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Sample records for 5-ht nerve terminals

  1. The Role of 5-HT3 Receptors in Signaling from Taste Buds to Nerves.

    PubMed

    Larson, Eric D; Vandenbeuch, Aurelie; Voigt, Anja; Meyerhof, Wolfgang; Kinnamon, Sue C; Finger, Thomas E

    2015-12-01

    Activation of taste buds triggers the release of several neurotransmitters, including ATP and serotonin (5-hydroxytryptamine; 5-HT). Type III taste cells release 5-HT directly in response to acidic (sour) stimuli and indirectly in response to bitter and sweet tasting stimuli. Although ATP is necessary for activation of nerve fibers for all taste stimuli, the role of 5-HT is unclear. We investigated whether gustatory afferents express functional 5-HT3 receptors and, if so, whether these receptors play a role in transmission of taste information from taste buds to nerves. In mice expressing GFP under the control of the 5-HT(3A) promoter, a subset of cells in the geniculate ganglion and nerve fibers in taste buds are GFP-positive. RT-PCR and in situ hybridization confirmed the presence of 5-HT(3A) mRNA in the geniculate ganglion. Functional studies show that only those geniculate ganglion cells expressing 5-HT3A-driven GFP respond to 10 μM 5-HT and this response is blocked by 1 μM ondansetron, a 5-HT3 antagonist, and mimicked by application of 10 μM m-chlorophenylbiguanide, a 5-HT3 agonist. Pharmacological blockade of 5-HT3 receptors in vivo or genetic deletion of the 5-HT3 receptors reduces taste nerve responses to acids and other taste stimuli compared with controls, but only when urethane was used as the anesthetic. We find that anesthetic levels of pentobarbital reduce taste nerve responses apparently by blocking the 5-HT3 receptors. Our results suggest that 5-HT released from type III cells activates gustatory nerve fibers via 5-HT3 receptors, accounting for a significant proportion of the neural taste response. PMID:26631478

  2. The Role of 5-HT3 Receptors in Signaling from Taste Buds to Nerves

    PubMed Central

    Vandenbeuch, Aurelie; Voigt, Anja; Meyerhof, Wolfgang; Kinnamon, Sue C.; Finger, Thomas E.

    2015-01-01

    Activation of taste buds triggers the release of several neurotransmitters, including ATP and serotonin (5-hydroxytryptamine; 5-HT). Type III taste cells release 5-HT directly in response to acidic (sour) stimuli and indirectly in response to bitter and sweet tasting stimuli. Although ATP is necessary for activation of nerve fibers for all taste stimuli, the role of 5-HT is unclear. We investigated whether gustatory afferents express functional 5-HT3 receptors and, if so, whether these receptors play a role in transmission of taste information from taste buds to nerves. In mice expressing GFP under the control of the 5-HT3A promoter, a subset of cells in the geniculate ganglion and nerve fibers in taste buds are GFP-positive. RT-PCR and in situ hybridization confirmed the presence of 5-HT3A mRNA in the geniculate ganglion. Functional studies show that only those geniculate ganglion cells expressing 5-HT3A-driven GFP respond to 10 μm 5-HT and this response is blocked by 1 μm ondansetron, a 5-HT3 antagonist, and mimicked by application of 10 μm m-chlorophenylbiguanide, a 5-HT3 agonist. Pharmacological blockade of 5-HT3 receptors in vivo or genetic deletion of the 5-HT3 receptors reduces taste nerve responses to acids and other taste stimuli compared with controls, but only when urethane was used as the anesthetic. We find that anesthetic levels of pentobarbital reduce taste nerve responses apparently by blocking the 5-HT3 receptors. Our results suggest that 5-HT released from type III cells activates gustatory nerve fibers via 5-HT3 receptors, accounting for a significant proportion of the neural taste response. SIGNIFICANCE STATEMENT Historically, serotonin (5-hydroxytryptamine; 5-HT) has been described as a candidate neurotransmitter in the gustatory system and recent studies show that type III taste receptor cells release 5-HT in response to various taste stimuli. In the present study, we demonstrate that a subset of gustatory sensory neurons express functional

  3. Enhanced 5-hydroxytryptamine (5-HT) release from vascular adrenergic nerves in spontaneously hypertensive rats

    SciTech Connect

    Kawasaki, H.; Urabe, M.; Takasaki, K.

    1986-03-01

    The release of 5-HT from vascular adrenergic nerves was compared between normotensive Wistar Kyoto rats (WKY) and SHR. The mesenteric vascular bed isolated from WKY and SHR was perfused with Krebs solution at a constant flow rate of 5 ml/min. Periarterial nerve stimulation (PNS) was delivered at 4 to 16 Hz for 30 sec. In the SHR preparation, the pressor response to PNS, previously decreased by prazonsin (50 nM), was greatly potentiated after treatment with 5-HT(1 ..mu..M) for 15 min and a frequency-dependent pressor response to PNS reappeared, whereas the 5-HT treatment did not alter the pressor response to exogenous norepinephrine (1 nmol) previously reduced by prazonsin. The potentiation of pressor response to PNS after 5-HT treatment was small in the WKY preparation. This potentiation in both WKY and SHR did not occur in the presence of ketanserin (10 nM). In the preparation labeled with (/sup 3/H)-5-HT, PNS (4-16 Hz) evoked a frequency-dependent increase of (/sup 3/H)-efflux, which was abolished by treatment with tetrodotoxin (100 nM) or 6-hydroxydopamine (50 mg/kg i.p. x 2) and in calcium-free Krebs solution. The PNS evoked-(/sup 3/H)-efflux was much greater in SHR than WKY. These results suggest that the release of 5-HT from vascular adrenergic nerves by PNS is enhanced in the SHR preparation.

  4. 5-HT1B receptors inhibit glutamate release from primary afferent terminals in rat medullary dorsal horn neurons

    PubMed Central

    Choi, I-S; Cho, J-H; An, C-H; Jung, J-K; Hur, Y-K; Choi, J-K; Jang, I-S

    2012-01-01

    BACKGROUND AND PURPOSE Although 5-HT1B receptors are expressed in trigeminal sensory neurons, it is still not known whether these receptors can modulate nociceptive transmission from primary afferents onto medullary dorsal horn neurons. EXPERIMENTAL APPROACH Primary afferent-evoked EPSCs were recorded from medullary dorsal horn neurons of rat horizontal brain stem slices using a conventional whole-cell patch clamp technique under a voltage-clamp condition. KEY RESULTS CP93129, a selective 5-HT1B receptor agonist, reversibly and concentration-dependently decreased the amplitude of glutamatergic EPSCs and increased the paired-pulse ratio. In addition, CP93129 reduced the frequency of spontaneous miniature EPSCs without affecting the current amplitude. The CP93129-induced inhibition of EPSCs was significantly occluded by GR55562, a 5-HT1B/1D receptor antagonist, but not LY310762, a 5-HT1D receptor antagonist. Sumatriptan, an anti-migraine drug, also decreased EPSC amplitude, and this effect was partially blocked by either GR55562 or LY310762. On the other hand, primary afferent-evoked EPSCs were mediated by the Ca2+ influx passing through both presynaptic N-type and P/Q-type Ca2+ channels. The CP93129-induced inhibition of EPSCs was significantly occluded by ω-conotoxin GVIA, an N-type Ca2+ channel blocker. CONCLUSIONS AND IMPLICATIONS The present results suggest that the activation of presynaptic 5-HT1B receptors reduces glutamate release from primary afferent terminals onto medullary dorsal horn neurons, and that 5-HT1B receptors could be, at the very least, a potential target for the treatment of pain from orofacial tissues. LINKED ARTICLE This article is commented on by Connor, pp. 353–355 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2012.01963.x PMID:22462474

  5. Physiologically identified 5-HT2-like receptors at the crayfish neuromuscular junction.

    PubMed

    Tabor, Jami N; Cooper, Robin L

    2002-04-01

    The model synaptic preparation of the crayfish opener neuromuscular junction is known to be responsive to exogenous application of 5-HT. The primary effect of 5-HT is an enhancement of vesicular release from the presynaptic motor nerve terminal. 5-HT is known to act through an IP(3) cascade which suggests the presence of a 5-HT(2) receptor subtype; however, this is based on vertebrate 5-HT receptor classification. We examined this possibility by using a selective agonist and two antagonists of the vertebrate 5-HT(2) receptor subtypes. The antagonist ketanserin and spiperone reduce the responsiveness of 5-HT in a dose-dependent manner. The broad 5-HT(2) receptor agonist, alpha-methyl-5-hydroxytryptamine (alpha-Me-5-HT) enhances synaptic transmission, in a concentration-dependent manner, but it is not as potent as 5-HT. These results support the notion that a 5-HT(2) receptor subtype is present presynaptically on the crayfish motor nerve terminals. By knowing the types of 5-HT receptors present on the presynaptic motor nerve terminals in this model synaptic preparation, a better understanding of the mechanisms of action of 5-HT on vesicular release will be forthcoming. PMID:11911865

  6. Downregulation of 5-HT7 Serotonin Receptors by the Atypical Antipsychotics Clozapine and Olanzapine. Role of Motifs in the C-Terminal Domain and Interaction with GASP-1.

    PubMed

    Manfra, Ornella; Van Craenenbroeck, Kathleen; Skieterska, Kamila; Frimurer, Thomas; Schwartz, Thue W; Levy, Finn Olav; Andressen, Kjetil Wessel

    2015-07-15

    The human 5-HT7 serotonin receptor, a G-protein-coupled receptor (GPCR), activates adenylyl cyclase constitutively and upon agonist activation. Biased ligands differentially activate 5-HT7 serotonin receptor desensitization, internalization and degradation in addition to G protein activation. We have previously found that the atypical antipsychotics clozapine and olanzapine inhibited G protein activation and, surprisingly, induced both internalization and lysosomal degradation of 5-HT7 receptors. Here, we aimed to determine the mechanism of clozapine- and olanzapine-mediated degradation of 5-HT7 receptors. In the C-terminus of the 5-HT7 receptor, we identified two YXXΦ motifs, LR residues, and a palmitoylated cysteine anchor as potential sites involved in receptor trafficking to lysosomes followed by receptor degradation. Mutating either of these sites inhibited clozapine- and olanzapine-mediated degradation of 5-HT7 receptors and also interfered with G protein activation. In addition, we tested whether receptor degradation was mediated by the GPCR-associated sorting protein-1 (GASP-1). We show that GASP-1 binds the 5-HT7 receptor and regulates the clozapine-mediated degradation. Mutations of the identified motifs and residues, located in or close to Helix-VIII of the 5-HT7 receptor, modified antipsychotic-stimulated binding of proteins (such as GASP-1), possibly by altering the flexibility of Helix-VIII, and also interfered with G protein activation. Taken together, our data demonstrate that binding of clozapine or olanzapine to the 5-HT7 receptor leads to antagonist-mediated lysosomal degradation by exposing key residues in the C-terminal tail that interact with GASP-1. PMID:25706089

  7. Serotonin type 1D receptors (5HT1DR) are differentially distributed in nerve fibres innervating craniofacial tissues

    PubMed Central

    Harriott, AM; Gold, MS

    2009-01-01

    We tested the hypothesis that the 5HT1DR, the primary antinociceptive target of triptans, is differentially distributed in tissues responsible for migraine pain. The density of 5HT1DR was quantified in tissues obtained from adult female rats with Western blot analysis. Receptor location was assessed with immunohistochemistry. The density of 5HT1DR was significantly greater in tissues known to produce migraine-like pain (i.e. circle of Willis and dura) than in structures in which triptans have no antinociceptive efficacy (i.e. temporalis muscle). 5HT1DR-like immunoreactivity was restricted to neuronal fibres, where it colocalized with calcitonin gene-related peptide and tyrosine hydroxylase immunoreactive fibres. These results are consistent with our hypothesis that the limited therapeutic profile of triptans could reflect its differential peripheral distribution and that the antinociceptive efficacy reflects inhibition of neuropeptide release from sensory afferents. An additional site of action at sympathetic efferents is also suggested. PMID:18557979

  8. WAY208466 inhibits glutamate release at hippocampal nerve terminals.

    PubMed

    Wang, Hue Yu; Lu, Cheng Wei; Lin, Tzu Yu; Kuo, Jinn Rung; Wang, Su Jane

    2016-06-15

    Evidence suggests that the glutamatergic system plays a crucial role in the pathophysiology and treatment of depression. This study investigates the effect of WAY208466, a 5-HT6 receptor agonist exhibiting an antidepressant effect, on glutamate release from rat hippocampal nerve terminals (synaptosomes). WAY208466 inhibited the Ca(2+)-dependent release of glutamate that was evoked by exposing the synaptosomes to the potassium channel blocker 4-aminopyridine, and the selective 5-HT6 receptor antagonist SB258585 blocked this phenomenon. The WAY208466-mediated inhibition of glutamate release was associated with a reduction of 4-aminopyridine-induced increase in the cytosolic free Ca(2+) concentration ([Ca(2+)]C) mediated via Cav2.2 (N-type) and Cav2.1 (P/Q-type) channels. WAY208466 did not alter the resting synaptosomal membrane potential or 4-aminopyridine-mediated depolarization; thus, the inhibition of the Ca(2+) influx could not be attributed to the decrease in synaptosomal excitability caused by 5-HT6 receptor activation. Furthermore, the effect of WAY208466 on 4-aminopyridine-evoked glutamate release was prevented by a Gi/Go-protein inhibitor pertussis toxin, adenylate cyclase inhibitor SQ22536, and a protein kinase A inhibitor H89. These results suggest that WAY208466 acts at the 5-HT6 receptors present in the hippocampal nerve terminals to suppress the Gi/Go-protein-coupled adenylate cyclase/protein kinase A cascade, which subsequently reduces the Ca(2+) influx via N- and P/Q-type Ca(2+) channels to inhibit the evoked glutamate release. This finding implicated a potential therapeutic role of 5-HT6 receptor agonist in the treatment of depression and other neurological diseases associated with glutamate excitotoxicity. PMID:27068148

  9. The mechanisms involved in the long-lasting neuroprotective effect of fluoxetine against MDMA (‘ecstasy')-induced degeneration of 5-HT nerve endings in rat brain

    PubMed Central

    Sanchez, V; Camarero, J; Esteban, B; Peter, M J; Green, A R; Colado, M I

    2001-01-01

    It has been reported that co-administration of fluoxetine with 3,4-methylenedioxymethamphetamine (MDMA, ‘ecstasy') prevents MDMA-induced degeneration of 5-HT nerve endings in rat brain. The mechanisms involved have now been investigated. MDMA (15 mg kg−1, i.p.) administration produced a neurotoxic loss of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in cortex, hippocampus and striatum and a reduction in cortical [3H]-paroxetine binding 7 days later. Fluoxetine (10 mg kg−1, i.p., ×2, 60 min apart) administered concurrently with MDMA or given 2 and 4 days earlier provided complete protection, and significant protection when given 7 days earlier. Fluvoxamine (15 mg kg−1, i.p., ×2, 60 min apart) only produced neuroprotection when administered concurrently. Fluoxetine (10 mg kg−1, ×2) markedly increased the KD and reduced the Bmax of cortical [3H]-paroxetine binding 2 and 4 days later. The Bmax was still decreased 7 days later, but the KD was unchanged. [3H]-Paroxetine binding characteristics were unchanged 24 h after fluvoxamine (15 mg kg−1, ×2). A significant cerebral concentration of fluoxetine plus norfluoxetine was detected over the 7 days following fluoxetine administration. The fluvoxamine concentration had decreased markedly by 24 h. Pretreatment with fluoxetine (10 mg kg−1, ×2) failed to alter cerebral MDMA accumulation compared to saline pretreated controls. Neither fluoxetine or fluvoxamine altered MDMA-induced acute hyperthermia. These data demonstrate that fluoxetine produces long-lasting protection against MDMA-induced neurodegeneration, an effect apparently related to the presence of the drug and its active metabolite inhibiting the 5-HT transporter. Fluoxetine does not alter the metabolism of MDMA or its rate of cerebral accumulation. PMID:11522596

  10. Role of central vagal 5-HT3 receptors in gastrointestinal physiology and pathophysiology

    PubMed Central

    Browning, Kirsteen N.

    2015-01-01

    Vagal neurocircuits are vitally important in the co-ordination and modulation of GI reflexes and homeostatic functions. 5-hydroxytryptamine (5-HT; serotonin) is critically important in the regulation of several of these autonomic gastrointestinal (GI) functions including motility, secretion and visceral sensitivity. While several 5-HT receptors are involved in these physiological responses, the ligand-gated 5-HT3 receptor appears intimately involved in gut-brain signaling, particularly via the afferent (sensory) vagus nerve. 5-HT is released from enterochromaffin cells in response to mechanical or chemical stimulation of the GI tract which leads to activation of 5-HT3 receptors on the terminals of vagal afferents. 5-HT3 receptors are also present on the soma of vagal afferent neurons, including GI vagal afferent neurons, where they can be activated by circulating 5-HT. The central terminals of vagal afferents also exhibit 5-HT3 receptors that function to increase glutamatergic synaptic transmission to second order neurons of the nucleus tractus solitarius within the brainstem. While activation of central brainstem 5-HT3 receptors modulates visceral functions, it is still unclear whether central vagal neurons, i.e., nucleus of the tractus solitarius (NTS) and dorsal motor nucleus of the vagus (DMV) neurons themselves also display functional 5-HT3 receptors. Thus, activation of 5-HT3 receptors may modulate the excitability and activity of gastrointestinal vagal afferents at multiple sites and may be involved in several physiological and pathophysiological conditions, including distention- and chemical-evoked vagal reflexes, nausea, and vomiting, as well as visceral hypersensitivity. PMID:26578870

  11. 5-HT3 Receptors

    PubMed Central

    Thompson, A. J.; Lummis, S. C. R.

    2009-01-01

    The 5-HT3 receptor is a member of the Cys-loop family of ligand-gated ion channels. These receptors are located in both the peripheral and central nervous systems, where functional receptors are constructed from five subunits. These subunits may be the same (homopentameric 5-HT3A receptors) or different (heteropentameric receptors, usually comprising of 5-HT3A and 5-HT3B receptor subunits), with the latter having a number of distinct properties. The 5-HT3 receptor binding site is comprised of six loops from two adjacent subunits, and critical ligand binding amino acids in these loops have been largely identified. There are a range of selective agonists and antagonists for these receptors and the pharmacophore is reasonably well understood. There are also a wide range of compounds that can modulate receptor activity. Studies have suggested many diverse potential disease targets that might be amenable to alleviation by 5-HT3 receptor selective compounds but to date only two applications have been fully realised in the clinic: the treatment of emesis and irritable-bowel syndrome. PMID:17073663

  12. Expression of 5-HT3 receptors and TTX resistant sodium channels (NaV1.8) on muscle nerve fibers in pain-free humans and patients with chronic myofascial temporomandibular disorders

    PubMed Central

    2014-01-01

    Background Previous studies have shown that 5-HT3-antagonists reduce muscle pain, but there are no studies that have investigated the expression of 5-HT3-receptors in human muscles. Also, tetrodotoxin resistant voltage gated sodium-channels (NaV) are involved in peripheral sensitization and found in trigeminal ganglion neurons innervating the rat masseter muscle. This study aimed to investigate the frequency of nerve fibers that express 5-HT3A-receptors alone and in combination with NaV1.8 sodium-channels in human muscles and to compare it between healthy pain-free men and women, the pain-free masseter and tibialis anterior muscles, and patients with myofascial temporomandibular disorders (TMD) and pain-free controls. Methods Three microbiopsies were obtained from the most bulky part of the tibialis and masseter muscles of seven and six healthy men and seven and six age-matched healthy women, respectively, while traditional open biopsies were obtained from the most painful spot of the masseter of five female patients and from a similar region of the masseter muscle of five healthy, age-matched women. The biopsies were processed by routine immunohistochemical methods. The biopsy sections were incubated with monoclonal antibodies against the specific axonal marker PGP 9.5, and polyclonal antibodies against the 5-HT3A-receptors and NaV1.8 sodium-channels. Results A similar percentage of nerve fibers in the healthy masseter (85.2%) and tibialis (88.7%) muscles expressed 5-HT3A-receptors. The expression of NaV1.8 by 5-HT3A positive nerve fibers associated with connective tissue was significantly higher than nerve fibers associated with myocytes (P < .001). In the patients, significantly more fibers per section were found with an average of 3.8 ± 3 fibers per section in the masseter muscle compared to 2.7 ± 0.2 in the healthy controls (P = .024). Further, the frequency of nerve fibers that co-expressed NaV1.8 and 5-HT3A receptors was significantly

  13. Ondansetron reverses anti-hypersensitivity from clonidine in rats following peripheral nerve injury: Role of γ-amino butyric acid in α2-adrenoceptor and 5-HT3 serotonin receptor analgesia

    PubMed Central

    Hayashida, Ken-ichiro; Kimura, Masafumi; Yoshizumi, Masaru; Hobo, Shotaro; Obata, Hideaki; Eisenach, James C.

    2012-01-01

    Introduction Monoaminergic pathways, impinging an α2-adrenoceptors and 5-HT3 serotonin receptors, modulate nociceptive transmission, but their mechanisms and interactions after neuropathic injury are unknown. Here we examine these interactions in rodents after nerve injury. Methods Male Sprague-Dawley rats following L5-L6 spinal nerve ligation (SNL) were used for either behavioral testing, in vivo microdialysis for γ-amino butyric acid (GABA) and acetylcholine release, or synaptosome preparation for GABA release. Results Intrathecal administration of the α2-adrenoceptor agonist (clonidine) and 5-HT3 receptor agonist (chlorophenylbiguanide) reduced hypersensitivity in SNL rats via GABA receptor-mediated mechanisms. Clonidine increased GABA and acetylcholine release in vivo in the spinal cord of SNL rats but not in normal rats. Clonidine-induced spinal GABA release in SNL rats was blocked by α2-adrenergic and nicotinic cholinergic antagonists. The 5-HT3 receptor antagonist ondansetron decreased and chlorophenylbiguanide increased spinal GABA release in both normal and SNL rats. In synaptosomes from the spinal dorsal horn of SNL rats, pre-synaptic GABA release was increased by nicotinic agonists and decreased by muscarinic and α2-adrenergic agonists. Spinally administered ondansetron significantly reduced clonidine-induced anti-hypersensitivity and spinal GABA release in SNL rats. Conclusion These results suggest that spinal GABA contributes to anti-hypersensitivity from intrathecal α2-adrenergic and 5-HT3 receptor agonists in the neuropathic pain state, that cholinergic neuroplasticity after nerve injury is critical for α2-adrenoceptor-mediated GABA release, and that blockade of spinal 5-HT3 receptors reduces α2-adrenoceptor-mediated anti-hypersensitivity via reducing total GABA release. PMID:22722575

  14. The effects of 5-HT on sensory, central and motor neurons driving the abdominal superficial flexor muscles in the crayfish.

    PubMed

    Strawn, J R; Neckameyer, W S; Cooper, R L

    2000-12-01

    Serotonin (5-HT) induces a variety of physiological and behavioral effects in crustaceans. However, the mechanisms employed by 5-HT to effect behavioral changes are not fully understood. Among the mechanisms by which these changes might occur are alterations in synaptic drive and efficacy of sensory, interneurons and motor neurons, as well as direct effects on muscles. We investigated these aspects with the use of a defined sensory-motor system, which is entirely contained within a single abdominal segment and consists of a 'cuticular sensory neurons segmental ganglia abdominal superficial flexor motor neurons-muscles' circuit. Our studies address the role of 5-HT in altering (1) the activity of motor neurons induced by sensory stimulation; (2) the inherent excitability of superficial flexor motor neurons; (3) transmitter release properties of the motor nerve terminal and (4) input resistance of the muscle. Using en passant recordings from the motor nerve, with and without sensory stimulation, and intracellular recordings from the muscle, we show that 5-HT enhances sensory drive and output from the ventral nerve cord resulting in an increase in the firing frequency of the motor neurons. Also, 5-HT increases transmitter release at the neuromuscular junction, and alters input resistance of the muscle fibers. PMID:11281271

  15. Functional characterization of 5-HT1D autoreceptors on the modulation of 5-HT release in guinea-pig mesencephalic raphe, hippocampus and frontal cortex.

    PubMed Central

    el Mansari, M.; Blier, P.

    1996-01-01

    1. The aims of the present study were (i) to characterize further the pharmacology of 5-HT1D autoreceptors modulating 5-HT release in guinea-pig mesencephalic raphe, hippocampus and frontal cortex; (ii) to determine whether 5-HT1D receptors in the mesencephalic raphe are located on 5-HT neurones; (iii) to determine whether 5-HT1D autoreceptors are coupled to G proteins; and (iv) to assess their sensitivity following long-term 5-HT reuptake blockade and inhibition of type-A monoamine oxidase. 2. In mesencephalic raphe, hippocampus and frontal cortex slices, the 5-HT1D/1B receptor agonist, sumatriptan and the 5-HT1 receptor agonist, 5-methoxytryptamine (5-MeOT) but not the 5-HT1B receptor agonist, CP93129, inhibited electrically the evoked release of [3H]-5-HT in a concentration-dependent manner. This effect was antagonized by the 5-HT1D/1B receptor antagonist GR127935 in the three structures, but not by the 5-HT1A receptor antagonist, (+)-WAY100635 in mesencephalic raphe slices. These results confirm the presence of functional 5-HT1D autoreceptors controlling 5-HT release within the mesencephalic raphe as well as in terminal regions. 3. The inhibitory effect of sumatriptan on K(+)-evoked release of [3H]-5-HT was not reduced by the addition of the Na+ channel blocker, tetrodotoxin to the superfusion medium, suggesting that these 5-HT1D receptors in the mesencephalic raphe are located on 5-HT neurones and may be considered autoreceptors. 4. The in vitro treatment with the alkylating agent N-ethylmaleimide (NEM) was used to determine whether these 5-HT1D autoreceptors are coupled to G proteins. The inhibitory effect of sumatriptan on electrically evoked release of [3H]-5-HT was attenuated in NEM-pretreated slices from mesencephalic raphe, hippocampus and frontal cortex, indicating that the 5-HT1D autoreceptors activated by sumatriptan are coupled to G proteins in these three structures. Taken together with our previous results, this suggests that, in addition to the 5

  16. Loading Drosophila nerve terminals with calcium indicators.

    PubMed

    Rossano, Adam J; Macleod, Gregory T

    2007-01-01

    Calcium plays many roles in the nervous system but none more impressive than as the trigger for neurotransmitter release, and none more profound than as the messenger essential for the synaptic plasticity that supports learning and memory. To further elucidate the molecular underpinnings of Ca(2+)-dependent synaptic mechanisms, a model system is required that is both genetically malleable and physiologically accessible. Drosophila melanogaster provides such a model. In this system, genetically-encoded fluorescent indicators are available to detect Ca(2+) changes in nerve terminals. However, these indicators have limited sensitivity to Ca(2+) and often show a non-linear response. Synthetic fluorescent indicators are better suited for measuring the rapid Ca(2+) changes associated with nerve activity. Here we demonstrate a technique for loading dextran-conjugated synthetic Ca(2+) indicators into live nerve terminals in Drosophila larvae. Particular emphasis is placed on those aspects of the protocol most critical to the technique's success, such as how to avoid static electricity discharges along the isolated nerves, maintaining the health of the preparation during extended loading periods, and ensuring axon survival by providing Ca(2+) to promote sealing of severed axon endings. Low affinity dextran-conjugated Ca(2+)-indicators, such as fluo-4 and rhod, are available which show a high signal-to-noise ratio while minimally disrupting presynaptic Ca(2+) dynamics. Dextran-conjugation helps prevent Ca(2+) indicators being sequestered into organelles such as mitochondria. The loading technique can be applied equally to larvae, embryos and adults. PMID:18997898

  17. Altered serotonin and dopamine metabolism in the CNS of serotonin 5-HT(1A) or 5-HT(1B) receptor knockout mice.

    PubMed

    Ase, A R; Reader, T A; Hen, R; Riad, M; Descarries, L

    2000-12-01

    Measurements of serotonin (5-HT), dopamine (DA), and noradrenaline, and of 5-HT and DA metabolites, were obtained by HPLC from 16 brain regions and the spinal cord of 5-HT(1A) or 5-HT(1B) knockout and wild-type mice of the 129/Sv strain. In 5-HT(1A) knockouts, 5-HT concentrations were unchanged throughout, but levels of 5-HT metabolites were higher than those of the wild type in dorsal/medial raphe nuclei, olfactory bulb, substantia nigra, and locus coeruleus. This was taken as an indication of increased 5-HT turnover, reflecting an augmented basal activity of midbrain raphe neurons and consequent increase in their somatodendritic and axon terminal release of 5-HT. It provided a likely explanation for the increased anxious-like behavior observed in 5-HT(1A) knockout mice. Concomitant increases in DA content and/or DA turnover were interpreted as the result of a disinhibition of DA, whereas increases in noradrenaline concentration in some territories of projection of the locus coeruleus could reflect a diminished activity of its neurons. In 5-HT(1B) knockouts, 5-HT concentrations were lower than those of the wild type in nucleus accumbens, locus coeruleus, spinal cord, and probably also several other territories of 5-HT innervation. A decrease in DA, associated with increased DA turnover, was measured in nucleus accumbens. These changes in 5-HT and DA metabolism were consistent with the increased aggressiveness and the supersensitivity to cocaine reported in 5-HT(1B) knockout mice. Thus, markedly different alterations in CNS monoamine metabolism may contribute to the opposite behavioral phenotypes of these two knockouts. PMID:11080193

  18. 5-HT1D receptor inhibits renal sympathetic neurotransmission by nitric oxide pathway in anesthetized rats.

    PubMed

    García-Pedraza, José-Ángel; García, Mónica; Martín, María-Luisa; Morán, Asunción

    2015-09-01

    Although serotonin has been shown to inhibit peripheral sympathetic outflow, serotonin regulation on renal sympathetic outflow has not yet been elucidated. This study investigated which 5-HT receptor subtypes are involved. Wistar rats were anesthetized (sodium pentobarbital; 60mg/kg, i.p.), and prepared for in situ autoperfused rat kidney, which allows continuous measurement of systemic blood pressure (SBP), heart rate (HR) and renal perfusion pressure (PP). Electrical stimulation of renal sympathetic nerves resulted in frequency-dependent increases in PP (18.3±1.0, 43.7±2.7 and 66.7±4.0 for 2, 4 and 6Hz, respectively), without altering SBP or HR. 5-HT, 5-carboxamidotryptamine (5-HT1/7 agonist) (0.00000125-0.1μg/kg each) or l-694,247 (5-HT1D agonist; 0.0125μg/kg) i.a. bolus inhibited vasopressor responses by renal nerve electrical stimulation, unlike i.a. bolus of agonists α-methyl-5-HT (5-HT2), 1-PBG (5-HT3), cisapride (5-HT4), AS-19 (5-HT7), CGS-12066B (5-HT1B) or 8-OH-DPAT (5-HT1A) (0.0125μg/kg each). The effect of l-694,247 did not affect the exogenous norepinephrine-induced vasoconstrictions, whereas was abolished by antagonist LY310762 (5-HT1D; 1mg/kg) or l-NAME (nitric oxide; 10mg/kg), but not by indomethacin (COX1/2; 2mg/kg) or glibenclamide (ATP-dependent K(+) channel; 20mg/kg). These results suggest that 5-HT mechanism-induced inhibition of rat vasopressor renal sympathetic outflow is mainly mediated by prejunctional 5-HT1D receptors via nitric oxide release. PMID:26003124

  19. Endogenous 5-HT outflow from chicken aorta by 5-HT uptake inhibitors and amphetamine derivatives

    PubMed Central

    DELGERMURUN, Dugar; ITO, Shigeo; OHTA, Toshio; YAMAGUCHI, Soichiro; OTSUGURO, Ken-ichi

    2015-01-01

    Chemoreceptor cells aggregating in clusters in the chicken thoracic aorta contain 5-hydroxytryptamine (5-HT) and have voltage-dependent ion channels and nicotinic acetylcholine receptors, which are characteristics typically associated with neurons. The aim of the present study was to investigate the effects of 5-HT uptake inhibitors, fluvoxamine, fluoxetine and clomipramine (CLM), and amphetamine derivatives, p-chloroamphetamine (PCA) and methamphetamine (MET), on endogenous 5-HT outflow from the isolated chick thoracic aorta in vitro. 5-HT was measured by using a HPLC system with electrochemical detection. The amphetamine derivatives and 5-HT uptake inhibitors caused concentration-dependent increases in endogenous 5-HT outflow. PCA was about ten times more effective in eliciting 5-HT outflow than MET. The 5-HT uptake inhibitors examined had similar potency for 5-HT outflow. PCA and CLM increased 5-HT outflow in a temperature-dependent manner. The outflow of 5-HT induced by PCA or 5-HT uptake inhibitors was independent of extracellular Ca2+ concentration. The 5-HT outflow induced by CLM, but not that by PCA, was dependent on the extracellular NaCl concentration. These results suggest that the 5-HT uptake system of 5-HT-containing chemoreceptor cells in the chicken thoracic aorta has characteristics similar to those of 5-HT-containing neurons in the mammalian central nervous system (CNS). PMID:26321443

  20. Endogenous 5-HT outflow from chicken aorta by 5-HT uptake inhibitors and amphetamine derivatives.

    PubMed

    Delgermurun, Dugar; Ito, Shigeo; Ohta, Toshio; Yamaguchi, Soichiro; Otsuguro, Ken-ichi

    2016-01-01

    Chemoreceptor cells aggregating in clusters in the chicken thoracic aorta contain 5-hydroxytryptamine (5-HT) and have voltage-dependent ion channels and nicotinic acetylcholine receptors, which are characteristics typically associated with neurons. The aim of the present study was to investigate the effects of 5-HT uptake inhibitors, fluvoxamine, fluoxetine and clomipramine (CLM), and amphetamine derivatives, p-chloroamphetamine (PCA) and methamphetamine (MET), on endogenous 5-HT outflow from the isolated chick thoracic aorta in vitro. 5-HT was measured by using a HPLC system with electrochemical detection. The amphetamine derivatives and 5-HT uptake inhibitors caused concentration-dependent increases in endogenous 5-HT outflow. PCA was about ten times more effective in eliciting 5-HT outflow than MET. The 5-HT uptake inhibitors examined had similar potency for 5-HT outflow. PCA and CLM increased 5-HT outflow in a temperature-dependent manner. The outflow of 5-HT induced by PCA or 5-HT uptake inhibitors was independent of extracellular Ca(2+) concentration. The 5-HT outflow induced by CLM, but not that by PCA, was dependent on the extracellular NaCl concentration. These results suggest that the 5-HT uptake system of 5-HT-containing chemoreceptor cells in the chicken thoracic aorta has characteristics similar to those of 5-HT-containing neurons in the mammalian central nervous system (CNS). PMID:26321443

  1. Towards novel 5-HT7versus 5-HT1A receptor ligands among LCAPs with cyclic amino acid amide fragments: design, synthesis, and antidepressant properties. Part II.

    PubMed

    Canale, Vittorio; Kurczab, Rafał; Partyka, Anna; Satała, Grzegorz; Witek, Jagna; Jastrzębska-Więsek, Magdalena; Pawłowski, Maciej; Bojarski, Andrzej J; Wesołowska, Anna; Zajdel, Paweł

    2015-03-01

    A 26-membered library of novel long-chain arylpiperazines, which contained primary and tertiary amides of cyclic amino acids (proline and 1,2,3,4-tetrahydroisoquinoline-3-carboxamide) in the terminal fragment was synthesized and biologically evaluated for binding affinity for 5-HT7 and 5-HT1A receptors. Docking studies confirmed advantages of Tic-amide over Pro-amide fragment for interaction with 5-HT7 receptors. Selected compounds 32 and 28, which behaved as 5-HT7Rs antagonist and 5-HT1A partial agonist, respectively, produced antidepressant-like effects in the forced swim test in mice after acute treatment in doses of 10 mg/kg (32) and 1.25 mg/kg (28). Compound 32 reduced immobility in a manner similar to the selective 5-HT7 antagonist SB-269970. PMID:25555143

  2. Critical role of 5-HT1A, 5-HT3, and 5-HT7 receptor subtypes in the initiation, generation, and propagation of the murine colonic migrating motor complex.

    PubMed

    Dickson, Eamonn J; Heredia, Dante J; Smith, Terence K

    2010-07-01

    The colonic migrating motor complex (CMMC) is necessary for fecal pellet propulsion in the murine colon. We have previously shown that 5-hydroxytryptamine (5-HT) released from enterochromaffin cells activates 5-HT(3) receptors on the mucosal processes of myenteric Dogiel type II neurons to initiate the events underlying the CMMC. Our aims were to further investigate the roles of 5-HT(1A), 5-HT(3), and 5-HT(7) receptor subtypes in generating and propagating the CMMC using intracellular microelectrodes or tension recordings from the circular muscle (CM) in preparations with and without the mucosa. Spontaneous CMMCs were recorded from the CM in isolated murine colons but not in preparations without the mucosa. In mucosaless preparations, ondansetron (3 microM; 5-HT(3) antagonist) plus hexamethonium (100 microM) completely blocked spontaneous inhibitory junction potentials, depolarized the CM. Ondansetron blocked the preceding hyperpolarization associated with a CMMC. Spontaneous CMMCs and CMMCs evoked by spritzing 5-HT (10 and 100 microM) or nerve stimulation in preparations without the mucosa were blocked by SB 258719 or SB 269970 (1-5 microM; 5-HT(7) antagonists). Both NAN-190 and (S)-WAY100135 (1-5 microM; 5-HT(1A) antagonists) blocked spontaneous CMMCs and neurally evoked CMMCs in preparations without the mucosa. Both NAN-190 and (S)-WAY100135 caused an atropine-sensitive depolarization of the CM. The precursor of 5-HT, 5-hydroxytryptophan (5-HTP) (10 microM), and 5-carboxamidotryptamine (5-CT) (5 microM; 5-HT(1/5/7) agonist) increased the frequency of spontaneous CMMCs. 5-HTP and 5-CT also induced CMMCs in preparations with and without the mucosa, which were blocked by SB 258719. 5-HT(1A), 5-HT(3), and 5-HT(7) receptors, most likely on Dogiel Type II/AH neurons, are important in initiating, generating, and propagating the CMMC. Tonic inhibition of the CM appears to be driven by ongoing activity in descending serotonergic interneurons; by activating 5-HT(7

  3. 5-HT6 receptors and Alzheimer's disease

    PubMed Central

    2013-01-01

    During the past 20 years, the 5-HT6 receptor has received increasing attention and become a promising target for improving cognition. Several studies with structurally different compounds have shown that not only antagonists but also 5-HT6 receptor agonists improve learning and memory in animal models. A large number of publications describing the development of ligands for this receptor have come to light, and it is now quite evident that 5-HT6 receptors have great pharmaceutical potential in terms of related patents. However, 5-HT6 receptor functionality is much more complex than initially defined. According to the existing data, different cellular pathways may be activated, depending on the drug being used. This article reviews preclinical and clinical evidence of the effects that 5-HT6 receptor compounds have on cognition. In addition, the biochemical and neurochemical mechanisms of action through which 5-HT6 receptor compounds can influence cognition will be described. Overall, several 5-HT6-targeted compounds can reasonably be regarded as powerful drug candidates for the treatment of Alzheimer's disease. PMID:23607787

  4. Differential interactions of dimethyltryptamine (DMT) with 5-HT1A and 5-HT2 receptors.

    PubMed

    Deliganis, A V; Pierce, P A; Peroutka, S J

    1991-06-01

    The interactions of the indolealkylamine N,N-dimethyltryptamine (DMT) with 5-hydroxytryptamine1A (5-HT1A) and 5-HT2 receptors in rat brain were analyzed using radioligand binding techniques and biochemical functional assays. The affinity of DMT for 5-HT1A sites labeled by [3H]-8-hydroxy-2-(di-n-propylamino)tetralin ([3H]-8-OH-DPAT) was decreased in the presence of 10(-4) M GTP, suggesting agonist activity of DMT at this receptor. Adenylate cyclase studies in rat hippocampi showed that DMT inhibited forskolin-stimulated cyclase activity, a 5-HT1A agonist effect. DMT displayed full agonist activity with an EC50 of 4 x 10(-6) M in the cyclase assay. In contrast to the agonist actions of DMT at 5-HT1A receptors, DMT appeared to have antagonistic properties at 5-HT2 receptors. The ability of DMT to compete for [3H]-ketanserin-labeled 5-HT2 receptors was not affected by the presence of 10(-4) M GTP, suggesting antagonist activity of DMT at 5-HT2 receptors. In addition, DMT antagonized 5-HT2-receptor-mediated phosphatidylinositol (PI) turnover in rat cortex at concentrations above 10(-7) M, with 70% of the 5-HT-induced PI response inhibited at 10(-4) M DMT. Micromolar concentrations of DMT produced a slight PI stimulation that was not blocked by the 5-HT2 antagonist ketanserin. These studies suggest that DMT has opposing actions on 5-HT receptor subtypes, displaying agonist activity at 5-HT1A receptors and antagonist activity at 5-HT2 receptors. PMID:1828347

  5. Effects of metformin on intestinal 5-hydroxytryptamine (5-HT) release and on 5-HT3 receptors.

    PubMed

    Cubeddu, L X; Bönisch, H; Göthert, M; Molderings, G; Racké, K; Ramadori, G; Miller, K J; Schwörer, H

    2000-01-01

    Nearly 30% of patients treated with metformin experience gastrointestinal side effects. Since release of 5-hydroxytryptamine (5-HT) from the intestine is associated with nausea, vomiting, and diarrhea, we examined whether metformin induces 5-HT release from the intestinal mucosa. In 40% of tissue biopsy specimens of human duodenal mucosa, metformin (1, 10, and 30 microM) caused an increase in 5-HT outflow by 35, 70, and 98%, respectively. Peak increases in 5-HT outflow were observed after 10-15 min exposure to metformin, returning to baseline levels after 25 min. Tetrodotoxin (1 microM) reduced by about 50% the metformin-evoked increase in 5-HT outflow (P<0.05). Metformin-evoked release was not affected by scopolamine + hexamethonium, propranolol, the 5-HT3 receptor antagonist dolasetron, naloxone, or the NK1 receptor antagonist L703606. In the presence of tetrodotoxin (1 microM), somatostatin (1 microM) further reduced metformin-induced 5-HT release by 15-20%. In view of the 5-HT releasing effects of selective 5-HT3 receptor agonists to which metformin (N-N-dimethylbiguanide) is structurally related, we investigated whether metformin directly interacts with 5-HT3 receptors. Receptor binding (inhibition of [3H]-GR65630 binding) and agonist effects (stimulation of [14C]-guanidinium influx) at 5-HT3 receptors were studied in murine neuroblastoma N1E-115 cells, which express functional 5-HT3 receptors. Metformin up to 0.3 mM failed to inhibit [3H]-GR65630 binding and to modify displacement of [3H]-GR65630 binding induced by 5-HT. 5-HT (3 microM) stimulated the influx of [14C]-guanidinium in intact N1E-115 cells. Metformin up to 1 mM failed to modify basal influx, 5-HT-induced influx, and 5-HT+ substance P-induced influx of [14C]-guanidinium. Our results indicate that metformin induces 5-HT3 receptor-independent release of 5-HT from human duodenal mucosa via neuronal and non-neuronal mechanisms. Part of the gastrointestinal side effects observed during treatment with

  6. Serotonin 5-HT4 receptors and forebrain cholinergic system: receptor expression in identified cell populations.

    PubMed

    Peñas-Cazorla, Raúl; Vilaró, M Teresa

    2015-11-01

    Activation of serotonin 5-HT4 receptors has pro-cognitive effects on memory performance. The proposed underlying neurochemical mechanism is the enhancement of acetylcholine release in frontal cortex and hippocampus elicited by 5-HT4 agonists. Although 5-HT4 receptors are present in brain areas related to cognition, e.g., hippocampus and cortex, the cellular localization of the receptors that might modulate acetylcholine release is unknown at present. We have analyzed, using dual label in situ hybridization, the cellular localization of 5-HT4 receptor mRNA in identified neuronal populations of the rat basal forebrain, which is the source of the cholinergic innervation to cortex and hippocampus. 5-HT4 receptor mRNA was visualized with isotopically labeled oligonucleotide probes, whereas cholinergic, glutamatergic, GABAergic and parvalbumin-synthesizing neurons were identified with digoxigenin-labeled oligonucleotide probes. 5-HT4 receptor mRNA was not detected in the basal forebrain cholinergic cell population. In contrast, basal forebrain GABAergic, parvalbumin synthesizing, and glutamatergic cells contained 5-HT4 receptor mRNA. Hippocampal and cortical glutamatergic neurons also express this receptor. These results indicate that 5-HT4 receptors are not synthesized by cholinergic cells, and thus would be absent from cholinergic terminals. In contrast, several non-cholinergic cell populations within the basal forebrain and its target hippocampal and cortical areas express these receptors and are thus likely to mediate the enhancement of acetylcholine release elicited by 5-HT4 agonists. PMID:25183542

  7. Cholecystokinin release mediated by 5-HT3 receptors in rat cerebral cortex and nucleus accumbens.

    PubMed Central

    Paudice, P.; Raiteri, M.

