into the cell. We investigated whether it antagonized the inhibitory modulation of Ca2+ current. Compared to the control group, 5-HT was 41% less effective at inhibiting Ca2+ current with 500 microM QEHA27 in the pipette. The QEHA27 peptide did not simply occlude the response to 5-HT because there was no stimulating effect of QEHA27 on the G-protein mediated response. This appears to be the first report of an interference between this peptide and the modulation of Ca2+ currents; it suggests that at least part of the action of the G-protein may be mediated by a beta gamma -subunit.

  3. Corticotropin-releasing factor antagonist reduces activation of noradrenalin and serotonin neurons in the locus coeruleus and dorsal raphe in the arousal response accompanied by yawning behavior in rats.

    PubMed

    Kubota, Natsuko; Amemiya, Seiichiro; Motoki, Chiharu; Otsuka, Tomomi; Nishijima, Takeshi; Kita, Ichiro

    2012-04-01

    We previously reported that intracerebroventricular (icv) administration of corticotropin-releasing factor (CRF) antagonist attenuates the arousal response during yawning behavior in rats. However, the CRF-related pathway involved in the arousal response during yawning is still unclear. In the present study, we assessed the involvement of the CRF-containing pathway from the hypothalamic paraventricular nucleus (PVN) to the locus coeruleus (LC) and the dorsal raphe nucleus (DRN) in the arousal response during frequent spontaneous yawning, which was induced by several microinjections of l-glutamate into the PVN in anesthetized rats, using c-Fos immunohistochemistry. The PVN stimulation showed significant increases in activation of PVN CRF neurons, LC noradrenalin (NA) neurons and DRN serotonin (5-HT) neurons as well as arousal response during yawning. But icv administration of a CRF receptor antagonist, α-helical CRF (9-41), significantly inhibited the activation of both LC NA neurons and DRN 5-HT neurons except the activation of CRF neurons in the PVN, and significantly suppressed the arousal response during yawning. These results suggest that the CRF-containing pathway from PVN CRF neurons to LC NA neurons and DRN 5-HT neurons can be involved in the arousal response during yawning behavior. Copyright © 2012 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

  4. Effects of 5-hydroxytryptamine and 5-hydroxytryptamine 2A/2C agonist on the genioglossus activity and sleep apnea in rats.

    PubMed

    Zhong, Yi-jue; Zhang, Cheng; Wang, Guang-fa

    2010-08-05

    5-Hydroxytryptamine (5-HT) is a common neurotransmitter in the brain which plays an important role in the pathogenesis of sleep apnea. Dysfunction of 5-HT and 5-HT(2) receptors may lead to the collapse of the upper airway and the instability of respiratory control, which in turn produce apnea. Genioglossus (GG) is one of the most important oropharyngeal muscles maintaining the upper airway open. The present study aimed to investigate the effects of 5-HT and 5-HT(2) receptor on GG activity and the sleep apnea in Sprague-Dawley (SD) rats. Microinjection probes were placed within the fourth ventricle of sixteen SD rats. After recovery for a week, the electromyogram (EMG) of GG was recorded in the anesthetized and vagotomized rats. The changes of GG activity before and after the microinjection of 5-HT or 5-HT(2A/2C) agonist -2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI) were observed. Probes were also laid in another eight SD rats. Electroencephalogram (EEG), EMG of neck muscle and respiration were recorded at the same time a week later. The effects of DOI on the occurrence of sleep apnea were explored. Both 5-HT and DOI significantly enhanced the activity of GG just 3 minutes after the completion of injection. The effect of 5-HT disappeared quickly and the effect of DOI lasted for more than 27 minutes. DOI also significantly decreased the post-sigh apnea index in non-rapid-eye-movement (NREM) and rapid-eye-movement (REM) sleep and decreased the spontaneous apnea index only in NREM sleep (P < 0.05, respectively). 5-HT and 5-HT(2A/2C) system correlated closely with the pathogenesis of the sleep apnea syndrome and 5-HT receptors may become the target of the drug treatment.

  5. On the role of 5-hydroxytryptamine in drug-induced antinociception.

    PubMed Central

    Sugrue, M F

    1979-01-01

    1. The effects of four specific inhibitors of 5-hydroxytryptamine (K-HT) uptake on morphine-, methadone- or pethidine-induced antinociception was studied in rats. Antinociception was assessed by means of hot plate (55 degrees C) reaction times. The effect of the compounds on the uptake of [3H]-5-HT into rat whole brain synaptosomes was also investigated. 2. Pretreatment with Org 6582, citalopram, zimelidine or femoxetine at doses devoid of antinociceptive activity potentiated morphine- but not methadone- or pethidine-induced antinociception. 3. A temporal correlation existed between the ability of Org 6582 to potentiate morphine-induced antinociception and to block synaptosomal [3H]-5-HT uptake. 4. 5-HT plays a critical role in the antinociceptive effect of morphine but not of methadone or pethidine. PMID:435690

  6. The effect of altered 5-hydroxytryptamine levels on beta-endorphin

    NASA Technical Reports Server (NTRS)

    Soliman, Karam F. A.; Mash, Deborah C.; Walker, Charles A.

    1986-01-01

    The purpose of the present study was to examine the effect of altering the concentration of 5-hydroxytryptamine (5-HT) on beta-endorphin (beta-Ep) content in the hypothalamus, thalamus, and periaqueductal gray (PAG)-rostral pons regions of the rat brain. The selective 5-HT reuptake inhibitor, fluoxetine (10 mg/kg), significantly lowered beta-Ep content in the hypothalamus and the PAG. Parachlorophenylalanine, which inhibits 5-HT synthesis, significantly elevated beta-Ep in all brain parts studied. Intracisternal injections of the neurotoxin 5-prime, 7-prime-dihydroxytryptamine with desmethylimipramine pretreatment significantly increased beta-Ep content in the hypothalamus and the PAG. In adrenalectomized rats, fluoxetine significantly decreased beta-Ep levels in the hypothalamus and increased the levels in the PAG. The results indicate that 5-HT may modulate the levels of brain beta-Ep.

  7. Platelet 5-hydroxytryptamine release and aggregation promoted by cotton bracts tannin.

    PubMed

    Rohrbach, M S; Rolstad, R A; Tracy, P B; Russell, J A

    1984-01-01

    The effect of aqueous extracts of cotton bract (CBE) on platelet secretion and aggregation was examined by using washed bovine and human platelets. The CBE promoted the release of 75% to 90% of the 5-hydroxytryptamine (5-HT) stored in both human and bovine platelets in a dose-dependent manner. This release reaction occurred without the lysis of the platelets and was not inhibited by indomethacin, 2-deoxyglucose, or KCN. Fractionation of the CBE indicated that the platelet secretagogue present in the CBE was the condensed polyphenol, tannin. In addition to promoting the secretion of 5-HT, tannin also aggregated the platelets in a dose-dependent manner. We conclude that the secretion of platelet 5-HT and the aggregation of platelets by tannin could potentially contribute to the pulmonary symptoms associated with byssinosis.

  8. The effect of altered 5-hydroxytryptamine levels on beta-endorphin

    NASA Technical Reports Server (NTRS)

    Soliman, Karam F. A.; Mash, Deborah C.; Walker, Charles A.

    1986-01-01

    The purpose of the present study was to examine the effect of altering the concentration of 5-hydroxytryptamine (5-HT) on beta-endorphin (beta-Ep) content in the hypothalamus, thalamus, and periaqueductal gray (PAG)-rostral pons regions of the rat brain. The selective 5-HT reuptake inhibitor, fluoxetine (10 mg/kg), significantly lowered beta-Ep content in the hypothalamus and the PAG. Parachlorophenylalanine, which inhibits 5-HT synthesis, significantly elevated beta-Ep in all brain parts studied. Intracisternal injections of the neurotoxin 5-prime, 7-prime-dihydroxytryptamine with desmethylimipramine pretreatment significantly increased beta-Ep content in the hypothalamus and the PAG. In adrenalectomized rats, fluoxetine significantly decreased beta-Ep levels in the hypothalamus and increased the levels in the PAG. The results indicate that 5-HT may modulate the levels of brain beta-Ep.

  9. Feeding increases 5-hydroxytryptamine and norepinephrine within the hypothalamus of chicks.

    PubMed

    Tachibana, T; Tazawa, M; Sugahara, K

    2001-11-01

    It is thought that hypothalamic 5-hydroxytryptamine (5HT) and norepinephrine (NE) are involved in the regulation of feeding in chicks. The present study was conducted to elucidate changes in the levels of extracellular 5HT and NE in the hypothalamus during feeding of chicks. In order to measure 5HT, NE and 4-hydroxy-3-methoxyphenylglycol (MHPG), which is a major metabolite of NE, we used brain microdialysis and high-pressure liquid chromatography with an electrochemical detector. After collecting samples to determine the basal levels of 5HT, NE and MHPG, food-deprived birds were given access to food. 5HT levels in the medial hypothalamus (MH) and lateral hypothalamus (LH) increased during the first 30 min of feeding, and then returned to basal levels. NE and MHPG in the LH increased during feeding, and remained elevated throughout the experiment. This study supports an idea that hypothalamic monoamines in the chick brain are involved in the regulation of feeding.

  10. Iontophoretic release of acetylcholine, noradrenaline, 5-hydroxytryptamine and D-lysergic acid diethylamide from micropipettes

    PubMed Central

    Bradley, P. B.; Candy, J. M.

    1970-01-01

    1. The in vitro iontophoretic release of tritium-labelled acetylcholine and 5-hydroxytryptamine from large and small micropipettes and noradrenaline and D-lysergic acid diethylamide from small micropipettes was determined by liquid scintillation counting. 2. The release was directly proportional to the electrical charge passed in the range normally used in the iontophoretic study of these compounds. The transport numbers obtained for the large micropipettes were approximately double those with the small micropipettes. A very low transport number was found for D-lysergic acid diethylamide. 3. The spontaneous leakage was small and did not vary appreciably with time. 4. The iontophoretic release of acetylcholine in vitro agreed with the in vitro measurements. 5. The brain-stem tissue concentration of D-lysergic acid diethylamide after intravenous injection into intact and decerebrate cats was determined. PMID:5492892

  11. Repeated chlorpromazine administration increases a behavioural response of rats to 5-hydroxytryptamine receptor stimulation.

    PubMed Central

    Green, A R

    1977-01-01

    1 The hyperactivity syndrome produced in rats by administration of tranylcypromine (20 mg/kg i.p.) followed 30 min later by L-tryptophan (50 mg/kg i.p.) is generally considered to be due to increased 5-hydroxytryptamine (5-HT) functional activity. It is inhibited by chlorpromazine (30 mg/kg i.p.) injected 60 min before the tranylcypromine. However, chlorpromazine injection for 4 days either at a dose of 30 mg/kg once daily or 5 mg/kg twice daily results in an enhanced hyperactivity response to tranylcypromine and L-tryptophan administration 24 h after the final dose of chlorpromazine. 2 One injection of chlorpromazine (30 mg/kg) did not produce enhancement 24 h later and the inhibition of the tranylcypromine/L-tryptophan hyperactivity observed after acute chlorpromazine injection was seen if the rats were given tranylcypromine and L-tryptophan 1 h after the fourth chlorpromazine (30 mg/kg) dose. 3 Chlorpromazine (30 mg/kg) once daily or 5 mg/kg twice daily for 4 days resulted in rats displaying enhanced behavioral responses to the suggested 5-HT agonist 5-methoxy N,N-dimethyltryptamine (2 mg/kg) on day 5. 4 Chlorpromazine (30 mg/kg) once daily for 4 days produces a slight increase in brain 5-hydroxytryptamine (5-HT) concentration on day 5, but no difference in the rate of brain 5-HT synthesis or the rate of 5-HT accumulation after tranylcypromine and L-tryptophan administration. 5. There is some evidence that chlorpromazine blocks 5-HT receptors. It has also been observed that several other neuroleptic drugs do not produce enhanced 5-HT responses after repeated administration. It is suggested therefore that the enhanced behavioural response to 5-HT receptor stimulation following repeated chlorpromazine administration may be because this drug blocks 5-HT receptors. PMID:264797

  12. Depressive disorder and gastrointestinal dysfunction after myocardial infarct are associated with abnormal tryptophan-5-hydroxytryptamine metabolism in rats

    PubMed Central

    Liu, Chunyan; Wang, Yangang

    2017-01-01

    In this study, we investigated the relationship between tryptophan-5-hydroxytryptamine metabolism, depressive disorder, and gastrointestinal dysfunction in rats after myocardial infarction. Our goal was to elucidate the physiopathologic bases of somatic/psychiatric depression symptoms after myocardial infarction. A myocardial infarction model was established by permanent occlusion of the left anterior descending coronary artery. Depression-like behavior was evaluated using the sucrose preference test, open field test, and forced swim test. Gastric retention and intestinal transit were detected using the carbon powder labeling method. Immunohistochemical staining was used to detect indoleamine 2,3-dioxygenase expression in the hippocampus and ileum. High-performance liquid chromatography with fluorescence and ultraviolet detection determined the levels of 5-hydroxytryptamine, its precursor tryptophan, and its metabolite 5-hydroxyindoleacetic acid in the hippocampus, distal ileum, and peripheral blood. All data were analyzed using one-way analyses of variance. Three weeks after arterial occlusion, rats in the model group began to exhibit depression-like symptoms. For example, the rate of sucrose consumption was reduced, the total and central distance traveled in the open field test were reduced, and immobility time was increased, while swimming, struggling and latency to immobility were decreased in the forced swim test. Moreover, the gastric retention rate and gastrointestinal transit rate were increased in the model group. Expression of indoleamine 2,3-dioxygenase was increased in the hippocampus and ileum, whereas 5-hydroxytryptamine metabolism was decreased, resulting in lower 5-hydroxytryptamine and 5-hydroxyindoleacetic acid levels in the hippocampus and higher levels in the ileum. Depressive disorder and gastrointestinal dysfunction after myocardial infarction involve abnormal tryptophan-5-hydroxytryptamine metabolism, which may explain the somatic, cognitive

  13. Depressive disorder and gastrointestinal dysfunction after myocardial infarct are associated with abnormal tryptophan-5-hydroxytryptamine metabolism in rats.

    PubMed

    Lu, Xiaofang; Wang, Yuefen; Liu, Chunyan; Wang, Yangang

    2017-01-01

    In this study, we investigated the relationship between tryptophan-5-hydroxytryptamine metabolism, depressive disorder, and gastrointestinal dysfunction in rats after myocardial infarction. Our goal was to elucidate the physiopathologic bases of somatic/psychiatric depression symptoms after myocardial infarction. A myocardial infarction model was established by permanent occlusion of the left anterior descending coronary artery. Depression-like behavior was evaluated using the sucrose preference test, open field test, and forced swim test. Gastric retention and intestinal transit were detected using the carbon powder labeling method. Immunohistochemical staining was used to detect indoleamine 2,3-dioxygenase expression in the hippocampus and ileum. High-performance liquid chromatography with fluorescence and ultraviolet detection determined the levels of 5-hydroxytryptamine, its precursor tryptophan, and its metabolite 5-hydroxyindoleacetic acid in the hippocampus, distal ileum, and peripheral blood. All data were analyzed using one-way analyses of variance. Three weeks after arterial occlusion, rats in the model group began to exhibit depression-like symptoms. For example, the rate of sucrose consumption was reduced, the total and central distance traveled in the open field test were reduced, and immobility time was increased, while swimming, struggling and latency to immobility were decreased in the forced swim test. Moreover, the gastric retention rate and gastrointestinal transit rate were increased in the model group. Expression of indoleamine 2,3-dioxygenase was increased in the hippocampus and ileum, whereas 5-hydroxytryptamine metabolism was decreased, resulting in lower 5-hydroxytryptamine and 5-hydroxyindoleacetic acid levels in the hippocampus and higher levels in the ileum. Depressive disorder and gastrointestinal dysfunction after myocardial infarction involve abnormal tryptophan-5-hydroxytryptamine metabolism, which may explain the somatic, cognitive

  14. Effect of antibiotics on the 5-hydroxytryptamine content of the small intestine and other organs in rats and mice

    PubMed Central

    Sullivan, T. J.

    1961-01-01

    Rats and mice were given antibiotics orally and by subcutaneous injection and the effects on tissue levels of 5-hydroxytryptamine and intestinal bacteria were studied. In mice it was found that antibiotics which caused a large reduction in the bacterial flora of the intestine when given orally also caused a significant increase in intestinal 5-hydroxytryptamine. In rats, neomycin caused a reduction in the urinary excretion of 5-hydroxyindoleacetic acid. In both rats and mice, many antibiotics caused a significant reduction in the weight of the spleen. PMID:19108146

  15. The effect of lysergic acid diethylamide, 5-hydroxytryptamine, and related compounds on the liver fluke, fasciola hepatica

    PubMed Central

    Mansour, T. E.

    1957-01-01

    The rhythmical activity of the liver fluke, Fasciola hepatica, was stimulated by 5-hydroxytryptamine and by lysergic acid diethylamide at very low concentrations. The effect was peripheral and was not mediated through the central ganglion. Other amines also stimulated rhythmical activity, the most potent being the indolamines. Bromolysergic acid diethylamide, and other analogues such as yohimbine, harmine, and dopamine depressed rhythmical movement and antagonized the stimulant action of 5-hydroxytryptamine and lysergic acid diethylamide. Evidence which suggests the presence of tryptamine receptors in the trematode is discussed. PMID:13489165

  16. Ionic currents influencing spontaneous firing and pacemaker frequency in dopamine neurons of the ventrolateral periaqueductal gray and dorsal raphe nucleus (vlPAG/DRN): A voltage-clamp and computational modelling study.

    PubMed

    Dougalis, Antonios G; Matthews, Gillian A C; Liss, Birgit; Ungless, Mark A

    2017-04-03

    Dopamine (DA) neurons of the ventrolateral periaqueductal gray (vlPAG) and dorsal raphe nucleus (DRN) fire spontaneous action potentials (APs) at slow, regular patterns in vitro but a detailed account of their intrinsic membrane properties responsible for spontaneous firing is currently lacking. To resolve this, we performed a voltage-clamp electrophysiological study in brain slices to describe their major ionic currents and then constructed a computer model and used simulations to understand the mechanisms behind autorhythmicity in silico. We found that vlPAG/DRN DA neurons exhibit a number of voltage-dependent currents activating in the subthreshold range including, a hyperpolarization-activated cation current (IH), a transient, A-type, potassium current (IA), a background, 'persistent' (INaP) sodium current and a transient, low voltage activated (LVA) calcium current (ICaLVA). Brain slice pharmacology, in good agreement with computer simulations, showed that spontaneous firing occurred independently of IH, IA or calcium currents. In contrast, when blocking sodium currents, spontaneous firing ceased and a stable, non-oscillating membrane potential below AP threshold was attained. Using the DA neuron model we further show that calcium currents exhibit little activation (compared to sodium) during the interspike interval (ISI) repolarization while, any individual potassium current alone, whose blockade positively modulated AP firing frequency, is not required for spontaneous firing. Instead, blockade of a number of potassium currents simultaneously is necessary to eliminate autorhythmicity. Repolarization during ISI is mediated initially via the deactivation of the delayed rectifier potassium current, while a sodium background 'persistent' current is essentially indispensable for autorhythmicity by driving repolarization towards AP threshold.

  17. Social instigation and aggression in postpartum female rats: role of 5-Ht1A and 5-Ht1B receptors in the dorsal raphé nucleus and prefrontal cortex

    PubMed Central

    da Veiga, Caroline Perinazzo; Miczek, Klaus A.; Lucion, Aldo Bolten

    2013-01-01

    Rationale 5-HT1A and 5-HT1B receptor agonists effectively reduce aggressive behavior in males that has been escalated by social instigation. Important sites of action for these drugs are the receptors in dorsal raphé nuclei (DRN) and the ventral–orbital prefrontal cortex (VO PFC). DRN and VO PFC areas are particularly relevant in the inhibitory control of escalated aggressive and impulsive behavior. Objectives The objectives of this study are to assess the anti-aggressive effects of 5-HT1A (8-OH-DPAT) and 5-HT1B (CP-93,129) receptor agonists microinjected into DRN and VO PFC, respectively, and to study the aggressive behavior in postpartum female Wistar rats using the social instigation protocol to increase aggression. Methods and Results 8-OH-DPAT (0.56 µg) in the DRN increased aggressive behavior in postpartum female rats. By contrast, CP-93,129 (1.0 µg) microinjected into VO PFC decreased the number of attack bites and lateral threats. 5-HT1A and 5-HT1B receptor agonists differed in their effects on non-aggressive activities, the former decreasing rearing and grooming and the latter increasing these acts. When 8-OH-DPAT was microinjected into DRN and CP-93,129 was microinjected into VO PFC in female rats at the same time, maternal aggression decreased. Specific participation of 5-HT1B receptors was verified by reversal of the anti-aggressive effects using the selective antagonist SB-224,289 (1.0 µg). Conclusions The decrease in maternal aggressive behavior after microinjections of 5-HT1B receptor agonists into the VO PFC and DRN of female postpartum rats that were instigated socially supports the hypothesis that activation of these receptors modulates high levels of aggression in a behaviorally specific manner, due to activation of 5-HT1B receptors at the soma and terminals. PMID:21107539

  18. Potentiation of RSU-1069 tumour cytotoxicity by 5-hydroxytryptamine (5-HT).

    PubMed

    Chaplin, D J

    1986-11-01

    It is known that many solid animal tumours have a lower oxygenation level than most normal tissues and, in addition, that this level of oxygenation can be further decreased by systemic administration of 5-hydroxytryptamine (5-HT). The present study has investigated if such selective decrease in tumour oxygenation can be exploited by using the hypoxic cell cytotoxin, RSU-1069. The results obtained show that 5-HT at a dose of 5 mg kg-1, although not cytotoxic alone, can potentiate the cytotoxic effects of RSU-1069 in the Lewis lung carcinoma over the dose range 0.01-0.15 mg g-1. Maximum potentiation occurs when 5-HT is administered after RSU-1069. Potentiation of RSU-1069 cytotoxicity was observed using both the soft agar excision assay as an endpoint as well as in situ growth delay. In addition, the study shows that potentiation of RSU-1069 (0.1 mg g-1) cytotoxicity can be seen with 5-HT doses as low as 0.5 mg kg-1. In contrast to the tumour cytotoxicity results, 5-HT at a dose of 5 mg kg-1 i.p. did not affect the systemic toxicity, as measured by LD50/7d of RSU-1069. Thus, these results indicate that 5-HT can increase the therapeutic efficiency of RSU-1069. Such a finding is consistent with the rationale that selective reduction in tumour blood flow and oxygenation induced by 5-HT can be exploited using the hypoxic cell cytotoxin RSU-1069.

  19. Effect of halothane on metabolism of 5-hydroxytryptamine by rat lungs perfused in situ.

    PubMed Central

    Watkins, C A; Wartell, S A; Rannels, D E

    1983-01-01

    The effect of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) on the uptake of 14C-labelled 5-hydroxytryptamine (5-HT) and its metabolism to 5-hydroxyindol-3-ylacetic acid (5-HIAA) was investigated in rat lungs perfused in situ. The rate of accumulation of 14C-labelled 5-HIAA in the tissue, monitored as an index of 5-HT metabolism, was linear with time, displayed saturation kinetics and remained stable for at least 180 min of perfusion. Exposure of the lungs to halothane (4%) for 60 min reversibly reduced production of 5-HIAA through an increase in the apparent Km for metabolism of the amine from 1.45 to 3.52 microM (P less than 0.001); the anaesthetic had no effect on the Vmax. of the process. The magnitude of the inhibition increased with time of exposure to the anaesthetic. Halothane exposure did not alter the distribution of [3H]sorbitol or [14C]5-HT, pulmonary vascular resistance, levels of ATP or the kinetics of amino acid transport in the tissue. Inhibition of protein synthesis by cycloheximide did not mimic the effect of the anaesthetic. These observations, together with those made in lungs exposed to inhibitors of 5-HT uptake and metabolism, were consistent with a halothane-mediated inhibition of 5-HT uptake, which did not appear to involve non-specific changes in membrane permeability. PMID:6847641

  20. Role of 5-hydroxytryptamine in the regulation of brain neuropeptides in normal and diabetic rat

    NASA Technical Reports Server (NTRS)

    Kolta, Malak G.; Williams, Byron B.; Soliman, Karam F. A.

    1986-01-01

    The effect of 5-hydroxytryptamine (5-HT) alteration on brain dopamine (DA), norepinephrine (NE), beta-endorphin (beta-E), and immunoreactive insulin was studied in Sprague-Dawley diabetic and control rats. Diabetes was induced using alloxan (45 mg/kg), 15 days prior to sacrificing. Both control and diabetic animals were treated with either p-chlorophenylalanine (PCPA, 300 mg/kg) three days prior to sacrificing or fluoxetine (10 mg/kg) twice daily for three days. PCPA treatment significantly decreased brain content of 5-HT and 5-hydroxyindolel acetic acid, while it caused significant increase and decrease in brain beta-E and insulin levels, respectively, in both normal and diabetic rat. Meanwhile, the administration of fluoxetine resulted in significant increase in brain content of 5-HT, DA, NE and insulin but significant decline of beta-E in diabetic and saline control rats. The results of this experiment indicate that 5-HT may be regulating both beta-E and insulin regardless of the availability of pancreatic insulin.

  1. Allergic sensitization modifies the pulmonary expression of 5-hydroxytryptamine receptors in guinea pigs.

    PubMed

    Córdoba-Rodríguez, Guadalupe; Vargas, Mario H; Ruiz, Víctor; Carbajal, Verónica; Campos-Bedolla, Patricia; Mercadillo-Herrera, Paulina; Arreola-Ramírez, José Luis; Segura-Medina, Patricia

    2016-03-01

    There is mounting evidence that 5-hydroxytryptamine (5-HT) plays a role in asthma. However, scarce information exists about the pulmonary expression of 5-HT receptors and its modification after allergic sensitization. In the present work, we explored the expression of 5-HT1A, 5-HT2A, 5-HT3, 5-HT4, 5-ht5a, 5-HT6, and 5-HT7 receptors in lungs from control and sensitized guinea pigs through qPCR and Western blot. In control animals, mRNA from all receptors was detectable in lung homogenates, especially from 5-HT2A and 5-HT4 receptors. Sensitized animals had decreased mRNA expression of 5-HT2A and 5-HT4 receptors and increased that of 5-HT7 receptor. In contrast, they had increased protein expression of 5-HT2A receptor in bronchial epithelium and of 5-HT4 receptor in lung parenchyma. The degree of airway response to the allergic challenge was inversely correlated with mRNA expression of the 5-HT1A receptor. In summary, our results showed that major 5-HT receptor subtypes are constitutively expressed in the guinea pig lung, and that allergic sensitization modifies the expression of 5-HT2A, 5-HT4, and 5-HT7 receptors. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Species differences in the responses of pulmonary vascular preparations to 5-hydroxytryptamine.

    PubMed

    Morcillo, E J; Cortijo, J

    1999-01-01

    5-Hydroxytryptamine (5-HT) has been implicated in pulmonary hypertension, hypoxic pulmonary vasoconstriction, and the pulmonary side-effects of some drugs. 5-HT contracts bovine, ovine, canine, caprine, feline, rabbit, guinea-pig and rat isolated pulmonary arteries mainly by activation of 5-HT2A receptors but relaxes porcine pulmonary artery through activation of endothelial 5-HT2B receptors. Pharmacological responses of the pulmonary veins to 5-HT have been less studied and comprise both contraction (bovine, canine, feline, equine, rabbit) and relaxation (ovine, caprine). Functional and radioligand binding studies in human isolated intrapulmonary arteries and veins have demonstrated a mixed population of 5-HT1B/1D and 5-HT2A receptors mediating vasoconstriction but no evidence of involvement of 5-HT1A, 5-HT3 and 5-HT4 receptors. Remarkable differences exist in the in vitro pulmonary vasoreactivity to 5-HT and related drugs in humans compared with other mammals. Therefore, the use of human tissues is to be preferred to study pathophysiological responses of pulmonary circulation with clinical relevance.

  3. Methotrexate causes a change in intestinal 5-hydroxytryptamine metabolism in rats.

    PubMed

    Takano, Yuho; Machida, Takuji; Obara, Yusuke; Hirano, Megumi; Kudo, Sae; Takagi, Minako; Hamaue, Naoya; Iizuka, Kenji; Hirafuji, Masahiko

    2014-10-05

    The effects of methotrexate on 5-hydroxytryptamine (5-HT) metabolism in the intestinal tissue of rats were investigated during the delayed phase after a single administration. Rats were i.p. injected with methotrexate or with saline as a control, and kaolin and food intakes were measured by an automatic monitoring apparatus. At 96 h after administration, dissected-out ileal tissue was frozen rapidly in liquid nitrogen for further analysis or fixed for immunohistochemical staining. Methotrexate at a dose of 50 mg/kg caused a time-dependent increase in kaolin intake lasting up to 72 h after administration, which returned to the control level at 96 h after administration. This dose of methotrexate caused a gradual decrease in body weight, food intake, and water intake lasting up to 72 h, which approached the control level at 96 h. Methotrexate caused pathologic changes, including a moderate inflammatory response in the ileal tissue and an increase in the number of L-tryptophan hydroxylase (TPH)-expressing cells in the ileal mucosa. Methotrexate also caused a significant increase in 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) content and in TPH1 mRNA expression in the ileal tissues. It had no significant effects on mRNA expression of serotonin transporter, COX-1, or COX-2 or on myeloperoxidase activity. This study demonstrated, for the first time, that methotrexate caused a change in the ileal 5-HT metabolism associated with hyperplasia of mucosal enterochromaffin cells.

  4. Interactions between GABA and 5-hydroxytryptamine in the guinea-pig ileum.

    PubMed

    Ong, J; Kerr, D I

    1983-10-28

    In isolated segments of the guinea-pig ileum, there was: (a) an early, short-lived (less than 20 s) depression by gamma-aminobutyric acid (GABA) of contractile responses to 5-hydroxytryptamine (5-HT), acetylcholine(ACh), or nicotine, also seen with 3-amino-1-propanesulphonic acid (3APS) or muscimol in place of GABA, and sensitive to bicuculline, picrotoxinin or piretanide, and (b) a delayed, longer-lasting (30 s-1 min) depression of responses to 5-HT and nicotine, but not exogenously applied ACh, also seen with baclofen and only antagonised by delta-aminovaleric acid (DAVA). At 25 degrees C, all these effects were still observed but slowed, whilst at 37 degrees C after cold storage (6 degrees C) overnight, the early, short-lived depression was reduced or eliminated, yet the delayed depression was enhanced. It is concluded that the early, short-lived depression is mediated through GABAA-receptor sites, and the delayed, longer-lasting depression through GABAB-receptor sites on neurones of the myenteric plexus; effects consistent with GABA being a neurotransmitter in the enteric nervous system.

  5. Effects of 5-hydroxytryptamine on defecation in open-field behavior in rats.

    PubMed

    Kameyama, T; Suzuki, M; Nabeshima, T

    1980-06-01

    An attempt was made to elucidate the role of the serotonergic nervous sytem in defecation resulting from environmental stimulation in rats. The open-field (OF) test and shuttle box method were used to study the defecation. 5-Hydroxytryptophan (5-HTP) significantly decreased the number of fecal boluses excreted in both emotional situations, namely, in both OF and shuttle box. The fecal excretion was significantly reduced compared with the controls after intraventricular injection of 5-hydroxytryptamine (5-HT). Animals pretreated with p-chlorophenylalanine (pCPA) and 5,6-dihydroxytryptamine (5,6-DHT) tended to show a slight increase in the OF defecation. 5-HTP was equally effective in diminishing the OF performance of pCPA-treated rats. The inhibitory effects of 5-HTP on the defecation were also observed after depletion of biogenic amines by reserpine treatment. Home cage defecation was increased after 5-HTP administration, decreased under pretreatment with pCPA and not influenced by intraventricular injection of 5-HTP. These results suggested that the defecation after environmental stimuli was due to a change in 5-HT levels in the brain.

  6. 5-hydroxytryptamine1B receptor and triptan response in migraine, lack of association with common polymorphisms.

    PubMed

    Velati, Daniela; Viana, Michele; Cresta, Stefania; Mantegazza, Paola; Testa, Lucia; Bettucci, Diego; Rinaldi, Maurizio; Sances, Grazia; Tassorelli, Cristina; Nappi, Giuseppe; Canonico, Pier Luigi; Martignoni, Emilia; Genazzani, Armando A

    2008-02-02

    Triptans mediate vasoconstriction of meningeal vessels via stimulation of vascular 5-hydroxytryptamine (5-HT)(1B) receptors. These drugs are recommended for acute treatment in patients with moderate-to-severe migraine attacks and in those patients with mild-to-moderate headache that are not controlled adequately by other agents. Yet, approximately 25% of all migraine users and 40% of all attacks do not respond to triptan treatment. Among the hypothesis to explain this is the possibility that genetic single nucleotide polymorphisms that alter the receptor, for example changing the transcriptional rate and therefore the amount of target protein might change the clinical response to these drugs. In the present contribution, we therefore decided to evaluate whether single nucleotide polymorphisms on the 5-HT(1B) gene might contribute to inter-individual variability in clinical responses to triptans. Two polymorphisms in the promoter region of the 5-HT(1B) receptor (T-261G and A-161T) and the synonymous variation G861C in the coding region were genotyped by restriction fragment length polymorphism in 105 migraine patients. In our sample population, 71% of patients responded to triptans. Allelic and diplotype frequencies were not significantly different between responders and non-responders. On the other hand, extrapolation of in vitro data on promoter activity would suggest that patients with higher copy number of receptors respond slightly better. Our data therefore do not support the involvement of 5-HT(1B) single nucleotide polymorphisms in mediating the inter-individual variability to triptans.

  7. γ-Aminobutyric acid suppresses enhancement of hamster sperm hyperactivation by 5-hydroxytryptamine

    PubMed Central

    FUJINOKI, Masakatsu; TAKEI, Gen L.

    2016-01-01

    Sperm hyperactivation is regulated by hormones present in the oviduct. In hamsters, 5-hydroxytryptamine (5HT) enhances hyperactivation associated with the 5HT2 receptor and 5HT4 receptor, while 17β-estradiol (E2) and γ-aminobutyric acid (GABA) suppress the association of the estrogen receptor and GABAA receptor, respectively. In the present study, we examined the regulatory interactions among 5HT, GABA, and E2 in the regulation of hamster sperm hyperactivation. When sperm were exposed to E2 prior to 5HT exposure, E2 did not affect 5HT-enhanced hyperactivation. In contrast, GABA partially suppressed 5HT-enhanced hyperactivation when sperm were exposed to GABA prior to 5HT. GABA suppressed 5HT-enhanced hyperactivation associated with the 5HT2 receptor although it did not suppress 5HT-enhanced hyperactivation associated with the 5HT4 receptor. These results demonstrate that hamster sperm hyperactivation is regulated by an interaction between the 5HT2 receptor-mediated action of 5HT and GABA. PMID:27773888

  8. Radioimmunoassay of serotonin (5-hydroxytryptamine) in cerebrospinal fluid, plasma, and serum

    SciTech Connect

    Engbaek, F.; Voldby, B

    1982-04-01

    A direct radioimmunoassay is described for serotonin (5-hydroxytryptamine) in cerebrospinal fluid, platelet-poor plasma, and serum. Antisera in rabbits was raised against serotonin diazotized to a conjugate of bovine albumin and D,L-p-aminophenylalanine. Polyethylene glycol, alone or in combination with anti-rabbit immunoglobulins, is used to separate bound and unbound tritiated serotonin. The minimum concentration of serotonin detectable is 2 nmol/L in a 200-..mu..L sample. Within-day precision (CV) is 4.3% between-day precision 7.7%. Analytical recoveries of serotonin are 109% and 101% for cerebrospinal fluid and plasma, respectively. Tryptophan, 5-hydroxytryptophan, 5-hydroxyindoleacetic acid, and 5-hydroxytryptophol do not interfere with the assay. However, 5-methoxytryptamine and tryptamine cross react. Of samples of cerebrospinal fluid from patients with disc herniations (n=21) or low-pressure hydrocephalus (n=10), one-third had concentrations of 2-4 nmol/L and two-thirds were below the minimum detectable concentration. The observed range for the concentration of serotonin in plasma of 14 normal subjects was 5-14 nmol/L (mean +/- SD, 9 +/- 3 nmol/L). The observed ranges for serotonin in serum were: for 10 women 520-900 (mean +/- SD: 695 +/- 110) nmol/L and for 10 men 380-680 (520 +/- 94) nmol/L.

  9. beta-Adrenoceptor agonists enhance 5-hydroxytryptamine-mediated behavioural responses.

    PubMed Central

    Cowen, P. J.; Grahame-Smith, D. G.; Green, A. R.; Heal, D. J.

    1982-01-01

    The beta-adrenoceptor agonists, salbutamol, terbutaline and clenbuterol, were investigated for their effect on 5-hydroxytryptamine-mediated (5-HT) hyperactivity. 2 The lipophilic beta-adrenoceptor agonist, clenbuterol (5 mg/kg) enhanced the behaviours induced by quipazine (25 mg/kg), including headweaving, forepaw treading and hind-limb abduction and thus increased automated activity recording. Clenbuterol (5 mg/kg) also enhanced the hyperactivity syndrome produced by the 5-HT agonist, 5-methoxy N,N-dimethyltryptamine (2 mg/kg) and the combination of tranylcypromine (10 mg/kg) and L-tryptophan (50 mg/kg). Salbutamol and terbutaline potentiated quipazine-induced hyperactivity only when given at the higher dose of 20 mg/kg. 3 The effect of clenbuterol in enhancing quipazine hyperactivity was blocked by the centrally acting beta 1-adrenoceptor antagonist, metoprolol (5 mg/kg), but not by the beta 2-adrenoceptor antagonist, butoxamine (5 mg/kg) or the peripherally acting beta 1-adrenoceptor antagonist, atenolol (5 mg/kg). 4 Clenbuterol (5 mg/kg) did not enhance the circling responses produced by methamphetamine (0.5 mg/kg) in unilateral nigrostriatal-lesioned rats. 5 The results suggest that beta-adrenoceptor agonists in common with some established antidepressant treatments produce enhancement of 5-HT-mediated behavioural responses. PMID:6124294

  10. Portal veins of mice infected with Schistosoma mansoni exhibit an increased reactivity to 5-hydroxytryptamine.

    PubMed

    Silva, C L; Morel, N; Noël, F

    1998-01-01

    In chronic severe infection with Schistosoma mansoni, portal hypertension and related vascular alterations usually develop as a consequence of granulomatous response to eggs. In order to investigate a putative direct effect of worms on the reactivity of their host portal vein, mice infected only with male worms were used in the present study. An higher reactivity to 5-hydroxytryptamine (5-HT) characterized by an increase in the maximal contraction and sensitivity was observed in portal vein from infected mice compared to healthy mice. Blockade of NO-synthase with l-NAME induced a small increase in 5-HT potency in portal vein from non-infected mice without changing the amplitude of the contractions, whereas it did not alter the reactivity of veins from infected mice. The present results show that unisexual infection of mice with male S. mansoni increased the reactivity of the portal vein to 5-HT which seems to be partially related to an alteration in the nitric oxide release by endothelium.

  11. Increased reactivity to 5-hydroxytryptamine of portal veins from mice infected with Schistosoma mansoni.

    PubMed

    Silva, C L; Morel, N; Lenzi, H L; Noël, F

    1998-07-01

    In chronic severe infection with Schistosoma mansoni, portal hypertension accompanied by anatomical changes of the portal vasculature can develop as a consequence of granulomatous response to eggs. Mice infected unisexually with male worms were used in the present study in order to investigate a direct effect of worms on the reactivity of their host portal vein. A higher reactivity in the presence of 5-hydroxytryptamine (5-HT), but not in the presence of KCl 100 mM solution, was observed in portal vein from infected mice compared to healthy mice. It was characterized by an increase in the maximal contraction and sensitivity to 5-HT. Blockade of NO-synthase with N omega-nitro-L-arginine methyl ester (L-NAME) induced a small increase in 5-HT potency in the portal vein from non-infected mice, but did not change the amplitude of the contractions. In portal veins from infected mice, preincubation with L-NAME did not affect the reactivity to 5-HT. Histological analysis indicated endothelial damage, subendothelial fibrous plaques, and focal areas of inflammatory infiltrates in the adventitial layer. As a conclusion, these results show that unisexual infection of mice with male S. mansoni increased the reactivity of the portal vein to 5-HT which seems to be only partially related to an alteration in the endothelial production of nitric oxide.

  12. Kinetic characterization of 5-hydroxytryptamine receptor desensitization in isolated guinea-pig trachea and rabbit aorta.

    PubMed

    Ben-Harari, R R; Dalton, B A; Osman, R; Maayani, S

    1991-04-01

    Desensitization of the contractile response mediated by the 5-hydroxytryptamine2 (5-HT2) receptor in the isolated guinea-pig trachea and rabbit aorta is a time-dependent process and therefore it has been characterized by an apparent rate constant obtained from a kinetic analysis. Under similar conditions, desensitization of the response in the trachea is 7-fold faster than in the aorta. Desensitization is homologous and reversible and is not affected by inhibition of neuronal and extraneuronal uptake, monoamine oxidase activity, alpha 1 adrenergic, cholinergic muscarinic or histamine H1 receptors. Desensitization does not depend on removal of epithelium from the trachea or endothelium and adventitia from the aorta or on the release of a stable relaxant factor. It is also not affected by the removal of extracellular Ca++, which is needed for tonic contraction. The dependence of desensitization on agonist concentration, number of receptors and the intrinsic activity of the agonist was determined. The observed values of the rate constants for desensitization and of the peak tension (T peak) in trachea show a saturable dependence on the concentration of 5-HT, indicating that occupancy of the 5-HT2 receptor is needed for desensitization. The less efficacious agonists, N-methyl serotonin, dimethyltryptamine, quipazine, 5-methoxytryptamine, 5-methyltryptamine, 5-methoxy dimethyltryptamine, 4-hydroxytryptamine and bufotenine induce significantly slower desensitization than 5-HT. A 25 to 75% reduction in 5-HT2 receptor number by alkylation had no effect on the observed rate constants for desensitization.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. Selective 5-hydroxytryptamine2 receptor antagonists protect against the neurotoxicity of methylenedioxymethamphetamine in rats.

    PubMed

    Schmidt, C J; Abbate, G M; Black, C K; Taylor, V L

    1990-11-01

    The serotonergic deficits resulting from methylenedioxymethamphetamine (MDMA)-induced neurotoxicity were prevented by the simultaneous administration of 5-hydroxytryptamine2 (5-HT2) receptor antagonists such as MDL 11,939 or ritanserin. This effect was not region specific as protection was observed in the cortex, hippocampus and striatum 1 week after the administration of a single dose of MDMA. MDL 11,939 also showed some efficacy at reducing the deficits in 5-HT concentrations and tryptophan hydroxylase activity produced by multiple administrations of MDMA. Protection against the neurotoxicity required the administration of MDL 11,939 within 1 hr of MDMA indicating 5-HT2 receptor activation was an early event in the process leading to terminal damage. Examination of the effect of the 5-HT2 receptor blockade on the early neurochemical alterations induced by MDMA revealed an inhibitory effect on MDMA-stimulated dopamine synthesis. Analysis of these data and the associated changes in dopamine metabolites indicates that 5-HT2 receptor antagonists block MDMA-induced neurotoxicity by interfering with the ability of the dopamine neuron to maintain its cytoplasmic pool of transmitter and thereby sustain carrier-mediated dopamine release.

  14. Photoaffinity labeling of the 5-hydroxytryptamine 1A receptor in rat hippocampus.

    PubMed

    Ransom, R W; Asarch, K B; Shih, J C

    1986-10-01

    1-[2-(4-Azidophenyl)ethyl]-4-(3-trifluoromethylphenyl)piperazine (p-azido-PAPP) inhibits [3H]5-hydroxytryptamine [( 3H]5-HT) binding to 5-HT1A and 5-HT1B sites in rat brain with equilibrium dissociation constants (KD) of 0.9 nM and 230 nM, respectively. [3H]p-Azido-PAPP was synthesized and its reversible and irreversible binding properties to the hippocampal 5-HT1A site characterized. [3H]p-Azido-PAPP labeled a single class of sites in rat hippocampal membranes with a KD of 1 nM and a maximal binding density of 370 fmol/mg protein. The pharmacological profile of [3H]p-azido-PAPP binding was consistent with the radioligand's selective interaction with the 5-HT1A receptor. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of membranes preincubated with [3H]p-azido-PAPP and irradiated showed a major band of incorporation of radioactivity at approximately 55,000 daltons. This incorporation could be blocked when membranes were incubated with 1 microM of several agents that have high affinity for 5-HT1A sites [5-HT, 8-hydroxy-2-(di-n-propylamino)tetraline, TVX Q 7821, spiperone, buspirone, d-lysergic acid diethylamide, metergoline]. The results indicate that on photolysis [3H]p-azido-PAPP irreversibly labels a polypeptide that is, or is a subunit of, the 5-HT1A receptor in rat hippocampus.