    1991-01-01

    1. The effects of 5-hydroxytryptamine (5-HT) on the release of cholexystokinin-like immunoreactivity (CCK-LI) were examined in synaptosomes prepared from rat cerebral cortex and nucleus accumbens and depolarized by superfusion with 15 mM KCl. 2. In both areas 5-HT, tested between 0.1 and 100 nM, increased the calcium-dependent, depolarization-evoked CCK-LI release in a concentration-related manner. The concentration-response curves did not differ significantly between the two brain areas (EC50: 0.4 +/- 0.045 nM and 0.48 +/- 0.053 nM, respectively, in cortical and n. accumbens synaptosomes; maximal effect: about 60% at 10 nM 5-HT). 3. The 5-HT1/5-HT2 receptor antagonist methiothepin (300 nM) did not affect the CCK-LI release elicited by 10 nM 5-HT. However, the effects of 10 nM 5-HT were antagonized in a concentration-dependent manner by the 5-HT3 receptor antagonists (3 alpha-tropanyl)-1H-indole-3-carboxylic acid ester (ICS 205-930; 0.1-100 nM; IC50: 3.56 +/- 0.42 nM in the cortex and 3.90 +/- 0.50 nM in the n. accumbens) and ondasetron (IC50: 8.15 +/- 0.73 nM in the cerebral cortex). 5-HT (10 nM) was also strongly antagonized by 100 nM 1 alpha H, 3 alpha 5 alpha H-tropan-3-yl-3,5-dichlorobenzoate (MDL 72222) another blocker of the 5-HT3 receptor. Moreover, the 5-HT3 receptor agonist 1-phenylbiguanide (tested in the cerebral cortex between 0.1 and 100 nM) enhanced CCK-LI release in a manner almost identical to that of 5-HT (EC50 = 0.64 +/- 0.071 nM). 4. It is concluded that 5-HT can act as a potent releaser of CCK-LI in rat cerebrocortex and nucleus accumbens through the activation of receptors of the 5-HT3 type situated on the CCK-releasing terminals. This interaction may provide a rationale for the clinical development of both 5-HT3 and CCK receptor antagonists as novel anxiolytic drugs. PMID:1933141

  8. Serotonin receptor diversity in the human colon: Expression of serotonin type 3 receptor subunits 5-HT3C, 5-HT3D, and 5-HT3E

    PubMed Central

    Kapeller, Johannes; Möller, Dorothee; Lasitschka, Felix; Autschbach, Frank; Hovius, Ruud; Rappold, Gudrun; Brüss, Michael; Gershon, Michael D.

    2011-01-01

    Since the first description of 5-HT3 receptors more than 50 years ago, there has been speculation about the molecular basis of their receptor heterogeneity. We have cloned the genes encoding novel 5-HT3 subunits 5-HT3C, 5-HT3D, and 5-HT3E and have shown that these subunits are able to form functional heteromeric receptors when coexpressed with the 5-HT3A subunit. However, whether these subunits are actually expressed in human tissue remained to be confirmed. In the current study, we performed immunocytochemistry to locate the 5-HT3A as well as the 5-HT3C, 5-HT3D, and 5-HT3E subunits within the human colon. Western blot analysis was used to confirm subunit expression, and RT-PCR was employed to detect transcripts encoding 5-HT3 receptor subunits in microdissected tissue samples. This investigation revealed, for the first time, that 5-HT3C, 5-HT3D, and 5-HT3E subunits are coexpressed with 5-HT3A in cell bodies of myenteric neurons. Furthermore, 5-HT3A and 5-HT3D were found to be expressed in submucosal plexus of the human large intestine. These data provide a strong basis for future studies of the roles that specific 5-HT3 receptor subtypes play in the function of the enteric and central nervous systems and the contribution that specific 5-HT3 receptors make to the pathophysiology of gastrointestinal disorders such as irritable bowel syndrome and dyspepsia. PMID:21192076

  9. Characterization of a ( sub 3 H)-5-hydroxtyryptamine binding site in rabbit caudate nucleus that differs from the 5-HT sub 1A , 5-HT sub 1B , 5-HT sub 1C and 5-HT sub 1D subtypes

    SciTech Connect

    Xiong, Wencheng; Nelson, D.L. )

    1989-01-01

    ({sup 3}H)5-HT binding sites were analyzed in membranes prepared from the rabbit caudate nucleus (CN). ({sup 3}H)5-HT labeled both 5-HT{sub 1A} and 5-HT{sub 1C} recognition sites, defined by nanomolar affinity for 8-OH-DPAT and mesulergine respectively; however, these represented only a fraction of total specific ({sup 3}H)5-HT binding. Saturation experiments of ({sup 3}H)5-HT binding in the presence of 100 nM 8-OH-DPAT and 100 nM mesulergine to block 5-HT{sub 1A} and 5-HT{sub 1C} sites revealed that non-5-HT{sub 1A}/non-5-HT{sub 1C} sites represented about 60% of the total 5-HT{sub 1} sites and that they exhibited saturable, high affinity, and homogeneous binding. The pharmacological profile of the non-5-HT{sub 1A}/non-5-HT{sub 1C} sites (designated 5-HT{sub 1R}) also differed from that of 5-HT{sub 1B} and 5-HT{sub 2} sites, but was similar to that of the 5-HT{sub 1D} site. However, significant differences existed between the 5-HT{sub 1D} and 5-HT{sub 1B} sites for their K{sub i} values for spiperone, spirilene, metergoline, and methiothepin. The study of modulatory agents also showed differences between the 5-HT{sub 1R} and 5-HT{sub 1D} sites. In addition, calcium enhanced the effects of GTP on the 5-HT{sub 1R} sites, whereas calcium inhibited the GTP effect on the 5-HT{sub 1D} sites.

  10. Design and synthesis of dual 5-HT1A and 5-HT7 receptor ligands.

    PubMed

    Ofori, Edward; Zhu, Xue Y; Etukala, Jagan R; Peprah, Kwakye; Jordan, Kamanski R; Adkins, Adia A; Bricker, Barbara A; Kang, Hye J; Huang, Xi-Ping; Roth, Bryan L; Ablordeppey, Seth Y

    2016-08-15

    5-HT1A and 5-HT7 receptors have been at the center of discussions recently due in part to their major role in the etiology of major central nervous system diseases such as depression, sleep disorders, and schizophrenia. As part of our search to identify dual targeting ligands for these receptors, we have carried out a systematic modification of a selective 5HT7 receptor ligand culminating in the identification of several dual 5-HT1A and 5-HT7 receptor ligands. Compound 16, a butyrophenone derivative of tetrahydroisoquinoline (THIQ), was identified as the most potent agent with low nanomolar binding affinities to both receptors. Interestingly, compound 16 also displayed moderate affinity to other clinically relevant dopamine receptors. Thus, it is anticipated that compound 16 may serve as a lead for further exploitation in our quest to identify new ligands with the potential to treat diseases of CNS origin. PMID:27312422

  11. Synthesis and structure-activity relationships of a new model of arylpiperazines. Part 7: Study of the influence of lipophilic factors at the terminal amide fragment on 5-HT(1A) affinity/selectivity.

    PubMed

    López-Rodríguez, María L; Ayala, David; Viso, Alma; Benhamú, Bellinda; de La Pradilla, Roberto Fernández; Zarza, Fernando; Ramos, José A

    2004-03-15

    The influence of lipophilic factors at the amide fragment of a new series of (+/-)-7a-alkyl-2-[4-(4-arylpiperazin-1-yl)butyl]-1,3-dioxoperhydropyrrolo[1,2-c]imidazoles 2 and of (+/-)-7a-alkyl-2-[(4-arylpiperazin-1-yl)methyl]-1,3-dioxoperhydropyrrolo[1,2-c]imidazoles 3 has been studied. Variations of logP have been carried out by introducing different hydrocarbonated substituents (R(1)) at the position 7a of the bicyclohydantoin, namely the non-pharmacophoric part. All the new compounds exhibit high potency for the 5-HT(1A) receptor; however, affinities for the alpha(1) receptor are high for compounds 2a-l while compounds 3a-f are selective over this adrenergic receptor. On the other hand, differences in logP do not notably affect the K(i) values for the above receptors. PMID:15018929

  12. Effects of the antidepressant fluoxetine on the subcellular localization of 5-HT1A receptors and SERT

    PubMed Central

    Descarries, Laurent; Riad, Mustaph

    2012-01-01

    Serotonin (5-HT) 5-HT1A autoreceptors (5-HT1AautoR) and the plasmalemmal 5-HT transporter (SERT) are key elements in the regulation of central 5-HT function and its responsiveness to antidepressant drugs. Previous immuno-electron microscopic studies in rats have demonstrated an internalization of 5-HT1AautoR upon acute administration of the selective agonist 8-OH-DPAT or the selective serotonin reuptake inhibitor antidepressant fluoxetine. Interestingly, it was subsequently shown in cats as well as in humans that this internalization is detectable by positron emission tomography (PET) imaging with the 5-HT1A radioligand [18F]MPPF. Further immunocytochemical studies also revealed that, after chronic fluoxetine treatment, the 5-HT1AautoR, although present in normal density on the plasma membrane of 5-HT cell bodies and dendrites, do not internalize when challenged with 8-OH-DPAT. Resensitization requires several weeks after discontinuation of the chronic fluoxetine treatment. In contrast, the SERT internalizes in both the cell bodies and axon terminals of 5-HT neurons after chronic but not acute fluoxetine treatment. Moreover, the total amount of SERT immunoreactivity is then reduced, suggesting that SERT is not only internalized, but also degraded in the course of the treatment. Ongoing and future investigations prompted by these finding are briefly outlined by way of conclusion. PMID:22826342

  13. Serotonin 5-HT1A receptors as targets for agents to treat psychiatric disorders: rationale and current status of research.

    PubMed

    Celada, Pau; Bortolozzi, Analía; Artigas, Francesc

    2013-09-01

    Psychiatric disorders represent a large economic burden in modern societies. However, pharmacological treatments are still far from optimal. Drugs used in the treatment of major depressive disorder (MDD) and anxiety disorders (selective serotonin [5-HT] reuptake inhibitors [SSRIs] and serotonin-noradrenaline reuptake inhibitors [SNRIs]) are pharmacological refinements of first-generation tricyclic drugs, discovered by serendipity, and show low efficacy and slowness of onset. Moreover, antipsychotic drugs are partly effective in positive symptoms of schizophrenia, yet they poorly treat negative symptoms and cognitive deficits. The present article reviews the neurobiological basis of 5-HT1A receptor (5-HT1A-R) function and the role of pre- and postsynaptic 5-HT1A-Rs in the treatment of MDD, anxiety and psychotic disorders. The activation of postsynaptic 5-HT1A-Rs in corticolimbic areas appears beneficial for the therapeutic action of antidepressant drugs. However, presynaptic 5-HT1A-Rs play a detrimental role in MDD, since individuals with high density or function of presynaptic 5-HT1A-Rs are more susceptible to mood disorders and suicide, and respond poorly to antidepressant drugs. Moreover, the indirect activation of presynaptic 5-HT1A-Rs by SSRIs/SNRIs reduces 5-HT neuron activity and terminal 5-HT release, thus opposing the elevation of extracellular 5-HT produced by blockade of the serotonin transporter (SERT) in the forebrain. Chronic antidepressant treatment desensitizes presynaptic 5-HT1A-Rs, thus reducing the effectiveness of the 5-HT1A autoreceptor-mediated negative feedback. The prevention of this process by the non-selective partial agonist pindolol accelerates clinical antidepressant effects. Two new antidepressant drugs, vilazodone (marketed in the USA) and vortioxetine (in development) incorporate partial 5-HT1A-R agonist properties with SERT blockade. Several studies with transgenic mice have also established the respective role of pre- and

  14. Constitutively Active 5-HT Receptors: An Explanation of How 5-HT Antagonists Inhibit Gut Motility in Species Where 5-HT is Not an Enteric Neurotransmitter?

    PubMed Central

    Spencer, Nick J.

    2015-01-01

    Antagonists of 5-Hydroxytryptamine (5-HT) receptors are well known to inhibit gastrointestinal (GI)-motility and transit in a variety of mammals, including humans. Originally, these observations had been interpreted by many investigators (including us) as evidence that endogenous 5-HT plays a major role in GI motility. This seemed a logical assumption. However, the story changed dramatically after recent studies revealed that 5-HT antagonists still blocked major GI motility patterns (peristalsis and colonic migrating motor complexes) in segments of intestine depleted of all 5-HT. Then, these results were further supported by Dr. Gershons' laboratory, which showed that genetic deletion of all genes that synthesizes 5-HT had minor, or no inhibitory effects on GI transit in vivo. If 5-HT was essential for GI motility patterns and transit, then one would expect major disruptions in motility and transit when 5-HT synthesis was genetically ablated. This does not occur. The inhibitory effects of 5-HT antagonists on GI motility clearly occur independently of any 5-HT in the gut. Evidence now suggests that 5-HT antagonists act on 5-HT receptors in the gut which are constitutively active, and don't require 5-HT for their activation. This would explain a long-standing mystery of how 5-HT antagonists inhibit gut motility in species like mice, rats, and humans where 5-HT is not an enteric neurotransmitter. Studies are now increasingly demonstrating that the presence of a neurochemical in enteric neurons does not mean they function as neurotransmitters. Caution should be exercised when interpreting any inhibitory effects of 5-HT antagonists on GI motility. PMID:26732863

  15. Neurexin is expressed on nerves, but not at nerve terminals, in the electric organ.

    PubMed

    Russell, A B; Carlson, S S

    1997-06-15

    Neurexins are highly variable transmembrane proteins hypothesized to be nerve terminal-specific cell adhesion molecules. As a test of the hypothesis that neurexin is restricted to the nerve terminal, we examined neurexins in the electric organ of the elasmobranch electric fish. Specific antibodies generated against the intracellular domain of electric fish neurexin were used in immunocytochemical and Western blot analyses of the electromotor neurons that innervate the electric organ. Our results indicate that neurexin is not expressed at electric organ nerve terminals, as expected by the neurexin hypothesis. Instead, neurexin is expressed by electromotor neurons and on myelinated axons. This neurexin has a molecular weight of 140 kDa, consistent with an alpha-neurexin. In addition, we find that perineurial cells of the electromotor nerve also express a neurexin. These cells surround bundles of axons to form a diffusion barrier and are thought to be a special form of fibroblast. The results of the study argue against a universal role for neurexins as nerve terminal-specific proteins but suggest that neurexins are involved in axon-Schwann cell and perineurial cell interactions. PMID:9169533

  16. The effect of opiates on the terminal nerve impulse and quantal secretion from visualized amphibian nerve terminals.

    PubMed Central

    Lavidis, N. A.

    1995-01-01

    1. Secretion of transmitter from amphibian motor nerve terminal release sites is intermittent, spatially non-uniform and varies considerably throughout the year and during development. The role of opioid receptors in modulating transmitter secretion from amphibian motor nerve terminals is evaluated in this study. 2. Dynorphin-A (24 microM) and morphine (500 microM) did not significantly change the shape of the nerve impulse or the consistency with which it was observed, but decreased evoked quantal secretion by more than 50%. These effects of dynorphin-A and morphine were largely reversed by naloxone (50 microM). 3. Dynorphin-A and morphine did not significantly change either the amplitude or the frequency of spontaneous quantal secretions. 4. There was a uniform decrease in evoked quantal secretion from release sites along terminal branches, irrespective of the quantal content value before drug treatment, indicating no difference in the susceptibility of proximal vs distal release sites to opiates. 5. Increasing the extracellular calcium concentration (0.3 to 0.4 mM) or trains of conditioning-test impulses (25 to 100 Hz) resulted in smaller dynorphin-A or morphine-induced decreases in evoked quantal secretion. 6. The decrease in evoked quantal secretion occurs as a result of a uniform decrease in the probability of quantal secretion from release sites without any affect on the propagation of the nerve terminal impulse. Low probability release sites become effectively silent. PMID:7582455

  17. Intrathecal 5-methoxy-N,N-dimethyltryptamine in mice modulates 5-HT1 and 5-HT3 receptors.

    PubMed

    Alhaider, A A; Hamon, M; Wilcox, G L

    1993-11-01

    The antinociceptive effects of intrathecally administered 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), a potent 5-HT receptor agonist, were studied in three behavioral tests in mice: the tail-flick test and the intrathecal substance P and N-methyl-D-aspartic acid (NMDA) assays. Intrathecal administration of 5-MeO-DMT (4.6-92 nmol/mouse) produced a significant prolongation of the tail-flick latency. This action was blocked by 5-HT3 and gamma-aminobutyric acidA (GABAA) receptor antagonists but not by 5-HT2, 5-HT1A, 5-HT1B or 5-HT1S receptor antagonists. Binding studies indicated that 5-MeO-DMT had very low affinity for 5-HT3 receptors. 5-MeO-DMT inhibited biting behavior while increasing scratching behavior induced by intrathecally administered substance P. The inhibition of biting behavior was antagonized by intrathecal co-administration of 5-HT1B and GABAA receptor antagonists while 5-HT1A, 5-HT1S, 5-HT2 and 5-HT3 receptor antagonists had no effect. 5-MeO-DMT-enhanced scratching behavior was inhibited by all the antagonists used except ketanserin and bicuculline, suggesting the involvement of 5-HT1A, 5-HT1B, 5-HT1S, 5-HT3 and GABAA receptors. NMDA-induced biting behavior was inhibited by 5-MeO-DMT pretreatment; this action was antagonized by 5-HT1B, 5-HT3 and GABAA receptor antagonists. The involvement of these receptors in 5-MeO-DMT action suggests that it may promote release of 5-HT (5-hydroxytryptamine, serotonin). PMID:7507056

  18. The 5-HT1-like receptors mediating inhibition of sympathetic vasopressor outflow in the pithed rat: operational correlation with the 5-HT1A, 5-HT1B and 5-HT1D subtypes

    PubMed Central

    Villalón, Carlos M; Centurión, David; Rabelo, Gonzalo; de Vries, Peter; Saxena, Pramod R; Sánchez-López, Araceli

    1998-01-01

    It has been suggested that the inhibition of sympathetically-induced vasopressor responses produced by 5-hydroxytryptamine (5-HT) in pithed rats is mediated by 5-HT1-like receptors. The present study has re-analysed this suggestion with regard to the classification schemes recently proposed by the NC-IUPHAR subcommittee on 5-HT receptors.Intravenous (i.v.) continuous infusions of 5-HT and the 5-HT1 receptor agonists, 8-OH-DPAT (5-HT1A), indorenate (5-HT1A), CP 93,129 (5-HT1B) and sumatriptan (5-HT1B/1D), resulted in a dose-dependent inhibition of sympathetically-induced vasopressor responses.The sympatho-inhibitory responses induced by 5-HT, 8-OH-DPAT, indorenate, CP 93,129 or sumatriptan were analysed before and after i.v. treatment with blocking doses of the putative 5-HT receptor antagonists, WAY 100635 (5-HT1A), cyanopindolol (5-HT1A/1B) or GR 127935 (5-HT1B/1D). Thus, after WAY 100635, the responses to 5-HT and indorenate, but not to 8-OH-DPAT, CP 93,129 and sumatriptan, were blocked. After cyanopindolol, the responses to 5-HT, indorenate and CP 93,129 were abolished, whilst those to 8-OH-DPAT and sumatriptan (except at the lowest frequency of stimulation) remained unaltered. In contrast, after GR 127935, the responses to 5-HT, CP 93,129 and sumatriptan, but not to 8-OH-DPAT and indorenate, were abolished.In additional experiments, the inhibition induced by 5-HT was not modified after 5-HT7 receptor blocking doses of mesulergine.The above results suggest that the 5-HT1-like receptors, which inhibit the sympathetic vasopressor outflow in pithed rats, display the pharmacological profile of the 5-HT1A, 5-HT1B and 5-HT1D, but not that of 5-HT7, receptors. PMID:9692787

  19. 5-HT4 and 5-HT2 receptors antagonistically influence gap junctional coupling between rat auricular myocytes.

    PubMed

    Derangeon, Mickaël; Bozon, Véronique; Defamie, Norah; Peineau, Nicolas; Bourmeyster, Nicolas; Sarrouilhe, Denis; Argibay, Jorge A; Hervé, Jean-Claude

    2010-01-01

    5-hydroxytryptamine-4 (5-HT(4)) receptors have been proposed to contribute to the generation of atrial fibrillation in human atrial myocytes, but it is unclear if these receptors are present in the hearts of small laboratory animals (e.g. rat). In this study, we examined presence and functionality of 5-HT(4) receptors in auricular myocytes of newborn rats and their possible involvement in regulation of gap junctional intercellular communication (GJIC, responsible for the cell-to-cell propagation of the cardiac excitation). Western-blotting assays showed that 5-HT(4) receptors were present and real-time RT-PCR analysis revealed that 5-HT(4b) was the predominant isoform. Serotonin (1 microM) significantly reduced cAMP concentration unless a selective 5-HT(4) inhibitor (GR113808 or ML10375, both 1 microM) was present. Serotonin also reduced the amplitude of L-type calcium currents and influenced the strength of GJIC without modifying the phosphorylation profiles of the different channel-forming proteins or connexins (Cxs), namely Cx40, Cx43 and Cx45. GJIC was markedly increased when serotonin exposure occurred in presence of a 5-HT(4) inhibitor but strongly reduced when 5-HT(2A) and 5-HT(2B) receptors were inhibited, showing that activation of these receptors antagonistically regulated GJIC. The serotoninergic response was completely abolished when 5-HT(4), 5-HT(2A) and 5-HT(2B) were simultaneously inhibited. A 24 h serotonin exposure strongly reduced Cx40 expression whereas Cx45 was less affected and Cx43 still less. In conclusion, this study revealed that 5-HT(4) (mainly 5-HT(4b)), 5-HT(2A) and 5-HT(2B) receptors coexisted in auricular myocytes of newborn rat, that 5-HT(4) activation reduced cAMP concentration, I(Ca)(L) and intercellular coupling whereas 5-HT(2A) or 5-HT(2B) activation conversely enhanced GJIC. PMID:19615378

  20. High trait aggression in men is associated with low 5-HT levels, as indexed by 5-HT4 receptor binding.

    PubMed

    da Cunha-Bang, Sofi; Mc Mahon, Brenda; Fisher, Patrick MacDonald; Jensen, Peter Steen; Svarer, Claus; Knudsen, Gitte Moos

    2016-04-01

    Impulsive aggression has commonly been associated with a dysfunction of the serotonin (5-HT) system: many, but not all, studies point to an inverse relationship between 5-HT and aggression. As cerebral 5-HT4 receptor (5-HT4R) binding has recently been recognized as a proxy for stable brain levels of 5-HT, we here test the hypothesis in healthy men and women that brain 5-HT levels, as indexed by cerebral 5-HT4R, are inversely correlated with trait aggression and impulsivity. Sixty-one individuals (47 men) underwent positron emission tomography scanning with the radioligand [(11)C]SB207145 for quantification of brain 5-HT4R binding. The Buss-Perry Aggression Questionnaire (BPAQ) and the Barratt Impulsiveness Scale were used for assessment of trait aggression and trait impulsivity. Among male subjects, there was a positive correlation between global 5-HT4R and BPAQ total score (P = 0.037) as well as BPAQ physical aggression (P = 0.025). No main effect of global 5-HT4R on trait aggression or impulsivity was found in the mixed gender sample, but there was evidence for sex interaction effects in the relationship between global 5-HT4R and BPAQ physical aggression. In conclusion we found that low cerebral 5-HT levels, as indexed by 5-HT4R binding were associated with high trait aggression in males, but not in females. PMID:26772668

  1. 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

  2. Serotonin (5-HT) and 5-HT2A receptor agonists suppress lipolysis in primary rat adipose cells.

    PubMed

    Hansson, Björn; Medina, Anya; Fryklund, Claes; Fex, Malin; Stenkula, Karin G

    2016-05-27

    Serotonin (5-HT) is a biogenic monoamine that functions both as a neurotransmitter and a circulating hormone. Recently, the metabolic effects of 5-HT have gained interest and peripheral 5-HT has been proposed to influence lipid metabolism in various ways. Here, we investigated the metabolic effects of 5-HT in isolated, primary rat adipose cells. Incubation with 5-HT suppressed β-adrenergically stimulated glycerol release and decreased phosphorylation of protein kinase A (PKA)-dependent substrates, hormone sensitive lipase (Ser563) and perilipin (Ser522). The inhibitory effect of 5-HT on lipolysis enhanced the anti-lipolytic effect of insulin, but sustained in the presence of phosphodiesterase inhibitors, OPC3911 and isobuthylmethylxanthine (IBMX). The relative expression of 5-HT1A, -2B and -4 receptor class family were significantly higher in adipose tissue compared to adipose cells, whereas 5-HT1D, -2A and -7 were highly expressed in isolated adipose cells. Similar to 5-HT, 5-HT2 receptor agonists reduced lipolysis while 5-HT1 receptor agonists rather decreased non-stimulated and insulin-stimulated glucose uptake. Together, these data provide evidence of a direct effect of 5-HT on adipose cells, where 5-HT suppresses lipolysis and glucose uptake, which could contribute to altered systemic lipid- and glucose metabolism. PMID:27109474

  3. Circadian 5-HT production regulated by adrenergic signaling

    PubMed Central

    Sun, Xing; Deng, Jie; Liu, Tiecheng; Borjigin, Jimo

    2002-01-01

    Using on-line microdialysis, we have characterized in vivo dynamics of pineal 5-hydroxytryptamine (5-HT; serotonin) release. Daily pineal 5-HT output is triphasic: (i) 5-HT levels are constant and high during the day; (ii) early in the night, there is a novel sharp rise in 5-HT synthesis and release, which precedes the nocturnal rise in melatonin synthesis; and (iii) late in the night, levels are low. This triphasic 5-HT production persists in constant darkness and is influenced strongly by intrusion of light at night. We demonstrate that both diurnal 5-HT synthesis and 5-HT release are activated by sympathetic innervation from the superior cervical ganglion and show that these processes are controlled by distinct receptors. The increase in 5-HT synthesis is controlled by β-adrenergic receptors, whereas the increase in 5-HT release is mediated by α-adrenergic signaling. On the other hand, the marked decrease in 5-HT content and release late at night is a passive process, influenced by the extent of melatonin synthesis. In the absence of melatonin synthesis, the late-night decline in 5-HT release is prevented, reaching levels roughly twice as high as that of the day value. In summary, our results demonstrate that 5-HT levels display marked circadian rhythms that depend on adrenergic signaling. PMID:11917109

  4. Aryl biphenyl-3-ylmethylpiperazines as 5-HT7 receptor antagonists.

    PubMed

    Kim, Jeeyeon; Kim, Youngjae; Tae, Jinsung; Yeom, Miyoung; Moon, Bongjin; Huang, Xi-Ping; Roth, Bryan L; Lee, Kangho; Rhim, Hyewhon; Choo, Il Han; Chong, Youhoon; Keum, Gyochang; Nam, Ghilsoo; Choo, Hyunah

    2013-11-01

    The 5-HT7 receptor (5-HT7 R) is a promising therapeutic target for the treatment of depression and neuropathic pain. The 5-HT7 R antagonist SB-269970 exhibited antidepressant-like activity, whereas systemic administration of the 5-HT7 R agonist AS-19 significantly inhibited mechanical hypersensitivity and thermal hyperalgesia. In our efforts to discover selective 5-HT7 R antagonists or agonists, aryl biphenyl-3-ylmethylpiperazines were designed, synthesized, and biologically evaluated against the 5-HT7 R. Among the synthesized compounds, 1-([2'-methoxy-(1,1'-biphenyl)-3-yl]methyl)-4-(2-methoxyphenyl)piperazine (28) was the best binder to the 5-HT7 R (pKi =7.83), and its antagonistic property was confirmed by functional assays. The selectivity profile of compound 28 was also recorded for the 5-HT7 R over other serotonin receptor subtypes, such as 5-HT1 R, 5-HT2 R, 5-HT3 R, and 5-HT6 R. In a molecular modeling study, the 2-methoxyphenyl moiety attached to the piperazine ring of compound 28 was proposed to be essential for the antagonistic function. PMID:24039134

  5. Synergism Between a Serotonin 5-HT2A Receptor (5-HT2AR) Antagonist and 5-HT2CR Agonist Suggests New Pharmacotherapeutics for Cocaine Addiction

    PubMed Central

    2012-01-01

    Relapse to cocaine dependence, even after extended abstinence, involves a number of liability factors including impulsivity (predisposition toward rapid, unplanned reactions to stimuli without regard to negative consequences) and cue reactivity (sensitivity to cues associated with cocaine-taking which can promote cocaine-seeking). These factors have been mechanistically linked to serotonin (5-hydroxytryptamine, 5-HT) signaling through the 5-HT2A receptor (5-HT2AR) and 5-HT2CR; either a selective 5-HT2AR antagonist or a 5-HT2CR agonist suppresses impulsivity and cocaine-seeking in preclinical models. We conducted proof-of-concept analyses to evaluate whether a combination of 5-HT2AR antagonist plus 5-HT2CR agonist would have synergistic effects over these liability factors for relapse as measured in a 1-choice serial reaction time task and cocaine self-administration/reinstatement assay. Combined administration of a dose of the selective 5-HT2AR antagonist M100907 plus the 5-HT2CR agonist WAY163909, each ineffective alone, synergistically suppressed cocaine-induced hyperactivity, inherent and cocaine-evoked impulsive action, as well as cue- and cocaine-primed reinstatement of cocaine-seeking behavior. The identification of synergism between a 5-HT2AR antagonist plus a 5-HT2CR agonist to attenuate these factors important in relapse indicates the promise of a bifunctional ligand as an anti-addiction pharmacotherapeutic, setting the stage to develop new ligands with improved efficacy, potency, selectivity, and in vivo profiles over the individual molecules. PMID:23336050

  6. Synergism between a serotonin 5-HT2A receptor (5-HT2AR) antagonist and 5-HT2CR agonist suggests new pharmacotherapeutics for cocaine addiction.

    PubMed

    Cunningham, Kathryn A; Anastasio, Noelle C; Fox, Robert G; Stutz, Sonja J; Bubar, Marcy J; Swinford, Sarah E; Watson, Cheryl S; Gilbertson, Scott R; Rice, Kenner C; Rosenzweig-Lipson, Sharon; Moeller, F Gerard

    2013-01-16

    Relapse to cocaine dependence, even after extended abstinence, involves a number of liability factors including impulsivity (predisposition toward rapid, unplanned reactions to stimuli without regard to negative consequences) and cue reactivity (sensitivity to cues associated with cocaine-taking which can promote cocaine-seeking). These factors have been mechanistically linked to serotonin (5-hydroxytryptamine, 5-HT) signaling through the 5-HT(2A) receptor (5-HT(2A)R) and 5-HT(2C)R; either a selective 5-HT(2A)R antagonist or a 5-HT(2C)R agonist suppresses impulsivity and cocaine-seeking in preclinical models. We conducted proof-of-concept analyses to evaluate whether a combination of 5-HT(2A)R antagonist plus 5-HT(2C)R agonist would have synergistic effects over these liability factors for relapse as measured in a 1-choice serial reaction time task and cocaine self-administration/reinstatement assay. Combined administration of a dose of the selective 5-HT(2A)R antagonist M100907 plus the 5-HT(2C)R agonist WAY163909, each ineffective alone, synergistically suppressed cocaine-induced hyperactivity, inherent and cocaine-evoked impulsive action, as well as cue- and cocaine-primed reinstatement of cocaine-seeking behavior. The identification of synergism between a 5-HT(2A)R antagonist plus a 5-HT(2C)R agonist to attenuate these factors important in relapse indicates the promise of a bifunctional ligand as an anti-addiction pharmacotherapeutic, setting the stage to develop new ligands with improved efficacy, potency, selectivity, and in vivo profiles over the individual molecules. PMID:23336050

  7. Multiple cytosolic calcium buffers in posterior pituitary nerve terminals.

    PubMed

    McMahon, Shane M; Chang, Che-Wei; Jackson, Meyer B

    2016-03-01

    Cytosolic Ca(2+) buffers bind to a large fraction of Ca(2+) as it enters a cell, shaping Ca(2+) signals both spatially and temporally. In this way, cytosolic Ca(2+) buffers regulate excitation-secretion coupling and short-term plasticity of release. The posterior pituitary is composed of peptidergic nerve terminals, which release oxytocin and vasopressin in response to Ca(2+) entry. Secretion of these hormones exhibits a complex dependence on the frequency and pattern of electrical activity, and the role of cytosolic Ca(2+) buffers in controlling pituitary Ca(2+) signaling is poorly understood. Here, cytosolic Ca(2+) buffers were studied with two-photon imaging in patch-clamped nerve terminals of the rat posterior pituitary. Fluorescence of the Ca(2+) indicator fluo-8 revealed stepwise increases in free Ca(2+) after a series of brief depolarizing pulses in rapid succession. These Ca(2+) increments grew larger as free Ca(2+) rose to saturate the cytosolic buffers and reduce the availability of Ca(2+) binding sites. These titration data revealed two endogenous buffers. All nerve terminals contained a buffer with a Kd of 1.5-4.7 µM, and approximately half contained an additional higher-affinity buffer with a Kd of 340 nM. Western blots identified calretinin and calbindin D28K in the posterior pituitary, and their in vitro binding properties correspond well with our fluorometric analysis. The high-affinity buffer washed out, but at a rate much slower than expected from diffusion; washout of the low-affinity buffer could not be detected. This work has revealed the functional impact of cytosolic Ca(2+) buffers in situ in nerve terminals at a new level of detail. The saturation of these cytosolic buffers will amplify Ca(2+) signals and may contribute to use-dependent facilitation of release. A difference in the buffer compositions of oxytocin and vasopressin nerve terminals could contribute to the differences in release plasticity of these two hormones. PMID:26880753

  8. The 5-HT3B subunit affects high-potency inhibition of 5-HT3 receptors by morphine

    PubMed Central

    Baptista-Hon, Daniel T; Deeb, Tarek Z; Othman, Nidaa A; Sharp, Douglas; Hales, Tim G

    2012-01-01

    BACKGROUND AND PURPOSE Morphine is an antagonist at 5-HT3A receptors. 5-HT3 and opioid receptors are expressed in many of the same neuronal pathways where they modulate gut motility, pain and reinforcement. There is increasing interest in the 5-HT3B subunit, which confers altered pharmacology to 5-HT3 receptors. We investigated the mechanisms of inhibition by morphine of 5-HT3 receptors and the influence of the 5-HT3B subunit. EXPERIMENTAL APPROACH 5-HT-evoked currents were recorded from voltage-clamped HEK293 cells expressing human 5-HT3A subunits alone or in combination with 5-HT3B subunits. The affinity of morphine for the orthosteric site of 5-HT3A or 5-HT3AB receptors was assessed using radioligand binding with the antagonist [3H]GR65630. KEY RESULTS When pre-applied, morphine potently inhibited 5-HT-evoked currents mediated by 5-HT3A receptors. The 5-HT3B subunit reduced the potency of morphine fourfold and increased the rates of inhibition and recovery. Inhibition by pre-applied morphine was insurmountable by 5-HT, was voltage-independent and occurred through a site outside the second membrane-spanning domain. When applied simultaneously with 5-HT, morphine caused a lower potency, surmountable inhibition of 5-HT3A and 5-HT3AB receptors. Morphine also fully displaced [3H]GR65630 from 5-HT3A and 5-HT3AB receptors with similar potency. CONCLUSIONS AND IMPLICATIONS These findings suggest that morphine has two sites of action, a low-affinity, competitive site and a high-affinity, non-competitive site that is not available when the channel is activated. The affinity of morphine for the latter is reduced by the 5-HT3B subunit. Our results reveal that morphine causes a high-affinity, insurmountable and subunit-dependent inhibition of human 5-HT3 receptors. PMID:21740409

  9. 5-HT2A and 5-HT2C receptors as hypothalamic targets of developmental programming in male rats.

    PubMed

    Martin-Gronert, Malgorzata S; Stocker, Claire J; Wargent, Edward T; Cripps, Roselle L; Garfield, Alastair S; Jovanovic, Zorica; D'Agostino, Giuseppe; Yeo, Giles S H; Cawthorne, Michael A; Arch, Jonathan R S; Heisler, Lora K; Ozanne, Susan E

    2016-04-01

    Although obesity is a global epidemic, the physiological mechanisms involved are not well understood. Recent advances reveal that susceptibility to obesity can be programmed by maternal and neonatal nutrition. Specifically, a maternal low-protein diet during pregnancy causes decreased intrauterine growth, rapid postnatal catch-up growth and an increased risk for diet-induced obesity. Given that the synthesis of the neurotransmitter 5-hydroxytryptamine (5-HT) is nutritionally regulated and 5-HT is a trophic factor, we hypothesised that maternal diet influences fetal 5-HT exposure, which then influences development of the central appetite network and the subsequent efficacy of 5-HT to control energy balance in later life. Consistent with our hypothesis, pregnant rats fed a low-protein diet exhibited elevated serum levels of 5-HT, which was also evident in the placenta and fetal brains at embryonic day 16.5. This increase was associated with reduced levels of 5-HT2CR, the primary 5-HT receptor influencing appetite, in the fetal, neonatal and adult hypothalamus. As expected, a reduction of 5-HT2CR was associated with impaired sensitivity to 5-HT-mediated appetite suppression in adulthood. 5-HT primarily achieves effects on appetite by 5-HT2CR stimulation of pro-opiomelanocortin (POMC) peptides within the arcuate nucleus of the hypothalamus (ARC). We show that 5-HT2ARs are also anatomically positioned to influence the activity of ARC POMC neurons and that mRNA encoding 5-HT2AR is increased in the hypothalamus ofin uterogrowth-restricted offspring that underwent rapid postnatal catch-up growth. Furthermore, these animals at 3 months of age are more sensitive to appetite suppression induced by 5-HT2AR agonists. These findings not only reveal a 5-HT-mediated mechanism underlying the programming of susceptibility to obesity, but also provide a promising means to correct it, by treatment with a 5-HT2AR agonist. PMID:26769798

  10. 5-HT2A and 5-HT2C receptors as hypothalamic targets of developmental programming in male rats

    PubMed Central

    Martin-Gronert, Malgorzata S.; Stocker, Claire J.; Wargent, Edward T.; Cripps, Roselle L.; Garfield, Alastair S.; Jovanovic, Zorica; D'Agostino, Giuseppe; Yeo, Giles S. H.; Cawthorne, Michael A.; Arch, Jonathan R. S.; Heisler, Lora K.; Ozanne, Susan E.

    2016-01-01

    ABSTRACT Although obesity is a global epidemic, the physiological mechanisms involved are not well understood. Recent advances reveal that susceptibility to obesity can be programmed by maternal and neonatal nutrition. Specifically, a maternal low-protein diet during pregnancy causes decreased intrauterine growth, rapid postnatal catch-up growth and an increased risk for diet-induced obesity. Given that the synthesis of the neurotransmitter 5-hydroxytryptamine (5-HT) is nutritionally regulated and 5-HT is a trophic factor, we hypothesised that maternal diet influences fetal 5-HT exposure, which then influences development of the central appetite network and the subsequent efficacy of 5-HT to control energy balance in later life. Consistent with our hypothesis, pregnant rats fed a low-protein diet exhibited elevated serum levels of 5-HT, which was also evident in the placenta and fetal brains at embryonic day 16.5. This increase was associated with reduced levels of 5-HT2CR, the primary 5-HT receptor influencing appetite, in the fetal, neonatal and adult hypothalamus. As expected, a reduction of 5-HT2CR was associated with impaired sensitivity to 5-HT-mediated appetite suppression in adulthood. 5-HT primarily achieves effects on appetite by 5-HT2CR stimulation of pro-opiomelanocortin (POMC) peptides within the arcuate nucleus of the hypothalamus (ARC). We show that 5-HT2ARs are also anatomically positioned to influence the activity of ARC POMC neurons and that mRNA encoding 5-HT2AR is increased in the hypothalamus of in utero growth-restricted offspring that underwent rapid postnatal catch-up growth. Furthermore, these animals at 3 months of age are more sensitive to appetite suppression induced by 5-HT2AR agonists. These findings not only reveal a 5-HT-mediated mechanism underlying the programming of susceptibility to obesity, but also provide a promising means to correct it, by treatment with a 5-HT2AR agonist. PMID:26769798

  11. Arterial expression of 5-HT2B and 5-HT1B receptors during development of DOCA-salt hypertension

    PubMed Central

    Banes, Amy KL; Watts, Stephanie W

    2003-01-01

    Background 5-hydroxytryptamine (5-HT)2B and 5-HT1B receptors are upregulated in arteries from hypertensive DOCA-salt rats and directly by mineralocorticoids. We hypothesized that increased 5-HT2B and 5-HT1B receptor density and contractile function would precede increased blood pressure in DOCA-high salt rats. We performed DOCA-salt time course (days 1, 3, 5 and 7) studies using treatment groups of: DOCA-high salt, DOCA-low salt, Sham and Sham-high salt rats. Results In isolated-tissue baths, DOCA-high salt aorta contracted to the 5-HT2B receptor agonist BW723C86 on day 1; Sham aorta did not contract. The 5-HT1B receptor agonist CP93129 had no effect in arteries from any group. On days 3, 5 and 7 CP93129 and BW723C86 contracted DOCA-high salt and Sham-high salt aorta; Sham and DOCA-low salt aorta did not respond. Western analysis of DOCA-high salt aortic homogenates revealed increased 5-HT2B receptor levels by day 3; 5-HT1B receptor density was unchanged. Aortic homogenates from the other groups showed unchanged 5-HT2B and 5-HT1B receptor levels. Conclusion These data suggest that functional changes of 5-HT2B but not 5-HT1B receptors may play a role in the development of DOCA-salt hypertension. PMID:12974983

  12. Chronic activation of 5-HT4 receptors or blockade of 5-HT6 receptors improve memory performances.

    PubMed

    Quiedeville, Anne; Boulouard, Michel; Hamidouche, Katia; Da Silva Costa-Aze, Virginie; Nee, Gerald; Rochais, Christophe; Dallemagne, Patrick; Fabis, Frédéric; Freret, Thomas; Bouet, Valentine

    2015-10-15

    5-HT4 and 5-HT6 serotonergic receptors are located in brain structures involved in memory processes. Neurochemical and behavioural studies have demonstrated that acute activation of 5-HT4 receptors (5-HT4R) or blockade of 5-HT6 receptors (5-HT6R) improves memory. To evaluate the potential of these two receptors as targets in the treatment of memory disorders encountered in several situations (ageing, Alzheimer's disease, schizophrenia, etc.), it is necessary to assess whether their beneficial effects occur after chronic administration, and if such treatment induces adverse effects. The goal of this study was to assess the effects of chronic 5-HT4R or 5-HT6R modulation on recognition memory, and to observe the possible manifestation of side effects (modification of weight gain, locomotor activity or exploratory behaviour, etc.). Mice were treated for 14 days with a 5-HT4R partial agonist (RS-67333) or a 5-HT6R antagonist (SB-271046) at increasing doses. Memory performances, locomotor activity, and exploration were assessed. Both chronic 5-HT4R activation and 5-HT6R blockade extended memory traces in an object recognition test, and were not associated with any adverse effects in the parameters assessed. Chronic modulation of one or both of these receptors thus seems promising as a potential strategy for the treatment memory deficits. PMID:26187692

  13. Presynaptic modulation of 5-HT release in the rat septal region.

    PubMed

    Rutz, S; Riegert, C; Rothmaier, A K; Jackisch, R

    2007-05-11

    5-HT released from serotonergic axon terminals in the septal nuclei modulates the activity of septal output neurons (e.g. septohippocampal cholinergic neurons) bearing somatodendritic 5-HT receptors. Therefore, we studied the mechanisms involved in the presynaptic modulation of 5-HT release in the lateral (LS) and medial septum (MS), and the diagonal band of Broca (DB). HPLC analysis showed that tissue concentrations of noradrenaline, dopamine and 5-HT were highest in DB (DB>MS>LS). Slices prepared from LS, MS and DB regions were preincubated with [(3)H]5-HT, superfused in the presence of 6-nitro-2-(1-piperazinyl)-quinoline (6-nitroquipazine) and electrically stimulated up to three times (first electrical stimulation period (S(1)), S(2), S(3); 360 pulses, 3 Hz, 2 ms, 26-28 mA). In all septal regions the Ca(2+)-dependent and tetrodotoxin-sensitive electrically-evoked overflow of [(3)H] was inhibited by the 5-HT(1B) agonist CP-93,129 and the alpha(2)-adrenoceptor agonist 5-bromo-6-(2-imidazolin-2-ylamino)-quinoxaline tartrate (UK-14,304). Also the mu- and kappa-opioid receptor agonists (d-Ala(2), N-Me-Phe(4), glycinol(5))-enkephalin (DAMGO) and [trans-(1S,2S(-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl]-benzenacetamide hydro-chloride] (U-50,488H), respectively, acted inhibitory (although less potently), whereas the delta-opioid receptor agonist (d-Pen(2), d-Pen(5))-enkephalin (DPDPE), the dopamine D(2) receptor agonist quinpirole and the adenosine A(1) receptor agonist N(6)-cyclopentyladenosine were all ineffective; the GABA(B) receptor agonist baclofen had weak effects. All inhibitory effects of the agonists were antagonized by the corresponding antagonists (3-[3-(dimethylamino)propyl]-4-hydroxy-N-[4-(4-pyridinyl)phenyl]benzamide dihydrochloride (GR-55,562), idazoxan, naloxone, nor-binaltorphimine), which also significantly enhanced the evoked release of 5-HT at S(1). It is concluded that 5-HT release in septal nuclei of the rat is modulated by

  14. 5-HT spatial distribution imaging with multiphoton excitation of 5-HT correlative visible fluorescence in live cells

    NASA Astrophysics Data System (ADS)

    Zhang, Zhihong; Zeng, Shaoqun; Liu, Yafeng; Zhou, Wei; Chen, Tongsheng; Luo, Qingming

    2002-04-01

    The autofluorescence of 5-Hydroxytryptamine (5-HT) loaded rat mucosal mast cells (RBL-2H3 cells) is imaged with multiphoton excitation laser scanning microscope (MPELSM). 5-HT correlative visible fluorescence (Fco-vis) excited with 740-nm multiphoton excitation is observed in live cells for the first time, and the generating mechanism of 5-HT Fco-vis is studied. The spatial distribution of 5-HT in live cells is imaged at high spatial resolution in our experiment, which provides a new way to study the correlation between 5-HT spatial distribution and content, and the cellular functional state in live tissue or cells.

  15. The 5-HT1A agonists 8-OH-DPAT, buspirone and ipsapirone attenuate stress-induced anorexia in rats.

    PubMed

    Dourish, C T; Kennett, G A; Curzon, G

    1987-01-01

    The effects of 5-HT agonists and antagonists, benzodiazepine anxiolytics and tricyclic antidepressants on restraint stress-induced anorexia in rats were examined. The selective 5-HT(1A) agonists 8-hydroxy-2-(di- n-propylamino)tetralin (8-OH-DPAT), buspirone and ipsapirone, when injected 2 h after the termination of stress, attenuated stress-induced anor exia and body weight loss. The effects of 8-OH-DPAT on stress-induced anorexia were blocked by the 5-HT(1A) antagonist spiperone but not by the 5-HT(2) antagonist ketanserin. The preferential 5-HT(1B) agonists RU-24969 and quipazine induced anorexia in unstressed rats and tended to supplement the anorectic effects of stress. The benzodiazepines chlordiazepoxide and diazepam and the 5-HT antagonist cyproheptadine had no effect on stress-induced anorexia, when given (like the 5-HT(1A) agonists) 2 h after the stress. Similarly, daily injection for 2 weeks of the tricyclic antidepressants desipramine and sertraline had no beneficial effect. The data suggest that 8-OH-DPAT, buspirone and ipsapirone attenuate stress-induced anorexia in rodents by a hyperphagic action on 5-HT(1A) receptors. PMID:22158750

  16. The storage of endogenous noradrenaline in sympathetic nerve terminals

    PubMed Central

    Bisby, M. A.; Fillenz, Marianne

    1971-01-01

    1. The subcellular distribution of noradrenaline in sympathetic nerve terminals of rat vas deferens and cat spleen has been studied by cell fractionation methods combined with fluorescence and electronmicroscopic histochemical methods for noradrenaline. 2. Pinched-off axon varicosities (synaptosomes) were isolated and identified by fluorescence and electronmicroscopy in the mitochondrial pellet. 3. The proportion of large to small dense-cored vesicles in electronmicrographs of sympathetic nerve terminals varies in different organs. In rat vas deferens 4% and in cat spleen 20% are large vesicles. 4. Density gradients of rat vas deferens have a single low density peak of noradrenaline at 0·6 M sucrose, whereas those of cat spleen have an additional peak of noradrenaline at 1·1 M sucrose. 5. Small dense-cored vesicles were identified electronmicroscopically in the low density fractions and large dense-cored vesicles in the high density fractions from density gradients. 6. We conclude that both small and large dense-cored vesicles store noradrenaline. ImagesPlate 1Plate 2Plate 3 PMID:5579649

  17. Convergence of melatonin and serotonin (5-HT) signaling at MT2/5-HT2C receptor heteromers.

    PubMed

    Kamal, Maud; Gbahou, Florence; Guillaume, Jean-Luc; Daulat, Avais M; Benleulmi-Chaachoua, Abla; Luka, Marine; Chen, Patty; Kalbasi Anaraki, Dina; Baroncini, Marc; Mannoury la Cour, Clotilde; Millan, Mark J; Prevot, Vincent; Delagrange, Philippe; Jockers, Ralf

    2015-05-01

    Inasmuch as the neurohormone melatonin is synthetically derived from serotonin (5-HT), a close interrelationship between both has long been suspected. The present study reveals a hitherto unrecognized cross-talk mediated via physical association of melatonin MT2 and 5-HT2C receptors into functional heteromers. This is of particular interest in light of the "synergistic" melatonin agonist/5-HT2C antagonist profile of the novel antidepressant agomelatine. A suite of co-immunoprecipitation, bioluminescence resonance energy transfer, and pharmacological techniques was exploited to demonstrate formation of functional MT2 and 5-HT2C receptor heteromers both in transfected cells and in human cortex and hippocampus. MT2/5-HT2C heteromers amplified the 5-HT-mediated Gq/phospholipase C response and triggered melatonin-induced unidirectional transactivation of the 5-HT2C protomer of MT2/5-HT2C heteromers. Pharmacological studies revealed distinct functional properties for agomelatine, which shows "biased signaling." These observations demonstrate the existence of functionally unique MT2/5-HT2C heteromers and suggest that the antidepressant agomelatine has a distinctive profile at these sites potentially involved in its therapeutic effects on major depression and generalized anxiety disorder. Finally, MT2/5-HT2C heteromers provide a new strategy for the discovery of novel agents for the treatment of psychiatric disorders. PMID:25770211

  18. RU 24969-induced emesis in the cat - 5-HT1 sites other than 5-HT1A, 5-HT1B or 5-HT1C implicated

    NASA Technical Reports Server (NTRS)

    Lucot, James B.

    1990-01-01

    RU 24969 was administered s.c. to cats and found to elicit emesis with a maximally effective dose of 1.0 mg/kg 5-Methoxytryptamine was found to have lower efficacy and to produce a higher incidence of nonspecific effects while trifluoromethylphenylpiperizine (TFMPP) was devoid of emetic effects. The emesis elicited by 1.0 mg/kg of RU 24969 was not altered by pretreatment with phentolamine, haloperidol, yohimbine or (-)-propranolol, indicating that catecholamines played no role in this response. The emesis was prevented by metergoline and methysergide but not by ketanserin, cyproheptadine, mesulergine, ICS 205 930, methiothepin, trimethobenzamide or BMY 7378. An indirect argument is presented that implicates a role for 5-HT1D sites. This conclusion must remain tentative until drugs selective for this site are synthesized and tested. The emesis was also prevented by 8-hydroxy-2-(di-n-propylamine)tetralin (8-OH-DPAT), confirming that this drug has a general antiemetic effect in cats.

  19. Incubation of cocaine cue reactivity associates with neuroadaptations in the cortical serotonin (5-HT) 5-HT2C receptor (5-HT2CR) system.

    PubMed

    Swinford-Jackson, S E; Anastasio, N C; Fox, R G; Stutz, S J; Cunningham, K A

    2016-06-01

    Intensification of craving elicited by drug-associated cues during abstinence occurs over time in human cocaine users while elevation of cue reactivity ("incubation") is observed in rats exposed to extended forced abstinence from cocaine self-administration. Incubation in rodents has been linked to time-dependent neuronal plasticity in the medial prefrontal cortex (mPFC). We tested the hypothesis that incubation of cue reactivity during abstinence from cocaine self-administration is accompanied by lower potency and/or efficacy of the selective serotonin (5-HT) 5-HT2C​ receptor (5-HT2CR) agonist WAY163909 to suppress cue reactivity and a shift in the subcellular localization profile of the mPFC 5-HT2CR protein. We observed incubation of cue reactivity (measured as lever presses reinforced by the discrete cue complex) between Day 1 and Day 30 of forced abstinence from cocaine relative to sucrose self-administration. Pharmacological and biochemical analyses revealed that the potency of the selective 5-HT2CR agonist WAY163909 to suppress cue reactivity, the expression of synaptosomal 5-HT2CR protein in the mPFC, and the membrane to cytoplasmic expression of the 5-HT2CR in mPFC were lower on Day 30 vs. Day 1 of forced abstinence from cocaine self-administration. Incubation of cue reactivity assessed during forced abstinence from sucrose self-administration did not associate with 5-HT2CR protein expression in the mPFC. Collectively, these outcomes are the first indication that neuroadaptations in the 5-HT2CR system may contribute to incubation of cocaine cue reactivity. PMID:26926963

  20. Recombinant saphenous vein 5-HT1B receptors of the rabbit: comparative pharmacology with human 5-HT1B receptors.

    PubMed

    Wurch, T; Palmier, C; Colpaert, F C; Pauwels, P J

    1997-01-01

    1. The rabbit recombinant saphenous vein 5-hydroxytryptamine1B (r 5-HT1B) receptor stably transfected in rat C6-glial cells was characterized by measuring adenosine 3':5'-cyclic monophosphate (cycle AMP) formation upon exposure to various 5-HT receptor ligands. The effects of agonists and antagonists were compared with their effects determined previously at the human cloned 5-HT1B (h 5-HT1B) receptor under similar experimental conditions. 2. Intact C6-glial cells expressing rb HT1B receptors exhibited [3H]-5-carboxamidotryptamine (5-CT) binding sites with a Kd of 0.80 +/- 0.13 nM and a Bmax between 225 to 570 fmol mg-1 protein. The binding affinities of a series of 5-HT receptor ligands determined in a membrane preparation with [3H]-5-CT or [3H]-N-[4-methoxy-3-(4-methylpiperazin-1-yl)phenyl]-3-methyl-4-(-4 -pyridyl) benzamide (GR 125,743) were similar. With the exception of ketanserin, ligand affinities were comparable to those determined at the clones h 5-HT1B receptor site. 3. rb 5-HT1B receptors were negatively coupled to cyclic AMP formation upon stimulation with 5-HT agonists. Of the several 5-HT agonists tested, 5-CT was the most potent, the potency rank order being: 5-CT > 5-HT > zolmitriptan > naratriptan > rizatriptan > sumatriptan > R (+)-8-(hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). The maximal responses of these agonists were similar to those induced by 5-HT. The potency of these agonists showed a positive correlation (r2 = 0.87; P < 0.002) with their potency at the cloned h 5-HT1B receptor subtype. 4. 2'-Methyl-4-(5-methyl-[1,2,4]oxadiazol-3-yl)-biphenyl-4-carboxylic acid [4-methoxy-e-(4-methyl-piperazin-1-yl)-phenyl]-amide (GR 127,935), methiothepin and ketanserin each behaved as silent, competitive antagonists at rb 5HT1B receptors; pKB values were 8.41, 8.32 and 7.05, respectively when naratriptan was used as an agonist. These estimates accorded with their binding affinities and the potencies found on 5-HT and/or sumatriptan

  1. Substance P nerve terminals synapse upon negative chronotropic vagal motoneurons.

    PubMed

    Massari, V J; Johnson, T A; Llewellyn-Smith, I J; Gatti, P J

    1994-10-17

    Previous data indicate that there are anatomically segregated and physiologically independent parasympathetic ganglia on the surface of the heart which are capable of selective control of sino-atrial rate, atrio-ventricular conduction, and atrial contractility. We have injected a retrograde tracer into the cardiac ganglion which selectively regulates heart rate (the SA ganglion). Medullary tissues were processed for the histochemical visualization of retrogradely labeled neurons and for the immunohistochemical detection of the neurotransmitter substance P (SP) by dual labeling light and electron microscopic methods. Negative chronotropic retrogradely labeled cells were found in a long slender column in the ventrolateral nucleus ambiguous (NA-VL) which enlarged somewhat at the level of the area postrema. These cells were found bilaterally, but they were asymmetrically distributed. Half the animals showed a pronounced right side predominance in retrograde labeling, while the other half of the animals showed a lesser left side predominance. These observations may help to explain some of the controversy in the literature concerning the relative influence of the right and left vagus nerves on sinus rate. Ultrastructural examination demonstrated axo-somatic and axo-dendritic contacts between SP nerve terminals and retrogradely labeled negative chronotropic NA-VL neurons. SP immunoreactivity was often associated with large dense-core vesicles in terminals forming either symmetric or asymmetric synapses. These observations provide a potential anatomical substrate for the centrally mediated bradycardia elicited by microinjections of SP into the NA. SP immunoreactive terminals were also observed to make axo-somatic, axo-dendritic, and axo-axonic synapses with unlabeled neurons in NA-VL.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7529651

  2. Cellular resilience: 5-HT neurons in Tph2(-/-) mice retain normal firing behavior despite the lack of brain 5-HT.

    PubMed

    Montalbano, Alberto; Waider, Jonas; Barbieri, Mario; Baytas, Ozan; Lesch, Klaus-Peter; Corradetti, Renato; Mlinar, Boris

    2015-11-01

    Considerable evidence links dysfunction of serotonin (5-hydroxytryptamine, 5-HT) transmission to neurodevelopmental and psychiatric disorders characterized by compromised "social" cognition and emotion regulation. It is well established that the brain 5-HT system is under autoregulatory control by its principal transmitter 5-HT via its effects on activity and expression of 5-HT system-related proteins. To examine whether 5-HT itself also has a crucial role in the acquisition and maintenance of characteristic rhythmic firing of 5-HT neurons, we compared their intrinsic electrophysiological properties in mice lacking brain 5-HT, i.e. tryptophan hydroxylase-2 null mice (Tph2(-/-)) and their littermates, Tph2(+/-) and Tph2(+/+), by using whole-cell patch-clamp recordings in a brainstem slice preparation and single unit recording in anesthetized animals. We report that the active properties of dorsal raphe nucleus (DRN) 5-HT neurons in vivo (firing rate magnitude and variability; the presence of spike doublets) and in vitro (firing in response to depolarizing current pulses; action potential shape) as well as the resting membrane potential remained essentially unchanged across Tph2 genotypes. However, there were subtle differences in subthreshold properties, most notably, an approximately 25% higher input conductance in Tph2(-/-) mice compared with Tph2(+/-) and Tph2(+/+) littermates (p<0.0001). This difference may at least in part be a consequence of slightly bigger size of the DRN 5-HT neurons in Tph2(-/-) mice (approximately 10%, p<0.0001). Taken together, these findings show that 5-HT neurons acquire and maintain their signature firing properties independently of the presence of their principal neurotransmitter 5-HT, displaying an unexpected functional resilience to complete brain 5-HT deficiency. PMID:26409296

  3. Functional effects of the muscarinic receptor agonist, xanomeline, at 5-HT1 and 5-HT2 receptors

    PubMed Central

    Watson, J; Brough, S; Coldwell, M C; Gager, T; Ho, M; Hunter, A J; Jerman, J; Middlemiss, D N; Riley, G J; Brown, A M

    1998-01-01

    Xanomeline [3(3-hexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine] has been reported to act as a functionally selective muscarinic partial agonist with potential use in the treatment of Alzheimer's disease. This study examined the functional activity of xanomeline at 5-HT1 and 5-HT2 receptors in native tissue and/or human cloned receptors.Xanomeline had affinity for muscarinic receptors in rat cortical membranes where the ratio of the displacement affinity of [3H]-Quinuclidinyl benzilate vs that of [3H]-Oxotremorine-M was 16, indicative of partial agonist activity. Radioligand binding studies on human cloned receptors confirmed that xanomeline had substantial affinity for M1, M2, M3, M4, M5 receptors and also for 5-HT1 and 5-HT2 receptor subtypes.Carbachol and xanomeline stimulated basal [35S]-GTPγS binding in rat cortical membranes with micromolar affinity. The response to carbachol was attenuated by himbacine and pirenzepine with pA2 of 8.2, 6.9 respectively consistent with the response being mediated, predominantly, via M2 and M4 receptors. Xanomeline-induced stimulation of [35S]-GTPγS binding was inhibited by himbacine with an apparent pKb of 6.3, was not attenuated by pirenzepine up to 3 μM and was inhibited by the selective 5-HT1A antagonist WAY100635 with an apparent pKb of 9.4. These data suggest the agonist effect of xanomeline in this tissue is, in part, via 5-HT1A receptors. Similar studies on human cloned receptors confirmed that xanomeline is an agonist at human cloned 5-HT1A and 5-HT1B receptors.In studies using the fluorescent cytoplasmic Ca2+ indicator FLUO-3AM, xanomeline induced an increase in cytoplasmic Ca2+ concentration in SH-SY5Y cells expressing recombinant human 5-HT2C receptors. Atropine antagonized this response, consistent with mediation via endogenously-expressed muscarinic receptors. In the presence of atropine, xanomeline antagonized 5-HT-induced cytoplasmic changes in Ca2+ concentration in cells expressing h5

  4. Mast cell-cholinergic nerve interaction in mouse airways.

    PubMed

    Weigand, Letitia A; Myers, Allen C; Meeker, Sonya; Undem, Bradley J

    2009-07-01

    We addressed the mechanism by which antigen contracts trachea isolated from actively sensitized mice. Trachea were isolated from mice (C57BL/6J) that had been actively sensitized to ovalbumin (OVA). OVA (10 microg ml(-1)) caused histamine release (approximately total tissue content), and smooth muscle contraction that was rapid in onset and short-lived (t(1/2) < 1 min), reaching approximately 25% of the maximum tissue response. OVA contraction was mimicked by 5-HT, and responses to both OVA and 5-HT were sensitive to 10 microm-ketanserin (5-HT(2) receptor antagonist) and strongly inhibited by atropine (1microm). Epithelial denudation had no effect on the OVA-induced contraction. Histological assessment revealed about five mast cells/tracheal section the vast majority of which contained 5-HT. There were virtually no mast cells in the mast cell-deficient (sash -/-) mouse trachea. OVA failed to elicit histamine release or contractile responses in trachea isolated from sensitized mast cell-deficient (sash -/-) mice. Intracellular recordings of the membrane potential of parasympathetic neurons in mouse tracheal ganglia revealed a ketanserin-sensitive 5-HT-induced depolarization and similar depolarization in response to OVA challenge. These data support the hypothesis that antigen-induced contraction of mouse trachea is epithelium-independent, and requires mast cell-derived 5-HT to activate 5-HT(2) receptors on parasympathetic cholinergic neurons. This leads to acetylcholine release from nerve terminals, and airway smooth muscle contraction. PMID:19403609

  5. Strontium, barium, and manganese metabolism in isolated presynaptic nerve terminals

    SciTech Connect

    Rasgado-Flores, H.; Sanchez-Armass, S.; Blaustein, M.P.; Nachshen, D.A.

    1987-06-01

    To gain insight into the mechanisms by which the divalent cations Sr, Ba, and Mn affect neurotransmitter release from presynaptic nerve terminals, the authors examined the sequestration of these cations, ion comparison to Ca, by mitochondrial and nonmitochondrial organelles and the extrusion of these cations from isolated nerve terminals. Sequestration was studied in synaptosomes made leaky to small ions by treatment with saponin; efflux was examined in intact synaptosomes that were preloaded with the divalent cations by incubation in depolarizing (K rich) media. The selectivity sequence for ATP-dependent mitochondrial uptake that they observed was Mn>>Ca>Sr>>Ba, whereas that for the SER was Ca greater than or equal to Mn>Sr>>Ba. When synaptosomes that were preloaded with divalent cations were incubated in Na- and Ca-free media, there was little efflux of /sup 45/Ca, /sup 133/Ba, /sup 85/Sr, or /sup 54/Mn. When the incubation was carried out in media containing Na without Ca, there was substantial stimulation of Ca and Sr efflux, but only slight stimulation of Ba or Mn efflux. In Na-free media, the addition of 1 mM Ca promoted the efflux of all four divalent cations, probably via Ca-divalent cation exchange. In summary, the sequestration and extrusion data suggest that, with equal loads, Mn will be buffered to the greatest extent, whereas Ba will be least well buffered. These results may help to explain why Mn has a very long-lasting effect on transmitter release, while the effect of Sr is much briefer.

  6. The modulation by 5-HT of glutamatergic inputs from the raphe pallidus to rat hypoglossal motoneurones, in vitro

    PubMed Central

    Bouryi, Vitali A; Lewis, David I

    2003-01-01

    these projections as a result of activation of 5-HT1A and/or5-HT1B receptors located on presynaptic terminals. PMID:14555716

  7. Agonist properties of N,N-dimethyltryptamine at serotonin 5-HT2A and 5-HT2C receptors.

    PubMed

    Smith, R L; Canton, H; Barrett, R J; Sanders-Bush, E

    1998-11-01

    Extensive behavioral and biochemical evidence suggests an agonist role at the 5-HT2A receptor, and perhaps the 5-HT2C receptor, in the mechanism of action of hallucinogenic drugs. However the published in vitro pharmacological properties of N,N-dimethyltryptamine (DMT), an hallucinogenic tryptamine analog, are not consistent with this hypothesis. We, therefore, undertook an extensive investigation into the properties of DMT at 5-HT2A and 5-HT2C receptors. In fibroblasts transfected with the 5-HT2A receptor or the 5-HT2C receptor, DMT activated the major intracellular signaling pathway (phosphoinositide hydrolysis) to an extent comparable to that produced by serotonin. Because drug efficacy changes with receptor density and cellular microenvironment, we also examined the properties of DMT in native preparations using a behavioral and biochemical approach. Rats were trained to discriminate an antagonist ketanserin from an agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in a two-lever choice paradigm. Pharmacological studies showed that responding on the DOI and ketanserin lever reflected agonist and antagonist activity at 5-HT2A receptors, and hence, was a suitable model for evaluating the in vivo functional properties of DMT. Like other 5-HT2A receptor agonists, DMT substituted fully for DOI. Intact choroid plexus was used to evaluate the agonist properties at endogenous 5-HT2C receptors; DMT was a partial agonist at 5-HT2C receptors in this native preparation. Thus, we conclude that DMT behaves as an agonist at both 5-HT2A and 5-HT2A receptors. One difference was evident in that the 5-HT2C, but not the 5-HT2A, receptor showed a profound desensitization to DMT over time. This difference is interesting in light of the recent report that the hallucinogenic activity of DMT does not tolerate in humans and suggests the 5-HT2C receptor plays a less prominent role in the action of DMT. PMID:9768567

  8. Pharmacological Characterization of 5-HT1A Autoreceptor-Coupled GIRK Channels in Rat Dorsal Raphe 5-HT Neurons

    PubMed Central

    Montalbano, Alberto; Corradetti, Renato; Mlinar, Boris

    2015-01-01

    G protein-activated inwardly rectifying potassium (GIRK) channels in 5-HT neurons are assumed to be principal effectors of 5-hydroxytryptamine 1A (5-HT1A) autoreceptors, but their pharmacology, subunit composition and the role in regulation of 5-HT neuron activity have not been fully elucidated. We sought for a pharmacological tool for assessing the functional role of GIRK channels in 5-HT neurons by characterizing the effects of drugs known to block GIRK channels in the submicromolar range of concentrations. Whole-cell voltage-clamp recording in brainstem slices were used to determine concentration-response relationships for the selected GIRK channel blockers on 5-HT1A autoreceptor-activated inwardly rectifying K+ conductance in rat dorsal raphe 5-HT neurons. 5-HT1A autoreceptor-activated GIRK conductance was completely blocked by the nonselective inwardly rectifying potassium channels blocker Ba2+ (EC50 = 9.4 μM, full block with 100 μM) and by SCH23390 (EC50 = 1.95 μM, full block with 30 μM). GIRK-specific blocker tertiapin-Q blocked 5-HT1A autoreceptor-activated GIRK conductance with high potency (EC50 = 33.6 nM), but incompletely, i.e. ~16% of total conductance resulted to be tertiapin-Q-resistant. U73343 and SCH28080, reported to block GIRK channels with submicromolar EC50s, were essentially ineffective in 5-HT neurons. Our data show that inwardly rectifying K+ channels coupled to 5-HT1A autoreceptors display pharmacological properties generally expected for neuronal GIRK channels, but different from GIRK1-GIRK2 heteromers, the predominant form of brain GIRK channels. Distinct pharmacological properties of GIRK channels in 5-HT neurons should be explored for the development of new therapeutic agents for mood disorders. PMID:26460748

  9. 5-HT3 receptor-dependent modulation of respiratory burst frequency, regularity, and episodicity in isolated adult turtle brainstems

    PubMed Central

    Bartman, Michelle E.; Wilkerson, Julia E.R.; Johnson, Stephen M.

    2010-01-01

    To determine the role of central serotonin 5-HT3 receptors in respiratory motor control, respiratory motor bursts were recorded from hypoglossal (XII) nerve rootlets on isolated adult turtle brainstems during bath-application of 5-HT3 receptor agonists and antagonists. mCPBG and PBG (5-HT3 receptor agonists) acutely increased XII burst frequency and regularity, and decreased bursts/episode. Tropisetron and MDL72222 (5-HT3 antagonists) increased bursts/episode, suggesting endogenous 5-HT3 receptor activation modulates burst timing in vitro. Tropisetron blocked all mCPBG effects, and the PBG-induced reduction in bursts/episode. Tropisetron application following mCPBG application did not reverse the long-lasting (2 h) mCPBG-induced decrease in bursts/episode. We conclude that endogenous 5-HT3 receptor activation regulates respiratory frequency, regularity, and episodicity in turtles and may induce a form of respiratory plasticity with the long-lasting changes in respiratory regularity. PMID:20399913

  10. The action of SDZ 205,557 at 5-hydroxytryptamine (5-HT3 and 5-HT4) receptors.

    PubMed Central

    Eglen, R. M.; Alvarez, R.; Johnson, L. G.; Leung, E.; Wong, E. H.

    1993-01-01

    1. The interaction of the novel antagonist, SDZ 205,557 (2-methoxy-4-amino-5-chloro benzoic acid 2-(diethylamino) ethyl ester), at 5-HT3 and 5-HT4 receptors has been assessed in vitro and in vivo. 2. In guinea-pig hippocampus and in the presence of 0.4 microM 5-carboxamidotryptamine, 5-HT4-mediated stimulation of adenylyl cyclase was competitively antagonized by SDZ 205,557, with a pA2 value of 7.5, and a Schild slope of 0.81. In rat carbachol-contracted oesophagus, 5-HT4-receptor mediated relaxations were surmountably antagonized by SDZ 205,557 with a similar pA2 value (7.3). This value was agonist-independent with the exception of (R)-zacopride, against which a significantly lower value (6.4) was observed. 3. In functional studies of 5-HT3 receptors, SDZ 205,557 exhibited an affinity of 6.2 in guinea-pig ileum compared with 6.9 at binding sites labelled by [3H]-quipazine in NG108-15 cells. In the anaesthetized, vagotomized micropig, SDZ 205,557 produced only a transient blockade of 5-HT4-mediated tachycardia. This contrasted with tropisetron, which was active for over 60 min after administration. The half-lives for the inhibitory responses of SDZ 205,557 and tropisetron were 23 and 116 min, respectively. 4. In conclusion, SDZ 205,557 has similar affinity for 5-HT3 and 5-HT4 receptors. The apparent selectivity observed in guinea-pig is due to the atypical nature of the 5-HT3 receptor in this species. The short duration of action of this novel antagonist may complicate its use in vivo. SDZ 205,557 should, therefore, be used with appropriate caution in studies defining the 5-HT4 receptor. PMID:8448587

  11. The 5-HT(7) receptor in learning and memory.

    PubMed

    Roberts, Amanda J; Hedlund, Peter B

    2012-04-01

    The 5-HT(7) receptor is a more recently discovered G-protein-coupled receptor for serotonin. The functions and possible clinical relevance of this receptor are not yet fully understood. The present paper reviews to what extent the use of animal models of learning and memory and other techniques have implicated the 5-HT(7) receptor in such processes. The studies have used a combination of pharmacological and genetic tools targeting the receptor to evaluate effects on behavior and cellular mechanisms. In tests such as the Barnes maze, contextual fear conditioning and novel location recognition that involve spatial learning and memory there is a considerable amount of evidence supporting an involvement of the 5-HT(7) receptor. Supporting evidence has also been obtained in studies of mRNA expression and cellular signaling as well as in electrophysiological experiments. Especially interesting are the subtle but distinct effects observed in hippocampus-dependent models of place learning where impairments have been described in mice lacking the 5-HT(7) receptor or after administration of a selective antagonist. While more work is required, it appears that 5-HT(7) receptors are particularly important in allocentric representation processes. In instrumental learning tasks both procognitive effects and impairments in memory have been observed using pharmacological tools targeting the 5-HT(7) receptor. In conclusion, the use of pharmacological and genetic tools in animal studies of learning and memory suggest a potentially important role for the 5-HT(7) receptor in cognitive processes. PMID:21484935

  12. Impaired neurotransmission in ether lipid-deficient nerve terminals

    PubMed Central

    Brodde, Alexander; Teigler, Andre; Brugger, Britta; Lehmann, Wolf D.; Wieland, Felix; Berger, Johannes; Just, Wilhelm W.

    2016-01-01

    Isolated defects of ether lipid (EL) biosynthesis in humans cause rhizomelic chondrodysplasia punctata type 2 and type 3, serious peroxisomal disorders. Using a previously described mouse model [Rodemer, C., Thai, T.P., Brugger, B., Kaercher, T., Werner, H., Nave, K.A., Wieland, F., Gorgas, K., and Just, W.W. (2003) Inactivation of ether lipid biosynthesis causes male infertility, defects in eye development and optic nerve hypoplasia in mice. Hum. Mol. Genet., 12, 1881–1895], we investigated the effect of EL deficiency in isolated murine nerve terminals (synaptosomes) on the pre-synaptic release of the neurotransmitters (NTs) glutamate and acetylcholine. Both Ca2+-dependent exocytosis and Ca2+-independent efflux of the transmitters were affected. EL-deficient synaptosomes respire at a reduced rate and exhibit a lowered adenosin-5′-triphosphate/adenosine diphosphate (ATP/ADP) ratio. Consequently, ATP-driven processes, such as synaptic vesicle cycling and maintenance of Na+, K+ and Ca2+ homeostasis, might be disturbed. Analyzing reactive oxygen species in EL-deficient neural and non-neural tissues revealed that plasmalogens (PLs), the most abundant EL species in mammalian central nervous system, considerably contribute to the generation of the lipid peroxidation product malondialdehyde. Although EL-deficient tissue contains less lipid peroxidation products, fibroblasts lacking ELs are more susceptible to induced oxidative stress. In summary, these results suggest that due to the reduced energy state of EL-deficient tissue, the Ca2+-independent efflux of NTs increases while the Ca2+-dependent release declines. Furthermore, lack of PLs is mainly compensated for by an increase in the concentration of phosphatidylethanolamine and results in a significantly lowered level of lipid peroxidation products in the brain cortex and cerebellum. PMID:22403185

  13. Glossopharyngeal long-term facilitation requires serotonin 5-HT2 and NMDA receptors in rats

    PubMed Central

    Cao, Ying; Liu, Chun; Ling, Liming

    2009-01-01

    Although the glossopharyngeal nerve (IX) is mainly a sensory nerve, it innervates stylopharyngeus and some other pharyngeal muscles, whose excitations would likely improve upper airway patency since electrical IX stimulation increases pharyngeal airway size. As acute intermittent hypoxia (AIH) induces hypoglossal and genioglossal long-term facilitation (LTF), we hypothesized that AIH induces glossopharyngeal LTF, which requires serotonin 5-HT2 and NMDA receptors. Integrated IX activity was recorded in anesthetized, vagotomized, paralyzed and ventilated rats before, during and after 5 episodes of 3-min isocapnic 12% O2 with 3-min intervals of 50% O2. Either saline, ketanserin (5-HT2 antagonist, 2 mg/kg) or MK-801 (NMDA antagonist, 0.2 mg/kg) was (i.v.) injected 30–60 min before AIH. Both phasic and tonic IX activities were persistently increased (both P<0.05) after AIH in vehicle, but not ketanserin or MK-801, rats. Hypoxic glossopharyngeal responses were minimally changed after either drug. These data suggest that AIH induces both phasic and tonic glossopharyngeal LTF, which requires activation of 5-HT2 and NMDA receptors. PMID:20026287

  14. Insights into the complex influence of 5-HT signaling on thalamocortical axonal system development.

    PubMed

    van Kleef, Esmee S B; Gaspar, Patricia; Bonnin, Alexandre

    2012-05-01

    The topographic organization of the thalamocortical axons (TCAs) in the barrel field (BF) in the rodent primary somatosensory cortex results from a succession of temporally and spatially precise developmental events. Prenatally, growth and guidance mechanisms enable TCAs to navigate through the forebrain and reach the cortex. Postnatally, TCAs grow into the cortex, and the refinement of their terminal arborization pattern in layer IV creates barrel-like structures. The combined results of studies performed over the past 20 years clearly show that serotonin (5-hydroxytryptamine; 5-HT) signaling modulates these pre- and early postnatal developmental processes. In this context, 5-HT signaling can purposely be described as 'modulating' rather than 'controlling' because developmental alterations of 5-HT synthesis, uptake or degradation either have a dramatic, moderate or no effect at all on TCA pathway and BF formation. In this review we summarize and compare the outcomes of diverse pharmacological and genetic manipulations of 5-HT signaling on TCA pathway and BF formation, in an attempt to understand these discrepancies. PMID:22607002

  15. The effects of inorganic particles of lunar soil simulant on brain nerve terminals

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Krisanova, Natalia; Sivko, Roman; Borisov, Arseniy

    2012-07-01

    The health effects from lunar soil exposure are almost completely unknown, whereas the observations suggest that it can be deleterious to human physiology. It is important that the components of lunar soil may be internalized with lipid fractions of the lung epithelium, which in turn may help ions to overcome the blood-brain barrier. The study focused on the effects of JSC-1a Lunar Soil Simulant (LSS) (Orbital Technologies Corporation, Madison, USA) on rat brain nerve terminals (synaptosomes). We revealed that brain nerve terminals were not indifferent to the exposure to LSS inorganic particles. Using Zetasizer Nanosystem (Malvern Instruments) with helium-neon laser for dynamic light scattering (DLS), the synaptosomal size before and after the addition of LSS was measured and the binding of LSS inorganic particles to nerve terminals was demonstrated. Using potential-sensitive fluorescent dye rhodamine 6G, we showed that LSS inorganic particles did not influence the potential of the plasma membrane of nerve terminals. Acidification of synaptic vesicles of nerve terminals did not change in the presence of LSS inorganic particles that was revealed with pH-sensitive fluorescent dye acridine orange. However, LSS inorganic particles influenced accumulation of glutamate, the main excitatory neurotransmitter in the CNS, by nerve terminals. Thus, we report that inorganic particles of LSS influence accumulation of glutamate in brain nerve terminals and this fact may have harmful consequences to human physiology, in particular glutamate homeostasis in the mammalian CNS.

  16. Serotonin 5-HT1B receptor-mediated calcium influx-independent presynaptic inhibition of GABA release onto rat basal forebrain cholinergic neurons.

    PubMed

    Nishijo, Takuma; Momiyama, Toshihiko

    2016-07-01

    Modulatory roles of serotonin (5-HT) in GABAergic transmission onto basal forebrain cholinergic neurons were investigated, using whole-cell patch-clamp technique in the rat brain slices. GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) were evoked by focal stimulation. Bath application of 5-HT (0.1-300 μm) reversibly suppressed the amplitude of evoked IPSCs in a concentration-dependent manner. Application of a 5-HT1B receptor agonist, CP93129, also suppressed the evoked IPSCs, whereas a 5-HT1A receptor agonist, 8-OH-DPAT had little effect on the evoked IPSCs amplitude. In the presence of NAS-181, a 5-HT1B receptor antagonist, 5-HT-induced suppression of evoked IPSCs was antagonised, whereas NAN-190, a 5-HT1A receptor antagonist did not antagonise the 5-HT-induced suppression of evoked IPSCs. Bath application of 5-HT reduced the frequency of spontaneous miniature IPSCs without changing their amplitude distribution. The effect of 5-HT on miniature IPSCs remained unchanged when extracellular Ca(2+) was replaced by Mg(2+) . The paired-pulse ratio was increased by CP93129. In the presence of ω-CgTX, the N-type Ca(2+) channel blocker, ω-Aga-TK, the P/Q-type Ca(2+) channel blocker, or SNX-482, the R-type Ca(2+) channel blocker, 5-HT could still inhibit the evoked IPSCs. 4-AP, a K(+) channel blocker, enhanced the evoked IPSCs, and CP93129 had no longer inhibitory effect in the presence of 4-AP. CP93129 increased the number of action potentials elicited by depolarising current pulses. These results suggest that activation of presynaptic 5-HT1B receptors on the terminals of GABAergic afferents to basal forebrain cholinergic neurons inhibits GABA release in Ca(2+) influx-independent manner by modulation of K(+) channels, leading to enhancement of neuronal activities. PMID:27177433

  17. Ion permeation and conduction in a human recombinant 5-HT3 receptor subunit (h5-HT3A)

    PubMed Central

    Brown, A M; Hope, A G; Lambert, J J; Peters, J A

    1998-01-01

    A human recombinant homo-oligomeric 5-HT3 receptor (h5-HT3A) expressed in a human embryonic kidney cell line (HEK 293) was characterized using the whole-cell recording configuration of the patch clamp technique. 5-HT evoked transient inward currents (EC50 = 3.4 μm; Hill coefficient = 1.8) that were blocked by the 5-HT3 receptor antagonist ondansetron (IC50 = 103 pm) and by the non-selective agents metoclopramide (IC50 = 69 nm), cocaine (IC50 = 459 nm) and (+)-tubocurarine (IC50 = 2.8 μm). 5-HT-induced currents rectified inwardly and reversed in sign (E5-HT) at a potential of −2.2 mV. N-Methyl-d-glucamine was finitely permeant. Permeability ratios PNa/PCs and PNMDG/PCs were 0.90 and 0.083, respectively. Permeability towards divalent cations was assessed from measurements of E5-HT in media where Ca2+ and Mg2+ replaced Na+. PCa/PCs and PMg/PCs were calculated to be 1.00 and 0.61, respectively. Single channel chord conductance (γ) estimated from fluctuation analysis of macroscopic currents increased with membrane hyperpolarization from 243 fS at −40 mV to 742 fS at −100 mV. Reducing [Ca2+]o from 2 to 0.1 mm caused an increase in the whole-cell current evoked by 5-HT. A concomitant reduction in [Mg2+]o produced further potentiation. Fluctuation analysis indicates that a voltage-independent augmentation of γ contributes to this phenomenon. The data indicate that homo-oligomeric receptors composed of h5-HT3A subunits form inwardly rectifying cation-selective ion channels of low conductance that are permeable to Ca2+ and Mg2+. PMID:9508827

  18. Spinal 5-HT1A, not the 5-HT1B or 5-HT3 receptors, mediates descending serotonergic inhibition for late-phase mechanical allodynia of carrageenan-induced peripheral inflammation.

    PubMed

    Kim, Joung Min; Jeong, Seong Wook; Yang, Jihoon; Lee, Seong Heon; Kim, Woon Mo; Jeong, Seongtae; Bae, Hong Beom; Yoon, Myung Ha; Choi, Jeong Il

    2015-07-23

    Previous electrophysiological studies demonstrated a limited role of 5-hydroxytryptamine 3 receptor (5-HT3R), but facilitatory role of 5-HT1AR and 5-HT1BR in spinal nociceptive processing of carrageenan-induced inflammatory pain. The release of spinal 5-HT was shown to peak in early-phase and return to baseline in late-phase of carrageenan inflammation. We examined the role of the descending serotonergic projections involving 5-HT1AR, 5-HT1BR, and 5-HT3R in mechanical allodynia of early- (first 4h) and late-phase (24h after) carrageenan-induced inflammation. Intrathecal administration of 5-HT produced a significant anti-allodynic effect in late-phase, but not in early-phase. Similarly, intrathecal 5-HT1AR agonist (8-OH-DPAT) attenuated the intensity of late-phase allodynia in a dose dependent fashion which was antagonized by 5-HT1AR antagonist (WAY-100635), but produced no effect on the early-phase allodynia. However, other agonists or antagonists of 5-HT1BR (CP-93129, SB-224289) and 5-HT3R (m-CPBG, ondansetron) did not produce any anti- or pro-allodynic effect in both early- and late- phase allodynia. These results suggest that spinal 5-HT1A, but not 5-HT1B or 5-HT3 receptors mediate descending serotonergic inhibition on nociceptive processing of late-phase mechanical allodynia in carrageenan-induced inflammation. PMID:26037417

  19. The silent and selective 5-HT1A antagonist, WAY 100635, produces via an indirect mechanism, a 5-HT2A receptor-mediated behaviour in mice during the day but not at night. Short communication.