  15. Skimmianine and related furoquinolines function as antagonists of 5-hydroxytryptamine receptors in animals.

    PubMed

    Cheng, J T; Chang, T K; Chen, I S

    1994-10-01

    1. Skimmianine, kokusaginine and confusameline, three furoquinolines extracted from the leaves of Evodia merrillii (Rutaceae), were investigated to characterize their selective effects on subtypes of 5-hydroxytryptamine (5-HT) receptors. 2. In the isolated membranes of rat cerebrocortex, using [3H]-5-HT and [3H]-ketanserin as radioligands, skimmianine and the two other furoquinolines displaced radioligand bindings in a concentration-dependent manner. Lower concentrations were required to affect [3H]-ketanserin binding than [3H]-5-HT binding in the order skimmianine > kokusaginine > confusameline. 3. Furoquinolines inhibited 5-HT-induced contraction mediated by 5-HT2 receptors in the presence of methiothepin in rat isolated aorta. Also, the combination of furoquinolines with ketanserin showed an additive antagonism. 4. These furoquinolines were inactive on the 5-carboxamidotryptamine-induced relaxation of guinea-pig ileum, a 5-HT1-mediated event. However, 5-HT-induced contraction via 5-HT2 receptors was reduced by these furoquinolines in a way similar to that in blood vessels. 5. The failure of these compounds to affect the 5-HT-induced Bezold-Jarisch-like reflex in anaesthetized rats, the major 5-HT3-mediated action, ruled out an action on 5-HT3 receptors. 6. The results obtained suggest that three furoquinoline alkaloids may act on 5-HT receptors in animals, more selectively to the 5-HT2 subtype, in the order of skimmianine > kokusaginine > confusameline.

  16. Does morphine enhance the release of 5-hydroxytryptamine in the rat spinal cord? An in vivo differential pulse voltammetry study.

    PubMed

    Chiang, C Y; Xiang, X K

    1987-05-19

    Differential pulse voltammetry used in combination with an electrochemically treated carbon fiber electrode allowed the detection of 5-hydroxyindoles (5-HI) in the dorsal horn of the urethane-anesthetized rat. Voltammograms were recorded every 3 min for up to 4 h. One component of the signal, peak 3, corresponding to 5-HI and uric acid was first identified separately in vitro as well as in vivo, and then further examined by means of systemic L- and D-trytophan administration and by local application of uricase, respectively. It was found that the height of peak 3 was unaffected by systemic morphine. Even following pretreatment with probenecid, the height of peak 3 was increased only 8.6-13.7% over that with saline, by morphine given either intraperitoneally or intracerebrally into the nucleus raphe magnus. However, these increments of peak 3 were not statistically significant. These findings suggest that the serotonin descending system is unlikely to play an important role in morphine analgesia.

  17. Activation of a Habenulo-Raphe Circuit Is Critical for the Behavioral and Neurochemical Consequences of Uncontrollable Stress in the Male Rat.

    PubMed

    Dolzani, Samuel D; Baratta, Michael V; Amat, Jose; Agster, Kara L; Saddoris, Michael P; Watkins, Linda R; Maier, Steven F

    2016-01-01

    Exposure to uncontrollable stress [inescapable tailshock (IS)] produces behavioral changes that do not occur if the stressor is controllable [escapable tailshock (ES)] an outcome that is mediated by greater IS-induced dorsal raphe nucleus (DRN) serotonin [5-hydroxytryptamine (5-HT)] activation. It has been proposed that this differential activation occurs because the presence of control leads to top-down inhibition of the DRN from medial prefrontal cortex (mPFC), not because uncontrollability produces greater excitatory input. Although mPFC inhibitory regulation over DRN 5-HT activation has received considerable attention, the relevant excitatory inputs that drive DRN 5-HT during stress have not. The lateral habenula (LHb) provides a major excitatory input to the DRN, but very little is known about the role of the LHb in regulating DRN-dependent behaviors. Here, optogenetic silencing of the LHb during IS blocked the typical anxiety-like behaviors produced by IS in male rats. Moreover, LHb silencing blocked the increase in extracellular basolateral amygdala 5-HT during IS and, surprisingly, during behavioral testing the following day. We also provide evidence that LHb-DRN pathway activation is not sensitive to the dimension of behavioral control. Overall, these experiments highlight a critical role for LHb in driving DRN activation and 5-HT release into downstream circuits that mediate anxiety-like behavioral outcomes of IS and further support the idea that behavioral control does not modulate excitatory inputs to the DRN.

  18. Activation of a Habenulo–Raphe Circuit Is Critical for the Behavioral and Neurochemical Consequences of Uncontrollable Stress in the Male Rat

    PubMed Central

    Baratta, Michael V.; Amat, Jose; Watkins, Linda R.

    2016-01-01

    Abstract Exposure to uncontrollable stress [inescapable tailshock (IS)] produces behavioral changes that do not occur if the stressor is controllable [escapable tailshock (ES)] an outcome that is mediated by greater IS-induced dorsal raphe nucleus (DRN) serotonin [5-hydroxytryptamine (5-HT)] activation. It has been proposed that this differential activation occurs because the presence of control leads to top–down inhibition of the DRN from medial prefrontal cortex (mPFC), not because uncontrollability produces greater excitatory input. Although mPFC inhibitory regulation over DRN 5-HT activation has received considerable attention, the relevant excitatory inputs that drive DRN 5-HT during stress have not. The lateral habenula (LHb) provides a major excitatory input to the DRN, but very little is known about the role of the LHb in regulating DRN-dependent behaviors. Here, optogenetic silencing of the LHb during IS blocked the typical anxiety-like behaviors produced by IS in male rats. Moreover, LHb silencing blocked the increase in extracellular basolateral amygdala 5-HT during IS and, surprisingly, during behavioral testing the following day. We also provide evidence that LHb–DRN pathway activation is not sensitive to the dimension of behavioral control. Overall, these experiments highlight a critical role for LHb in driving DRN activation and 5-HT release into downstream circuits that mediate anxiety-like behavioral outcomes of IS and further support the idea that behavioral control does not modulate excitatory inputs to the DRN. PMID:27785462

  19. Raphe nuclei in three cartilaginous fishes, Hydrolagus colliei, Heterodontus francisci, and Squalus acanthias.

    PubMed

    Stuesse, S L; Stuesse, D C; Cruce, W L

    1995-07-31

    The vertebrate reticular formation, containing over 30 nuclei in mammals, is a core brainstem area with a long evolutionary history. However, not all reticular nuclei are equally old. Nuclei that are widespread among the vertebrate classes are probably ones that evolved early. We describe raphe nuclei in the reticular formation of three cartilaginous fishes that diverged from a common ancestor over 350 million years ago. These fishes are Hydrolagus colliei, a holocephalan, Squalus acanthias, a small-brained shark, and Heterodontus francisci, a large-brained shark. Nuclear identification was based on immunohistochemical localization of serotonin and leu-enkephalin, on brainstem location, and on cytoarchitectonics. Raphe nuclei are clustered in inferior and superior cell groups, but within these groups individual nuclei can be identified: raphe pallidus, raphe obscurus, and raphe magnus in the inferior group and raphe pontis, raphe dorsalis, raphe centralis superior, and raphe linearis in the superior group. Hydrolagus lacked a dorsal raphe nucleus, but the nucleus was present in the sharks. The majority of immunoreactive cells are found in the superior group, especially in raphe centralis superior, but immunoreactive cells are present from spinal cord to caudal mesencephalon. The distribution and cytoarchitectonics of serotoninergic and enkephalinergic cells are similar to each other, but raphe nuclei contain fewer enkephalinergic than serotoninergic cells. The cytoarchitectonics of immunoreactive raphe cells in cartilaginous fishes are remarkably similar to those described for raphe nuclei in mammals; however, the lack of a raphe dorsalis in Hydrolagus indicates that either it evolved later than the other raphe nuclei or it was lost in holocephalan fishes.

  20. Cannabidiol, a non-psychotropic component of cannabis, attenuates vomiting and nausea-like behaviour via indirect agonism of 5-HT(1A) somatodendritic autoreceptors in the dorsal raphe nucleus.

    PubMed

    Rock, E M; Bolognini, D; Limebeer, C L; Cascio, M G; Anavi-Goffer, S; Fletcher, P J; Mechoulam, R; Pertwee, R G; Parker, L A

    2012-04-01

    To evaluate the hypothesis that activation of somatodendritic 5-HT(1A) autoreceptors in the dorsal raphe nucleus (DRN) produces the anti-emetic/anti-nausea effects of cannabidiol (CBD), a primary non-psychoactive cannabinoid found in cannabis. The potential of systemic and intra-DRN administration of 5-HT(1A) receptor antagonists, WAY100135 or WAY100635, to prevent the anti-emetic effect of CBD in shrews (Suncus murinus) and the anti-nausea-like effects of CBD (conditioned gaping) in rats were evaluated. Also, the ability of intra-DRN administration of CBD to produce anti-nausea-like effects (and reversal by systemic WAY100635) was assessed. In vitro studies evaluated the potential of CBD to directly target 5-HT(1A) receptors and to modify the ability of the 5-HT(1A) agonist, 8-OH-DPAT, to stimulate [(35) S]GTPγS binding in rat brainstem membranes. CBD suppressed nicotine-, lithium chloride (LiCl)- and cisplatin (20 mg·kg(-1) , but not 40 mg·kg(-1) )-induced vomiting in the S. murinus and LiCl-induced conditioned gaping in rats. Anti-emetic and anti-nausea-like effects of CBD were suppressed by WAY100135 and the latter by WAY100635. When administered to the DRN: (i) WAY100635 reversed anti-nausea-like effects of systemic CBD, and (ii) CBD suppressed nausea-like effects, an effect that was reversed by systemic WAY100635. CBD also displayed significant potency (in a bell-shaped dose-response curve) at enhancing the ability of 8-OH-DPAT to stimulate [(35) S]GTPγS binding to rat brainstem membranes in vitro. Systemically administered CBD and 8-OH-DPAT synergistically suppressed LiCl-induced conditioned gaping. These results suggest that CBD produced its anti-emetic/anti-nausea effects by indirect activation of the somatodendritic 5-HT(1A) autoreceptors in the DRN. This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of

  1. Order of application determines the interaction between phorbol esters and GTP-gamma-S in dorsal raphe neurons: evidence that the effect of 5-HT is modified upstream of the G protein Ca channel interaction.

    PubMed

    Chen, Y; Penington, N J

    1997-05-01

    Phorbol esters activating protein kinase C (PKC) partially uncouple the inhibitory effect of serotonin (5-HT) from serotonergic neuron Ca2+ current. Presently the site of action of PKC is not known and may be the receptor, G protein, or ion channel. We recorded Ca2+ current from acutely isolated neurons with the use of the patch-clamp technique to study the site of action of PKC. Activation of the G protein with internal guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S) occluded the response to 5-HT, but unexpectedly this effect was not reversed by the addition of the phorbol ester phorbol 12-myristate 13-acetate (PMA) despite the voltage-dependent reversal of the effect of GTP-gamma-S by long depolarizing steps to +80 mV. PMA was, however, able to partially reverse 5-HT-induced inhibition of Ca2+ current. The rate of reinhibition of the Ca2+ current (related to the concentration of activated G proteins) by GTP-gamma-S after the addition of PMA at -50 mV was identical to the rate when only GTP-gamma-S was present. By contrast, when cells were exposed first to PMA, and then GTP-gamma-S was perfused into the cell, GTP-gamma-S lost about half of its ability to activate the G protein. The rate of reinhibition of the Ca2+ current by internal GTP-gamma-S was also reduced in cells pretreated with PMA. The original result in which PMA did not reverse the action of GTP-gamma-S suggested that the channel was not the functional site of action of PMA, nor was the site on the G protein that binds to the channel, but it did not rule out the receptor. When the receptor was bypassed, after prior PKC activation, it was found that direct activation of the G protein by a nonhydrolyzable analogue of GTP was reduced; taken as a whole, this indicates that in dorsal raphe, and perhaps other neurons, the site of the critical phosphorylation may be on the G protein and possibly at the GTP binding site.

  2. Importance of phenylalanine 107 in agonist recognition by the 5-hydroxytryptamine(3A) receptor.

    PubMed

    Steward, L J; Boess, F G; Steele, J A; Liu, D; Wong, N; Martin, I L

    2000-06-01

    The 5-hydroxytryptamine (5-HT)(3) receptor is a member of the ligand-gated ion channel receptor family with significant homology to the nicotinic acetylcholine, gamma-aminobutyric acid(A), and glycine receptors. In this receptor class, the agonist binding site is formed by parts of the extracellular amino-terminal region. This study examines the effects of altering phenylalanine 107 (F107) of the 5-HT(3AL) subunit, obtained from NG108-15 cells, using site-directed mutagenesis. The wild-type (WT) and mutant receptors were expressed in HEK 293 cells and characterized using both whole-cell patch-clamp and radioligand binding. The tyrosine mutant F107Y exhibits a significantly lower affinity for the agonist 5-HT (K(i) = 203 versus 15.6 nM) and an increase of similar magnitude in the EC(50) value (10.6 versus 1.2 microM) compared with WT. The activation kinetics of the maximal currents generated by 5-HT with this mutant were markedly slower than those of the WT receptor, but application of supramaximal concentrations of the agonist markedly decreased the time to half-peak. The asparagine mutant F107N displayed a significantly higher affinity for 5-HT than the WT receptor (1.62 versus 15.6 nM), which was mirrored in direction and magnitude by changes in the EC(50) value for this agonist (0.2 versus 1.2 microM). In contrast to the WT receptor, the mutant F107N was activated by acetylcholine (EC(50) = 260 microM). The response to acetylcholine was blocked by the 5-HT(3) receptor antagonist renzapride with a similar IC(50) value as that determined against currents generated by 5-HT in the WT receptor. These data suggest that F107 is an important determinant of agonist recognition at the 5-HT(3) receptor.

  3. Potentiation of RSU-1069 tumour cytotoxicity by 5-hydroxytryptamine (5-HT).

    PubMed Central

    Chaplin, D. J.

    1986-01-01

    It is known that many solid animal tumours have a lower oxygenation level than most normal tissues and, in addition, that this level of oxygenation can be further decreased by systemic administration of 5-hydroxytryptamine (5-HT). The present study has investigated if such selective decrease in tumour oxygenation can be exploited by using the hypoxic cell cytotoxin, RSU-1069. The results obtained show that 5-HT at a dose of 5 mg kg-1, although not cytotoxic alone, can potentiate the cytotoxic effects of RSU-1069 in the Lewis lung carcinoma over the dose range 0.01-0.15 mg g-1. Maximum potentiation occurs when 5-HT is administered after RSU-1069. Potentiation of RSU-1069 cytotoxicity was observed using both the soft agar excision assay as an endpoint as well as in situ growth delay. In addition, the study shows that potentiation of RSU-1069 (0.1 mg g-1) cytotoxicity can be seen with 5-HT doses as low as 0.5 mg kg-1. In contrast to the tumour cytotoxicity results, 5-HT at a dose of 5 mg kg-1 i.p. did not affect the systemic toxicity, as measured by LD50/7d of RSU-1069. Thus, these results indicate that 5-HT can increase the therapeutic efficiency of RSU-1069. Such a finding is consistent with the rationale that selective reduction in tumour blood flow and oxygenation induced by 5-HT can be exploited using the hypoxic cell cytotoxin RSU-1069. PMID:3801269

  4. Peptide YY3–36 and 5-Hydroxytryptamine Mediate Emesis Induction by Trichothecene Deoxynivalenol (Vomitoxin)

    PubMed Central

    Pestka, James J.

    2013-01-01

    Deoxynivalenol (DON, vomitoxin), a trichothecene mycotoxin produced by Fusarium sp. that frequently occurs in cereal grains, has been associated with human and animal food poisoning. Although a common hallmark of DON-induced toxicity is the rapid onset of emesis, the mechanisms for this adverse effect are not fully understood. Recently, our laboratory has demonstrated that the mink (Neovison vison) is a suitable small animal model for investigating trichothecene-induced emesis. The goal of this study was to use this model to determine the roles of two gut satiety hormones, peptide YY3–36 (PYY3–36) and cholecystokinin (CCK), and the neurotransmitter 5-hydroxytryptamine (5-HT) in DON-induced emesis. Following ip exposure to DON at 0.1 and 0.25mg/kg bw, emesis induction ensued within 15–30min and then persisted up to 120min. Plasma DON measurement revealed that this emesis period correlated with the rapid distribution and clearance of the toxin. Significant elevations in both plasma PYY3–36 (30–60min) and 5-HT (60min) but not CCK were observed during emesis. Pretreatment with the neuropeptide Y2 receptor antagonist JNJ-31020028 attenuated DON- and PYY-induced emesis, whereas the CCK1 receptor antagonist devezapide did not alter DON’s emetic effects. The 5-HT3 receptor antagonist granisetron completely suppressed induction of vomiting by DON and the 5-HT inducer cisplatin. Granisetron pretreatment also partially blocked PYY3–36-induced emesis, suggesting a potential upstream role for this gut satiety hormone in 5-HT release. Taken together, the results suggest that both PYY3–36 and 5-HT play contributory roles in DON-induced emesis. PMID:23457120

  5. Peptide displacement of ( sup 3 H)5-hydroxytryptamine binding to bovine cortical membranes

    SciTech Connect

    Takeuchi, Y.; Root-Bernstein, R.S.; Shih, J.C. )

    1990-12-01

    Chemical studies have demonstrated that peptides such as the encephalitogenic (EAE) peptide of myelin basic protein (MBP) and luteinizing hormone-releasing hormone (LHRH) can bind serotonin (5-hydroxytryptamine, 5-HT) in vitro. The present research was undertaken to determine whether such binding interferes with 5-HT binding to its 5-HT1 receptors on bovine cerebral cortical membranes. EAE peptide and LHRH displaced ({sup 3}H)5-HT with IC50s of 4.0 x 10(-4) and 1.8 x 10(-3) M respectively. MBP itself also showed apparent displacing ability with an IC50 of 6.0 x 10(-5) M, though it also caused aggregation of cortical membranes that might have interfered with normal receptor binding. These results support previous suggestions that the tryptophan peptide region of MBP may act as a 5-HT receptor in the neural system. We also tested the effects of muramyl dipeptide (N-acetyl-muramyl-L-Ala-D-isoGln, MD), a bacterial cell-wall breakdown product that acts as a slow-wave sleep promoter, binds to LHRH and EAE peptide, and competes for 5-HT binding sites on macrophages. It showed no significant displacement of 5-HT binding to cortical membranes (IC50 greater than 10(-1) M), but its D-Ala analogue did (IC50 = 1.7 x 10(-3) M). Thus, it seems likely that the 5-HT-related effects of naturally occurring muramyl peptides are physiologically limited by receptor types.

  6. Antidepressant drugs inhibit a glial 5-hydroxytryptamine transporter in rat brain.

    PubMed

    Bal, N; Figueras, G; Vilaró, M T; Suñol, C; Artigas, F

    1997-08-01

    We assessed the role of glial cells in the uptake of serotonin (5-hydroxytryptamine, 5-HT). Primary cultures of rat and mouse cortical astrocytes took up and deaminated 5-HT. The antidepressants citalopram, clomipramine, fluoxetine, fluvoxamine, paroxetine and sertraline inhibited this process. The presence of the mRNAs for the 5-HT transporter and monoamine oxidase-A (MOA-A) was established in cultured astrocytes and in adult rat brain areas with (midbrain and brainstem) and without (frontal cortex) serotonergic cell bodies after reverse transcription-polymerase chain reaction and hybridization with probes complementary to the cloned neuronal 5-HT transporter and MAO-A. To examine in vivo the role of astrocytes in the elimination of 5-HT from the extracellular brain space, 5-HT was perfused through dialysis probes implanted in the frontal cortex of conscious rats and its concentration was measured at the probe outlet. Tissue 5-HT recovery was dose-dependently inhibited by the concurrent perfusion of citalopram, fluoxetine and paroxetine, showing that it essentially measured uptake through the high-affinity 5-HT transporter. Rats lesioned with 5,7-dihydroxytryptamine (5,7-DHT; 88% reduction of tissue 5-HT) displayed tissue 5-HT recovery slightly higher than sham-operated rats (55 +/- 2 vs. 46 +/- 3%, P < 0.001), a finding perhaps attributable to the astrogliosis induced by 5,7-DHT denervation. Rats lesioned with 6-hydroxydopamine showed tissue 5-HT uptake similar to controls, suggesting negligible reuptake of 5-HT by catecholaminergic terminals. These results are consistent with the presence of a glial component of 5-HT uptake in the rodent brain, sensitive to antidepressants, which takes place through a 5-HT transporter very similar or identical to that present in neurons.

  7. 5-Hydroxytryptamine does not reduce sympathetic nerve activity or neuroeffector function in the splanchnic circulation

    PubMed Central

    Darios, Emma S.; Barman, Susan M.; Orer, Hakan S.; Morrison, Shaun F.; Davis, Robert P.; Seitz, Bridget M.; Burnett, Robert; Watts, Stephanie W.

    2015-01-01

    Infusion of 5-hydroxytryptamine (5-HT) in conscious rats results in a sustained (up to 30 days) fall in blood pressure. This is accompanied by an increase in splanchnic blood flow. Because the splanchnic circulation is regulated by the sympathetic nervous system, we hypothesized that 5-HT would: 1) directly reduce sympathetic nerve activity in the splanchnic region; and/or 2) inhibit sympathetic neuroeffector function in splanchnic blood vessels. Moreover, removal of the sympathetic innervation of the splanchnic circulation (celiac ganglionectomy) would reduce 5-HT-induced hypotension. In anaesthetized Sprague-Dawley rats, mean blood pressure was reduced from 101 ± 4 to 63 ± 3 mm Hg during slow infusion of 5-HT (25 μg/kg/min, i.v.). Pre- and postganglionic splanchnic sympathetic nerve activity was unaffected during 5-HT infusion. In superior mesenteric arterial rings prepared for electrical field stimulation, neither 5-HT (3, 10, 30 nM), the 5-HT1B receptor agonist CP 93129 nor 5-HT1/7 receptor agonist 5-carboxamidotryptamine inhibited neurogenic contraction compared to vehicle. 5-HT did not inhibit neurogenic contraction in superior mesenteric venous rings. Finally, celiac ganglionectomy did not modify the magnitude of fall or time course of 5-HT-induced hypotension when compared to animals receiving sham ganglionectomy. We conclude it is unlikely 5-HT interacts with the sympathetic nervous system at the level of the splanchnic preganglionic or postganglionic nerve, as well as at the neuroeffector junction, to reduce blood pressure. These important studies allow us to rule out a direct interaction of 5-HT with the splanchnic sympathetic nervous system as a cause of the 5-HT-induced fall in blood pressure. PMID:25732865

  8. An electrophysiological study of 5-hydroxytryptamine receptors of neurones in the molluscan nervous system

    PubMed Central

    Gerschenfeld, H. M.; Stefani, E.

    1966-01-01

    1. 5-Hydroxytryptamine (5-HT) has been iontophoretically applied to the membrane of central neurones of Cryptomphallus aspersa; CILDA neurones (cells with inhibition of long duration) (Gerschenfeld & Tauc, 1964) are the only cells sensitive to 5-HT. The responses to 5-HT is always a depolarization. The CILDA cells studied were also depolarized by ACh. 2. From experiments in which pulses of 5-HT and ACh were applied from a double-barrelled micropipette to the CILDA cell soma, it has been calculated that 5-HT and ACh receptors were located at different distances from the injecting micropipette tip. It has also been calculated from the diffusion equation that in the same CILDA cell a 5-HT concentration of 8·2 × 10-9 M and a ACh concentration of 1·3 × 10-8 M caused a similar peak depolarization. 3. CILDA neurones show `anomalous' rectification. 5-HT increases the membrane conductance of CILDA. 4. 5-HT receptors of CILDA neurone are desensitized by repeated application of 5-HT. The desensitization lasts for ca. 40 sec. 5. 5-HT receptors are blocked by lysergic acid diethylamide and its derivatives. Morphine chlorhydrate blocks them non-competitively. 6. Some inhibitors of monoamine oxidase (trancylpromine, isocarboxazide, iproniazide and nialamide) have been tested. They do not prolong the action of 5-HT, but block the 5-HT receptors. 7. No crossed desensitization between 5-HT and ACh has been observed. Atropine blocks both ACh-receptors and 5-HT receptors, 5-HT receptors appear to be blocked to a greater extent. 8. The data presented support the assumption of a excitatory transmitter role of 5-HT to CILDA neurones, but further evidence is necessary to confirm this hypothesis. PMID:5918062

  9. Ethanol Stabilizes the Open State of Single 5-Hydroxytryptamine3A(QDA) Receptors

    PubMed Central

    Feinberg-Zadek, Paula L.

    2010-01-01

    Ethanol enhancement of 5-hydroxytryptamine (5-HT)3A receptor-mediated responses may have important consequences in the intoxicating and addictive properties of ethanol. Although the exact mechanism is unknown, ethanol-mediated enhancement of 5-HT3 receptor current has been proposed to occur due to stabilization of the open-channel state. It has not been possible to directly measure the open state of the channel due to the extremely low single-channel conductance of 5-HT3A channels. Recently, three arginine residues within the large intracellular loop of the 5-HT3A subunit were substituted by their equivalent residues (glutamine, aspartate, and alanine) of the 5-HT3B subunit to produce a 5-HT3A(QDA) subunit that forms functional homomeric channels exhibiting a measurable single-channel conductance. Using whole-cell rapid-agonist application techniques and the cell-attached single-channel recording configuration, we examined human 5-HT3A(QDA) receptors expressed in human embryonic kidney 293 cells. The agonist sensitivity, macroscopic kinetics, and modulation by ethanol were similar between mutant and wild-type channels, suggesting the substitutions had not altered these channel structure-function properties. The open time histogram for single-channel events mediated by 5-HT3A(QDA) receptors in the presence of maximal 5-HT was best fit by three exponentials, but in the presence of ethanol a fourth open state was evident. In summary, the QDA substitution greatly enhanced single-channel conductance with little effect on 5-HT3A channel's kinetic properties and ethanol enhances agonist action on 5-HT3A receptors by inducing a new, long-lived open-channel state. Furthermore, the 5-HT3A(QDA) receptor appears to be suitable for pharmacological studies of 5-HT3A receptor modulation at a single-channel level. PMID:20200118

  10. Nelotanserin, a novel selective human 5-hydroxytryptamine2A inverse agonist for the treatment of insomnia.

    PubMed

    Al-Shamma, Hussien A; Anderson, Christen; Chuang, Emil; Luthringer, Remy; Grottick, Andrew J; Hauser, Erin; Morgan, Michael; Shanahan, William; Teegarden, Bradley R; Thomsen, William J; Behan, Dominic

    2010-01-01

    5-Hydroxytryptamine (5-HT)(2A) receptor inverse agonists are promising therapeutic agents for the treatment of sleep maintenance insomnias. Among these agents is nelotanserin, a potent, selective 5-HT(2A) inverse agonist. Both radioligand binding and functional inositol phosphate accumulation assays suggest that nelotanserin has low nanomolar potency on the 5-HT(2A) receptor with at least 30- and 5000-fold selectivity compared with 5-HT(2C) and 5-HT(2B) receptors, respectively. Nelotanserin dosed orally prevented (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI; 5-HT(2A) agonist)-induced hypolocomotion, increased sleep consolidation, and increased total nonrapid eye movement sleep time and deep sleep, the latter marked by increases in electroencephalogram (EEG) delta power. These effects on rat sleep were maintained after repeated subchronic dosing. In healthy human volunteers, nelotanserin was rapidly absorbed after oral administration and achieved maximum concentrations 1 h later. EEG effects occurred within 2 to 4 h after dosing, and were consistent with vigilance-lowering. A dose response of nelotanserin was assessed in a postnap insomnia model in healthy subjects. All doses (up to 40 mg) of nelotanserin significantly improved measures of sleep consolidation, including decreases in the number of stage shifts, number of awakenings after sleep onset, microarousal index, and number of sleep bouts, concomitant with increases in sleep bout duration. Nelotanserin did not affect total sleep time, or sleep onset latency. Furthermore, subjective pharmacodynamic effects observed the morning after dosing were minimal and had no functional consequences on psychomotor skills or memory. These studies point to an efficacy and safety profile for nelotanserin that might be ideally suited for the treatment of sleep maintenance insomnias.

  11. The effect of fasting on 5-hydroxytryptamine metabolism in brain regions of the albino rat.

    PubMed Central

    Fuenmayor, L. D.; García, S.

    1984-01-01

    The turnover of 5-hydroxytryptamine (5-HT) in the whole brain and different brain regions was studied in rats fasted for 24 h. These rats showed an increased tissue concentration of the amine in the whole brain and of its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the whole brain, the striatum, the combined pons-medulla and the cerebral cortex. The accumulation of 5-HIAA after probenecid was increased by fasting in the regions mentioned above except for the striatum. The effect of probenecid was also increased by fasting in the midbrain, the hypothalamus and the hippocampus. In the striatum, the administration of probenecid produced a smaller increase in 5-HIAA concentration in fasted than in fed rats. The decay of 5-HT following p-chlorophenylalanine (PCPA) was increased in the hypothalamus of fasted rats at 16 h, but not at 4 h, after the intraperitoneal administration of the inhibitor. In the midbrain, the striatum and the combined pons-medulla, food deprivation did not modify the decrease induced by PCPA. However, the inhibitor induced a reduction of food consumption in the fed group, which made this group rather similar to the fasted one and complicated the interpretation of the results in these last three cerebral areas. Our results confirm that food deprivation increases the turnover of brain 5-HT and point out that the increase probably occurs in all brain areas. This increased turnover appears to be accompanied, in the hypothalamus, by an increased neuronal release of the amine. In the striatum, fasting probably blocks the active transport system which removes acid metabolites from the brain. PMID:6207885

  12. 5-Hydroxytryptamine does not reduce sympathetic nerve activity or neuroeffector function in the splanchnic circulation.

    PubMed

    Darios, Emma S; Barman, Susan M; Orer, Hakan S; Morrison, Shaun F; Davis, Robert P; Seitz, Bridget M; Burnett, Robert; Watts, Stephanie W

    2015-05-05

    Infusion of 5-hydroxytryptamine (5-HT) in conscious rats results in a sustained (up to 30 days) fall in blood pressure. This is accompanied by an increase in splanchnic blood flow. Because the splanchnic circulation is regulated by the sympathetic nervous system, we hypothesized that 5-HT would: 1) directly reduce sympathetic nerve activity in the splanchnic region; and/or 2) inhibit sympathetic neuroeffector function in splanchnic blood vessels. Moreover, removal of the sympathetic innervation of the splanchnic circulation (celiac ganglionectomy) would reduce 5-HT-induced hypotension. In anaesthetized Sprague-Dawley rats, mean blood pressure was reduced from 101±4 to 63±3mm Hg during slow infusion of 5-HT (25μg/kg/min, i.v.). Pre- and postganglionic splanchnic sympathetic nerve activity were unaffected during 5-HT infusion. In superior mesenteric arterial rings prepared for electrical field stimulation, neither 5-HT (3, 10, 30nM), the 5-HT1B receptor agonist CP 93129 nor 5-HT1/7 receptor agonist 5-carboxamidotryptamine inhibited neurogenic contraction compared to vehicle. 5-HT did not inhibit neurogenic contraction in superior mesenteric venous rings. Finally, celiac ganglionectomy did not modify the magnitude of fall or time course of 5-HT-induced hypotension when compared to animals receiving sham ganglionectomy. We conclude it is unlikely 5-HT interacts with the sympathetic nervous system at the level of the splanchnic preganglionic or postganglionic nerve, as well as at the neuroeffector junction, to reduce blood pressure. These important studies allow us to rule out a direct interaction of 5-HT with the splanchnic sympathetic nervous system as a cause of the 5-HT-induced fall in blood pressure. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Upregulation of 5-Hydroxytryptamine Receptor Signaling in Coronary Arteries after Organ Culture

    PubMed Central

    Rao, Fang; Xue, Yu-Mei; Zhou, Zhi-Ling; Liu, Xiao-Ying; Shan, Zhi-Xin; Li, Xiao-Hong; Lin, Qiu-Xiong; Wu, Shu-Lin; Yu, Xi-Yong

    2014-01-01

    Background 5-Hydroxytryptamine (5-HT) is a powerful constrictor of coronary arteries and is considered to be involved in the pathophysiological mechanisms of coronary-artery spasm. However, the mechanism of enhancement of coronary-artery constriction to 5-HT during the development of coronary artery disease remains to be elucidated. Organ culture of intact blood-vessel segments has been suggested as a model for the phenotypic changes of smooth muscle cells in cardiovascular disease. Methodology/Principal Findings We wished to characterize 5-HT receptor-induced vasoconstriction and quantify expression of 5-HT receptor signaling in cultured rat coronary arteries. Cumulative application of 5-HT produced a concentration-dependent vasoconstriction in fresh and 24 h-cultured rat coronary arteries without endothelia. 5-HT induced greater constriction in cultured coronary arteries than in fresh coronary arteries. U46619- and CaCl2-induced constriction in the two groups was comparable. 5-HT stimulates the 5-HT2A receptor and cascade of phospholipase C to induce coronary vasoconstriction. Calcium influx through L-type calcium channels and non-L-type calcium channels contributed to the coronary-artery constrictions induced by 5-HT. The contractions mediated by non-L-type calcium channels were significantly enhanced in cultured coronary arteries compared with fresh coronary arteries. The vasoconstriction induced by thapsigargin was also augmented in cultured coronary arteries. The decrease in Orai1 expression significantly inhibited 5-HT-evoked entry of Ca2+ in coronary artery cells. Expression of the 5-HT2A receptor, Orai1 and STIM1 were augmented in cultured coronary arteries compared with fresh coronary arteries. Conclusions An increased contraction in response to 5-HT was mediated by the upregulation of 5-HT2A receptors and downstream signaling in cultured coronary arteries. PMID:25202989

  14. Inhibition by 5-hydroxytryptamine and noradrenaline in substantia gelatinosa of guinea-pig spinal trigeminal nucleus.

    PubMed

    Grudt, T J; Williams, J T; Travagli, R A

    1995-05-15

    1. Whole-cell and intracellular recordings were made from neurons in slices of guinea-pig spinal trigeminal nucleus pars caudalis. 2. 5-Hydroxytryptamine (5-HT) hyperpolarized 70% of neurons by activating 5-HT1A receptors. The effect was mimicked by 5-carboxamidotryptamine (5-CT) and (+/-)-2-dipropylamino-8-hydroxy-1,2,3,4-tetrahydronapthalene hydrobromide (8-OH-DPAT) and antagonized by 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)-butyl]-piperazine hydrobromide (NAN 190) and pindobind-5-HT1A. Nine per cent of the neurons were depolarized by 5-HT. 3. In about 20% of recordings, 5-HT also evoked repetitive inhibitory postsynaptic potentials that were mediated by glycine. 4. Noradrenaline (NA) hyperpolarized 71% of neurons. This effect was mediated by activation of alpha 2-adrenoceptors, since 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine (UK14304) also caused a hyperpolarization and idazoxan (1 microM) blocked the hyperpolarization to both NA and UK14304. Phenylephrine depolarized a subset of neurons and this depolarization was blocked by prazosin, suggesting an action mediated by activation of alpha 1-adrenoceptors. 5. NA also evoked repetitive GABAA-mediated inhibitory postsynaptic potentials in about 20% of recordings. The increase in synaptic activity was mimicked by phenylephrine and blocked by prazosin. 6. These results indicate that there are at least two mechanisms through which 5-HT and NA inhibit neurons: (i) in many cells both 5-HT and NA mediate a hyperpolarization through an increase of a potassium conductance; (ii) 5-HT and NA also activated GABA- and glycine-containing interneurons to cause IPSPs in separate groups of cells.

  15. TRPA1, substance P, histamine and 5-hydroxytryptamine interact in an interdependent way to induce nociception.

    PubMed

    Fischer, Luana; Lavoranti, Maria Isabel; de Oliveira Borges, Mariana; Miksza, Alana Farias; Sardi, Natalia Fantin; Martynhak, Bruno Jacson; Tambeli, Claudia H; Parada, Carlos Amílcar

    2017-04-01

    Although TRPA1, SP, histamine and 5-hydroxytryptamine (5-HT) have recognized contribution to nociceptive mechanisms, little is known about how they interact with each other to mediate inflammatory pain in vivo. In this study we evaluated whether TRPA1, SP, histamine and 5-HT interact, in an interdependent way, to induce nociception in vivo. The subcutaneous injection of the TRPA1 agonist allyl isothiocyanate (AITC) into the rat's hind paw induced a dose-dependent and short lasting behavioral nociceptive response that was blocked by the co-administration of the TRPA1 antagonist, HC030031, or by the pretreatment with antisense ODN against TRPA1. AITC-induced nociception was significantly decreased by the co-administration of selective antagonists for the NK1 receptor for substance P, the H1 receptor for histamine and the 5-HT1A or 3 receptors for 5-HT. Histamine- or 5-HT-induced nociception was decreased by the pretreatment with antisense ODN against TRPA1. These findings suggest that AITC-induced nociception depends on substance P, histamine and 5-HT, while histamine- or 5-HT-induced nociception depends on TRPA1. Most important, AITC interact in a synergistic way with histamine, 5-HT or substance P, since their combination at non-nociceptive doses induced a nociceptive response much higher than that expected by the sum of the effect of each one alone. This synergistic effect is dependent on the H1, 5-HT1A or 3 receptors. Together, these findings suggest a self-sustainable cycle around TRPA1, no matter where the cycle is initiated each step is achieved and even subeffective activation of more than one step results in a synergistic activation of the overall cycle.

  16. Kinetics of competitive drug action at 5-hydroxytryptamine2 receptors in isolated rabbit aorta.

    PubMed

    Clancy, B M; Osman, R; Maayani, S

    1987-07-01

    The kinetics of agonist and antagonist interactions with the 5-hydroxytryptamine2 receptor were studied in the isolated rabbit aorta by following the antagonist-induced decrease in the steady-state response to an agonist. A model describing the competitive drug-receptor interactions was fitted to the data and yielded estimates of the association and dissociation rate constants of the agonist and the antagonist. A high concentration of the agonist ([agonist] much greater than KA) was used to reduce the influence of antagonist diffusion to the receptor upon the onset of antagonism. The effect of a diffusion barrier was evaluated by comparing the kinetics of drug competition in the absence and in the presence of the adventitia. The rate constants of the high-affinity antagonists spiperone, methysergide or ketanserin were similar in the absence and in the presence of the adventitia. In contrast, the rate constants of the low affinity antagonist 5-methoxygramine were reduced almost 5-fold in the presence of the adventitia. This observation may be explained by the large partition coefficients of the high-affinity antagonists as compared to the relatively low partition coefficient of 5-methoxygramine. The ratios of the estimated rate constants (k-x/kx) are in good agreement with the dissociation constants of the drugs determined with steady-state methods. In addition the results suggest that the association rate constant is a primary determinant of drug affinity for the receptor. The kinetic rate constants of the high-affinity antagonists measured in this preparation are similar to those previously reported in high-affinity binding studies. We conclude that the kinetic parameters obtained in our experiments reflect primarily the molecular interactions of these drugs with the receptor.

  17. Signal transduction differences between 5-hydroxytryptamine type 2A and type 2C receptor systems.

    PubMed

    Berg, K A; Clarke, W P; Sailstad, C; Saltzman, A; Maayani, S

    1994-09-01

    The cDNAs for human 5-hydroxytryptamine (5-HT)2C and 5-HT2A receptors were stably transfected separately into parent Chinese hamster ovary cells, and cell lines in which levels of transfected receptor protein expression and accumulation of inositol phosphates in response to 5-HT were comparable were chosen for study. The effect of activation of these receptors on 5-HT1B-like receptor-mediated responsiveness (i.e., inhibition of forskolin-stimulated cAMP accumulation) was studied. Activation of 5-HT2C receptors with 5-HT (0.1-100 microM) abolished the 5-HT1B-like response, which returned when 5-HT2C receptors were blocked with mesulergine (1 microM). Furthermore, the maximal response to 5-carboxytryptamine was reduced in a concentration-dependent manner by the 5-HT2A/5-HT2C-selective partial agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane. In contrast, activation of 5-HT2A receptors with either 5-HT or (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane did not alter the 5-HT1B-like response. The reduction of 5-HT1B-like responsiveness produced by 5-HT2C receptor activation was independent of protein kinase C activation and increases in the intracellular calcium concentration. Although 5-HT2A and 5-HT2C receptors are strikingly similar in structure and pharmacology, and the signal transduction systems coupled to these receptors have been thought to be similar, if not identical, these data provide the first evidence for fundamental differences in the signal transduction systems of these 5-HT2 receptor subtypes.

  18. Lamotrigine, carbamazepine and phenytoin differentially alter extracellular levels of 5-hydroxytryptamine, dopamine and amino acids.

    PubMed

    Ahmad, Shagufta; Fowler, Leslie J; Whitton, Peter S

    2005-02-01

    We have studied the effects of treatment with the anticonvulsants lamotrigine (LTG), phenytoin (PHN) and carbamazepine (CBZ) on basal and stimulated extracellular aspartate (ASP), glutamate (GLU), taurine (TAU), GABA, 5-hydroxytryptamine (5-HT) and dopamine (DA) in the hippocampus of freely moving rats using microdialysis. All of the drugs investigated have had inhibition of Na(+) channel activity implicated as their principal mechanism of action. Neither LTG (10-20 mg/kg), PHN (20-40 mg/kg) or CBZ (10-20 mg/kg) had an effect on the basal extracellular concentrations of any of the amino acids studied with the exception of glutamate, which was decreased at the highest LTG dose. However, when amino acid transmitter levels were increased with 50 microM veratridine, LTG was found to cause a dose-dependent decrease in dialysate levels of all four amino acids, with the effect being most pronounced for glutamate. In contrast, PHN decreased extracellular aspartate levels but had no effect on evoked-extracellular GLU, TAU or GABA. Somewhat unexpectedly, CBZ did not alter the stimulated increase in the excitatory amino acids, GLU and ASP, but, rather surprisingly for an antiepileptic drug, markedly decreased that of the inhibitory substances TAU and GABA. The three drugs had differing effects on basal extracellular 5-HT and DA. LTG caused a dose-dependent decrease in both, while CBZ and PHN both increased extracellular 5-HT and DA. When extracellular 5-HT and DA was evoked by veratridine LTG had no significant effect on this, while PHN but not CBZ increased stimulated extracellular 5-HT and both PHN and CBZ augmented DA. Thus, the effects of the three drugs studied seemed to depend on whether extracellular transmitter levels are evoked or basal and the particular transmitter in question. This suggests that there are marked differences in the neurochemical mechanisms of antiepileptic drug action of the three compounds studied.

  19. Identification of 5-hydroxytryptamine1D binding sites in sheep caudate nucleus membranes.

    PubMed

    Pauwels, P J; Palmier, C; Briley, M

    1993-08-03

    Radioligand binding measurements were performed in membranes of sheep caudate nucleus using [3H]5-hydroxytryptamine (5-HT). [3H]5-HT labeled a population of high affinity binding sites with a Kd of 1.9 +/- 0.1 nM and a Bmax of 19.8 +/- 2.2 fmol/mg tissue. Combined 5-HTID/E binding sites were the predominant 5-HT1 subtype, accounting for 78% of the total population of 5-HT1 binding sites. 5-Carboxamidotryptamine (5-CT) and sumatriptan yielded inhibition curves which best fitted a two-site model with high affinity values of 0.8 and 10.1 nM, and 1000 and 206 nM for their low affinity components. The proportion of the high affinity 5-CT and sumatriptan binding sites was 79 and 72%. The binding affinity profile of 5-HT1D binding sites [5-CT > 5-HT > d-LSD > 5-MeOT > sumatriptan > RU 24,969 > metergoline > tryptamine = rauwolscine = methylsergide > yohimbine = methiothepin > TFMPP = 8-OH-DPAT > 2-methyl-5-HT > mCPP = quipazine = CP 93,129 > ketanserin > (-)-propranolol = haloperidol = ipsapirone] compares well to that reported for 5-HT1D receptor sites in human caudate and cortex (correlation coefficient: 0.99 and 0.98). The present results indicate that sheep caudate nucleus is a valid tissue for studying interaction of compounds with 5-HT1D binding sites in the relative absence of 5-HT1E binding sites.

  20. The 5-hydroxytryptamine 4 Receptor Agonist-induced Actions and Enteric Neurogenesis in the Gut

    PubMed Central

    Goto, Kei; Kawahara, Isao

    2014-01-01

    We explored a novel effect of 5-hydroxytryptamine 4 receptor (5-HT4R) agonists in vivo to reconstruct the enteric neural circuitry that mediates a fundamental distal gut reflex. The neural circuit insult was performed in guinea pigs and rats by rectal transection and anastomosis. A 5-HT4R-agonist, mosapride citrate (MOS) applied orally and locally at the anastomotic site for 2 weeks promoted the regeneration of the impaired neural circuit or the recovery of the distal gut reflex. MOS generated neurofilament-, 5-HT4R- and 5-bromo-2'-deoxyuridine-positive cells and formed neural network in the granulation tissue at the anastomosis. Possible neural stem cell markers increased during the same time period. These novel actions by MOS were inhibited by specific 5-HT4R-antagonist such as GR113808 (GR) or SB-207266. The activation of enteric neural 5-HT4R promotes reconstruction of an enteric neural circuit that involves possibly neural stem cells. We also succeeded in forming dense enteric neural networks by MOS in a gut differentiated from mouse embryonic stem cells. GR abolished the formation of enteric neural networks. MOS up-regulated the expression of mRNA of 5-HT4R, and GR abolished this upregulation, suggesting MOS differentiated enteric neural networks, mediated via activation of 5-HT4R. In the small intestine in H-line: Thy1 promoter green fluorescent protein (GFP) mice, we obtained clear 3-dimensional imaging of enteric neurons that were newly generated by oral application of MOS after gut transection and anastomosis. All findings indicate that treatment with 5-HT4R-agonists could be a novel therapy for generating new enteric neurons to rescue aganglionic disorders in the whole gut. PMID:24466442

  1. An update on the role of the 5-hydroxytryptamine6 receptor in cognitive function.

    PubMed

    Fone, Kevin C F

    2008-11-01

    As the 5-hydroxytryptamine(6) (5-HT(6)) receptor is almost exclusively expressed in the CNS, particularly in areas associated with learning and memory, many studies have examined its role in cognitive function in the rodent, as reviewed herein. Most studies, in healthy adult rats, report that 5-HT(6) receptor antagonists enhance retention of spatial learning in the Morris water maze, improve consolidation in autoshaping tasks and reverse natural forgetting in object recognition. Antagonists appear to facilitate both cholinergic and glutamatergic neurotransmission, reversing scopolamine- and NMDA receptor antagonist-induced memory impairments. Recent reports show that the 5-HT(6) receptor antagonist, PRX-07034, restores the impairment of novel object recognition produced in rats reared in social isolation, a neurodevelopmental model producing behavioural changes similar to several core symptoms seen in schizophrenia. The 5-HT(6) receptor antagonist, Ro 04-6790, modestly improved reversal learning in isolation reared but not group-housed controls in the water maze. Ro 04-6790 also improved novel object discrimination both in adult rats that received chronic intermittent phencyclidine and drug-naïve 18-month-old rats. However, more information on their effect in animal models of schizophrenia and Alzheimer's disease is required. Several selective high-affinity 5-HT(6) receptor agonists developed recently also improve object discrimination and extra-dimensional set-shifting behaviour. Thus both 5-HT(6) receptor agonist and antagonist compounds show promise as pro-cognitive agents in pre-clinical studies but the explanation for their paradoxical analogous effect is currently unclear, and is discussed in this article.

  2. Potentiation by endothelin-1 of 5-hydroxytryptamine-induced contraction in coronary artery of the pig.

    PubMed Central

    Nakayama, K.; Ishigai, Y.; Uchida, H.; Tanaka, Y.

    1991-01-01

    1. In order to elucidate the physiological and potential pathological roles of endothelin-1 (ET-1) in coronary artery contraction and relaxation, we undertook the present study to examine the action of ET-1 itself, and the combined effects of ET-1 with vasoconstrictor agonists such as acetylcholine (ACh), histamine, and 5-hydroxytryptamine (5-HT), all of which have been implicated in the genesis of coronary spasm. 2. Isometric tension and cytosolic Ca2+ concentration ([Ca2+]i) in a ring segment of porcine coronary artery loaded with fura-2 were measured simultaneously. 3. ET-1 contracted the artery in a concentration-dependent manner; and nisoldipine, a Ca2+ channel blocking drug of the 1,4-dihydropyridine type, antagonized the ET-1 action non-competitively. A radio-receptor binding assay also indicated the mutually exclusive binding of ET-1 and (+)-[3H]-PN200-110, a Ca2+ channel ligand, to the membrane fraction of porcine coronary artery. 4. ET-1 (10-100 pM) increased tension and [Ca2+]i in a parallel manner, while at higher concentrations (1-10 nM) it produced further contraction with a small increase in [Ca2+]i. 5. ET-1 (30-100 pM) selectively potentiated the 5-HT-induced contraction 1.5 to 2 times over the control without causing a significant increase in [Ca2+]i, which seems to be qualitatively similar to a tumour promoting phorbol ester, 12-deoxyphorbol 13-isobutylate (DPB). Bay K 8644 (10 nM), on the other hand, potentiated the contraction in response to practically all agonists used and affected a concomitant increase in [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1810605

  3. Increased responsiveness to 5-hydroxytryptamine after antigenic challenge is inhibited by nifedipine and niflumic acid in rat trachea in vitro.

    PubMed

    Moura, Carlos Tiago Martins; Bezerra, Fernanda Carvalho; de Moraes, Isabelle Maciel; Magalhães, Pedro Jorge Caldas; Capaz, Francisco Ruy

    2005-12-01

    Antigenic challenge often induces hyperreactivity in asthmatic airway, although the precise mechanism(s) underlying this increased responsiveness is not entirely known. Tracheae obtained from ovalbumin (OVA)-sensitized saline- or OVA-challenged rats were placed in 10 mL bath chambers for isometric recording of 5-hydroxytryptamine (5-HT)-induced contractions. 5-Hydroxytryptamine induced a stronger contraction compared with control in antigen-challenged trachea under normal or Ca2+-free conditions. In tracheae pretreated with the L-type Ca2+ channel blocker nifedipine (10(-6) mol/L) or the Ca2+-activated Cl- channel blocker niflumic acid (10(-4) mol/L), this hyperresponsiveness was not developed in either normal or Ca2+-free medium. The increased contractile response to 5-HT in allergic rat isolated trachea may be related to a greater ionic (Ca2+ and Cl-) channel involvement.

  4. Inhibitory 5-hydroxytryptamine receptors involved in pressor effects obtained by stimulation of sympathetic outflow from spinal cord in pithed rats.

    PubMed Central

    Morán, A; Velasco, C; Salvador, T; Martín, M L; San Román, L

    1994-01-01

    1. A study was made of the effects of 5-hydroxytryptamine (5-HT) on pressor response induced in vivo by electrical stimulation of the sympathetic outflow from the spinal cord of pithed rats. All animals had been pretreated with atropine. Intravenous infusion of 5-hydroxytryptamine at doses of 10 and 20 micrograms kg-1 min-1 reduced the pressor effects obtained by electrical stimulation at intervals of 10 min over the 1 h of infusion. 2. This inhibitory action of 5-HT was depressed by cyproheptadine and methiothepin but was not modified by ketanserin or MDL-72222. By contrast, the inhibitory action of 5-HT was lost in pithed rats that had been pretreated with exogenous noradrenaline. 3. The 5-HT1 receptor agonist 5-carboxamidotryptamine (5-CT) caused an inhibition of the pressor response, whereas the 5-HT3 receptor agonist, 1-phenylbiguanide, produced a variable but significant increase in the pressor response. The 5-HT2 receptor agonist, m-CPP, did not modify the pressor sympathetic response. 4. Our results suggest that 5-hydroxytryptamine interferes with sympathetic neurotransmission by inhibiting pressor effects as a result of stimulation of the complete sympathetic outflow, and that this inhibition is mainly through a presynaptic 5-HT1 mechanism. PMID:7889292

  5. 5-hydroxytryptamine stimulation of phospholipase D activity in the rabbit isolated mesenteric artery.

    PubMed

    Hinton, J M; Adams, D; Garland, C J

    1999-04-01

    1. The involvement of phospholipase D (PLD) in the 5-hydroxytryptamine 5-HT1B/5-HT1D-signalling pathway was assessed in the rabbit isolated mesenteric artery. 2. RT-PCR analysis of mesenteric smooth muscle cells revealed a strong signal corresponding to mRNA transcript for the 5-HT1B receptor. The PCR fragment corresponded to the known sequence for the 5-HT1B receptor. No signal corresponding to 5-HT1D mRNA was detected. 3. Neither 5-HT (3 microM) nor KCl (45 mM) individually stimulated any significant increase in the smooth muscle concentration of [33P]-PtdBut to reflect PLD activity. However, in the presence of KCl (45 mM), 5-HT evoked a concentration-dependent increase in [33P]-PtdBut, to a maximum of 84% with 5-HT (3 microM). 4. [33P]-PtdBut accumulation evoked by 5-HT in the presence of KCl was abolished in nominally calcium-free Krebs-Henseleit Buffer (KHB) or with the selective protein kinase C inhibitor, Ro-31 8220 (10 microM, 20 min). 5. 5-HT (3 microM) in the presence of KCl (45 mM) failed to increase either the accumulation of [33P]-phosphatidic acid in the presence of butanol, or total [3H]-inositol phosphates ([3H]-InsP) in the presence of LiCl (10 mM). 6. 5-HT (0.1-1 microM) abolished forskolin (1 microM) stimulated increases in cyclic AMP (15 fold increase), an action which was pertussis toxin-sensitive. 7. Therefore, in the presence of raised extracellular potassium 5-HT can stimulate PLD via 5-HT1B receptors in the rabbit mesenteric artery. This action requires extracellular calcium and the activation of protein kinase C. These characteristics are identical to the profile for 5-HT1B/5-HT1D-receptor evoked contraction in vascular smooth muscle cells, suggesting a role for PLD in this response to 5-HT.

  6. Meta-analysis of 5-hydroxytryptamine type 2A receptor polymorphisms and migraine susceptibility.

    PubMed

    Peng, Jian-Ming; Yu, You-Jiang; Su, Lan-Di; Luo, Xue

    2014-12-01

    Epidemiologic studies have investigated the association of polymorphisms in 5-hydroxytryptamine type 2A receptor (5HT2A) gene and migraine susceptibility, but the results of those studies are inconclusive. To obtain a more systematic estimation of the association, we conducted a comprehensive search to examine all the eligible studies of 5HT2A polymorphisms and migraine risk. The odd ratios (ORs) with 95% confidence intervals (CIs) were used to determine the strength of the association. Publication bias was analyzed by Begg's funnel plots. Seven eligible studies regarding 5HT2A T102C and A-1438G polymorphisms with 721 cases and 713 controls were included in this meta-analysis. Overall, no significant associations were found between 5HT2A T102C (for T vs. C: OR = 1.029, 95% CI = 0.870-1.217, p = 0.739; for TT vs. CC: OR = 1.083, 95% CI = 0.760-1.544, p = 0.657; for TT + TC vs. CC: OR = 1.066, 95% CI = 0.802-1.416, p = 0.662; for TT vs. TC + CC: OR = 1.017, 95% CI = 0.774-1.336, p = 0.904) or A-1438G (for T vs. C: OR = 0.996, 95% CI = 0.726-1.365, p = 0.979; for TT vs. CC: OR = 0.983, 95% CI = 0.511-1.891, p = 0.960; for TT + TC vs. CC: OR = 1.118, 95% CI = 0.654-1.910, p = 0.684; for TT vs. TC + CC: OR = 0.890, 95% CI = 0.528-1.499, p = 0.661) polymorphisms and migraine risk. The further subgroup analysis by ethnicity, assay and disease type also found no significant association using four genetic models. Meanwhile, the publication bias analysis suggests that there is no publication bias in these studies. In conclusion, our current meta-analysis implies that 5HT2A T102C and A-1438G polymorphisms may be not risk factors in the pathogenesis of migraine.

  7. Functional properties of a cloned 5-hydroxytryptamine ionotropic receptor subunit: comparison with native mouse receptors.

    PubMed Central

    Hussy, N; Lukas, W; Jones, K A

    1994-01-01

    1. A comparative study of the whole-cell and single-channel properties of cloned and native mouse 5-hydroxytryptamine ionotropic receptors (5-HT3) was undertaken using mammalian cell lines expressing the cloned 5-HT3 receptor subunit A (5-HT3R-A), superior cervical ganglia (SCG) neurones and N1E-115 cells. 2. No pharmacological difference was found in the sensitivity to the agonists 5-HT and 2-methyl-5-HT, or to the antagonists d-tubocurare and 3-tropanyl-3,5-dichlorobenzoate (MDL-72222). 3. Current-voltage (I-V) relationships of whole-cell currents showed inward rectification in the three preparations. Rectification was stronger both in cells expressing the 5-HT3R-A subunit and in N1E-115 cells when compared with SCG neurones. 4. No clear openings could be resolved in 5-HT-activated currents in patches excised from cells expressing the 5-HT3R-A subunit or N1E-115 cells. Current fluctuation analysis of whole-cell and excised-patch records revealed a slope conductance of 0.4-0.6 pS in both preparations. Current-voltage relationships of these channels showed strong rectification that fully accounted for the whole-cell voltage dependence. 5. In contrast, single channels of about 10 pS were activated by 5-HT in patches excised from SCG neurones. The weak voltage dependence of their conductance did not account completely for the rectification of whole-cell currents. A lower unitary conductance (3.4 pS) was inferred from whole-cell noise analysis. 6. We conclude that the receptor expressed from the cloned cDNA is indistinguishable from the 5-HT3 receptor of N1E-115 cells, suggesting an identical structure for these two receptors. The higher conductance and different voltage dependence of the 5-HT3 receptor in SCG neurones might indicate the participation of an additional subunit in the structure of native ganglionic 5-HT3 receptors. Homo-oligomeric 5-HT3R-A channels may also be present as suggested by the lower conductance estimated by whole-cell noise analysis. PMID

  8. Stimulation and inhibition of adenylyl cyclase by distinct 5-hydroxytryptamine receptors.

    PubMed

    De Vivo, M; Maayani, S

    1990-10-01

    5-Hydroxytryptamine (serotonin, 5-HT) stimulates basal adenylyl cyclase activity in membranes from guinea pig or rat hippocampi, but 5-HT inhibits forskolin-stimulated adenylyl cyclase activity in these same membranes. The opposing effects of 5-HT on adenylyl cyclase activity indicate that distinct 5-HT receptors, positively and negatively coupled to adenylyl cyclase, are present in these membranes. Stimulation of adenylyl cyclase activity is mediated by two distinct 5-HT receptors. The receptor with lower affinity for 5-HT, designated as RL, is apparently homologous with a 5-HT receptor present in rat collicular membranes, but it is not homologous with the stimulatory receptor characterized in neuroblastoma hybrid cell (NCB-20) membranes. The receptor with higher affinity for 5-HT is homologous with the 5-HT1A binding site. The magnitude of stimulation by 5-HT1A receptors is variable with respect to stimulation by RL and is sometimes completely absent. Inhibition of forskolin-stimulated adenylyl cyclase activity, in membranes from either rat or guinea pig hippocampus or rat cortex, is a functional correlate of the 5-HT1A binding site. This inhibitory response was used to determine the pharmacological characteristics of drugs that reportedly have high affinity for 5-HT1A binding sites, such as 1-[2-(4-aminophenyl)ethyl]-4-(3-trifluoromethylphenyl)piperazine (PAPP) and (-)pindolol. PAPP inhibited adenylyl cyclase activity in guinea pig hippocampal membranes with an EC50 value of 27 +/- 3 nM. (-)Pindolol was a partial agonist in inhibiting adenylyl cyclase activity in guinea pig and rat hippocampal membranes. Because of the low intrinsic activity of (-)pindolol, it was tested as an antagonist of the inhibition produced by 5-HT1A receptor agonists in rat hippocampal membranes. The Kb of (-)pindolol was 40 nM as measured by a Schild plot. (-)Propranolol was a simple competitive antagonist at the rat hippocampal receptor with a Kb value of 550 nM. In summary, guinea pig

  9. Oxidation of tryptamine and 5-hydroxytryptamine: a pulse radiolysis and quantum chemical study.

    PubMed

    Gaikwad, P; Priyadarsini, K I; Naumov, S; Rao, B S M

    2009-07-23

    The reactions of oxidizing radicals (*)OH, N(3)(*), Br(2)(*-), and NO(2)(*) with tryptamine (Tpe) and 5-hydroxytryptamine (HTpe) were studied by pulse radiolysis and analyzed by quantum chemical calculations. Barring NO(2)(*) radical, the rate constants for their reaction with Tpe and HTpe were found to be diffusion controlled and the rates in the NO(2)(*) radical reaction with HTpe are lower by 2 orders of magnitude with k approximately 1 x 10(7) dm(3) mol(-1) s(-1). The transient spectra formed on oxidation of Tpe and HTpe exhibited peaks at 330 and 530 nm (indolyl radical) and 420 nm (indoloxyl radical), respectively, and the latter is in reasonable agreement with the calculated value (407 nm). Both radicals decay through direct recombination, but only the indoloxyl radical was observed to react with the parent molecule to give a (HTpe-Ind)(*) radical adduct for [HTpe] > or = 50 x 10(-6) mol dm(-3). The calculated optimized geometries in water revealed the formation of two distinct types of radical adducts, one through the H-O bond and the other by C-C linkage. The H-O bonded radical adduct was found to be exothermic with a reaction enthalpy of -4 kcal mol(-1) and bond length 0.1819 nm and the C-C bonded radical adducts are endothermic and rate determining but are finally driven by exothermic processes involving intermolecular H transfer followed by intramolecular reorganization through H shift resulting in stable C4-C4' and C2-C4' dimers with reaction enthalpies of -39 and -44 kcal mol(-1), respectively, and this process was found to be thermodynamically as efficient as direct recombination of indoloxyl radicals. The formation of the two dimer products was also seen in steady-state radiolysis. The lack of adduct formation in the case of indolyl radical with Tpe is due to the positive free energy change (DeltaG = 10 kcal mol(-1)). The energetics for the (*)OH addition have shown dependence on the site of activation with (HTpe-OH)(*) adducts at C2 and C4 and the

  10. 5-Hydroxytryptamine Changes under Different Pretreatments on Rat Models of Myocardial Infarction and/or Depression

    PubMed Central

    Liu, Mei-Yan; Zhang, Li-Jun; Zhou, Yu-Xin; Wei, Wan-Lin

    2017-01-01

    Background: Psychocardiological researches have suggested a central role of 5-hydroxytryptamine (5-HT) on psychocardiological mechanism. This study aimed to further explore the central role of 5-HT and pretreatment effects of XinLingWan on rats with myocardial infarction (MI) and/or depression. Methods: Ninety Sprague-Dawley rats were randomly divided into three groups: MI group, depression group, and MI + depression group (n = 30 in each group). Each group was then divided into three subgroups (n = 10 in each subgroup): a negative control subgroup (NCS), a Western medicine subgroup (WMS), and a traditional Chinese medicine subgroup (TCMS), which were received pretreatment once a day for 4 weeks by saline, 20 mg/kg sertraline mixed with 2 ml saline, and 40 mg/kg XingLingWan mixed with 2 ml saline, respectively. Different rat models were established after different pretreatments. Rats were then sacrificed for detection of serum 5-HT, platelet 5-HT, 5-HT2A receptors (5-HT2AR), and serotonin transporter (SERT). Data were analyzed by one-way analysis of variance (ANOVA) and least-significant difference (LSD) testing. Results: MI group: compared with NCS, there was a significant increase in WMS and TCMS of serum 5-HT (176.15 ± 11.32 pg/ml vs. 334.50 ± 29.09 pg/ml and 474.04 ± 10.86 pg/ml, respectively, both P = 0.000), platelet 5-HT (129.74 ± 27.17 pg/ml vs. 322.24 ± 11.60 pg/ml and 340.4 5 ± 17.99 pg/ml, respectively, both P = 0.000); depression group: compared with NCS, there was a significant increase in WMS and TCMS of serum 5-HT (194.69 ± 5.09 pg/ml vs. 326.21 ± 39.98 pg/ml and 456.33 ± 23.12 pg/ml, respectively, both P = 0.000), platelet 5-HT (175.15 ± 4.07 pg/ml vs. 204.56 ± 18.59 pg/ml and 252.03 ± 22.26 pg/ml, respectively, P = 0.004 and P = 0.000, respectively); MI + depression group: compared with NCS, there was a significant increase in both WMS and TCMS of serum 5-HT (182.50 ± 10.23 pg/ml vs. 372.55 ± 52.23 pg/ml and 441.76 ± 23.38 pg

  11. Identification of 5-hydroxytryptamine receptors positively coupled to adenylyl cyclase in rat cultured astrocytes

    PubMed Central

    Hirst, Warren D; Price, Gary W; Rattray, Marcus; Wilkin, Graham P

    1997-01-01

    5-Hydroxytryptamine (5-HT) elicited a dose-dependent stimulation of intracellular adenosine 3′ : 5′-cyclic monophosphate (cyclic AMP) accumulation in cultured astrocytes derived from neonatal rat (Sprague Dawley) thalamic/hypothalamic area with a potency (pEC50) of 6.68±0.08 (mean±s.e.mean).In order to characterize the 5-HT receptor responsible for the cyclic AMP accumulation the effects of a variety of compounds were investigated on basal cyclic AMP levels (agonists) and 5-carboxamidotryptamine (5-CT) stimulated cyclic AMP levels (antagonists). The rank order of potency for the agonists investigated was 5-CT (pEC50=7.81±0.09)>5-methoxytryptamine (5-MeOT) (pEC50=6.86±0.36)>5-HT (pEC50=6.68±0.08). The following compounds, at concentrations up to 10 μM, did not affect basal cyclic AMP levels 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), cisapride, sumatriptan, DOI and RU 24969. The rank order of potency of antagonists was meth- iothepin (pKi=7.98±0.25)>mesulergine (pKi=7.58±0.18)>ritanserin (pKi=7.20±0.24)>clozapine (pKi=7.03±0.19)>mianserin (pKi=6.41±0.19). The following compounds, at concentrations up to 10 μM, were inactive: ketanserin, WAY100635, GR127935. This pharmacological profile is consistent with that of 5-HT7 receptor subtype-mediated effects.The cultured astrocytes exhibited regional heterogeneity in the magnitude of cyclic AMP accumulation (Emax). Cells cultured from the thalamic/hypothalamic area had significantly higher Emax values (588±75% and 572±63% of basal levels for 5-CT and 5-HT, respectively) compared to brainstem (274±51% and 318±46%, respectively) and colliculus astrocytes (244±15% and 301±24%, respectively). No significant differences in pEC50 (for either 5-HT or 5-CT) values were observed.Reverse transcriptase-polymerase chain reaction (RT–PCR) with primers specific for the 5-HT7 receptor confirmed expression of messenger RNA for this receptor subtype by the cultured astrocytes derived from all regions

  12. Organization of projections from the raphe nuclei to the vestibular nuclei in rats

    NASA Technical Reports Server (NTRS)

    Halberstadt, A. L.; Balaban, C. D.

    2003-01-01

    Previous anatomic and electrophysiological evidence suggests that serotonin modulates processing in the vestibular nuclei. This study examined the organization of projections from serotonergic raphe nuclei to the vestibular nuclei in rats. The distribution of serotonergic axons in the vestibular nuclei was visualized immunohistochemically in rat brain slices using antisera directed against the serotonin transporter. The density of serotonin transporter-immunopositive fibers is greatest in the superior vestibular nucleus and the medial vestibular nucleus, especially along the border of the fourth ventricle; it declines in more lateral and caudal regions of the vestibular nuclear complex. After unilateral iontophoretic injections of Fluoro-Gold into the vestibular nuclei, retrogradely labeled neurons were found in the dorsal raphe nucleus (including the dorsomedial, ventromedial and lateral subdivisions) and nucleus raphe obscurus, and to a minor extent in nucleus raphe pallidus and nucleus raphe magnus. The combination of retrograde tracing with serotonin immunohistofluorescence in additional experiments revealed that the vestibular nuclei receive both serotonergic and non-serotonergic projections from raphe nuclei. Tracer injections in densely innervated regions (especially the medial and superior vestibular nuclei) were associated with the largest numbers of Fluoro-Gold-labeled cells. Differences were observed in the termination patterns of projections from the individual raphe nuclei. Thus, the dorsal raphe nucleus sends projections that terminate predominantly in the rostral and medial aspects of the vestibular nuclear complex, while nucleus raphe obscurus projects relatively uniformly throughout the vestibular nuclei. Based on the topographical organization of raphe input to the vestibular nuclei, it appears that dense projections from raphe nuclei are colocalized with terminal fields of flocculo-nodular lobe and uvula Purkinje cells. It is hypothesized that

  13. Organization of projections from the raphe nuclei to the vestibular nuclei in rats

    NASA Technical Reports Server (NTRS)

    Halberstadt, A. L.; Balaban, C. D.

    2003-01-01

    Previous anatomic and electrophysiological evidence suggests that serotonin modulates processing in the vestibular nuclei. This study examined the organization of projections from serotonergic raphe nuclei to the vestibular nuclei in rats. The distribution of serotonergic axons in the vestibular nuclei was visualized immunohistochemically in rat brain slices using antisera directed against the serotonin transporter. The density of serotonin transporter-immunopositive fibers is greatest in the superior vestibular nucleus and the medial vestibular nucleus, especially along the border of the fourth ventricle; it declines in more lateral and caudal regions of the vestibular nuclear complex. After unilateral iontophoretic injections of Fluoro-Gold into the vestibular nuclei, retrogradely labeled neurons were found in the dorsal raphe nucleus (including the dorsomedial, ventromedial and lateral subdivisions) and nucleus raphe obscurus, and to a minor extent in nucleus raphe pallidus and nucleus raphe magnus. The combination of retrograde tracing with serotonin immunohistofluorescence in additional experiments revealed that the vestibular nuclei receive both serotonergic and non-serotonergic projections from raphe nuclei. Tracer injections in densely innervated regions (especially the medial and superior vestibular nuclei) were associated with the largest numbers of Fluoro-Gold-labeled cells. Differences were observed in the termination patterns of projections from the individual raphe nuclei. Thus, the dorsal raphe nucleus sends projections that terminate predominantly in the rostral and medial aspects of the vestibular nuclear complex, while nucleus raphe obscurus projects relatively uniformly throughout the vestibular nuclei. Based on the topographical organization of raphe input to the vestibular nuclei, it appears that dense projections from raphe nuclei are colocalized with terminal fields of flocculo-nodular lobe and uvula Purkinje cells. It is hypothesized that

  14. Structural basis of the anti-inflammatory activity of quercetin: inhibition of the 5-hydroxytryptamine type 2 receptor.

    PubMed

    Rotelli, Alejandra Ester; Aguilar, Carlos Fernando; Pelzer, Lilian Eugenia

    2009-09-01

    The anti-inflammatory activity of quercetin was evaluated through serotonin-induced rat-paw edema. The experiments showed that quercetin had an important effect on acute inflammatory processes. Docking of serotonin and quercetin into the homology model of the 5-Hydroxytryptamine Type 2 Receptor allowed to analyze the structural basis of the anti-inflammatory activity. Results showed that serotonin and quercetin bind in the same region of the active site with a similar binding energy but quercetin has a much bigger inhibition constant. Therefore, it seems possible that quercetin may act as a natural inhibitor of the receptor blocking the acute inflammation generated by serotonin.

  15. 5-Hydroxytryptamine2C receptor contribution to m-chlorophenylpiperazine and N-methyl-beta-carboline-3-carboxamide-induced anxiety-like behavior and limbic brain activation.

    PubMed

    Hackler, Elizabeth A; Turner, Greg H; Gresch, Paul J; Sengupta, Saikat; Deutch, Ariel Y; Avison, Malcolm J; Gore, John C; Sanders-Bush, Elaine

    2007-03-01

    Activation of 5-hydroxytryptamine2C (5-HT(2C)) receptors by the 5-HT(2) receptor agonist m-chlorophenylpiperazine (m-CPP) elicits anxiety in humans and anxiety-like behavior in animals. We compared the effects of m-CPP with the anxiogenic GABA(A) receptor inverse agonist N-methyl-beta-carboline-3-carboxamide (FG-7142) on both anxiety-like behavior and regional brain activation using functional magnetic resonance imaging (fMRI) in the rat. We also determined whether the selective 5-HT(2C) receptor antagonist SB 242084 [6-chloro-2,3-dihydro-5-methyl-N-[6-[(2-methyl-3-pyridinyl)oxy]-3-pyridinyl]-1H-indole-1-carboxyamide dihydrochloride] would blunt m-CPP or FG-7142-induced neuronal activation. Both m-CPP (3 mg/kg i.p.) and FG-7142 (10 mg/kg i.p.) elicited anxiety-like behavior when measured in the social interaction test, and pretreatment with SB 242084 (1 mg/kg i.p.) completely blocked the behavioral effects of both anxiogenic drugs. Regional brain activation in vivo in response to anxiogenic drug challenge was determined by blood oxygen level-dependent (BOLD) fMRI using a powerful 9.4T magnet. Region of interest analyses revealed that m-CPP and FG-7142 significantly increased BOLD signals in brain regions that have been linked to anxiety, including the amygdala, dorsal hippocampus, and medial hypothalamus. These BOLD signal increases were blocked by pretreatment with SB 242084. In contrast, injection of m-CPP and FG-7142 resulted in BOLD signal decreases in the medial prefrontal cortex that were not blocked by SB 242084. In conclusion, the brain activation signals produced by anxiogenic doses of both m-CPP and FG-7142 are mediated at least partially by the 5-HT(2C) receptor, indicating that this receptor is a key component in anxiogenic neural circuitry.

  16. Reduced 5-HT(1B) receptor binding in the dorsal brain stem after cognitive behavioural therapy of major depressive disorder.

    PubMed

    Tiger, Mikael; Rück, Christian; Forsberg, Anton; Varrone, Andrea; Lindefors, Nils; Halldin, Christer; Farde, Lars; Lundberg, Johan

    2014-08-30

    Major depression is a significant contributor to the global burden of disease, and its pathophysiology is largely unknown. The serotonin hypothesis is, however, the model with most supporting data, although the details are only worked out to some extent. Recent clinical imaging measurements indeed imply a role in major depressive disorder (MDD) for the inhibitory serotonin autoreceptor 5-hydroxytryptamine1B (5-HT1B). The aim of the current study was to examine 5-HT1B receptor binding in the brain of MDD patients before and after psychotherapy. Ten patients with an ongoing untreated moderate depressive episode were examined with positron emission tomography (PET) and the 5-HT1B receptor selective radioligand [(11)C]AZ10419369, before and after treatment with internet-based cognitive behavioural therapy. All of the patients examined responded to treatment, and 70% were in remission by the time of the second PET measurement. A statistically significant 33% reduction of binding potential (BPND) was found in the dorsal brain stem (DBS) after treatment. No other significant changes in BPND were found. The DBS contains the raphe nuclei, which regulate the serotonin system. This study gives support for the importance of serotonin and the 5-HT1B receptor in the biological response to psychological treatment of MDD.

  17. Age-dependent effects of the 5-hydroxytryptamine-2a-receptor polymorphism (His452Tyr) on human memory.

    PubMed

    Papassotiropoulos, Andreas; Henke, Katharina; Aerni, Amanda; Coluccia, Daniel; Garcia, Esmeralda; Wollmer, Marc A; Huynh, Kim-Dung; Monsch, Andreas U; Stähelin, Hannes B; Hock, Christoph; Nitsch, Roger M; de Quervain, Dominique J-F

    2005-05-31

    A polymorphism (His452Tyr) of the 5-hydroxytryptamine (5-HT)2a receptor is associated with episodic memory in healthy young humans. Because 5-HT2a-receptor density decreases with increasing age, we tested whether the 5-HT2a receptor genotype effect on memory is influenced by age. We investigated the association of the His452Tyr genotype with memory performance in 622 healthy study participants aged from 18 to 90 years. In young to middle-aged participants, age significantly influenced genotype effects on episodic memory: the His452Tyr genotype exerted a significant influence on memory only in young participants. In the group of elderly cognitively healthy participants, the His452Tyr genotype did not affect memory performance. We conclude that age strongly modulates the effect of the 5-HT2a receptor polymorphism at residue 452 on episodic memory.

  18. The action of 5-hydroxytryptamine and related compounds on the activity of retzius cells of the leech Hirudo medicinalis

    PubMed Central

    Smith, P.A.; Walker, R.J.

    1974-01-01

    1 The equipotent molar ratios of a range of tryptamine analogues, as compared with 5-hydroxytryptamine (5-HT), have been determined on the basis of their ability to hyperpolarize the membrane potential of the Retzius cell of the leech, Hirudo medicinalis. 2 The substitution of methyl, fluoro, chloro, methoxy or acetyl groups onto the 5-HT molecule progressively reduced the potency. 3 5-Methoxylation or terminal N-methylation of tryptamine considerably increased the potency of tryptamine but these compounds tended to depolarize cells rather than cause hyperpolarization. In some experiments they were ineffective on preparations pretreated with 5-HT. 4 It is suggested that these compounds may act by a different mechanism from the 5-hydroxylated indoles, perhaps involving a different receptor. PMID:4441793

  19. The effect of DA-9701 on 5-hydroxytryptamine-induced contraction of feline esophageal smooth muscle cells.

    PubMed

    Oh, Kyung Hoon; Nam, Yoonjin; Jeong, Ji Hoon; Kim, In Kyeom; Sohn, Uy Dong

    2014-04-22

    Serotonin, or 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter found in blood platelets, the gastrointestinal (GI) tract, and the central nervous system (CNS) of animals and humans. The signaling pathways of 5-hydroxytryptamine (5-HT)-induced contractions in cat esophageal smooth muscle cell (ESMC)s have been identified, but the downstream components of the 5-HT signaling pathway remain unclear. DA-9701 is the standardized extract of the Pharbitis nil Choisy seed (Pharbitidis Semen, Convolvulaceae) and the root of Corydalis yahusuo W.T. Wang (Corydalis Tuber, Papaveraceae). DA-9701 is known to have strong gastroprokinetic effects and a good safety profile. In this study, we investigated the 5-HT signaling pathway at the G-protein level, and we explored the mechanisms by which DA-9701 induces smooth muscle contraction. Freshly isolated smooth muscle cells were harvested from the feline esophagus, and cells were permeabilized to measure their length. 5-HT produced esophageal smooth muscle contractions in a dose-dependent manner. Furthermore, 5-HT produced a relatively long-acting contraction. 5-HT binds to the 5-HT2, 5-HT3 and 5-HT4 receptors to induce smooth muscle contraction in feline ESMCs. These receptors, which are located in esophageal smooth muscle, are coupled to Gαq, Gαo and Gαs. These G proteins activate PLC, which leads to Ca2+/calmodulin-dependent MLCK activation, resulting in MLC20 phosphorylation and cell contraction. Conversely, DA-9701 inhibits 5-HT-induced contraction by inhibiting MLC20 phosphorylation.

  20. Selective 5-hydroxytryptamine2 antagonists have antidepressant-like effects on differential-reinforcement-of-low-rate 72-second schedule.

    PubMed

    Marek, G J; Li, A A; Seiden, L S

    1989-07-01

    The effects of eleven 5-hydroxytryptamine antagonists with varying selectivity for the 5-hydroxytryptamine2 (5-HT2) relative to the 5-HT1 binding site were assessed in rats responding under a differential-reinforcement-of-low rate 72-sec (DRL 72-s) schedule of reinforcement. Three drugs with a 1000-fold selectivity for the 5-HT2 binding site (ketanserin, ritanserin, pipamperone) increased the reinforcement rate and decreased the response rate similar to antidepressant drugs. The two drugs with roughly the same affinity for both 5-HT1 and 5-HT2 binding sites (methysergide and metergoline) did not increase the reinforcement rate. The maximal increase in the reinforcement rate after 5-HT antagonist administration was positively correlated with the selectivity of the 5-HT antagonists for the 5-HT2 versus the 5-HT1 binding site. The increase in the reinforcement rate after administration of 5-HT antagonists was not correlated with the affinity of the 5-HT antagonists for the alpha-1 adrenergic, alpha-2 adrenergic, histamine-1 or dopamine-2 receptors. The 1000-fold selective 5-HT2 antagonist xylamidine, which does not pass the blood-brain barrier, did not increase the reinforcement rate or decrease the response rate. Thus, selective antagonism of central 5-HT2 relative to 5-HT1 receptors results in antidepressant-like effects on the DRL 72-s schedule. Furthermore, the specificity of the DRL 72-s schedule as a screen for antidepressant drugs was strengthened by the observation that the alpha-1 adrenergic antagonist, prazosin, did not increase the reinforcement rate despite significant decreases in the response rate.

  1. High-level stable expression of recombinant 5-HT1A 5-hydroxytryptamine receptors in Chinese hamster ovary cells.

    PubMed Central

    Newman-Tancredi, A; Wootton, R; Strange, P G

    1992-01-01

    The human 5-hydroxytryptamine 5-HT1A receptor gene was transfected into Chinese hamster ovary cells. A series of recombinant monoclonal cell lines expressing the receptor were isolated and the properties of one cell line that expressed receptors at a high level (2.8 pmol/mg) were studied in detail. In ligand binding assays with the selective 5-HT1A receptor agonist 2-(NN-di[3H]propylamino)-8-hydroxy-1,2,3,4-tetrahydronaphthalene ([3H]8-OH-DPAT) only a single class of saturable high-affinity binding sites was detected, with a pharmacological profile in competition experiments essentially identical to that of the 5-HT1A receptor of bovine hippocampus. [3H]8-OH-DPAT binding to the recombinant cell membranes was inhibited by GTP, showing that the receptors in the transfected cells couple to G-proteins. A series of 5-hydroxytryptamine agonists inhibited forskolin-stimulated adenylate cyclase activity in the cells and, despite the high level of receptor expression, their apparent efficacies were similar to those observed for inhibition of adenylate cyclase in brain. This recombinant cell line provides a complete model system for studying the 5-HT1A receptor and its transmembrane signalling system. The recombinant cells can also be grown in suspension culture for long periods but, whereas 5-HT1A receptor numbers and receptor regulation by guanine nucleotides are maintained in suspension-grown cells, the inhibition of adenylate cyclase by the 5-HT1A receptor is gradually lost. Images Fig. 1. PMID:1386736

  2. Effects of 5-hydroxytryptamine, dopamine, and acetylcholine on accumulation of cyclic AMP and cyclic GMP in the anterior byssus retractor muscle of Mytilus edulis L. (Mollusca).

    PubMed

    Köhler, G; Lindl, T

    1980-02-01

    We investigated in vitro accumulation of adenosine 3',5'-monophosphate (induced by 5-hydroxytryptamine and dopamine) and of guanosine 3',5'-monophosphate (induced by acetylcholine) in the anterior byssus retractor muscle of Mytilus. The response to 5-hydroxytryptamine exceeded that induced by equimolar concentrations of dopamine. 1-methyl lysergic acid, a 5-hydroxytryptamine-blocking agent, diminished the 5-hydroxytryptamine-induced increase of cyclic AMP level. This parallels the effect of this amine on the contracted muscle. Acetylcholine, which causes a tonic contraction of the muscle, increased intracellular levels of cyclic GMP in a dose-dependent (max. 45-fold at 10(-4) M ACh) manner. The time course of the rise in cyclic GMP level was rapid and transient (peak concentration of cyclic GMP at 2 min). Mytolon was the most effective of all cholinergic blockers tested. It was concluded that cyclic nucleotides may play a role in the modulatory process of the transmitters. A direct relation to the relaxation-contraction process could not be established.

  3. A randomized trial of 5-hydroxytryptamine4-receptor agonist, YKP10811, on colonic transit and bowel function in functional constipation.

    PubMed

    Shin, Andrea; Acosta, Andres; Camilleri, Michael; Boldingh, Amy; Burton, Duane; Ryks, Michael; Rhoten, Deborah; Zinsmeister, Alan R

    2015-04-01

    YKP10811, a selective agonist of the serotonin 5-hydroxytryptamine-4 receptor, increases gastrointestinal (GI) motility. We investigated the safety and effects of YKP10811 on GI and colonic transit and bowel movements (BMs) in patients with functional constipation in a randomized, double-blind, placebo-controlled study. Patients with functional constipation, based on the Rome III criteria, were assigned randomly to groups given YKP10811 10 mg (n = 15), 20 mg (n = 16), 30 mg (n = 15), or placebo (n = 11) daily for 8 days. Transit of solids was measured by validated scintigraphy at baseline and on days 7 to 9. Patients kept diaries on days 1 to 9, recording time to first BM, number of BMs/day, and stool consistency (based on the Bristol Stool Form Scale). To evaluate safety, we collected data on adverse events and clinical laboratory test and electrocardiograms results. The primary efficacy end points were determined from an intent-to-treat analysis assessing colonic transit at 24 hours and the half-time (t1/2) of gastric emptying, using analysis of covariance models. Secondary efficacy end points included measures of colonic transit (geometric center at 4 and 24 hours), small-bowel transit (based on colon filling at 6 hours), t1/2 of ascending colon emptying, and bowel functions. We used the Dunnett test to compare the effects of each dose with placebo. A per-protocol analysis (PPA) assessed the t1/2 of gastric emptying and time to first BM using proportional hazards models. Fifty-five participants completed the study. YKP10811 was associated with a significant acceleration in colon filling at 6 hours (P < .05), t1/2 of ascending colon emptying, and colonic transit at 24 and 48 hours, as well as increased stool consistency over 8 days (based on intent-to-treat analysis). In general, the 10-mg and 20-mg doses were the most effective in accelerating colonic transit. No serious adverse events were observed. YKP10811, a selective agonist of the serotonin receptor 5

  4. Immunohistochemical localization of serotonin (5-hydroxytryptamine) in the gonad and digestive gland of Mya arenaria (Mollusca: Bivalvia).

    PubMed

    Garnerot, F; Pellerin, J; Blaise, C; Mathieu, M

    2006-12-01

    Serotonin (5-hydroxytryptamine or 5-HT) C(10)H(12)N(2)O plays a central role in several physiological processes in marine molluscs, especially in reproduction. 5-HT acts as a neurohormone to modulate spawning, parturition and meiosis by reinitiating prophase in arrested oocytes. Preliminary experiments using 10(-5)M 5-HT dissolved in aquarium water showed that 5-HT induced spawning movements in ripe clams and in both sexes of Mya arenaria while only a few males released sperm. The occurrence of serotoninergic fibers was demonstrated by PAP immunohistochemical reaction in the gonad of both sexes during gametogenesis. In an organism infected by the trematode parasite Prosorhynchus squamatus, we showed that serotoninergic innervation completely disappeared around the gonad's follicles. Although the gonad and digestive gland are intertwined, no serotoninergic innervations were found in the digestive gland. These findings suggest, for the first time to our knowledge in the soft shell clam, that serotonin might be involved in the regulation of gametogenesis.

  5. Effects of procaine and extracellular calcium concentration on response of rat stomach fundus muscle to acetylcholine and 5-hydroxytryptamine.

    PubMed Central

    Weinstock, M; Weiss, C

    1979-01-01

    1. When rat stomach fundus muscle was incubated for 30 min in Tyrode solution from which calcium chloride had been omitted, there was an almost complete abolition of the contractile response to 5-hydroxytryptamine (5-HT) while that to acetylcholine (ACh) was still present. 2. The maximum tension obtainable with ACh remained the same in external calcium concentrations ranging from 0.45 to 3.6 mM, but the pD2 value increased. 3. A concentration of at least 0.9 mM calcium was needed to maintain a maximum contraction with 5-HT, and the pD2 for this agent also increased significantly with increase in calcium content of the medium. 4. The effects of procaine on the responses of the muscle to 5-HT and ACh were similar to the respective changes induced by lowering the calcium concentration, and were reduced by the addition of calcium. 5. Concentrations of 2.2 x 10(-7) to 3.6 x 10(-5) M procaine reduced the effects of both 5-HT and KCl and suppressed the maximum responses. 6. The maximum responses to KCl and 5-HT were restored at higher concentrations of procaine (greater than 3.6 x 10(-4) M), while the effect of ACh was reduced. 7. It is suggested that 5-HT, like KCl, is almost entirely dependent on extracellular calcium for inducing muscle contraction, while ACh may utilize calcium from bound stores. PMID:435684

  6. 6-Substituted tricyclic partial ergoline compounds are selective and potent 5-hydroxytryptamine sub 1A receptor agents

    SciTech Connect

    Slaughter, J.L.; Harrington, M.A.; Peroutka, S.J. )

    1990-01-01

    A series of 6 tricyclic partial ergoline derivatives was analyzed using radioligand binding assays. Four agents (LY 178210, LY 254089, LY 197205, and LY 197206) display high affinity for 5-hydroxytryptamine{sub 1A} (5-HT{sub 1A}) receptor binding sites labeled by ({sup 3}H)8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) and display {ge} 150 fold selectivity for the 5-HT{sub 1A} over the 5-HT{sub 1D} receptor binding site. The most potent agent investigated, LY 178210, is essentially inactive at a total of 12 other neurotransmitter receptor binding sites in the brain. Using a forskolin-stimulated adenylate cyclase assay as a model of 5-HT{sub 1A} receptor function, LY 178210 was found to display partial agonist activity which was blocked by 10{sup {minus}5} M ({minus})pindolol. These data indicate that LY 178210 is a potent and selective 5-HT{sub 1A} receptor partial agonist.

  7. Polymorphisms in the 5-hydroxytryptamine receptor 3B gene are associated with heroin dependence in the Chinese Han population.

    PubMed

    Yin, Fangyuan; Ji, Yuanyuan; Zhang, Jing; Guo, Hao; Huang, Xin; Lai, Jianghua; Wei, Shuguang

    2016-12-02

    Previous studies suggested that the 5-hydroxytryptamine receptor 3B (HTR3B) is involved in heroin dependence by modulating dopamine (DA) release in the reward pathway and that the genetic polymorphisms in HTR3B play plausible role in modulating the risk of developing heroin addiction. To identify markers that contribute to the genetic susceptibility to heroin dependence, we examined the potential associations between heroin dependence and 7 single nucleotide polymorphisms (SNPs) of the HTR3B gene using multiplex SNaPshot technology in a Chinese Han population. Participants included 418 heroin-dependent subjects and 422 healthy controls. The results suggested that the genotype distribution of HTR3B rs1176746 and rs1185027 were significantly different between heroin dependent subjects and healthy controls (both p=0.004). The frequency of the GG of rs1176746 and AA of rs1185027 genotype in heroin-dependent subjects were significantly higher than that of healthy controls, while the GA of rs1176746 and AT of rs1185027 genotype distributions were much lower. Another SNP, rs10789970, showed a nominally significant p-value in the genotype distribution between heroin dependent subjects and controls (p=0.022). These findings indicate the important role of HTR3B polymorphisms in heroin dependence among the Chinese Han population and provide valuable information for further genetic and neurobiological investigations of heroin dependence. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  8. Mediation of 5-hydroxytryptamine-induced tachycardia in the pig by the putative 5-HT4 receptor.