    PubMed

    Darmani, N A

    1998-01-01

    The head-twitch response (HTR) in rodents is considered to be a functional index for the activation of 5-HT2A receptors. Intraperitoneal administration of the silent and selective 5-HT1A receptor antagonist, WAY 100635, produced the HTR in mice in a dose-dependent bell-shaped manner. The induced behaviour followed a diurnal pattern in that WAY 100635 only produced a robust HTR frequency during the light period of the 24h daily cycle. Pretreatment with the selective 5-HT2A/C receptor antagonist, SR 46349B, potently, and in a dose-dependent manner attenuated the induced behaviour. It appears that WAY 100635 produces the HTR indirectly via disinhibition of endogenous serotonergic inhibitory tone operating on the somatodenritic pulse-modulating 5-HT1A autoreceptors. The latter antagonism seems to potentiate endogenous 5-HT release in serotonergic terminal field synapses which subsequently stimulates postsynaptic 5-HT2A receptors to produce the head-twitch behaviour. PMID:9826108

  20. Therapeutic Potential of 5-HT6 Receptor Agonists.

    PubMed

    Karila, Delphine; Freret, Thomas; Bouet, Valentine; Boulouard, Michel; Dallemagne, Patrick; Rochais, Christophe

    2015-10-22

    Given its predominant expression in the central nervous system (CNS), 5-hydroxytryptamine (5-HT: serotonin) subtype 6 receptor (5-HT6R) has been considered as a valuable target for the development of CNS drugs with limited side effects. After 2 decades of intense research, numerous selective ligands have been developed to target this receptor; this holds potential interest for the treatment of neuropathological disorders. In fact, some agents (mainly antagonists) are currently undergoing clinical trial. More recently, a series of potent and selective agonists have been developed, and preclinical studies have been conducted that suggest the therapeutic interest of 5-HT6R agonists. This review details the medicinal chemistry of these agonists, highlights their activities, and discusses their potential for treating cognitive issues associated with Alzheimer's disease (AD), depression, or obesity. Surprisingly, some studies have shown that both 5-HT6R agonists and antagonists exert similar procognitive activities. This article summarizes the hypotheses that could explain this paradox. PMID:26099069

  1. Selective 5-HT2C agonists as potential antidepressants.

    PubMed

    Leysen, D C

    1999-02-01

    The antidepressants currently used need improvement, especially in terms of efficacy, relapse rate and onset of action. In this review the clinical and experimental data which support the rationale for 5-HT2C agonists in the treatment of depression are listed. Next, the results obtained with the non-selective 5-HT2C agonists on the market and in clinical development are described. Finally, the preclinical data on the more selective 5-HT2C agonists are summarized. These recent preclinical results reveal a greater potency and effect size compared to fluoxetine, good tolerability and no evidence of tolerance development. Selective 5-HT2C agonists might become innovative drugs for the treatment of depression, panic, obsessive-compulsive disorder (OCD), some forms of aggression and eating disorders. PMID:16160946

  2. Pattern of arborization of the motor nerve terminals in the fast and slow mammalian muscles.

    PubMed

    Tomas, J; Santafé, M; Fenoll, R; Mayayo, E; Batlle, J; Lanuza, A; Piera, V

    1992-01-01

    A silver impregnation method and a morphometric approach were used to define differences existing in the motor nerve terminal branching pattern between a fast-twitch muscle (extensor digitorum longus) and a slow-twitch one (soleus) of the normal adult rat. Because no single measure can describe precisely all geometrical properties (ie both topology and metrics) of the nerve terminals, we evaluated morphologic parameters defining length and angular characteristics in the different terminal segments classified according to their centrifugal order. The main results indicate that the distal free-end segments in the extensor digitorum longus muscle are shorter and less divergent than in the soleus nerve terminals. The endings in the two muscles have different fractal dimensions. Findings are discussed in the context of the hypothetical mechanisms governing motor nerve terminal size and complexity. PMID:1628112

  3. Early attempts to visualize cortical monoamine nerve terminals.

    PubMed

    Hökfelt, Tomas

    2016-08-15

    The Falck-Hillarp, formaldehyde fluorescence method for the demonstration of monoamine neurons in a microscope was established in Lund, Sweden and published in 1962. In the same year Hillarp moved to Karolinska Institutet in Stockholm. Two years later Dahlström and Fuxe published the famous supplement in Acta Physiologica Scandinavica, describing the distribution of the dopamine, noradrenaline and serotonin cell groups in the rat brain. This landmark paper also represented an important contribution to an emerging discipline in neuroscience - chemical neuroanatomy. During the following years several modifications of the original method were developed, attempting to solve some shortcomings, one being the reproducible demonstration of noradrenaline nerve terminals in cortical regions. One result was the paper focused on in the present article, which also describes other efforts in the same direction going on in parallel, primarily, in Lund and Stockholm. As a result there was, in the mid 1970s, a fairly complete knowledge of the catecholamine systems in the rat brain. This article is part of a Special Issue entitled SI:50th Anniversary Issue. PMID:26806405

  4. Effects of the potassium channel blocking dendrotoxins on acetylcholine release and motor nerve terminal activity.

    PubMed

    Anderson, A J; Harvey, A L

    1988-01-01

    1. The effects of the K+ channel blocking toxins, the dendrotoxins, on neuromuscular transmission and motor nerve terminal activity were assessed on frog cutaneous pectoris, mouse diaphragm and mouse triangularis sterni nerve-muscle preparations. Endplate potentials (e.p.ps) and miniature e.p.ps were recorded with intracellular microelectrodes, and nerve terminal spikes were recorded with extracellular electrodes placed in the perineural sheaths of motor nerves. 2. Dendrotoxin from green mamba (Dendroaspis angusticeps) venom and toxin I from black mamba (D. polylepis) venom increased the amplitude of e.p.ps by increasing quantal content, and also induced repetitive e.p.ps. 3. Perineural recordings revealed that dendrotoxins could decrease the component of the waveform associated with K+ currents at the nerve terminals, and induce repetitive activation of nerve terminals. 4. In frog motor nerves, dendrotoxins are known to block the fast f1 component of the K+ current at nodes of Ranvier. Blockade of a similar component of the K+ current at motor nerve terminals may be responsible for the effects of these toxins on neuromuscular transmission. 5. Similar conclusions can be drawn from the results obtained from mouse neuromuscular junctions. PMID:2450611

  5. Modulation of dopamine transmission by 5HT2C and 5HT3 receptors: a role in the antidepressant response.

    PubMed

    Dremencov, Eliyahu; Weizmann, Yifat; Kinor, Noa; Gispan-Herman, Iris; Yadid, Gal

    2006-02-01

    Dopaminergic mesolimbic and mesocortical systems are fundamental in hedonia and motivation. Therefore their regulation should be central in understanding depression treatment. This review highlights the dopaminergic activity in relation to depressive behavior and suggests two putative receptors as potential targets for research and development of future antidepressants. In this article we review data that describe the role of serotonin in regulating dopamine release, via 5HT2C and 5HT3 receptors. This action of serotonin appears to be linked to depressive-like behavior and to onset of behavioral effects of antidepressants in an animal model of depression. We suggest that drugs or strategies that decrease 5HT2C and increase 5HT3 receptor-mediated dopamine release in the limbic areas of the brain may provide a fast onset of therapeutic effect. Clinical and basic research data supporting this hypothesis are discussed. PMID:16475958

  6. (1R, 3S)-(−)-Trans-PAT: A novel full-efficacy serotonin 5-HT2C receptor agonist with 5-HT2A and 5-HT2B receptor inverse agonist/antagonist activity

    PubMed Central

    Booth, Raymond G.; Fang, Lijuan; Huang, Yingsu; Wilczynski, Andrzej; Sivendran, Sashikala

    2009-01-01

    The serotonin 5-HT2A, 5-HT2B, and 5-HT2C G protein-coupled receptors signal primarily through Gαq to activate phospholipase C (PLC) and formation of inositol phosphates (IP) and diacylglycerol. The human 5-HT2C receptor, expressed exclusively in the central nervous system, is involved in several physiological and psychological processes. Development of 5-HT2C agonists that do not also activate 5-HT2A or 5-HT2B receptors is challenging because transmembrane domain identity is about 75% among 5-HT2 subtypes. This paper reports 5-HT2 receptor affinity and function of (1R,3S)-(−)-trans-1-phenyl-3-dimethylamino-1,2,3,4-tetrahydronaphthalene (PAT), a small molecule that produces anorexia and weight-loss after peripheral administration to mice. (−)-Trans-PAT is a stereoselective full-efficacy agonist at human 5-HT2C receptors, plus, it is a 5-HT2A/5-HT2B inverse agonist and competitive antagonist. The Ki of (−)-trans-PAT at 5-HT2A, 5-HT2B, and 5-HT2C receptors is 410, 1200, and 37 nM, respectively. Functional studies measured activation of PLC/[3H]-IP formation in clonal cells expressing human 5-HT2 receptors. At 5-HT2C receptors, (−)-trans-PAT is an agonist (EC50 = 20 nM) comparable to serotonin in potency and efficacy. At 5-HT2A and 5-HT2B receptors, (−)-trans-PAT is an inverse agonist (IC50 = 490 and 1,000 nM, respectively) and competitive antagonist (KB = 460 and 1400 nM, respectively) of serotonin. Experimental results are interpreted in light of molecular modeling studies indicating the (−)-trans-PAT protonated amine can form an ionic bond with D3.32 of 5-HT2A and 5-HT2C receptors, but, not with 5-HT2B receptors. In addition to probing 5-HT2 receptor structure and function, (−)-trans-PAT is a novel lead regarding 5-HT2C agonist/5-HT2A inverse agonist drug development for obesity and neuropsychiatric disorders. PMID:19397907

  7. Spinal 5-HT3 receptors mediate descending facilitation and contribute to behavioral hypersensitivity via a reciprocal neuron-glial signaling cascade

    PubMed Central

    2014-01-01

    Background It has been recently recognized that the descending serotonin (5-HT) system from the rostral ventromedial medulla (RVM) in the brainstem and the 5-HT3 receptor subtype in the spinal dorsal horn are involved in enhanced descending pain facilitation after tissue and nerve injury. However, the mechanisms underlying the activation of the 5-HT3 receptor and its contribution to facilitation of pain remain unclear. Results In the present study, activation of spinal 5-HT3 receptors by intrathecal injection of a selective 5-HT3 receptor agonist SR 57227 induced spinal glial hyperactivity, neuronal hyperexcitability and pain hypersensitivity in rats. We found that there was neuron-to-microglia signaling via the chemokine fractalkine, microglia to astrocyte signaling via cytokine IL-18, astrocyte to neuronal signaling by IL-1β, and enhanced activation of NMDA receptors in the spinal dorsal horn. Glial hyperactivation in spinal dorsal horn after hindpaw inflammation was also attenuated by molecular depletion of the descending 5-HT system by intra-RVM Tph-2 shRNA interference. Conclusions These findings offer new insights into the cellular and molecular mechanisms at the spinal level responsible for descending 5-HT-mediated pain facilitation during the development of persistent pain after tissue and nerve injury. New pain therapies should focus on prime targets of descending facilitation-induced glial involvement, and in particular the blocking of intercellular signaling transduction between neurons and glia. PMID:24913307

  8. 5-HT-1A receptor-mediated modulation of medullary expiratory neurones in the cat.

    PubMed Central

    Lalley, P M; Bischoff, A M; Richter, D W

    1994-01-01

    The involvement of the 5-HT-1A receptor in serotoninergic responses of stage 2 expiratory (E-2) neurones was investigated in pentobarbitone-anaesthetized, mechanically ventilated cats. The specific agonist of the 5-HT-1A receptor, 8-hydroxy-diproplaminotetralin (8-OH-DPAT), administered systemically or by ionophoresis directly on to the neurones, had a clear depressant effect. Administration of 8-OH-DPAT at doses of 10-50 micrograms kg-1 (I.V.) increased the membrane hyperpolarizations of E-2 neurones during the inspiratory and postinspiratory phases, and shortened their duration of activity in association with shortening of phrenic nerve activity. Discharges of E-2 neurones were also less intense. At doses of 50-90 micrograms kg-1, 8-OH-DPAT reduced or abolished inspiratory hyperpolarizations, and reduced expiratory depolarizations of membrane potential and discharge in parallel with inhibition of phrenic nerve discharges. The effects of the larger doses were reversed by I.V. injection of NAN-190, an antagonist at the 5-HT-1A receptor. Dose-dependent effects on the membrane potential and discharge of E-2 neurones, but not on phrenic nerve activity, were also seen by ionophoretic administration of 8-OH-DPAT on to E-2 neurones. At low currents, ejection of 8-OH-DPAT hyperpolarized the neurones without affecting the duration of inspiratory hyperpolarization and expiratory depolarization. This hyperpolarization depressed the intensity and the duration of expiratory discharges. Ejection with larger currents hyperpolarized the E-2 neurones further, and depressed expiratory depolarization leading to blockade of expiratory discharges. The effects on membrane potential were accompanied by decreased neuronal input resistance. This depressed the excitability of E-2 neurones as tested by discharge evoked by intracellular current injection. The amplitudes of action potentials decreased in parallel with the changes in input resistance. The effects were attributed to a

  9. Effects of dominance status on conditioned defeat and expression of 5-HT1A and 5-HT2A receptors

    PubMed Central

    Morrison, Kathleen E.; Swallows, Cody L.; Cooper, Matthew A.

    2011-01-01

    Past experience can alter how individuals respond to stressful events. The brain serotonin system is a key factor modulating stress-related behavior and may contribute to individual variation in coping styles. In this study we investigated whether dominant and subordinate hamsters respond differently to social defeat and whether their behavioral responses are associated with changes in 5-HT1A and 5-HT2A receptor immunoreactivity in several limbic brain regions. We paired weight-matched hamsters in daily aggressive encounters for two weeks so that they formed a stable dominance relationship. We also included controls that were exposed to an empty cage each day for two weeks. Twenty-four hours after the final pairing or empty cage exposure, subjects were socially defeated in 3, 5-min encounters with a more aggressive hamster. Twenty-four hours after social defeat, animals were tested for conditioned defeat in a 5-min social interaction test with a non-aggressive intruder. We collected brains following conditioned defeat testing and performed immunohistochemistry for 5-HT1A and 5-HT2A receptors. We found that dominants showed less submissive and defensive behavior at conditioned defeat testing compared to both subordinates and controls. Additionally, both dominants and subordinates had an increased number of 5-HT1A immunopositive cells in the basolateral amygdala compared to controls. Subordinates also had more 5-HT1A immunopositive cells in the dorsal medial amygdala than did controls. Finally, dominants had fewer 5-HT1A immunopositive cells in the paraventricular nucleus of the hypothalamus compared to controls. Our results indicate that dominant social status results in a blunted conditioned defeat response and a distinct pattern of 5-HT1A receptor expression, which may contribute to resistance to conditioned defeat. PMID:21362435

  10. Preclinical profile of the mixed 5-HT1A/5-HT2A receptor antagonist S 21,357.

    PubMed

    Griebel, G; Blanchard, D C; Rettori, M C; Guardiola-Lemaître, B; Blanchard, R J

    1996-06-01

    This study evaluated the pharmacological and behavioral effects of S 21,357, a drug with high affinity for both 5-HT1A and 5-HT2A receptors. The drug behaved as antagonist at both 5-HT1A autoreceptors and postsynaptic 5-HT1A receptors, as it prevented the inhibitory effect of lesopitron on the electrical discharge of the dorsal raphé nucleus (DRN) 5-HT neurons and the activity of forskolin-stimulated adenylate cyclase in hippocampal homogenates. In addition, S 21,357 (4 and 128 mg/kg, PO) inhibited 5-HTP-induced head-twitch responses in mice, indicating that it possesses 5-HT2A antagonistic properties. In a test battery designed to assess defensive behaviors of Swiss-Webster mice to the presence of, or situations associated with, a natural threat stimulus (i.e., rat), S 21,357 (0.12-2 mg/kg, IP) reduced contextual defense reactions after the rat was removed, risk assessment activities when the subject was chased, and finally, defensive attack behavior. These behavioral changes are consistent with fear/anxiety reduction. Furthermore, the drug strongly reduced flight reactions in response to the approaching rat. This last finding, taken together with recent results with panic-modulating drugs, suggest that S 21,357 may have potential efficacy against panic attack. Finally, our results suggest that compounds sharing high affinities for both 5-HT1A and 5-HT2A receptors may directly or synergistically increase the range of defensive behaviors affected. PMID:8743616

  11. Testosterone and its metabolites modulate 5HT1A and 5HT1B agonist effects on intermale aggression.

    PubMed

    Simon, N G; Cologer-Clifford, A; Lu, S F; McKenna, S E; Hu, S

    1998-01-01

    Our understanding of the neurochemical and neuroendocrine systems' regulating the display of offensive intermale aggression has progressed substantially over the past twenty years. Pharmacological studies have shown that serotonin, via its action at 5HT1A and/or 5HT1B receptor sites, modulates the display of intermale aggressive behavior and that its effects serve to decrease behavioral expression. Neuroendocrine investigations, in turn, have demonstrated that male-typical aggression is testosterone-dependent and studies of genetic effects, metabolic function and steroid receptor binding have shown that facilitation of behavioral displays can occur via independent androgen-sensitive or estrogen-sensitive pathways. Remarkably, there have been virtually no studies that examined the interrelationship between these facilitative and inhibitory systems. As an initial step toward characterizing the interaction between the systems, studies were conducted that assessed hormonal modulation of serotonin function at 5HT1A and 5HT1B receptor sites. They demonstrated: (1) that the androgenic and estrogenic metabolites of testosterone differentially modulate the ability of systemically administered 8-OH-DPAT (a 5HT1A agonist) and CGS12066B (a 5HT1B agonist) to decrease offensive aggression; and (2) when microinjected into the lateral septum (LS) or medial preoptic area (MPO), the aggression-attenuating effects of 1A and 1B agonists differ regionally and vary with the steroidal milieu. In general, the results suggest that estrogens establish a restrictive environment for attenuation of T-dependent aggression by 8-OH-DPAT and CGS 12066B, while androgens either do not inhibit, or perhaps even facilitate, the ability of 5HT1A and 5HT1B agonists to reduce aggression. Potential mechanisms involved in the production of these steroidal effects are discussed and emerging issues that may impact on efforts to develop an integrative neurobiological model of offensive, intermale aggression

  12. Spinal 5-HT-receptors and tonic modulation of transmission through a withdrawal reflex pathway in the decerebrated rabbit.

    PubMed Central

    Clarke, R. W.; Harris, J.; Houghton, A. K.

    1996-01-01

    1. In decerebrated, non-spinalized rabbits, intrathecal administration of either of the selective 5-HT1A-receptor antagonists (S)WAY-100135 or WAY-100635 resulted in dose-dependent enhancement of the reflex responses of gastrocnemius motoneurones evoked by electrical stimulation of all myelinated afferents of the sural nerve. The approximate ED50 for WAY-100635 was 0.9 nmol and that for (S)WAY-100135 13 nmol. Intrathecal doses of the antagonists which caused maximal facilitation of reflexes in non-spinalized rabbits had no effect in spinalized preparations. 2. In non-spinalized animals, intravenous administration of (S)WAY-100135 was significantly less effective in enhancing reflexes than when it was given by the intrathecal route. 3. When given intrathecally, the selective 5-HT 2A/2C-receptor antagonist, ICI 170,809, produced a bellshaped dose-effect curve, augmenting reflexes at low doses (< or = 44 nmol), but reducing them at higher doses (982 nmol). Idazoxan, the selective alpha 2-adrenoceptor antagonist, was less effective in enhancing reflex responses when given intrathecally after ICI 170,809 compared to when it was given alone. Intravenous ICI 170,809 resulted only in enhancement of reflexes and the facilitatory effects of subsequent intrathecal administration of idazoxan were not compromised. 4. The selective 5-HT3-receptor blocker ondansetron faciliated gastrocnemius medialis reflex responses in a dose-related manner when given by either intrathecal or intravenous routes. This drug was slightly more potent when given i.v. and it did not alter the efficacy of subsequent intrathecal administration of idazoxan. 5. None of the antagonists had any consistent effects on arterial blood pressure or heart rate. 6. These data are consistent with the idea that, in the decrebrated rabbit, 5-HT released from descending axons has multiple roles in controlling transmission through the sural-gastrocnemius medialis reflex pathway. Thus, it appears 5-HT tonically inhibits

  13. Distinct target-derived signals organize formation, maturation, and maintenance of motor nerve terminals.

    PubMed

    Fox, Michael A; Sanes, Joshua R; Borza, Dorin-Bogdan; Eswarakumar, Veraragavan P; Fässler, Reinhard; Hudson, Billy G; John, Simon W M; Ninomiya, Yoshifumi; Pedchenko, Vadim; Pfaff, Samuel L; Rheault, Michelle N; Sado, Yoshikazu; Segal, Yoav; Werle, Michael J; Umemori, Hisashi

    2007-04-01

    Target-derived factors organize synaptogenesis by promoting differentiation of nerve terminals at synaptic sites. Several candidate organizing molecules have been identified based on their bioactivities in vitro, but little is known about their roles in vivo. Here, we show that three sets of organizers act sequentially to pattern motor nerve terminals: FGFs, beta2 laminins, and collagen alpha(IV) chains. FGFs of the 7/10/22 subfamily and broadly distributed collagen IV chains (alpha1/2) promote clustering of synaptic vesicles as nerve terminals form. beta2 laminins concentrated at synaptic sites are dispensable for embryonic development of nerve terminals but are required for their postnatal maturation. Synapse-specific collagen IV chains (alpha3-6) accumulate only after synapses are mature and are required for synaptic maintenance. Thus, multiple target-derived signals permit discrete control of the formation, maturation, and maintenance of presynaptic specializations. PMID:17418794

  14. [Suppressing effect of the serotonin 5HT1B/D receptor agonist rizatriptan on calcitonin gene-related peptide (CGRP) concentration in migraine attacks].

    PubMed

    Stepień, Adam; Jagustyn, Piotr; Trafny, Elzbieta Anna; Widerkiewicz, Krzysztof

    2003-01-01

    Calcitonin gene-related peptide (CGRP) is one of the neuropeptides most abundant in the nervous tissue. Recent studies indicate that local cranial release of CGRP from the trigeminal nerve perivascular endings within arachnoidea plays an important role in the pathophysiology of migraine attacks and cluster headaches. Elevated CGRP levels in cranial venous blood (in the jugular vein) during an acute spontaneous migraine attack have been reported in rather few studies so far. Sumatriptan--a selective serotonin 5HT1B/D receptor agonist, highly effective in terminating migraine attacks, decreases the elevated CGRP level back to normal. The aim of our study was to determine the effect of rizatriptan (a drug from a new generation of triptans) on CGRP release in migraine attacks. In 45 patients suffering from migraine attacks with and without aura, plasma CGRP levels were assessed during an attack twice: before treatment and two hours after rizatriptan administration. In the group under study the plasma CGRP level before treatment was significantly higher than that measured two hours after rizatriptan administration. The decrease in CGRP levels was associated with subsidence of the migraine attack. There was no difference between migraine patients with and without aura. These results suggest that triptans as serotonin 5HT1B/D receptor agonists decrease CGRP plasma concentration in migraine attacks. PMID:15174248

  15. Effect of 5-HT2A and 5-HT2C receptors on temporal discrimination by mice.

    PubMed

    Halberstadt, Adam L; Sindhunata, Ivan S; Scheffers, Kees; Flynn, Aaron D; Sharp, Richard F; Geyer, Mark A; Young, Jared W

    2016-08-01

    Timing deficits are observed in patients with schizophrenia. Serotonergic hallucinogens can also alter the subjective experience of time. Characterizing the mechanism through which the serotonergic system regulates timing will increase our understanding of the linkage between serotonin (5-HT) and schizophrenia, and will provide insight into the mechanism of action of hallucinogens. We investigated whether interval timing in mice is altered by hallucinogens and other 5-HT2 receptor ligands. C57BL/6J mice were trained to perform a discrete-trials temporal discrimination task. In the discrete-trials task, mice were presented with two levers after a variable interval. Responding on lever A was reinforced if the interval was <6.5 s, and responding on lever B was reinforced if the interval was >6.5 s. A 2-parameter logistic function was fitted to the proportional choice for lever B (%B responding), yielding estimates of the indifference point (T50) and the Weber fraction (a measure of timing precision). The 5-HT2A antagonist M100907 increased T50, whereas the 5-HT2C antagonist SB-242,084 reduced T50. The results indicate that 5-HT2A and 5-HT2C receptors have countervailing effects on the speed of the internal pacemaker. The hallucinogen 2,5-dimethoxy-4-iodoamphetamine (DOI; 3 mg/kg IP), a 5-HT2 agonist, flattened the response curve at long stimulus intervals and shifted it to the right, causing both T50 and the Weber fraction to increase. The effect of DOI was antagonized by M100907 (0.03 mg/kg SC) but was unaffected by SB-242,084 (0.1 mg/kg SC). Similar to DOI, the selective 5-HT2A agonist 25CN-NBOH (6 mg/kg SC) reduced %B responding at long stimulus intervals, and increased T50 and the Weber fraction. These results demonstrate that hallucinogens alter temporal perception in mice, effects that are mediated by the 5-HT2A receptor. It appears that 5-HT regulates temporal perception, suggesting that altered serotonergic signaling may contribute to the timing deficits

  16. Examination of the hippocampal contribution to serotonin 5-HT2A receptor-mediated facilitation of object memory in C57BL/6J mice.

    PubMed

    Zhang, Gongliang; Cinalli, David; Cohen, Sarah J; Knapp, Kristina D; Rios, Lisa M; Martínez-Hernández, José; Luján, Rafael; Stackman, Robert W

    2016-10-01

    The rodent hippocampus supports non-spatial object memory. Serotonin 5-HT2A receptors (5-HT2AR) are widely expressed throughout the hippocampus. We previously demonstrated that the activation of 5-HT2ARs enhanced the strength of object memory assessed 24 h after a limited (i.e., weak memory) training procedure. Here, we examined the subcellular distribution of 5-HT2ARs in the hippocampal CA1 region and underlying mechanisms of 5-HT2AR-mediated object memory consolidation. Analyses with immuno-electron microscopy revealed the presence of 5-HT2ARs on the dendritic spines and shafts of hippocampal CA1 neurons, and presynaptic terminals in the CA1 region. In an object recognition memory procedure that places higher demand on the hippocampus, only post-training systemic or intrahippocampal administration of the 5-HT2AR agonist TCB-2 enhanced object memory. Object memory enhancement by TCB-2 was blocked by the 5-HT2AR antagonist, MDL 11,937. The memory-enhancing dose of systemic TCB-2 increased extracellular glutamate levels in hippocampal dialysate samples, and increased the mean in vivo firing rate of hippocampal CA1 neurons. In summary, these data indicate a pre- and post-synaptic distribution of 5-HT2ARs, and activation of 5-HT2ARs selectively enhanced the consolidation of object memory, without affecting encoding or retrieval. The 5-HT2AR-mediated facilitation of hippocampal memory may be associated with an increase in hippocampal neuronal firing and glutamate efflux during a post-training time window in which recently encoded memories undergo consolidation. PMID:27114257

  17. Mechanisms of action of the 5-HT1B/1D receptor agonists.

    PubMed

    Tepper, Stewart J; Rapoport, Alan M; Sheftell, Fred D

    2002-07-01

    Recent studies of the pathophysiology of migraine provide evidence that the headache phase is associated with multiple physiologic actions. These actions include the release of vasoactive neuropeptides by the trigeminovascular system, vasodilation of intracranial extracerebral vessels, and increased nociceptive neurotransmission within the central trigeminocervical complex. The 5-HT(1B/1D) receptor agonists, collectively known as triptans, are a major advance in the treatment of migraine. The beneficial effects of the triptans in patients with migraine are related to their multiple mechanisms of action at sites implicated in the pathophysiology of migraine. These mechanisms are mediated by 5-HT(1B/1D) receptors and include vasoconstriction of painfully dilated cerebral blood vessels, inhibition of the release of vasoactive neuropeptides by trigeminal nerves, and inhibition of nociceptive neurotransmission. The high affinity of the triptans for 5-HT(1B/1D) receptors and their favorable pharmacologic properties contribute to the beneficial effects of these drugs, including rapid onset of action, effective relief of headache and associated symptoms, and low incidence of adverse effects. PMID:12117355

  18. Vortioxetine, but not escitalopram or duloxetine, reverses memory impairment induced by central 5-HT depletion in rats: evidence for direct 5-HT receptor modulation.

    PubMed

    Jensen, Jesper Bornø; du Jardin, Kristian Gaarn; Song, Dekun; Budac, David; Smagin, Gennady; Sanchez, Connie; Pehrson, Alan Lars

    2014-01-01

    Depressed patients suffer from cognitive dysfunction, including memory deficits. Acute serotonin (5-HT) depletion impairs memory and mood in vulnerable patients. The investigational multimodal acting antidepressant vortioxetine is a 5-HT3, 5-HT7 and 5-HT1D receptor antagonist, 5-HT1B receptor partial agonist, 5-HT1A receptor agonist and 5-HT transporter (SERT) inhibitor that enhances memory in normal rats in novel object recognition (NOR) and conditioned fear (Mørk et al., 2013). We hypothesized that vortioxetine's 5-HT receptor mechanisms are involved in its memory effects, and therefore investigated these effects in 5-HT depleted rats. Four injections of the irreversible tryptophan hydroxylase inhibitor 4-chloro-dl-phenylalanine methyl ester hydrochloride (PCPA, 86mg/kg, s.c.) induced 5-HT depletion, as measured in hippocampal homogenate and microdialysate. The effects of acute challenge with vortioxetine or the 5-HT releaser fenfluramine on extracellular 5-HT were measured in PCPA-treated and control rats. PCPA's effects on NOR and spontaneous alternation (SA) performance were assessed along with the effects of acute treatment with 5-hydroxy-l-tryptophan (5-HTP), vortioxetine, the selective 5-HT reuptake inhibitor escitalopram, or the 5-HT norepinephrine reuptake inhibitor duloxetine. SERT occupancies were estimated by ex vivo autoradiography. PCPA depleted central 5-HT by >90% in tissue and microdialysate, and impaired NOR and SA performance. Restoring central 5-HT with 5-HTP reversed these deficits. At similar SERT occupancies (>90%) vortioxetine, but not escitalopram or duloxetine, restored memory performance. Acute fenfluramine significantly increased extracellular 5-HT in control and PCPA-treated rats, while vortioxetine did so only in control rats. Thus, vortioxetine restores 5-HT depletion impaired memory performance in rats through one or more of its receptor activities. PMID:24284262

  19. Increased expression of 5-HT1B receptors by Herpes simplex virus gene transfer in septal neurons: new in-vitro and in-vivo models to study 5-HT1B receptor function

    PubMed Central

    Riegert, Céline; Rothmaier, Anna Katharina; Leemhuis, Jost; Sexton, Timothy J.; Neumaier, John F.; Cassel, Jean-Christophe; Jackisch, Rolf

    2009-01-01

    Serotonergic modulation of acetylcholine (ACh) release after neuron-specific increase of the expression of 5-HT1B receptors by gene transfer was studied in-vitro and in-vivo. The increased expression of the 5-HT1B receptor in-vitro was induced by treating rat primary fetal septal cell cultures for 3 days with a viral vector inducing the expression of green fluorescent protein alone (GFP vector), or, in addition, of 5-HT1B receptors (HA1B/GFP vector). The transfection resulted in a high number of GFP-positive cells, part of which being immunopositive for choline acetyltransferase. In HA1B/GFP-cultures (vs. GFP-cultures), electrically-evoked ACh release was significantly more sensitive to the inhibitory action of the 5-HT1B agonist CP-93,129. Increased expression of the 5-HT1B receptor in-vivo was induced by stereotaxic injections of the vectors into the rat septal region. Three days later, electrically-evoked release of ACh in hippocampal slices of HA1B/GFP-treated rats was lower than in their GFP-treated counterparts, showing a higher inhibitory efficacy of endogenous 5-HT on cholinergic terminals after transfection. Moreover, CP-93,129 had a higher inhibitory potency. In conclusion, the HA1B/GFP vector reveals a useful tool to induce a targeted increase of 5-HT1B heteroreceptors on cholinergic neurons in selected CNS regions, which provides interesting perspectives for functional approaches at more integrated levels. PMID:18502320

  20. Dorsal Raphe Neurons Signal Reward through 5-HT and Glutamate

    PubMed Central

    Liu, Zhixiang; Zhou, Jingfeng; Li, Yi; Hu, Fei; Lu, Yao; Ma, Ming; Feng, Qiru; Zhang, Ju-en; Wang, Daqing; Zeng, Jiawei; Bao, Junhong; Kim, Ji-Young; Chen, Zhou-Feng; Mestikawy, Salah El; Luo, Minmin

    2015-01-01

    Summary The dorsal raphe nucleus (DRN) in the midbrain is a key center for serotonin (5-hydroxytryptamine; 5-HT) expressing neurons. Serotonergic neurons in the DRN have been theorized to encode punishment by opposing the reward signaling of dopamine neurons. Here, we show that DRN neurons encode reward, but not punishment, through 5-HT and glutamate. Optogenetic stimulation of DRN Pet-1 neurons reinforces mice to explore the stimulation-coupled spatial region, shifts sucrose preference, drives optical self-stimulation, and directs sensory discrimination learning. DRN Pet-1 neurons increase their firing activity during reward tasks and this activation can be used to rapidly change neuronal activity patterns in the cortnassociated with 5-HT, they also release glutamate, and both neurotransmitters contribute to reward signaling. These experiments demonstrate the ability of DRN neurons to organize reward behaviors and might provide insights into the underlying mechanisms of learning facilitation and anhedonia treatment. PMID:24656254

  1. Vortioxetine dose-dependently reverses 5-HT depletion-induced deficits in spatial working and object recognition memory: a potential role for 5-HT1A receptor agonism and 5-HT3 receptor antagonism.

    PubMed

    du Jardin, Kristian Gaarn; Jensen, Jesper Bornø; Sanchez, Connie; Pehrson, Alan L

    2014-01-01

    We previously reported that the investigational multimodal antidepressant, vortioxetine, reversed 5-HT depletion-induced memory deficits while escitalopram and duloxetine did not. The present report studied the effects of vortioxetine and the potential impact of its 5-HT1A receptor agonist and 5-HT3 receptor antagonist properties on 5-HT depletion-induced memory deficits. Recognition and spatial working memory were assessed in the object recognition (OR) and Y-maze spontaneous alternation (SA) tests, respectively. 5-HT depletion was induced in female Long-Evans rats using 4-cholro-DL-phenylalanine methyl ester HCl (PCPA) and receptor occupancies were determined by ex vivo autoradiography. Rats were acutely dosed with vortioxetine, ondansetron (5-HT3 receptor antagonist) or flesinoxan (5-HT1A receptor agonist). The effects of chronic vortioxetine administration on 5-HT depletion-induced memory deficits were also assessed. 5-HT depletion reliably impaired memory performance in both the tests. Vortioxetine reversed PCPA-induced memory deficits dose-dependently with a minimal effective dose (MED) ≤0.1mg/kg (∼80% 5-HT3 receptor occupancy; OR) and ≤3.0mg/kg (5-HT1A, 5-HT1B, 5-HT3 receptor occupancy: ∼15%, 60%, 95%) in SA. Ondansetron exhibited a MED ≤3.0μg/kg (∼25% 5-HT3 receptor occupancy; OR), but was inactive in the SA test. Flesinoxan had a MED ≤1.0mg/kg (∼25% 5-HT1A receptor occupancy; SA); only 1.0mg/kg ameliorated deficits in the NOR. Chronic p.o. vortioxetine administration significantly improved memory performance in OR and occupied 95%, 66%, and 9.5% of 5-HT3, 5-HT1B, and 5-HT1A receptors, respectively. Vortioxetine's effects on SA performance may involve 5-HT1A receptor agonism, but not 5-HT3 receptor antagonism, whereas the effects on OR performance may involve 5-HT3 receptor antagonism and 5-HT1A receptor agonism. PMID:23916504

  2. Evidence for 5-HT7 receptors mediating relaxation of human colonic circular smooth muscle

    PubMed Central

    Prins, Nicolaas H; Briejer, Michel R; Van Bergen, Patrick J E; Akkermans, Louis M A; Schuurkes, Jan A J

    1999-01-01

    5-HT4 receptors mediate relaxation of human colon circular muscle. However, after 5-HT4 receptor blockade (SB 204070 10 nM), 5-HT still induced a relaxation (pEC50 6.3). 5-HT4 receptors were sufficiently blocked, as the curves to 5-HT obtained in the presence of 10 and 100 nM SB 204070 were indistinguishable. This 5-HT-induced relaxation was tetrodotoxin-insensitive, indicative of a smooth muscle relaxant 5-HT receptor. This, and the rank order of potency (5-CT=5-MeOT=5-HT) suggested involvement of 5-HT1 or 5-HT7 receptors. Mesulergine, a 5-HT7 receptor antagonist at nanomolar concentrations, and a 5-HT1 receptor antagonist at micromolar concentrations, competitively antagonized the 5-HT-induced relaxation (pKB 8.3) and antagonized the relaxation to 5-CT. Methysergide antagonized the 5-HT-induced relaxation (pA2 7.6). It is concluded that the profile of the smooth muscle inhibitory 5-HT receptor resembles that of the 5-HT7 receptor. These data provide the first evidence for functional human 5-HT7 receptors. PMID:10556917

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

    PubMed

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

    2014-01-01

    The nervus terminalis (or terminal nerve) system was discovered in an elasmobranch species more than a century ago. Over the past century, it has also been recognized in other vertebrate groups, from agnathans to mammals. However, its origin, functions or relationship with the olfactory system are still under debate. Despite the abundant literature about the nervus terminalis system in adult elasmobranchs, its development has been overlooked. Studies in other vertebrates have reported newly differentiated neurons of the terminal nerve system migrating from the olfactory epithelium to the telencephalon as part of a 'migratory mass' of cells associated with the olfactory nerve. Whether the same occurs in developing elasmobranchs (adults showing anatomically separated nervus terminalis and olfactory systems) has not yet been determined. In this work we characterized for the first time the development of the terminal nerve and ganglia in an elasmobranch, the lesser spotted dogfish (Scyliorhinus canicula), by means of tract-tracing techniques combined with immunohistochemical markers for the terminal nerve (such as FMRF-amide peptide), for the developing components of the olfactory system (Gα0 protein, GFAP, Pax6), and markers for early postmitotic neurons (HuC/D) and migrating immature neurons (DCX). We discriminated between embryonic olfactory and terminal nerve systems and determined that both components may share a common origin in the migratory mass. We also localized the exact point where they split off near the olfactory nerve-olfactory bulb junction. The study of the development of the terminal nerve system in a basal gnathostome contributes to the knowledge of the ancestral features of this system in vertebrates, shedding light on its evolution and highlighting the importance of elasmobranchs for developmental and evolutionary studies. PMID:25402659

  4. Expression of the spinal 5-HT7 receptor and p-ERK pathway in the carrageenan inflammatory pain of rats

    PubMed Central

    Cho, Soo Young; Ki, Hyoung Gon; Kim, Joung Min; Oh, Jin Myung; Yang, Ji Hoon; Kim, Woong Mo; Lee, Hyung Gon; Yoon, Myung Ha

    2015-01-01

    Background Although the inhibitory role of the 5-hydroxytrypatmine receptor 7(5-HT7R) on nociceptive processing is generally recognized, an excitatory effect associated with a reduced 5-HT7R expression has also been observed in the nerve injury model. In the carrageenan model, no significant effect is produced by the 5-HT7R activation, but the change in 5-HT7R expression has not been examined. Lesioning of the spinal serotonergic pathway enhances allodynia in the carrageenan model, but it also relieves several other pain states, including in the formalin model. While lesioning suppresses the activation of the extracellular signal-regulated kinase (ERK) of the spinal cord in the formalin model, its role in the carrageenan model has not been reported. Methods Following intraplantar injections of carrageenan, the spinal 5-HT7R expression was examined using Western blotting in male Sprague-Dawley rats. The effect of serotonergic pathway lesioning with intrathecal 5,7-dihydroxytryptamine (5,7-DHT) on the expression of the phospho-ERK was measured. Results The expression of the 5-HT7R in the carrageenan model was not significantly different from that of naive animals. The expression of the spinal p-ERK in the carrageenan model was significantly increased, but returned to the level of a naive rat 1 hour after the carrageenan injection. However, it remained significantly higher 1 hour after the injection in the animals treated with 5,7-DHT than in the naive and control rats. Conclusions The expression of the spinal 5-HT7R is not altered by peripheral inflammation with carrageenan, suggesting that the lack of antinociceptive effect of the 5-HT7R activation is partly attributable to the absence of changes in the expression of the 5-HT7R in the spinal cord. The extended increase of the spinal p-ERK might be related to the enhanced pain behavior in the animals with lesions of the spinal serotonergic pathway in the carrageenan model. PMID:25844136

  5. Variation within the serotonin (5-HT) 5-HT2C receptor system aligns with vulnerability to cocaine cue reactivity

    PubMed Central

    Anastasio, N C; Liu, S; Maili, L; Swinford, S E; Lane, S D; Fox, R G; Hamon, S C; Nielsen, D A; Cunningham, K A; Moeller, F G

    2014-01-01

    Cocaine dependence remains a challenging public health problem with relapse cited as a major determinant in its chronicity and severity. Environmental contexts and stimuli become reliably associated with its use leading to durable conditioned responses (‘cue reactivity') that can predict relapse as well as treatment success. Individual variation in the magnitude and influence of cue reactivity over behavior in humans and animals suggest that cue-reactive individuals may be at greater risk for the progression to addiction and/or relapse. In the present translational study, we investigated the contribution of variation in the serotonin (5-HT) 5-HT2C receptor (5-HT2CR) system in individual differences in cocaine cue reactivity in humans and rodents. We found that cocaine-dependent subjects carrying a single nucleotide polymorphism (SNP) in the HTR2C gene that encodes for the conversion of cysteine to serine at codon 23 (Ser23 variant) exhibited significantly higher attentional bias to cocaine cues in the cocaine-word Stroop task than those carrying the Cys23 variant. In a model of individual differences in cocaine cue reactivity in rats, we identified that high cocaine cue reactivity measured as appetitive approach behavior (lever presses reinforced by the discrete cue complex) correlated with lower 5-HT2CR protein expression in the medial prefrontal cortex and blunted sensitivity to the suppressive effects of the selective 5-HT2CR agonist WAY163909. Our translational findings suggest that the functional status of the 5-HT2CR system is a mechanistic factor in the generation of vulnerability to cocaine-associated cues, an observation that opens new avenues for future development of biomarker and therapeutic approaches to suppress relapse in cocaine dependence. PMID:24618688

  6. The spatial relationship between the musculature and the NADPH-diaphorase activity, 5-HT and FMRFamide immunoreactivities in redia, cercaria and adult Echinoparyphium aconiatum (Digenea).

    PubMed

    Terenina, N B; Tolstenkov, O; Fagerholm, H-P; Serbina, E A; Vodjanitskaja, S N; Gustafsson, M K S

    2006-04-01

    The spatial relationship between the musculature and the NADPH-diaphorase (NADPH-d) activity, 5-HT and FMRFamide immunoreactivities in redia, cercaria and adult Echinoparyphium aconiatum was studied using scanning electron microscopy (SEM), NADPH-d histochemistry, immunocytochemistry, and confocal scanning laser microscopy (CSLM). TRITC-conjugated phalloidin was used to stain the musculature. Staining for NADPH-d was observed in the central (CNS) and peripheral nervous system (PNS) of all three stages. NADPH-d positive nerves occurred very close to muscle fibres. 5-HT-immunoreactive (5-HT-IR) nerve cells and fibres occurred in the CNS and PNS and close to muscle fibres. FMRFamide-IR nerve fibres were observed in the CNS and PNS of adult worms. This is the first time, the presence of the NADPH-d has been demonstrated in the larval as well as the adult stages of a fluke. PMID:16494908

  7. Morphology and Functional Anatomy of the Recurrent Laryngeal Nerve with Extralaryngeal Terminal Bifurcation

    PubMed Central

    Dogan, Sami

    2016-01-01

    Anatomical variations of the recurrent laryngeal nerve (RLN), such as an extralaryngeal terminal bifurcation (ETB), threaten the safety of thyroid surgery. Besides the morphology of the nerve branches, intraoperative evaluation of their functional anatomy may be useful to preserve motor activity. We exposed 67 RLNs in 36 patients. The main trunk, bifurcation point, and terminal branches of bifid nerves were macroscopically determined and exposed during thyroid surgery. The functional anatomy of the nerve branches was evaluated by intraoperative nerve monitoring (IONM). Forty-six RLNs with an ETB were intraoperatively exposed. The bifurcation point was located along the prearterial, arterial, and postarterial segments in 11%, 39%, and 50% of bifid RLNs, respectively. Motor activity was determined in all anterior branches. The functional anatomy of terminal branches detected motor activity in 4 (8.7%) posterior branches of 46 bifid RLNs. The motor activity in posterior branches created a wave amplitude at 25–69% of that in the corresponding anterior branches. The functional anatomy of bifid RLNs demonstrated that anterior branches always contained motor fibres while posterior branches seldom contained motor fibres. The motor activity of the posterior branch was weaker than that of the anterior branch. IONM may help to differentiate between motor and sensory functions of nerve branches. The morphology and functional anatomy of all nerve branches must be preserved to ensure a safer surgery. PMID:27493803

  8. Differential effect of viral overexpression of nucleus accumbens shell 5-HT1B receptors on stress- and cocaine priming-induced reinstatement of cocaine seeking

    PubMed Central

    Nair, Sunila G.; Furay, Amy R.; Liu, Yusha; Neumaier, John F.

    2013-01-01

    5-HT1B receptors are densely expressed on terminals of medium spiny neurons projecting from the nucleus accumbens shell (NAccSh) to the ventral tegmental area, where 5-HT1B receptors modulate GABA release directly, and firing of dopaminergic neurons indirectly. While interactions between NAccSh 5-HT1B receptors and stress have been reported in early stages of psychostimulant-induced neuroadaptations, specifically psychomotor sensitization, the effect of this interaction on later stages of drug seeking is currently unknown. Here, we examined the effect of herpes simplex virus (HSV)-mediated overexpression of NAccSh 5-HT1B receptors on reinstatement of cocaine seeking induced by exposure to stress or a cocaine prime. Rats were trained to self-administer cocaine (0.75 mg/kg/infusion) and the operant response was extinguished. Rats were then injected with viral vector expressing 5-HT1B and green fluorescent protein (GFP) or GFP alone into the NAccSh. The effect of 5-HT1B receptor overexpression was assessed on reinstatement induced by intermittent footshock (0.5 mA for 15 minutes) or a cocaine prime (10 mg/kg, ip). Results indicate that NAccSh 5-HT1B receptor overexpression had no effect on footshock reinstatement while significantly decreasing cocaine priming-induced reinstatement. We also found that NAccSh overexpression of 5-HT1B receptors had no effect on saccharin intake following social defeat stress. These results suggest that the efficacy of pharmacological agents targeting 5-HT1B receptors for the treatment of cocaine relapse will depend largely on the nature of the reinstating stimulus. Taken together with previous results it appears that NAccSh 5-HT1B receptors influence stress responses in early, but not in the later stages of psychostimulant-induced neuroadaptations. PMID:24075973

  9. 5-HT3 Receptor Brain-Type B-Subunits are Differentially Expressed in Heterologous Systems

    PubMed Central

    2015-01-01

    Genes for five different 5-HT3 receptor subunits have been identified. Most of the subunits have multiple isoforms, but two isoforms of the B subunits, brain-type 1 (Br1) and brain-type 2 (Br2) are of particular interest as they appear to be abundantly expressed in human brain, where 5-HT3B subunit RNA consists of approximately 75% 5-HT3Br2, 24% 5-HT3Br1, and <1% 5-HT3B. Here we use two-electrode voltage-clamp, radioligand binding, fluorescence, whole cell, and single channel patch-clamp studies to characterize the roles of 5-HT3Br1 and 5-HT3Br2 subunits on function and pharmacology in heterologously expressed 5-HT3 receptors. The data show that the 5-HT3Br1 transcriptional variant, when coexpressed with 5-HT3A subunits, alters the EC50, nH, and single channel conductance of the 5-HT3 receptor, but has no effect on the potency of competitive antagonists; thus, 5-HT3ABr1 receptors have the same characteristics as 5-HT3AB receptors. There were some differences in the shapes of 5-HT3AB and 5-HT3ABr1 receptor responses, which were likely due to a greater proportion of homomeric 5-HT3A versus heteromeric 5-HT3ABr1 receptors in the latter, as expression of the 5-HT3Br1 compared to the 5-HT3B subunit is less efficient. Conversely, the 5-HT3Br2 subunit does not appear to form functional channels with the 5-HT3A subunit in either oocytes or HEK293 cells, and the role of this subunit is yet to be determined. PMID:25951416

  10. The 5-HT[subscript 3A] Receptor Is Essential for Fear Extinction

    ERIC Educational Resources Information Center

    Kondo, Makoto; Nakamura, Yukiko; Ishida, Yusuke; Yamada, Takahiro; Shimada, Shoichi

    2014-01-01

    The 5-HT [subscript 3] receptor, the only ionotropic 5-HT receptor, is expressed in limbic regions, including the hippocampus, amygdala, and cortex. However, it is not known whether it has a role in fear memory processes. Analysis of 5-HT [subscript 3A] receptor knockout mice in fear conditioning paradigms revealed that the 5-HT [subscript 3A]…

  11. 5-HT2CRs expressed by pro-opiomelanocortin neurons regulate insulin sensitivity in liver

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mice lacking 5-HT 2C receptors displayed hepatic insulin resistance, a phenotype normalized by re-expression of 5-HT2CRs only in pro-opiomelanocortin (POMC) neurons. 5-HT2CR deficiency also abolished the anti-diabetic effects of meta-chlorophenylpiperazine (a 5-HT2CR agonist); these effects were re...