    PubMed Central

    Villalón, C. M.; den Boer, M. O.; Heiligers, J. P.; Saxena, P. R.

    1990-01-01

    Intravenous bolus injections of 5-hydroxytryptamine (5-HT; 3, 10 and 30 micrograms kg-1), 5-methoxytryptamine (5-MeO-T; 3, 10 and 30 micrograms kg-1), renzapride (BRL 24924; 3, 10, 30 and 100 micrograms kg-1) and isoprenaline (0.03, 0.1 and 0.3 micrograms kg-1) to anaesthetized pigs increased heart rate by, respectively, 22 +/- 3, 44 +/- 3 and 65 +/- 4 beats min-1 (5-HT; n = 17); 12 +/- 1, 26 +/- 2 and 44 +/- 4 beats min-1 (5-MeO-T; n = 15), 5 +/- 2, 11 +/- 2, 18 +/- 4 and 37 +/- 5 beats min-1 (renzapride; n = 8) and 17 +/- 2, 46 +/- 3 and 75 +/- 3 beats min-1 (isoprenaline; n = 13). The responses to 5-HT, 5-MeO-T and renzapride were antagonized by ICS 205-930 (1 and 3 mg kg-1, i.v.), which did not modify the increases in heart rate by isoprenaline. Renzapride showed tachyphylaxis and attenuated the responses to 5-HT. These findings indicate that 5-HT elicits tachycardia in the pig by acting on a novel receptor, either similar or identical to the 5-HT4 receptor identified in mouse brain colliculi. PMID:2207493

  9. Serotonin (5-hydroxytryptamine, 5-HT) immunoreactive endocrine and neural elements in the chromaffin enteropancreatic system of amphibians and reptiles.

    PubMed

    Trandaburu, Tiberiu; Trandaburu, Ioana

    2007-01-01

    The diffuse chromaffin enteropancreatic system of nine species of amphibians (newts, frogs) and reptiles (turtles, lizards, snakes) was investigated immunohistochemically for the presence and topographic distribution of serotonin (5-hydroxytryptamine, 5-HT). The study revealed various numbers of serotonin-producing cells in the pancreas and intestinal epithelium and also immunolabelled nerve profiles in the villi of all species studied. In addition, two different morphological populations of serotonin cells ("open" and "closed") were localized in the functional segments of the intestines in the representative species of all the taxa investigated. Semi-quantitative evaluation of the immunolabelled pancreatic and enteric cells revealed significantly different mean numbers of labelled cells in different amphibian and reptilian taxa, and also between the various successive gut segments of each taxon. The ratio between "open" and "closed" varieties of serotonin cells recorded along the intestines followed a decreasing trend, progressive in lizards and snakes and more abrupt in newts, frogs and turtles. The above findings may help resolve several key stages of the phylogenetic evolution of poikilothermic vertebrates.

  10. Kinetic definition of agonist efficacy at a 5-hydroxytryptamine (5-HT2) receptor in the isolated rabbit aorta.

    PubMed

    Cory, R N; Osman, R; Maayani, S

    1986-01-01

    The contractile response of the isolated rabbit aorta elicited by 5-hydroxytryptamine (5-HT) and five partial agonists acting on the 5-HT2 receptor were separated into a phasic and a tonic response by altering the [Ca++] in the buffer. A kinetic analysis of the two responses yields parameters that provide a mechanistic insight into the different nature of these responses. The kinetic parameters of the phasic contraction indicate that the onset of this response depends on the access of the drug to the receptor and that its decay is independent of the nature and the concentration of the agonist. The observed rate constant of the onset of the tonic response, kobs, is saturable with increasing drug concentration, suggesting that the rate determining step is the activation of an effector by the preformed drug-receptor complex. These kinetic characteristics of the 5-HT2-mediated response are similar to those observed previously by us for the alpha-1 adrenergic receptor-mediated response in the rabbit aorta, suggesting that these receptors activate similar mechanisms related to the mobilization of Ca++. Furthermore, it is shown that the maximal values of kobs for the 5-HT2 agonists follow the rank order of maximal amplitudes of the phasic responses and the maximal steady-state levels of the tonic response. It is suggested that the maximal value of kobs may serve as a kinetic measure of drug efficacy.

  11. 5-Carboxamidotryptamine is a selective agonist at 5-hydroxytryptamine receptors mediating vasodilatation and tachycardia in anaesthetized cats.

    PubMed Central

    Connor, H. E.; Feniuk, W.; Humphrey, P. P.; Perren, M. J.

    1986-01-01

    We have attempted to characterize the 5-hydroxytryptamine (5-HT) receptors mediating bronchoconstriction, vasodilatation, vasodepression and tachycardia in anaesthetized cats following bilateral vagosympathectomy and beta-adrenoceptor blockade with propranolol. 5-HT (1-100 micrograms/kg-1 i.v.) caused dose-related bronchoconstriction and tachycardia but variable and complex effects on diastolic blood pressure and carotid arterial vascular resistance. In contrast, 5-carboxamidotryptamine (5-CT; 0.01-1 micrograms kg-1 i.v.) caused consistent, dose-related decreases in diastolic blood pressure and carotid arterial vascular resistance and increases in heart rate. 5-CT did not cause bronchoconstriction. The 5-HT-induced bronchoconstriction was dose-dependently antagonized by methiothepin, methysergide and ketanserin (10-100 micrograms kg-1 i.v.). The highest doses used of these antagonists did not antagonize bronchoconstriction induced by prostaglandin F2 alpha. The high potency of all three antagonists indicate a 5-HT2-receptor mediated effect. The 5-HT- and 5-CT-induced tachycardia as well as the 5-CT-induced vasodepressor and carotid arterial vasodilator responses were dose-dependently antagonized by low doses of methiothepin (10-100 micrograms kg-1 i.v.) and by high doses of methysergide (100-1000 micrograms kg-1 i.v.) but were little affected by ketanserin in doses up to 1000 micrograms kg-1 i.v. These selective effects of 5-CT appear to be mediated by '5-HT1-like' receptors. PMID:2937503

  12. Comparative effects of niflumic acid and nifedipine on 5-hydroxytryptamine- and acetylcholine-induced contraction of the rat trachea.

    PubMed

    Teixeira, M C; Coelho, R R; Leal-Cardoso, J H; Criddle, D N

    2000-04-07

    The effects of niflumic acid, an inhibitor of Ca(2+)-activated Cl(-) (Cl((Ca))) channels, were compared with those of the voltage-dependent Ca(2+) channel (VDCC) blocker nifedipine on 5-hydroxytryptamine (5-HT)- and acetylcholine-induced contractions of the rat isolated trachea. Niflumic acid (3-100 microM) induced a concentration-dependent inhibition of 5-HT (10 microM)-induced contractions, with a reduction to 37.0+/-9.5% of the control at the highest concentration. One micromolar nifedipine, which completely blocked 60 mM KCl-induced contractions, reduced the response to 5-HT similarly to 39.2+/-11.5% of the control. The inhibition of the 5-HT response was not significantly different from that produced by the combined presence of nifedipine (1 microM) and niflumic acid (100 microM), suggesting that their effects were not additive. In contrast, neither niflumic acid (3-100 microM) nor nifedipine (1 microM) inhibited acetylcholine-induced contractions. The contraction to 5-HT (10 microM) in Cl(-)-free solution was decreased by more than approximately 85% of the control, whilst that of acetylcholine was reduced only by approximately 36%. Our data show that niflumic acid exerts selective inhibitory effects on 5-HT-induced contraction, and suggest that activation of Cl((Ca)) channels may be a mechanism whereby 5-HT (but not acetylcholine) induces Ca(2+) entry via VDCCs to elicit contraction.

  13. Superagonist, Full Agonist, Partial Agonist, and Antagonist Actions of Arylguanidines at 5-Hydroxytryptamine-3 (5-HT3) Subunit A Receptors.

    PubMed

    Alix, Katie; Khatri, Shailesh; Mosier, Philip D; Casterlow, Samantha; Yan, Dong; Nyce, Heather L; White, Michael M; Schulte, Marvin K; Dukat, Małgorzata

    2016-11-16

    Introduction of minor variations to the substitution pattern of arylguanidine 5-hydroxytryptamine-3 (5-HT3) receptor ligands resulted in a broad spectrum of functionally-active ligands from antagonist to superagonist. For example, (i) introduction of an additional Cl-substituent(s) to our lead full agonist N-(3-chlorophenyl)guanidine (mCPG, 2; efficacy % = 106) yielded superagonists 7-9 (efficacy % = 186, 139, and 129, respectively), (ii) a positional isomer of 2, p-Cl analog 11, displayed partial agonist actions (efficacy % = 12), and (iii) replacing the halogen atom at the meta or para position with an electron donating OCH3 group or a stronger electron withdrawing (i.e., CF3) group resulted in antagonists 13-16. We posit based on combined mutagenesis, crystallographic, and computational analyses that for the 5-HT3 receptor, the arylguanidines that are better able to simultaneously engage the primary and complementary subunits, thus keeping them in close proximity, have greater agonist character while those that are deficient in this ability are antagonists.

  14. 5-Hydroxytryptamine (5-HT) Cellular Sequestration during Chronic Exposure Delays 5-HT3 Receptor Resensitization due to Its Subsequent Release*

    PubMed Central

    Hothersall, J. Daniel; Alexander, Amy; Samson, Andrew J.; Moffat, Christopher; Bollan, Karen A.; Connolly, Christopher N.

    2014-01-01

    The serotonergic synapse is dynamically regulated by serotonin (5-hydroxytryptamine (5-HT)) with elevated levels leading to the down-regulation of the serotonin transporter and a variety of 5-HT receptors, including the 5-HT type-3 (5-HT3) receptors. We report that recombinantly expressed 5-HT3 receptor binding sites are reduced by chronic exposure to 5-HT (IC50 of 154.0 ± 45.7 μm, t½ = 28.6 min). This is confirmed for 5-HT3 receptor-induced contractions in the guinea pig ileum, which are down-regulated after chronic, but not acute, exposure to 5-HT. The loss of receptor function does not involve endocytosis, and surface receptor levels are unaltered. The rate and extent of down-regulation is potentiated by serotonin transporter function (IC50 of 2.3 ± 1.0 μm, t½ = 3.4 min). Interestingly, the level of 5-HT uptake correlates with the extent of down-regulation. Using TX-114 extraction, we find that accumulated 5-HT remains soluble and not membrane-bound. This cytoplasmically sequestered 5-HT is readily releasable from both COS-7 cells and the guinea pig ileum. Moreover, the 5-HT level released is sufficient to prevent recovery from receptor desensitization in the guinea pig ileum. Together, these findings suggest the existence of a novel mechanism of down-regulation where the chronic release of sequestered 5-HT prolongs receptor desensitization. PMID:25281748

  15. Modulation of the hypoxic sensory response of the carotid body by 5-hydroxytryptamine: role of the 5-HT2 receptor.

    PubMed

    Jacono, F J; Peng, Y-J; Kumar, G K; Prabhakar, N R

    2005-02-15

    Previous studies have shown that glomus cells of the carotid body express 5-hydroxytryptamine (5-HT). The aim of this study was to elucidate the role of 5-HT on the hypoxic sensory response (HSR) of the carotid body. Sensory activity was recorded from multi-fiber (n=16) and single-fiber (n=8) preparations of ex vivo carotid bodies harvested from anesthetized, adult rats. 5-HT (3 microM) had no significant effect on the magnitude or on the onset of the HSR. However, 5-HT consistently prolonged the time necessary for the sensory activity to return to baseline following the termination of the hypoxic challenge. Ketanserin (40 microM), a 5-HT2 receptor antagonist completely prevented 5-HT-induced prolongation of the HSR, whereas had no effect on the control HSR (onset, magnitude, and time for decay without 5-HT). Carotid bodies expressed 5-HT, but hypoxia did not facilitate 5-HT release. These observations suggest that 5-HT is not critical for the HSR of the rat carotid body, but it modulates the dynamics of the HSR via its action on 5-HT2 receptors.

  16. Identification of 5-Hydroxytryptamine-Producing Cells by Detection of Fluorescence in Paraffin-Embedded Tissue Sections

    PubMed Central

    Kaneko, Y.; Onda, N.; Watanabe, Y.; Shibutani, M.

    2016-01-01

    5-Hydroxytryptamine (5-HT) produced by enterochromaffin (EC) cells is an important enteric mucosal signaling ligand and has been implicated in several gastrointestinal diseases, including inflammatory bowel disease and functional disorders such as irritable bowel syndrome. The present study reports a new, simple and rapid visualization method of 5-HT-producing EC cells utilizing detection of fluorescence in paraffin-embedded tissue sections after formalin fixation. In human samples, there was a high incidence of fluorescence+ cells in the 5-HT+ cells in the pyloric, small intestinal and colonic glands, while co-localization was lacking between fluorescence+ and gastrin+ cells in the pyloric and small intestinal glands. Fluorescence+ EC cells were detected in the colon of mice and rats. Fluorescence+ cells were also observed in 5-HT+ β cells in the pancreatic islets of Langerhans in pregnant mice, while non-pregnant mouse pancreatic islet cells showed no 5-HT immunoreactivity or fluorescence. These results suggest that fluorescence+ cells are identical to 5-HT+ cells, and the source of fluorescence may be 5-HT itself or molecules related to its synthesis or degradation. This fluorescence signal detection method may be applicable for monitoring of inflammatory status of inflammatory bowel diseases in both the experimental and clinical settings. PMID:27734992

  17. Identification and characterization of a truncated variant of the 5-hydroxytryptamine(2A) receptor produced by alternative splicing.

    PubMed

    Guest, P C; Salim, K; Skynner, H A; George, S E; Bresnick, J N; McAllister, G

    2000-09-08

    We have identified an alternatively spliced 5-hydroxytryptamine 2A receptor (5-HT(2A)-R) transcript by PCR of human brain cDNA using degenerate oligonucleotide primers to transmembrane (TM) domains 3 and 7 of the 5-HT(2)-R subfamily. The variant contains a 118-bp insertion at the exon II/III boundary of the 5-HT(2A)-R, which produces a frame shift in the coding sequence and a premature stop codon. PCR analysis showed that the truncated receptor (5-HT(2A-tr)) and native 5-HT(2A)-R were co-expressed in most brain tissues, with the highest levels being found in hippocampus, corpus collosum, amygdala and caudate nucleus. Western blot analysis of HEK-293 cells transfected transiently with a 5-HT(2A-tr) construct showed that a 30-kDa protein was expressed on cell membranes. Co-transfection studies showed no effect of the 5-HT(2A-tr) variant on 3H-ketanserin binding to the native 5-HT(2A)-R or on functional coupling of the 5-HT(2A)-R to 5-HT-stimulated Ca(2+) mobilization. The functional significance of the 5-HT(2A-tr) variant and other truncated receptors remains to be established.

  18. Quercetin inhibits the 5-hydroxytryptamine type 3 receptor-mediated ion current by interacting with pre-transmembrane domain I.

    PubMed

    Lee, Byung-Hwan; Jeong, Sang-Min; Jung, Sang-Min; Lee, Jun-Ho; Kim, Jong-Hoon; Yoon, In-Soo; Lee, Joon-Hee; Choi, Sun-Hye; Lee, Sang-Mok; Chang, Choon-Gon; Kim, Hyung-Chun; Han, YeSun; Paik, Hyun-Dong; Kim, Yangmee; Nah, Seung-Yeol

    2005-08-31

    The flavonoid, quercetin, is a low molecular weight substance found in apple, tomato and other fruit. Besides its antioxidative effect, quercetin, like other flavonoids, has a wide range of neuropharmacological actions including analgesia, and motility, sleep, anticonvulsant, sedative and anxiolytic effects. In the present study, we investigated its effect on mouse 5-hydroxytryptamine type 3 (5-HT3A) receptor channel activity, which is involved in pain transmission, analgesia, vomiting, and mood disorders. The 5-HT3A receptor was expressed in Xenopus oocytes, and the current was measured with the two-electrode voltage clamp technique. In oocytes injected with 5-HT3A receptor cRNA, quercetin inhibited the 5-HT-induced inward peak current (I(5-HT)) with an IC50 of 64.7 +/- 2.2 microM. Inhibition was competitive and voltage-independent. Point mutations of pre-transmembrane domain 1 (pre-TM1) such as R222T and R222A, but not R222D, R222E and R222K, abolished inhibition, indicating that quercetin interacts with the pre-TM1 of the 5-HT3A receptor.

  19. Release of endogenous 5-hydroxytryptamine from the myenteric plexus of the guinea-pig isolated small intestine.

    PubMed Central

    Holzer, P.; Skofitsch, G.

    1984-01-01

    The presence of 5-hydroxytryptamine (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in, and the release of these substances from, the myenteric plexus-longitudinal muscle (MPLM) layer of the guinea-pig isolated small intestine were investigated. 5-HT and 5-HIAA were measured by high performance liquid chromatography and electrochemical detection. Freshly prepared MPLM contained measurable amounts of 5-HT and 5-HIAA. For the release experiments, the MPLM was incubated in a medium containing the 5-HT uptake inhibitor fluoxetine and the monoamine oxidase inhibitor nialamide; this led to a decrease in the 5-HIAA content of the MPLM whereas the 5-HT content remained unchanged. There was a spontaneous release of 5-HT and 5-HIAA from the MPLM. The release of 5-HT was so small that it was just detectable; it seemed equivalent to about 0.8% of the tissue stores released per min. Depolarization of the tissue by increasing the [K+] or by exposing it to veratridine enhanced the release of 5-HT in a Ca2+-dependent manner whereas the release of 5-HIAA was not increased. Tetrodotoxin inhibited the veratridine-evoked release of 5-HT but did not affect the K+-evoked release of 5-HT. The presence of 5-HT in myenteric neurones and the characteristics of the release of 5-HT from these neurones strongly support the hypothesis that 5-HT is an enteric neurotransmitter. PMID:6200171

  20. Action of angiotensin II, 5-hydroxytryptamine and adenosine triphosphate on ionic currents in single ear artery cells of the rabbit.

    PubMed

    Hughes, A D; Bolton, T B

    1995-10-01

    1. Angiotensin II, 5-hydroxytryptamine (5-HT) and adenosine triphosphate (ATP) evoked a transient inward current in isolated single car artery cells of rabbit held at -60 mV by whole cell voltage clamp in physiological saline using a KCL-containing pipette solution. Under these conditions agonist did not activate a calcium-dependent potassium current. 2. Responses to each agonist were transient and desensitized rapidly. Inward current at -60 mV holding potential was not abolished by blockade of voltage-dependent calcium channels or by buffering intracellular calcium with BAPTA, a calcium chelator, or following depletion of intracellular calcium stores with ryanodine. 3. The shape of the current-voltage relationships and the reversal potentials of the current induced by angiotensin II, 5-HT and ATP were similar under a variety of ionic conditions. Agonist-induced current was unaffected by replacing intracellular chloride with citrate ions or by replacing intracellular sodium with caesium or extracellular sodium with barium or calcium. Replacement of extracellular sodium with Tris shifted the reversal potential in all cases by around 30 mV negatively. 4. These data suggest that angiotensin II, 5-HT and ATP activate similar cationic conductances which are relatively non-selective allowing mono- and divalent cations to cross the smooth muscle cell membrane. These channels may allow the influx of calcium under physiological conditions.

  1. Effect of nitroglycerine in popliteal preparations from patients with peripheral occlusive arteriopathy precontracted with KCl or 5-hydroxytryptamine.

    PubMed

    Ortega, Ana; Avellanal, Martin; España, Gabriel; Flores, Angel; Aleixandre, Amaya

    2003-08-01

    1. At the present time, there are no studies in isolated arteries from patients suffering from peripheral occlusive arteriopathy (POA). In the present study, we attempt to characterize the effect of nitroglycerine (GTN) in isolated popliteal preparations obtained after leg amputation in 60-90-year-old men and women suffering from POA. 2. After surgical operation, arterial samples were stored in a refrigerator at 4 degrees C and, after 12-36 h, they were cut into rings and mounted in organ baths containing Krebs'-Henseleit solution at 37 degrees C and gassed constantly with 95% CO2 and 5% O2. Because noradrenaline elicited very poor contractile responses in these preparations, in the present study we evaluated the concentration-dependent contractions induced by KCl (15-90 mmol/L) and 5-hydroxytryptamine (5-HT; 10-7 to 10-4 mol/L) in arteriopathic popliteal rings and, when the corresponding maximum contractile effect had been obtained, we also evaluated the concentration-dependent relaxing effect produced by GTN (10-10 to 10-5 mol/L) in all precontracted preparations. As a reference, similar experiments were performed in popliteal preparations obtained following surgery on non-arteriopathic vascular tissue where it was necessary to resect a certain percentage of healthy vessel. 3. The responses to KCl and 5-HT were greater in healthy vessel than in arteriopathic rings. The relaxing effect of GTN was greater in preparations precontracted with 5-HT than in those preparations precontracted with KCl. In addition, preparations precontracted with KCl relaxed even less when they were obtained from patients with POA. 4. The present data indicate that GTN is a vasodilator with little effect on depolarized arteries. The results also indicate that the effect of this drug is even less in depolarized arteries from patients with POA.

  2. 5-hydroxytryptamine (5-HT) reduces total peripheral resistance during chronic infusion: direct arterial mesenteric relaxation is not involved

    PubMed Central

    2012-01-01

    Serotonin (5-hydroxytryptamine; 5-HT) delivered over 1 week results in a sustained fall in blood pressure in the sham and deoxycorticosterone acetate (DOCA)-salt rat. We hypothesized 5-HT lowers blood pressure through direct receptor-mediated vascular relaxation. In vivo, 5-HT reduced mean arterial pressure (MAP), increased heart rate, stroke volume, cardiac index, and reduced total peripheral resistance during a 1 week infusion of 5-HT (25 µg/kg/min) in the normotensive Sprague Dawley rat. The mesenteric vasculature was chosen as an ideal candidate for the site of 5-HT receptor mediated vascular relaxation given the high percentage of cardiac output the site receives. Real-time RT-PCR demonstrated that mRNA transcripts for the 5-HT2B, 5-HT1B, and 5-HT7 receptors are present in sham and DOCA-salt superior mesenteric arteries. Immunohistochemistry and Western blot validated the presence of the 5-HT2B, 5- HT1B and 5-HT7 receptor protein in sham and DOCA-salt superior mesenteric artery. Isometric contractile force was measured in endothelium-intact superior mesenteric artery and mesenteric resistance arteries in which the contractile 5- HT2A receptor was antagonized. Maximum concentrations of BW-723C86 (5- HT2B agonist), CP 93129 (5-HT1B agonist) or LP-44 (5-HT7 agonist) did not relax the superior mesenteric artery from DOCA-salt rats vs. vehicle. Additionally, 5-HT (10–9 M to 10–5 M) did not cause relaxation in either contracted mesenteric resistance arteries or superior mesenteric arteries from normotensive Sprague- Dawley rats. Thus, although 5-HT receptors known to mediate vascular relaxation are present in the superior mesenteric artery, they are not functional, and are therefore not likely involved in a 5-HT-induced fall in total peripheral resistance and MAP. PMID:22559843

  3. 5-hydroxytryptamine (5-HT) reduces total peripheral resistance during chronic infusion: direct arterial mesenteric relaxation is not involved.

    PubMed

    Davis, Robert Patrick; Pattison, Jill; Thompson, Janice M; Tiniakov, Ruslan; Scrogin, Karie E; Watts, Stephanie W

    2012-05-06

    Serotonin (5-hydroxytryptamine; 5-HT) delivered over 1 week results in a sustained fall in blood pressure in the sham and deoxycorticosterone acetate (DOCA)-salt rat. We hypothesized 5-HT lowers blood pressure through direct receptor-mediated vascular relaxation. In vivo, 5-HT reduced mean arterial pressure (MAP), increased heart rate, stroke volume, cardiac index, and reduced total peripheral resistance during a 1 week infusion of 5-HT (25 µg/kg/min) in the normotensive Sprague Dawley rat. The mesenteric vasculature was chosen as an ideal candidate for the site of 5-HT receptor mediated vascular relaxation given the high percentage of cardiac output the site receives. Real-time RT-PCR demonstrated that mRNA transcripts for the 5-HT2B, 5-HT1B, and 5-HT7 receptors are present in sham and DOCA-salt superior mesenteric arteries. Immunohistochemistry and Western blot validated the presence of the 5-HT2B, 5- HT1B and 5-HT7 receptor protein in sham and DOCA-salt superior mesenteric artery. Isometric contractile force was measured in endothelium-intact superior mesenteric artery and mesenteric resistance arteries in which the contractile 5- HT2A receptor was antagonized. Maximum concentrations of BW-723C86 (5- HT2B agonist), CP 93129 (5-HT1B agonist) or LP-44 (5-HT7 agonist) did not relax the superior mesenteric artery from DOCA-salt rats vs. vehicle. Additionally, 5-HT (10-9 M to 10-5 M) did not cause relaxation in either contracted mesenteric resistance arteries or superior mesenteric arteries from normotensive Sprague- Dawley rats. Thus, although 5-HT receptors known to mediate vascular relaxation are present in the superior mesenteric artery, they are not functional, and are therefore not likely involved in a 5-HT-induced fall in total peripheral resistance and MAP.

  4. The role of brain 5-hydroxytryptamine in the hyperactivity produced in rats by lithium and monoamine oxidase inhibition

    PubMed Central

    Grahame-Smith, D.G.; Green, A.R.

    1974-01-01

    1 Administration to rats of LiCl (3 mEq/kg) subcutaneously twice daily for 3 days followed by monoamine oxidase inhibition with either tranylcypromine (TCP; 20 mg/kg) or pargyline (75 mg/kg) on the fourth day produces a syndrome of hyperactivity indistinguishable from that produced by monoamine oxidase inhibition and L-tryptophan administration. 2 At least 3 injections of LiCl (3 mEq/kg) are necessary before hyperactivity is seen but one dose of LiCl (10 mEq/kg) 5 h before TCP also caused hyperactivity. The hyperactivity is blocked by prior administration of p-chlorophenylalanine, a tryptophan hydroxylase inhibitor. 3 LiCl pretreatment does not alter the concentration of L-tryptophan in the brain. However after monoamine oxidase inhibition the 5-hydroxytryptamine (5-HT) accumulation was significantly greater in animals given lithium indicating an increase in 5-HT synthesis of 70%. This was confirmed by measuring 5-hydroxyindoleacetic acid accumulation after probenecid (200 mg/kg). 4 The hyperactivity produced by the 5-HT analogue, 5-methoxy N,N-dimethyltryptamine was not potentiaed by lithium pretreatment but one injection of LiCl (3 mEq/kg) which did not alter the rate of 5-HT synthesis, did potentiate the hyperactivity following TCP (20 mg/kg) and L-tryptophan (50 mg/kg). 5 These results suggest that lithium administration may cause an initial alteration of the 5-HT available for release at the nerve ending, which is followed after subsequent treatment by an increase in the rate of 5-HT synthesis. The possible clinical significance of these findings is discussed. PMID:4281339

  5. Prediction of clinical response based on pharmacokinetic/pharmacodynamic models of 5-hydroxytryptamine reuptake inhibitors in mice.

    PubMed

    Kreilgaard, M; Smith, D G; Brennum, L T; Sánchez, C

    2008-09-01

    Bridging the gap between preclinical research and clinical trials is vital for drug development. Predicting clinically relevant steady-state drug concentrations (Css) in serum from preclinical animal models may facilitate this transition. Here we used a pharmacokinetic/pharmacodynamic (PK/PD) modelling approach to evaluate the predictive validity of 5-hydroxytryptamine (5-HT; serotonin) transporter (SERT) occupancy and 5-hydroxytryptophan (5-HTP)-potentiated behavioral syndrome induced by 5-HT reuptake inhibitor (SRI) antidepressants in mice. Serum and whole brain drug concentrations, cortical SERT occupancy and 5-HTP-potentiated behavioral syndrome were measured over 6 h after a single subcutaneous injection of escitalopram, paroxetine or sertraline. [(3)H]2-(2-dimethylaminomethylphenylsulphanyl)-5-methyl-phenylamine ([(3)H]MADAM) was used to assess SERT occupancy. For PK/PD modelling, an effect-compartment model was applied to collapse the hysteresis and predict the steady-state relationship between drug exposure and PD response. The predicted Css for escitalopram, paroxetine and sertraline at 80% SERT occupancy in mice are 18 ng mL(-1), 18 ng mL(-1) and 24 ng mL(-1), respectively, with corresponding responses in the 5-HTP behavioral model being between 20-40% of the maximum. Therapeutically effective SERT occupancy for SRIs in depressed patients is approximately 80%, and the corresponding plasma Css are 6-21 ng mL(-1), 21-95 ng mL(-1) and 20-48 ng mL(-1) for escitalopram, paroxetine and sertraline, respectively. Thus, PK/PD modelling using SERT occupancy and 5-HTP-potentiated behavioral syndrome as response markers in mice may be a useful tool to predict clinically relevant plasma Css values.

  6. Effects of chlorphentermine and phentermine on the pulmonary disposition of 5-hydroxytryptamine in the rat in vivo

    SciTech Connect

    Morita, T.; Mehendale, H.M.

    1983-06-01

    This study was designed to examine whether chlorphentermine (CP) affects pulmonary disposition of 5-hydroxytryptamine (5-HT) in rat in vivo. Further, the effects of CP were compared with those of phentermine (P), the nonchlorinated congener. The right jugular vein and left carotid artery of male Sprague-Dawley rats were cannulated and fresh saline solution containing 150 micrograms indocyanine green and a mixture of labeled and unlabeled 5-HT was injected into the jugular vein, and arterial blood samples were collected for 20 s. In order to compare the effect of CP and P on pulmonary disposition of 5-HT, 2.6 nmol (/sup 14/C)-5-HT was employed for in vivo single-pass experiments. Each animal was used for 2 in vivo single-pass experiments. After the first experiment, which served as a control, animals received an indicated dose of CP or P, to commence the second ''drug-treated'' in vivo experiment. Pulmonary clearance of 5-HT was inhibited by prior administration of CP (1 mg/kg) by 42%, whereas at the highest dose (20 mg/kg) P inhibited 5-HT clearance by only 25%. Pulmonary accumulation of CP was greater than P at higher doses, and the inhibition of 5-HT clearance correlated with the pulmonary accumulation of these drugs. In addition to the in vivo demonstration of the CP inhibition of pulmonary clearance of 5-HT in the rat, these studies also demonstrate a higher affinity of the lung tissue for CP than for P and a greater propensity for the impairment of pulmonary 5-HT clearance.

  7. Changes in 5-hydroxytryptamine and cortisol plasma levels in menopausal women after inhalation of clary sage oil.

    PubMed

    Lee, Kyung-Bok; Cho, Eun; Kang, Young-Sook

    2014-11-01

    The purpose of this study was to examine the antidepressant-like effects of clary sage oil on human beings by comparing the neurotransmitter level change in plasma. The voluntary participants were 22 menopausal women in 50's. Subjects were classified into normal and depression tendency groups using each of Korean version of Beck Depression Inventory-I (KBDI-I), KBDI-II, and Korean version of Self-rating Depression Scale. Then, the changes in neurotransmitter concentrations were compared between two groups. After inhalation of clary sage oil, cortisol levels were significantly decreased while 5-hydroxytryptamine (5-HT) concentration was significantly increased. Thyroid stimulating hormone was also reduced in all groups but not statistically significantly. The different change rate of 5-HT concentration between normal and depression tendency groups was variable according to the depression measurement inventory. When using KBDI-I and KBDI-II, 5-HT increased by 341% and 828% for the normal group and 484% and 257% for the depression tendency group, respectively. The change rate of cortisol was greater in depression tendency groups compared with normal groups, and this difference was statistically significant when using KBDI-II (31% vs. 16% reduction) and Self-rating Depression Scale inventory (36% vs. 8.3% reduction). Among three inventories, only KBDI-II differentiated normal and depression tendency groups with significantly different cortisol level. Finally, clary sage oil has antidepressant-like effect, and KBDI-II inventory may be the most sensitive and valid tool in screening for depression status or severity.

  8. Hypersensitivity of mesenteric veins to 5-hydroxytryptamine- and ketanserin-induced reduction of portal pressure in portal hypertensive rats.

    PubMed Central

    Cummings, S. A.; Groszmann, R. J.; Kaumann, A. J.

    1986-01-01

    Isolated superior mesenteric veins from portal hypertensive rats were 3 to 10 times more sensitive to 5-hydroxytryptamine (5-HT) and 3 times less sensitive to (-)-noradrenaline than veins from sham-operated rats. The sensitivity to vasopressin did not differ in the 2 groups. Ketanserin competitively antagonized the effects of 5-HT in superior mesenteric veins and portal veins with high affinity (KB values 0.1-0.3 nM), as expected for 5-HT2-receptors. The affinity of ketanserin for 5-HT2-receptors was similar in veins from normal, sham-operated or portal-hypertensive rats. Intraportal injections of low doses of 5-HT caused increases in portal pressure which were more pronounced in portal hypertensive rats than in sham-operated rats and were blocked by 0.3 mg kg-1 ketanserin in both groups. Ketanserin 0.3 mg kg-1 did not block the portal pressor response to (-)-noradrenaline in either group of rats. In portal hypertensive rats but not in sham-operated rats, 0.3 mg kg-1 ketanserin caused decreases in portal pressure, portal flow and cardiac output, as estimated by radioactive microspheres. The reduction in portal pressure caused by ketanserin was due mainly to a decrease in portal venous inflow secondary to a decreased cardiac output. The reduction in cardiac output, which was observed only in the portal hypertensive rats but not in sham-operated rats, is consistent with venous dilatation and pooling of blood in the portal venous system. The venous pooling could be secondary to the blockade of 5-HT2-receptors in the portal venous system. It is proposed that ketanserin should be explored for the treatment of patients with portal hypertension. PMID:3801785

  9. Effects of DAU 6215, a novel 5-hydroxytryptamine3 (5-HT3) antagonist on electrophysiological properties of the rat hippocampus.

    PubMed Central

    Passani, M. B.; Pugliese, A. M.; Azzurrini, M.; Corradetti, R.

    1994-01-01

    1. The aim of the present study was to test the effects of DAU 6215 (endo-N-(8-methyl-8-azabicyclo-[3.2.1]-octo-3-yl)-2,3-dihydro-2-ox o-1H- benzimidazole-1-carboxamide carboxamide hydrochloride), a newly synthesized, selective 5-hydroxytryptamine3 (5-HT3) antagonist, on the cell membrane properties and on characterized 5-HT-mediated responses of pyramidal neurones in the hippocampal CA1 region. 2. Administration of DAU 6215, even at concentrations several hundred fold its Ki, did not affect the cell membrane properties of pyramidal neurones, nor modify extracellularly recorded synaptic potentials, evoked by stimulating the Schaffer's collaterals. 3. Micromolar concentrations (15-30 microM) of 5-HT elicited several responses in pyramidal neurones that are mediated by distinct 5-HT receptor subtypes. DAU 6215 did not antagonize the 5-HT1A-induced membrane hyperpolarization and conductance increase, a response that was blocked by the selective 5-HT1A antagonist NAN-190 (1-(2-methoxyphenyl)-4-[4-(2-phtalamido)butyl- piperazine). Similarly, DAU 6215 did not affect the membrane depolarization and decrease in amplitude of the afterhyperpolarization, elicited by the activation of putative 5-HT4 receptors. 4. 5-HT increased the frequency of spontaneous postsynaptic potentials (s.p.s.ps) recorded in pyramidal neurones loaded with chloride. In agreement with previous observations, most of the s.p.s.ps were reversed GABAergic events, produced by the activation of 5-HT3 receptors on interneurones, because they persisted in the presence of the glutamate NMDA and non NMDA antagonists, D-aminophosphonovaleric acid (APV; 50 microM) and 6,7-dinitroquinoxaline-2,3-dione (DNQX; 25 microM), and were elicited by the selective 5-HT3 agonist, 2-methyl-5-HT (2-Me-5-HT, 50 microM).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8075890

  10. Studies of the interaction of 5-hydroxytryptamine and the perivascular innervation of the guinea-pig caecum

    PubMed Central

    Drakontides, Anna B.; Gershon, Michael D.

    1972-01-01

    1. The action and interaction of noradrenaline (NA), 5-hydroxytryptamine (5-HT) and the sympathetic innervation was studied in the isolated taenia of the guinea-pig caecum. 2. Addition of 5-HT led to a contraction of the taenia while addition of NA or perivascular nerve stimulation resulted in relaxation. Responses to 5-HT or perivascular nerve stimulation were abolished by tetrodotoxin. Tetrodotoxin did not affect responses to applied NA. Hexamethonium and hyoscine converted the 5-HT response to a relaxation and augmented the relaxation which followed low frequency perivascular nerve stimulation. Hexamethonium and hyoscine did not affect the dose-response relationship for NA. 3. Fatigue of mechanical responses of the taenia to perivascular nerve stimulation was accelerated when nerves were stimulated in the presence of 5-HT or α-methyl-p-tyrosine (α-MPT). These two agents were additive in this action. 4. Reserpine, 6-hydroxydopamine and α-MPT all reduced the NA content of the taenia. However, only after 6-hydroxydopamine could adrenergic activity be related to NA content. 5. Segments of taenia were incubated with either tritiated NA or 5-HT. An increased rate of release of radioactivity followed perivascular nerve stimulation after incubation with either substance. This release did not occur when tissue was taken from animals given reserpine or 6-hydroxydopamine. 6. It is concluded that 5-HT activates neural elements exclusively while NA has a direct effect on smooth muscle. 5-HT can apparently be taken up by adrenergic axons, and appears to enter the releasable neurotransmitter pool. Since none of the actions characteristic of 5-HT are seen when it is released by adrenergic axons as a false neurotransmitter, the released amine probably fails to reach neuronal receptors for 5-HT. PMID:4342028

  11. Reduced sensitivity to both positive and negative reinforcement in mice over-expressing the 5-hydroxytryptamine transporter.

    PubMed

    Line, Samantha J; Barkus, Chris; Rawlings, Nancy; Jennings, Katie; McHugh, Stephen; Sharp, Trevor; Bannerman, David M

    2014-12-01

    The 5-hydroxytryptamine (5-HT) transporter (5-HTT) is believed to play a key role in both normal and pathological psychological states. Much previous data suggest that the s allele of the polymorphic regulatory region of the 5-HTT gene promoter is associated with reduced 5-HTT expression and vulnerability to psychiatric disorders, including anxiety and depression. In comparison, the l allele, which increases 5-HTT expression, is generally considered protective. However, recent data link this allele to both abnormal 5-HT signalling and psychopathic traits. Here, we studied the processing of aversive and rewarding cues in transgenic mice that over-express the 5-HTT (5-HTTOE mice). Compared with wild-type mice, 5-HTTOE mice froze less in response to both a tone that had previously been paired with footshock, and the conditioning context. In addition, on a decision-making T-maze task, 5-HTTOE mice displayed reduced preference for a larger, delayed reward and increased preference for a smaller, immediate reward, suggesting increased impulsiveness compared with wild-type mice. However, further inspection of the data revealed that 5-HTTOE mice displayed a relative insensitivity to reward magnitude, irrespective of delay. In contrast, 5-HTTOE mice appeared normal on tests of spatial working and reference memory, which required an absolute choice between options associated with either reward or no reward. Overall, the present findings suggest that 5-HTT over-expression results in a reduced sensitivity to both positive and negative reinforcers. Thus, these data show that increased 5-HTT expression has some maladaptive effects, supporting recent suggestions that l allele homozygosity may be a potential risk factor for disabling psychiatric traits.

  12. Treadmill exercise alleviates stress-induced impairment of social interaction through 5-hydroxytryptamine 1A receptor activation in rats.

    PubMed

    Kim, Tae-Woon; Lim, Baek-Vin; Kim, Kijeong; Seo, Jin-Hee; Kim, Chang-Ju

    2015-08-01

    Brain-derived neurotrophic factor (BDNF) and its receptors tyrosine kinase B (trkB), and cyclic adenosine monophosphate response element binding protein (CREB) have been suggested as the neurobiological risk factors causing depressive disorder. Serotonin (5-hydroxytryptamine, 5-HT) plays an important role in the pathogenesis of depression. We in-vestigated the effect of treadmill exercise on social interaction in relation with BDNF and 5-HT expressions following stress in rats. Stress was induced by applying inescapable 0.2 mA electric foot shock to the rats for 7 days. The rats in the exercise groups were forced to run on a motorized treadmill for 30 min once a day for 4 weeks. Social interaction test and western blot for BDNF, TrkB, pCREB, and 5-HT1A in the hippocampus were performed. The results indicate that the spend time with unfamiliar partner was decreased by stress, in contrast, treadmill exercise increased the spending time in the stress-induced rats. Expressions of BDNF, TrkB, and pCREB were decreased by stress, in contrast, treadmill exercise enhanced expressions of BDNF, TrkB, and pCREB in the stress-induced rats. In addition, 5-HT1A receptor expression was de-creased by stress, in contrast, treadmill exercise enhanced 5-HT1A expression in the stress-induced rats. In the present study, treadmill exercise alleviated stress-induced social interaction impairment through enhancing hippocampal plasticity and serotonergic function in the hippocampus. These effects of treadmill exercise are achieved through 5-HT1A receptor activation.

  13. Tong Xie Yao Fang relieves irritable bowel syndrome in rats via mechanisms involving regulation of 5-hydroxytryptamine and substance P.

    PubMed

    Yin, Yue; Zhong, Lei; Wang, Jian-Wei; Zhao, Xue-Ying; Zhao, Wen-Jing; Kuang, Hai-Xue

    2015-04-21

    To investigate whether the Chinese medicine Tong Xie Yao Fang (TXYF) improves dysfunction in an irritable bowel syndrome (IBS) rat model. Thirty baby rats for IBS modeling were separated from mother rats (1 h per day) from days 8 to 21, and the rectum was expanded by angioplasty from days 8 to 12. Ten normal rats were used as normal controls. We examined the effects of TXYF on defection frequency, colonic transit function and smooth muscle contraction, and the expression of 5-hydroxytryptamine (5-HT) and substance P (SP) in colonic and hypothalamus tissues by Western blot and RT-PCT techniques in both normal rats and IBS model rats with characterized visceral hypersensitivity. Defecation frequency was 1.8 ± 1.03 in normal rats and 4.5 ± 1.58 in IBS model rats (P < 0.001). However, the defecation frequency was significantly decreased (3.0 ± 1.25 vs 4.5 ± 1.58, P < 0.05), while the time (in seconds) of colon transit function was significantly increased (256.88 ± 20.32 vs 93.36 ± 17.28, P < 0.001) in IBS + TXYF group rats than in IBS group rats. Increased colonic smooth muscle tension and contract frequency in IBS model rats were significantly decreased by administration of TXYF. Exogenous agonist stimulants increased spontaneous activity and elicited contractions of colon smooth muscle in IBS model rats, and all of these actions were significantly reduced by TXYF involving 5-HT and SP down-regulation. TXYF can modulate the activity of the enteric nervous system and alter 5-HT and SP activities, which may contribute to the symptoms of IBS.

  14. 5-Hydroxytryptamine modulates cytokine and chemokine production in LPS-primed human monocytes via stimulation of different 5-HTR subtypes.

    PubMed

    Dürk, Thorsten; Panther, Elisabeth; Müller, Tobias; Sorichter, Stephan; Ferrari, Davide; Pizzirani, Cinzia; Di Virgilio, Francesco; Myrtek, Daniel; Norgauer, Johannes; Idzko, Marco

    2005-05-01

    The neurotransmitter 5-hydroxytryptamine (5-HT), commonly known as serotonin, is released at peripheral sites from activated enterochromaffin cells, mast cells and platelets. In this study we analyzed the biological activity and intracellular signaling of 5-HT in human monocytes. By reverse transcription (RT) and PCR, messenger RNA (mRNA) expression of 5-HT receptor 1E (5-HTR(1E)), 5-HTR(2A), 5-HTR(3), 5-HTR(4) and 5-HTR(7) could be revealed. Functional studies showed that 5-HT modulates the release of IL-1beta, IL-6, IL-8/CXCL8, IL-12p40 and tumor necrosis factor-alpha (TNF-alpha), while it has no effect on the production of IL-18 and IFN-gamma in LPS-stimulated human blood monocytes. Moreover, RT and PCR revealed that 5-HT modulated mRNA levels of IL-6 and IL-8/CXCL8, but did not influence mRNA levels of IL-1beta and TNF-alpha. Pharmacological studies with isotype-selective receptor agonists allowed us to show that 5-HTR(3) subtype up-regulates the LPS-induced production of IL-1beta, IL-6 and IL-8/CXCL8, while it was not involved in TNF-alpha and IL-12p40 secretion. Furthermore, activation of the G(s)-coupled 5-HTR(4) and 5-HTR(7) subtypes increased intracellular cyclic AMP (cAMP) and secretion of IL-1beta, IL-6, IL-12p40 and IL-8/CXCL8, while, on the contrary, it inhibited LPS-induced TNF-alpha release. Interestingly, 5-HTR(1) and 5-HTR(2) agonists did not modulate the LPS-induced cytokine production in human monocytes. Our results point to a new role for 5-HT in inflammation by modulating cytokine production in monocytes via activation of 5-HTR(3), 5-HTR(4) and 5-HTR(7) subtypes.

  15. The effect of selective 5-hydroxytryptamine uptake inhibitors on 5-methoxy-N,N-dimethyltryptamine-induced ejaculation in the rat.

    PubMed Central

    Rényi, L.

    1986-01-01

    The ejaculatory response and the 5-hydroxytryptamine (5-HT) behavioural syndrome induced by 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) (3 mg kg-1 i.p.) were studied following acute and repeated treatment of rats with the selective uptake inhibitors of 5-HT, fluoxetine, zimeldine, alaproclate, and citalopram. The oral doses used were based on the respective ED50 values for uptake inhibition. Acute doses of fluoxetine and zimeldine significantly reduced the ejaculatory response when given 48 h before 5-MeODMT. This blockade was prevented by treatment of the rats with the postsynaptic 5-HT receptor antagonist methergoline. An acute dose of fluoxetine given 7 and 14 days before 5-MeODMT significantly enhanced the ejaculatory response. On day 24, the response returned to the control level. Repeated treatment every second day (5 times over 9 days and 10 times over 19 days) with fluoxetine caused a longer blockade of the ejaculatory response and the sensitization of the response came later than after an acute dose. Parallel with the ejaculatory response three other components of the 5-HT behavioural syndrome also decreased significantly. Acute doses of alaproclate and citalopram significantly blocked the ejaculatory response at 1 h, but they failed to affect the response at any other time point after either acute or repeated treatment. Neither did these drugs attentuate the 5-HT syndrome. It is concluded that acute and repeated treatment of rats with different selective 5-HT uptake inhibitors does not produce a common alteration in 5-HT2-receptor functions. PMID:2939912

  16. Predictive In Silico Studies of Human 5-hydroxytryptamine Receptor Subtype 2B (5-HT2B) and Valvular Heart Disease

    PubMed Central

    Reid, Terry-Elinor; Kumar, Krishna

    2014-01-01

    Serotonin (5-HT) receptors are neuromodulator neurotransmitter receptors which when activated generate a signal transduction pathway within cells resulting in cell-cell communication. 5-hydroxytryptamine (serotonin) receptor 2B (5-HT2B) is a subtype of the seven members of 5-hydroxytrytamine (5-HT) family of receptors which is the largest member of the super family of 7-transmembrane G-protein coupled receptors (GPCRs). Not only do 5-HT receptors play physiological roles in the cardiovascular system, gastrointestinal and endocrine function and the central nervous, but they also play a role in behavioral functions. In particular 5-HT2B receptor is wide spread with regards to its distribution throughout bodily tissues and is expressed at high levels in the lungs, peripheral tissues, liver, kidney and prostate just to name a few. Hence 5-HT2B participates in multiple biological functions including CNS regulation, regulation of gastrointestinal motality, cardiovascular regulation and 5-HT transport system regulation. While 5-HT2B is a viable drug target and has therapeutic indications for treating obesity, psychotherapy, Parkinson’s disease etc. there is a growing concern regarding adverse drug reactions, specifically valvulopathy associated with 5-HT2B agonists. Due to the sequence homology experienced by 5-HT2 subtypes there is also a concern regarding the off target effects of 5-HT2A and 5-HT2C agonists. The concept of subtype selectivity is of paramount importance and can be tackled with the aid of in silico studies, specifically cheminformatics, to develop models to predict valvulopathy associated toxicity of drug candidates prior to clinical trials. This review has highlighted three in silico approaches thus far that have been successful in either predicting 5-HT2B toxicity of molecules or identifying important interactions between 5-HT2B and drug molecules that bring about valvulopathy related toxicities. PMID:23675941

  17. Treadmill exercise alleviates stress-induced impairment of social interaction through 5-hydroxytryptamine 1A receptor activation in rats

    PubMed Central

    Kim, Tae-Woon; Lim, Baek-Vin; Kim, Kijeong; Seo, Jin-Hee; Kim, Chang-Ju

    2015-01-01

    Brain-derived neurotrophic factor (BDNF) and its receptors tyrosine kinase B (trkB), and cyclic adenosine monophosphate response element binding protein (CREB) have been suggested as the neurobiological risk factors causing depressive disorder. Serotonin (5-hydroxytryptamine, 5-HT) plays an important role in the pathogenesis of depression. We in-vestigated the effect of treadmill exercise on social interaction in relation with BDNF and 5-HT expressions following stress in rats. Stress was induced by applying inescapable 0.2 mA electric foot shock to the rats for 7 days. The rats in the exercise groups were forced to run on a motorized treadmill for 30 min once a day for 4 weeks. Social interaction test and western blot for BDNF, TrkB, pCREB, and 5-HT1A in the hippocampus were performed. The results indicate that the spend time with unfamiliar partner was decreased by stress, in contrast, treadmill exercise increased the spending time in the stress-induced rats. Expressions of BDNF, TrkB, and pCREB were decreased by stress, in contrast, treadmill exercise enhanced expressions of BDNF, TrkB, and pCREB in the stress-induced rats. In addition, 5-HT1A receptor expression was de-creased by stress, in contrast, treadmill exercise enhanced 5-HT1A expression in the stress-induced rats. In the present study, treadmill exercise alleviated stress-induced social interaction impairment through enhancing hippocampal plasticity and serotonergic function in the hippocampus. These effects of treadmill exercise are achieved through 5-HT1A receptor activation. PMID:26331133

  18. Increased extracellular dopamine and 5-hydroxytryptamine levels contribute to enhanced subthalamic nucleus neural activity during exhausting exercise

    PubMed Central

    Hu, Y; Liu, X

    2015-01-01

    The purpose of the study was to explore the mechanism underlying the enhanced subthalamic nucleus (STN) neural activity during exhausting exercise from the perspective of monoamine neurotransmitters and changes of their corresponding receptors. Rats were randomly divided into microdialysis and immunohistochemistry study groups. For microdialysis study, extracellular fluid of the STN was continuously collected with a microdialysis probe before, during and 90 min after one bout of exhausting exercise. Dopamine (DA) and 5-hydroxytryptamine (5-HT) levels were subsequently detected with high-performance liquid chromatography (HPLC). For immunohistochemistry study, the expression of DRD2 and HT2C receptors in the STN, before, immediately after and 90 min after exhaustion was detected through immunohistochemistry technique. Microdialysis study results showed that the extracellular DA and 5-HT neurotransmitters increased significantly throughout the procedure of exhausting exercise and the recovery period (P<0.05 or P<0.01). Immunohistochemistry study results showed that the expression levels of DRD2 and HT2C in the rat STN immediately after exhausting exercise and at the time point of 90 min after exhaustion were both higher than those of the rest condition, but the difference was not significant (P>0.05). Our results suggest that the increased extracellular DA and 5-HT in the STN might be one important factor leading to the enhanced STN neural activity and the development of fatigue during exhausting exercise. This study may essentially offer useful evidence for better understanding of the mechanism of the central type of exercise-induced fatigue. PMID:26424920

  19. The Role of 5-Hydroxytryptamine in the Pathophysiology of Migraine and its Relevance to the Design of Novel Treatments.

    PubMed

    Villalón, Carlos M; VanDenBrink, Antoinette Maassen

    2016-07-28

    Migraine is a highly prevalent neurovascular disorder. Of the many factors that have been implicated over the years, 5-hydroxytryptamine (5-HT; serotonin) has long been involved in the pathophysiology of migraine. Certainly, some lines of evidence suggest: (i) a 5-HT depletion from blood platelets resulting in cranial extracerebral vasodilatation; and (ii) the effectiveness of an intravenous (i.v.) infusion of 5 HT to abort migraine in some patients. More direct evidence comes from some drugs that influence 5-HT release and/or interact (as agonists or antagonists) with 5-HT receptors to treat this disorder. Indeed, the development of sumatriptan and second generation triptans in the 1990's led to discover that these drugs produce selective cranial extracerebral vasoconstriction (via 5 HT1B receptors) and inhibition of the trigeminovascular system responses implicated in migraine (via 5 HT1D/5 HT1F receptors). Although the triptans represent the current mainstay of acute antimigraine treatment, a number of patients do not respond well to the triptans and are contraindicated in patients with cardiovascular pathologies. This mini-review outlines further developments in the design of novel (non-vasoconstrictor) antimigraine treatments acting via 5-HT receptors, including selective agonists at 5 HT1D and 5-HT1F receptors, agonists at 5-HT1B/1D receptors combined with other properties as well as antagonists at 5-HT2B/2C, 5-HT3 and 5 HT7 receptors. It also touches upon the recent development of antagonists and antibodies at calcitonin gene-related peptide (CGRP) and its receptors, which produce a direct blockade of the CGRPergic vasodilator mechanisms involved in migraine. These alternative pharmacological approaches will hopefully lead to less side effects.

  20. Parallel Functional Activity Profiling Reveals Valvulopathogens Are Potent 5-Hydroxytryptamine2B Receptor Agonists: Implications for Drug Safety Assessment

    PubMed Central

    Huang, Xi-Ping; Setola, Vincent; Yadav, Prem N.; Allen, John A.; Rogan, Sarah C.; Hanson, Bonnie J.; Revankar, Chetana; Robers, Matt; Doucette, Chris

    2009-01-01

    Drug-induced valvular heart disease (VHD) is a serious side effect of a few medications, including some that are on the market. Pharmacological studies of VHD-associated medications (e.g., fenfluramine, pergolide, methysergide, and cabergoline) have revealed that they and/or their metabolites are potent 5-hydroxytryptamine2B (5-HT2B) receptor agonists. We have shown that activation of 5-HT2B receptors on human heart valve interstitial cells in vitro induces a proliferative response reminiscent of the fibrosis that typifies VHD. To identify current or future drugs that might induce VHD, we screened approximately 2200 U.S. Food and Drug Administration (FDA)-approved or investigational medications to identify 5-HT2B receptor agonists, using calcium-based high-throughput screening. Of these 2200 compounds, 27 were 5-HT2B receptor agonists (hits); 14 of these had previously been identified as 5-HT2B receptor agonists, including seven bona fide valvulopathogens. Six of the hits (guanfacine, quinidine, xylometazoline, oxymetazoline, fenoldopam, and ropinirole) are approved medications. Twenty-three of the hits were then “functionally profiled” (i.e., assayed in parallel for 5-HT2B receptor agonism using multiple readouts to test for functional selectivity). In these assays, the known valvulopathogens were efficacious at concentrations as low as 30 nM, whereas the other compounds were less so. Hierarchical clustering analysis of the pEC50 data revealed that ropinirole (which is not associated with valvulopathy) was clearly segregated from known valvulopathogens. Taken together, our data demonstrate that patterns of 5-HT2B receptor functional selectivity might be useful for identifying compounds likely to induce valvular heart disease. PMID:19570945

  1. 5-HT1 agonists reduce 5-hydroxytryptamine release in rat hippocampus in vivo as determined by brain microdialysis.

    PubMed Central

    Sharp, T.; Bramwell, S. R.; Grahame-Smith, D. G.

    1989-01-01

    1. An intracerebral perfusion method, brain microdialysis, was used to assess changes of 5-hydroxytryptamine (5-HT) release in the ventral hippocampus of the chloral hydrate-anaesthetized rat in response to systemic administration of a variety of 5-HT1 receptor agonists. 2. A stable output of reliably detectable endogenous 5-HT was measured in dialysates collected from ventral hippocampus with the 5-HT reuptake inhibitor, citalopram, present in the perfusion medium. 3. Under these conditions the putative 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) caused a dose-dependent (5-250 micrograms kg-1, s.c.) reduction of 5-HT in hippocampal dialysates. 4. Similarly, the putative 5-HT1A agonists gepirone (5 mg kg-1, s.c.), ipsapirone (5 mg kg-1, s.c.) and buspirone (5 mg kg-1, s.c.) markedly reduced levels of 5-HT in hippocampal perfusates whereas their common metabolite 1-(2-pyrimidinyl) piperazine (5 mg kg-1, s.c.), which does not bind to central 5-HT1A recognition sites, had no effect. 5. 5-Methoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-indole (RU 24969), a drug with reported high affinity for brain 5-HT1B binding sites, also produced a dose-dependent (0.25-5 mg kg-1, s.c.) decrease of hippocampal 5-HT output. 6. These data are direct biochemical evidence that systemically administered putative 5-HT1A and 5-HT1B agonists markedly inhibit 5-HT release in rat ventral hippocampus in vivo. PMID:2466516

  2. Interaction of tryptamine and ergoline compounds with threonine 196 in the ligand binding site of the 5-hydroxytryptamine6 receptor.

    PubMed

    Boess, F G; Monsma, F J; Meyer, V; Zwingelstein, C; Sleight, A J

    1997-09-01

    We examined the ligand-binding site of the 5-hydroxytryptamine6 (5-HT6) receptor using site-directed mutagenesis. Interactions with residues in two characteristic positions of trans-membrane region V are important for ligand binding in several bioamine receptors. In the 5-HT6 receptor, one of these residues is a threonine (Thr196), whereas in most other mammalian 5-HT receptors, the corresponding residue is alanine. After transient expression in human embryonic kidney 293 cells, we determined the effects of the mutation T196A on [3H]d-lysergic acid diethylamide (LSD) binding and adenylyl cyclase stimulation. This mutation produced a receptor with a 10-fold reduced affinity for [3H]LSD and a 6-fold reduced affinity for 5-HT. The potency of both LSD and 5-HT for stimulation of adenylyl cyclase was also reduced by 18- and 7-fold, respectively. The affinity of other N1-unsubstituted ergolines (e.g., ergotamine, lisuride) was reduced 10-30 fold, whereas the affinity of N1-methylated ergolines (e.g., metergoline, methysergide, mesulergine) and other ligands, such as methiothepine, clozapine, ritanserin, amitriptyline, and mainserin, changed very little or increased. This indicates that in wild-type 5-HT6 receptor, Thr196 interacts with the N1 of N1-unsubstituted ergolines and tryptamines, probably forming a hydrogen bond. Based on molecular modeling, a serine residue in transmembrane region IV of the 5-HT2A receptor has previously been proposed to interact with the N1-position of 5-HT. When the corresponding residue of the 5-HT6 receptor (Ala154) was converted to serine, no change in the affinity of twelve 5-HT6 receptor ligands or in the potency of 5-HT and LSD could be detected, suggesting that this position does not contribute to the ligand binding site of the 5-HT6 receptor.

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

    PubMed Central

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

    1986-01-01

    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.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3742155

  4. Changes in head twitch response induced by a 5-hydroxytryptamine agonist in mice fed a low-protein diet.

    PubMed

    Minakami, K; Shimizu, T; Toriire, Y; Fukuda, T

    1996-01-01

    Long-term intake of a protein diet in infants causes the malnutrition syndrome known as kwashiorkor. Neurological symptoms in kwashiorkor have been reported occasionally. We studied the effects of malnutrition on murine behaviour by feeding growing mice a long-term low-protein diet. Three groups of 3-week-old male ddY mice were fed protein-controlled diets of 8,15 and 25% (control group) of total diet weight for 11 weeks immediately after weaning. The number of head twitches in 2 min were measured 2 min after injection of 10 mg/kg 5 -methoxy- N,N-dimethyltryptamine (5-MeODMT), a 5 -hydroxytryptamine (5 -HT) receptor agonist i.p. Organs were weighed after 10 weeks of feeding. Intracerebral monoamines and their metabolites were assayed using high performance liquid chromatography with electrochemical detection. Bodyweights of mice that were fed the 8% protein diet for 10 weeks were lower than in the other groups. The frequencies of the 5 -MeODMT-induced head twitch in mice that were fed the 8% low-protein diet for 4, 7 and 10 weeks were, respectively, 37.4, 21.4 and 45.2% those of the control group. The frequencies of head twitch also decreased in mice that were fed the 15% low-protein diet for 7 or 10 weeks. The locomotor activity of the mice was unchanged by the amount of protein in the diet. In assays of intracerebral monoamines, 5-HT and 5-HIAA in the whole brain and metabolic turnover of 5-HT increased significantly in mice that were fed the 8% low-protein diet for 11 weeks. Results suggest that head twitches in mice on long-term low-protein diets are suppressed due to the changes in the intracerebral serotonin system.

  5. Contribution of a helix 5 locus to selectivity of hallucinogenic and nonhallucinogenic ligands for the human 5-hydroxytryptamine2A and 5-hydroxytryptamine2C receptors: direct and indirect effects on ligand affinity mediated by the same locus.

    PubMed

    Almaula, N; Ebersole, B J; Ballesteros, J A; Weinstein, H; Sealfon, S C

    1996-07-01

    An important determinant of the neurobehavioral responses induced by a drug is its relative receptor selectivity. The molecular basis of ligand selectivity of hallucinogenic and nonhallucinogenic compounds of varying structural classes for the human 5-hydroxytryptamine (5-HT)2A and 5-HT2C receptors was investigated with the use of reciprocal site-directed mutagenesis. Because these two closely related receptor subtypes differ in the amino acid present at position 5.46 (residues 242 and 222 in the sequences, respectively), the effects of corresponding substitutions in the 5-HT2A[S5.46(242)-->A] and 5-HT2C[A5.46(222)-->S] receptors were studied in tandem. By studying both receptors, the direct and indirect effects of mutations on affinity and selectivity can be distinguished. The ergolines studied, mesulergine (selective for the 5-HT2C receptor) and d-lysergic acid diethylamide (selective for the 5-HT2A receptor), reversed their relative affinity with mutations in each receptor, supporting a direct role of this locus in the selectivity of these ligands. However, interchange mutations in either receptor led to decreased or unchanged affinity for (+/-)-1-)(2,5-dimethoxy-4-iodophenyl)-2-aminopropane and ketanserin, which have higher affinity for the 5-HT2A receptor, consistent with little contribution of this locus to the selectivity of these ligands. The indoleamines studied were affected differently by mutations in each receptor, suggesting that they bind differently to the two receptor subtypes. Mutation of this locus in the 5-HT2A receptor decreased the affinity of all indoleamines, whereas the interchange mutation of the 5-HT2C receptor did not affect indoleamine affinity. These results are consistent with a direct interaction between this side chain and indoleamines for the 5-HT2A receptor but not for the 5-HT2C receptor. Furthermore, this analysis shows that the higher affinity of 5-HT and tryptamine for the 5-HT2C receptor than for the 5-HT2A receptors is not

  6. Histamine and 5-hydroxytryptamine in the intestinal tract of germ-free animals, animals harbouring one microbial species and conventional animals

    PubMed Central

    Beaver, Margaret H.; Wostmann, B. S.

    1962-01-01

    Histamine and 5-hydroxytryptamine were determined in the intestinal tract of germfree and conventional rats and mice. Comparable histamine data were collected in Clostridium perfringens mono-associated rats, while 5-hydroxytryptamine determinations were extended to include the chicken. In rats and mice harbouring an intestinal microflora, bacterial formation of histamine occurs mainly in the caecum. Compared to values found in germ-free animals, histamine levels in the wall of the small intestine of the conventional animal tend to be higher, though in the rat the data are not consistent. Mono-association (harbouring of one microbial species) of germ-free rats with a histamine-producing strain of Clostridium perfringens resulted in high histamine concentrations in the caecal contents, but failed to increase the histamine levels in the wall of the small intestine. 5-Hydroxytryptamine levels in the intestinal wall in the presence of an intestinal flora were generally lower than those in germ-free animals. Modification of the flora by dietary administration of penicillin to mice partly abolished its depressing effect. PMID:13970018

  7. Histamine and 5-hydroxytryptamine in the intestinal tract of germ-free animals, animals harbouring one microbial species and conventional animals.

    PubMed

    BEAVER, M H; WOSTMANN, B S

    1962-12-01

    Histamine and 5-hydroxytryptamine were determined in the intestinal tract of germfree and conventional rats and mice. Comparable histamine data were collected in Clostridium perfringens mono-associated rats, while 5-hydroxytryptamine determinations were extended to include the chicken. In rats and mice harbouring an intestinal microflora, bacterial formation of histamine occurs mainly in the caecum. Compared to values found in germ-free animals, histamine levels in the wall of the small intestine of the conventional animal tend to be higher, though in the rat the data are not consistent. Mono-association (harbouring of one microbial species) of germ-free rats with a histamine-producing strain of Clostridium perfringens resulted in high histamine concentrations in the caecal contents, but failed to increase the histamine levels in the wall of the small intestine. 5-Hydroxytryptamine levels in the intestinal wall in the presence of an intestinal flora were generally lower than those in germ-free animals. Modification of the flora by dietary administration of penicillin to mice partly abolished its depressing effect.

  8. Emesis and Defecations Induced by the 5-Hydroxytryptamine (5-HT3) Receptor Anatagonist Zacopride in the Ferret

    DTIC Science & Technology

    1990-02-16

    vehicle pretreatment in order screened for evidence of disease prior to release from quarantine- to re-establish that a response to zacopride would occur...dorsal vagus primarily innervates the dorsal aspects reported here (n.033 mg/kg). In contrast, Costall et al. (1987) of the stomach and the coeliac ...receptor. This was anatomically beyond the coeliac ganglion (MacKay and An- demonstrated by the reduced emesis seen after pretreatment drews, 1983

  9. Median raphe cyst: report of two cases.

    PubMed

    Kumar, Piyush; Das, Anupam; Savant, Sushil S; Barkat, Rizwana

    2017-02-15

    Median raphe cysts are rare congenital lesions ofthe male genitalia that occur as a result of alteredembryologic development. We report two such casesof median raphe cysts in the pediatric age group. Inaddition, we review the literature.

  10. Projection patterns from the raphe nuclear complex to the ependymal wall of the ventricular system in the rat.

    PubMed

    Simpson, K L; Fisher, T M; Waterhouse, B D; Lin, R C

    1998-09-14

    The goal of the present study was to characterize the anatomical and neurochemical relationships that the raphe nuclear complex maintains with respect to lateralized and centralized components of the ventricular system. From this investigation, we 1) determined the ipsilateral vs. contralateral distribution of raphe efferents to the ependymal wall of the lateral ventricle, 2) assessed the degree of collateralization of individual ependymal projection neurons to other sites along the ventricular path, 3) compared the topography of raphe neurons that project to the ventricular lining as well as the lumen of the fourth and lateral ventricles, and 4) evaluated the neurochemical identity of raphe neurons that innervate the ventricular system. After tracer injections into the lateral ventricle, labeled cells were distributed evenly on both sides of the midline in the dorsomedial subregion of the intermediate dorsal raphe nucleus. Further rostrally, labeled cells were clustered bilaterally above the medial longitudinal fasciculi and extended into the median raphe nucleus. Injections that involved the ependymal wall of the lateral ventricle resulted in prominent ipsilateral labeling within the dorsal raphe nucleus, just ventral to the cerebral aqueduct. Most of the labeled cells in this latter group had collateral projections to other sites along the ventricular path. Most of the ventricle projection cells contained serotonin but not nicotinamide adenine dinucleotide phosphate diaphorase. These findings indicate that the raphe nuclear complex is topographically organized with respect to the ventricular system. Selected subsets of serotoninergic dorsal raphe neurons may influence discrete segments of the ventricular system independently as well as coordinate functions throughout the system through axon collaterals to other sites along the ventricular neuraxis.

  11. The influence of cerebral 5-hydroxytryptamine on catalepsy induced by brain-amine depleting neuroleptics or by cholinomimetics

    PubMed Central

    Fuenmayor, Luis D.; Vogt, Marthe

    1979-01-01

    1 Catalepsy was produced in rats and mice by the subcutaneous injection of either tetrabenazine or the butyrophenone U-32,802A (4′-fluoro-4-{[4-(p-fluorophenyl)-3-cyclohexen-1-yl]amino} butyrophenone hydrochloride). Catalepsy was evaluated by the duration of total immobility on a vertical grid. 2 Pretreatment with p-chlorophenylalanine (PCPA) reduced the intensity of catalepsy by 50% or more, whereas its time course remained the same. 3 5-Hydroxytryptophan (5-HTP), 10 mg/kg, enhanced the catalepsy induced by U-32,802A or tetrabenazine, provided it was administered soon (45 min) after the neuroleptic; injections at 90 min had no effect. Otherwise untreated rats given this dose of 5-HTP behaved normally on the grid. 4 The anticataleptic effect of PCPA was reversed by 5-HTP. 5 Measurable changes in 5-hydroxytryptamine (5-HT) metabolism in the rat forebrain accompanied the modification of catalepsy by 5-HTP and PCPA. 6 Methysergide (5 mg/kg) given 30 min before the neuroleptics to either mice or rats reduced the catalepsy, assessed 2.5 h after the methysergide. It also prevented the increase in neuroleptic-induced catalepsy following 5-HTP, 10 mg/kg. 7 Tryptophan, like 5-HTP, increased the catalepsy seen in mice after U-32,802A and tetrabenazine, and increased the production of 5-hydroxyindol-3-ylacetic acid in the forebrain. 8 In the rat, intracerebroventricular injection of physostigmine produced catalepsy which was not modified by methysergide or PCPA but was abolished by atropine. Similarly, in the mouse, catalepsy induced by the subcutaneous injection of pilocarpine was abolished by atropine but not affected by either methysergide or 5-HTP. 9 Atropine greatly reduced the catalepsy induced by U-32,802A and tetrabenazine but lowered striatal homovanillic acid (HVA) only after U-32,802A. D,L-DOPA, 20 mg/kg, diminished the cataleptogenic effect of both neuroleptics and raised striatal HVA. 10 The results support the view that there is a facilitating or permissive

  12. Antagonism of fenfluramine-induced hyperthermia in rats by some, but not all, selective inhibitors of 5-hydroxytryptamine uptake.

    PubMed Central

    Sugrue, M. F.

    1984-01-01

    The injection of fenfluramine (7.5 mg kg-1,i.p.) to rats housed at 27-28 degrees C was associated with an elevation of core body temperature which peaked at approximately 1 h post-injection. One h pretreatment with citalopram (20 mg kg-1, i.p.), chlorimipramine (10 mg kg-1, i.p.), femoxetine (10 mg kg-1, i.p.) and fluoxetine (20 mg kg-1, i.p.) resulted in an attenuated response to fenfluramine. In contrast, Org 6582 (20 mg kg-1) and zimelidine (20 mg kg-1) were devoid of an effect on fenfluramine-induced hyperthermia. The response to fenfluramine was was also blocked by i.p. injections of metergoline (0.2 mg kg-1), methysergide (5 mg kg-1) and mianserin (0.5 mg kg-1). Rectal temperature was unaltered by both the 5-hydroxytryptamine (5-HT) uptake inhibitors and the 5-HT receptor antagonists. The IC50 values (nM) for in vitro inhibition of [3H]-5-HT uptake into rat hypothalamic synaptosomes were for citalopram 2.4, chlorimipramine 8.8, femoxetine 14, fluoxetine 16, Org 6582 75 and zimelidine 250. The injection of all six compounds (20 mg kg-1, i.p.) 1 h before death was associated with an inhibition of [3H]-5-HT uptake into rat hypothalamic synaptosomes which ranged from 47.2% for chlorimipramine to 83.3% for citalopram. Rat hypothalamic 5-HT levels were decreased by approximately 50% 3 h after the injection of fenfluramine (15 mg kg-1, i.p.). This effect was blocked by a 1 h pretreatment with fluoxetine, Org 6582 and zimelidine (all 20 mg kg-1, i.p.). Ki values for displacement of specifically bound [3H]-5-HT (1 nM) to rat hypothalamic membranes were for metergoline 26 nM, methysergide 1.1 microM, mianserin 3.6 microM, chlorimipramine 9.2 microM and fluoxetine 32.7 microM. Values for citalopram, femoxetine, Org 6582 and zimelidine were in excess of 65.4 microM.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6722394

  13. Adrenoceptor- and cholinoceptor-mediated mechanisms in the regulation of 5-hydroxytryptamine release from isolated tracheae of newborn rabbits.

    PubMed Central

    Freitag, A.; Wessler, I.; Racké, K.

    1996-01-01

    1. Isolated tracheae of newborn rabbits were incubated in vitro and the outflow of 5-hydroxytryptamine (5-HT) was determined by h.p.l.c. with electrochemical detection. Evidence has previously been provided that this 5-HT outflow derives from neuroendocrine epithelial (NEE) cells of the airway mucosa. 2. Phenylephrine (1, 10 and 30 microM) enhanced the outflow of 5-HT by 80, 290 and 205%, respectively. 5-HT outflow evoked by 10 microM phenylephrine was not affected by the presence of the neurotoxin tetrodotoxin (1 microM). 3. Rauwolscine, ARC 239 (an alpha(2B)-adrenoceptor preferring antagonist), yohimbine and prazosin antagonized the effect of 10 microM phenylephrine in a concentration-dependent manner with IC50 values of 150, 295, 300 and 1,700 nM, respectively. Comparison of the ratios (between all antagonists) of the present IC50 values with the corresponding ratios of Ki values obtained in binding studies for the alpha(2A)-, alpha(2B)-, alpha(2C)- and alpha(2D)-adrenoceptor subtypes strongly suggests the involvement of an alpha(2B)-receptor. 4. 5-HT outflow evoked by 10 microM phenylephrine was inhibited by 65% in the presence of 1 microM forskolin and abolished in the presence of 10 microM forskolin. 5. 5-HT outflow evoked by 10 microM phenylephrine was inhibited by about 45 and 70% in the presence of 0.1 and 1 microM isoprenaline, respectively. The inhibitory effect of 1 microM isoprenaline was only marginally antagonized by 1 microM, but blocked by 10 microM propranolol. 6. 5-HT outflow was not affected by the muscarine receptor agonist oxotremorine (10 microM), but was enhanced by 175% by 100 microM nicotine. The effect of nicotine was blocked by 100 microM hexamethonium and prevented by 1 microM tetrodotoxin or 1 microM yohimbine. 7. In conclusion, 5-HT release from NEE cells of the rabbit trachea is stimulated via alpha-adrenoceptors most likely of the alpha(2B)-subtype localized directly at the NEE cells. Activation of beta-adrenoceptors as well as

  14. The human oral raphe system. Architectonics and neuronal types in pigment-Nissl preparations.

    PubMed

    Ohm, T G; Heilmann, R; Braak, H

    1989-01-01

    Serial sections (15 microns, 120 microns, and 400 microns) of nine brain stems treated with a combined lipofuscin pigment-Nissl stain were examined in order to delineate the three-dimensional conformation and subdivisions as well as the neuronal types of the human oral raphe system. Characteristic lipofuscin deposits within the somata of various cell types facilitated the demarcation of the oral raphe nuclei from surrounding structures. The dorsal, central, and linear raphe nuclei, e.g. the major subdivisions of the oral raphe system, share common traits as far as neuronal composition and pigmentation is concerned. The interfascicular subnucleus, the dorsofascicular subnucleus, and the intercalate subnucleus are minor subdivisions of the dorsal raphe nucleus. The intercalate one cannot be differentiated from surrounding areas in preparations solely stained for Nissl-material, while it can facilely be identified in combined pigment-Nissl preparations by virtue of differences in the pigmentation pattern. Our architectonical concept of the oral raphe system is in good accordance with the one derived from immunocytochemical investigations of serotonin-containing neurons in the human brain stem. Furthermore, five main neuronal types are described which constitute the oral raphe nuclei. They have been differentiated according to their characteristics as seen in combined pigment-Nissl preparations. I) Large ovoid to polygonal neurons with densely packed and intensely stained pigment granules. II) Similarly featured cells displaying dust-fine and faintly stained pigment granules. III) Medium-sized, ovoid to polygonal neurons with loosely distributed, small pigment granules. IV) Small ovoid neurons devoid of pigment or with only few, intensely stained granules. V) Small spindle-shaped nerve cells with various amounts of intensely stained pigment granules.(ABSTRACT TRUNCATED AT 250 WORDS)

  15. Involvement of 5-hydroxytryptamine 5-HT₃ serotonergic receptors in the acquisition and reinstatement of the conditioned place preference induced by MDMA.

    PubMed

    Roger-Sánchez, Concepción; Rodríguez-Arias, Marta; Miñarro, Jose; Aguilar, Maria A

    2013-08-15

    Some MDMA (3,4-methylenedioxymethamphetamine) users develop dependence as a result of chronic consumption. The present study evaluated the role of 5-hydroxytryptamine 5-HT₃ receptors in the acquisition, expression and reinstatement of the conditioned place preference (CPP) induced by MDMA. Adolescent male mice were conditioned with 10 mg/kg of MDMA and then treated with 1 or 3mg/kg of the 5-hydroxytryptamine 5-HT₃ antagonist MDL72222 during acquisition of conditioning (experiment 1), before expression of CPP in a post-conditioning test (experiment 2) or before a reinstatement test (experiment 3). MDL72222 was devoid of motivational effects but blocked acquisition of the MDMA-induced CPP. Moreover, following extinction, the low dose of MDL72222 blocked reinstatement of the CPP induced by priming with MDMA. Acute MDMA reduced levels of dihydroxypheylacetic acid (DOPAC) in the striatum and levels of acid 5-hydroxyindoleacetic (5-HIAA) in the cortex. Acute MDMA+MDL72222 also reduced striatal DOPAC. The repeated co-administration of MDMA plus MDL72222 (on PND 32-34-36-38) increased dopamine and decreased DOPAC in the striatum, and increased cortical serotonin and enhanced transporters of dopamine and serotonin. The acute administration (on PND ±55) of MDMA or MDL72222 increased levels of dopamine and reduced those of DOPAC in the striatum and co-administration of MDMA plus MDL72222 increased striatal serotonin. Our results confirm that 5-hydroxytryptamine 5-HT₃ receptors are involved in the acquisition of conditioned rewarding effects of MDMA and demonstrate that these receptors are also involved in reinstatement after extinction.

  16. Blockade of 5-hydroxytryptamine3 receptors prevents cisplatin-induced but not motion- or xylazine-induced emesis in the cat

    NASA Technical Reports Server (NTRS)

    Lucot, J. B.

    1989-01-01

    5-Hydroxytryptamine3 antagonists have been reported to prevent emesis elicited by cisplatin and radiation. This study investigated the possibility that drugs with this mechanism of action may be useful in preventing emesis elicited by other stimuli. The drugs ICS 205-930 (0.1 and 1.0 mg/kg) and MDL 72222 (0.1 and 1.0 mg/kg) were administered SC to cats before challenging them with either provocative motion or an emetic dose of xylazine. In no instance was a significant reduction in emesis evident. Zacopride was also administered before motion testing (0.01 to 10.0 mg/kg) and found to not have efficacy. To test the possibility that species or route of administration were factors in the negative results, 1.0 mg/kg of ICS 205-930 was administered SC before IV infusion of 7.5 mg/kg of cisplatin. There was a total suppression of emesis for the duration of the six-hour observation periods. This result verifies other work which found 5-hydroxytryptamine3 antagonists to be effective in preventing emesis elicited by cancer chemotherapeutic treatments. However, there is no evidence that they are effective in other syndromes, such as motion sickness and xylazine-induced emesis.

  17. Does pharmacogenomics account for variability in control of acute chemotherapy-induced nausea and vomiting with 5-hydroxytryptamine type 3 receptor antagonists?

    PubMed

    Trammel, Morgan; Roederer, Mary; Patel, Jai; McLeod, Howard

    2013-06-01

    Chemotherapy-induced nausea and vomiting is one of the most concerning adverse drug effects from cytotoxic chemotherapy. Despite appropriate use of antiemetic guidelines, 20-30 % of patients experience breakthrough nausea and vomiting secondary to chemotherapy. To assess the variability of 5-hydroxytryptamine type 3 receptor antagonist efficacy caused by genetic variation, a review of the available literature was conducted. From the literature, three sources of pharmacogenomic variability were identified: polymorphisms associated with 5-hydroxytryptamine type 3 receptor subunits, drug metabolism via cytochromes P450, and drug transport in the body. Testing for receptor subunit polymorphisms is not applicable to a clinical setting at this time; however, cytochrome P450 2D6 testing is FDA-approved and widely accessible. Cytochrome P450 2D6 ultrarapid metabolizers and poor metabolizers displayed altered antiemetic efficacy when compared with intermediate metabolizers and extensive metabolizers. We postulate that testing for cytochrome P450 2D6 phenotypes may be the most accessible way to provide individualized antiemetic therapy in the future.

  18. Blockade of 5-hydroxytryptamine3 receptors prevents cisplatin-induced but not motion- or xylazine-induced emesis in the cat

    NASA Technical Reports Server (NTRS)

    Lucot, J. B.

    1989-01-01

    5-Hydroxytryptamine3 antagonists have been reported to prevent emesis elicited by cisplatin and radiation. This study investigated the possibility that drugs with this mechanism of action may be useful in preventing emesis elicited by other stimuli. The drugs ICS 205-930 (0.1 and 1.0 mg/kg) and MDL 72222 (0.1 and 1.0 mg/kg) were administered SC to cats before challenging them with either provocative motion or an emetic dose of xylazine. In no instance was a significant reduction in emesis evident. Zacopride was also administered before motion testing (0.01 to 10.0 mg/kg) and found to not have efficacy. To test the possibility that species or route of administration were factors in the negative results, 1.0 mg/kg of ICS 205-930 was administered SC before IV infusion of 7.5 mg/kg of cisplatin. There was a total suppression of emesis for the duration of the six-hour observation periods. This result verifies other work which found 5-hydroxytryptamine3 antagonists to be effective in preventing emesis elicited by cancer chemotherapeutic treatments. However, there is no evidence that they are effective in other syndromes, such as motion sickness and xylazine-induced emesis.

  19. Benefits of Hormone Therapy Estrogens Depend on Estrogen Type: 17β-Estradiol and Conjugated Equine Estrogens Have Differential Effects on Cognitive, Anxiety-Like, and Depressive-Like Behaviors and Increase Tryptophan Hydroxylase-2 mRNA Levels in Dorsal Raphe Nucleus Subregions

    PubMed Central

    Hiroi, Ryoko; Weyrich, Giulia; Koebele, Stephanie V.; Mennenga, Sarah E.; Talboom, Joshua S.; Hewitt, Lauren T.; Lavery, Courtney N.; Mendoza, Perla; Jordan, Ambra; Bimonte-Nelson, Heather A.

    2016-01-01

    Decreased serotonin (5-HT) function is associated with numerous cognitive and affective disorders. Women are more vulnerable to these disorders and have a lower rate of 5-HT synthesis than men. Serotonergic neurons in the dorsal raphe nucleus (DRN) are a major source of 5-HT in the forebrain and play a critical role in regulation of stress-related disorders. In particular, polymorphisms of tryptophan hydroxylase-2 (TpH2, the brain-specific, rate-limiting enzyme for 5-HT biosynthesis) are implicated in cognitive and affective disorders. Administration of 17β-estradiol (E2), the most potent naturally circulating estrogen in women and rats, can have beneficial effects on cognitive, anxiety-like, and depressive-like behaviors. Moreover, E2 increases TpH2 mRNA in specific subregions of the DRN. Although conjugated equine estrogens (CEE) are a commonly prescribed estrogen component of hormone therapy in menopausal women, there is a marked gap in knowledge regarding how CEE affects these behaviors and the brain 5-HT system. Therefore, we compared the effects of CEE and E2 treatments on behavior and TpH2 mRNA. Female Sprague-Dawley rats were ovariectomized, administered either vehicle, CEE, or E2 and tested on a battery of cognitive, anxiety-like, and depressive-like behaviors. The brains of these animals were subsequently analyzed for TpH2 mRNA. Both CEE and E2 exerted beneficial behavioral effects, although efficacy depended on the distinct behavior and for cognition, on the task difficulty. Compared to CEE, E2 generally had more robust anxiolytic and antidepressant effects. E2 increased TpH2 mRNA in the caudal and mid DRN, corroborating previous findings. However, CEE increased TpH2 mRNA in the caudal and rostral, but not the mid, DRN, suggesting that distinct estrogens can have subregion-specific effects on TpH2 gene expression. We also found differential correlations between the level of TpH2 mRNA in specific DRN subregions and behavior, depending on the type of

  20. Prophylaxis of Radiation-Induced Nausea and Vomiting Using 5-Hydroxytryptamine-3 Serotonin Receptor Antagonists: A Systematic Review of Randomized Trials

    SciTech Connect

    Salvo, Nadia; Doble, Brett; Khan, Luluel; Amirthevasar, Gayathri; Dennis, Kristopher; Pasetka, Mark; DeAngelis, Carlo; Tsao, May; Chow, Edward

    2012-01-01

    Purpose: To systematically review the effectiveness and safety of 5-hydroxytryptamine-3 receptor antagonists (5-HT3 RAs) compared with other antiemetic medication or placebo for prophylaxis of radiation-induced nausea and vomiting. Methods and Materials: We searched the following electronic databases: MEDLINE, Embase, the Cochrane Central Register of Controlled Clinical Trials, and Web of Science. We also hand-searched reference lists of included studies. Randomized, controlled trials that compared a 5-HT3 RA with another antiemetic medication or placebo for preventing radiation-induced nausea and vomiting were included. We excluded studies recruiting patients receiving concomitant chemotherapy. When appropriate, meta-analysis was conducted using Review Manager (v5) software. Relative risks were calculated using inverse variance as the statistical method under a random-effects model. We assessed the quality of evidence by outcome using the Grading of Recommendations Assessment, Development, and Evaluation approach. Results: Eligibility screening of 47 articles resulted in 9 included in the review. The overall methodologic quality was moderate. Meta-analysis of 5-HT3 RAs vs. placebo showed significant benefit for 5-HT3 RAs (relative risk [RR] 0.70; 95% confidence interval [CI] 0.57-0.86 for emesis; RR 0.84, 95% CI 0.73-0.96 for nausea). Meta-analysis comparing 5-HT3 RAs vs. metoclopramide showed a significant benefit of the 5-HT3 RAs for emetic control (RR 0.27, 95% CI 0.15-0.47). Conclusion: 5-Hydroxytryptamine-3 RAs are superior to placebo and other antiemetics for prevention of emesis, but little benefit was identified for nausea prevention. 5-Hydroxytryptamine-3 RAs are suggested for prevention of emesis. Limited evidence was found regarding delayed emesis, adverse events, quality of life, or need for rescue medication. Future randomized, controlled trials should evaluate different 5-HT3 antiemetics and new agents with novel mechanisms of action such at the NK

  1. Development of the serotonergic cells in murine raphe nuclei and their relations with rhombomeric domains.

    PubMed

    Alonso, Antonia; Merchán, Paloma; Sandoval, Juan E; Sánchez-Arrones, Luisa; Garcia-Cazorla, Angels; Artuch, Rafael; Ferrán, José L; Martínez-de-la-Torre, Margaret; Puelles, Luis

    2013-09-01

    The raphe nuclei represent the origin of central serotonergic projections. The literature distinguishes seven nuclei grouped into rostral and caudal clusters relative to the pons. The boundaries of these nuclei have not been defined precisely enough, particularly with regard to developmental units, notably hindbrain rhombomeres. We hold that a developmental point of view considering rhombomeres may explain observed differences in connectivity and function. There are twelve rhombomeres characterized by particular genetic profiles, and each develops between one and four distinct serotonergic populations. We have studied the distribution of the conventional seven raphe nuclei among these twelve units. To this aim, we correlated 5-HT-immunoreacted neurons with rhombomeric boundary landmarks in sagittal mouse brain sections at different developmental stages. Furthermore, we performed a partial genoarchitectonic analysis of the developing raphe nuclei, mapping all known serotonergic differentiation markers, and compared these results, jointly with others found in the literature, with our map of serotonin-containing populations, in order to examine regional variations in correspondence. Examples of regionally selective gene patterns were identified. As a result, we produced a rhombomeric classification of some 45 serotonergic populations, and suggested a corresponding modified terminology. Only a minor rostral part of the dorsal raphe nucleus lies in the midbrain. Some serotonergic neurons were found in rhombomere 4, contrary to the conventional assumption that it lacks such neurons. We expect that our reclassification of raphe nuclei may be useful for causal analysis of their differential molecular specification, as well as for studies of differential connectivity and function.

  2. Blockade of 5-hydroxytryptamine(3) receptors prevents cisplatin-induced but not motion- or xylazine-induced emesis in the cat

    NASA Technical Reports Server (NTRS)

    Lucot, James B.

    1989-01-01

    The effects of the 5-hydroxytryptamine(3) (5-HT-3) antagonists ICS 205-930 and MDL 72222 on the emesis induced by motion or by emetic doses of xylazine (0.66 mg/kg administered SC) or cisplatin (7.5 mg/kg infused over a period of 4-5 min) were investigated in cats. It was found that neither the low (0.1 mg/kg) or the high (1.0 mg.kg) doses of ICS 205-930 or MDL 72222 prevented emesis elicited by screening motion challenges or xylazine. On the other hand, treatment cats by 1.0 mg/kg of ICS 205-930 was effective against cisplatin-induced motion sickness, in agreement with earlier results obtained on other mammals.

  3. 5-hydroxytryptamine receptor (5-HT1DR) promotes colorectal cancer metastasis by regulating Axin1/β-catenin/MMP-7 signaling pathway

    PubMed Central

    Ji, Qing; Liu, Xuan; Zhou, Lihong; Song, Haiyan; Zhou, Xiqiu; Xu, Yangxian; Chen, Zhesheng; Cai, Jianfeng; Ji, Guang; Li, Qi

    2015-01-01

    Overexpression of 5-hydroxytryptamine (5-HT) in human cancer contributes to tumor metastasis, but the role of 5-HT receptor family in cancer has not been thoroughly explored. Here, we report overexpression of 5-HT1D receptor (5-HT1DR) was associated with Wnt signaling pathway and advanced tumor stage. The underlying mechanism of 5-HT1DR-promoted tumor invasion was through its activation on the Axin1/β-catenin/MMP-7 pathway. In an orthotopic colorectal cancer mouse model, we demonstrated that a 5-HT1DR antagonist (GR127935) effectively inhibited tumor metastasis through targeting Axin1. Furthermore, in intestinal epithelium cells, we observed that 5-HT1DR played an important role in cell invasion via Axin1/β-catenin/MMP-7 pathway. Together, our findings reveal an essential role of the physiologic level of 5-HT1DR in pulmonary metastasis of colorectal cancer. PMID:26214021

  4. Effects of p-chlorophenylalanine on the sensitivity of rat intestine to agonists and on intestinal 5-hydroxytryptamine levels during Nippostrongylus brasiliensis infection.