  12. Motor nerve terminal restoration after focal destruction in young and old mice.

    PubMed

    Robbins, N; Kuchynski, M; Polak, J; Grasso, A

    1990-01-01

    Regeneration of soleus motor nerve terminals after focal destruction by black widow spider venom (BWSV) or its active factor alpha-latrotoxin (LTx) was compared in young and old CBF-1 mice. The object was to determine whether previously reported delayed regeneration after nerve injury in old rodents was due to altered removal of debris, or delay or aberrancy in structural or functional restoration of the neuromuscular junction. In addition, the use of a new fluorescent technique permitted for the first time quantitation of the accuracy of early nerve terminal regeneration in mammalian muscle. Immunohistochemical and electron micrographic studies showed no age difference in destruction of terminals and removal of debris 2 days after toxin application. The indirect twitch and structural reinnervation (measured with flourescent techniques) returned to an equal extent in young and old mice beginning at 3 days after LTx treatment. BWSV (as opposed to LTx) delayed regeneration 1 day in young but not in old mice. On the first day of reinnervation, there was perisynaptic outgrowth in both young and old mice, although in the latter, there was a higher incidence of aberrant outgrowth. The relation between return of twitch strength and recovery of nerve terminal area (measured in teased zinc iodide-stained preparations) showed no age dependency. We conclude that factors cited to explain altered reactive sprouting in the aging CNS do not apply to regeneration of peripheral motor nerve terminals. However, it is possible that the aberrant regrowth observed at the neuromuscular junction in old mice will pertain to the aging CNS. Altered axonal rather than nerve terminal regeneration is the likely source of delayed peripheral nerve regeneration in old animals. PMID:2288242

  13. Interaction of nanoparticles of ferric oxide with brain nerve terminals and blood platelets

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Krisanova, Natalia; Sivko, Roman; Borisov, Arseniy

    2012-07-01

    Nanoparticles of ferric oxide are the components of Lunar and Martian soil simulants. The observations suggest that exposure to Lunar soli simulant can be deleterious to human physiology and the components of lunar soil may be internalized by lung epithelium and may overcome the blood-brain barrier. The study focused on the effects of nanoparticles of ferric oxide on the functional state of rat brain nerve terminals (synaptosomes) and rabbit blood platelets. Using photon correlation spectroscopy, we demonstrated the binding of nanoparticles of ferric oxide with nerve terminals and platelets. Nanoparticles did not depolarize the plasma membrane of nerve terminals and platelets that was shown by fluorimetry with potential-sensitive fluorescent dye rhodamine 6G. Using pH-sensitive fluorescent dye acridine orange, we revealed that the acidification of synaptic vesicles of nerve terminals and secretory granules of platelets did not change in the presence of nanoparticles. The initial velocity of uptake of excitatory neurotransmitter glutamate was not influenced by nanoparticles of ferric oxide, whereas glutamate binding to nerve terminals was altered. Thus, it was suggested that nanoparticles of ferric oxide might disturb glutamate transport in the mammalian CNS.

  14. Opposing actions of 5HT1A and 5HT2-like serotonin receptors on modulations of the electric signal waveform in the electric fish Brachyhypopomus pinnicaudatus

    PubMed Central

    Allee, Susan J.; Markham, Michael R.; Salazar, Vielka L.; Stoddard, Philip K.

    2008-01-01

    Serotonin (5-HT) is an indirect modulator of the electric organ discharge (EOD) in the weakly electric gymnotiform fish, Brachyhypopomus pinnicaudatus. Injections of 5-HT enhance EOD waveform “masculinity”, increasing both waveform amplitude and the duration of the second phase. This study investigated the pharmacological identity of 5-HT receptors that regulate the electric waveform and their effects on EOD amplitude and duration. We present evidence that two sets of serotonin receptors modulate the EOD in opposite directions. We found that the 5HT1AR agonist 8-OH-DPAT diminishes EOD duration and amplitude while the 5HT1AR antagonist WAY100635 increases these parameters. In contrast, the 5HT2R agonist α-Me-5-HT increases EOD amplitude but not duration, yet 5-HT-induced increases in EOD duration can be inhibited by blocking 5HT2A/2C-like receptors with ketanserin. These results show that 5-HT exerts bi-directional control of EOD modulations in B. pinnicaudatus via action at receptors similar to mammalian 5HT1A and 5HT2 receptors. The discordant amplitude and duration response suggests separate mechanisms for modulating these waveform parameters. PMID:18206154

  15. Long-term Stress with Hyperglucocorticoidemia-induced Hepatic Steatosis with VLDL Overproduction Is Dependent on both 5-HT2 Receptor and 5-HT Synthesis in Liver

    PubMed Central

    Fu, Jihua; Ma, Shaoxin; Li, Xin; An, Shanshan; Li, Tao; Guo, Keke; Lin, Min; Qu, Wei; Wang, Shanshan; Dong, Xinyue; Han, Xiaoyu; Fu, Ting; Huang, Xinping; Wang, Tianying; He, Siyu

    2016-01-01

    Hepatic triglycerides production and adipose lipolysis are pivotal for long-term stress (LTS) or hyperglucocorticoidemia-induced insulin resistance. 5-hydroxytryptamine (5-HT) has been demonstrated to induce hepatic lipid metabolic abnormality by activating mammalian target of rapamycin (mTOR). In present study, we explored whether 5-HT is involved in LTS effects in liver using restraint stress-exposed rats and cultured primary rat hepatocytes and HepG2 cells. LTS with hyperglucocorticoidemia induced hepatic 5-HT synthetic increase with tryptophan hydroxylase 1 (Tph1) up-regulation, and 5-HT2 receptor (5-HT2R, including 5-HT2A, 2B receptor) up-regulation in liver and visceral adipose, as well as hepatic mTOR activation with triglycerides and VLDL overproduction with steatosis, and visceral adipose lipolytic increase with high blood free fatty acids (FFAs) level. 5-HT exposure exhibited LTS-like effects in both tissues, and both LTS and 5-HT effects could be abolished significantly by blocking 5-HT2R. In HepG2 cells dexamethasone or palmitate-induced mTOR activation with triglycerides and VLDL overproduction were accompanied by up-regulations of 5-HT synthesis and 5-HT2R, which were significantly abolished by gene silencing Tph1 or 5-HT2R and were almost fully abolished by co-silencing of both, especially on VLDL overproduction. Chemical inhibition of Tph1 or/and 5-HT2R in both hepatocytes exhibited similar abolishment with genetic inhibition on dexamethason-induced effects. 5-HT-stimulated effects in both hepatocytes were fully abolished by blocking 5-HT2R, while 5-HT itself also up-regulated 5-HT2R. In conclusion, up-regulated hepatic 5-HT synthesis and 5-HT2R induced by both glucocorticoid and FFAs are crucial for LTS-induced hepatic steatosis with VLDL overproduction, while 5-HT by acting on 5-HT2R mediates mTOR activation in liver. PMID:26884719

  16. The human serotonin 5-HT{sub 2C} receptor: Complete cDNA, genomic structure, and alternatively spliced variant

    SciTech Connect

    Xie, Enzhong; Zhu, Lingyu; Zhao, Lingyun

    1996-08-01

    The complete 4775-nt cDNA encoding the human serotonin 5-HT{sub 2C} receptor (5-HT{sub 2C}R), a G-protein-coupled receptor, has been isolated. It contains a 1377-nt coding region flanked by a 728-nt 5{prime}-untranslated region and a 2670-nt 3{prime}-untranslated region. By using the cloned 5-HT{sub 2C}R cDNA probe, the complete human gene for this receptor has been isolated and shown to contain six exons and five introns spanning at least 230 kb of DNA. The coding region of the human 5-HT{sub 2C}R gene is interrupted by three introns, and the positions of the intron/exon junctions are conserved between the human and the rodent genes. In addition, an alternatively spliced 5-HT{sub 2C}R RNA that contains a 95-nt deletion in the region coding for the second intracellular loop and the fourth transmembrane domain of the receptor has been identified. This deletion leads to a frameshift and premature termination so that the short isoform RNA encodes a putative protein of 248 amino acids. The ratio for the short isoform over the 5-HT{sub 2C}R RNA was found to be higher in choroid plexus tumor than in normal brain tissue, suggesting the possibility of differential regulation of the 5-HT{sub 2C}R gene in different neural tissues or during tumorigenesis. Transcription of the human 5-HT{sub 2C}R gene was found to be initiated at multiple sites. No classical TATA-box sequence was found at the appropriate location, and the 5{prime}-flanking sequence contains many potential transcription factor-binding sites. A 7.3-kb 5{prime}-flanking 5-HT{sub 2C}R DNA directed the efficient expression of a luciferase reported gene in SK-N-SH and IMR32 neuroblastoma cells, indicating that is contains a functional promoter. 69 refs., 8 figs., 1 tab.

  17. Rapid loss of motor nerve terminals following hypoxia–reperfusion injury occurs via mechanisms distinct from classic Wallerian degeneration

    PubMed Central

    Baxter, Becki; Gillingwater, Thomas H; Parson, Simon H

    2008-01-01

    Motor nerve terminals are known to be vulnerable to a wide range of pathological stimuli. To further characterize this vulnerability, we have developed a novel model system to examine the response of mouse motor nerve terminals in ex vivo nerve/muscle preparations to 2 h hypoxia followed by 2 h reperfusion. This insult induced a rapid loss of neurofilament and synaptic vesicle protein immunoreactivity at pre-synaptic motor nerve terminals but did not appear to affect post-synaptic endplates or muscle fibres. The severity of nerve terminal loss was dependent on the age of the mouse and muscle type: in 8–12-week-old mice the predominantly fast-twitch lumbrical muscles showed an 82.5% loss, whereas the predominantly slow-twitch muscles transversus abdominis and triangularis sterni showed a 57.8% and 27.2% loss, respectively. This was contrasted with a > 97% loss in the predominantly slow-twitch muscles from 5–6-week-old mice. We have also demonstrated that nerve terminal loss occurs by a mechanism distinct from Wallerian degeneration, as the slow Wallerian degeneration (Wlds) gene did not modify the extent of nerve terminal pathology. Together, these data show that our new model of hypoxia–reperfusion injury is robust and repeatable, that it induces rapid, quantitative changes in motor nerve terminals and that it can be used to further examine the mechanisms regulating nerve terminal vulnerability in response to hypoxia–reperfusion injury. PMID:18510509

  18. Evidence for 5-HT1-like receptor-mediated vasoconstriction in human pulmonary artery.

    PubMed Central

    MacLean, M. R.; Clayton, R. A.; Templeton, A. G.; Morecroft, I.

    1996-01-01

    1. The 5-hydroxytryptamine (5-HT) receptors mediating contraction of human isolated pulmonary artery rings were investigated. Responses to the agonists 5-carboximidotryptamine (5-CT, non-selective 5-HT1 agonist), sumatriptan (5-HT1D-like receptor agonist), 5-HT and 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT, 5-HT1A receptor agonist) were studied. Responses to 5-HT and sumatriptan in the presence of the antagonists, methiothepin (non-selective 5-HT1+2-receptor antagonist), ketanserin (5-HT2A receptor antagonist) and the novel antagonist, GR55562 (5-HT1D receptor antagonist) were also studied. 2. All agonists contracted human pulmonary artery ring preparations in the following order of potency 5-CT > 5-HT = sumatriptan > 8-OH-DPAT. Maximum responses to 5-HT, 5-CT and sumatriptan were not significantly different. 3. Methiothepin 1 nM and 10 nM, but not 0.1 nM reduced the maximum contractile responses to 5-HT but did not alter tissue sensitivity to 5-HT. Methiothepin 0.1 nM, 1 nM and 10 nM had a similar effect on responses to sumatriptan. 4. The 5-HT2A receptor antagonist ketanserin (10 nM, 100 nM and 1 microM) also reduced the maximum contractile response to both 5-HT and sumatriptan without affecting tissue sensitivity to these agonists. 5. The novel 5-HT1D receptor antagonist, GR55562, inhibited responses to 5-HT and sumatriptan in a true competitive fashion. 6. The results suggest that the human pulmonary artery has a functional population of 5-HT1D-like receptors which are involved in the contractile response to 5-HT. PMID:8886409

  19. The 5-HT1A receptor in Major Depressive Disorder.

    PubMed

    Kaufman, Joshua; DeLorenzo, Christine; Choudhury, Sunia; Parsey, Ramin V

    2016-03-01

    Major Depressive Disorder (MDD) is a highly prevalent psychiatric diagnosis that is associated with a high degree of morbidity and mortality. This debilitating disorder is currently one of the leading causes of disability nationwide and is predicted to be the leading cause of disease burden by the year 2030. A large body of previous research has theorized that serotonergic dysfunction, specifically of the serotonin (5-HT) 1A receptor, plays a key role in the development of MDD. The purpose of this review is to describe the evolution of our current understanding of the serotonin 1A (5-HT1A) receptor and its role in the pathophysiology MDD through the discussion of animal, post-mortem, positron emission tomography (PET), pharmacologic and genetic studies. PMID:26851834

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

    PubMed Central

    Fassio, Anna; Fadda, Manuela; Benfenati, Fabio

    2016-01-01

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

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

    PubMed

    Fassio, Anna; Fadda, Manuela; Benfenati, Fabio

    2016-01-01

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

  2. The serotonin 5-HT7 receptors: two decades of research.

    PubMed

    Gellynck, Evelien; Heyninck, Karen; Andressen, Kjetil W; Haegeman, Guy; Levy, Finn Olav; Vanhoenacker, Peter; Van Craenenbroeck, Kathleen

    2013-10-01

    Like most neurotransmitters, serotonin possesses a simple structure. However, the pharmacological consequences are more complex and diverse. Serotonin is involved in numerous functions in the human body including the control of appetite, sleep, memory and learning, temperature regulation, mood, behavior, cardiovascular function, muscle contraction, endocrine regulation, and depression. Low levels of serotonin may be associated with several disorders, namely increase in aggressive and angry behaviors, clinical depression, Parkinson's disease, obsessive-compulsive disorder, eating disorders, migraine, irritable bowel syndrome, tinnitus, and bipolar disease. These effects are mediated via different serotonin (5-HT) receptors. In this review, we will focus on the last discovered member of this serotonin receptor family, the 5-HT7 receptor. This receptor belongs to the G protein-coupled receptor superfamily and was cloned two decades ago. Later, different splice variants were described but no major functional differences have been described so far. All 5-HT7 receptor variants are coupled to Gαs proteins and stimulate cAMP formation. Recently, several interacting proteins have been reported, which can influence receptor signaling and trafficking. PMID:24042216

  3. The 5-HT4 receptor: molecular cloning and pharmacological characterization of two splice variants.

    PubMed Central

    Gerald, C; Adham, N; Kao, H T; Olsen, M A; Laz, T M; Schechter, L E; Bard, J A; Vaysse, P J; Hartig, P R; Branchek, T A

    1995-01-01

    Molecular cloning efforts have provided primary amino acid sequence and signal transduction data for a large collection of serotonin receptor subtypes. These include five 5-HT1-like receptors, three 5-HT2 receptors, one 5-HT3 receptor, two 5-HT5 receptors, one 5-HT6 receptor and one 5-HT7 receptor. Molecular biological information on the 5-HT4 receptor is notably absent from this list. We now report the cloning of the pharmacologically defined 5-HT4 receptor. Using degenerate oligonucleotide primers, we identified a rat brain PCR fragment which encoded a '5-HT receptor-like' amino acid sequence. The corresponding full length cDNA was isolated from a rat brain cDNA library. Transiently expressed in COS-7 cells, this receptor stimulates adenylyl cyclase activity and is sensitive to the benzamide derivative cisapride. The response is also blocked by ICS-205930. Interestingly, we isolated two splice variants of the receptor, 5-HT4L and 5-HT4S, differing in the length and sequence of their C-termini. In rat brain, the 5-HT4S transcripts are restricted to the striatum, but the 5-HT4L transcripts are expressed throughout the brain, except in the cerebellum where it was barely detectable. In peripheral tissues, differential expression was also observed in the atrium of the heart where only the 5-HT4S isoform was detectable. Images PMID:7796807

  4. Repetitive Nerve Stimulation Transiently Opens the Mitochondrial Permeability Transition Pore in Motor Nerve Terminals of Symptomatic Mutant SOD1 Mice

    PubMed Central

    Nguyen, Khanh T.; Barrett, John N.; García-Chacón, Luis; David, Gavriel; Barrett, Ellen F.

    2011-01-01

    Mitochondria in motor nerve terminals temporarily sequester large Ca2+ loads during repetitive stimulation. In wild-type mice this Ca2+ uptake produces a small (<5 mV), transient depolarization of the mitochondrial membrane potential (Ψm, motor nerve stimulated with at 100 Hz for 5 s). We demonstrate that this stimulation-induced Ψm depolarization attains much higher amplitudes in motor terminals of symptomatic mice expressing the G93A or G85R mutation of human superoxide dismutase 1 (SOD1), models of familial amyotrophic lateral sclerosis (fALS). These large Ψm depolarizations decayed slowly and incremented with successive stimulus trains. Additional Ψm depolarizations occurred that were not synchronized with stimulation. These large Ψm depolarizations were reduced (a) by cyclosporin A (CsA, 1-2 uM), which inhibits opening of the mitochondrial permeability transition pore (mPTP), or (b) by replacing bath Ca2+ with Sr2+, which enters motor terminals and mitochondria but does not support mPTP opening. These results are consistent with the hypothesis that the large Ψm depolarizations evoked by repetitive stimulation in motor terminals of symptomatic fALS mice result from mitochondrial dysfunction that increases the likelihood of transient mPTP opening during Ca2+ influx. Such mPTP openings, a sign of mitochondrial stress, would disrupt motor terminal handling of Ca2+ loads and might thereby contribute to motor terminal degeneration in fALS mice. Ψm depolarizations resembling those in symptomatic fALS mice could be elicited in wild-type mice following 0.5-1 hr exposure to diamide (200 μM), which produces an oxidative stress, but these depolarizations were not reduced by CsA. PMID:21310237

  5. Repetitive nerve stimulation transiently opens the mitochondrial permeability transition pore in motor nerve terminals of symptomatic mutant SOD1 mice.

    PubMed

    Nguyen, Khanh T; Barrett, John N; García-Chacón, Luis; David, Gavriel; Barrett, Ellen F

    2011-06-01

    Mitochondria in motor nerve terminals temporarily sequester large Ca(2+) loads during repetitive stimulation. In wild-type mice this Ca(2+) uptake produces a small (<5 mV), transient depolarization of the mitochondrial membrane potential (Ψ(m), motor nerve stimulated at 100 Hz for 5s). We demonstrate that this stimulation-induced Ψ(m) depolarization attains much higher amplitudes in motor terminals of symptomatic mice expressing the G93A or G85R mutation of human superoxide dismutase 1 (SOD1), models of familial amyotrophic lateral sclerosis (fALS). These large Ψ(m) depolarizations decayed slowly and incremented with successive stimulus trains. Additional Ψ(m) depolarizations occurred that were not synchronized with stimulation. These large Ψ(m) depolarizations were reduced (a) by cyclosporin A (CsA, 1-2 μM), which inhibits opening of the mitochondrial permeability transition pore (mPTP), or (b) by replacing bath Ca(2+) with Sr(2+), which enters motor terminals and mitochondria but does not support mPTP opening. These results are consistent with the hypothesis that the large Ψ(m) depolarizations evoked by repetitive stimulation in motor terminals of symptomatic fALS mice result from mitochondrial dysfunction that increases the likelihood of transient mPTP opening during Ca(2+) influx. Such mPTP openings, a sign of mitochondrial stress, would disrupt motor terminal handling of Ca(2+) loads and might thereby contribute to motor terminal degeneration in fALS mice. Ψ(m) depolarizations resembling those in symptomatic fALS mice could be elicited in wild-type mice following a 0.5-1h exposure to diamide (200 μM), which produces an oxidative stress, but these depolarizations were not reduced by CsA. PMID:21310237

  6. Autonomic nerves terminating on microvessels in the pineal organs of various submammalian vertebrates.

    PubMed

    Frank, C L; Czirok, Szabina J; Vincze, Csilla; Rácz, G; Szél, A; Vígh, B

    2005-01-01

    In earlier works we have found that in the mammalian pineal organ, a part of autonomic nerves--generally thought to mediate light information from the retina--form vasomotor endings on smooth muscle cells of vessels. We supposed that they serve the vascular support for circadian and circannual periodic changes in the metabolic activity of the pineal tissue. In the present work, we investigated whether peripheral nerves present in the photoreceptive pineal organs of submammalians form similar terminals on microvessels. In the cyclostome, fish, amphibian, reptile and bird species investigated, autonomic nerves accompany vessels entering the arachnoidal capsule and interfollicular meningeal septa of the pineal organ. The autonomic nerves do not enter the pineal tissue proper but remain in the perivasal meningeal septa isolated by basal lamina. They are composed of unmyelinated and myelinated fibers and form terminals around arterioles, veins and capillaries. The terminals contain synaptic and granular vesicles. Comparing various vertebrates, more perivasal terminals were found in reptiles and birds than in the cyclostome, fish and amphibian pineal organs. Earlier, autonomic nerves of the pineal organs were predominantly investigated in connection with the innervation of pineal tissue. The perivasal terminals found in various submammalians show that a part of the pineal autonomic fibers are vasomotoric in nature, but the vasosensor function of some fibers cannot be excluded. We suppose that the vasomotor regulation of the pineal microvessels in the photosensory submamalian pineal--like in mammals--may serve the vascular support for circadian and circannual periodic changes in the metabolic activity of the pineal tissue. The higher number of perivasal terminals in reptiles and birds may correspond to the higher metabolic activity of the tissues in more differentiated species. PMID:15813212

  7. 5-HT induces temporomandibular joint nociception in rats through the local release of inflammatory mediators and activation of local β adrenoceptors.

    PubMed

    Oliveira-Fusaro, Maria Cláudia G; Clemente-Napimoga, Juliana Trindade; Teixeira, Juliana Maia; Torres-Chávez, Karla Elena; Parada, Carlos Amílcar; Tambeli, Cláudia Herrera

    2012-09-01

    The 5-hydroxytryptamine (serotonin, 5-HT) is an important inflammatory mediator found in high levels in the synovial fluid of the temporomandibular joint (TMJ) of patients with inflammatory pain. In this study, we used the nociceptive behavior responses, measured as flinching the head and rubbing the orofacial region, as a nociceptive assay. We demonstrated that the local blockade of the 5-HT₃ receptor and β₁ or β₂-adrenoceptors, the depletion of norepinephrine in the sympathetic terminals and the local inhibition of cyclooxygenase significantly reduced 5-HT-induced TMJ nociception. These results demonstrated that 5-HT induces nociception in the TMJ region by the activation of β₁ and β₂ adrenoceptors located in the TMJ region and local release of sympathetic amines and prostaglandins. Therefore, the high levels of 5-HT in the synovial fluid of patients with TMJ inflammatory pain may contribute to TMJ pain by similar mechanisms. PMID:22683622

  8. Participation of 5-HT1-like and 5-HT2A receptors in the contraction of human temporal artery by 5-hydroxytryptamine and related drugs.

    PubMed Central

    Verheggen, R.; Freudenthaler, S.; Meyer-Dulheuer, F.; Kaumann, A. J.

    1996-01-01

    1. We investigated the hypothesis that, as in some other large human arteries, 5-HT-induced contraction of the temporal artery is mediated through two co-existing receptor populations, 5-HT1-like- and 5-HT2A. Temporal arterial segments were obtained from patients undergoing brain surgery and rings prepared set up to contract with 5-HT and related agents. Fractions of maximal 5-HT responses mediated through 5-HT1-like and 5-HT2A receptors, f1 and f2 = 1-f1, were estimated by use of the 5-HT2A-selective antagonist ketanserin. 2. In rings with intact endothelium 5-HT evoked contractions with a -log EC50, M of 7.0. Ketanserin (10-1000 nM) antagonized part of the 5-HT-induced contractions. Ketanserin-resistant components of 5-HT-induced contractions were found with -log EC50, M of 6.9 and f1 of 0.17 (100 nM ketanserin) and -log EC50, M of 6.4 and f1 of 0.20 (1000 nM ketanserin). 3. In rings with endothelial function attenuated by enzymatic treatment, 5-HT caused contractions with a -log EC50, M of 7.2 that were partially blocked by ketanserin. Ketanserin-resistant components of 5-HT-induced contractions were found with -log EC50, M 7.4 and f1 of 0.16 (100 nM ketanserin) and -log EC50, M of 7.5 and f1 of 0.14 (1000 nM ketanserin). 4. The ketanserin-resistant component of 5-HT-evoked contraction was blocked by methiothepin (100-1000 nM) consistent with mediation through 5-HT1-like receptors. 5. In rings with intact endothelium the 5-HT1-like-selective agonist, sumatriptan, caused small contractions with a -log EC50, M of 6.5 and intrinsic activity of 0.21 with respect to 5-HT that were resistant to blockade by 1000 nM ketanserin but antagonized by 100 nM methiothepin. 6. In rings with intact endothelium the 5-HT2A receptor partial agonist SK&F 103829 (2,3,4,5-tetrahydro-8[methyl sulphonyl]-1H3-benzazepin-7-ol methensulphonate) contracted rings with a -log EC50, M of 5.0 and an intrinsic activity of 0.49 with respect to 5-HT; the effects were antagonized by ketanserin 1000

  9. GR-127935-sensitive mechanism mediating hypotension in anesthetized rats: are 5-HT5B receptors involved?

    PubMed

    Sánchez-Maldonado, Carolina; López-Sánchez, Pedro; Anguiano-Robledo, Liliana; Leopoldo, Marcello; Lacivita, Enza; Terrón, José A

    2015-04-01

    The 5-HT1B/1D receptor antagonist, GR-127935, inhibits hypotensive responses produced by the 5-HT1A, 5-HT1B/1D and 5-HT7 receptor agonist, and 5-HT5A/5B receptor ligand, 5-carboxamidotryptamine (5-CT), in rats. This work further characterized the above mechanism using more selective 5-HT1B and 5-HT1D receptor antagonists. Also, expression of 5-HT5A and 5-HT5B receptor mRNAs in blood vessels was searched by reverse transcription polymerase chain reaction. Decreases in diastolic blood pressure induced by 5-CT (0.001-10 μg/kg, intravenously) were analyzed in anesthetized rats that had received intravenous vehicle (1 mL/kg), SB-224289 (5-HT1B antagonist; 0.3 and 1.0 mg/kg), BRL15572 (5-HT1D antagonist; 0.3 and 1.0 mg/kg), SB-224289 + BRL15572 (0.3 mg/kg, each), or SB-224289 + BRL15572 (0.3 mg/kg, each) + GR-127935 (1 mg/kg). Because only the latter treatment inhibited 5-CT-induced hypotension, suggestive of a mechanism unrelated to 5-HT1B/1D receptors, the effects of antagonists/ligands at 5-HT5A (SB-699551, 1 mg/kg), 5-HT6 (SB-399885, 1 mg/kg), and 5-HT1B/1D/5A/5B/7 receptors (ergotamine, 0.1 mg/kg) on 5-CT-induced hypotension were tested. Interestingly, only ergotamine blocked 5-CT-induced responses; this effect closely paralleled that of SB-224289 + BRL-15572 + GR-127935. Neither did ergotamine nor GR-127935 inhibit hypotensive responses induced by the 5-HT7 receptor agonist, LP-44. Faint but clear bands corresponding to 5-HT5A and 5-HT5B receptor mRNAs in aorta and mesenteric arteries were detected. Results suggest that the GR-127935-sensitive mechanism mediating hypotension in rats is unrelated to 5-HT1B, 5-HT1D, 5-HT5A, 5-HT6, and 5-HT7 receptors. This mechanism, however, resembles putative 5-HT5B receptors. PMID:25502305

  10. Serotonin (5-HT) 2C Receptor (5-HT2CR) Protein Expression is Enriched in Synaptosomal and Postsynaptic Compartments of Rat Cortex

    PubMed Central

    Anastasio, Noelle C.; Lanfranco, Maria Fe; Bubar, Marcy J.; Seitz, Patricia K.; Stutz, Sonja J.; McGinnis, Andrew G.; Watson, Cheryl S.; Cunningham, Kathryn A.

    2010-01-01

    The action of serotonin (5-HT) at the 5-HT2C receptor (5-HT2CR) in cerebral cortex is emerging as a candidate modulator of neural processes that mediate core phenotypic facets of several psychiatric and neurological disorders. However, our understanding of the neurobiology of the cortical 5-HT2CR protein complex is currently limited. The goal of the present study was to explore the subcellular localization of the 5-HT2CR in synaptosomes and the postsynaptic density, an electron-dense thickening specialized for postsynaptic signaling and neuronal plasticity. Utilizing multiples tissues (brain, peripheral tissues), protein fractions (synaptosomal, postsynaptic density), and controls (peptide neutralization, 5-HT2CR stable-expressing cells), we established the selectivity of two commercially available 5-HT2CR antibodies and employed the antibodies in Western blot and immunoprecipitation studies of PFC and motor cortex, two regions implicated in cognitive, emotional and motor dysfunction. For the first time, we demonstrated the expression of the 5-HT2CR in postsynaptic density-enriched fractions from both PFC and motor cortex. Co-immunoprecipitation studies revealed the presence of PSD-95 within the 5-HT2CR protein complex expressed in PFC and motor cortex. Taken together, these data support the hypothesis that the 5-HT2CR is localized within the postsynaptic thickening of synapses and is therefore positioned to directly modulate synaptic plasticity in cortical neurons. PMID:20345755

  11. Genotype-Dependent Difference in 5-HT2C Receptor-Induced Hypolocomotion: Comparison with 5-HT2A Receptor Functional Activity

    PubMed Central

    Bazovkina, Darya V.; Kondaurova, Elena M.; Naumenko, Vladimir S.; Ponimaskin, Evgeni

    2015-01-01

    In the present study behavioral effects of the 5-HT2C serotonin receptor were investigated in different mouse strains. The 5-HT2C receptor agonist MK-212 applied intraperitoneally induced significant dose-dependent reduction of distance traveled in the open field test in CBA/Lac mice. This effect was receptor-specific because it was inhibited by the 5-HT2C receptor antagonist RS102221. To study the role of genotype in 5-HT2C receptor-induced hypolocomotion, locomotor activity of seven inbred mouse strains was measured after MK-212 acute treatment. We found that the 5-HT2C receptor stimulation by MK-212 decreased distance traveled in the open field test in CBA/Lac, C57Bl/6, C3H/He, and ICR mice, whereas it failed to affect locomotor activity in DBA/2J, Asn, and Balb/c mice. We also compared the interstrain differences in functional response to 5-HT2C and 5-HT2A receptors activation measured by the quantification of receptor-mediated head-twitches. These experiments revealed significant positive correlation between 5-HT2C and 5-HT2A receptors functional responses for all investigated mouse strains. Moreover, we found that 5-HT2A receptor activation with DOI did not change locomotor activity in CBA/Lac mice. Taken together, our data indicate the implication of 5-HT2C receptors in regulation of locomotor activity and suggest the shared mechanism for functional responses mediated by 5-HT2C and 5-HT2A receptors. PMID:26380122

  12. Effects of ginger constituents on the gastrointestinal tract: role of cholinergic M3 and serotonergic 5-HT3 and 5-HT4 receptors.

    PubMed

    Pertz, Heinz H; Lehmann, Jochen; Roth-Ehrang, René; Elz, Sigurd

    2011-07-01

    The herbal drug ginger (Zingiber officinale Roscoe) may be effective for treating nausea, vomiting, and gastric hypomotility. In these conditions, cholinergic M (3) receptors and serotonergic 5-HT (3) and 5-HT (4) receptors are involved. The major chemical constituents of ginger are [6]-gingerol, [8]-gingerol, [10]-gingerol, and [6]-shogaol. We studied the interaction of [6]-gingerol, [8]-gingerol, [10]-gingerol (racemates), and [6]-shogaol with guinea pig M (3) receptors, guinea pig 5-HT (3) receptors, and rat 5-HT (4) receptors. In whole segments of guinea pig ileum (bioassay for contractile M (3) receptors), [6]-gingerol, [8]-gingerol, [10]-gingerol, and [6]-shogaol slightly but significantly depressed the maximal carbachol response at an antagonist concentration of 10 µM. In the guinea pig myenteric plexus preparation (bioassay for contractile 5-HT (3) receptors), 5-HT maximal responses were depressed by [10]-gingerol from 93 ± 3 % to 65 ± 6 % at an antagonist concentration of 3 µM and to 48 ± 3 % at an antagonist concentration of 5 µM following desensitization of 5-HT (4) receptors and blockade of 5-HT (1) and 5-HT (2) receptors. [6]-Shogaol (3 µM) induced depression to 61 ± 3 %. In rat esophageal tunica muscularis mucosae (bioassay for relaxant 5-HT (4) receptors), [6]-gingerol, [8]-gingerol, [10]-gingerol, and [6]-shogaol (2-6.3 µM) showed no agonist effects. The maximal 5-HT response remained unaffected in the presence of the compounds. It is concluded that the efficiency of ginger in reducing nausea and vomiting may be based on a weak inhibitory effect of gingerols and shogaols at M (3) and 5-HT (3) receptors. 5-HT (4) receptors, which play a role in gastroduodenal motility, appear not to be involved in the action of these compounds. PMID:21305447

  13. Role for serotonin2A (5-HT2A) and 2C (5-HT2C) receptors in experimental absence seizures.

    PubMed

    Venzi, Marcello; David, François; Bellet, Joachim; Cavaccini, Anna; Bombardi, Cristiano; Crunelli, Vincenzo; Di Giovanni, Giuseppe

    2016-09-01

    Absence seizures (ASs) are the hallmark of childhood/juvenile absence epilepsy. Monotherapy with first-line anti-absence drugs only controls ASs in 50% of patients, indicating the need for novel therapeutic targets. Since serotonin family-2 receptors (5-HT2Rs) are known to modulate neuronal activity in the cortico-thalamo-cortical loop, the main network involved in AS generation, we investigated the effect of selective 5-HT2AR and 5-HT2CR ligands on ASs in the Genetic Absence Epilepsy Rats from Strasbourg (GAERS), a well established polygenic rat model of these non-convulsive seizures. GAERS rats were implanted with fronto-parietal EEG electrodes under general anesthesia, and their ASs were later recorded under freely moving conditions before and after intraperitoneal administration of various 5-HT2AR and 5-HT2CR ligands. The 5-HT2A agonist TCB-2 dose-dependently decreased the total time spent in ASs, an effect that was blocked by the selective 5-HT2A antagonist MDL11,939. Both MDL11,939 and another selective 5-HT2A antagonist (M100,907) increased the length of individual seizures when injected alone. The 5-HT2C agonists lorcaserin and CP-809,101 dose-dependently suppressed ASs, an effect blocked by the selective 5-HT2C antagonist SB 242984. In summary, 5-HT2ARs and 5-HT2CRs negatively control the expression of experimental ASs, indicating that selective agonists at these 5-HT2R subtypes might be potential novel anti-absence drugs. PMID:27085605

  14. Genotype-Dependent Difference in 5-HT2C Receptor-Induced Hypolocomotion: Comparison with 5-HT2A Receptor Functional Activity.

    PubMed

    Bazovkina, Darya V; Kondaurova, Elena M; Naumenko, Vladimir S; Ponimaskin, Evgeni

    2015-01-01

    In the present study behavioral effects of the 5-HT2C serotonin receptor were investigated in different mouse strains. The 5-HT2C receptor agonist MK-212 applied intraperitoneally induced significant dose-dependent reduction of distance traveled in the open field test in CBA/Lac mice. This effect was receptor-specific because it was inhibited by the 5-HT2C receptor antagonist RS102221. To study the role of genotype in 5-HT2C receptor-induced hypolocomotion, locomotor activity of seven inbred mouse strains was measured after MK-212 acute treatment. We found that the 5-HT2C receptor stimulation by MK-212 decreased distance traveled in the open field test in CBA/Lac, C57Bl/6, C3H/He, and ICR mice, whereas it failed to affect locomotor activity in DBA/2J, Asn, and Balb/c mice. We also compared the interstrain differences in functional response to 5-HT2C and 5-HT2A receptors activation measured by the quantification of receptor-mediated head-twitches. These experiments revealed significant positive correlation between 5-HT2C and 5-HT2A receptors functional responses for all investigated mouse strains. Moreover, we found that 5-HT2A receptor activation with DOI did not change locomotor activity in CBA/Lac mice. Taken together, our data indicate the implication of 5-HT2C receptors in regulation of locomotor activity and suggest the shared mechanism for functional responses mediated by 5-HT2C and 5-HT2A receptors. PMID:26380122

  15. The opposite effect of a 5-HT1B receptor agonist on 5-HT synthesis, as well as its resistant counterpart, in an animal model of depression

    PubMed Central

    Skelin, Ivan; Kovačević, Tomislav; Sato, Hiroki; Diksic, Mirko

    2013-01-01

    Flinders Sensitive Line (FSL) rat is as an animal model of depression with altered parameters of the serotonergic (5-HT) system function (5-HT synthesis rates, tissue concentrations, release, receptor density and affinity), as well as an altered sensitivity of these parameters to different 5-HT based antidepressants. The effects of acute and chronic treatments with the 5-HT1B agonist, CP-94253 on 5-HT synthesis, in the FSL rats and the Flinders Resistant Line (FRL) controls were measured using α-[14C]methyl-L-tryptophan (α-MTrp) autoradiography. CP-94253 (5 mg/kg), or an adequate volume of saline, was injected i.p. as a single dose in the acute experiment or delivered via the subcutaneously implanted osmotic minipump (5 mg/kg/day for 14 days) in the chronic experiment. The acute treatment with CP-94253 significantly decreased the 5-HT synthesis in both the FRL and FSL rats, with a more widespread effect in the FRL rats. Chronic treatment with CP-94253 significantly decreased 5-HT synthesis in the FRL rats, while 5-HT synthesis in the FSL rats was significantly increased throughout the brain. In both the acute and chronic experiment, the FRL rats had higher brain 5-HT synthesis rates, relative to the FSL rats. The shift in the direction of the treatment effect from acute to chronic, using the 5-HT1B agonist, CP-94253, on 5-HT synthesis in the FSL model of depression, with an opposite effect on the control FRL rats, suggests the differential adaptation of the 5-HT system in the FSL and FRL rats to chronic stimulation of 5-HT1B receptors. PMID:22542420

  16. Diurnal variation in 5-HT1B autoreceptor function in the anterior hypothalamus in vivo: effect of chronic antidepressant drug treatment

    PubMed Central

    Sayer, Tamsin J O; Hannon, Serina D; Redfern, Peter H; Martin, Keith F

    1999-01-01

    Intracerebral microdialysis was used to examine the function of the terminal 5-hydroxytryptamine (5-HT) autoreceptor in the anterior hypothalamus of anaesthetized rats at two points in the light phase of the light–dark cycle.Infusion of the 5-HT1A/1B agonist 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridyl)-1H-indole (RU24969) 0.1, 1.0 and 10 μM through the microdialysis probe led to a concentration-dependent decrease (49, 56 and 65% respectively) in 5-HT output. The effect of RU24969 (1 and 5 μM) was prevented by concurrent infusion of methiothepin (1 and 10 μM) into the anterior hypothalamus via the microdialysis probe. Infusion of methiothepin alone (1.0 and 10 μM) increased (15 and 142% respectively) 5-HT output.Infusion of RU24969 (5 μM) through the probe at mid-light and end-light resulted in a quantitatively greater decrease in 5-HT output at end-light compared with mid-light.Following treatment with either paroxetine hydrochloride (10 mg kg−1 i.p.) or desipramine hydrochloride (10 mg kg−1 i.p.) for 21 days the function of the terminal 5-HT1B autoreceptor was more markedly attenuated at end-light.The data show that, as defined by the response to RU24969, the function of the 5-HT1B receptors that control 5-HT output in the anterior hypothalamus is attenuated following chronic desipramine or paroxetine treatment in a time-of-day-dependent manner. PMID:10372820

  17. 5-HT2A receptor activation is necessary for CO2-induced arousal.

    PubMed

    Buchanan, Gordon F; Smith, Haleigh R; MacAskill, Amanda; Richerson, George B

    2015-07-01

    Hypercapnia-induced arousal from sleep is an important protective mechanism pertinent to a number of diseases. Most notably among these are the sudden infant death syndrome, obstructive sleep apnea and sudden unexpected death in epilepsy. Serotonin (5-HT) plays a significant role in hypercapnia-induced arousal. The mechanism of 5-HT's role in this protective response is unknown. Here we sought to identify the specific 5-HT receptor subtype(s) involved in this response. Wild-type mice were pretreated with antagonists against 5-HT receptor subtypes, as well as antagonists against adrenergic, cholinergic, histaminergic, dopaminergic, and orexinergic receptors before challenge with inspired CO2 or hypoxia. Antagonists of 5-HT(2A) receptors dose-dependently blocked CO2-induced arousal. The 5-HT(2C) receptor antagonist, RS-102221, and the 5-HT1A receptor agonist, 8-OH-DPAT, attenuated but did not completely block CO2-induced arousal. Blockade of non-5-HT receptors did not affect CO2-induced arousal. None of these drugs had any effect on hypoxia-induced arousal. 5-HT2 receptor agonists were given to mice in which 5-HT neurons had been genetically eliminated during embryonic life (Lmx1b(f/f/p)) and which are known to lack CO2-induced arousal. Application of agonists to 5-HT(2A), but not 5-HT(2C), receptors, dose-dependently restored CO2-induced arousal in these mice. These data identify the 5-HT(2A) receptor as an important mediator of CO2-induced arousal and suggest that, while 5-HT neurons can be independently activated to drive CO2-induced arousal, in the absence of 5-HT neurons and endogenous 5-HT, 5-HT receptor activation can act in a permissive fashion to facilitate CO2-induced arousal via another as yet unidentified chemosensor system. PMID:25925320

  18. 5-HT2A receptor activation is necessary for CO2-induced arousal

    PubMed Central

    Smith, Haleigh R.; MacAskill, Amanda; Richerson, George B.

    2015-01-01

    Hypercapnia-induced arousal from sleep is an important protective mechanism pertinent to a number of diseases. Most notably among these are the sudden infant death syndrome, obstructive sleep apnea and sudden unexpected death in epilepsy. Serotonin (5-HT) plays a significant role in hypercapnia-induced arousal. The mechanism of 5-HT's role in this protective response is unknown. Here we sought to identify the specific 5-HT receptor subtype(s) involved in this response. Wild-type mice were pretreated with antagonists against 5-HT receptor subtypes, as well as antagonists against adrenergic, cholinergic, histaminergic, dopaminergic, and orexinergic receptors before challenge with inspired CO2 or hypoxia. Antagonists of 5-HT2A receptors dose-dependently blocked CO2-induced arousal. The 5-HT2C receptor antagonist, RS-102221, and the 5-HT1A receptor agonist, 8-OH-DPAT, attenuated but did not completely block CO2-induced arousal. Blockade of non-5-HT receptors did not affect CO2-induced arousal. None of these drugs had any effect on hypoxia-induced arousal. 5-HT2 receptor agonists were given to mice in which 5-HT neurons had been genetically eliminated during embryonic life (Lmx1bf/f/p) and which are known to lack CO2-induced arousal. Application of agonists to 5-HT2A, but not 5-HT2C, receptors, dose-dependently restored CO2-induced arousal in these mice. These data identify the 5-HT2A receptor as an important mediator of CO2-induced arousal and suggest that, while 5-HT neurons can be independently activated to drive CO2-induced arousal, in the absence of 5-HT neurons and endogenous 5-HT, 5-HT receptor activation can act in a permissive fashion to facilitate CO2-induced arousal via another as yet unidentified chemosensor system. PMID:25925320

  19. Hippocampal 5-HT1A Receptor and Spatial Learning and Memory

    PubMed Central

    Glikmann-Johnston, Yifat; Saling, Michael M.; Reutens, David C.; Stout, Julie C.

    2015-01-01

    Spatial cognition is fundamental for survival in the topographically complex environments inhabited by humans and other animals. The hippocampus, which has a central role in spatial cognition, is characterized by high concentration of serotonin (5-hydroxytryptamine; 5-HT) receptor binding sites, particularly of the 1A receptor (5-HT1A) subtype. This review highlights converging evidence for the role of hippocampal 5-HT1A receptors in spatial learning and memory. We consider studies showing that activation or blockade of the 5-HT1A receptors using agonists or antagonists, respectively, lead to changes in spatial learning and memory. For example, pharmacological manipulation to induce 5-HT release, or to block 5-HT uptake, have indicated that increased extracellular 5-HT concentrations maintain or improve memory performance. In contrast, reduced levels of 5-HT have been shown to impair spatial memory. Furthermore, the lack of 5-HT1A receptor subtype in single gene knockout mice is specifically associated with spatial memory impairments. These findings, along with evidence from recent cognitive imaging studies using positron emission tomography (PET) with 5-HT1A receptor ligands, and studies of individual genetic variance in 5-HT1A receptor availability, strongly suggests that 5-HT, mediated by the 5-HT1A receptor subtype, plays a key role in spatial learning and memory. PMID:26696889

  20. 5-HT1B receptor modulation of the serotonin transporter in vivo: studies using KO mice.

    PubMed

    Montañez, Sylvia; Munn, Jaclyn L; Owens, W Anthony; Horton, Rebecca E; Daws, Lynette C

    2014-07-01

    The serotonin transporter (SERT) controls the strength and duration of serotonergic neurotransmission by the high-affinity uptake of serotonin (5-HT) from extracellular fluid. SERT is a key target for many psychotherapeutic and abused drugs, therefore understanding how SERT activity and expression are regulated is of fundamental importance. A growing literature suggests that SERT activity is under regulatory control of the 5-HT1B autoreceptor. The present studies made use of mice with a constitutive reduction (5-HT1B+/-) or knockout of 5-HT1B receptors (5-HT1B-/-), as well as mice with a constitutive knockout of SERT (SERT-/-) to further explore the relationship between SERT activity and 5-HT1B receptor expression. High-speed chronoamperometry was used to measure clearance of 5-HT from CA3 region of hippocampus in vivo. Serotonin clearance rate, over a range of 5-HT concentrations, did not differ among 5-HT1B receptor genotypes, nor did [(3)H]cyanoimipramine binding to SERT in this brain region, suggesting that SERT activity is not affected by constitutive reduction or loss of 5-HT1B receptors; alternatively, it might be that other transport mechanisms for 5-HT compensate for loss of 5-HT1B receptors. Consistent with previous reports, we found that the 5-HT1B receptor antagonist, cyanopindolol, inhibited 5-HT clearance in wild-type mice. However, this effect of cyanopindolol was lost in 5-HT1B-/- mice and diminished in 5-HT1B+/- mice, indicating that the 5-HT1B receptor is necessary for cyanopindolol to inhibit 5-HT clearance. Likewise, cyanopindolol was without effect on 5-HT clearance in SERT-/- mice, demonstrating a requirement for the presence of both SERT and 5-HT1B receptors in order for cyanopindolol to inhibit 5-HT clearance in CA3 region of hippocampus. Our findings are consistent with SERT being under the regulatory control of 5-HT1B autoreceptors. Future studies to identify signaling pathways involved may help elucidate novel therapeutic targets for the

  1. Agonist actions of dihydroergotamine at 5-HT2B and 5-HT2C receptors and their possible relevance to antimigraine efficacy

    PubMed Central

    Schaerlinger, B; Hickel, P; Etienne, N; Guesnier, L; Maroteaux, L

    2003-01-01

    The pharmaceutical compound, dihydroergotamine (DHE) is dispensed to prevent and reduce the occurrence of migraine attacks. Although still controversial, the prophylactic effect of this drug is believed to be caused through blockade and/or activation of numerous receptors including serotonin (5-HT) receptors of the 5-HT2 subtype. To elucidate if 5-HT2 receptors (5-HT2Rs) may be involved in DHE prophylactic effect, we performed investigations aimed to determine the respective pharmacological profile of DHE and of its major metabolite 8′-hydroxy-DHE (8′-OH-DHE) at the 5-HT2B and 5-HT2CRs by binding, inositol triphosphate (IP3) or cyclic GMP (cGMP) coupling studies in transfected fibroblasts. DHE and 8′-OH-DHE are competitive compounds at 5-HT2B and 5-HT2CRs. 8′-OH-DHE interaction at (5-HT2BRs) was best fitted by a biphasic competition curve and displayed the highest affinity with a Ki of 5 nM. These two compounds acted as agonists for both receptors in respect to cGMP production with pEC50 of 8.32±0.09 for 8′-OH-DHE at 5-HT2B and 7.83±0.06 at 5-HT2CRs. Knowing that the antimigraine prophylactic effect of DHE is only observed after long-term treatment, we chronically exposed the recombinant cells to DHE and 8′-OH-DHE. The number of 5-HT2BR-binding sites was always more affected than 5-HT2CRs. At 5-HT2BRs, 8′-OH-DHE was more effective than DHE, with an uncoupling that persisted for more than 40 h for IP3 or cGMP. By contrast, the 5-HT2CR coupling was reversible after either treatment. Chronic exposure to 8′-OH-DHE caused a persistent agonist-mediated desensitisation of 5-HT2B, but not 5-HT2CRs. This may be of relevance to therapeutic actions of the compound. PMID:12970106

  2. Mouse motor nerve terminal immunoreactivity to synaptotagmin II during sustained quantal transmitter release.

    PubMed

    Angaut-Petit, D; Juzans, P; Molgó, J; Faille, L; Seagar, M J; Takahashi, M; Shoji-Kasai, Y

    1995-05-29

    An antibody directed against the lumenal NH2-terminus of synaptotagmin II was used to examine the distribution of this vesicular protein either after spontaneous acetylcholine release or after sustained release induced by La3+ or alpha-latrotoxin, in conditions that prevent endocytosis. The detection of the epitope was examined in the presence or absence of Triton X-100. We show that, in resting conditions of transmitter release, permeabilization of nerve terminal membranes is required for obvious detection of synaptotagmin Ii immunoreactivity whereas during sustained rates of quantal release, permeabilization is not necessary. These data indicate that, in the latter conditions, synaptotagmin II is incorporated into the terminal axolemma and its intravesicular domain exposed at the extracellular nerve terminal surface. PMID:7552284

  3. 5-HT6 receptor agonism facilitates emotional learning

    PubMed Central

    Pereira, Marcela; Martynhak, Bruno J.; Andreatini, Roberto; Svenningsson, Per

    2015-01-01

    Serotonin (5-HT) and its receptors play crucial roles in various aspects of mood and cognitive functions. However, the role of specific 5-HT receptors in these processes remains to be better understood. Here, we examined the effects of the selective and potent 5-HT6 agonist (WAY208466) on mood, anxiety and emotional learning in mice. Male C57Bl/6J mice were therefore tested in the forced swim test (FST), elevated plus-maze (EPM), and passive avoidance tests (PA), respectively. In a dose-response experiment, mice were treated intraperitoneally with WAY208466 at 3, 9, or 27 mg/kg and examined in an open field arena open field test (OFT) followed by the FST. 9 mg/kg of WAY208466 reduced immobility in the FST, without impairing the locomotion. Thus, the dose of 9 mg/kg was subsequently used for tests of anxiety and emotional learning. There was no significant effect of WAY208466 in the EPM. In the PA, mice were trained 30 min before the treatment with saline or WAY208466. Two separate sets of animals were used for short term memory (tested 1 h post-training) or long term memory (tested 24 h post-training). WAY208466 improved both short and long term memories, evaluated by the latency to enter the dark compartment, in the PA. The WAY208466-treated animals also showed more grooming and rearing in the light compartment. To better understand the molecular mechanisms and brain regions involved in the facilitation of emotional learning by WAY208466, we studied its effects on signal transduction and immediate early gene expression. WAY208466 increased the levels of phospho-Ser845-GluA1 and phospho-Ser217/221-MEK in the caudate-putamen. Levels of phospho-Thr202/204-Erk1/2 and the ratio mature BDNF/proBDNF were increased in the hippocampus. Moreover, WAY208466 increased c-fos in the hippocampus and Arc expression in both hippocampus and prefrontal cortex (PFC). The results indicate antidepressant efficacy and facilitation of emotional learning by 5-HT6 receptor agonism via

  4. Functional Status of the Serotonin 5-HT2C Receptor (5-HT2CR) Drives Interlocked Phenotypes that Precipitate Relapse-Like Behaviors in Cocaine Dependence

    PubMed Central

    Anastasio, Noelle C; Stutz, Sonja J; Fox, Robert G; Sears, Robert M; Emeson, Ronald B; DiLeone, Ralph J; O'Neil, Richard T; Fink, Latham H; Li, Dingge; Green, Thomas A; Gerard Moeller, F; Cunningham, Kathryn A

    2014-01-01

    Relapse vulnerability in cocaine dependence is rooted in genetic and environmental determinants, and propelled by both impulsivity and the responsivity to cocaine-linked cues (‘cue reactivity'). The serotonin (5-hydroxytryptamine, 5-HT) 5-HT2C receptor (5-HT2CR) within the medial prefrontal cortex (mPFC) is uniquely poised to serve as a strategic nexus to mechanistically control these behaviors. The 5-HT2CR functional capacity is regulated by a number of factors including availability of active membrane receptor pools, the composition of the 5-HT2CR macromolecular protein complex, and editing of the 5-HT2CR pre-mRNA. The one-choice serial reaction time (1-CSRT) task was used to identify impulsive action phenotypes in an outbred rat population before cocaine self-administration and assessment of cue reactivity in the form of lever presses reinforced by the cocaine-associated discrete cue complex during forced abstinence. The 1-CSRT task reliably and reproducibly identified high impulsive (HI) and low impulsive (LI) action phenotypes; HI action predicted high cue reactivity. Lower cortical 5-HT2CR membrane protein levels concomitant with higher levels of 5-HT2CR:postsynaptic density 95 complex distinguished HI rats from LI rats. The frequency of edited 5-HT2CR mRNA variants was elevated with the prediction that the protein population in HI rats favors those isoforms linked to reduced signaling capacity. Genetic loss of the mPFC 5-HT2CR induced aggregate impulsive action/cue reactivity, suggesting that depressed cortical 5-HT2CR tone confers vulnerability to these interlocked behaviors. Thus, impulsive action and cue reactivity appear to neuromechanistically overlap in rodents, with the 5-HT2CR functional status acting as a neural rheostat to regulate, in part, the intersection between these vulnerability behaviors. PMID:23939424

  5. The human 5-HT7 serotonin receptor splice variants: constitutive activity and inverse agonist effects

    PubMed Central

    Krobert, Kurt A; Levy, Finn Olav

    2002-01-01

    Using membranes from stably or transiently transfected HEK293 cells cultured in 5-HT-free medium and expressing the recombinant human 5-HT7 receptor splice variants (h5-HT7(a), h5-HT7(b) and h5-HT7(d)), we compared their abilities to constitutively activate adenylyl cyclase (AC).All h5-HT7 splice variants elevated basal and forskolin-stimulated AC. The basal AC activity was reduced by the 5-HT7 antagonist methiothepin and this effect was blocked by mesulergine (neutral 5-HT7 antagonist) indicating that the inhibitory effect of methiothepin is inverse agonism at the 5-HT7 receptor.Receptor density correlated poorly with constitutive AC activity in stable clonal cell lines and transiently transfected cells. Mean constitutive AC activity as a percentage of forskolin-stimulated AC was significantly higher for the h5-HT7(b) splice variant compared to the h5-HT7(a) and h5-HT7(d) splice variants but only in stable cell lines.All eight 5-HT antagonists tested inhibited constitutive AC activity of all splice variants in a concentration-dependent manner. No differences in inverse agonist potencies (pIC50) were observed between the splice variants. The rank order of potencies was in agreement and highly correlated with antagonist potencies (pKb) determined by antagonism of 5-HT-stimulated AC activity (methiothepin>metergoline>mesulergine⩾clozapine⩾spiperone⩾ritanserin>methysergide>ketanserin).The efficacy of inverse agonism was not receptor level dependent and varied for several 5-HT antagonists between membrane preparations of transiently and stably transfected cells.It is concluded that the h5-HT7 splice variants display similar constitutive activity and inverse agonist properties. PMID:11906971

  6. Interaction of 5-HT1B/D ligands with recombinant h 5-HT1A receptors: intrinsic activity and modulation by G-protein activation state.

    PubMed

    Pauwels, P J; Palmier, C; Dupuis, D S; Colpaert, F C

    1998-05-01

    Many 5-HT1B/D receptor ligands have affinity for 5-HT1A receptors. In the present study, the intrinsic activity of a series of 5-HT1B/D ligands was investigated at human 5-HT1A (h 5-HT1A) receptors by measuring G-protein activation in recombinant C6-glial and HeLa membranes, using agonist-stimulated [35S]GTPgammaS binding. In these two membrane preparations, the density of h 5-HT1A receptors (i.e., 246 to 320 fmol mg(-1) protein) and of their G-proteins, and the receptor: G-protein density ratio (0.08 to 0.18) appeared to be similar. It was found that: (i) the maximal [35S]GTPgammaS binding responses induced by the 5-HT1B/D receptor ligands in the HeLa preparation at 30 microM GDP were comparable to that of the native agonist 5-HT; (ii) as compared to 5-HT (1.00), similar potencies but lower maximal responses were observed in the C6-glial preparation at 0.3 microM GDP for zolmitriptan (0.89), dihydroergotamine (0.81), rizatriptan (0.71), CP122638 (0.69), naratriptan (0.60) and sumatriptan (0.53); and that (iii) maximal [35S]GTPgammaS binding responses induced by 5-HT1B/D ligands in the C6-glial preparation were either unaffected or significantly enhanced by increasing the GDP concentration from 0.3 to 30 microM and higher concentrations. These features differ from those observed with 5-HT1A receptor agonists; the latter display the same rank order of potency and efficacy in both membrane preparations, and increasing the amount of GDP with C6-glial membranes results in an attenuation of both the agonist's maximal effect and the apparent potency of partial agonists. The differential regulation of 5-HT1A and 5-HT1B/D agonist responses by GDP suggests that different G-protein subtypes are involved upon 5-HT1A receptor activation by 5-HT1A and 5-HT1B/D agonists. PMID:9650800

  7. Evaluation of gene expression changes of serotonin receptors, 5-HT3AR and 5-HT2AR as main stress factors in breast cancer patients.

    PubMed

    Hejazi, Seyed Hesam; Ahangari, Ghasem; Pornour, Majid; Deezagi, Abdolkhaleagh; Aminzadeh, Saeed; Ahmadkhaniha, Hamid Reza; Akbari, Mohamad Esmail

    2014-01-01

    Breast cancer is a serious and potentially lethal multi-factor disease among 40-50 aged women in both developed and developing countries. Also, various studies have pointed to roles of neurotransmitters like serotonin in development of cancers, through action on various types of receptors. This study was conducted to evaluate serotonin receptor (5HT2AR and 5HT3AR) genes expression in peripheral blood mononuclear cells (PBMCs) of breast cancer patients in comparison with the healthy people and in the MCF7 cell line. Peripheral blood samples were obtained from 30 patients and 30 healthy individuals. Total RNA was extracted from PBMCs and MCF-7 cells. and 5HT2AR and 5HT3AR were detected by RT-PCR techniques. Finally, serotonin receptor gene expression variation in breast cancer patients and MCF-7 cells were determined by real time-PCR. This latter indicated significant promotion in expression of 5HT3AR and 5HT2AR in PBMCs in breast cancer patients but expression of 5HT2AR in the MCF-7 cell line was significantly decreased. In conclusion, after performing complimentary tests, determine of gene expression changes in serotonin receptors (5HT2AR and 5HT3AR) may be useful as a new approach in treatment of breast cancer based on use of antagonists. PMID:24969868

  8. Size-related differences in the branching pattern of the motor nerve terminals in triangularis sterni muscle of the mouse.

    PubMed

    Tomasi, J; Fenol, R; Santafe, M; Mayayo, E

    1989-01-01

    A light microscopy morphometric study was performed in singly innervated synaptic areas of the triangularis sterni muscle of the normal adult Swiss mouse. Investigating mechanisms of the motor nerve growth control, we tested the hypothesis that significant differences in the nerve terminal branching pattern can be detected between different populations of nerve endings classified according to their arborization complexity or size. The main observations of this morphometric study are first, that the mean segment length of the terminal arborization between branch points behaves as an independent variable from the remaining parameters; the mean value of this parameter did not change in nerve endings of differing size and complexity. Secondly, the increase in size of the nerve endings is accompanied by a significant reduction in the mean length of the distal free-end segments. Results are discussed in the context of the possible regulatory mechanisms governing nerve terminal growth and remodelling. PMID:2752213

  9. The antidepressant-like activity of 6-methoxy-2-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one involves serotonergic 5-HT(1A) and 5-HT(2A/C) receptors activation.

    PubMed

    Pytka, Karolina; Walczak, Maria; Kij, Agnieszka; Rapacz, Anna; Siwek, Agata; Kazek, Grzegorz; Olczyk, Adrian; Gałuszka, Adam; Waszkielewicz, Anna; Marona, Henryk; Sapa, Jacek; Filipek, Barbara

    2015-10-01

    Xanthone derivatives have been shown to posses many biological properties. Some of them act within the central nervous system and show neuroprotective or antidepressant-like properties. Taking this into account we investigated antidepressant-like activity in mice and the possible mechanism of action of 6-methoxy-2-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one (HBK-11) - a new xanthone derivative. We demonstrated that HBK-11 produced antidepressant-like effects in the forced swim test and tail suspension test, comparable to that of venlafaxine. The combined treatment with sub-effective doses of HBK-11 and fluoxetine (but not reboxetine or bupropion) significantly reduced the immobility in the forced swim test. Moreover, the antidepressant-like activity of HBK-11 in the aforementioned test was blocked by p-chlorophenylalanine, and significantly reduced by serotonergic 5HT1A receptor antagonist - WAY-1006335 and 5HT2A/C receptor antagonist - ritanserin. As none of the above treatments influenced the spontaneous locomotor activity, it can be concluded that HBK-11 mediates its activity through a serotonergic system, and its antidepressant-like effect involves 5HT1A and 5HT2A/C receptor activation. Furthermore, at antidepressant-like doses HBK-11 did not cause the mice to display locomotor deficits in rotarod or chimney tests. Considering the pharmacokinetic profile, HBK-11 demonstrated rapid absorption after i.p. administration, high clearance value, short terminal half-life, very high volume of distribution and incomplete bioavailability. The compound studied had good penetration into the brain tissue of mice. Since studied xanthone derivative seems to present interesting, untypical mechanism of antidepressant-like action i.e. 5HT2A/C receptor activation, it may have a potential in the treatment of depressive disorders, and surely requires further studies. PMID:26210317

  10. Localization and Function of a 5-HT Transporter in Crypt Epithelia of the Gastrointestinal Tract

    PubMed Central

    Wade, P. R.; Chen, J.; Jaffe, B.; Kassem, I. S.; Blakely, R. D.; Gershon, M. D.

    2012-01-01

    The peristaltic reflex can be evoked in the absence of input from the CNS because the responsible neural pathways are intrinsic to the intestine. Mucosal enterochromaffin cells have been postulated to be pressure transducers, which activate the intrinsic sensory neurons that initiate the reflex by secreting 5-HT. All of the criteria necessary to establish 5-HT as this transmitter have been fulfilled previously, except that no mucosal mechanism for 5-HT inactivation was known. In the current investigation, desensitization of 5-HT receptors was demonstrated to inhibit the peristaltic reflex in the guinea pig large intestine in vitro. At low concentration (1.0 nM), the 5-HT uptake inhibitor fluoxetine potentiated the reflex, but higher concentrations blocked it, suggesting that the peristaltic reflex depends on the 5-HT transporter-mediated inactivation of 5-HT. Specific (Na+-dependent, fluoxetine-sensitive) uptake of 3H- 5-HT by intestinal crypt epithelial cells was found by radioautography. mRNA encoding the neuronal 5-HT transporter was demonstrated in the intestinal mucosa by Northern analysis and located in crypt epithelial cells as well as in myenteric neurons by in situ hybridization. cDNA encoding the 5-HT transporter was cloned from the mucosa and completely sequenced. 5-HT transporter immunoreactivity was detected in crypt epithelial cells and enteric neurons. Mucosal epithelial cells thus express a plasmalemmal 5-HT transporter identical to that of serotonergic neurons. This molecule seems to play a critical role in the peristaltic reflex. PMID:8601815

  11. Immunohistological localization of 5-HT in the CNS and feeding system of the Stable Fly

    Technology Transfer Automated Retrieval System (TEKTRAN)

    5-HT immunoreactive neurons were detected in the CNS of the stable fly. The finding of strong innervations of the cibarial pump muscles and the foregut by 5-HT IR neurons in the feeding-related systems suggests that 5-HT may play a crucial role in the control of the feeding behavior in both the larv...

  12. The role of serotonin 5-HT2A receptors in memory and cognition

    PubMed Central

    Zhang, Gongliang; Stackman, Robert W.

    2015-01-01

    Serotonin 5-HT2A receptors (5-HT2ARs) are widely distributed in the central nervous system, especially in brain region essential for learning and cognition. In addition to endogenous 5-HT, several hallucinogens, antipsychotics, and antidepressants function by targeting 5-HT2ARs. Preclinical studies show that 5-HT2AR antagonists have antipsychotic and antidepressant properties, whereas agonist ligands possess cognition-enhancing and hallucinogenic properties. Abnormal 5-HT2AR activity is associated with a number of psychiatric disorders and conditions, including depression, schizophrenia, and drug addiction. In addition to its traditional activity as a G protein-coupled receptor (GPCR), recent studies have defined novel operations of 5-HT2ARs. Here we review progress in the (1) receptor anatomy and biology: distribution, signaling, polymerization and allosteric modulation; and (2) receptor functions: learning and memory, hallucination and spatial cognition, and mental disorders. Based on the recent progress in basic research on the 5-HT2AR, it appears that post-training 5-HT2AR activation enhances non-spatial memory consolidation, while pre-training 5-HT2AR activation facilitates fear extinction. Further, the potential influence that 5-HT2AR-elicited visual hallucinations may have on visual cue (i.e., landmark) guided spatial cognition is discussed. We conclude that the development of selective 5-HT2AR modulators to target distinct signaling pathways and neural circuits represents a new possibility for treating emotional, neuropsychiatric, and neurodegenerative disorders. PMID:26500553

  13. Endurance training effects on 5-HT(1B) receptors mRNA expression in cerebellum, striatum, frontal cortex and hippocampus of rats.

    PubMed

    Chennaoui, M; Drogou, C; Gomez-Merino, D; Grimaldi, B; Fillion, G; Guezennec, C Y

    2001-07-01

    The 5-HT(1B) receptors are the predominant auto- and heteroreceptors located on serotonergic and non-serotonergic terminals where they regulate the neuronal release of neurotransmitters. The present study investigated the effects of a 7 week period of physical training on the expression of cerebral 5-HT(1B) receptors by measuring corresponding mRNA levels in rat. Using RNase protection assay technique, we have observed no change in 5-HT(1B) receptor mRNA levels in the striatum and in the hippocampus after moderate as well as after intensive training. In contrast, a significant decrease in 5-HT(1B) receptor mRNA levels was observed in cerebellum of intensively trained rats. Moreover, in frontal cortex, a significant decrease in 5-HT(1B) receptors mRNA level occurred in both groups of trained rats. These data suggest the existence of regional differences in the effect of physical exercise on the expression of 5-HT(1B) receptors. PMID:11516568

  14. Density and Function of Central Serotonin (5-HT) Transporters, 5-HT1A and 5-HT2A Receptors, and Effects of their Targeting on BTBR T+tf/J Mouse Social Behavior

    PubMed Central

    Gould, Georgianna G.; Hensler, Julie G.; Burke, Teresa F.; Benno, Robert H.; Onaivi, Emmanuel S.; Daws, Lynette C.

    2010-01-01

    BTBR mice are potentially useful tools for autism research because their behavior parallels core social interaction impairments and restricted-repetitive behaviors. Altered regulation of central serotonin (5-HT) neurotransmission may underlie such behavioral deficits. To test this, we compared 5-HT transporter (SERT), 5-HT1A and 5-HT2A receptor densities among BTBR and C57 strains. Autoradiographic [3H] cyanoimipramine (1nM) binding to SERT was 20–30% lower throughout the adult BTBR brain as compared to C57BL/10J mice. In hippocampal membrane homogenates [3H] citalopram maximal binding (Bmax) to SERT was 95 ± 13 fmol/mg protein in BTBR and 171 ± 20 fmol/mg protein in C57BL/6J mice, and the BTBR dissociation constant (KD) was 2 ± 0.3 nM vs. 1.1 ± 0.2 in C57BL/6J mice. Hippocampal 5-HT1A and 5-HT2A receptor binding was similar among strains. However, 8-OH-DPAT-stimulated [35S] GTPγS binding in the BTBR hippocampal CA1 region was 28% higher, indicating elevated 5-HT1A capacity to activate G-proteins. In BTBR mice, the SERT blocker, fluoxetine (10 mg/kg) and the 5-HT1A receptor partial-agonist, buspirone (2 mg/kg) enhanced social interactions. The D2/5-HT2 receptor antagonist, risperidone (0.1 mg/kg) reduced marble burying but failed to improve sociability. Overall, altered SERT and/or 5-HT1A functionality in hippocampus could contribute to the relatively low sociability of BTBR mice. PMID:21070242

  15. The influence of 5-HT2 and 5-HT4 receptor antagonists to modify drug induced disinhibitory effects in the mouse light/dark test

    PubMed Central

    Costall, Brenda; Naylor, Robert J

    1997-01-01

    The ability of 5-HT2 and 5-HT4 receptor antagonists to modify the disinhibitory profile of diazepam and other agents was investigated in male BKW mice in the light/dark test box. The 5-HT2A/2B/2C receptor antagonists ritanserin, MDL11939 and RP62203 and also methysergide, which failed to modify mouse behaviour when administered alone, caused dose-related enhancements (4 to 8 fold) in the potency of diazepam to disinhibit behavioural responding to the aversive situation of the test box. Ritanserin was shown to enhance the disinhibitory potency of other benzodiazepines, chlordiazepoxide (4 fold), temazepam (10 fold) and lorazepam (10 fold), the 5-HT1A receptor ligands, 8-OH-DPAT (25 fold), buspirone (100 fold) and lesopitron (500 fold), the 5-HT3 receptor antagonists, ondansetron (100 fold) R(+)-zacopride (100 fold) and S(−)-zacopride (greater than a 1000 fold), the substituted benzamides, sulpiride (10 fold) and tiapride (5 to 10 fold) and the cholecystokinin (CCK)A receptor antagonist, devazepide (100 fold). It also reduced the onset of action of disinhibition following treatment with the 5-HT synthesis inhibitor parachlorophenylalanine. Ritanserin failed to enhance the disinhibitory effects of the CCKB receptor antagonist CI-988, the angiotensin AT1 receptor antagonist losarten or the angiotensin converting enzyme inhibitor ceranapril. The 5-HT4 receptor antagonists SDZ205-557, GR113808 and SB204070 caused dose-related reductions in the disinhibitory effect of diazepam, returning values to those shown in vehicle treated controls. The antagonists failed to modify mouse behaviour when administered alone. GR113808 was also shown to cause a dose-related antagonism of the disinhibitory effects of chlordiazepoxide, lorazepam, 8-OH-DPAT, buspirone, lesopitron, ondansetron, R(+)-zacopride, sulpiride, tiapride, devazepide, CI-988, losarten, ceranapril and parachlorophenylalanine. It was concluded that in BKW mice (a) the failure of 5-HT2 and 5-HT4 receptor antagonists

  16. Evaluation of the ocular hypotensive response of serotonin 5-HT1A and 5-HT2 receptor ligands in conscious ocular hypertensive cynomolgus monkeys.

    PubMed

    May, Jesse A; McLaughlin, Marsha A; Sharif, Najam A; Hellberg, Mark R; Dean, Thomas R

    2003-07-01

    Published investigations of serotonin-1A (5-hydroxytryptamine1A; 5-HT1A) receptor agonists and serotonin-2A (5-hydroxytryptamine2A; 5-HT2A) receptor antagonists in nonprimate species provide conflicting results with regard to their intraocular pressure-lowering efficacy. Thus, their therapeutic utility in the treatment of human glaucoma has been confusing. We evaluated the effect of selected 5-HT1A agonists and 5-HT2A receptor antagonists on intraocular pressure in a nonhuman primate model, the conscious cynomolgus monkey with laser-induced ocular hypertension. Neither selective 5-HT1A agonists [e.g., R-8-hydroxy-2-(di-n-propylamino)tetralin and flesinoxan] nor selective 5-HT2 receptor antagonists [e.g., R-(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol (M-100907) and 6-chloro-2,3-dihydro-5-methyl-N-[6-[(2-methyl-3-pyridinyl)oxy]-3-pyridinyl]-1H-indole-1-carboxamide (SB-242084)] lowered intraocular pressure in the primate model following topical ocular administration. However, compounds that function as agonists at both the 5-HT1A and 5-HT2 receptors were found to effectively lower intraocular pressure in the model: 5-hydroxy-alpha-methyltryptamine, 5-methoxy-alpha-methyltryptamine, 5-hydroxy-N,N-dimethyltryptamine (bufotenine), and 5-methoxy-N,N-dimethyltryptamine. Furthermore, the selective 5-HT2 receptor agonist R-(-)-1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane lowered intraocular pressure in the primate model, demonstrating a pharmacological response associated with activation of the 5-HT2 receptor. These observations suggest that compounds that function as efficient agonists at 5-HT2 receptors should be considered as potential agents for the control of intraocular pressure in the treatment of ocular hypertension and glaucoma in humans. PMID:12676887

  17. Effects of chronic citalopram treatment on 5-HT1A and 5-HT2A receptors in group- and isolation-housed mice.

    PubMed

    Günther, Lydia; Liebscher, Sabine; Jähkel, Monika; Oehler, Jochen

    2008-09-28

    Selective serotonin reuptake inhibitors (SSRI) are characterized by high clinical effectiveness and good tolerability. A 2-3 week delay in the onset of effects is caused by adaptive mechanisms, probably at the serotonergic (5-HT) receptor level. To analyze this in detail, we measured 5-HT(1A) and 5-HT(2A) receptor bindings in vitro after 3 weeks of citalopram treatment (20 mg/kg i.p. daily) in group-housed as well as isolation-housed mice, reflecting neurobiological aspects seen in psychiatric patients. Isolation housing increased somatodendritic (+52%) and postsynaptic (+30-95%) 5-HT(1A) as well as postsynaptic 5-HT(2A) receptor binding (+25-34%), which confirms previous findings. Chronic citalopram treatment did not induce alterations in raphe 5-HT(1A) autoreceptor binding, independent of housing conditions. Housing-dependent citalopram effects on postsynaptic 5-HT(1A) receptor binding were found with increases in group- (+11-42%) but decreases in isolation-housed (-11 to 35%) mice. Forebrain 5-HT(2A) receptor binding decreased between 11 and 38% after chronic citalopram administration, independent of housing conditions. Citalopram's long-term action comprises alterations at the postsynaptic 5-HT(1A) and 5-HT(2A) receptor binding levels. Housing conditions interact with citalopram effects, especially on 5-HT(1A) receptor binding, and should be more strongly considered in pharmacological studies. In general, SSRI-induced alterations were more pronounced and affected more brain regions in isolates, supporting the concept of a higher responsiveness in "stressed" animals. Isolation-induced receptor binding changes were partly normalized by chronic citalopram treatment, suggesting the isolation housing model for further analyses of SSRI effects, especially at the behavioral level. PMID:18657534

  18. Role of 5-HT5A and 5-HT1B/1D receptors in the antinociception produced by ergotamine and valerenic acid in the rat formalin test.

    PubMed

    Vidal-Cantú, Guadalupe C; Jiménez-Hernández, Mildred; Rocha-González, Héctor I; Villalón, Carlos M; Granados-Soto, Vinicio; Muñoz-Islas, Enriqueta

    2016-06-15

    Sumatriptan, dihydroergotamine and methysergide inhibit 1% formalin-induced nociception by activation of peripheral 5-HT1B/1D receptors. This study set out to investigate the pharmacological profile of the antinociception produced by intrathecal and intraplantar administration of ergotamine (a 5-HT1B/1D and 5-HT5A/5B receptor agonist) and valerenic acid (a partial agonist at 5-HT5A receptors). Intraplantar injection of 1% formalin in the right hind paw resulted in spontaneous flinching behavior of the injected hindpaw of female Wistar rats. Intrathecal ergotamine (15nmol) or valerenic acid (1 nmol) blocked in a dose dependent manner formalin-induced nociception. The antinociception by intrathecal ergotamine (15nmol) or valerenic acid (1nmol) was partly or completely blocked by intrathecal administration of the antagonists: (i) methiothepin (non-selective 5-HT5A/5B; 0.01-0.1nmol); (ii) SB-699551 (selective 5-HT5A; up to 10nmol); (iii) anti-5-HT5A antibody; (iv) SB-224289 (selective 5-HT1B; 0.1-1nmol); or (v) BRL-15572 (selective 5-HT1D; 0.1-1nmol). Likewise, antinociception by intraplantar ergotamine (15nmol) and valerenic acid (10nmol) was: (i) partially blocked by methiothepin (1nmol), SB-699551 (10nmol) or SB-224289 (1nmol); and (ii) abolished by BRL-15572 (1nmol). The above doses of antagonists (which did not affect per se the formalin-induced nociception) were high enough to completely block their respective receptors. Our results suggest that ergotamine and valerenic acid produce antinociception via 5-HT5A and 5-HT1B/1D receptors located at both spinal and peripheral sites. This provides new evidence for understanding the modulation of nociceptive pathways in inflammatory pain. PMID:27068146

  19. Increased expression of 5-HT(2A) and 5-HT(2B) receptors in detrusor muscle after partial bladder outlet obstruction in rats.

    PubMed

    Michishita, Mai; Yano, Kazuo; Kasahara, Ken-ichi; Tomita, Ken-ichi; Matsuzaki, Osamu

    2015-01-01

    Serotonin (5-hydroxytryptamine; 5-HT)-induced bladder contraction is enhanced after partial bladder outlet obstruction (pBOO) in rats. We investigated time-dependent changes in bladder contraction and expression of 5-HT(2A) and 5-HT(2B) receptor mRNA in bladder tissue to elucidate the mechanism of this enhancement. On day 3 and 7 after pBOO, contractile responses of isolated rat bladder strips to 5-HT were increased compared with that in sham-operated rats; on day 14, the response had decreased to the same level as that in sham rat bladders. In contrast, carbacholinduced contraction was not enhanced by pBOO at any time point. In sham rats, 5-HT(2A) receptor mRNA was expressed in the urothelium, and 5-HT(2B) receptor mRNA was expressed in the detrusor muscle layer. In pBOO rats, both receptor mRNAs were increased in the detrusor muscle and subserosal layers, but not in the urothelium. The increase of 5-HT(2A) receptor mRNA was maintained from day 3 to day 14 after pBOO, and 5-HT(2B) receptor mRNA was increased on day 7 after pBOO. These results suggested that pBOO induced up-regulation of the 5-HT(2A) and 5-HT(2B) receptors in the detrusor muscle and subserosal layers of the bladder, and such up-regulation may be related to the enhanced bladder contractile response to 5-HT. PMID:26106048

  20. 5-HT1A and 5-HT1B receptors control the firing of serotoninergic neurons in the dorsal raphe nucleus of the mouse: studies in 5-HT1B knock-out mice.

    PubMed

    Evrard, A; Laporte, A M; Chastanet, M; Hen, R; Hamon, M; Adrien, J

    1999-11-01

    The characteristics of the spontaneous firing of serotoninergic neurons in the dorsal raphe nucleus and its control by serotonin (5-hydroxytryptamine, 5-HT) receptors were investigated in wild-type and 5-HT1B knock-out (5-HT1B-/-) mice of the 129/Sv strain, anaesthetized with chloral hydrate. In both groups of mice, 5-HT neurons exhibited a regular activity with an identical firing rate of 0.5-4.5 spikes/s. Intravenous administration of the 5-HT reuptake inhibitor citalopram or the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) induced a dose-dependent inhibition of 5-HT neuronal firing which could be reversed by the selective 5-HT1A antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohe xane carboxamide (WAY 100635). Both strains were equally sensitive to 8-OH-DPAT (ED50 approximately 6.3 microgram/kg i.v.), but the mutants were less sensitive than wild-type animals to citalopram (ED50 = 0.49 +/- 0.02 and 0.28 +/- 0.01 mg/kg i.v., respectively, P < 0.05). This difference could be reduced by pre-treatment of wild-type mice with the 5-HT1B/1D antagonist 2'-methyl-4'-(5-methyl-[1,2,4]oxadiazol-3-yl)-biphenyl-4-carbox yli c acid [4-methoxy-3-(4-methyl-piperazine-1-yl)-phenyl]amide (GR 127935), and might be accounted for by the lack of 5-HT1B receptors and a higher density of 5-HT reuptake sites (specifically labelled by [3H]citalopram) in 5-HT1B-/- mice. In wild-type but not 5-HT1B-/- mice, the 5-HT1B agonists 3-(1,2,5, 6-tetrahydro-4-pyridyl)-5-propoxypyrrolo[3,2-b]pyridine (CP 94253, 3 mg/kg i.v.) and 5-methoxy-3-(1,2,3, 6-tetrahydropyridin-4-yl)-1H-indole (RU 24969, 0.6 mg/kg i.v.) increased the firing rate of 5-HT neurons (+22.4 +/- 2.8% and +13.7 +/- 6.0%, respectively, P < 0.05), and this effect could be prevented by the 5-HT1B antagonist GR 127935 (1 mg/kg i.v.). Altogether, these data indicate that in the mouse, the firing of 5-HT neurons in the dorsal raphe nucleus is under both an inhibitory control through 5-HT1A

  1. A selective 5-HT1a receptor agonist improves respiration in a mouse model of Rett syndrome

    PubMed Central

    Levitt, Erica S.; Hunnicutt, Barbara J.; Knopp, Sharon J.; Williams, John T.

    2013-01-01

    Rett syndrome is a neurological disorder caused by loss of function mutations in the gene that encodes the DNA binding protein methyl-CpG-binding protein 2 (Mecp2). A prominent feature of the syndrome is disturbances in respiration characterized by frequent apnea and an irregular interbreath cycle. 8-Hydroxy-2-dipropylaminotetralin has been shown to positively modulate these disturbances (Abdala AP, Dutschmann M, Bissonnette JM, Paton JF, Proc Natl Acad Sci U S A 107: 18208–18213, 2010), but the mode of action is not understood. Here we show that the selective 5-HT1a biased agonist 3-chloro-4-fluorophenyl-(4-fluoro-4-{[(5-methylpyrimidin-2-ylmethyl)-amino]-methyl}-piperidin-1-yl)-methanone (F15599) decreases apnea and corrects irregularity in both heterozygous Mecp2-deficient female and in Mecp2 null male mice. In whole cell voltage-clamp recordings from dorsal raphe neurons, F15599 potently induced an outward current, which was blocked by barium, reversed at the potassium equilibrium potential, and was antagonized by the 5-HT1a antagonist WAY100135. This is consistent with somatodendritic 5-HT1a receptor-mediated activation of G protein-coupled inwardly rectifying potassium channels (GIRK). In contrast, F15599 did not activate 5-HT1b/d receptors that mediate inhibition of glutamate release from terminals in the nucleus accumbens by a presynaptic mechanism. Thus F15599 activated somatodendritic 5-HT1a autoreceptors, but not axonal 5-HT1b/d receptors. In unanesthetized Mecp2-deficient heterozygous female mice, F15599 reduced apnea in a dose-dependent manner with maximal effect of 74.5 ± 6.9% at 0.1 mg/kg and improved breath irrregularity. Similarly, in Mecp2 null male mice, apnea was reduced by 62 ± 6.6% at 0.25 mg/kg, and breathing became regular. The results indicate respiration is improved with a 5-HT1a agonist that activates GIRK channels without affecting neurotransmitter release. PMID:24092697

  2. Characterisation of the 5-HT receptor binding profile of eletriptan and kinetics of [3H]eletriptan binding at human 5-HT1B and 5-HT1D receptors.

    PubMed

    Napier, C; Stewart, M; Melrose, H; Hopkins, B; McHarg, A; Wallis, R

    1999-03-01

    The affinity of eletriptan ((R)-3-(1-methyl-2-pyrrolidinylmethyl)-5-[2-(phenylsulphonyl )ethyl]-1H-indole) for a range of 5-HT receptors was compared to values obtained for other 5-HT1B/1D receptor agonists known to be effective in the treatment of migraine. Eletriptan, like sumatriptan, zolmitriptan, naratriptan and rizatriptan had highest affinity for the human 5-HT1B, 5-HT1D and putative 5-ht1f receptor. Kinetic studies comparing the binding of [3H]eletriptan and [3H]sumatriptan to the human recombinant 5-HT1B and 5-HT1D receptors expressed in HeLa cells revealed that both radioligands bound with high specificity (>90%) and reached equilibrium within 10-15 min. However, [3H]eletriptan had over 6-fold higher affinity than [3H]sumatriptan at the 5-HT1D receptor (K(D)): 0.92 and 6.58 nM, respectively) and over 3-fold higher affinity than [3H]sumatriptan at the 5-HT1B receptor (K(D): 3.14 and 11.07 nM, respectively). Association and dissociation rates for both radioligands could only be accurately determined at the 5-HT1D receptor and then only at 4 degrees C. At this temperature, [3H]eletriptan had a significantly (P<0.05) faster association rate (K(on) 0.249 min(-1) nM(-1)) than [3H]sumatriptan (K(on) 0.024 min(-1) nM(-1)) and a significantly (P<0.05) slower off-rate (K(off) 0.027 min(-1) compared to 0.037 min(-1) for [3H]sumatriptan). These data indicate that eletriptan is a potent ligand at the human 5-HT1B, 5-HT1D, and 5-ht1f receptors and are consistent with its potent vasoconstrictor activity and use as a drug for the acute treatment of migraine headache. PMID:10193663

  3. New halogenated tris-(phenylalkyl)amines as h5-HT2B receptor ligands.

    PubMed

    Kapadia, Nirav; Ahmed, Shahrear; Harding, Wayne W

    2016-07-15

    A series of compounds in which various halogen substituents were incorporated into a phenyl ring of a tris-(phenylalkyl)amine scaffold, was synthesized and evaluated for affinity to h5-HT2 receptors. In general, all compounds were found to have good affinity for the 5-HT2B receptor and were selective over 5-HT2A and 5-HT2C receptors. Compound 9i was the most selective compound in this study and is the highest affinity 5-HT2B receptor ligand bearing a tris-(phenylalkyl)amine scaffold to date. PMID:27261181

  4. Expression of a conserved cell-type-specific protein in nerve terminals coincides with synaptogenesis.

    PubMed Central

    Catsicas, S; Larhammar, D; Blomqvist, A; Sanna, P P; Milner, R J; Wilson, M C

    1991-01-01

    Contact of axons with target territories results in the formation of synapses, specific junctional complexes that may represent a final stage of neuronal maturation. Synaptosomal-associated protein 25 (SNAP-25) is a component of particular nerve terminals recently identified in rodent brain. To evaluate the structure and regulation of molecular components of the synapse, we investigated the expression of SNAP-25 in the developing chicken nervous system. Analysis of SNAP-25 cDNA clones demonstrated that the chicken homologue is identical in amino acid sequence to the mouse protein. In chicken retina and neural tube, the onset of SNAP-25 mRNA and protein expression was found to correspond to the time of synaptogenesis. These results suggest that SNAP-25 plays a role in the physiology of mature nerve terminals and that its expression may be regulated by specific cell-cell interactions occurring during synapse formation. Images PMID:1992470

  5. Increased hypothalamic 5-HT2A receptor gene expression and effects of pharmacologic 5-HT2A receptor inactivation in obese A{sup y} mice

    SciTech Connect

    Nonogaki, Katsunori . E-mail: knonogaki-tky@umin.ac.jp; Nozue, Kana; Oka, Yoshitomo

    2006-12-29

    Serotonin (5-hydroxytryptamine; 5-HT) 2A receptors contribute to the effects of 5-HT on platelet aggregation and vascular smooth muscle cell proliferation, and are reportedly involved in decreases in plasma levels of adiponectin, an adipokine, in diabetic subjects. Here, we report that systemic administration of sarpogrelate, a 5-HT2A receptor antagonist, suppressed appetite and increased hypothalamic pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript, corticotropin releasing hormone, 5-HT2C, and 5-HT1B receptor gene expression. A{sup y} mice, which have ectopic expression of the agouti protein, significantly increased hypothalamic 5-HT2A receptor gene expression in association with obesity compared with wild-type mice matched for age. Systemic administration of sarpogrelate suppressed overfeeding, body weight gain, and hyperglycemia in obese A{sup y} mice, whereas it did not increase plasma adiponectin levels. These results suggest that obesity increases hypothalamic 5-HT2A receptor gene expression, and pharmacologic inactivation of 5-HT2A receptors inhibits overfeeding and obesity in A{sup y} mice, but did not increase plasma adiponectin levels.