    PubMed Central

    Farmer, S. G.; Laniyonu, A. A.

    1984-01-01

    Infection of rats with the nematode N. brasiliensis caused non-specific increases in maximum response of isolated intestine to acetylcholine and 5-hydroxytryptamine (5-HT), and a specific subsensitivity to 5-HT. Intestinal levels of 5-HT, measured fluorimetrically, increased approximately 2 fold during infection. Treatment of infected rats with parachlorophenylalanine (PCPA) depleted the gut of 5-HT, and prevented the specific subsensitivity to the amine but not the increases in maximum response. Depletion of intestinal 5-HT did not prevent the immune expulsion of the parasites. It is concluded that the specific subsensitivity of the gut is due to the elevated levels of 5-HT during infection, but that the increased maximum responses are due to some other factor. Further, the lack of effect of PCPA on parasite rejection casts doubt on the proposed role of 5-HT in this process. PMID:6236863

  5. Comparison of the performance of different DFT methods in the calculations of the molecular structure and vibration spectra of serotonin (5-hydroxytryptamine, 5-HT)

    NASA Astrophysics Data System (ADS)

    Yang, Yue; Gao, Hongwei

    2012-04-01

    Serotonin (5-hydroxytryptamine, 5-HT) is a monoamine neurotransmitter which plays an important role in treating acute or clinical stress. The comparative performance of different density functional theory (DFT) methods at various basis sets in predicting the molecular structure and vibration spectra of serotonin was reported. The calculation results of different methods including mPW1PW91, HCTH, SVWN, PBEPBE, B3PW91 and B3LYP with various basis sets including LANL2DZ, SDD, LANL2MB, 6-31G, 6-311++G and 6-311+G* were compared with the experimental data. It is remarkable that the SVWN/6-311++G and SVWN/6-311+G* levels afford the best quality to predict the structure of serotonin. The results also indicate that PBEPBE/LANL2DZ level show better performance in the vibration spectra prediction of serotonin than other DFT methods.

  6. Blockade of 5-hydroxytryptamine(3) receptors prevents cisplatin-induced but not motion- or xylazine-induced emesis in the cat

    NASA Technical Reports Server (NTRS)

    Lucot, James B.

    1989-01-01

    The effects of the 5-hydroxytryptamine(3) (5-HT-3) antagonists ICS 205-930 and MDL 72222 on the emesis induced by motion or by emetic doses of xylazine (0.66 mg/kg administered SC) or cisplatin (7.5 mg/kg infused over a period of 4-5 min) were investigated in cats. It was found that neither the low (0.1 mg/kg) or the high (1.0 mg.kg) doses of ICS 205-930 or MDL 72222 prevented emesis elicited by screening motion challenges or xylazine. On the other hand, treatment cats by 1.0 mg/kg of ICS 205-930 was effective against cisplatin-induced motion sickness, in agreement with earlier results obtained on other mammals.

  7. Adolescence fluoxetine increases serotonergic activity in the raphe-hippocampus axis and improves depression-like behaviors in female rats that experienced neonatal maternal separation.

    PubMed

    Yoo, Sang Bae; Kim, Bom-Taeck; Kim, Jin Young; Ryu, Vitaly; Kang, Dong-Won; Lee, Jong-Ho; Jahng, Jeong Won

    2013-06-01

    This study was conducted to examine if fluoxetine, a selective 5-hydroxytryptamine (5-HT) reuptake inhibitor, would reverse adverse behavioral effects of neonatal maternal separation in female rats. Sprague-Dawley pups were separated from dam daily for 3h during postnatal day (PND) 1-14 (maternal separation; MS) or left undisturbed (non-handled; NH). Female NH and MS pups received intraperitoneal injection of fluoxetine (10mg/kg) or vehicle daily from PND 35 until the end of the whole experimental period. Rats were either subjected to behavioral tests during PND 44-54, or sacrificed for neurochemical analyses during PND 43-45. Daily food intake and weight gain of both NH and MS pups were suppressed by fluoxetine, with greater effects in MS pups. MS experience increased immobility and decrease swimming in forced swim test. Swimming was increased, although immobility was not significantly decreased, in MS females by adolescence fluoxetine. However, adolescence fluoxetine increased immobility during forced swim test and decreased time spent in open arms during elevated plus maze test in NH females. Fluoxetine normalized MS-induced decrease of the raphe 5-HT levels and increased 5-HT metabolism in the hippocampus in MS females, and increased the hypothalamic 5-HT both in NH and MS. Fluoxetine decreased the raphe 5-HT and increased the plasma corticosterone in NH females. Results suggest that decreased 5-HTergic activity in the raphe nucleus is implicated in the pathophysiology of depression-like behaviors, and increased 5-HTergic activities in the raphe-hippocampus axis may be a part of anti-depressant efficacy of fluoxetine, in MS females. Also, an extra-hypothalamic 5-HTergic activity may contribute to the increased anorectic efficacy of fluoxetine in MS females. Additionally, decreased 5-HT in the raphe and elevated plasma corticosterone may be related with fluoxetine-induced depression- and/or anxiety-like behaviors in NH females.

  8. Anococcygeal Raphe Revisited: A Histological Study Using Mid-Term Human Fetuses and Elderly Cadavers

    PubMed Central

    Arakawa, Takashi; Abe, Hiroshi; Abe, Shinichi; Cho, Baik Hwan; Murakami, Gen; Sugihara, Kenichi

    2012-01-01

    Purpose We recently demonstrated the morphology of the anococcygeal ligament. As the anococcygeal ligament and raphe are often confused, the concept of the anococcygeal raphe needs to be re-examined from the perspective of fetal development, as well as in terms of adult morphology. Materials and Methods We examined the horizontal sections of 15 fetuses as well as adult histology. From cadavers, we obtained an almost cubic tissue mass containing the dorsal wall of the anorectum, the coccyx and the covering skin. Most sections were stained with hematoxylin and eosin or Masson-trichrome solution. Results The adult ligament contained both smooth and striated muscle fibers. A similar band-like structure was seen in fetuses, containing: 1) smooth muscle fibers originating from the longitudinal muscle coat of the anal canal and 2) striated muscle fibers from the external anal sphincter (EAS). However, in fetuses, the levator ani muscle did not attach to either the band or the coccyx. Along and around the anococcygeal ligament, we did not find any aponeurotic tissue with transversely oriented fibers connecting bilateral levator ani slings. Instead, in adults, a fibrous tissue mass was located at a gap between bilateral levator ani slings; this site corresponded to the dorsal side of the ligament and the EAS in the immediately deep side of the natal skin cleft. Conclusion We hypothesize that a classically described raphe corresponds to the specific subcutaneous tissue on the superficial or dorsal side of the anococcygeal ligament. PMID:22665356

  9. Disruption of raphé serotonergic neural projections to the cortex: a potential pathway contributing to remote loss of brainstem neurons following neonatal hypoxic-ischemic brain injury.

    PubMed

    Reinebrant, Hanna E; Wixey, Julie A; Buller, Kathryn M

    2012-12-01

    Neuronal injury is a key feature of neonatal hypoxic-ischemic (HI) brain injury. However, the mechanisms underpinning neuronal losses, such as in the brainstem, are poorly understood. One possibility is that disrupted neural connections between the cortex and brainstem may compromise the survival of neuronal cell bodies in the brainstem. We investigated whether brainstem raphé serotonergic neurons that project to the cortex are lost after HI. We also tested if neuroinflammation has a role in disrupting brainstem raphé projections. Postnatal day 3 (P3) rats underwent unilateral carotid artery ligation followed by hypoxia (6% oxygen for 30 min). A retrograde tracer, choleratoxin b, was deposited in the motor cortex on P38. On P45 we found that retrogradely labelled neurons in the dorsal raphé dorsal, ventrolateral, interfascicular, caudal and ventral nuclei were lost after P3 HI. All retrogradely labelled neurons in the raphé nuclei were serotonergic. Numbers of retrogradely labelled neurons were also reduced in the ventromedial thalamus and basolateral amygdala. Minocycline treatment (45 mg/kg 2 h post-HI, 22.5 mg/kg daily P4-P9) attenuated losses of retrogradely labelled neurons in the dorsal raphé ventrolateral, interfascicular and ventral raphé nuclei, and the ventromedial thalamus. These results indicate that raphé neurons projecting to the cortex constitute a population of serotonergic neurons that are lost after P3 HI. Furthermore, neuroinflammation has a role in the disruption of raphé and thalamic neural projections. Future studies investigating the cellular mechanisms of axonal degeneration may reveal new targets for interventions to prevent neuronal losses after neonatal HI.

  10. The effect of three products of cigarette smoke (cyanide, thiocyanate and nicotine) on the concentration-response curves of 5-hydroxytryptamine, norepinephrine and epinephrine in the isolated human umbilical veins and arteries.

    PubMed

    Tunçel, N; Aydin, Y; Tikiz, H

    1994-02-01

    The effect of cyanide (10(-7) M), thiocyanate (10(-4) M) and nicotine (10(-7) M) on the concentration-response curves of 5-hydroxytryptamine, norepinephrine and epinephrine were investigated in human isolated umbilical arteries and veins. Cyanide significantly affected the responses of arterial strips to 5-hydroxytryptamine, norepinephrine and epinephrine: It caused significant leftward shifts of the 5-hydroxytryptamine concentration-response curves and significantly potentiated the contractile effects of norepinephrine and epinephrine in the case of norepinephrine, and epinephrine concentration reached 10(-6) and 10(-7) M respectively in the bath medium. Cyanide did not show any significant effect on the concentration-response curves of 5-hydroxytryptamine, norepinephrine and epinephrine in veins. Nicotine interacted with the response of adrenergic agonists both in arteries and veins; in arteries it potentiates the contractile response of epinephrine; in veins, it inhibited the dilatory responses of norepinephrine and potentiated the contractile effect of high concentration of epinephrine (10(-6) M). Thiocyanate did not cause any difference on any cumulative concentration-response curves either on the vessels. However, none of these individual effects of cyanide and nicotine were observed when the cyanide, thiocyanate and nicotine were added in combination in the isolated organ bath medium.

  11. A phase 1 randomized study evaluating the effect of omeprazole on the pharmacokinetics of a novel 5-hydroxytryptamine receptor 4 agonist, revexepride (SSP-002358), in healthy adults

    PubMed Central

    Pierce, David; Corcoran, Mary; Velinova, Maria; Hossack, Stuart; Hoppenbrouwers, Mieke; Martin, Patrick

    2015-01-01

    Background About 30% of patients with gastroesophageal reflux disease continue to experience symptoms despite treatment with proton pump inhibitors. The 5-hydroxytryptamine 4 receptor agonist revexepride (SSP-002358) is a novel prokinetic that stimulates gastrointestinal motility, which has been suggested as a continued cause of symptoms in these patients. The aim of this study was to assess whether revexepride pharmacokinetics were affected by co-administration of omeprazole, in preparation for a proof-of-concept evaluation of revexepride added to proton pump inhibitor treatment. Methods In this phase 1, open-label, randomized, two-period crossover study, healthy adults aged 18–55 years were given a single dose of revexepride 1 mg or revexepride 1 mg + omeprazole 40 mg. Pharmacokinetic parameters were assessed for up to 48 hours after administration of the investigational product. Adverse events, clinical chemistry and hematology parameters, electrocardiograms, and vital signs were monitored. Results In total, 42 participants were enrolled and 40 completed the study. The median age was 24 years (18–54 years), 55% were women and 93% were white. The pharmacokinetic parameters of revexepride were similar without or with omeprazole co-administration. The mean area under the plasma concentration–time curve from time 0 to infinity (AUC0–∞) was 23.3 ng · h/mL (standard deviation [SD]: 6.33 ng · h/mL) versus 24.6 ng · h/mL (SD: 6.31 ng · h/mL), and maximum plasma concentrations (Cmax) were 3.89 ng/mL (SD: 1.30 ng/mL) and 4.12 ng/mL (SD: 1.29 ng/mL) in participants without and with omeprazole, respectively. For AUC0–∞ and Cmax, the 90% confidence intervals for the ratios of geometric least-squares means (with:without omeprazole) were fully contained within the pre-defined equivalence limits of 0.80–1.25. Mean apparent terminal phase half-life was 9.95 hours (SD: 2.06 hours) without omeprazole, and 11.0 hours (SD: 3.25 hours) with omeprazole. Conclusion

  12. Decrease in serotonin concentration in raphe magnus nucleus and attenuation of morphine analgesia in two mice models of neuropathic pain.

    PubMed

    Sounvoravong, Sourisak; Nakashima, Mihoko N; Wada, Mitsuhiro; Nakashima, Kenichiro

    2004-01-26

    The alleviation of neuropathic pain cannot be satisfactorily achieved by treatment with opioids. There is much evidence to indicate that the active site of morphine for inducing effective analgesia is in the raphe magnus nucleus, where serotonin (5-HT, 5-hydroxytryptamine) acts as a primary transmitter. Therefore, we developed the hypothesis that 5-HT released in the raphe magnus nucleus could be related to the effectiveness of morphine in two mice models of neuropathic pain, diabetic (DM)-induced neuropathy and sciatic nerve ligation (SL). Two weeks after a single administration of streptozotocin, or 10 days after sciatic nerve ligation, mice were subcutaneously (s.c.) injected with morphine at 3, 5 and 10 mg/kg. The antinociceptive effect of morphine was estimated in the tail-pinch test; 5-HT content was measured after induction of neuropathic pain by microdialysis followed by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). Morphine produced as insufficient antinociceptive effect in SL mice at all doses compared with that in sham-operated mice, while in DM mice, morphine given s.c. at 5 and 10 mg/kg produced antinociceptive effects compared with those in non-diabetic mice, but not at 3 mg/kg. The 5-HT content of dialysates, expressed as AUC for 75 min, in SL and DM mice was less than that in control mice. However, morphine given s.c. at 5 mg/kg did not significantly affect 5-HT levels in both mice models compared to their controls. These results suggest that the decrease in 5-HT levels in the raphe magnus nucleus may be related to attenuation of the analgesic effect of morphine caused by the abnormal pain state found in diabetes and partial peripheral nerve injury.

  13. Simultaneous determination of 5-hydroxyindoleacetic acid and 5-hydroxytryptamine in urine samples from patients with acute appendicitis by liquid chromatography using poly(bromophenol blue) film modified electrode.

    PubMed

    Xu, Haihong; Zhang, Wen; Wang, Dan; Zhu, Wei; Jin, Litong

    2007-02-01

    The fabrication and application of a novel electrochemical detection (ED) system with a poly(bromophenol blue) (PBPB) film chemically modified electrode (CME) for high performance liquid chromatography (HPLC) were described. The electrochemical behaviors of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) at this CME were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that the PBPB CME efficiently exhibited electrocatalytic effect on the current responses of 5-HT and 5-HIAA with relatively high sensitivity, stability and long life of activity. In HPLC-ED, the two analytes had good and stable current responses at the CME and their linear ranges were over four orders of magnitude (R> or =0.9992) with the detection limits being 0.25 nmol L(-1) for 5-HT and 0.50 nmol L(-1) for 5-HIAA. The application of this method for the determination of 5-HT and 5-HIAA in urine samples from patients with acute appendicitis (AA) was satisfactory.

  14. gamma-Aminobutyric acid-A receptor-mediated suppression of 5-hydroxytryptamine-induced guinea-pig basilar artery smooth muscle contractility.

    PubMed

    Shirakawa, J; Hosoda, K; Taniyama, K; Matsumoto, S; Tanaka, C

    1989-01-01

    The mechanism of gamma-aminobutyric acid (GABA)-induced suppression of 5-hydroxytryptamine (5HT)-induced contractility of cerebral blood vessels was studied in single smooth muscle cells isolated from the guinea-pig basilar artery. GABA reduced 5HT-induced contraction of single smooth muscle cells, and the effect of GABA was mimicked by muscimol, but not baclofen. The response of muscimol was antagonized by bicuculline, thereby indicating that GABAA receptors exist on the smooth muscle of the basilar artery. Since GABA did not change the contraction induced by the addition of Ca2+ to the Ca2+-free medium in the presence of high K+, it is unlikely that GABA inhibits the influx of extracellular Ca2+. The caffeine-induced contraction in the Ca2+-free medium was reduced by GABA, and the effect of GABA was not obtained by treatment with furosemide and in the Cl- -free medium. These results indicate that GABA acts on the GABAA receptor located on smooth muscle cells and reduces the contractility of the basilar artery by suppression of the mobilization of intracellular Ca2+.

  15. Detection of 5-hydroxytryptamine (5-HT) in vitro using a hippocampal neuronal network-based biosensor with extracellular potential analysis of neurons.

    PubMed

    Hu, Liang; Wang, Qin; Qin, Zhen; Su, Kaiqi; Huang, Liquan; Hu, Ning; Wang, Ping

    2015-04-15

    5-hydroxytryptamine (5-HT) is an important neurotransmitter in regulating emotions and related behaviors in mammals. To detect and monitor the 5-HT, effective and convenient methods are demanded in investigation of neuronal network. In this study, hippocampal neuronal networks (HNNs) endogenously expressing 5-HT receptors were employed as sensing elements to build an in vitro neuronal network-based biosensor. The electrophysiological characteristics were analyzed in both neuron and network levels. The firing rates and amplitudes were derived from signal to determine the biosensor response characteristics. The experimental results demonstrate a dose-dependent inhibitory effect of 5-HT on hippocampal neuron activities, indicating the effectiveness of this hybrid biosensor in detecting 5-HT with a response range from 0.01μmol/L to 10μmol/L. In addition, the cross-correlation analysis of HNNs activities suggests 5-HT could weaken HNN connectivity reversibly, providing more specificity of this biosensor in detecting 5-HT. Moreover, 5-HT induced spatiotemporal firing pattern alterations could be monitored in neuron and network levels simultaneously by this hybrid biosensor in a convenient and direct way. With those merits, this neuronal network-based biosensor will be promising to be a valuable and utility platform for the study of neurotransmitter in vitro.

  16. Chemocentric informatics approach to drug discovery: identification and experimental validation of selective estrogen receptor modulators as ligands of 5-hydroxytryptamine-6 receptors and as potential cognition enhancers.

    PubMed

    Hajjo, Rima; Setola, Vincent; Roth, Bryan L; Tropsha, Alexander

    2012-06-28

    We have devised a chemocentric informatics methodology for drug discovery integrating independent approaches to mining biomolecular databases. As a proof of concept, we have searched for novel putative cognition enhancers. First, we generated Quantitative Structure-Activity Relationship (QSAR) models of compounds binding to 5-hydroxytryptamine-6 receptor (5-HT(6)R), a known target for cognition enhancers, and employed these models for virtual screening to identify putative 5-HT(6)R actives. Second, we queried chemogenomics data from the Connectivity Map ( http://www.broad.mit.edu/cmap/ ) with the gene expression profile signatures of Alzheimer's disease patients to identify compounds putatively linked to the disease. Thirteen common hits were tested in 5-HT(6)R radioligand binding assays and ten were confirmed as actives. Four of them were known selective estrogen receptor modulators that were never reported as 5-HT(6)R ligands. Furthermore, nine of the confirmed actives were reported elsewhere to have memory-enhancing effects. The approaches discussed herein can be used broadly to identify novel drug-target-disease associations.

  17. The effects of single and repeated electroconvulsive shock administration on the release of 5-hydroxytryptamine and noradrenaline from cortical slices of rat brain.

    PubMed Central

    Green, A. R.; Heal, D. J.; Vincent, N. D.

    1987-01-01

    1 A method is described of measuring the K+-evoked release of endogenous 5-hydroxytryptamine (5-HT) and noradrenaline (NA) from slices prepared from rat cortex. 2 There was no difference in either the spontaneous (basal) or K+-evoked release of 5-HT or NA from cortical slices prepared from handled animals and those given a single electroconvulsive shock (ECS) either 30 min or 24 h earlier. 3 In chronic studies, rats were either handled or given an ECS 5 times over 10 days and cortical slices prepared. There was no difference in 5-HT or NA release between the groups 30 min after the last treatment other than a modest attentuation of spontaneous NA release following ECS treatment. However 24 h after the last treatment K+-evoked release (above basal release) of 5-HT and NA was inhibited by 84% and 48%, respectively. 4 These data demonstrate that following a single ECS, normal 5-HT and NA release is seen at a time when GABA release is markedly inhibited. After repeated ECS the release of both monoamines was markedly inhibited. These 5-HT changes may be involved in the enhanced 5-HT-receptor function seen after repeated ECS. PMID:3664089

  18. The mechanism of body temperature changes induced by intraventricular injections of adrenaline, noradrenaline and 5-hydroxytryptamine in the ox (bos taurus)

    PubMed Central

    Findlay, J. D.; Robertshaw, D.

    1967-01-01

    1. Adrenaline, noradrenaline and 5-hydroxytryptamine (5-HT) were injected into the lateral ventricle of the ox. The effect of these drugs was measured on the respiratory rate, tidal volume, heat production, skin temperature of the ear, evaporative loss from the skin and the rectal temperature at 20 and 10° C ambient temperature. 2. Neither adrenaline (3 mg) nor noradrenaline (3 mg) had any effect on the temperature regulating mechanisms of the ox, except to produce vasoconstriction if vasodilatation was already present due to high ambient temperature or previous injection of 5-HT. 3. Injection of 5-HT (5 mg) caused a rise in respiratory rate, a fall in tidal volume and heat production, elevation of ear skin temperature and skin evaporative loss and a decrease in rectal temperature. Sedation of the animals occurred. 4. In its reaction to these monoamines the ox is similar to the goat, sheep and rabbit, but is unlike the cat and dog. 5. It was concluded that neither adrenaline nor noradrenaline has a role in the central control of temperature regulation in the ox, but that 5-HT may be involved in the control of heat dissipation mechanisms. PMID:6034117

  19. Effects of 5,7-dihydroxytryptamine on an identified 5-hydroxytryptamine-containing neurone in the central nervous sytem of the snail Helix pomatia.

    PubMed

    Osborne, N N; Pentreath, V W

    1976-01-01

    1. The effect of 5,7-dihydroxytryptamine (5,7-DHT) on an identified 5-hydroxytryptamine (5-HT)-containing neurone in the CNS of the snail was studied by histochemical, biochemical and electrophysiological methods. 2. Low concentrations of 5,7-DHT decreased the endogenous 5-HT content of the neurone without affecting the amino acids, while relatively large amounts of the drug proportionately lowered 5-HT and in addition slightly decreased the tryptophan and methionine content of the cell. 3. 5,7-DHT blocked the uptake of [3H]-5-HT into the neurone; the close analogue 5,6-DHT was more potent. 4. As well as slightly influencing the accumulation of [3H]-tryptophan by the neurone 5,7-DHT inhibited the metabolism of this amino acid to form 5-HT, probably by affecting the enzyme tryptophan-hydroxylase. 5. 5,7-DHT produced a postsynaptic blockade of transmission from the neurone by blocking the 5-HT receptors of the follower neurones. This effect appeared to be specific for 5-HT receptors. 6. The data support the idea that 5,7-DHT is neurotoxic for indoleamine-containing neurones.

  20. Interaction between the effects of 5-hydroxytryptamine and adrenaline on the growth of platelet thrombi in the coronary artery of the anaesthetized dog.

    PubMed Central

    McAuliffe, S. J.; Snow, H. M.; Cox, B.; Smith, C. C.; Noble, M. I.

    1993-01-01

    1. The interaction between adrenaline and 5-hydroxytryptamine (5-HT) has been quantitated on the rate of thrombus formation, in the stenosed coronary artery with damaged endothelium of the anaesthetized dog. 2. Changes in the plasma concentration of adrenaline were produced by varying the rate of an intravenous infusion of adrenaline and in the effects of 5-HT, by intravenous injections of the selective 5-HT2 receptor antagonist, ICI 170809. 3. Increases in the plasma concentration of adrenaline, which did not cause significant changes in blood pressure and heart rate, increased the rate of thrombus formation. 4. Antagonism of the 5-HT2 receptor by ICI 170809, in the absence of an infusion of adrenaline, abolished thrombus formation (mean ED50 0.41 microgram kg-1, i.v.). 5. The effects of adrenaline were non-competitively antagonized by ICI 170809; maximum effects were obtained in the dose-range 50-200 micrograms kg-1, i.v., when the mean dose-ratio increase in adrenaline required to restore equivalent rates of thrombus formation was 39 fold. 6. These results are consistent with a synergism between adrenaline and 5-HT and emphasize the importance of both on thrombus formation. PMID:8358542

  1. Sensitive determination of norepinephrine, epinephrine, dopamine and 5-hydroxytryptamine by coupling HPLC with [Ag(HIO6 )2 ](5-) -luminol chemiluminescence detection.

    PubMed

    Wu, Dong; Xie, He; Lu, Haifeng; Li, Wei; Zhang, Qunlin

    2016-09-01

    Based on the enhancing effects of norepinephrine (NE), epinephrine (EP), dopamine (DA) and 5-hydroxytryptamine (5-HT) on the chemiluminescence (CL) reaction between [Ag(HIO6 )2 ](5-) and luminol in alkaline solution, a high-performance liquid chromatography (HPLC) method with CL detection was explored for the sensitive determination of monoamine neurotransmitters for the first time. The UV-visible absorption spectra were recorded to study the enhancement mechanism of monoamine neurotransmitters on the CL of [Ag(HIO6 )2 ](5-) and luminol reaction. The HPLC separation of NE, EP, DA and 5-HT was achieved with isocratic elution using a mixture of aqueous 0.2% phosphoric acid and methanol (5:95, v/v) within 11.0 min. Under the optimized conditions, the detection limits of NE, EP, DA, and 5-HT were 4.8, 0.9, 1.9 and 2.3 ng/mL, respectively, corresponding to 17.6-96.0 pg for 20 μL sample injection. The recoveries of monoamine neurotransmitters in rat brain were >95.6% with the precisions expressed by RSD <5.0%. The validated HPLC-CL method was successfully applied for the quantification of NE, EP, DA and 5-HT in rat brain. This method has promising potential for some biological and clinical investigations focusing on the levels of monoamine neurotransmitters. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  2. Simultaneous quantification of 5-hydroxyindoleacetic acid and 5-hydroxytryptamine by capillary electrophoresis with quantum dot and horseradish peroxidase enhanced chemiluminescence detection.

    PubMed

    Zhang, Liangliang; Zhao, Yunsha; Huang, Junming; Zhao, Shulin

    2014-09-15

    A capillary electrophoresis (CE) with chemiluminescence (CL) detection method was developed for the simultaneous quantification of 5-hydroxyindoleacetic acid (5-HIAA) and 5-hydroxytryptamine (5-HT). In this method, CdTe quantum dot (QD) and horseradish peroxidase (HRP) were used as enhancing reagents to co-catalyze the post-column CL reaction between luminol and hydrogen peroxide, achieving highly efficient CL emission. 5-HIAA and 5-HT inhibit the CL emission resulting to the formation of negative peaks in electropherogram. The degree of CL suppression is proportional to the concentration of 5-HT and 5-HIAA. The linear ranges for the determination of 5-HIAA and 5-HT were 2.5×10(-8)-2.5×10(-6) M and 2.5×10(-8)-5.0×10(-6) M with detection limits (signal/noise=3) of 7.0×10(-9) M and 6.0×10(-9) M, respectively. Intraday precision do not exceed 5.0%. The accuracy was confirmed by the recoveries ranged from 98% to 104%. The present method was successfully applied for the quantification of 5-HIAA and 5-HT in human urine. The concentrations of 5-HT and 5-HIAA in human urine were found to be in the range of 0.78-1.2 μM and 3.2-5.1 μM, respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Changes in the regulation of 5-hydroxytryptamine release by alpha2-adrenoceptors in the rat hippocampus after long-term desipramine treatment.

    PubMed

    Yoshioka, M; Matsumoto, M; Numazawa, R; Togashi, H; Smith, C B; Saito, H

    1995-12-29

    In vivo microdialysis was used to measure the effects of long-term treatment of rats with desipramine upon the regulation by alpha2-adrenoceptors of serotonin (5-hydroxytryptamine, 5-HT) release from the serotonergic neurons in the hippocampus. Rats were injected with saline or desipramine, 10 mg/kg, i.p., every 12 h for 14 days. When added to the perfusion solution, brimonidine, an alpha2-adrenoceptor agonist, significantly inhibited the K+-evoked release of 5-HT in the hippocampi of saline-treated, control rats. This action of brimonidine was prevented by pretreating the rats with idazoxan, an alpha2-adrenoceptor antagonist. Long-term desipramine treatment significantly reduced the inhibitory effect of brimonidine upon the K+-evoked 5-HT release. With long-term administration of desipramine, noradrenaline content in the hippocampi was significantly decreased as compared with that of the control rats, whereas the basal noradrenaline concentration in the dialysate was significantly increased. On the other hand, both the 5-HT content of the hippocampus and the basal 5-HT concentration in the dialysate were significantly increased. The present study suggests that long-term administration of desipramine causes a functional subsensitivity of the presynaptic alpha2-adrenoceptors that regulate serotonergic neuronal function in the rat hippocampus. It also supports the concept that changes in the sensitivity of alpha2-adrenoceptors that regulate neurotransmitter release play an important role in the mechanism of antidepressant drug action.

  4. The 5-hydroxytryptamine transporter is functional in human coronary artery smooth muscle cells proliferation and is regulated by Interleukin-1 beta

    PubMed Central

    Wang, Qing-Jie; Wang, Dong; Tang, Cheng-Chun

    2015-01-01

    Abnormal human coronary artery smooth muscle cells (hCASMCs) proliferation and migration are key factors in coronary artery restenosis after percutaneous coronary intervention. Platelets release 5-hydroxytryptamine (5-HT), which is a strong mitogen for pulmonary artery smooth muscle cells proliferation and migration. Here, we investigated the effects of 5-HT and role of 5-HT transporter (5-HTT) on hCASMCs proliferation and migration. The 5-HT (10-6-10-5 mol/l) significantly increased hCASMCs proliferation and migration, and these effects were inhibited by fluoxetine (10-5 mol/l) and citalopram (10-6 mol/l), two 5-HTT blocker. Overexpression in hCASMCs enhanced 5-HT induced cells proliferation and migration. The 5-HTT and interleukin-1 beta (IL-1β) expression were increased in rat balloon injury carotid arteries. Treatment with IL-1β (10 ng/ml, 3d) upregulates 5-HTT expression in hCASMCs and increased 5-HT induced currents in Human Embryonic Kidney 293-5-HTT cells. PMID:26221231

  5. Separate 5-hydroxytryptamine receptors on the salivary gland of the blowfly are linked to the generation of either cyclic adenosine 3',5'-monophosphate or calcium signals.

    PubMed Central

    Berridge, M. J.; Heslop, J. P.

    1981-01-01

    1 5'-Hydroxytryptamine (5-HT) stimulates the formation of two separate second messengers in the salivary gland of the blowfly. Activation of adenylate cyclase raises adenosine 3',5'-monophosphate (cyclic AMP) whereas the hydrolysis of phosphatidylinositol (PI) is associated with an increase in calcium permeability. The possibility that these two signal pathways might be controlled by separate 5-HT receptors was studied by testing the specificity of 5-HT analogues and antagonists. 2 The parent compound 5-HT was found to stimulate both cyclic AMP formation and the related parameters of PI hydrolysis and calcium transport with similar dose-response relationships. 3 Certain analogues such as 4- and 5-fluoro-alpha-methyltryptamine were capable of raising cyclic AMP levels and stimulating fluid secretion but did not stimulate the hydrolysis of PI or the entry of calcium. 4 Other analogues, which had chloro or methyl substituents at the 5-position, were found to stimulate the hydrolysis of PI and the transport of calcium at much lower doses than those required to stimulate the formation of cyclic AMP. 5 Antagonists were also found to exert selective effects. Methysergide was a potent inhibitor of PI hydrolysis whereas cinanserin was far more selective in blocking the stimulatory effect of 5-HT on cyclic AMP formation. 6 It is concluded that 5-HT acts on two separate receptors, a 5-HT1 receptor acting through calcium and a 5-HT2 receptor which mediates its effects through cyclic AMP. PMID:6265018

  6. Effects of methysergide and 5-hydroxytryptamine on carotid blood flow distribution in pigs: further evidence for the presence of atypical 5-HT receptors.

    PubMed Central

    Saxena, P. R.; Verdouw, P. D.

    1984-01-01

    The effects of acute (50-350 micrograms kg-1, i.v.) and subacute (350 micrograms kg-1 orally per day for six days) administration of methysergide, and of intra-arterial infusions of 0.5 and 2.0 micrograms kg-1 min-1 5-hydroxytryptamine (5-HT) on the distribution of carotid blood flow into the capillary (nutrient) and arterio-venous anastomotic (AVA) fractions were studied in anaesthetized pigs. The acute, but not the subacute, administration of methysergide caused a moderate reduction of carotid blood flow. This reduction, noticed only in the AVA fraction, was due to a constriction of the arterio-venous anastomoses (AVAs). Both doses of 5-HT reduced total carotid blood flow but its nutrient fraction--particularly that distributed to the skin and ears--increased substantially. The AVA fraction was greatly diminished. After treatment with methysergide, 5-HT no longer reduced the total carotid blood flow, but increased it. Despite this reversal the constriction of AVAs by the amine was only slightly diminished. On the other hand, the vasodilatation of the nutrient channels was enhanced. The results of the interaction between methysergide and 5-HT provide further evidence for the presence of 'atypical' 5-HT receptors (probably corresponding to 5-HT1 binding sites) mediating AVA contraction and nutrient vasodilatation. The 5-HT2 receptors mediate vasoconstriction and are located in the large conducting arteries and possibly, in smaller numbers, in the AVAs and arterioles. PMID:6478112

  7. The effect of noradrenaline and 5-hydroxytryptamine injected into a lateral cerebral ventricle, on thermoregulation in the new-born lamb.

    PubMed Central

    Cooper, K E; Pittman, Q J; Veale, W L

    1976-01-01

    1. Respiratory frequency, shivering, ear skin temperatures and rectal temperatures were observed following intraventricular injections of noradrenaline (NA), 5-hydroxytryptamine (5-HT) and saline (NaCl) into new-born lambs exposed to ambient temperatures of 4, 21, or 30 degrees C. 2. Intraventricular NA caused respiratory rate to decrease and body temperature to increase in the 30 degrees C environment. At 21 degrees C, it increased ear skin temperature but did not significantly affect rectal temperature. At 4 degrees C, NA decreased shivering and rectal temperature fell. 3. 5-HT elevated respiratory rate in the 30 degrees C environment and increased ear skin temperature in the 21 and 4 degrees C environments. In the 4 degrees C environment rectal temperature decreased. 4. In general, the change in rectal temperature was related to the dosage of drug administered. Control injections of NaCl had no significant effect on any of the variables measured. 5. The monoaminergic pathways involved in thermoregulation in the new-born lamb appear to be organized in a manner similar to that of the adult sheep and are functional at birth. PMID:994031

  8. Interaction between the effects of spinal heating and cooling and of injections into a lateral cerebral ventricle of noradrenaline, 5-hydroxytryptamine and carbachol on thermoregulation in sheep.

    PubMed Central

    Bacon, M; Bligh, J

    1976-01-01

    1. A study has been made of the interactions of the thermoregulatory effects of spinal cord heating and cooling and of the injections into the cerebral ventricle of noradrenaline, 5-hydroxytryptamine (5-HT) and carbamylcholine in sheep. 2. The interactions of spinal cord heating and the injections into the cerebral ventricle of noradrenaline, 5-HT and carbamylcholine were very similar to those of hypothalamic heating or of high ambient temperature and the injections into the cerebral ventricle of these substances. These results are interpreted as evidence of the synaptic convergence of the pathways from peripheral, spinal cord and hypothalamic warm-sensors at or before the points of action of these synaptically active substances. 3. The only definite thermoregulatory effect of spinal cooling was the onset of shivering which could be due to a purely spinal effect of cold. No substantial evidence was obtained of an interaction between spinal cooling and an injection of noradrenaline, 5-HT or carbamylcholine into the cerebral ventricle. Thus there was no clear indication of centripetal pathways from spinal cold sensors converging with those from the skin and the hypothalamus for which evidence of convergence was obtained in an earlier study. 4. The results of this study are expressed in terms of the neuronal model of Bligh, Cottle & Maskrey (1971) and Maskrey & Bligh (1971), appropriately modified. PMID:1249731

  9. Effects of 5,7-dihydroxytryptamine on an identified 5-hydroxytryptamine-containing neurone in the central nervous sytem of the snail Helix pomatia.

    PubMed Central

    Osborne, N N; Pentreath, V W

    1976-01-01

    1. The effect of 5,7-dihydroxytryptamine (5,7-DHT) on an identified 5-hydroxytryptamine (5-HT)-containing neurone in the CNS of the snail was studied by histochemical, biochemical and electrophysiological methods. 2. Low concentrations of 5,7-DHT decreased the endogenous 5-HT content of the neurone without affecting the amino acids, while relatively large amounts of the drug proportionately lowered 5-HT and in addition slightly decreased the tryptophan and methionine content of the cell. 3. 5,7-DHT blocked the uptake of [3H]-5-HT into the neurone; the close analogue 5,6-DHT was more potent. 4. As well as slightly influencing the accumulation of [3H]-tryptophan by the neurone 5,7-DHT inhibited the metabolism of this amino acid to form 5-HT, probably by affecting the enzyme tryptophan-hydroxylase. 5. 5,7-DHT produced a postsynaptic blockade of transmission from the neurone by blocking the 5-HT receptors of the follower neurones. This effect appeared to be specific for 5-HT receptors. 6. The data support the idea that 5,7-DHT is neurotoxic for indoleamine-containing neurones. Images Figure 1 Figure 3 PMID:1252663

  10. A slow voltage-dependent Na(+)-current induced by 5-hydroxytryptamine and the G-protein-coupled activation mechanism in the ganglion cells of Aplysia.

    PubMed

    Kudo, A; Sasaki, K; Tamazawa, Y; Matsumoto, M

    1991-01-01

    Application of 5-hydroxytryptamine (5HT) induces a slowly depolarizing response in the neurons of Aplysia abdominal ganglion. In voltage-clamped cells, 5HT induced a slow inward current that increased steeply with membrane depolarization from -85 mV showing a negative slope conductance, but never reversed into outward when hyperpolarized beyond the equilibrium potential for K+. The 5HT-induced response was markedly augmented in Ca(2+)-free media, but depressed in Na(+)-free media, and unaffected by a change in external potassium. Intracellular injection of guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) significantly depressed the 5HT response in a dose-dependent way. Injection of cholera toxin (CTX) selectively blocked the 5HT-induced response, the effect being irreversible. Neither 3'-deoxyadenosine, an inhibitor of adenylate cyclase, nor H-8, an inhibitor of protein kinase A, depressed the 5HT response. 3-Isobutyl-1-methylxanthine (IBMX) did not augment the 5HT response appreciably. The 5HT responses were not depressed at all during a saturated response to Br-cyclic AMP injected intracellularly. It was concluded that the 5HT response is produced by opening of the voltage-dependent Na(+)-channels with activation of CTX-sensitive G-protein but not necessarily with an increase in intracellular cyclic AMP.

  11. Pharmacological profile of lurasidone, a novel antipsychotic agent with potent 5-hydroxytryptamine 7 (5-HT7) and 5-HT1A receptor activity.

    PubMed

    Ishibashi, Tadashi; Horisawa, Tomoko; Tokuda, Kumiko; Ishiyama, Takeo; Ogasa, Masaaki; Tagashira, Rie; Matsumoto, Kenji; Nishikawa, Hiroyuki; Ueda, Yoko; Toma, Satoko; Oki, Hitomi; Tanno, Norihiko; Saji, Ikutaro; Ito, Akira; Ohno, Yukihiro; Nakamura, Mitsutaka

    2010-07-01

    Lurasidone [(3aR,4S,7R,7aS)-2-[(1R,2R)-2-[4-(1,2-benzisothiazol-3-yl)piperazin-1-ylmethyl]cyclohexylmethyl]hexahydro-4,7-methano-2H-isoindole-1,3-dione hydrochloride; SM-13496] is an azapirone derivative and a novel antipsychotic candidate. The objective of the current studies was to investigate the in vitro and in vivo pharmacological properties of lurasidone. Receptor binding affinities of lurasidone and several antipsychotic drugs were tested under comparable assay conditions using cloned human receptors or membrane fractions prepared from animal tissue. Lurasidone was found to have potent binding affinity for dopamine D(2), 5-hydroxytryptamine 2A (5-HT(2A)), 5-HT(7), 5-HT(1A), and noradrenaline alpha(2C) receptors. Affinity for noradrenaline alpha(1), alpha(2A), and 5-HT(2C) receptors was weak, whereas affinity for histamine H(1) and muscarinic acetylcholine receptors was negligible. In vitro functional assays demonstrated that lurasidone acts as an antagonist at D(2) and 5-HT(7) receptors and as a partial agonist at the 5-HT(1A) receptor subtype. Lurasidone showed potent effects predictive of antipsychotic activity, such as inhibition of methamphetamine-induced hyperactivity and apomorphine-induced stereotyped behavior in rats, similar to other antipsychotics. Furthermore, lurasidone had only weak extrapyramidal effects in rodent models. In animal models of anxiety disorders and depression, treatment with lurasidone was associated with significant improvement. Lurasidone showed a preferential effect on the frontal cortex (versus striatum) in increasing dopamine turnover. Anti-alpha(1)-noradrenergic, anticholinergic, and central nervous system (CNS) depressant actions of lurasidone were also very weak. These results demonstrate that lurasidone possesses antipsychotic activity and antidepressant- or anxiolytic-like effects with potentially reduced liability for extrapyramidal and CNS depressant side effects.

  12. Translational evaluation of JNJ-18038683, a 5-hydroxytryptamine type 7 receptor antagonist, on rapid eye movement sleep and in major depressive disorder.

    PubMed

    Bonaventure, Pascal; Dugovic, Christine; Kramer, Michelle; De Boer, Peter; Singh, Jaskaran; Wilson, Sue; Bertelsen, Kirk; Di, Jianing; Shelton, Jonathan; Aluisio, Leah; Dvorak, Lisa; Fraser, Ian; Lord, Brian; Nepomuceno, Diane; Ahnaou, Abdellah; Drinkenburg, Wilhelmus; Chai, Wenying; Dvorak, Curt; Sands, Steve; Carruthers, Nicholas; Lovenberg, Timothy W

    2012-08-01

    In rodents 5-hydroxytryptamine type 7 (5-HT(7)) receptor blockade has been shown to be effective in models of depression and to increase the latency to rapid eye movement (REM) sleep and decrease REM duration. In the clinic, the REM sleep reduction observed with many antidepressants may serve as a biomarker. We report here the preclinical and clinical evaluation of a 5-HT(7) receptor antagonist, (3-(4-chlorophenyl)-1,4,5,6,7,8-hexahydro-1-(phenylmethyl)pyrazolo[3,4-d]azepine 2-hydroxy-1,2,3-propanetricarboxylate) (JNJ-18038683). In rodents, JNJ-18038683 increased the latency to REM sleep and decreased REM duration, and this effect was maintained after repeated administration for 7 days. The compound was effective in the mouse tail suspension test. JNJ-18038683 enhanced serotonin transmission, antidepressant-like behavior, and REM sleep suppression induced by citalopram in rodents. In healthy human volunteers JNJ-18038683 prolonged REM latency and reduced REM sleep duration, demonstrating that the effect of 5-HT(7) blockade on REM sleep translated from rodents to humans. Like in rats, JNJ-18038683 enhanced REM sleep suppression induced by citalopram in humans, although a drug-drug interaction could not be ruled out. In a double-blind, active, and placebo-controlled clinical trial in 225 patients suffering from major depressive disorder, neither treatment with pharmacologically active doses of JNJ-18038683 or escitalopram separated from placebo, indicating a failed study lacking assay sensitivity. Post hoc analyses using an enrichment window strategy, where all the efficacy data from sites with an implausible high placebo response [placebo group Montgomery-Åsberg Depression Rating Scale (MADRS) < = 12] and from sites with no placebo response (MADRS > = 28) are removed, there was a clinically meaningful difference between JNJ-18038683 and placebo. Further clinical studies are required to characterize the potential antidepressant efficacy of JNJ-18038683.

  13. Selective blockade of 5-hydroxytryptamine (5-HT)7 receptors enhances 5-HT transmission, antidepressant-like behavior, and rapid eye movement sleep suppression induced by citalopram in rodents.

    PubMed

    Bonaventure, Pascal; Kelly, Lisa; Aluisio, Leah; Shelton, Jonathan; Lord, Brian; Galici, Ruggero; Miller, Kirsten; Atack, John; Lovenberg, Timothy W; Dugovic, Christine

    2007-05-01

    Evidence has accumulated supporting a role for 5-hydroxytryptamine (5-HT)7 receptors in circadian rhythms, sleep, and mood disorders, presumably as a consequence of the modulation of 5-HT-mediated neuronal activity. We hypothesized that a selective 5-HT7 receptor antagonist, (2R)-1-[(3-hydroxyphenyl)sulfonyl]-2-[2-(4-methyl-1-piperidinyl)ethyl]-pyrrolidine (SB-269970), should increase activity of 5-HT neurons and potentiate the effect of selective serotonin reuptake inhibitors (citalopram). In rats, administration of 3 mg/kg s.c. citalopram alone increased the extracellular concentration of 5-HT. This effect of citalopram on extracellular 5-HT concentration was significantly enhanced by an ineffective dose of SB-269970. Combining this dose of SB-269970 with a low dose of citalopram also resulted in a significant increase in extracellular concentration of 5-HT, suggesting a potentiation of neurochemical effects. In mice, citalopram and SB-269970 dose-dependently decreased immobility time in the tail suspension test. The dose-effect curve of citalopram was shifted leftward by coadministration of an effective dose of SB-269970. Furthermore, combining ineffective doses of citalopram and SB-269970 also resulted in a significant decrease of immobility time in the tail suspension test, suggesting potentiation of antidepressant-like effects. In rats, SB-269970 potentiated the increase of rapid eye movement (REM) latency and the REM sleep decrease induced by citalopram. SB-269970 also reversed the increase in sleep fragmentation induced by citalopram. Rat plasma and brain concentrations of citalopram were not affected by coadministration of SB-269970, arguing for a pharmacodynamic rather than a pharmacokinetic mechanism. Overall, these results indicate that selective blockade of 5-HT7 receptors may enhance the antidepressant efficacy of citalopram and may provide a novel therapy to alleviate sleep disturbances associated with depression.

  14. AMPA receptor involvement in 5-hydroxytryptamine2A receptor-mediated pre-frontal cortical excitatory synaptic currents and DOI-induced head shakes.

    PubMed

    Zhang, Ce; Marek, Gerard J

    2008-01-01

    Glutamate plays an important role in the psychotomimetic effects of both channel blocking N-methyl D-aspartate (NMDA) receptor antagonists and hallucinogenic drugs which activate 5-hydroxytryptamine2A (5-HT2A) receptors. Previous work suggested that activation of non-NMDA ionotropic glutamate receptors mediates the effects of 5-HT-induced excitatory post-synaptic potentials/currents (EPSPs/EPSCs) when recording from layer V pyramidal cells in the rat medial pre-frontal cortex (mPFC). However, those effects are mediated by either alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) or kainate receptors of the iGluk5 subtype. To test whether activation of AMPA receptors is sufficient to mediate 5-HT-induced EPSCs, a 2,3-benzodiazepine that selectively blocks AMPA receptors was assessed. This selective AMPA receptor antagonist potently suppressed 5-HT-induced EPSCs. Since phenethylamine hallucinogens induce head shakes by activating 5-HT2A receptors in the mPFC and this action is modulated by glutamate, we also examined whether selective blockade of AMPA receptors would suppress DOI-induced head shakes. As predicted, we found that selective blockade of AMPA receptors suppressed DOI-induced head shakes. Given evidence that activation of AMPA receptors is an important downstream effect for both channel blocking NMDA receptor antagonists and phenethylamine hallucinogens, we also tested multiple doses of DOI with a sub-anesthetic dose of MK-801. Synergistic action between these two classes of psychotomimetic drugs was demonstrated by MK-801 enhancing DOI-induced head shakes and locomotor activity. These findings expand the dependence of both channel blocking NMDA receptor antagonists and phenethylamine hallucinogens on enhancing extracellular glutamate.

  15. 5-Hydroxytryptamine (serotonin)2A receptors in rat anterior cingulate cortex mediate the discriminative stimulus properties of d-lysergic acid diethylamide.

    PubMed

    Gresch, Paul J; Barrett, Robert J; Sanders-Bush, Elaine; Smith, Randy L

    2007-02-01

    d-Lysergic acid diethylamide (LSD), an indoleamine hallucinogen, produces profound alterations in mood, thought, and perception in humans. The brain site(s) that mediates the effects of LSD is currently unknown. In this study, we combine the drug discrimination paradigm with intracerebral microinjections to investigate the anatomical localization of the discriminative stimulus of LSD in rats. Based on our previous findings, we targeted the anterior cingulate cortex (ACC) to test its involvement in mediating the discriminative stimulus properties of LSD. Rats were trained to discriminate systemically administered LSD (0.085 mg/kg s.c.) from saline. Following acquisition of the discrimination, bilateral cannulae were implanted into the ACC (AP, +1.2 mm; ML, +/-1.0 mm; DV, -2.0 mm relative to bregma). Rats were tested for their ability to discriminate varying doses of locally infused LSD (0.1875, 0.375, and 0.75 microg/side) or artificial cerebrospinal fluid (n = 3-7). LSD locally infused into ACC dose-dependently substituted for systemically administered LSD, with 0.75 microg/side LSD substituting completely (89% correct). Systemic administration of the selective 5-hydroxytryptamine (serotonin) (5-HT)(2A) receptor antagonist R-(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidine-methanol (M100907; 0.4 mg/kg) blocked the discriminative cue of LSD (0.375 microg/side) infused into ACC (from 68 to 16% drug lever responding). Furthermore, M100907 (0.5 microg/microl/side) locally infused into ACC completely blocked the stimulus effects of systemic LSD (0.04 mg/kg; from 80 to 12% on the LSD lever). Taken together, these data indicate that 5-HT(2A) receptors in the ACC are a primary target mediating the discriminative stimulus properties of LSD.

  16. Effects of serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibition plus 5-HT(2A) receptor antagonism on the firing activity of norepinephrine neurons.

    PubMed

    Szabo, Steven T; Blier, Pierre

    2002-09-01

    YM992 [(S)-2-[[(7-fluoro-4-indanyl)oxy]methyl]morpholine monohydrochloride] is a selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitor (SSRI) and a potent 5-HT(2A) antagonist. The aim of the present study was to assess, using in vivo extracellular unitary recordings, the effect of acute and sustained administration of YM992 (40 mg kg(-1) day(-1) s.c., using osmotic minipumps) on the spontaneous firing activity of locus coeruleus (LC) norepinephrine (NE) neurons. Acute intravenous injection of YM992 (4 mg kg(-1)) significantly decreased NE neuron firing activity by 29% and blocked the inhibitory effect of a subsequent injection of the 5-HT(2) agonist DOI [1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride]. A 2-day treatment with YM992 decreased the firing rate of NE neurons by 66%, whereas a partial recovery was observed after a 7-day treatment and a complete one after a 21-day treatment. Following the injection of the alpha(2)-adrenoceptor antagonist idazoxan (1 mg kg(-1) i.v.), NE neuron firing was equalized in controls and 2-day YM992-treated rats. This put into evidence an increased degree of activation of alpha(2)-adrenergic autoreceptors in the treated rats. The suppressant effect of the alpha(2)-adrenoceptor agonist clonidine was significantly decreased in long-term YM992-treated rats. The recovery of LC firing activity after long-term YM992 administration could thus be explained by a decreased sensitivity of alpha(2)-adrenergic autoreceptors. Sustained SSRI administration leads to a gradual reduction of the firing activity of NE neurons during long-term administration, whereas YM992 produced opposite effects. The exact basis for the increased synaptic availability of NE by YM992 remains to be elucidated. This NE activity, resulting from 5-HT reuptake inhibition plus 5-HT(2A) receptor antagonism, might confer additional benefits in affective and anxiety disorders.

  17. Selective Recognition of 5-Hydroxytryptamine and Dopamine on a Multi-Walled Carbon Nanotube-Chitosan Hybrid Film-Modified Microelectrode Array

    PubMed Central

    Xu, Huiren; Wang, Li; Luo, Jinping; Song, Yilin; Liu, Juntao; Zhang, Song; Cai, Xinxia

    2015-01-01

    It is difficult to determine dopamine (DA) and 5-hydroxytryptamine (5-HT) accurately because of the interference of ascorbic acid (AA) in vitro, which has a high concentration and can be oxidized at a potential close to DA and 5-HT at a conventional electrode, combined with the overlapping voltammetric signal of DA and 5-HT at a bare electrode. Herein, chitosan (CS) was used as a stabilizing matrix by electrochemical reaction, and multi-walled carbon nanotubes (MWCNTs) were modified onto the microelectrode array (MEA). The CS-MWCNT hybrid film-modified MEA was quite effective at simultaneously recognizing these species in a mixture and resolved the overlapping anodic peaks of AA, DA and 5-HT into three well-defined oxidation peaks in differential pulse voltammetry (DPV) at −80 mV, 105 mV and 300 mV (versus Ag|AgCl), respectively. The linear responses were obtained in the range of 5 × 10−6 M to 2 × 10−4 M for DA (r = 0.996) and in the range of 1 × 10−5 M to 3 × 10−4 M for 5-HT (r = 0.999) using the DPV under the presence of a single substance. While DA coexisted with 5-HT in the interference of 3 × 10−4 M AA, the linear responses were obtained in the range of 1 × 10−5 M to 3 × 10−4 M for selective molecular recognition of DA (r = 0.997) and 5-HT (r = 0.997) using the DPV. Therefore, this proposed MEA was successfully used for selective molecular recognition and determination of DA and 5-HT using the DPV, which has a potential application for real-time determination in vitro experiments. PMID:25580900

  18. [Effects of Chinese herbal medicines for regulating liver qi on expression of 5-hydroxytryptamine 3B receptor in hypothalamic tissues of rats with anger emotion].

    PubMed

    Ge, Qing-fang; Zhang, Hui-yun

    2011-08-01

    To explore the central mechanisms of anger emotion and the effects of Chinese herbal medicines for regulating liver qi on the anger emotion and the expression level of 5-hydroxytryptamine 3B receptor (5-HT3BR) in rat hypothalamus. Rat models of anger-in or anger-out emotions were prepared by the methods of resident intruder paradigm. There were five groups in this study: control, anger-in model, Jingqianshu Granule-treated anger-in, anger-out model and Jingqianping Granule-treated anger-out groups. The treatment groups were orally given Jingqianshu granules and Jingqianping granules respectively, and the model groups and the normal control group were given sterile water. Open-field test and sucrose preference test were used to evaluate behavioristics of the rats. Semi-quantitative reverse transcription-polymerase chain reaction and Western blot methods were used to detect the expression levels of 5-HT3BR mRNA and protein in the rat hypothalamus. The expression of 5-HT3BR in hypothalamus of anger-in model rats increased obviously (P<0.01) and that of anger-out model rats decreased obviously (P<0.01) compared with the normal control group. Compared with the model group, the expressions of 5-HT3BR in the treatment groups were significantly improved (P<0.01) after treatment, and recovered to normal level. The anger-in stimulation obviously increases hypothalamic 5-HT3BR expression and the anger-out emotion can obviously reduce its expression. Chinese herbal medicines for regulating liver qi may treat anger emotion in rats by improving the hypothalamic 5-HT3BR protein and gene expression levels.

  19. Protein kinase mediated upregulation of endothelin A, endothelin B and 5-hydroxytryptamine 1B/1D receptors during organ culture in rat basilar artery

    PubMed Central

    Hansen-Schwartz, Jacob; Svensson, Carl-Lennart; Xu, Cang-Bao; Edvinsson, Lars

    2002-01-01

    Organ culture has been shown to upregulate both endothelin (ET) and 5-hydroxytryptamine 1B/1D (5-HT1B/1D) receptors in rat cerebral arteries. The purpose of the present study was to investigate the involvement of protein kinases, especially protein kinases C (PKC) and A (PKA) in this process. The effect of inhibiting protein kinases during organ culture with staurosporine (unspecific protein kinase inhitor), RO 31-7549 (specific inhibitor of classical PKC's) and H 89 (specific inhibitor of PKA) was examined using in vitro pharmacological examination of cultured vessel segments with ET-1 (unspecific ETA and ETB agonist), S6c (specific ETB agonist) and 5-CT (5-HT1 agonist). Levels of mRNA coding for the ETA, ETB, 5-HT1B and 5-HT1D receptors were analysed using real-time RT–PCR. Classical PKC's are critically involved in the appearance of the ETB receptor; co-culture with RO 31-7549 abolished the contractile response (6.9±1.8%) and reduced the ETB receptor mRNA by 44±4% as compared to the cultured control. Correlation between decreased ETB receptor mRNA and abolished contractile function indicates upstream involvement of PKC. Inhibition of PKA generally had an enhancing effect on the induced changes giving rise to a 7–25% increase in Emax in response to ET-1, S6c and 5-CT as compared to the cultured control. Staurosporine inhibited the culture induced upregulation of the response of both the ETA and the 5-HT1B/1D receptors, but had no significant effect on the mRNA levels of these receptors. This lack of correlation indicates an additional downstream involvement of protein kinases. PMID:12183337

  20. Sucrose preload reduces snacking after mild mental stress in healthy participants as a function of 5-hydroxytryptamine transporter gene promoter polymorphism.

    PubMed

    Markus, C Rob; Jonkman, Lisa M; Capello, Aimee; Leinders, Sacha; Hüsch, Fabian

    2015-01-01

    Brain serotonin (5-hydroxytryptamine, 5-HT) dysfunction is considered to promote food intake and eating-related disturbances, especially under stress or negative mood. Vulnerability for 5-HT disturbances is considered to be genetically determined, including a short (S) allele polymorphism in the serotonin transporter gene (5-HTTLPR) that is associated with lower serotonin function. Since 5-HT function may be slightly increased by carbohydrate consumption, S-allele 5-HTTLPR carriers in particular may benefit from a sugar-preload due to their enhanced 5-HT vulnerability. The aim of the current study was to investigate whether a sugar-containing preload may reduce appetite and energy intake after exposure to stress to induce negative mood, depending on genetic 5-HT vulnerability. From a population of 771 healthy young male and female genotyped college students 31 S/S carriers (8 males, 23 females) and 26 long allele (L/L) carriers (9 males, 17 females) (mean ± S.D. 22 ± 1.6 years; body mass index, BMI, 18-33 kg/m(2)) were monitored for changes in appetite and snacking behavior after stress exposure. Results revealed an increased energy intake after mild mental stress (negative mood) mainly for high-fat sweet foods, which was significantly greater in S/S carriers, and only in these genotypes this intake was significantly reduced by a sucrose-containing preload. Although alternative explanations are possible, it is suggested that S/S participants may have enhanced brain (hypothalamic) 5-HT responsiveness to food that makes them more susceptible to the beneficial satiation effects of a sucrose-preload as well as to the negative effects of mild mental stress on weight gain.

  1. Selective recognition of 5-hydroxytryptamine and dopamine on a multi-walled carbon nanotube-chitosan hybrid film-modified microelectrode array.

    PubMed

    Xu, Huiren; Wang, Li; Luo, Jinping; Song, Yilin; Liu, Juntao; Zhang, Song; Cai, Xinxia

    2015-01-08

    It is difficult to determine dopamine (DA) and 5-hydroxytryptamine (5-HT) accurately because of the interference of ascorbic acid (AA) in vitro, which has a high concentration and can be oxidized at a potential close to DA and 5-HT at a conventional electrode, combined with the overlapping voltammetric signal of DA and 5-HT at a bare electrode. Herein, chitosan (CS) was used as a stabilizing matrix by electrochemical reaction, and multi-walled carbon nanotubes (MWCNTs) were modified onto the microelectrode array (MEA). The CS-MWCNT hybrid film-modified MEA was quite effective at simultaneously recognizing these species in a mixture and resolved the overlapping anodic peaks of AA, DA and 5-HT into three well-defined oxidation peaks in differential pulse voltammetry (DPV) at -80 mV, 105 mV and 300 mV (versus Ag|AgCl), respectively. The linear responses were obtained in the range of 5 × 10(-6) M to 2 × 10(-4) M for DA (r = 0.996) and in the range of 1 × 10(-5) M to 3 × 10(-4) M for 5-HT (r = 0.999) using the DPV under the presence of a single substance. While DA coexisted with 5-HT in the interference of 3 × 10(-4) M AA, the linear responses were obtained in the range of 1 × 10(-5) M to 3 × 10(-4) M for selective molecular recognition of DA (r = 0.997) and 5-HT (r = 0.997) using the DPV. Therefore, this proposed MEA was successfully used for selective molecular recognition and determination of DA and 5-HT using the DPV, which has a potential application for real-time determination in vitro experiments.

  2. The 5-hydroxytryptamine4 receptor agonists prucalopride and PRX-03140 increase acetylcholine and histamine levels in the rat prefrontal cortex and the power of stimulated hippocampal θ oscillations.

    PubMed

    Johnson, David E; Drummond, Elena; Grimwood, Sarah; Sawant-Basak, Aarti; Miller, Emily; Tseng, Elaine; McDowell, Laura L; Vanase-Frawley, Michelle A; Fisher, Katherine E; Rubitski, David M; Stutzman-Engwall, Kim J; Nelson, Robin T; Horner, Weldon E; Gorczyca, Roxanne R; Hajos, Mihaly; Siok, Chester J

    2012-06-01

    5-Hydroxytryptamine (5-HT)(4) receptor agonists reportedly stimulate brain acetylcholine (ACh) release, a property that might provide a new pharmacological approach for treating cognitive deficits associated with Alzheimer's disease. The purpose of this study was to compare the binding affinities, functional activities, and effects on neuropharmacological responses associated with cognition of two highly selective 5-HT(4) receptor agonists, prucalopride and 6,7-dihydro-4-hydroxy-7-isopropyl-6-oxo-N-[3-(piperidin-1-yl)propyl]thieno[2,3-b]pyridine-5-carboxamide (PRX-03140). In vitro, prucalopride and PRX-03140 bound to native rat brain 5-HT(4) receptors with K(i) values of 30 nM and 110 nM, respectively, and increased cAMP production in human embryonic kidney-293 cells expressing recombinant rat 5-HT(4) receptors. In vivo receptor occupancy studies established that prucalopride and PRX-03140 were able to penetrate the brain and bound to 5-HT(4) receptors in rat brain, achieving 50% receptor occupancy at free brain exposures of 330 nM and 130 nM, respectively. Rat microdialysis studies revealed that prucalopride maximally increased ACh and histamine levels in the prefrontal cortex at 5 and 10 mg/kg, whereas PRX-03140 significantly increased cortical histamine levels at 50 mg/kg, failing to affect ACh release at doses lower than 150 mg/kg. In combination studies, donepezil-induced increases in cortical ACh levels were potentiated by prucalopride and PRX-03140. Electrophysiological studies in rats demonstrated that both compounds increased the power of brainstem-stimulated hippocampal θ oscillations at 5.6 mg/kg. These findings show for the first time that the 5-HT(4) receptor agonists prucalopride and PRX-03140 can increase cortical ACh and histamine levels, augment donepezil-induced ACh increases, and increase stimulated-hippocampal θ power, all neuropharmacological parameters consistent with potential positive effects on cognitive processes.

  3. Characterization of the 5-hydroxytryptamine1a receptor-mediated inhibition of forskolin-stimulated adenylate cyclase activity in guinea pig and rat hippocampal membranes.

    PubMed

    De Vivo, M; Maayani, S

    1986-07-01

    The inhibition of forskolin-stimulated adenylate cyclase activity by 5-hydroxytryptamine (5-HT) receptor agonists was measured in guinea pig and rat hippocampal membranes. The results were consistent with the inhibition being mediated by a single, homogeneous population of receptors. In guinea pig hippocampal membranes 8-hydroxy-2-(di-n-propylamino)tetralin, d-lysergic acid diethylamide, 5-HT and buspirone were potent in inhibiting forskolin-stimulated adenylate cyclase activity, with EC50 values of 18, 24, 53 and 146 nM, respectively. Spiperone (Kb = 26 nM) and methiothepin (Kb = 13 nM) were potent competitive antagonists at this receptor whereas ketanserin, a high affinity 5-HT2 receptor ligand, and ICS 205-930, a high affinity peripheral neuronal (M) receptor ligand, were not. In rat hippocampal membranes, 8-hydroxy-2-(di-n-propylamino)tetralin, d-lysergic acid diethylamide, 5-HT and buspirone were potent agonists and exhibited the same rank order of potency as in guinea pig hippocampal membranes. The maximal percentage of inhibition by buspirone was significantly less than the maximal percentage of inhibition by 5-HT in rat membranes, suggesting that it is a partial agonist at this receptor, with an intrinsic activity relative to 5-HT of 0.5. The concentration-response data show that the inhibition of forskolin-stimulated adenylate cyclase activity in guinea pig and rat hippocampal membranes is mediated by a receptor with the characteristics of the 5-HT1A binding site. We propose that the inhibition of adenylate cyclase activity is a functional correlate of this binding site. This response is suitable for measuring activities and affinities of drugs acting at 5-HT1A receptors.

  4. A comparison of 5-hydroxytryptamine receptors mediating contraction in rabbit aorta and dog saphenous vein: evidence for different receptor types obtained by use of selective agonists and antagonists.

    PubMed Central

    Feniuk, W.; Humphrey, P. P.; Perren, M. J.; Watts, A. D.

    1985-01-01

    Using recently available selective agonists and antagonists we have examined further our postulate (Apperley et al., 1980) that 5-hydroxytryptamine (5-HT) mediates contraction of dog saphenous vein via a different 5-HT receptor type from that in the rabbit aorta. In the rabbit isolated aorta, ketanserin and spiperone were potent, specific, competitively-acting antagonists of the contractile effects of 5-HT. In contrast, in the dog isolated saphenous vein neither ketanserin nor spiperone caused any rightward displacement of concentration-response curves to 5-HT although the maximum response was reduced by about 10%. In the rabbit aorta 5-carboxamidotryptamine (5-CONH2-T) was a weak agonist whilst the 5-N,N-dimethyl and 5-N-ethyl derivatives were even weaker or inactive. The contractile effect of 5-CONH2-T in the rabbit aorta was potently and competitively antagonized by ketanserin. In contrast, in the dog saphenous vein 5-CONH2-T and its 5-N,N-dimethyl and 5-N-ethyl derivatives were all potent agonists. The contractile effect of 5-CONH2-T was not markedly affected by ketanserin. The profile of action of ketanserin and spiperone in the rabbit aorta is consistent with the view that 5-HT2 receptors mediate contraction in this preparation. However, the 5-HT receptor mediating contraction in the dog saphenous vein appears to be '5-HT1-like', sharing a number of characteristics with the 5-HT1 recognition site identified from [3H]-5-HT ligand binding studies in brain tissue. PMID:2933110

  5. Brown adipose tissue sympathetic nerve activity is potentiated by activation of 5-hydroxytryptamine (5-HT)1A/5-HT7 receptors in the rat spinal cord

    PubMed Central

    Madden, C. J.; Morrison, S. F.

    2008-01-01

    In urethane-chloralose anesthetized, neuromuscularly blocked, ventilated rats, microinjection of NMDA (12 pmol) into the right fourth thoracic segment (T4) spinal intermediolateral nucleus (IML) immediately increased ipsilateral brown adipose tissue (BAT) sympathetic nerve activity (SNA; peak +492% of control), expired CO2 (+0.1%) heart rate (+48 beats min−1) and arterial pressure (+8 mmHg). The increase in BAT SNA evoked by T4 IML microinjection of NMDA was potentiated when it was administered immediately following a T4 IML microinjection of 5-hydroxytryptamine (5-HT, 100 pmol) or the 5-HT1A/5-HT7 receptor agonist, 8-OH-DPAT (600 pmol), (area under the curve: 184%, and 259% of the NMDA-only response, respectively). In contrast, T4 IML microinjection of the 5-HT2 receptor agonist, DOI (28 pmol) did not potentiate the NMDA-evoked increase in BAT SNA (101% of NMDA-only response). Microinjection into the T4 IML of the selective 5-HT1A antagonist, WAY-100635 (500 pmol), plus the 5-HT7 antagonist, SB-269970 (500 pmol), prevented the 5-HT-induced potentiation of the NMDA-evoked increase in BAT SNA. When administered separately, WAY-100635 (800 pmol) and SB-269970 (800 pmol) attenuated the 8-OH-DPAT-induced potentiation of the NMDA-evoked increase in BAT SNA through effects on the amplitude and duration of the response, respectively. The selective 5-HT2 receptor antagonist, ketanserin (100 pmol), did not attenuate the potentiations of the NMDA-evoked increase in BAT SNA induced by either 5-HT or 8-OH-DPAT. These results demonstrate that activation of 5-HT1A/5-HT7 receptors can act synergistically with NMDA receptor activation within the IML to markedly increase BAT SNA. PMID:18082230

  6. The effect of intraventricular injections of noradrenaline, 5-hydroxytryptamine, acetylcholine and tranylcypromine on the ox (Bos taurus) at different environmental temperatures

    PubMed Central

    Findlay, J. D.; Thompson, G. E.

    1968-01-01

    1. Noradrenaline, 5-hydroxytryptamine (5-HT), acetylcholine and tranylcypromine were injected or infused into the lateral ventricle of the ox. The effects of these drugs on heart and respiration rates, heat production, rectal, skin and hypothalamic temperatures and skin evaporative loss were measured when the animal was exposed to environmental temperatures ranging from -1° C to +30° C. 2. Acetylcholine (0·001-2 mg) had no detectable effect on temperature regulation at 20° C. 3. In small doses (0·005-0·05 mg) 5-HT had no detectable effect. Larger doses (2-5 mg) given in a cold environment (-1° C) also had no effect but the same doses given in warm environments (15-30° C) caused increases in skin temperatures, skin evaporative loss and respiratory rate, and decreases in rectal and hypothalamic temperatures. 4. Infusion of tranylcypromine (0·107 ml./min of a 1 in 50 solution) in a warm environment (20° C) also caused a decrease in rectal temperature after a delay of 1-1½ hr during which no effects were apparent. 5. Noradrenaline (2 mg) had no effect on temperature regulation when injected into animals in a warm environment (30° C). When injected (1 mg) into animals in a cold environment (-1° C) shivering stopped and heat production and rectal and hypothalamic temperatures were decreased. 6. It is concluded that intraventricular 5-HT and noradrenaline both cause a decrease in body temperature, and it is unlikely that central temperature regulation in the ox is mediated only by these two substances. PMID:5636999

  7. PRX-08066, a novel 5-hydroxytryptamine receptor 2B antagonist, reduces monocrotaline-induced pulmonary arterial hypertension and right ventricular hypertrophy in rats.

    PubMed

    Porvasnik, Stacy L; Germain, Sean; Embury, Jennifer; Gannon, Kimberley S; Jacques, Vincent; Murray, Justin; Byrne, Barry J; Shacham, Sharon; Al-Mousily, Faris

    2010-08-01

    Pulmonary arterial hypertension (PAH) is a life-threatening disease that results in right ventricular failure. 5-((4-(6-Chlorothieno[2,3-d]pyrimidin-4-ylamino)piperidin-1-yl)methyl)-2-fluorobenzonitrile monofumarate (PRX-08066) is a selective 5-hydroxytryptamine receptor 2B (5-HT2BR) antagonist that causes selective vasodilation of pulmonary arteries. In the current study, the effects of PRX-08066 were assessed by using the monocrotaline (MCT)-induced PAH rat model. Male rats received 40 mg/kg MCT or phosphate-buffered saline and were treated orally twice a day with vehicle or 50 or 100 mg/kg PRX-08066 for 5 weeks. Pulmonary and cardiac functions were evaluated by hemodynamics, heart weight, magnetic resonance imaging (MRI), pulmonary artery (PA) morphology, and histology. Cardiac MRI demonstrated that PRX-08066 (100 mg/kg) significantly (P < 0.05) improved right ventricular ejection fraction. PRX-08066 significantly reduced peak PA pressure at 50 and 100 mg/kg (P < 0.05 and < 0.01, respectively) compared with MCT control animals. PRX-08066 therapy also significantly reduced right ventricle (RV)/body weight and RV/left ventricle + septum (P < 0.01 and < 0.001, respectively) compared with MCT-treated animals. Morphometric assessment of pulmonary arterioles revealed a significant reduction in medial wall thickening and lumen occlusion associated with both doses of PRX-08066 (P < 0.01). The 5-HT2BR antagonist PRX-08066 significantly attenuated the elevation in PA pressure and RV hypertrophy and maintained cardiac function. Pulmonary vascular remodeling was also diminished compared with MCT control rats. PRX-08066 prevents the severity of PAH in the MCT rat model.

  8. Isolation-induced aggression in mice: effects of 5-hydroxytryptamine uptake inhibitors and involvement of postsynaptic 5-HT1A receptors.

    PubMed

    Sánchez, C; Hyttel, J

    1994-11-03

    The inhibitory potencies of selective serotonin (5-hydroxytryptamine, 5-HT) uptake inhibitors on isolation-induced aggressive behaviour in male mice were studied. Furthermore, the role of postsynaptic 5-HT1A receptors in the mediation of aggressive behaviour was studied. The selective 5-HT uptake inhibitors, sertraline, floxetine, femoxetine and fluvoxamine, showed weak antiaggressive effects, and citalopram and paroxetine were ineffective. This rank of potencies corresponded with neither uptake inhibitory potencies in vitro nor potentiation of 1-5-hydroxytryptophan (1,5-HTP)-induced motor effects in vivo, as citalopram and paroxetine were among the most potent compounds in these tests. A subeffective dose of 1,5-HTP (110 mumol/kg = 25 mg/kg, s.c.) potentiated the antiaggressive effect of citalopram and paroxetine more than 110 and 1600 times, respectively. The effects of sertraline, fluvoxamine, fluoxetine and femoxetine were only potentiated 3, 36, 4 and 16 times, respectively. The 5-HT releasing compound fenfluramine inhibited the aggressive behaviour dose dependently, and depletion of 5-HT by treatment with p-chloro-phenylalanine methyl ester attenuated this effect significantly. p-Chloro-phenylalanine methyl ester was ineffective itself, but potentiated the antiaggressive effect of the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamin)tetralin (8-OH-DPAT). The beta-adrenoceptor/5-HT1A receptor antagonist, (-)-penbutolol, reversed the antiaggressive effects of 8-OHDPAT. In conclusion, selective 5-HT uptake inhibitors act in different ways on isolation-induced aggressive behaviour, and postsynaptic 5-HT1A receptors are involved in mediating the aggressive behaviour.

  9. 5-hydroxytryptamine-mediated neurotransmission modulates spontaneous and vagal-evoked glutamate release in the nucleus of the solitary tract effect of uptake blockade.

    PubMed

    Hosford, Patrick S; Mifflin, Steve W; Ramage, Andrew G

    2014-05-01

    The effect of blockade of either 5-hydroxytryptamine (5-HT)/serotonin transporter (SERT) with citalopram or the organic cation transporter 3 (OCT3)/plasma membrane monoamine transporter (PMAT) with decynium-22 (D-22) on spontaneous and evoked release of 5-HT in the nucleus tractus solitarius (NTS) was investigated in rat brainstem slices treated with gabazine. 5-HT release was measured indirectly by changes in the frequency and amplitude of glutamatergic miniature excitatory postsynaptic currents (mEPSCs) [in the presence of tetrodotoxin (TTX)] and evoked EPSCs. Blockade of 5-HT3 receptors with granisetron reduced, whereas the 5-HT3 agonist phenylbiguanide increased, the frequency of mEPSCs. 5-HT decreased mEPSC frequency at low concentrations and increased frequency at high concentrations. This inhibition was blocked by the 5-HT1A antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY-100635), which was ineffective on its own, whereas the excitation was reversed by granisetron. The addition of citalopram or D-22 caused inhibition, which was prevented by 5-HT1A blockade. Thus, in the NTS, the spontaneous release of 5-HT is able to activate 5-HT3 receptors, but not 5-HT1A receptors, as the release in their vicinity is removed by uptake. The ineffectiveness of corticosterone suggests that the low-affinity, high-capacity transporter is PMAT, not OCT3. For evoked 5-HT release, only D-22 caused an increase in the amplitude of EPSCs, with a decrease in the paired pulse ratio, and increased the number of spontaneous EPSCs after 20-Hz stimulation. Thus, for the evoked release of 5-HT, the low-affinity, high-capacity transporter PMAT, but not 5-HT transporter (5-HTT)/SERT, is important in the regulation of changes in 5-HT extracellular concentration.

  10. Pharmacological characterization of 5-hydroxytryptamine3 receptors in murine brain and ileum using the novel radioligand [3H]RS-42358-197: evidence for receptor heterogeneity.

    PubMed

    Bonhaus, D W; Wong, E H; Stefanich, E; Kunysz, E A; Eglen, R M

    1993-11-01

    Previous studies have demonstrated species-specific differences in 5-hydroxytryptamine3 (5-HT3) receptors, but unequivocal evidence of 5-HT3 receptor subtypes, within a species, has not yet been obtained. The purpose of the current study was to test for heterogeneity in 5-HT3 receptors in murine tissues. 5-HT3 receptors in membranes derived from brain cerebral cortex of CD-1, C57Bl/6, and Swiss Webster mice and ileum of CD-1 mice were labeled with the 5-HT3 receptor antagonist [3H]RS-42358-197. Structurally diverse competing ligands were then used to characterize the binding site. [3H]RS-42358-197 bound with similar affinity in each of the cortical tissues (mean KD = 0.14 nM; range, 0.06-0.32 nM) but bound with lower affinity in ileal tissue (2.5 nM). The density of sites labeled with [3H]RS-42358-197 ranged from 10.4 fmol/mg of protein in Swiss Webster mouse cortex to 44.2 fmol/mg of protein in Sprague-Dawley rat cortex. Displacing ligands produced a pharmacologic profile of the [3H]RS-42358-197 binding site consistent with it being a 5-HT3 receptor: (R)-YM060 > (S)-zacopride > (R)-zacopride > MDL 72222 > 2-methyl-5-HT. However, > or = 10-fold differences in the affinity of certain ligands were found when comparing 5-HT3 binding sites in membranes from cerebral cortex of the different strains of mice and when comparing 5-HT3 binding sites in brain and ileal membranes prepared from the CD-1 mouse strain.(ABSTRACT TRUNCATED AT 250 WORDS)

  11. Imaging Glaucomatous Damage Across the Temporal Raphe

    PubMed Central

    Huang, Gang; Luo, Ting; Gast, Thomas J.; Burns, Stephen A.; Malinovsky, Victor E.; Swanson, William H.

    2015-01-01

    Purpose. To image and analyze anatomical differences at the temporal raphe between normal and glaucomatous eyes using adaptive optics scanning laser ophthalmoscopy (AOSLO) and optical coherence tomography (OCT), and to relate these differences to visual field measurements. Methods. Nine glaucomatous eyes of 9 patients (age 54–78 years, mean deviation of visual field [MD] −5.03 to −0.20 dB) and 10 normal eyes of 10 controls (age 54–81, MD −1.13 to +1.39 dB) were enrolled. All the participants were imaged in a region that was centered approximately 9° temporal to the fovea. The size of imaging region was at least 10° vertically by 4° horizontally. The raphe gap, defined as the distance between the superior and inferior retinal nerve fiber layer (RNFL) bundles, was measured. A bundle index was computed to quantify the relative reflectivity and density of the nerve fiber bundles. We also measured thickness of the ganglion cell complex (GCC) and RNFL. Results. The raphe gap was larger in glaucomatous eyes than control eyes. Specifically, eight glaucomatous eyes with local averaged field loss no worse than −3.5 dB had larger raphe gaps than all control eyes. The bundle index, GCC thickness, and RNFL thickness were on average reduced in glaucomatous eyes, with the first two showing statistically significant differences between the two groups. Conclusions. Structural changes in the temporal raphe were observed and quantified even when local functional loss was mild. These techniques open the possibility of using the raphe as a site for glaucoma research and clinical assessment. PMID:26047040

  12. The 5-hydroxytryptamine2A receptor is involved in (+)-norfenfluramine-induced arterial contraction and blood pressure increase in deoxycorticosterone acetate-salt hypertension.

    PubMed

    Ni, Wei; Fink, Gregory D; Watts, Stephanie W

    2007-05-01

    The highly effective anorexigen (+)-fenfluramine was widely used to control body weight until the association with primary pulmonary hypertension and valvular heart disease. (+)-Norfenfluramine is the major hepatic metabolite of (+)-fenfluramine and is primarily responsible for the anorexic effect as well as side effects. We reported that (+)-norfenfluramine causes vasoconstriction and a blood pressure increase in rats with normal blood pressure via the 5-hydroxytryptamine (5-HT)2A receptor. With the knowledge that (+)-norfenfluramine also has affinity for 5-HT2B receptors and that arterial 5-HT2B receptor expression is up-regulated in deoxycorticosterone acetate (DOCA)-salt hypertension, we tested the hypothesis that (+)-norfenfluramine-induced vasoconstriction and pressor effects are potentiated in DOCA-salt hypertensive rats in a 5-HT2 receptor-dependent manner. Contractions of arteries were measured using an isolated tissue bath system or myograph. Mean arterial blood pressure was measured in chronically instrumented conscious rats. Effects of (+)-norfenfluramine in stimulating arterial contraction (leftward shift versus SHAM, aorta, 5.13-fold; renal artery, 1.95-fold; mesenteric resistance artery, 1.77-fold) and raising blood pressure were significantly enhanced in hypertension. In arteries from both normotensive and hypertensive rats, (+)-norfenfluramine-induced contraction in aorta was inhibited by 5-HT2A receptor antagonists, ketanserin and LY53857 (4-isopropyl-7-methyl-9-(2-hydroxy-1-meth ylpropoxycarbonyl)4,6,6a,7,8,9,10,10a-octahydroindolo[4,3-fg]quinoline), but not by the 5-HT2B receptor antagonist, LY272015 [6-chloro-5-methyl-N-(5-quinolinyl)-2,3-dihydro-1H-indole-1-carboxamide]. Ketanserin (3 mg/kg) reduced (+)-norfenfluramine-induced pressor response in both SHAM and DOCA rats. Our results demonstrate that (+)-norfenfluramine-induced arterial contraction and blood pressure increases are potentiated in DOCA-salt hypertensive rats. However, it is the 5

  13. Polymorphisms in the 5-hydroxytryptamine 2A receptor and CytochromeP4502D6 genes synergistically predict fluvoxamine-induced side effects in japanese depressed patients.

    PubMed

    Suzuki, Yutaro; Sawamura, Kazushi; Someya, Toshiyuki

    2006-04-01

    5-Hydroxytryptamine (5-HT) receptors are thought to be associated with the gastrointestinal side effects induced by selective serotonin reuptake inhibitors. CytochromeP450 (CYP) 2D6 may also be associated with the side effects induced by fluvoxamine, since the plasma fluvoxamine concentration depends on a CYP2D6 gene polymorphism. This study investigated whether 5-HT receptor and CYP2D6 gene polymorphisms could predict the occurrence of the side effects. The effects of 5-HT receptor and CYP2D6 gene polymorphisms on the incidence of gastrointestinal side effects induced by fluvoxamine were investigated in 100 depressed outpatients who gave written consent to participate in the study. The patients visited every 2 weeks until the week 12 end point and the fluvoxamine dose was changed in response to their clinical symptoms. All side effects, including the gastrointestinal side effects, were assessed at each visit. Polymerase chain reaction was used to determine A-1438G of the 5-HT2A receptor, C195T and Pro16Ser of the 5-HT3A receptor, Tyr129Ser of the 5-HT3B receptor, and the *5 and *10 alleles of CYP2D6. Both the A-1438G polymorphism of the 5-HT2A receptor gene and the CYP2D6 gene polymorphism had significant effects on the incidence of gastrointestinal side effects. Cox regression was used to analyze the combination effect of the two polymorphisms on the gastrointestinal side effects. Cox regression analysis showed that lower metabolizers (LMs) of CYP2D6 with the G/G genotype of the 5-HT2A A-1438G polymorphism had a 4.242-fold (P = 0.009) and LMs with the A/G genotype had a 4.147-fold (P = 0.004) higher risk of developing gastrointestinal side effects than normal metabolizers with the A/A genotype. The 5-HT3A and 3B gene polymorphisms had no significant effects on the incidence of gastrointestinal side effects. 5-HT2A receptor and CYP2D6 gene polymorphisms had a synergistic effect for the prediction of fluvoxamine-induced gastrointestinal side effects.

  14. 5-Hydroxytryptamine type 2A receptors regulate cyclic AMP accumulation in a neuronal cell line by protein kinase C-dependent and calcium/calmodulin-dependent mechanisms.

    PubMed

    Berg, K A; Clarke, W P; Chen, Y; Ebersole, B J; McKay, R D; Maayani, S

    1994-05-01

    The effects of 5-hydroxytryptamine (5-HT)2A receptor activation on cAMP formation were studied in a cell line derived from embryonic rat cortex (A1A1). 5-HT (EC50 = 0.87 microM) amplified the amount of cAMP formed in response to 5'-N-ethylcarboxamidoadenosine (an adenosine A2 receptor agonist), cholera toxin, and forskolin after 15 min of coincubation in the presence of the phosphodiesterase inhibitor rolipram. This effect of 5-HT was blocked by 10 nM ketanserin as well as by 10 nM spiperone, indicating a response mediated by the 5-HT2A receptor subtype. Similarly, cAMP accumulation was enhanced by coincubation with the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) and the calcium ionophore A23187. After exposure to PMA for 24 hr (PKC-depleted cells), 5-HT and A23187 still enhanced cAMP formed in response to forskolin and 5'-N-ethylcarboxamidoadenosine, whereas the amplifying effects of PMA were abolished. Analysis by Western blots and PKC activity measurements revealed that, of three PKC isoforms detected in A1A1 cells (alpha, delta, and epsilon), only the calcium-independent isoform PKC-epsilon remained in membrane fractions after long term PMA treatment. In PKC-depleted cells, 5-HT-mediated amplification was greatly reduced after treatment with the calcium chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (acetoxymethyl)-ester or the calmodulin antagonists calmidazolium and N-(6-aminohexyl)-5-chloro-1-napthalenesulfonamide hydrochloride. In addition, 5-HT-mediated amplification of cAMP accumulation was reduced by the PKC inhibitor staurosporine in normal cells but was unaffected in PKC-depleted cells. In conclusion, these data suggest that 5-HT2A receptor activation can amplify cAMP formation in A1A1 cells by two distinct pathways coupled to the hydrolysis of inositol phosphates, i.e., PKC and calcium/calmodulin.

  15. A behavioural and biochemical study in rats of 5-hydroxytryptamine receptor agonists and antagonists, with observations on structure-activity requirements for the agonists

    PubMed Central

    Green, A.R.; Hall, J.E.; Rees, A.R.

    1981-01-01

    1 The effect of the putative 5-hydroxytryptamine (5-HT) receptor antagonists, methysergide, methergoline, mianserin, cyproheptadine, cinanserin (all at 10 mg/kg), methiothepin (5 mg/kg) and (-)-propranolol (20 mg/kg) on the behavioural responses to tranylcypromine (10 mg/kg) followed 30 min later by L-tryptophan (100 mg/kg) was examined. 2 Methysergide, methergoline, methiothepin and (-)-propranolol inhibited head weaving, forepaw treading and hind-limb abduction. Methysergide and methergoline increased reactivity. In contrast, cypropheptadine, cinanserin and mianserin had no effects on the behaviour. 3 Similar findings were obtained when the behaviours were elicited by administration of tranylcypromine (10 mg/kg) followed by the putative 5-HT receptor agonist, 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) (2 mg/kg). 4 When the behaviours were elicited by the putative 5-HT receptor agonist, quipazine (50 mg/kg), all the drugs effectively inhibited head weaving and forepaw treading. 5 When the dose of cypropheptadine was doubled to 20 mg/kg an inhibition of the tranylcypromine/L-tryptophan induced behaviours was seen. 6 Methiothepin produced a marked inhibition of apomorphine-induced locomotor activity whilst all the others enhanced this response, suggesting that only methiothepin inhibits the 5-HT behaviours by dopamine antagonism and that the increased reactivity seen following tranylcypromine/L-tryptophan after pretreatment with methysergide or methergoline might be due to enhanced dopamine function. 7 Pretreatment with p-chlorophenylalanine resulted in enhanced behavioural responses to both 5-MeODMT and quipazine. 8 Both methergoline and methiothepin decreased the rate of 5-HT synthesis in whole brain but not spinal cord and methergoline decreased spinal cord 5-HIAA concentration. None of the other drugs had any significant effects on the concentration of 5-HT, 5-HIAA or 5-HT synthesis rate in brain or spinal cord. 9 Experiments with compounds structurally related

  16. Inhibitory action of niflumic acid on noradrenaline- and 5-hydroxytryptamine-induced pressor responses in the isolated mesenteric vascular bed of the rat.

    PubMed

    Criddle, D N; de Moura, R S; Greenwood, I A; Large, W A

    1997-03-01

    1. The effects of niflumic acid, an inhibitor of calcium-activated chloride currents, were compared with the actions of the calcium channel blocker nifedipine on noradrenaline- and 5-hydroxytryptamine (5-HT)-induced pressor responses of the rat perfused isolated mesenteric vascular bed. 2. Bolus injections of noradrenaline (1 and 10 nmol) increased the perfusion pressure in a dose-dependent manner. Nifedipine (1 microM) inhibited the increase in pressure produced by 1 nmol noradrenaline by 31 +/- 5%. Niflumic acid (10 and 30 microM) also inhibited the noradrenaline-induced increase in perfusion pressure and 30 microM niflumic acid reduced the pressor response to 1 nmol noradrenaline by 34 +/- 6%. 3. The increases in perfusion elicited by 5-HT (0.3 and 3 nmol) were reduced by niflumic acid (10 and 30 microM) in a concentration-dependent manner and 30 microM niflumic acid inhibited responses to 0.3 and 3 nmol 5-HT by, respectively, 49 +/- 8% and 50 +/- 7%. Nifedipine (1 microM) decreased the pressor response to 3 nmol 5-HT by 44 +/- 9%. 4. In the presence of a combination of 30 microM niflumic acid and 1 microM nifedipine the inhibition of the pressor effects of noradrenaline (10 nmol) and 5-HT (3 nmol) was not significantly greater than with niflumic acid (30 microM) alone. Thus the effects of niflumic acid and nifedipine were not additive. 5. In Ca-free conditions the transient contractions induced by 5-HT (3 nmol) were not reduced by 30 microM niflumic acid, suggesting that this agent does not inhibit calcium release from the intracellular store or the binding of 5-HT to its receptor. 6. Niflumic acid 30 microM did not inhibit the pressor responses induced by KCl (20 and 60 mumol) which were markedly reduced by 1 microM nifedipine. In addition, 1 microM levcromakalim decreased pressor responses produced by 20 mumol KCl. These data suggest that niflumic acid does not block directly calcium channels or activate potassium channels. 7. It is concluded that niflumic

  17. Influence of ambient temperature on the thermoregulatory responses to 5-hydroxytryptamine, noradrenaline and acetylcholine injected into the lateral cerebral ventricles of sheep, goats and rabbits

    PubMed Central

    Bligh, J.; Cottle, W. H.; Maskrey, M.