  6. Conformational state of human cardiac 5-HT(4(g)) receptors influences the functional effects of polyclonal anti-5-HT(4) receptor antibodies.

    PubMed

    Di Scala, Emmanuella; Rose, Stéphanie; Hérault, Olivier; Argibay, Jorge; Cosnay, Pierre; Bozon, Véronique

    2007-04-01

    The functional effects of the anti-G21V antibody directed against the second extracellular loop of human heart 5-HT(4) receptors can differ when the receptors are expressed in different cell lines. Here, we extend these studies to show variation in the responses of 5-HT(4(g)) receptors to the antibody within the same expression system. In a previous report no effect of the anti-G21V antibodies had been shown upon 5-HT(4(g)) receptors expressed in CHO cells. Here the same antibodies alone or when added before 5-HT had a functional "inverse-agonist like" effect upon 5-HT(4(g)) receptors expressed in a separate line of CHO cells. Although these CHO cells showed a lower efficacy of cAMP production evoked by 5-HT than the previous report they express a similar h5-HT(4(g)) receptor density. Inhibition of either phosphodiesterases or Gi proteins had no effect upon the action of the antibody. Conformational states of the 5-HT(4) receptor and/or equilibrium between different states of receptors may then determine the functional effect of antibodies against this receptor. PMID:17222392

  7. Deletion of the 5-HT3A-receptor subunit blunts the induction of cocaine sensitization

    PubMed Central

    Hodge, C. W.; Bratt, A. M.; Kelley, S. P.

    2008-01-01

    Serotonin (5-HT) receptors are classified into seven groups (5-HT1–7), comprising at least 14 structurally and pharmacologically distinct receptor subtypes. Pharma-cological antagonism of ionotropic 5-HT3 receptors has been shown to modulate both behavioral and neuro-chemical aspects of the induction of sensitization to cocaine. It is not known, however, if specific molecular subunits of the 5-HT3 receptor influence the development of cocaine sensitization. To address this question, we studied the effects of acute and chronic intermittent cocaine administration in mice with a targeted deletion of the gene for the 5-HT3A-receptor subunit (5-HT3A −/−). 5-HT3A (−/−) mice showed blunted induction of cocaine-induced locomotor sensitization as compared with wild-type littermate controls. 5-HT3A (−/−) mice did not differ from wild-type littermate controls on measures of basal motor activity or response to acute cocaine treatment. Enhanced locomotor response to saline injection following cocaine sensitization was observed equally in 5-HT3A (−/−) and wild-type mice suggesting similar conditioned effects associated with chronic cocaine treatment. These data show a role for the 5-HT3A-receptor subunit in the induction of behavioral sensitization to cocaine and suggest that the 5-HT3A molecular subunit modulates neurobehavioral adaptations to cocaine, which may underlie aspects of addiction. PMID:17559417

  8. A Subpopulation of Serotonergic Neurons That Do Not Express the 5-HT1A Autoreceptor

    PubMed Central

    2012-01-01

    5-HT neurons are topographically organized in the hindbrain, and have been implicated in the etiology and treatment of psychiatric diseases such as depression and anxiety. Early studies suggested that the raphe 5-HT neurons were a homogeneous population showing similar electrical properties, and feedback inhibition mediated by 5-HT1A autoreceptors. We utilized histochemistry techniques in ePet1-eGFP and 5-HT1A-iCre/R26R mice to show that a subpopulation of 5-HT neurons do not express the somatodendritic 5-HT1A autoreceptor mRNA. In addition, we performed patch-clamp recordings followed by single-cell PCR in ePet1-eGFP mice. From 134 recorded 5-HT neurons located in the dorsal, lateral, and median raphe, we found lack of 5-HT1A mRNA expression in 22 cells, evenly distributed across raphe subfields. We compared the cellular characteristics of these neuronal types and found no difference in passive membrane properties and general excitability. However, when injected with large depolarizing current, 5-HT1A-negative neurons fired more action potentials, suggesting a lack of autoinhibitory action of local 5-HT release. Our results support the hypothesis that the 5-HT system is composed of subpopulations of serotonergic neurons with different capacity for adaptation. PMID:23336048

  9. Distribution of cells responsive to 5-HT6 receptor antagonist-induced hypophagia

    PubMed Central

    Garfield, Alastair S.; Burke, Luke K.; Shaw, Jill; Evans, Mark L.; Heisler, Lora K.

    2014-01-01

    The central 5-hydroxytryptamine (5-HT; serotonin) system is well established as an important regulator of appetite and continues to remain a focus of obesity research. While much emphasis has focussed on the 5-HT2C receptor (5-HT2CR) in 5-HT's anorectic effect, pharmacological manipulation of the 5-HT6 receptor (5-HT6R) also reduces appetite and body weight and may be amenable to obesity treatment. However, the neurological circuits that underlie 5-HT6R-induced hypophagia remain to be identified. Using c-fos immunoreactivity (FOS-IR) as a marker of neuronal activation, here we mapped the neuroanatomical targets activated by an anorectic dose of the 5-HT6R antagonist SB-399885 throughout the brain. Furthermore, we quantified SB-399855 activated cells within brain appetitive nuclei, the hypothalamus, dorsal raphe nucleus (DRN) and nucleus of the solitary tract (NTS). Our results reveal that 5-HT6R antagonist-induced hypophagia is associated with significantly increased neuronal activation in two nuclei with an established role in the central control of appetite, the paraventricular nucleus of the hypothalamus (PVH) and the NTS. In contrast, no changes in FOS-IR were observed between treatment groups within other hypothalamic nuclei or DRN. The data presented here provide a first insight into the neural circuitry underlying 5-HT6R antagonist-induced appetite suppression and highlight the PVH and NTS in the coordination of 5-HT6R hypophagia. PMID:24566060

  10. Synergistic effect between 5-HT4 receptor agonist and phosphodiesterase 4-inhibitor in releasing acetylcholine in pig gastric circular muscle in vitro.

    PubMed

    Lefebvre, Romain A; Van Colen, Inge; Pauwelyn, Vicky; De Maeyer, Joris H

    2016-06-15

    5-HT4 receptor agonists have a gastroprokinetic effect by facilitating acetylcholine release from cholinergic nerves innervating gastrointestinal smooth muscle. The role of phosphodiesterase (PDE) 4 in the signal transduction pathway of the 5-HT4 receptors located on the cholinergic neurons towards the circular muscle layer in pig stomach was investigated by analysis of acetylcholine release. Circular muscle strips were prepared from pig proximal stomach and tritium outflow, induced by electrical field stimulation, was studied as a marker for acetylcholine release after incubation with [(3)H]-choline. The PDE4-inhibitor roflumilast concentration-dependently (0.1-1µM) enhanced the facilitating effect of a submaximally effective concentration of the 5-HT4 receptor agonist prucalopride (0.01µM) on electrically induced acetylcholine release. Roflumilast (0.3µM) enhanced acetylcholine release per se but in the combined presence of roflumilast and prucalopride, acetylcholine release was enhanced more than the sum of the effect of the 2 compounds alone. The 5-HT4 receptor agonist velusetrag concentration-dependently (0.01-0.1µM) enhanced acetylcholine release; the effect of the minimally effective concentration (0.01µM) was significantly enhanced by 1µM of the PDE4-inhibitor rolipram, again to a level higher than the sum of the effect of the 2 compounds alone. The synergistic effect between 5-HT4 receptor agonists and PDE4-inhibitors demonstrates that the intracellular pathway of the 5-HT4 receptors located on cholinergic neurons towards pig gastric circular muscle is controlled by PDE4. Combining a 5-HT4 receptor agonist with a PDE4-inhibitor might thus enhance its gastroprokinetic effect. PMID:27060014

  11. Human 5-HT1F receptor-stimulated [35S]GTPgammaS binding: correlation with inhibition of guinea pig dural plasma protein extravasation.

    PubMed

    Wainscott, D B; Johnson, K W; Phebus, L A; Schaus, J M; Nelson, D L

    1998-07-01

    To determine the potency and efficacy of 5-HT1F receptor ligands, a [35S]GTPgammaS binding assay was developed and optimized for the human 5-HT1F receptor. Compounds which are known to be effective in the abortive treatment of migraine were tested for efficacy and potency in this assay. Naratriptan, sumatriptan, zolmitriptan, and rizatriptan all had agonist activity. The 5-HT1F receptor ligand LY334370 (4-fluoro-N-[3-(1-methyl-4-piperidinyl)-1H-indol-5-yl]-benzamide) was the most potent compound tested with an EC50 of 2.13 +/- 0.15 nM. LY302148 (5-fluoro-3-[1-[2-(1-methyl-1H-pyrazol-4-yl)ethyl]-4-piperidinyl]-1H-ind ole), methysergide, LY306258 (3-dimethylamino-2,3,4,9-tetrahydro-1H-carbazol-6-ol), dihydroergotamine (DHE), L-694,247 and CP-122,288 were also investigated for potency and efficacy. There was a statistically significant correlation between the pEC50 for the stimulation of [35S]GTPgammaS binding and the pID50 for the inhibition of trigeminal nerve-stimulated dural plasma protein extravasation in the guinea pig. In the course of these studies, it was found that the purportedly selective 5-HT1D receptor antagonist GR127935 inhibited 5-HT1F receptor-stimulated [35S]GTPgammaS binding with a Ki of 39.6 +/- 9.5 nM. These studies demonstrate that 5-HT1F receptor-mediated stimulation of [35S]GTPgammaS binding in a clonal cell system is a reproducible, high throughput assay that is predictive of an in vivo model of 5-HT1F receptor activation. PMID:9718276

  12. Cloning, expression and pharmacology of a truncated splice variant of the human 5-HT7 receptor (h5-HT7(b))

    PubMed Central

    Jasper, J R; Kosaka, A; To, Z P; Chang, D J; Eglen, R M

    1997-01-01

    The rat 5-hydroxytryptamine (5-HT)7 receptor displays two splice variations, a long form, and a truncated splice isoform, arising from the introduction of a stop codon near the carboxy-terminus. The human 5-HT7 receptor gene contains at least two introns and encodes a 445 amino acid 5-HT receptor. A truncated splice variation in the human 5-HT7 receptor was isolated from a human placental cDNA library. In accordance with current NC-IUPHAR nomenclature guidelines, it is suggested that this receptor be denoted as the h5-HT7(b) receptor and the long form of the receptor as h5-HT7(a). The h5-HT7(b) receptor was stably expressed in HEK 293 cells and ligand affinities were determined by displacement of [3H]-5-carboxyamidotryptamine (5-CT; Kd=0.28±0.06 nM, Bmax=7.3±1.7 pmol mg−1 protein). The rank order of affinities (pKi) for a series of ligands was: 5-carboxamidotryptamine (5-CT, 9.65)>5-hydroxytryptamine (5-HT, 9.41)>methiothepin (8.87)>mesulergine (7.87)>8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT, 6.85)>ketanserin (6.44). The h5-HT7(b) receptor coupled positively to adenylyl cyclase in HEK 293 cells. This response was elicited by a number of agonists with the following order of potency (pEC50): 5-CT (8.7±0.11)>5-MeOT (5-methoxytryptamine; 8.1±0.20)>5-HT (7.5±0.13)>tryptamine (5.6±0.36)>8-OH-DPAT (5.3±0.28)>5-methoxytryptamine (5.0±0.06). This rank order was comparable to that observed in the radioligand binding studies. In a similar fashion to that described for the 5-HT7(a) receptor, PCR studies suggested that the 5-HT7(b) receptor mRNA is found in great abundance throughout the brain, in the small intestine and aorta. It is concluded that the h5-HT7 receptor, like the rat receptor, exists as splice variants exhibiting similar pharmacology, signal transduction and distribution. It is thus likely that there exists a complex physiological role for alternate splicing products of the 5-HT7 receptor gene. PMID:9298538

  13. Down-regulation of 5-HT1B and 5-HT1D receptors inhibits proliferation, clonogenicity and invasion of human pancreatic cancer cells.

    PubMed

    Gurbuz, Nilgun; Ashour, Ahmed A; Alpay, S Neslihan; Ozpolat, Bulent

    2014-01-01

    Pancreatic ductal adenocarcinoma is characterized by extensive local tumor invasion, metastasis and early systemic dissemination. The vast majority of pancreatic cancer (PaCa) patients already have metastatic complications at the time of diagnosis, and the death rate of this lethal type of cancer has increased over the past decades. Thus, efforts at identifying novel molecularly targeted therapies are priorities. Recent studies have suggested that serotonin (5-HT) contributes to the tumor growth in a variety of cancers including prostate, colon, bladder and liver cancer. However, there is lack of evidence about the impact of 5-HT receptors on promoting pancreatic cancer. Having considered the role of 5-HT-1 receptors, especially 5-HT1B and 5-HT1D subtypes in different types of malignancies, the aim of this study was to investigate the role of 5-HT1B and 5-HT1D receptors in PaCa growth and progression and analyze their potential as cytotoxic targets. We found that knockdown of 5-HT1B and 5-HT1D receptors expression, using specific small interfering RNA (siRNA), induced significant inhibition of proliferation and clonogenicity of PaCa cells. Also, it significantly suppressed PaCa cells invasion and reduced the activity of uPAR/MMP-2 signaling and Integrin/Src/Fak-mediated signaling, as integral tumor cell pathways associated with invasion, migration, adhesion, and proliferation. Moreover, targeting 5-HT1B and 5-HT1D receptors down-regulates zinc finger ZEB1 and Snail proteins, the hallmarks transcription factors regulating epithelial-mesenchymal transition (EMT), concomitantly with up-regulating of claudin-1 and E-Cadherin. In conclusion, our data suggests that 5-HT1B- and 5-HT1D- mediated signaling play an important role in the regulation of the proliferative and invasive phenotype of PaCa. It also highlights the therapeutic potential of targeting of 5-HT1B/1D receptors in the treatment of PaCa, and opens a new avenue for biomarkers identification, and valuable new

  14. Down-regulation of 5-HT1B and 5-HT1D receptors inhibits proliferation, clonogenicity and invasion of human pancreatic cancer cells.

    PubMed

    Gurbuz, Nilgun; Ashour, Ahmed A; Alpay, S Neslihan; Ozpolat, Bulent

    2014-01-01

    Pancreatic ductal adenocarcinoma is characterized by extensive local tumor invasion, metastasis and early systemic dissemination. The vast majority of pancreatic cancer (PaCa) patients already have metastatic complications at the time of diagnosis, and the death rate of this lethal type of cancer has increased over the past decades. Thus, efforts at identifying novel molecularly targeted therapies are priorities. Recent studies have suggested that serotonin (5-HT) contributes to the tumor growth in a variety of cancers including prostate, colon, bladder and liver cancer. However, there is lack of evidence about the impact of 5-HT receptors on promoting pancreatic cancer. Having considered the role of 5-HT-1 receptors, especially 5-HT1B and 5-HT1D subtypes in different types of malignancies, the aim of this study was to investigate the role of 5-HT1B and 5-HT1D receptors in PaCa growth and progression and analyze their potential as cytotoxic targets. We found that knockdown of 5-HT1B and 5-HT1D receptors expression, using specific small interfering RNA (siRNA), induced significant inhibition of proliferation and clonogenicity of PaCa cells. Also, it significantly suppressed PaCa cells invasion and reduced the activity of uPAR/MMP-2 signaling and Integrin/Src/Fak-mediated signaling, as integral tumor cell pathways associated with invasion, migration, adhesion, and proliferation. Moreover, targeting 5-HT1B and 5-HT1D receptors down-regulates zinc finger ZEB1 and Snail proteins, the hallmarks transcription factors regulating epithelial-mesenchymal transition (EMT), concomitantly with up-regulating of claudin-1 and E-Cadherin. In conclusion, our data suggests that 5-HT1B- and 5-HT1D-mediated signaling play an important role in the regulation of the proliferative and invasive phenotype of PaCa. It also highlights the therapeutic potential of targeting of 5-HT1B/1D receptors in the treatment of PaCa, and opens a new avenue for biomarkers identification, and valuable new

  15. Pharmacological evidence for CGRP uptake into perivascular capsaicin sensitive nerve terminals

    PubMed Central

    Sams-Nielsen, Anette; Orskov, Cathrine; Jansen-Olesen, Inger

    2001-01-01

    Specific mechanisms, providing reuptake of cathecholamine and amino acid neurotransmitters (e.g. serotonin and glutamate) into cells of the central nervous system are well known, whereas neuronal uptake of neuropeptide transmitters have not previously been reported. In the present study we present evidence for uptake of the 37 amino acid neuropeptide, calcitonin gene-related peptide (CGRP) into perivascular terminals of capsaicin sensitive nerve fibres, innervating the guinea-pig basilar artery. Release of CGRP from perivascular nerve terminals was obtained by capsaicin-induced vanilloid receptor-stimulation and detected as CGRP receptor-mediated dilation of isolated segments of the guinea-pig basilar artery. Following three repeated capsaicin challenges, CGRP-depleted segments were incubated with CGRP. This caused significant reappearance of capsaicin-induced vasodilatory responses. These responses were dependent on duration and concentration of the preceding CGRP incubation and were inhibited by the CGRP receptor antagonist, CGRP8–37. The CGRP-re-depletion was significantly reduced when CGRP8–37 was present during the preceding CGRP incubation. Thus, presynaptic CGRP receptors are likely to be involved in neuronal CGRP uptake. Incubating the artery segments with 125I-CGRP allowed subsequent detection of capsaicin-induced 125I-release. Immunohistochemical experiments showed that only terminal CGRP is subject to capsaicin-induced depletion in vitro, whereas CGRP-immunoreactivity endures in the nerve fibres. PMID:11226146

  16. New therapeutic opportunities for 5-HT2C receptor ligands in neuropsychiatric disorders.

    PubMed

    Di Giovanni, Giuseppe; De Deurwaerdère, Philippe

    2016-01-01

    The 5-HT2C receptor (R) displays a widespread distribution in the CNS and is involved in the action of 5-HT in all brain areas. Knowledge of its functional role in the CNS pathophysiology has been impaired for many years due to the lack of drugs capable of discriminating among 5-HT2R subtypes, and to a lesser extent to the 5-HT1B, 5-HT5, 5-HT6 and 5-HT7Rs. The situation has changed since the mid-90s due to the increased availability of new and selective synthesized compounds, the creation of 5-HT2C knock out mice, and the progress made in molecular biology. Many pharmacological classes of drugs including antipsychotics, antidepressants and anxiolytics display affinities toward 5-HT2CRs and new 5-HT2C ligands have been developed for various neuropsychiatric disorders. The 5-HT2CR is presumed to mediate tonic/constitutive and phasic controls on the activity of different central neurobiological networks. Preclinical data illustrate this complexity to a point that pharmaceutical companies developed either agonists or antagonists for the same disease. In order to better comprehend this complexity, this review will briefly describe the molecular pharmacology of 5-HT2CRs, as well as their cellular impacts in general, before addressing its central distribution in the mammalian brain. Thereafter, we review the preclinical efficacy of 5-HT2C ligands in numerous behavioral tests modeling human diseases, highlighting the multiple and competing actions of the 5-HT2CRs in neurobiological networks and monoaminergic systems. Notably, we will focus this evidence in the context of the physiopathology of psychiatric and neurological disorders including Parkinson's disease, levodopa-induced dyskinesia, and epilepsy. PMID:26617215

  17. Antiallodynic effect of tianeptine via modulation of the 5-HT7 receptor of GABAergic interneurons in the spinal cord of neuropathic rats.

    PubMed

    Lin, Hai; Heo, Bong Ha; Kim, Woong Mo; Kim, Yong Chul; Yoon, Myung Ha

    2015-06-26

    Although tianeptine, an atypical antidepressant has been reported to have antinociceptive effects, the mode of action is different from that of tricyclic antidepressants despite structural similarities. We examined the antiallodynic effect of intrathecal tianeptine in neuropathic pain rats and determined the involvement of 5-hydroxytryptamine type 7 (5-HT7) receptor of the GABAergic interneurons in the spinal cord. Neuropathic pain was induced by spinal nerve ligation (SNL). After observation of the effect from intrathecal tianeptine, a 5-HT7 receptor antagonist (SB-269970) was administered intrathecally 10 min before delivery of tianeptine, to determine the contribution of spinal 5-HT7 receptor on the activity of tianeptine. GAD expression and GABA concentrations were assessed. Intrathecal tianeptine dose-dependently attenuated mechanical allodynia in SNL rats. Pre-treatment with intrathecal SB-269970 reversed the antiallodynic effect of tianeptine. Both GAD65 expression and the GABA concentration in the spinal cord were decreased in neuropathic rats but were increased by tianeptine. Additionally, 5-HT7 receptor and GAD65 were co-localized in the spinal cord. Intrathecal tianeptine reduces neuropathic pain. 5-HT7 receptor of the GABAergic interneurons together with GAD65 plays a role in the activity of tianeptine at the spinal cord level. PMID:25982324

  18. 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. PMID:15574737

  19. Osmoregulation of vasopressin secretion via activation of neurohypophysial nerve terminals glycine receptors by glial taurine.

    PubMed

    Hussy, N; Brès, V; Rochette, M; Duvoid, A; Alonso, G; Dayanithi, G; Moos, F C

    2001-09-15

    Osmotic regulation of supraoptic nucleus (SON) neuron activity depends in part on activation of neuronal glycine receptors (GlyRs), most probably by taurine released from adjacent astrocytes. In the neurohypophysis in which the axons of SON neurons terminate, taurine is also concentrated in and osmo-dependently released by pituicytes, the specialized glial cells ensheathing nerve terminals. We now show that taurine release from isolated neurohypophyses is enhanced by hypo-osmotic and decreased by hyper-osmotic stimulation. The high osmosensitivity is shown by the significant increase on only 3.3% reduction in osmolarity. Inhibition of taurine release by 5-nitro-2-(3-phenylpropylamino)benzoic acid, niflumic acid, and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid suggests the involvement of volume-sensitive anion channels. On purified neurohypophysial nerve endings, activation of strychnine-sensitive GlyRs by taurine or glycine primarily inhibits the high K(+)-induced rise in [Ca(2+)](i) and subsequent release of vasopressin. Expression of GlyRs in vasopressin and oxytocin terminals is confirmed by immunohistochemistry. Their implication in the osmoregulation of neurohormone secretion was assessed on isolated whole neurohypophyses. A 6.6% hypo-osmotic stimulus reduces by half the depolarization-evoked vasopressin secretion, an inhibition totally prevented by strychnine. Most importantly, depletion of taurine by a taurine transport inhibitor also abolishes the osmo-dependent inhibition of vasopressin release. Therefore, in the neurohypophysis, an osmoregulatory system involving pituicytes, taurine, and GlyRs is operating to control Ca(2+) influx in and neurohormone release from nerve terminals. This elucidates the functional role of glial taurine in the neurohypophysis, reveals the expression of GlyRs on axon terminals, and further defines the role of glial cells in the regulation of neuroendocrine function. PMID:11549721

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

    PubMed

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

    2016-09-15

    Lacosamide is an anti-epileptic drug that is also used for the treatment of painful diabetic neuropathy acting through voltage-gated sodium channels. The aim of this work was to evaluate the effects of acute application of lacosamide on the electrical activity of corneal cold nerve terminals in lacrimo-deficient guinea pigs. Four weeks after unilateral surgical removal of the main lachrimal gland in guinea pigs, corneas were excised and superfused in vitro at 34°C for extracellular electrophysiological recording of nerve terminal impulse activity of cold thermosensitive nerve terminals. The characteristics of the spontaneous and the stimulus-evoked (cooling ramps from 34°C to 15°C) activity before and in presence of lacosamide 100µM and lidocaine 100µM were compared. Cold nerve terminals (n=34) recorded from dry eye corneas showed significantly enhanced spontaneous activity (8.0±1.1 vs. 5.2±0.7imp/s; P<0.05) and cold response (21.2±1.7 vs. 16.8±1.3imp/s; P<0.05) as well as reduced cold threshold (1.5±0.1 vs. 2.8±0.2 Δ°C; P<0.05) to cooling ramps compared to terminals (n=58) from control animals. Both lacosamide and lidocaine decreased spontaneous activity and peak response to cooling ramps significantly (P<0.05). Temperature threshold was increased by the addition of lidocaine (P<0.05) but not lacosamide (P>0.05) to the irrigation fluid. In summary, the application of lacosamide results in a significant decrease of the augmented spontaneous activity and responsiveness to cold of corneal sensory nerves from tear-deficient animals. Based on these promising results we speculate that lacosamide might be used to reduce the hyperexcitability of corneal cold receptors caused by prolonged ocular surface dryness due to hyposecretory or evaporative dry eye disease. PMID:27263827

  1. Evidence that 5-HT1D receptors mediate inhibition of sympathetic ganglionic transmission in anaesthetized cats.

    PubMed Central

    Jones, J. F.; Martin, G. R.; Ramage, A. G.

    1995-01-01

    In anaesthetized cats, 5-carboxamidotryptamine (5-CT) or 5-hydroxytryptamine (5-HT) (0.3-300 micrograms kg-1,i.v.) inhibited the postganglionic compound action potential evoked by preganglionic electrical stimulation (0.5 Hz) with a similar potency in the stellate and splanchnic ganglia. In the 5-HT experiments transmission thorough the inferior mesenteric ganglia was also recorded. The maximal inhibitory effect of 5-HT was greater on the stellate and splanchnic ganglia (60 +/- 4 and 52 +/- 5%) than on the inferior mesenteric (15 +/- 2%). The effects of 5-HT were unaffected by pretreatment with antagonists (1 mg kg-1;i.v.) for 5-HT2 (BW501C67), 5-HT1A (WAY-100635) and 5-HT3 receptors (ondansetron). However, responses to both 5-HT and 5-CT were attenuated significantly by GR127935 (1 mg kg-1) except the responses to 5-HT at the inferior mesenteric ganglia. These results are consistent with the involvement of 5-HT1D receptors mediating inhibition of sympathetic ganglionic transmission in vivo. PMID:8528548

  2. Analysis of the agonist activity of fenoldopam (SKF 82526) at the vascular 5-HT2 receptor.

    PubMed Central

    Christie, M. I.; Harper, D.; Smith, G. W.

    1992-01-01

    1. The 5-HT2 receptor agonist activity of fenoldopam (SKF 82526) was characterized in the rabbit isolated aorta preparation. 2. Fenoldopam was an agonist at the vascular 5-HT2 receptor with lower affinity and efficacy than the naturally occurring agonist 5-hydroxytryptamine (5-HT). Fenoldopam had an affinity (pKA) of 5.84 +/- 0.04 and efficacy (tau) of 0.57 +/- 0.04, whereas 5-HT had a pKA of 6.65 +/- 0.12 and tau of 2.66 +/- 0.41. 3. The constrictor effects of fenoldopam and 5-HT were competitively antagonized by the 5-HT2 antagonist, ketanserin, with pKB values of 8.81 +/- 0.11 and 8.83 +/- 0.10 respectively. 4. Prior incubation with fenoldopam produced a concentration-related rightward shift of a subsequent 5-HT concentration-response curve. This inhibition was specific for 5-HT since constrictor responses to angiotensin II were unaffected. 5. This study indicates that the D1 receptor agonist, fenoldopam, acts as an agonist at the vascular 5-HT2 receptor, but with an affinity and efficacy less than that of the naturally occurring agonist, 5-HT. PMID:1361397

  3. Organization of the mouse 5-HT3 receptor gene and functional expression of two splice variants.

    PubMed

    Werner, P; Kawashima, E; Reid, J; Hussy, N; Lundström, K; Buell, G; Humbert, Y; Jones, K A

    1994-10-01

    The structure of the mouse 5-HT3 receptor gene, 5-HT3R-A, is most similar to nicotinic acetylcholine receptor (nAChR) genes, in particular to the gene encoding the neuronal nAChR subunit alpha 7. These genes share among other things the location of three adjacent introns, suggesting that 5-HT3R-A and nAChR genes arose from a common precursor gene. The alternative use of two adjacent splice acceptor sites in intron 8 creates, in addition to the original 5-HT3R-A cDNA (5-HT3R-AL), a shorter isoform (5-HT3R-AS) which lacks six codons in the segment that translates into the major intracellular domain. This splice consensus sequence is not found in human genomic DNA. In mouse, we demonstrate by RNAse protection assay that 5-HT3R-AS mRNA is approximately 5 times more abundant than 5-HT3R-AL mRNA in both neuroblastoma cell lines and neuronal tissues. We used the Semliki Forest virus expression system for electrophysiological characterization of 5-HT3R-AS and 5-HT3R-AL in mammalian cells. No differences in electrophysiological characteristics, such as voltage dependence, desensitization kinetics, or unitary conductance were found between homomeric 5-HT3R-AS and 5-HT3R-AL receptors. Their properties are very similar to those of 5-HT3 receptors in mouse neuroblastoma cell lines. PMID:7854052

  4. 5-HT2A receptors are involved in cognitive but not antidepressant effects of fluoxetine.

    PubMed

    Castañé, Anna; Kargieman, Lucila; Celada, Pau; Bortolozzi, Analía; Artigas, Francesc

    2015-08-01

    The prefrontal cortex (PFC) plays a crucial role in cognitive and affective functions. It contains a rich serotonergic (serotonin, 5-HT) innervation and a high density of 5-HT receptors. Endogenous 5-HT exerts robust actions on the activity of pyramidal neurons in medial PFC (mPFC) via excitatory 5-HT2A and inhibitory 5-HT1A receptors, suggesting the involvement of 5-HT neurotransmission in cortical functions. However, the underlying mechanisms must be elucidated. Here we examine the role of 5-HT2A receptors in the processing of emotional and cognitive signals evoked by increasing the 5-HT tone after acute blockade of the 5-HT transporter. Fluoxetine (5-20mg/kg i.p.) dose-dependently reduced the immobility time in the tail-suspension test in wild-type (WT) and 5-HT2Aknockout (KO2A) mice, with non-significant differences between genotypes. Fluoxetine (10mg/kg i.p.) significantly impaired mice performance in the novel object recognition test 24h post-administration in WT, but not in KO2A mice. The comparable effect of fluoxetine on extracellular 5-HT in the mPFC of both genotypes suggests that presynaptic differences are not accountable. In contrast, single unit recordings of mPFC putative pyramidal neurons showed that fluoxetine (1.8-7.2mg/kg i.v.) significantly increased neuronal discharge in KO2A but not in WT mice. This effect is possibly mediated by an altered excitatory/inhibitory balance in the PFC in KO2A mice. Overall, the present results suggest that 5-HT2A receptors play a detrimental role in long-term memory deficits mediated by an excess 5-HT in PFC. PMID:25914158

  5. 5-HT potentiation of the GABAA response in the rat sacral dorsal commissural neurones

    PubMed Central

    Xu, Tian-Le; Pang, Zhi-Ping; Li, Ji-Shuo; Akaike, Norio

    1998-01-01

    The modulatory effect of 5-hydroxytryptamine (5-HT) on the γ-aminobutyric acidA (GABAA) response was investigated in the neurones freshly dissociated from the rat sacral dorsal commissural nucleus (SDCN) using the nystatin perforated patch recording configuration under the voltage-clamp conditions.5-HT potentiated GABA-induced Cl− current (IGABA) without affecting the reversal potential of IGABA and the apparent affinity of GABA to its receptor.α-Methyl-5-HT mimicked the potentiation effect of 5-HT on IGABA while ketanserine blocked it. 1-Oleoyl-2-acetyl-glycerol (OAG) potentiated IGABA, and the effect of 5-HT on IGABA was occluded by OAG pretreatment. In the presence of chelerythrine, 5-HT failed to potentiate IGABA, suggesting that protein kinase C (PKC) is involved in the pathway through which the activation of the 5-HT2 receptor potentiates the IGABA.The facilitatory effect of 5-HT on IGABA remained in the presence of BAPTA-AM. LiCl also had no effect on 5-HT-induced potentiation of IGABA.H-89, genistein, okadaic acid and pervanadate all had no effects on 5-HT potentiation of IGABA. Pertussis toxin treatment for 6–8 h did not block the facilitatory effect of 5-HT on IGABA.The present results show that GABAA receptor in the rat SDCN could be modulated in situ by 5-HT, one of the major transmitters involved in the supraspinal control of nociception, and that the phosphorylation of GABAA receptor by PKC may be sufficient to support such modulation. The results also strongly support the hypothesis that the cotransmission by 5-HT and GABA has an important role in the spinal cord. PMID:9690871

  6. 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. PMID:26324408

  7. Vortioxetine restores reversal learning impaired by 5-HT depletion or chronic intermittent cold stress in rats.

    PubMed

    Wallace, Ashley; Pehrson, Alan L; Sánchez, Connie; Morilak, David A

    2014-10-01

    Current treatments for depression, including serotonin-specific reuptake inhibitors (SSRIs), are only partially effective, with a high incidence of residual symptoms, relapse, and treatment resistance. Loss of cognitive flexibility, a component of depression, is associated with dysregulation of the prefrontal cortex. Reversal learning, a form of cognitive flexibility, is impaired by chronic stress, a risk factor for depression, and the stress-induced impairment in reversal learning is sensitive to chronic SSRI treatment, and is mimicked by serotonin (5-HT) depletion. Vortioxetine, a novel, multimodal-acting antidepressant, is a 5-HT3, 5-HT7 and 5-HT1D receptor antagonist, a 5-HT1B receptor partial agonist, a 5-HT1A receptor agonist, and inhibits the 5-HT transporter. Using adult male rats, we first investigated the direct effects of vortioxetine, acting at post-synaptic 5-HT receptors, on reversal learning that was compromised by 5-HT depletion using 4-chloro-DL-phenylalanine methyl ester hydrochloride (PCPA), effectively eliminating any contribution of 5-HT reuptake blockade. PCPA induced a reversal learning impairment that was alleviated by acute or sub-chronic vortioxetine administration, suggesting that post-synaptic 5-HT receptor activation contributes to the effects of vortioxetine. We then investigated the effects of chronic dietary administration of vortioxetine on reversal learning that had been compromised in intact animals exposed to chronic intermittent cold (CIC) stress, to assess vortioxetine's total pharmacological effect. CIC stress impaired reversal learning, and chronic vortioxetine administration prevented the reversal-learning deficit. Together, these results suggest that the direct effect of vortioxetine at 5-HT receptors may contribute to positive effects on cognitive flexibility deficits, and may enhance the effect of 5-HT reuptake blockade. PMID:24852131

  8. A novel aminotetralin-type serotonin (5-HT) 2C receptor-specific agonist and 5-HT2A competitive antagonist/5-HT2B inverse agonist with preclinical efficacy for psychoses.

    PubMed

    Canal, Clinton E; Morgan, Drake; Felsing, Daniel; Kondabolu, Krishnakanth; Rowland, Neil E; Robertson, Kimberly L; Sakhuja, Rajeev; Booth, Raymond G

    2014-05-01

    Development of 5-HT2C agonists for treatment of neuropsychiatric disorders, including psychoses, substance abuse, and obesity, has been fraught with difficulties, because the vast majority of reported 5-HT2C selective agonists also activate 5-HT2A and/or 5-HT2B receptors, potentially causing hallucinations and/or cardiac valvulopathy. Herein is described a novel, potent, and efficacious human 5-HT2C receptor agonist, (-)-trans-(2S,4R)-4-(3'[meta]-bromophenyl)-N,N-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine (-)-MBP), that is a competitive antagonist and inverse agonist at human 5-HT2A and 5-HT2B receptors, respectively. (-)-MBP has efficacy comparable to the prototypical second-generation antipsychotic drug clozapine in three C57Bl/6 mouse models of drug-induced psychoses: the head-twitch response elicited by [2,5]-dimethoxy-4-iodoamphetamine; hyperlocomotion induced by MK-801 [(5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (dizocilpine maleate)]; and hyperlocomotion induced by amphetamine. (-)-MBP, however, does not alter locomotion when administered alone, distinguishing it from clozapine, which suppresses locomotion. Finally, consumption of highly palatable food by mice was not increased by (-)-MBP at a dose that produced at least 50% maximal efficacy in the psychoses models. Compared with (-)-MBP, the enantiomer (+)-MBP was much less active across in vitro affinity and functional assays using mouse and human receptors and also translated in vivo with comparably lower potency and efficacy. Results indicate a 5-HT2C receptor-specific agonist, such as (-)-MBP, may be pharmacotherapeutic for psychoses, without liability for obesity, hallucinations, heart disease, sedation, or motoric disorders. PMID:24563531

  9. A Novel Aminotetralin-Type Serotonin (5-HT) 2C Receptor-Specific Agonist and 5-HT2A Competitive Antagonist/5-HT2B Inverse Agonist with Preclinical Efficacy for Psychoses

    PubMed Central

    Morgan, Drake; Felsing, Daniel; Kondabolu, Krishnakanth; Rowland, Neil E.; Robertson, Kimberly L.; Sakhuja, Rajeev; Booth, Raymond G.

    2014-01-01

    Development of 5-HT2C agonists for treatment of neuropsychiatric disorders, including psychoses, substance abuse, and obesity, has been fraught with difficulties, because the vast majority of reported 5-HT2C selective agonists also activate 5-HT2A and/or 5-HT2B receptors, potentially causing hallucinations and/or cardiac valvulopathy. Herein is described a novel, potent, and efficacious human 5-HT2C receptor agonist, (−)-trans-(2S,4R)-4-(3′[meta]-bromophenyl)-N,N-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine (−)-MBP), that is a competitive antagonist and inverse agonist at human 5-HT2A and 5-HT2B receptors, respectively. (−)-MBP has efficacy comparable to the prototypical second-generation antipsychotic drug clozapine in three C57Bl/6 mouse models of drug-induced psychoses: the head-twitch response elicited by [2,5]-dimethoxy-4-iodoamphetamine; hyperlocomotion induced by MK-801 [(5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (dizocilpine maleate)]; and hyperlocomotion induced by amphetamine. (−)-MBP, however, does not alter locomotion when administered alone, distinguishing it from clozapine, which suppresses locomotion. Finally, consumption of highly palatable food by mice was not increased by (−)-MBP at a dose that produced at least 50% maximal efficacy in the psychoses models. Compared with (−)-MBP, the enantiomer (+)-MBP was much less active across in vitro affinity and functional assays using mouse and human receptors and also translated in vivo with comparably lower potency and efficacy. Results indicate a 5-HT2C receptor-specific agonist, such as (−)-MBP, may be pharmacotherapeutic for psychoses, without liability for obesity, hallucinations, heart disease, sedation, or motoric disorders. PMID:24563531

  10. Yokukansan Increases 5-HT1A Receptors in the Prefrontal Cortex and Enhances 5-HT1A Receptor Agonist-Induced Behavioral Responses in Socially Isolated Mice

    PubMed Central

    Ueki, Toshiyuki; Mizoguchi, Kazushige; Yamaguchi, Takuji; Nishi, Akinori; Ikarashi, Yasushi; Hattori, Tomohisa; Kase, Yoshio

    2015-01-01

    The traditional Japanese medicine yokukansan has an anxiolytic effect, which occurs after repeated administration. In this study, to investigate the underlying mechanisms, we examined the effects of repeated yokukansan administration on serotonin 1A (5-HT1A) receptor density and affinity and its expression at both mRNA and protein levels in the prefrontal cortex (PFC) of socially isolated mice. Moreover, we examined the effects of yokukansan on a 5-HT1A receptor-mediated behavioral response. Male mice were subjected to social isolation stress for 6 weeks and simultaneously treated with yokukansan. Thereafter, the density and affinity of 5-HT1A receptors were analyzed by a receptor-binding assay. Levels of 5-HT1A receptor protein and mRNA were also measured. Furthermore, (±)-8-hydroxy-2-(dipropylamino)tetralin hydrobromide (8-OH-DPAT; a 5-HT1A receptor agonist) was injected intraperitoneally, and rearing behavior was examined. Social isolation stress alone did not affect 5-HT1A receptor density or affinity. However, yokukansan significantly increased receptor density and decreased affinity concomitant with unchanged protein and mRNA levels. Yokukansan also enhanced the 8-OH-DPAT-induced decrease in rearing behavior. These results suggest that yokukansan increases 5-HT1A receptors in the PFC of socially isolated mice and enhances their function, which might underlie its anxiolytic effects. PMID:26681968

  11. Functional selectivity of hallucinogenic phenethylamine and phenylisopropylamine derivatives at human 5-hydroxytryptamine (5-HT)2A and 5-HT2C receptors.

    PubMed

    Moya, Pablo R; Berg, Kelly A; Gutiérrez-Hernandez, Manuel A; Sáez-Briones, Patricio; Reyes-Parada, Miguel; Cassels, Bruce K; Clarke, William P

    2007-06-01

    2,5-Dimethoxy-4-substituted phenylisopropylamines and phenethylamines are 5-hydroxytryptamine (serotonin) (5-HT)(2A/2C) agonists. The former are partial to full agonists, whereas the latter are partial to weak agonists. However, most data come from studies analyzing phospholipase C (PLC)-mediated responses, although additional effectors [e.g., phospholipase A(2) (PLA(2))] are associated with these receptors. We compared two homologous series of phenylisopropylamines and phenethylamines measuring both PLA(2) and PLC responses in Chinese hamster ovary-K1 cells expressing human 5-HT(2A) or 5-HT(2C) receptors. In addition, we assayed both groups of compounds as head shake inducers in rats. At the 5-HT(2C) receptor, most compounds were partial agonists for both pathways. Relative efficacy of some phenylisopropylamines was higher for both responses compared with their phenethylamine counterparts, whereas for others, no differences were found. At the 5-HT(2A) receptor, most compounds behaved as partial agonists, but unlike findings at 5-HT(2C) receptors, all phenylisopropylamines were more efficacious than their phenethylamine counterparts. 2,5-Dimethoxyphenylisopropylamine activated only the PLC pathway at both receptor subtypes, 2,5-dimethoxyphenethylamine was selective for PLC at the 5-HT(2C) receptor, and 2,5-dimethoxy-4-nitrophenethylamine was PLA(2)-specific at the 5-HT(2A) receptor. For both receptors, the rank order of efficacy of compounds differed depending upon which response was measured. The phenylisopropylamines were strong head shake inducers, whereas their phenethylamine congeners were not, in agreement with in vitro results and the involvement of 5-HT(2A) receptors in the head shake response. Our results support the concept of functional selectivity and indicate that subtle changes in ligand structure can result in significant differences in the cellular signaling profile. PMID:17337633

  12. 5-HT(2A) receptor blockade and 5-HT(2C) receptor activation interact to reduce cocaine hyperlocomotion and Fos protein expression in the caudate-putamen.

    PubMed

    Pockros, Lara A; Pentkowski, Nathan S; Conway, Sineadh M; Ullman, Teresa E; Zwick, Kimberly R; Neisewander, Janet L

    2012-12-01

    Both the 5-HT(2A) receptor (R) antagonist M100907 and the 5-HT(2C) R agonist MK212 attenuate cocaine-induced dopamine release and hyperlocomotion. This study examined whether these drugs interact to reduce cocaine hyperlocomotion and Fos expression in the striatum and prefrontal cortex. We first determined from dose-effect functions a low dose of both M100907 and MK212 that failed to alter cocaine (15 mg/kg, i.p.) hyperlocomotion. Subsequently, we examined whether these subthreshold doses given together would attenuate cocaine hyperlocomotion, consistent with a 5-HT(2A)/5-HT(2C) R interaction. Separate groups of rats received two sequential drug injections 5 min apart immediately before a 1-h locomotion test as follows: (1) saline + saline, (2) saline + cocaine, (3) 0.025 mg/kg M100907 + cocaine, (4) 0.125 mg/kg MK212 + cocaine, or (5) cocktail combination of 0.025 mg/kg M100907 and 0.125 mg/kg MK212 + cocaine. Brains were extracted for Fos immunohistochemistry 90 min after the second injection. We next examined the effects of 0.025 mg/kg M100907 and 0.125 mg/kg MK212, alone and in combination, on spontaneous locomotor activity. While neither drug given alone produced any effects, the M100907/MK212 cocktail attenuated cocaine hyperlocomotion as well as cocaine-induced Fos expression in the dorsolateral caudate-putamen (CPu), but had no effect on spontaneous locomotion. The findings suggest that 5-HT(2A) Rs and 5-HT(2C) Rs interact to attenuate cocaine hyperlocomotion and Fos expression in the CPu, and that the CPu is a potential locus of the interactive effects between these 5-HT(2) R subtypes on behavior. Further research investigating combined 5-HT(2A) R antagonism and 5-HT(2C) R agonism as a treatment for cocaine dependence is warranted. PMID:22886755

  13. 5-HT2A receptor blockade and 5-HT2C receptor activation interact to reduce cocaine hyperlocomotion and Fos protein expression in the caudate-putamen

    PubMed Central

    Pockros, Lara A.; Pentkowski, Nathan S.; Conway, Sineadh M.; Ullman, Teresa E.; Zwick, Kimberly R.; Neisewander, Janet L.