    1971-01-01

    1. The influences of ambient temperature (Ta) on the thermoregulatory effector activities and the body temperature (Tb) of intraventricular injections into the sheep, goat and rabbit of 5-hydroxytryptamine (5-HT), noradrenaline (NA), acetylcholine (ACh), carbachol and eserine, have been interpreted in terms of a simple neuronal model of the pathways between thermosensors and thermoregulatory effectors. 2. In all three species 5-HT in minimal doses caused a rise in respiratory frequency (RF) and a fall in Tb at high Ta, and a reduction in EMG activity and a fall in Tb at low Ta. These effects could be interpreted as those of an excitatory transmitter acting on the warm receptor—heat loss pathway. 3. In all three species NA caused a reduction in RF and a rise in Tb at high Ta, and a reduction in EMG activity and a fall in Tb at low Ta. These effects are interpreted as those of an inhibitory transmitter acting both on the warm sensor—heat loss pathways and on the cold sensor—heat production pathway. 4. The effects of ACh and the cholinomimetic substances carbachol and eserine are complex and more difficult to interpret. In small doses the effects on the sheep and goat are those of an excitatory transmitter on the cold sensor—heat production pathway. There was an increase in EMG activity and a rise in Tb at low Ta, and a reduction in RF and a rise in Tb at high Ta. At higher dose levels in the goat and at all dose levels in the rabbit these substances had the reverse effects which are attributed to a synaptic block due to the excess of the excitatory substance. 5. The effects of ambient temperature and injected substances upon ear temperature are consistent with the predictions of the model if it is assumed (a) that at high and low ambient temperatures direct thermal effects on ear vessels dominate those of the sympathetic innervation, and (b) that the warm sensor influence is to lower peripheral vasomotor tone, and the cold sensor influence is to increase it

  18. Efficacy and safety of 5-hydroxytryptamine 3 receptor antagonists in irritable bowel syndrome: A systematic review and meta-analysis of randomized controlled trials

    PubMed Central

    Tang, Yurong; Xiong, Wenjie; Shen, Xiaoxue; Jiang, Ling; Lin, Lin

    2017-01-01

    Aim We assessed the efficacy and safety of 5-hydroxytryptamine (5-HT3) receptor antagonists in adults with non-constipated irritable bowel syndrome (IBS) or diarrhea-predominant IBS (IBS-D). Methods We searched PubMed, MEDLINE, EMBASE, and the Cochrane Controlled Trials Register for randomized controlled trials (RCTs) involving adults with non-constipated IBS or IBS-D that compared 5-HT3 receptor antagonists with placebo or other conventional treatment. Dichotomous symptom data were pooled to obtain the relative risk (RR) and 95% confidence intervals (CIs) for improving global IBS symptoms, abdominal pain and abnormal bowel habits, or stool consistency symptoms after therapy, and adverse events, including constipation. Meta- analysis was performed with Mantel Haenszel method using Revman 5.3 software. Results We included 21 RCTs; 16 were high quality (Jadad score ≥ 4). The pooled RR of global IBS symptoms improved by 5-HT3 receptor antagonists versus placebo or mebeverine was 1.56 (95% CI: 1.43–1.71); alosetron, ramosetron, and cilansetron had similar treatment effects. The pooled RR of abdominal pain relieved by 5-HT3 receptor antagonists versus placebo was 1.33 (95% CI: 1.26–1.39). The pooled RR showed that 5-HT3 receptor antagonists improved abnormal bowel habits or stool consistency symptoms (RR = 1.63, 95% CI: 1.33, 1.99). The pooled RR of adverse events following 5-HT3 receptor antagonist treatment was 1.15 (95% CI: 1.08, 1.22). Subgroup analysis indicated that alosetron had a high rate of adverse effects (RR = 1.16, 95% CI: 1.08, 1.25); adverse events following ramosetron treatment were not statistically significantly different. 5-HT3 receptor antagonists were likelier to cause constipation: the pooled RR of constipation developing with 5-HT3 receptor antagonist versus placebo was 3.71 (95% CI: 2.98–4.61). However, constipation was likelier in patients with non-constipated IBS after taking 5-HT3 receptor antagonists than in patients with IBS-D only

  19. Evidence for the existence of FGFR1-5-HT1A heteroreceptor complexes in the midbrain raphe 5-HT system.

    PubMed

    Borroto-Escuela, Dasiel O; Narvaez, Manuel; Pérez-Alea, Mileidys; Tarakanov, Alexander O; Jiménez-Beristain, Antonio; Mudó, Giuseppa; Agnati, Luigi F; Ciruela, Francisco; Belluardo, Natale; Fuxe, Kjell

    2015-01-02

    The ascending midbrain 5-HT neurons known to contain 5-HT1A autoreceptors may be dysregulated in depression due to a reduced trophic support. With in situ proximity ligation assay (PLA) and supported by co-location of the FGFR1 and 5-HT1A immunoreactivities in midbrain raphe 5-HT cells, evidence for the existence of FGFR1-5-HT1A heteroreceptor complexes were obtained in the dorsal and median raphe nuclei of the Sprague-Dawley rat. Their existence in the rat medullary raphe RN33B cell cultures was also established. After combined FGF-2 and 8-OH-DPAT treatment, a marked and significant increase in PLA positive clusters was found in the RN33B cells. Similar results were reached upon coactivation by agonists in HEK293T cells using the Fluorescent Resonance Energy Transfer (FRET) technique resulting in increased FRETmax and reduced FRET50 values. The heteroreceptor complex formation was dependent on TMV of the 5-HT1A receptor since it was blocked by incubation with TMV but not with TMII. Taken together, the 5-HT1A autoreceptors by being recruited into a FGFR1-5-HT1A heteroreceptor complex in the midbrain raphe 5-HT nerve cells may develop a novel function, namely a trophic role in many midbrain 5-HT neuron systems originating from the dorsal and medianus raphe nuclei.

  20. Self-transcendence trait and its relationship with in vivo serotonin transporter availability in brainstem raphe nuclei: An ultra-high resolution PET-MRI study.

    PubMed

    Kim, Jong-Hoon; Son, Young-Don; Kim, Jeong-Hee; Choi, Eun-Jung; Lee, Sang-Yoon; Joo, Yo-Han; Kim, Young-Bo; Cho, Zang-Hee

    2015-12-10

    Self-transcendence is an inherent human personality trait relating to the experience of spiritual aspects of the self. We examined the relationship between self-transcendence and serotonin transporter (SERT) availability in brainstem raphe nuclei, which are collections of five different serotonergic nuclei with rostro-caudal extension, using ultra-high resolution magnetic resonance imaging (MRI) and positron emission tomography (PET) with (11)C-3-amino-4-(2-dimethylaminomethylphenylthio)benzonitrile ([(11)C]DASB) to elucidate potential roles of serotonergic neuronal activities in this personality trait. Sixteen healthy subjects completed 7.0T MRI and High Resolution Research Tomograph (HRRT) PET. The regions of interest (ROIs) included the dorsal raphe nucleus (R1), median raphe nucleus (R2), raphe pontis (R3), and the caudal raphe nuclei (R4 and R5). For the estimation of SERT availability, the binding potential (BPND) was derived using the simplified reference tissue model (SRTM2). The Temperament and Character Inventory was used to measure self-transcendence. The analysis revealed that the self-transcendence total score had a significant negative correlation with the [(11)C]DASB BPND in the caudal raphe (R5). The subscale score for spiritual acceptance was significantly negatively correlated with the [(11)C]DASB BPND in the median raphe nucleus (R2). The results indicate that the self-transcendence trait is associated with SERT availability in specific raphe subnuclei, suggesting that the serotonin system may serve as an important biological basis for human self-transcendence. Based on the connections of these nuclei with cortico-limbic and visceral autonomic structures, the functional activity of these nuclei and their related neural circuitry may play a crucial role in the manifestation of self-transcendence. Copyright © 2015. Published by Elsevier B.V.

  1. EphrinA5 Signaling Is Required for the Distinctive Targeting of Raphe Serotonin Neurons in the Forebrain

    PubMed Central

    Muzerelle, Aude

    2017-01-01

    Serotonin (5-HT) neurotransmission in the brain relies on a widespread axon terminal network originating from the hindbrain raphe nuclei. These projections are topographically organized such that the dorsal (DR), and median raphe (MnR) nuclei have different brain targets. However, the guidance molecules involved in this selective targeting in development are unknown. Here, we show the implication of ephrinA5 signaling in this process. We find that the EphA5 gene is selectively expressed in a subset of 5-HT neurons during embryonic and postnatal development. Highest coexpression of EphA5 and the 5-HT marker Tph2 is found in the DR, with lower coexpression in the MnR, and hardly any colocalization of the caudal raphe in the medulla. Accordingly, ephrinA induced a dose-dependent collapse response of 5-HT growth cones cultured from rostral but not caudal raphe. Ectopic expression of ephrinA3, after in utero electroporation in the amygdala and piriform cortex, repelled 5-HT raphe fiber ingrowth. Conversely, misplaced DR 5-HT axons were found in ephrin A5 knockout mice in brain regions that are normally only targeted by MnR 5-HT axons. This causes an overall increase in the density of 5-HT innervation in the ventromedial hypothalamus, the suprachiasmatic nucleus, and the olfactory bulb. All these brain areas have high expression of ephrinAs at the time of 5-HT fiber ingrowth. Present results show for the first time the role of a guidance molecule for the region-specific targeting of raphe neurons. This has important implications to understand how functional parsing of central 5-HT neurons is established during development. PMID:28197551

  2. Sleep deprivation reduces the citalopram-induced inhibition of serotoninergic neuronal firing in the nucleus raphe dorsalis of the rat.

    PubMed

    Prévot, E; Maudhuit, C; Le Poul, E; Hamon, M; Adrien, J

    1996-12-01

    Sleep deprivation (SD) for one night induces mood improvement in depressed patients. However, relapse often occurs on the day after deprivation subsequently to a sleep episode. In light of the possible involvement of central serotonin (5-hydroxytryptamine, 5-HT) neurotransmission in both depression and sleep mechanisms, we presently investigated, in the rat, the effects of SD and recovery sleep on the electrophysiological response of 5-HT neurons in the nucleus raphe dorsalis (NRD) to an acute challenge with the 5-HT reuptake blocker citalopram. In all rats, citalopram induced a dose-dependent inhibition of the firing of NRD neurons recorded under chloral hydrate anaesthesia. After SD, achieved by placing rats in a slowly rotating cylinder for 24 h, the inhibitory action of citalopram was significantly reduced (with a concomitant 53% increase in its ED50 value). After a recovery period of 4 h, a normal susceptibility of the firing to citalopram was restored. The decreased sensitivity of 5-HT neuronal firing to the inhibitory effect of citalopram after SD probably results in an enhancement of 5-HT neurotransmission. Such an adaptive phenomenon (similar to that reported after chronic antidepressant treatment), and its normalization after recovery sleep, parallel the mood improvement effect of SD and the subsequent relapse observed in depressed patients. These data suggest that the associated changes in 5-HT autocontrol of the firing of NRD serotoninergic neurons are relevant to the antidepressant action of SD.

  3. Sleep cycles in cats during chronic electrical stimulation of the area postrema and the anterior raphe.

    PubMed

    Bronzino, J D; Stern, W C; Leahy, J P; Morgane, P J

    1976-01-01

    Sleep-waking profiles were obtained from 130 7 hr stimulation-EEG recording sessions in a series of cats bearing chronically implanted stimulating electrodes in the regions of the area postrema and anterior raphe nuclei. The results indicated that: (a) during electrical stimulation of the region of the area postrema with 0.5 or 10 Hz at 1 and 2 mA there were significant increases in the occurrence of the deeper aspects of slow-wave sleep and in REM sleep. These elevations were significant in comparison to nonstimulation baselines and to sleep profiles obtained during stimulation of points located dorsal and anterior to the area postrema. (b) Stimulation of the medial reticular formation including the anterior raphe using the same parameters employed for the area postrema did not alter the occurrence of any stage of sleep. These findings indicate that the region of the area postrema may be more involved in the generation of sleep than the anterior raphe nuclei.

  4. Raphe lesions and 5,7-dihydroxytryptamine induce grooming reflexes in adrenalectomized cats.

    PubMed

    Swenson, R M; Randall, W

    1980-04-01

    Grooming reflexes are induced by frontal neocortical, pontile, or spinal lesions in dogs and cats. In intact cats, the combined treatments of adrenalectomy and para-chlorophenylalanine administration induce grooming reflexes. Two other ways of depleting serotonin (with 5,7-dihydroxytryptamine and raphe lesions) were combined with adrenalectomy in the present study as further tests that serotonin and glucocorticoid hormones are the critical factors in the induction of grooming reflexes. Because the deficit in serotonin is confined to the superior colliculi in cats with frontal and pontile lesions, 5,7-dihydroxytryptamine (5,7-DHT) was injected directly into the superior colliculi at eight sites, 2 microgram/site (1 microliter at .5 microliter/min). Electrolytic dc lesions of the dorsal and superior central raphe nuclei were made in another group, and then both groups were adrenalectomized. There were three control groups: (a) a group with vehicle injections in the superior colliculi and laporatomies, (b) a group with 5,7-DHT injections in the superior colliculi, and (c) a group with the raphe lesions. Large receptive fields for grooming reflexes occurred only in the groups with combined treatments. Thus the mechanism of induction of grooming reflexes by central nervous system lesions involves independent changes in a hormonal and a neurotransmitter system which combine to effect the change in behavior.

  5. Histofluorescence studies on the effect of 1,3-dimethyl-5-adamantanamine (D-145) on serotonin neurons in midbrain raphe nuclei.

    PubMed

    Smialowska, M

    1976-01-01

    1,3-Dimethyl-5-adamantanamine (D-145), a dopamine system stimulating agent, given at doses of 10-40 mg/kg ip, 2-5 hr before sacrifice, depressed the intensity of serotonin fluorescence in the rat midbrain raphe nuclei. Spiroperidol, 2 mg/kg ip, given 5 min before D-145, prevented the depression of serotonin fluorescence in the dorsal raphe nucleus (NDR), but not in the other groups of serotonin midbrain neurons. The results suggest a functional interaction between dopaminergic neurons and serotoninergic neurons in NDR.

  6. The sites of action of 5-hydroxytryptamine in nerve-muscle preparations from the guinea-pig small intestine and colon

    PubMed Central

    Costa, M.; Furness, J.B.

    1979-01-01

    1 The sites of action of 5-hydroxytryptamine (5-HT) were examined in isolated segments of guinea-pig intestine. Mechanical records were taken from the longitudinal muscle of the ileum and proximal colon and from the circular muscle of the ileum and distal colon. 2 In order to examine direct actions of 5-HT, nerve-mediated responses were blocked with tetrodotoxin (0.2 μg/ml). There was a gradient in the responsiveness of the longitudinal muscle of the ileum; in the proximal ileum it was usually unresponsive, whereas in the distal ileum about 30% of the amplitude of contraction was caused by a direct effect on the muscle. In the circular muscle from all parts of the ileum, direct effects on the muscle were weak or absent. In the distal colon, the circular muscle was almost always unresponsive to direct effects of 5-HT even when concentrations of 5-HT as great as 100 μg/ml were used. All direct actions of 5-HT on intestinal muscle were blocked by methysergide (1 μg/ml), which itself did not affect nerve-mediated responses. 3 Excitatory cholinergic nerves and excitatory and inhibitory nerves which released unidentified substances were all stimulated by 5-HT. The contractions mediated through cholinergic nerves were blocked by hyoscine (0.6 μg/ml). 4 Tachyphylaxis to the action of 5-HT occurred both for effects mediated through nerves and for direct effects on the muscle. Responses returned promptly after 5-HT was washed from the organ bath. 5 While 5-HT blocked its own action on neural receptors, it did not antagonize the stimulation of nicotinic receptors on cholinergic neurones by 1-1 dimethyl-4-phenylpiperazinium iodide (DMPP). Moreover, pentolinium markedly reduced contractions caused by DMPP without significantly affecting responses to 5-HT. In contrast, (+)-tubocurarine, another nicotinic receptor antagonist, was effective in reducing contractions caused by 5-HT. 6 Phenyldiguanide, which has been reported to antagonize the stimulant action of 5-HT on

  7. Inhibitory action of niflumic acid on noradrenaline- and 5-hydroxytryptamine-induced pressor responses in the isolated mesenteric vascular bed of the rat

    PubMed Central

    Criddle, D N; Soares de Moura, R; Greenwood, I A; Large, W A

    1997-01-01

    The effects of niflumic acid, an inhibitor of calcium-activated chloride currents, were compared with the actions of the calcium channel blocker nifedipine on noradrenaline- and 5-hydroxytryptamine (5-HT)-induced pressor responses of the rat perfused isolated mesenteric vascular bed.Bolus injections of noradrenaline (1 and 10 nmol) increased the perfusion pressure in a dose-dependent manner. Nifedipine (1 μM) inhibited the increase in pressure produced by 1 nmol noradrenaline by 31±5%. Niflumic acid (10 and 30 μM) also inhibited the noradrenaline-induced increase in perfusion pressure and 30 μM niflumic acid reduced the pressor response to 1 nmol noradrenaline by 34±6%.The increases in perfusion elicited by 5-HT (0.3 and 3 nmol) were reduced by niflumic acid (10 and 30 μM) in a concentration-dependent manner and 30 μM niflumic acid inhibited responses to 0.3 and 3 nmol 5-HT by, respectively, 49±8% and 50±7%. Nifedipine (1 μM) decreased the pressor response to 3 nmol 5-HT by 44±9%.In the presence of a combination of 30 μM niflumic acid and 1 μM nifedipine the inhibition of the pressor effects of noradrenaline (10 nmol) and 5-HT (3 nmol) was not significantly greater than with niflumic acid (30 μM) alone. Thus the effects of niflumic acid and nifedipine were not additive.In Ca-free conditions the transient contractions induced by 5-HT (3 nmol) were not reduced by 30 μM niflumic acid, suggesting that this agent does not inhibit calcium release from the intracellular store or the binding of 5-HT to its receptor.Niflumic acid 30 μM did not inhibit the pressor responses induced by KCl (20 and 60 μmol) which were markedly reduced by 1 μM nifedipine. In addition, 1 μM levcromakalim decreased pressor responses produced by 20 μmol KCl. These data suggest that niflumic acid does not block directly calcium channels or activate potassium channels.It is concluded that niflumic acid selectively reduces a

  8. [Influence of occupational stress and 5-hydroxytryptamine 2A receptor gene polymorphisms on depression in workers in a thermal power plant].

    PubMed

    Wu, H; Wang, F F; Zhou, W H; Gu, G Z; Yu, S F

    2016-10-20

    Objective: To investigate the association of occupational stress and 5-hydroxytryptamine 2A (5-HT2A) receptor gene polymorphisms with depression. Methods: In November 2010, cluster sampling was used to select 589 workers in a thermal power plant as study subjects. Questionnaires were used to investigate demographic features and occupational stressors. Polymerase chain reaction-restriction fragment length polymorphism was used to detect the genotypes of T102C and A-1438G in 5-HT2A receptor gene in 589 workers. Results: High-level daily hassles (OR=3.013, 95%CI 1.642~5.530) , more negative emotion (OR=4.808, 95% CI 2.662~8.681) , more body needs (OR=1.890, 95% CI 1.034~3.453) , and severe role conflict (OR=1.815, 95% CI 1.002~3.288) were risk factors for depression, while high rewards (OR=0.424, 95% CI 0.226~0.796) was the protective factor against depression (all P<0.05). There were no significant differences in T102C genotype and allele distributions between the groups with and without depression (P>0.05) ; there was a significant difference in A-1438G genotype distribution between the groups with and without depression (χ(2)= 9.573, P<0.05) , while there was no significant difference in A-1438G allele distribution between these groups (P>0.05). The risk of depression in the workers with high-level daily hassles who carried TC genotype (OR= 4.473, 95% CI 1.161~17.238) or CC genotype (OR=5.176, 95% CI 1.367~19.593) of T102C was 4.473 and 5.176 times that in those with low-level daily hassles who carried TT genotype, and the risk of depression in the workers with more negative emotions who carried TC genotype (OR=5.667, 95%CI 1.204~26.673) or CC genotype (OR=8.114, 95% CI 1.747~37.677) of T102C was 5.667 and 8.114 times that in those with less negative emotion who carried TT genotype. The risk of depression in the workers with high-level daily hassles who carried AG genotype (OR=4.505, 95% CI 2.215~9.162) or GG genotype (OR=6.484, 95% CI 2.562~ 16.414) of A-1438G

  9. Midbrain Raphe Stimulation Improves Behavioral and Anatomical Recovery from Fluid-Percussion Brain Injury

    PubMed Central

    Carballosa Gonzalez, Melissa M.; Blaya, Meghan O.; Alonso, Ofelia F.; Bramlett, Helen M.

    2013-01-01

    Abstract The midbrain median raphe (MR) and dorsal raphe (DR) nuclei were tested for their capacity to regulate recovery from traumatic brain injury (TBI). An implanted, wireless self-powered stimulator delivered intermittent 8-Hz pulse trains for 7 days to the rat's MR or DR, beginning 4–6 h after a moderate parasagittal (right) fluid-percussion injury. MR stimulation was also examined with a higher frequency (24 Hz) or a delayed start (7 days after injury). Controls had sham injuries, inactive stimulators, or both. The stimulation caused no apparent acute responses or adverse long-term changes. In water-maze trials conducted 5 weeks post-injury, early 8-Hz MR and DR stimulation restored the rate of acquisition of reference memory for a hidden platform of fixed location. Short-term spatial working memory, for a variably located hidden platform, was restored only by early 8-Hz MR stimulation. All stimulation protocols reversed injury-induced asymmetry of spontaneous forelimb reaching movements tested 6 weeks post-injury. Post-mortem histological measurement at 8 weeks post-injury revealed volume losses in parietal-occipital cortex and decussating white matter (corpus callosum plus external capsule), but not hippocampus. The cortical losses were significantly reversed by early 8-Hz MR and DR stimulation, the white matter losses by all forms of MR stimulation. The generally most effective protocol, 8-Hz MR stimulation, was tested 3 days post-injury for its acute effect on forebrain cyclic adenosine monophosphate (cAMP), a key trophic signaling molecule. This procedure reversed injury-induced declines of cAMP levels in both cortex and hippocampus. In conclusion, midbrain raphe nuclei can enduringly enhance recovery from early disseminated TBI, possibly in part through increased signaling by cAMP in efferent targets. A neurosurgical treatment for TBI using interim electrical stimulation in raphe repair centers is suggested. PMID:22963112

  10. Midbrain raphe stimulation improves behavioral and anatomical recovery from fluid-percussion brain injury.

    PubMed

    Carballosa Gonzalez, Melissa M; Blaya, Meghan O; Alonso, Ofelia F; Bramlett, Helen M; Hentall, Ian D

    2013-01-15

    The midbrain median raphe (MR) and dorsal raphe (DR) nuclei were tested for their capacity to regulate recovery from traumatic brain injury (TBI). An implanted, wireless self-powered stimulator delivered intermittent 8-Hz pulse trains for 7 days to the rat's MR or DR, beginning 4-6 h after a moderate parasagittal (right) fluid-percussion injury. MR stimulation was also examined with a higher frequency (24 Hz) or a delayed start (7 days after injury). Controls had sham injuries, inactive stimulators, or both. The stimulation caused no apparent acute responses or adverse long-term changes. In water-maze trials conducted 5 weeks post-injury, early 8-Hz MR and DR stimulation restored the rate of acquisition of reference memory for a hidden platform of fixed location. Short-term spatial working memory, for a variably located hidden platform, was restored only by early 8-Hz MR stimulation. All stimulation protocols reversed injury-induced asymmetry of spontaneous forelimb reaching movements tested 6 weeks post-injury. Post-mortem histological measurement at 8 weeks post-injury revealed volume losses in parietal-occipital cortex and decussating white matter (corpus callosum plus external capsule), but not hippocampus. The cortical losses were significantly reversed by early 8-Hz MR and DR stimulation, the white matter losses by all forms of MR stimulation. The generally most effective protocol, 8-Hz MR stimulation, was tested 3 days post-injury for its acute effect on forebrain cyclic adenosine monophosphate (cAMP), a key trophic signaling molecule. This procedure reversed injury-induced declines of cAMP levels in both cortex and hippocampus. In conclusion, midbrain raphe nuclei can enduringly enhance recovery from early disseminated TBI, possibly in part through increased signaling by cAMP in efferent targets. A neurosurgical treatment for TBI using interim electrical stimulation in raphe repair centers is suggested.

  11. The highly selective 5-hydroxytryptamine (5-HT)2A receptor antagonist, EMD 281014, significantly increases swimming and decreases immobility in male congenital learned helpless rats in the forced swim test.

    PubMed

    Patel, Jignesh G; Bartoszyk, Gerd D; Edwards, Emmeline; Ashby, Charles R

    2004-04-01

    We examined the effect of the highly selective 5-hydroxytryptamine (5-HT)(2A) receptor antagonist 7-[4-[2-(4-fluoro-phenyl)-ethyl]-piperazine-1-carbonyl]-1H-indole-3-carbonitrile HCl (EMD 281014) in congenital learned helpless male rats in the forced swim test. The administration of EMD-281014 (0.3-30 mg/kg i.p.) to congenital learned helpless rats dose-dependently and significantly (at 10 and 30 mg/kg) decreased immobility and increased swimming compared to vehicle-treated animals. Thus, EMD 281014 produces effects in the forced swim test resembling those of antidepressants.

  12. Colocalization of serotonin and vesicular glutamate transporter 3-like immunoreactivity in the midbrain raphe of Syrian hamsters (Mesocricetus auratus).

    PubMed

    Mintz, Eric M; Scott, Tamara J

    2006-02-13

    Vesicular glutamate transporter 3 (VGLUT3) expression has been specifically localized to brain regions rich in serotonergic cells. It has been suggested that this transporter may contribute to the regulation of extracellular glutamate concentrations via a nonsynaptic mechanism. In this study, we examine the colocalization of vesicular glutamate transporter 3 immunoreactivity with serotonin immunoreactivity in the dorsal and median raphe nuclei of Syrian hamsters. Brain sections from adult hamsters were fluorescently labeled for serotonin-ir and VGLUT3-ir and examined using confocal microscopy. The results indicate that most serotonergic cells of the midbrain raphe also expressed vesicular glutamate transporter 3. In addition, nonserotonergic cells in these brain regions also show immunoreactivity for the transporter. These data confirm previous findings of vesicular glutamate transporter 3 expression in serotonergic and nonserotonergic neurons in rats. These findings suggest that the location of vesicular glutamate transporter 3 may be as much a function of neuroanatomical location as of the neurochemical identity of the expressing neurons.

  13. Effects of creatine monohydrate supplementation and exercise on depression-like behaviors and raphe 5-HT neurons in mice.

    PubMed

    Ahn, Na-Ri; Leem, Yea-Hyun; Kato, Morimasa; Chang, Hyuk-ki

    2016-09-01

    The effects of creatine and exercise on chronic stress-induced depression are unclear. In the present study, we identified the effects of 4-week supplementation of creatine monohydrate and/or exercise on antidepressant behavior and raphe 5-HT expression in a chronic mild stress-induced depressed mouse model. Seven-week-old male C57BL/6 mice (n=48) were divided randomly into 5 groups: (1) non-stress control (CON, n=10), (2) stress control (ST-CON, n=10), (3) stress and creatine intake (ST-Cr, n=10), (4) stress and exercise (ST-Ex, n=9), and (5) combined stress, exercise, and creatine intake (ST-Cr+Ex, n=9). After five weeks' treatment, we investigated using both anti-behavior tests (the Tail Suspension Test (TST) and the Forced Swimming Test (FST)), and 5-HT expression in the raphe nuclei (the dorsal raphe (DR) and median raphe (MnR)). Stress for 4 weeks significantly increased depressive behaviors in the mice. Treatment with creatine supplementation combined with exercise significantly decreased depressive behaviors as compared with the CON-ST group in both the TST and FST tests. With stress, 5-HT expression in the raphe nuclei decreased significantly. With combined creatine and exercise, 5-HT positive cells increased significantly and had a synergic effect on both DR and MnR. The present study found that even a single treatment of creatine or exercise has partial effects as an antidepressant in mice with chronic mild stress-induced depression. Furthermore, combined creatine and exercise has synergic effects and is a more effective prescription than a single treatment.

  14. Effects of creatine monohydrate supplementation and exercise on depression-like behaviors and raphe 5-HT neurons in mice

    PubMed Central

    Ahn, Nari; Leem, Yea Hyun; Kato, Morimasa; Chang, Hyukki

    2016-01-01

    [Purpose] The effects of creatine and exercise on chronic stress-induced depression are unclear. In the present study, we identified the effects of 4-week supplementation of creatine monohydrate and/or exercise on antidepressant behavior and raphe 5-HT expression in a chronic mild stress-induced depressed mouse model. [Methods] Seven-week-old male C57BL/6 mice (n=48) were divided randomly into 5 groups: (1) non-stress control (CON, n=10), (2) stress control (ST-CON, n=10), (3) stress and creatine intake (ST-Cr, n=10), (4) stress and exercise (ST-Ex, n=9), and (5) combined stress, exercise, and creatine intake (ST-Cr+Ex, n=9). After five weeks’ treatment, we investigated using both anti-behavior tests (the Tail Suspension Test (TST) and the Forced Swimming Test (FST)), and 5-HT expression in the raphe nuclei (the dorsal raphe (DR) and median raphe (MnR)). [Results] Stress for 4 weeks significantly increased depressive behaviors in the mice. Treatment with creatine supplementation combined with exercise significantly decreased depressive behaviors as compared with the CON-ST group in both the TST and FST tests. With stress, 5-HT expression in the raphe nuclei decreased significantly. With combined creatine and exercise, 5-HT positive cells increased significantly and had a synergic effect on both DR and MnR. [Conclusion] The present study found that even a single treatment of creatine or exercise has partial effects as an antidepressant in mice with chronic mild stress-induced depression. Furthermore, combined creatine and exercise has synergic effects and is a more effective prescription than a single treatment. PMID:27757384

  15. Cell-Type-Specific Modulation of Sensory Responses in Olfactory Bulb Circuits by Serotonergic Projections from the Raphe Nuclei

    PubMed Central

    Brunert, Daniela; Tsuno, Yusuke; Rothermel, Markus; Shipley, Michael T.

    2016-01-01

    Serotonergic neurons in the brainstem raphe nuclei densely innervate the olfactory bulb (OB), where they can modulate the initial representation and processing of olfactory information. Serotonergic modulation of sensory responses among defined OB cell types is poorly characterized in vivo. Here, we used cell-type-specific expression of optical reporters to visualize how raphe stimulation alters sensory responses in two classes of GABAergic neurons of the mouse OB glomerular layer, periglomerular (PG) and short axon (SA) cells, as well as mitral/tufted (MT) cells carrying OB output to piriform cortex. In PG and SA cells, brief (1–4 s) raphe stimulation elicited a large increase in the magnitude of responses linked to inhalation of ambient air, as well as modest increases in the magnitude of odorant-evoked responses. Near-identical effects were observed when the optical reporter of glutamatergic transmission iGluSnFR was expressed in PG and SA cells, suggesting enhanced excitatory input to these neurons. In contrast, in MT cells imaged from the dorsal OB, raphe stimulation elicited a strong increase in resting GCaMP fluorescence with only a slight enhancement of inhalation-linked responses to odorant. Finally, optogenetically stimulating raphe serotonergic afferents in the OB had heterogeneous effects on presumptive MT cells recorded extracellularly, with an overall modest increase in resting and odorant-evoked responses during serotonergic afferent stimulation. These results suggest that serotonergic afferents from raphe dynamically modulate olfactory processing through distinct effects on multiple OB targets, and may alter the degree to which OB output is shaped by inhibition during behavior. SIGNIFICANCE STATEMENT Modulation of the circuits that process sensory information can profoundly impact how information about the external world is represented and perceived. This study investigates how the serotonergic system modulates the initial processing of olfactory

  16. Cell-Type-Specific Modulation of Sensory Responses in Olfactory Bulb Circuits by Serotonergic Projections from the Raphe Nuclei.

    PubMed

    Brunert, Daniela; Tsuno, Yusuke; Rothermel, Markus; Shipley, Michael T; Wachowiak, Matt

    2016-06-22

    Serotonergic neurons in the brainstem raphe nuclei densely innervate the olfactory bulb (OB), where they can modulate the initial representation and processing of olfactory information. Serotonergic modulation of sensory responses among defined OB cell types is poorly characterized in vivo Here, we used cell-type-specific expression of optical reporters to visualize how raphe stimulation alters sensory responses in two classes of GABAergic neurons of the mouse OB glomerular layer, periglomerular (PG) and short axon (SA) cells, as well as mitral/tufted (MT) cells carrying OB output to piriform cortex. In PG and SA cells, brief (1-4 s) raphe stimulation elicited a large increase in the magnitude of responses linked to inhalation of ambient air, as well as modest increases in the magnitude of odorant-evoked responses. Near-identical effects were observed when the optical reporter of glutamatergic transmission iGluSnFR was expressed in PG and SA cells, suggesting enhanced excitatory input to these neurons. In contrast, in MT cells imaged from the dorsal OB, raphe stimulation elicited a strong increase in resting GCaMP fluorescence with only a slight enhancement of inhalation-linked responses to odorant. Finally, optogenetically stimulating raphe serotonergic afferents in the OB had heterogeneous effects on presumptive MT cells recorded extracellularly, with an overall modest increase in resting and odorant-evoked responses during serotonergic afferent stimulation. These results suggest that serotonergic afferents from raphe dynamically modulate olfactory processing through distinct effects on multiple OB targets, and may alter the degree to which OB output is shaped by inhibition during behavior. Modulation of the circuits that process sensory information can profoundly impact how information about the external world is represented and perceived. This study investigates how the serotonergic system modulates the initial processing of olfactory information by the

  17. Allosteric interactions between the binding sites of receptor agonists and guanine nucleotides: a comparative study of the 5-hydroxytryptamine1A and adenosine A1 receptor systems in rat hippocampal membranes.

    PubMed

    Mahle, C D; Wiener, H L; Yocca, F D; Maayani, S

    1992-12-01

    The ternary complex formed between agonist, receptor and guanine nucleotide binding protein and its destabilization by guanine nucleotides (GN) was utilized to study early events in signal transduction, by characterizing the allosteric interactions between agonist and GN binding to the receptor/guanine nucleotide binding protein, G complex for adenosine A1 and 5-hydroxytryptamine1A receptors. The functional interaction between the ternary complex and GTP was examined by assaying adenylyl cyclase activity. Binding of a full adenosine A1 agonist ([3H]-R-(-)-N6-(2-phenylisopropyl)adenosine), and a full [(+-)-[3H]-8-hydroxydipropylaminotetralin] and partial ([3H]-8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8- azaspirol[4.5]-decane-7,9-dione) 5-hydroxytryptamine1A agonist was examined in relation to the binding of GN. The amount of ternary complex formed depended upon receptor type and drug relative efficacy. The ratio between the drug's EC50 value (adenylyl cyclase) and dissociation constant (binding) was also receptor and drug relative efficacy dependent. 5'-Guanylylimidodiphosphate (100 microM) caused an approximately 50% decrease in the Bmax for all drugs without affecting Kd values. 5'-Guanylylimidodiphosphate and guanosine 5'-O-(3-thiotriphosphate) attenuated [3H]-agonist binding in a concentration-dependent and saturable manner, with IC50 values increased 2- to 6-fold with increasing receptor occupancy. IC50 values were approximately one-tenth lower at the 5-hydroxytryptamine1A receptor than adenosine A1 receptor; similar values were obtained for inhibition of (+-)-[3H]-8-hydroxydipropylaminotetralin and [3H]-8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8- azaspirol[4.5]-decane-7,9-dione binding, suggesting an independence of agonist efficacy. We propose that the stabilization of the ternary complex by hormone binding, measured by Bmax values, is related to drug-relative efficacy, thus the amount of ternary complex available for destabilization by GN is

  18. Mapping the binding site pocket of the serotonin 5-Hydroxytryptamine2A receptor. Ser3.36(159) provides a second interaction site for the protonated amine of serotonin but not of lysergic acid diethylamide or bufotenin.

    PubMed

    Almaula, N; Ebersole, B J; Zhang, D; Weinstein, H; Sealfon, S C

    1996-06-21

    Like other amine neurotransmitters that activate G-protein-coupled receptors, 5-hydroxytryptamine (5-HT) binds to the 5-HT2A receptor through the interaction of its cationic primary amino group with the conserved Asp3.32(155) in transmembrane helix 3. Computational experiments with a 5-HT2A receptor model suggest that the same functional group of 5-hydroxytryptamine also forms a hydrogen bond with the side chain of Ser3.36(159), which is adjacent in space to Asp3.32(155). However, other 5-HT2A receptor ligands like lysergic acid diethylamide (LSD), in which the amine nitrogen is embedded in a heterocycle, or N,N-dimethyl 5-HT, in which the side chain is a tertiary amine, are found in the computational simulations to interact with the aspartate but not with the serine, due mainly to steric hindrance. The predicted difference in the interaction of various ligands in the same receptor binding pocket was tested with site-directed mutagenesis of Ser3.36(159) --> Ala and Ser3.36(159) --> Cys. The alanine substitution led to an 18-fold reduction in 5-HT affinity and the cysteine substitution to an intermediate 5-fold decrease. LSD affinity, in contrast, was unaffected by either mutation. N,N-Dimethyl 5-HT affinity was unaffected by the cysteine mutation and had a comparatively small 3-fold decrease in affinity for the alanine mutant. These findings identify a mode of ligand-receptor complexation that involves two receptor side chains interacting with the same functional group of specific serotonergic ligands. This interaction serves to orient the ligands in the binding pocket and may influence the degree of receptor activation.

  19. Origin and evolution of the canal raphe system in diatoms.

    PubMed

    Ruck, Elizabeth C; Theriot, Edward C

    2011-11-01

    One lineage of pennate diatoms has a slit through the siliceous cell wall, called a "raphe," that functions in motility. Raphid pennate diatoms number in the perhaps tens of thousands of species, with the diversity of raphe forms potentially matching this number. Three lineages-the Bacillariales, Rhopalodiales, and Surirellales-possess a complex and presumably highly derived raphe that is physically separated from the cell interior, most often by a set of siliceous braces. Because the relationship among these three lineages is unclear, the number of origins of the canal raphe system and the homology of it and its constitutive parts among these lineages, is equally unclear. We reconstructed the phylogeny of raphid pennate diatoms and included, for the first time, members of all three canal raphid diatom lineages, and used the phylogeny to test specific hypotheses about the origin of the canal raphe. The canal raphe appears to have evolved twice, once in the common ancestor of Bacillariales and once in the common ancestor of Rhopalodiales and Surirellales, which form a monophyletic group in our analyses. These results recommend careful follow-up morphogenesis studies of the canal raphe in these two lineages to determine the underlying developmental basis for this remarkable case of parallel evolution. Copyright © 2011 Elsevier GmbH. All rights reserved.

  20. 5-HT1A receptor activation counteracts c-Fos immunoreactivity induced in serotonin neurons of the raphe nuclei after immobilization stress in the male rat.

    PubMed

    Rioja, José; Santín, Luis J; Doña, Alicia; de Pablos, Laura; Minano, Francisco J; Gonzalez-Baron, Salvador; Aguirre, Jose A

    2006-04-24

    The serotoninergic system and the 5-HT1A receptors have been involved in the brain response to acute stress. The aim of our study was evaluate the role of the 5-HT1A receptors in serotoninergic cells of rostral and caudal raphe nuclei under acute immobilization in rats. Double immunocytochemical staining of 5-hydroxy-tryptamine and c-Fos protein and stereology techniques were used to study the specific cell activation in the raphe nuclei neurons in five groups (control group, immobilization group (immobilization lasting 1 h), DPAT group (8-OH-DPAT 0.3 mg/kg, s.c.), DPAT+IMMO group (8-OH-DPAT 0.3 mg/kg, s.c., 30' prior acute immobilization) and WAY+DPAT+IMMO group (WAY-100635 0.3 mg/kg, s.c. and 8-OH-DPAT 0.3 mg/kg, s.c., 45' and 30', respectively, before immobilization). Our results showed an increase in the number of c-Fos immunoreactive nuclei in serotoninergic cells in both dorsal and median raphe nuclei in the immobilized group. The 8-OH-DPAT pretreatment counteracted the excitatory effects of the acute immobilization in these brain regions. In addition, WAY-100635 administration reduced the effect of 8-OH-DPAT injection, suggesting a selective 5-HT1A receptor role. Raphe pallidus and raphe obscurus did not show any differences among experimental groups. We suggest that somatodendritic 5-HT1A receptors in rostral raphe nuclei may play a crucial role in both mediating the consequences of uncontrollable stress and the possible beneficial effects of treatment with 5-HT1A receptor agonists.

  1. Postnatal maintenance of the 5-Ht1a-Pet1 autoregulatory loop by serotonin in the raphe nuclei of the brainstem

    PubMed Central

    2014-01-01

    Background Despite the importance of 5-HT1A as a major target for the action of several anxiolytics/antidepressant drugs, little is known about its regulation in central serotonin (5-hydroxytryptamine, 5-HT) neurons. Results We report that expression of 5-HT1A and the transcription factor Pet1 was impaired in the rostral raphe nuclei of mice lacking tryptophan hydroxylase 2 (Tph2) after birth. The downregulation of Pet1 was recapitulated in 5-Ht1a -/- mice. Using an explant culture system, we show that reduction of Pet1 and 5-HT1A was rescued in Tph2 -/- brainstem by exogenous 5-HT. In contrast, 5-HT failed to rescue reduced expression of Pet1 in 5-Ht1a -/- brainstem explant culture. Conclusions These results suggest a causal relationship between 5-HT1A and Pet1, and reveal a potential mechanism by which 5-HT1A-Pet1 autoregulatory loop is maintained by 5-HT in a spatiotemporal-specific manner during postnatal development. Our results are relevant to understanding the pathophysiology of certain psychiatric and developmental disorders. PMID:24972638

  2. Addition of the Neurokinin-1-Receptor Antagonist (RA) Aprepitant to a 5-Hydroxytryptamine-RA and Dexamethasone in the Prophylaxis of Nausea and Vomiting Due to Radiation Therapy With Concomitant Cisplatin

    SciTech Connect

    Jahn, Franziska; Jahn, Patrick; Sieker, Frank; Vordermark, Dirk; Jordan, Karin

    2015-08-01

    Purpose: To assess, in a prospective, observational study, the safety and efficacy of the addition of the neurokinin-1-receptor antagonist (NK1-RA) aprepitant to concomitant radiochemotherapy, for the prophylaxis of radiation therapy–induced nausea and vomiting. Patients and Methods: This prospective observational study compared the antiemetic efficacy of an NK1-RA (aprepitant), a 5-hydroxytryptamine-RA, and dexamethasone (aprepitant regimen) versus a 5-hydroxytryptamine-RA and dexamethasone (control regimen) in patients receiving concomitant radiochemotherapy with cisplatin at the Department of Radiation Oncology, University Hospital Halle (Saale), Germany. The primary endpoint was complete response in the overall phase, defined as no vomiting and no use of rescue therapy in this period. Results: Fifty-nine patients treated with concomitant radiochemotherapy with cisplatin were included in this study. Thirty-one patients received the aprepitant regimen and 29 the control regimen. The overall complete response rates for cycles 1 and 2 were 75.9% and 64.5% for the aprepitant group and 60.7% and 54.2% for the control group, respectively. Although a 15.2% absolute difference was reached in cycle 1, a statistical significance was not detected (P=.22). Furthermore maximum nausea was 1.58 ± 1.91 in the control group and 0.73 ± 1.79 in the aprepitant group (P=.084); for the head-and-neck subset, 2.23 ± 2.13 in the control group and 0.64 ± 1.77 in the aprepitant group, respectively (P=.03). Conclusion: This is the first study of an NK1-RA–containing antiemetic prophylaxis regimen in patients receiving concomitant radiochemotherapy. Although the primary endpoint was not obtained, the absolute difference of 10% in efficacy was reached, which is defined as clinically meaningful for patients by international guidelines groups. Randomized phase 3 studies are necessary to further define the potential role of an NK1-RA in this setting.

  3. Addition of the Neurokinin-1-Receptor Antagonist (RA) Aprepitant to a 5-Hydroxytryptamine-RA and Dexamethasone in the Prophylaxis of Nausea and Vomiting Due to Radiation Therapy With Concomitant Cisplatin.

    PubMed

    Jahn, Franziska; Riesner, Anica; Jahn, Patrick; Sieker, Frank; Vordermark, Dirk; Jordan, Karin

    2015-08-01

    To assess, in a prospective, observational study, the safety and efficacy of the addition of the neurokinin-1-receptor antagonist (NK