    2012-01-01

    Both the 5-HT2A receptor (R) antagonist M100907 and the 5-HT2CR agonist MK212 attenuate cocaine-induced dopamine release and hyperlocomotion. This study examined whether these drugs interact to reduce cocaine hyperlocomotion and Fos expression in the striatum and prefrontal cortex. We first determined from dose-effect functions a low dose of both M100907 and MK212 that failed to alter cocaine (15 mg/kg, i.p.) hyperlocomotion. Subsequently we examined whether these subthreshold doses given together would attenuate cocaine hyperlocomotion, consistent with a 5-HT2A/5-HT2CR interaction. Separate groups of rats received two sequential drug injections 5 min apart immediately before a 1-h locomotion test as follows: 1) saline + saline, 2) saline + cocaine, 3) 0.025 mg/kg M100907 + cocaine, 4) 0.125 mg/kg MK212 + cocaine, or 5) cocktail combination of 0.025 mg/kg M100907 and 0.125 mg/kg MK212 + cocaine. Brains were extracted for Fos immunohistochemistry 90 min after the second injection. We next examined the effects of 0.025 mg/kg M100907 and 0.125 mg/kg MK212, alone and in combination, on spontaneous locomotor activity. While neither drug given alone produced any effects, the M100907/MK212 cocktail attenuated cocaine hyperlocomotion as well as cocaine-induced Fos expression in the dorsolateral caudate-putamen (CPu), but had no effect on spontaneous locomotion. The findings suggest that 5-HT2ARs and 5-HT2CRs interact to attenuate cocaine hyperlocomotion and Fos expression in the CPu, and that the CPu is a potential locus of the interactive effects between these 5-HT2R subtypes on behavior. Further research investigating combined 5-HT2AR antagonism and 5-HT2CR agonism as a treatment for cocaine dependence is warranted. PMID:22886755

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  15. Serotonin 5-HT3 receptors in rat CA1 hippocampal interneurons: functional and molecular characterization

    PubMed Central

    Sudweeks, Sterling N; van Hooft, Johannes A; Yakel, Jerrel L

    2002-01-01

    The molecular makeup of the serotonin 5-HT3 receptor (5-HT3R) channel was investigated in rat hippocampal CA1 interneurons in slices using single-cell RT-PCR and patch-clamp recording techniques. We tested for the expression of the 5-HT3A (both short and long splice variants) and 5-HT3B subunits, as well as the expression of the α4 subunit of the neuronal nicotinic ACh receptors (nAChRs), the latter of which has been shown to co-assemble with the 5-HT3A subunit in heterologous expression systems. Both the 5-HT3A-short and α4-nAChR subunits were expressed in these interneurons, but we could not detect any expression of either the 5-HT3B or the 5-HT3A-long subunits. Furthermore, there was a strong tendency for the 5-HT3A-short and α4-nAChR subunits to be co-expressed in individual interneurons. To assess whether there was any functional evidence for co-assembly between the 5-HT3A-short and α4-nAChR subunits, we used the sulphydryl agent 2-aminoethyl methanethiosulphonate (MTSEA), which has previously been shown to modulate expressed 5-HT3Rs that contain the α4-nAChR subunit. In half of the interneurons examined, MTSEA significantly enhanced the amplitude of the 5-HT3R-mediated responses, which is consistent with the notion that the α4-nAChR subunit co-assembles with the 5-HT3A subunit to form a native heteromeric 5-HT3R channel in rat CA1 hippocampal interneurons in vivo. In addition, the single-channel properties of the 5-HT3R were investigated in outside-out patches. No resolvable single-channel currents were observed. Using non-stationary fluctuation analysis, we obtained an estimate of the single-channel conductance of 4 pS, which is well below that expected for channels containing both the 5-HT3A and 5-HT3B subunits. PMID:12411518

  16. Phosphotidylinositol turnover in vascular, uterine, fundal, and tracheal smooth muscle: effect of serotonin (5HT)

    SciTech Connect

    Cohen, M.L.; Wittenauer, L.A.

    1986-03-01

    In brain, platelets, and aorta, 5HT has been reported to increase phosphotidylinositol turnover, an effect linked to 5HT/sub 2/ receptors. The authors examined the effect of 5HT on /sup 3/H-inositol-1-phosphate (/sup 3/H-I-P) in tissues possessing 5HT/sub 2/ receptors that mediate contraction to 5HT (rat jugular vein, aorta, uterus and guinea pig trachea) and in a tissue in which contraction to 5HT is not mediated by 5HT/sub 2/ receptors (rat stomach fundus). Tissues were incubated (37/sup 0/C, 95% O/sub 2/, 5% CO/sub 2/) with /sup 3/H-inositol (90 min), washed, LiCl/sub 2/ (10 mM) and 5HT added for 90 min, extracted, and /sup 3/H-I-P eluted from a Dowex-1 column. Basal /sup 3/H-I-P was 10-fold higher in the uterus than in the other tissues. 5HT (10/sup -6/-10/sup -4/M) increased /sup 3/H-I-P in the jugular vein, aorta, and uterus but not in the trachea or fundus. Maximum increase was greatest in the jugular vein (8-fold) with an ED/sub 50/ of 0.4 ..mu..M 5HT. The selective 5HT/sub 2/ receptor blocker, LY53857 (10/sup -8/M) antagonized the increase in /sup 3/H-I-P by 5HT in the jugular vein, aorta and uterus. Pargyline (10/sup -5/M) added to the trachea and fundus did not unmask an effect of 5HT (10/sup -4/M). These data suggest that (1) the jugular vein produced the most sensitive response to 5HT-induced increases in /sup 3/H-I-P, (2) increases in /sup 3/H-I-P by 5HT in smooth muscle may be linked to 5HT/sub 2/ receptors and (3) activation of 5HT/sub 2/ receptors as occurred in the trachea will not always increase /sup 3/H-I-P.

  17. INSIGHTS INTO THE REGULATION OF 5-HT2A RECEPTORS BY SCAFFOLDING PROTEINS AND KINASES

    PubMed Central

    Allen, John A.; Yadav, Prem N.

    2008-01-01

    SUMMARY 5-HT2A serotonin receptors are essential molecular targets for the actions of LSD-like hallucinogens and atypical antipsychotic drugs. 5-HT2A serotonin receptors also mediate a variety of physiological processes in peripheral and central nervous systems including platelet aggregation, smooth muscle contraction, and the modulation of mood and perception. Scaffolding proteins have emerged as important regulators of 5-HT2A receptors and our recent studies suggest multiple scaffolds exist for 5-HT2A receptors including PSD95, arrestin, and caveolin. In addition, a novel interaction has emerged between p90 ribosomal S6 kinase and 5-HT2A receptors which attenuates receptor signaling. This article reviews our recent studies and emphasizes the role of scaffolding proteins and kinases in the regulation of 5-HT2A trafficking, targeting and signaling. PMID:18640136

  18. Mechanism for the acute effects of organophosphate pesticides on the adult 5-HT system.

    PubMed

    Judge, Sarah J; Savy, Claire Y; Campbell, Matthew; Dodds, Rebecca; Gomes, Larissa Kruger; Laws, Grace; Watson, Anna; Blain, Peter G; Morris, Christopher M; Gartside, Sarah E

    2016-02-01

    The neurotransmitter serotonin (5-HT) is involved in mood disorder aetiology and it has been reported that (organophosphate) OP exposure affects 5-HT turnover. The aim of this study was to elucidate the mechanism underlying OP effects on the adult 5-HT system. First, acute in vivo administration of the OP diazinon (0, 1.3, 13 or 39 mg/kg i.p.) to male Hooded Lister rats inhibited the activity of the cholinergic enzyme acetylcholinesterase in blood and in the hippocampus, dorsal raphe nucleus (DRN), striatum and prefrontal cortex. Diazinon-induced cholinesterase inhibition was greatest in the DRN, the brain's major source of 5-HT neurones. Second, acute in vivo diazinon exposure (0 or 39 mg/kg i.p.) increased the basal firing rate of DRN neurones measured ex vivo in brain slices. The excitatory responses of DRN neurones to α1-adrenoceptor or AMPA/kainate receptor activation were not affected by in vivo diazinon exposure but the inhibitory response to 5-HT was attenuated, indicating 5-HT1A autoreceptor down-regulation. Finally, direct application of the diazinon metabolite diazinon oxon to naive rat brain slices increased the firing rate of DRN 5-HT neurones, as did chlorpyrifos-oxon, indicating the effect was not unique to diazinon. The oxon-induced augmentation of firing was blocked by the nicotinic acetylcholine receptor antagonist mecamylamine and the AMPA/kainate glutamate receptor antagonist DNQX. Together these data indicate that 1) acute OP exposure inhibits DRN cholinesterase, leading to acetylcholine accumulation, 2) the acetylcholine activates nicotinic receptors on 5-HT neurones and also on glutamatergic neurones, thus releasing glutamate and activating 5-HT neuronal AMPA/kainate receptors 3) the increase in 5-HT neuronal activity, and resulting 5-HT release, may lead to 5-HT1A autoreceptor down-regulation. This mechanism may be involved in the reported increase in risk of developing anxiety and depression following occupational OP exposure. PMID

  19. Sulfonyl-containing modulators of serotonin 5-HT6 receptors and their pharmacophore models

    NASA Astrophysics Data System (ADS)

    Ivachtchenko, A. V.

    2014-05-01

    Data published in recent years on the synthesis of serotonin 5-HT6 receptor modulators are summarized. Modulators with high affinity for 5-HT6 receptors exhibiting different degrees of selectivity — from highly selective to semiselective and multimodal — are described. Clinical trial results are reported for the most promising serotonin 5-HT6 receptor modulators attracting special attention of medicinal chemists. The bibliography includes 128 references.

  20. An electrophysiological analysis of the storage of acetylcholine in preganglionic nerve terminals

    PubMed Central

    Bennett, M. R.; McLachlan, Elspeth M.

    1972-01-01

    1. An electrophysiological analysis has been made of the storage of acetylcholine (ACh) in the preganglionic nerve terminals of the isolated superior cervical ganglion of the guinea-pig. The mean amplitude of excitatory post-synaptic potentials recorded intracellularly was taken as a measure of the ACh output per impulse from the terminals of a preganglionic axon. 2. Prolonged repetitive stimulation of the cervical sympathetic trunk at 10 and 20 Hz in the presence of hemicholinium No. 3 led to an exponential decline of ACh output as the transmitter formed before the beginning of stimulation was depleted. 3. The rate of decline of ACh output during stimulation at 20 Hz (τ = 0·83-1·95 min) was about twice as fast as that at 10 Hz (τ = 1·00-6·83 min). 4. The results suggest that, during prolonged stimulation, ACh is released from a single store in the preganglionic nerve terminal and that each impulse releases a constant fraction of the store of the transmitter. PMID:4335804

  1. Distinct Circuits Underlie the Effects of 5-HT1B Receptors on Aggression and Impulsivity.

    PubMed

    Nautiyal, Katherine M; Tanaka, Kenji F; Barr, Mary M; Tritschler, Laurent; Le Dantec, Yannick; David, Denis J; Gardier, Alain M; Blanco, Carlos; Hen, René; Ahmari, Susanne E

    2015-05-01

    Impulsive and aggressive behaviors are both modulated by serotonergic signaling, specifically through the serotonin 1B receptor (5-HT1BR). 5-HT1BR knockout mice show increased aggression and impulsivity, and 5-HT1BR polymorphisms are associated with aggression and drug addiction in humans. To dissect the mechanisms by which the 5-HT1BR affects these phenotypes, we developed a mouse model to spatially and temporally regulate 5-HT1BR expression. Our results demonstrate that forebrain 5-HT1B heteroreceptors expressed during an early postnatal period contribute to the development of the neural systems underlying adult aggression. However, distinct heteroreceptors acting during adulthood are involved in mediating impulsivity. Correlating with the impulsivity, dopamine in the nucleus accumbens is elevated in the absence of 5-HT1BRs and normalized following adult rescue of the receptor. Overall, these data show that while adolescent expression of 5-HT1BRs influences aggressive behavior, a distinct set of 5-HT1B receptors modulates impulsive behavior during adulthood. PMID:25892302

  2. The 5-HT3 receptor is essential for exercise-induced hippocampal neurogenesis and antidepressant effects.

    PubMed

    Kondo, M; Nakamura, Y; Ishida, Y; Shimada, S

    2015-11-01

    Exercise has a variety of beneficial effects on brain structure and function, such as hippocampal neurogenesis, mood and memory. Previous studies have shown that exercise enhances hippocampal neurogenesis, induces antidepressant effects and improves learning behavior. Brain serotonin (5-hydroxytryptamine, 5-HT) levels increase following exercise, and the 5-HT system has been suggested to have an important role in these exercise-induced neuronal effects. However, the precise mechanism remains unclear. In this study, analysis of the 5-HT type 3A receptor subunit-deficient (htr3a(-/-)) mice revealed that lack of the 5-HT type 3 (5-HT3) receptor resulted in loss of exercise-induced hippocampal neurogenesis and antidepressant effects, but not of learning enhancement. Furthermore, stimulation of the 5-HT3 receptor promoted neurogenesis. These findings demonstrate that the 5-HT3 receptor is the critical target of 5-HT action in the brain following exercise, and is indispensable for hippocampal neurogenesis and antidepressant effects induced by exercise. This is the first report of a pivotal 5-HT receptor subtype that has a fundamental role in exercise-induced morphological changes and psychological effects. PMID:25403840

  3. Distinct circuits underlie the effects of 5-HT1B receptors on aggression and impulsivity

    PubMed Central

    Nautiyal, Katherine M.; Tanaka, Kenji F.; Barr, Mary M.; Tritschler, Laurent; Le Dantec, Yannick; David, Denis J.; Gardier, Alain M.; Blanco, Carlos; Hen, René; Ahmari, Susanne E.

    2015-01-01

    Summary Impulsive and aggressive behaviors are both modulated by serotonergic signaling, specifically through the serotonin 1B receptor (5-HT1BR). 5-HT1BR knockout mice show increased aggression and impulsivity, and 5-HT1BR polymorphisms are associated with aggression and drug addiction in humans. To dissect the mechanisms by which the 5-HT1BR affects these phenotypes, we developed a mouse model to spatially and temporally regulate 5-HT1BR expression. Our results demonstrate that forebrain 5-HT1B heteroreceptors expressed during an early postnatal period contribute to the development of the neural systems underlying adult aggression. However, distinct heteroreceptors acting during adulthood are involved in mediating impulsivity. Correlating with the impulsivity, dopamine in the nucleus accumbens is elevated in the absence of 5-HT1BRs, and normalized following adult rescue of the receptor. Overall, these data show that while adolescent expression of 5-HT1BRs influences aggressive behavior, a distinct set of 5-HT1B receptors modulate impulsive behavior during adulthood. PMID:25892302

  4. Synthesis and biological evaluation of 4-nitroindole derivatives as 5-HT2A receptor antagonists.

    PubMed

    Hayat, Faisal; Viswanath, Ambily Nath Indu; Pae, Ae Nim; Rhim, Hyewhon; Park, Woo-Kyu; Choo, Hea-Young Park

    2015-03-15

    A novel series of 4-nitroindole sulfonamides containing a methyleneamino-N,N-dimethylformamidine were prepared. The binding of these compounds to 5-HT2A and 5-HT2C was evaluated, and most of the compounds showed IC50 values of less than 1μM, and exhibited high selectivity for the 5-HT2C receptor. However, little selectivity was observed in the functional assay for 5-HT6 receptors. The computational modeling studies further validated the biological results and also demonstrated a reasonable correlation between the activity of compounds and the mode of superimposition with specified pharmacophoric features. PMID:25684421

  5. 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptor mRNA modulation by antidepressant treatment in the chronic mild stress model of depression: sex differences exposed.

    PubMed

    Pitychoutis, P M; Dalla, C; Sideris, A C; Tsonis, P A; Papadopoulou-Daifoti, Z

    2012-05-17

    It is well established that women experience major depression at roughly twice the rate of men. Interestingly, accumulating clinical and experimental evidence shows that the responsiveness of males and females to antidepressant pharmacotherapy, and particularly to tricyclic antidepressants (TCAs), is sex-differentiated. Herein, we investigated whether exposure of male and female rats to the chronic mild stress (CMS) model of depression, as well as treatment with the TCA clomipramine may affect serotonergic receptors' (5-HTRs) mRNA expression in a sex-dependent manner. Male and female rats were subjected to CMS for 4 weeks and during the next 4 weeks they concurrently received clomipramine treatment (10 mg/ml/kg). CMS and clomipramine's effects on 5-HT(1A)R, 5-HT(2A)R, and 5-HT(2C)R mRNA expression were assessed by in situ hybridization histochemistry in selected subfields of the hippocampus and in the lateral orbitofrontal cortex (OFC), two regions implicated in the pathophysiology of major depression. CMS and clomipramine treatment induced sex-differentiated effects on rats' hedonic status and enhanced 5-HT(1A)R mRNA expression in the cornu ammonis 1 (CA1) hippocampal region of male rats. Additionally, CMS attenuated 5-HT(1A)R mRNA expression in the OFC of male rats and clomipramine reversed this effect. Moreover, 5-HT(2A)R mRNA levels in the OFC were enhanced in females but decreased in males, while clomipramine reversed this effect only in females. CMS increased 5-HT2CR mRNA expression in the CA4 region of both sexes and this effect was attenuated by clomipramine. Present data exposed that both CMS and clomipramine treatment may induce sex-differentiated and region-distinctive effects on 5-HTRs mRNA expression and further implicate the serotonergic system in the manifestation of sexually dimorphic neurobehavioral responses to stress. PMID:22441040

  6. Phosphatidylinositol 3-Kinase Couples Localised Calcium Influx to Activation of Akt in Central Nerve Terminals.

    PubMed

    Nicholson-Fish, Jessica C; Cousin, Michael A; Smillie, Karen J

    2016-03-01

    The efficient retrieval of synaptic vesicle membrane and cargo in central nerve terminals is dependent on the efficient recruitment of a series of endocytosis modes by different patterns of neuronal activity. During intense neuronal activity the dominant endocytosis mode is activity-dependent endocytosis (ADBE). Triggering of ADBE is linked to calcineurin-mediated dynamin I dephosphorylation since the same stimulation intensities trigger both. Dynamin I dephosphorylation is maximised by a simultaneous inhibition of its kinase glycogen synthase kinase 3 (GSK3) by the protein kinase Akt, however it is unknown how increased neuronal activity is transduced into Akt activation. To address this question we determined how the activity-dependent increases in intracellular free calcium ([Ca(2+)]i) control activation of Akt. This was achieved using either trains of high frequency action potentials to evoke localised [Ca(2+)]i increases at active zones, or a calcium ionophore to raise [Ca(2+)]i uniformly across the nerve terminal. Through the use of either non-specific calcium channel antagonists or intracellular calcium chelators we found that Akt phosphorylation (and subsequent GSK3 phosphorylation) was dependent on localised [Ca(2+)]i increases at the active zone. In an attempt to determine mechanism, we antagonised either phosphatidylinositol 3-kinase (PI3K) or calmodulin. Activity-dependent phosphorylation of both Akt and GSK3 was arrested on inhibition of PI3K, but not calmodulin. Thus localised calcium influx in central nerve terminals activates PI3K via an unknown calcium sensor to trigger the activity-dependent phosphorylation of Akt and GSK3. PMID:26198194

  7. Fangchinoline inhibits glutamate release from rat cerebral cortex nerve terminals (synaptosomes).

    PubMed

    Lin, Tzu-Yu; Lu, Cheng-Wei; Tien, Lu-Tai; Chuang, Shu-Han; Wang, Yu-Ru; Chang, Wen-Hsuan; Wang, Su-Jane

    2009-07-01

    Fangchinoline, an active component of radix stephaniae tetrandrinea, has been shown to possess neuroprotective properties. It has been reported that excessive glutamate release has been proposed to be involved in the pathogenesis of several neurological diseases. The primary purpose of the present study was to investigate the effect of fangchinoline on glutamate release in rat cerebral cortex nerve terminals and to explore the possible mechanism. Fangchinoline inhibited the release of glutamate evoked by 4-aminopyridine (4-AP) in a concentration-dependent manner, and this phenomenon resulted from a reduction of vesicular exocytosis but not from an inhibition of Ca(2+)-independent efflux via glutamate transporter. Fangchinoline did not alter the resting synaptosomal membrane potential or 4-AP-mediated depolarization, but significantly reduced depolarization-induced increase in [Ca(2+)](C). Fangchinoline-mediated inhibition of glutamate release was significantly prevented by the N- and P/Q-type Ca(2+) channel blocker omega-conotoxin MVIIC, and by the PKC inhibitors, GF109203X and Ro318220. In addition, the glutamate release mediated by direct Ca(2+) entry with Ca(2+) ionophore (ionomycin) was unaffected by fangchinoline, which suggests that the inhibitory effect of fangchinoline is not due to directly interfering with the release process at some point subsequent to Ca(2+) influx. These results suggest that fangchinoline inhibits glutamate release from the rat cortical synaptosomes through the suppression of voltage-dependent Ca(2+) channel activity and subsequent reduces Ca(2+) entry into nerve terminals, rather than any upstream effect on nerve terminal excitability. This inhibition appears to involve the suppression of PKC signal transduction pathway. This finding may explain the neuroprotective effects of fangchinoline against neurotoxicity. PMID:19428795

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

    PubMed

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

    2016-01-28

    In the spinal dorsal horn (DH), nerve injury activates microglia and induces neuropathic pain. Several studies clarified an involvement of adenosine triphosphate (ATP) in the microglial activation. However, the origin of ATP together with the release mechanism is unclear. Recent in vitro study revealed that an ATP marker, quinacrine, in lysosomes was released from neurite terminal of dorsal root ganglion (DRG) neurons to extracellular space via lysosomal exocytosis. Here, we demonstrate a possibility that the lysosomal ingredient including ATP released from DRG neurons by lysosomal-exocytosis is an additional source of the glial activation in DH after nerve injury. After rat L5 spinal nerve ligation (SNL), mRNA for transcription factor EB (TFEB), a transcription factor controlling lysosomal activation and exocytosis, was induced in the DRG. Simultaneously both lysosomal protein, LAMP1- and vesicular nuclear transporter (VNUT)-positive vesicles were increased in L5 DRG neurons and ipsilateral DH. The quinacrine staining in DH was increased and co-localized with LAMP1 immunoreactivity after nerve injury. In DH, LAMP1-positive vesicles were also co-localized with a peripheral nerve marker, Isolectin B4 (IB4) lectin. Injection of the adenovirus encoding mCherry-LAMP1 into DRG showed that mCherry-positive lysosomes are transported to the central nerve terminal in DH. These findings suggest that activation of lysosome synthesis including ATP packaging in DRG, the central transportation of the lysosome, and subsequent its exocytosis from the central nerve terminal of DRG neurons in response to nerve injury could be a partial mechanism for activation of microglia in DH. This lysosome-mediated microglia activation mechanism may provide another clue to control nociception and pain. PMID:26601776

  9. Nature of 5-HT1-like receptors mediating depressor responses in vagosympathectomized rats; close resemblance to the cloned 5-ht7 receptor.

    PubMed

    De Vries, P; Villalón, C M; Heiligers, J P; Saxena, P R

    1997-07-01

    It has been suggested that the late hypotensive response to serotonin (5-hydroxytryptamine; 5-HT) in vagosympathectomized rats is mediated by '5-HT1-like' receptors since this effect is mimicked by 5-carboxamidotryptamine (5-CT), is not modified by cyproheptadine, ketanserin or MDL 72222, but it is blocked by methysergide. The present study was set out to reanalyze this suggestion in terms of the classification schemes proposed in 1994 and 1996 by the NC-IUPHAR subcommittee on the classification and nomenclature of 5-HT receptors. I.v. bolus injections of 5-CT (0.01-0.3 microg x kg(-1)), 5-HT (1-30 microg x kg(-1)) and 5-methoxytryptamine (5-MeO-T; 1-30 microg x kg(-1)) produced dose-dependent hypotensive responses with a rank order of agonist potency: 5-CT > 5-HT > 5-methoxytryptamine with sumatriptan (30-1000 microg x kg(-1)) inactive. The depressor responses to 5-HT and 5-CT were not attenuated by i.v. GR127935 (300-3000 microg x kg(-1)) or equivalent volumes of saline. In contrast, lisuride, methiothepin, mesulergine, metergoline and clozapine dose-dependently antagonized the responses to 5-HT and 5-CT; the rank order of apparent pA2 values against 5-HT and 5-CT, respectively, was: lisuride (7.7; 7.8) > methiothepin (6.8; 7.0) > or = mesulergine (6.4; 6.6) > clozapine (5.7; 5.8); metergoline displayed variable potencies (5.6; 6.4). Except for lisuride, which also affected isoprenaline-induced hypotension, the antagonism by the other drugs was selective. Based upon the above rank order of agonist potency, the blockade by a series of drugs showing high affinity for the cloned 5-ht7 receptor and the lack of blockade by GR127935, our results indicate that the 5-HT receptor mediating hypotension in vagosympathectomized rats is operationally similar to other putative 5-ht7 receptors mediating vascular and non-vascular responses (e.g. relaxation of the rabbit femoral vein, canine coronary and external carotid arteries and guinea-pig ileum as well as feline tachycardia

  10. The regulation of sGC on the rat model of neuropathic pain is mediated by 5-HT1ARs and NO/cGMP pathway

    PubMed Central

    Xu, Zifeng; Yang, Bin; Zhang, Jianhai; Zheng, Jijian

    2016-01-01

    Inadequate management of neuropathic pain results in poor clinical outcomes and reduces quality of life for the patient all over the world, but intricate interplay between wide variety of the pathophysiological mechanisms involved in the development and progression of neuropathic pain makes it difficult to design effective therapeutic strategies. The present study aims to elucidate the interaction of 5-HT1A receptors (5-HT1ARs), soluble guanylate cyclase (sGC) and NO/cGMP signaling pathway in the development of neuropathic pain. The results showed that after sciatic nerve crush procedure, the protein level of sGC in the spinal cord was greatly increased. The mechanical threshold in rats was significantly enhanced by the sGC inhibitor ODQ and neuronal NO synthase (nNOS) inhibitor SMTC, indicating the role of sGC and nNOS in the process of neuropathic pain. The treatment of NO donors (SNP and SIN-1) and cGMP-selective phosphodiesterase inhibitor (Zaprinast) all significantly decreased the mechanical threshold in rats, but the 5-HT1ARs inhibitor WAY100635 significantly increased the mechanical threshold in rats, demonstrating the role of NO/cGMP pathway and 5-HT1ARs in the development of neuropathic pain. Finally, the protein levels of sGC was greatly increased by SNP and Zaprinast but decreased by WAY100635 and SMTC, showing the regulation of NO/cGMP pathway and 5-HT1ARs on the protein expression of sGC. Taken together, it is suggested that sGC in the spinal cord regulates the neuropathic pain, which is mediated by 5-HT1ARs and NO/cGMP pathway. PMID:27158388

  11. An Orally Active Phenylaminotetralin-Chemotype Serotonin 5-HT7 and 5-HT1A Receptor Partial Agonist that Corrects Motor Stereotypy in Mouse Models.

    PubMed

    Canal, Clinton E; Felsing, Daniel E; Liu, Yue; Zhu, Wanying; Wood, JodiAnne T; Perry, Charles K; Vemula, Rajender; Booth, Raymond G

    2015-07-15

    Stereotypy (e.g., repetitive hand waving) is a key phenotype of autism spectrum disorder, Fragile X and Rett syndromes, and other neuropsychiatric disorders, and its severity correlates with cognitive and attention deficits. There are no effective treatments, however, for stereotypy. Perturbation of serotonin (5-HT) neurotransmission contributes to stereotypy, suggesting that distinct 5-HT receptors may be pharmacotherapeutic targets to treat stereotypy and related neuropsychiatric symptoms. For example, preclinical studies indicate that 5-HT7 receptor activation corrects deficits in mouse models of Fragile X and Rett syndromes, and clinical trials for autism are underway with buspirone, a 5-HT1A partial agonist with relevant affinity at 5-HT7 receptors. Herein, we report the synthesis, in vitro molecular pharmacology, behavioral pharmacology, and pharmacokinetic parameters in mice after subcutaneous and oral administration of (+)-5-(2'-fluorophenyl)-N,N-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine ((+)-5-FPT), a new, dual partial agonist targeting both 5-HT7 (Ki = 5.8 nM, EC50 = 34 nM) and 5-HT1A (Ki = 22 nM, EC50 = 40 nM) receptors. Three unique, heterogeneous mouse models were used to assess the efficacy of (+)-5-FPT to reduce stereotypy: idiopathic jumping in C58/J mice, repetitive body rotations in C57BL/6J mice treated with the NMDA antagonist, MK-801, and repetitive head twitching in C57BL/6J mice treated with the 5-HT2 agonist, DOI. Systemic (+)-5-FPT potently and efficaciously reduced or eliminated stereotypy in each of the mouse models without altering locomotor behavior on its own, and additional tests showed that (+)-5-FPT, at the highest behaviorally active dose tested, enhanced social interaction and did not cause behaviors indicative of serotonin syndrome. These data suggest that (+)-5-FPT is a promising medication for treating stereotypy in psychiatric disorders. PMID:26011730

  12. Highly potent, non-basic 5-HT6 ligands. Site mutagenesis evidence for a second binding mode at 5-HT6 for antagonism.

    PubMed

    Harris, Ralph N; Stabler, Russel S; Repke, David B; Kress, James M; Walker, Keith A; Martin, Renee S; Brothers, Julie M; Ilnicka, Mariola; Lee, Simon W; Mirzadegan, Tara

    2010-06-01

    A series of 5-HT(6) ligands derived from (R)-1-(amino)methyl-6-(phenyl)sulfonyltetralin was prepared that yielded several non-basic analogs having sub-nanomolar affinity. Ligand structure-activity relationships, receptor point mutation studies, and molecular modeling of these novel ligands all combined to reveal a new alternative binding mode to 5-HT(6) for antagonism. PMID:20434910

  13. Analysis of free ACh and 5-HT in milk from four different species and their bioactivity on 5-HT(3) and nACh receptors.

    PubMed

    Gallegos-Perez, Jose-Luis; Limon, Agenor; Reyes-Ruiz, Jorge M; Alshanqeeti, Ali S; Aljohi, Mohammad A; Miledi, Ricardo

    2014-07-25

    Milk is one of the most beneficial aliments and is highly recommended in normal conditions; however, in certain disorders, like irritable bowel syndrome, cow milk and dairy products worsen the gastric symptoms and their use is not recommended. Among the most recognized milk-induced gatrointestinal symptoms are abdominal pain, nausea and vomiting, which are processes controlled by cholinergic and serotonergic transmission. Whether the presence of bioavailable ACh and 5-HT in milk may contribute to normal peristalsis, or to the developing of these symptoms, is not known. In this work we attempt to determine whether the content of free ACh and 5-HT is of physiological significance in milk from four different species: cow (bovine), goat, camel and human. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to identify and quantify free ACh and 5-HT in milk, and activation of the serotonergic and cholinergic ionotropic receptors was investigated using electrophysiological experiments. Our principal hypothesis was that milk from these four species had sufficient free ACh and 5-HT to activate their correspondent receptors expressed in a heterologous system. Our results showed a more complex picture, in which free ACh and 5-HT and their ability to activate cholinergic and serotonergic receptors are not correlated. This work is a first step to elucidate whether 5-HT and ACh, at the concentrations present in the milk, can be associated to a direct function in the GI. PMID:24820623

  14. Human serotonin 1D receptor is encoded by a subfamily of two distinct genes: 5-HT1D alpha and 5-HT1D beta.

    PubMed Central

    Weinshank, R L; Zgombick, J M; Macchi, M J; Branchek, T A; Hartig, P R

    1992-01-01

    The serotonin 1D (5-HT1D) receptor is a pharmacologically defined binding site and functional receptor site. Observed variations in the properties of 5-HT1D receptors in different tissues have led to the speculation that multiple receptor proteins with slightly different properties may exist. We report here the cloning, deduced amino acid sequences, pharmacological properties, and second-messenger coupling of a pair of human 5-HT1D receptor genes, which we have designated 5-HT1D alpha and 5-HT1D beta due to their strong similarities in sequence, pharmacological properties, and second-messenger coupling. Both genes are free of introns in their coding regions, are expressed in the human cerebral cortex, and can couple to inhibition of adenylate cyclase activity. The pharmacological binding properties of these two human receptors are very similar, and match closely the pharmacological properties of human, bovine, and guinea pig 5-HT1D sites. Both receptors exhibit high-affinity binding of sumatriptan, a new anti-migraine medication, and thus are candidates for the pharmacological site of action of this drug. Images PMID:1565658

  15. Effects of the serotonin 5-HT(2) antagonist, ritanserin, and the serotonin 5-HT(1A) antagonist, WAY 100635, on cocaine-seeking in rats.

    PubMed

    Schenk, S

    2000-10-01

    Manipulations of serotonergic systems have been shown to modify many of the behavioral effects of cocaine. It was recently demonstrated that serotonin (5-HT) depletions produced by inhibition of tryptophan hydroxylase reduced cocaine-seeking in an animal model. The present study was designed to determine whether pretreatment with specific 5-HT antagonists might also decrease cocaine-seeking. The effect of pretreatment with the 5-HT(2) antagonist, ritanserin (0.0, 1.0, or 10.0 mg/kg), or the 5-HT(1A) antagonist, WAY 100635 (0. 0, 0.1, 0.3, or 1.0 mg/kg), on cocaine (5.0, 10.0, or 20.0 mg/kg)-produced reinstatement of extinguished drug-taking behavior was measured. Although ritanserin was ineffective, WAY 100635 attenuated cocaine-produced reinstatement in a dose-dependent manner. These effects of WAY 100635 appeared to be specific since responding maintained by saccharin self-administration remained high following pretreatment with 0.3 or 1.0 mg/kg WAY 100635. These data suggest a role of 5-HT(1A), but not 5-HT(2), receptors in cocaine-seeking. PMID:11124402

  16. 5-Chloroindole: a potent allosteric modulator of the 5-HT3 receptor

    PubMed Central

    Newman, Amy S; Batis, Nikolaos; Grafton, Gillian; Caputo, Francesca; Brady, Catherine A; Lambert, Jeremy J; Peters, John A; Gordon, John; Brain, Keith L; Powell, Andrew D; Barnes, Nicholas M

    2013-01-01

    Background and Purpose The 5-HT3 receptor is a ligand-gated ion channel that is modulated allosterically by various compounds including colchicine, alcohols and volatile anaesthetics. However the positive allosteric modulators (PAMs) identified to date have low affinity, which hinders investigation because of non-selective effects at pharmacologically active concentrations. The present study identifies 5-chloroindole (Cl-indole) as a potent PAM of the 5-HT3 receptor. Experimental Approach 5-HT3 receptor function was assessed by the increase in intracellular calcium and single-cell electrophysiological recordings in HEK293 cells stably expressing the h5-HT3A receptor and also the mouse native 5-HT3 receptor that increases neuronal contraction of bladder smooth muscle. Key Results Cl-indole (1–100 μM) potentiated agonist (5-HT) and particularly partial agonist [(S)-zacopride, DDP733, RR210, quipazine, dopamine, 2-methyl-5-HT, SR57227A, meta chlorophenyl biguanide] induced h5-HT3A receptor-mediated responses. This effect of Cl-indole was also apparent at the mouse native 5-HT3 receptor. Radioligand-binding studies identified that Cl-indole induced a small (∼twofold) increase in the apparent affinity of 5-HT for the h5-HT3A receptor, whereas there was no effect upon the affinity of the antagonist, tropisetron. Cl-indole was able to reactivate desensitized 5-HT3 receptors. In contrast to its effect on the 5-HT3 receptor, Cl-indole did not alter human nicotinic α7 receptor responses. Conclusions and Implications The present study identifies Cl-indole as a relatively potent and selective PAM of the 5-HT3 receptor; such compounds will aid investigation of the molecular basis for allosteric modulation of the 5-HT3 receptor and may assist the discovery of novel therapeutic drugs targeting this receptor. Linked Articles Recent reviews on allosteric modulation can be found at: Kenakin, T (2013). New concepts in pharmacological efficacy at 7TM receptors: IUPHAR Review 2

  17. Cervical spinal cord injury upregulates ventral spinal 5-HT2A receptors.

    PubMed

    Fuller, David D; Baker-Herman, Tracy L; Golder, Francis J; Doperalski, Nicholas J; Watters, Jyoti J; Mitchell, Gordon S

    2005-02-01

    Following chronic C2 spinal hemisection (C2HS), crossed spinal pathways to phrenic motoneurons exhibit a slow, spontaneous increase in efficacy by a serotonin (5-HT)-dependent mechanism associated with 5-HT2A receptor activation. Further, the spontaneous appearance of cross-phrenic activity following C2HS is accelerated and enhanced by exposure to chronic intermittent hypoxia (CIH). We hypothesized that chronic C2HS would increase 5-HT and 5-HT2A receptor expression in ventral cervical spinal segments containing phrenic motoneurons. In addition, we hypothesized that CIH exposure would further increase 5-HT and 5-HT2A receptor density in this region. Control, sham-operated, and C2HS Sprague-Dawley rats were studied following normoxia or CIH (11% O2-air; 5-min intervals; nights 7-14 post-surgery). At 2 weeks post-surgery, ventral spinal gray matter extending from C4 and C5 was isolated ipsilateral and contralateral to C2HS. Neither C2HS nor CIH altered 5-HT concentration measured with an ELISA on either side of the spinal cord. However, 5-HT2A receptor expression assessed with immunoblots increased in ipsilateral gray matter following C2HS, an effect independent of CIH. Immunocytochemistry revealed increased 5-HT2A receptor expression on identified phrenic motoneurons (p<0.05), as well as in the surrounding gray matter. Contralateral to injury, 5-HT2A receptor expression was elevated in CIH, but not normoxic C2HS rats (p<0.05). Our data are consistent with the hypothesis that spontaneous increase in 5-HT2A receptor expression on or near phrenic motoneurons contributes to strengthened crossed-spinal synaptic pathways to phrenic motoneurons following C2HS. PMID:15716627

  18. Pharmacological Characterization of a 5-HT1-Type Serotonin Receptor in the Red Flour Beetle, Tribolium castaneum

    PubMed Central

    Vleugels, Rut; Lenaerts, Cynthia; Baumann, Arnd; Vanden Broeck, Jozef; Verlinden, Heleen

    2013-01-01

    Serotonin (5-hydroxytryptamine, 5-HT) is known for its key role in modulating diverse physiological processes and behaviors by binding various 5-HT receptors. However, a lack of pharmacological knowledge impedes studies on invertebrate 5-HT receptors. Moreover, pharmacological information is urgently needed in order to establish a reliable classification system for invertebrate 5-HT receptors. In this study we report on the molecular cloning and pharmacological characterization of a 5-HT1 receptor from the red flour beetle, Tribolium castaneum (Trica5-HT1). The Trica5-HT1 receptor encoding cDNA shows considerable sequence similarity with members of the 5-HT1 receptor class. Real time PCR showed high expression in the brain (without optic lobes) and the optic lobes, consistent with the role of 5-HT as neurotransmitter. Activation of Trica5-HT1 in mammalian cells decreased NKH-477-stimulated cyclic AMP levels in a dose-dependent manner, but did not influence intracellular Ca2+ signaling. We studied the pharmacological profile of the 5-HT1 receptor and demonstrated that α-methylserotonin, 5-methoxytryptamine and 5-carboxamidotryptamine acted as agonists. Prazosin, methiothepin and methysergide were the most potent antagonists and showed competitive inhibition in presence of 5-HT. This study offers important information on a 5-HT1 receptor from T. castaneum facilitating functional research of 5-HT receptors in insects and other invertebrates. The pharmacological profiles may contribute to establish a reliable classification scheme for invertebrate 5-HT receptors. PMID:23741451

  19. 5-Hydroxytryptamine-induced bladder hyperactivity via the 5-HT2A receptor in partial bladder outlet obstruction in rats.

    PubMed

    Sakai, Takumi; Kasahara, Ken-ichi; Tomita, Ken-ichi; Ikegaki, Ichiro; Kuriyama, Hiroshi

    2013-04-01

    We investigated the effects of partial bladder outlet obstruction (BOO) on the function and gene expression of 5-hydroxytryptamine (5-HT) receptor subtypes in rat bladder. Isometric contractions of the isolated bladders from sham-operated control and BOO rats were examined. The contractile responses to 5-HT were significantly increased in BOO rat bladder strips, while the responses to KCl, carbachol, or phenylephrine were not different from the control. The 5-HT-induced hypercontraction in BOO rat bladder strips was inhibited by ketanserin, a 5-HT(2A) receptor antagonist. The contractile responses to 5-HT in bladder strips were not affected by urothelium removal from the intact bladder. The gene expression of 5-HT receptor subtypes in the bladders was analyzed by RT-PCR. The mRNA expression of the 5-HT(2A), 5-HT(2B), 5-HT(2C), 5-HT(4), and 5-HT(7) receptors was detected in both the control and BOO rat bladders. Quantitative RT-PCR analysis showed there was a significant increase of 5-HT(2A) receptor mRNA in the BOO rat bladder compared with the control bladder. On the other hand, the gene expression of the 5-HT(4) receptor was not changed in the BOO rat bladder. These results suggest that the increased contractile responses to 5-HT in BOO rat bladder may be partly caused by 5-HT(2A) receptor upregulation in the detrusor smooth muscles. PMID:23344575

  20. Neuronal porosome - The secretory portal at the nerve terminal: Its structure-function, composition, and reconstitution

    NASA Astrophysics Data System (ADS)

    Jena, Bhanu P.

    2014-09-01

    Cup-shaped secretory portals at the cell plasma membrane called porosomes mediate secretion from cells. Membrane bound secretory vesicles transiently dock and fuse at the cytosolic compartment of the porosome base to expel intravesicular contents to the outside during cell secretion. In the past decade, the structure, isolation, composition, and functional reconstitution of the neuronal porosome complex has been accomplished providing a molecular understanding of its structure-function. Neuronal porosomes are 15 nm cup-shaped lipoprotein structures composed of nearly 40 proteins; compared to the 120 nm nuclear pore complex comprised of over 500 protein molecules composed of 30 different proteins. Being a membrane-associated supramolecular complex has precluded determination of the atomic structure of the porosome. However recent studies using small-angle X-ray solution scattering (SAXS), provide at sub-nanometer resolution, the native 3D structure of the neuronal porosome complex associated with docked synaptic vesicle at the nerve terminal. Additionally, results from the SAXS study and earlier studies using atomic force microscopy, provide the possible molecular mechanism involved in porosome-mediated neurotransmitter release at the nerve terminal.

  1. Circadian variation in the activity of the 5-HT1B autoreceptor in the region of the suprachiasmatic nucleus, measured by microdialysis in the conscious freely-moving rat

    PubMed Central

    Garabette, M L; Martin, K F; Redfern, P H

    2000-01-01

    Intracerebral microdialysis was used to examine the function of the terminal 5-hydroxytryptamine1B (5-HT1B) autoreceptor in the region of the suprachiasmatic nuclei (SCN) of freely moving conscious rats at six time points or zeitgeber times (ZTs) across the light:dark cycle. Infusion of the 5-HT1A/1B agonist 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridyl)-1H-indole (RU24969) (1 μM) via the microdialysis probe produced a decrease in 5-HT output when applied at ZTs 3, 6, 15 and 21 (69.8±11.9, 59±11.7, 43.9±17.2 and 45.7±17.0% respectively). At ZTs 9 and 18 RU24969 (1 μm) failed to affect the 5-HT output significantly (28.0±11 and 32.8±24.6% decrease respectively). The profile of inhibition of 5-HT output following infusion of RU24969 (1 μM) at ZT 6 was unaffected by concurrent infusion of the specific 5-HT1A antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide trihydrochloride (WAY100635) (1 μM) (52.48±17.5% decrease). The data demonstrate a circadian rhythm in the activity of the 5-HT1B autoreceptor in the region of the SCN. PMID:11139433

  2. Binding of indolylalkylamines at 5-HT2 serotonin receptors: examination of a hydrophobic binding region.

    PubMed

    Glennon, R A; Chaurasia, C; Titeler, M

    1990-10-01

    Taking advantage of a proposed hydrophobic region on 5-HT2 receptors previously identified by radioligand-binding studies utilizing various phenylisopropylamine derivatives, we prepared and evaluated several N1 - and/or C7-alkyl-substituted derivatives of alpha-methyltryptamine in order to improve its affinity and selectivity. It was determined that substitution of an n-propyl or amyl group has similar effect on affinity regardless of location (i.e., N1 or C7). The low affinity of several N1-alkylpyrroleethylamines suggests that the benzene portion of the alpha-methyltryptamines is necessary for significant affinity. Whereas tryptamine derivatives generally display little selectivity for the various populations of 5-HT receptors, N1-n-propyl-5-methoxy-alpha-methyltryptamine (3h) binds with significant affinity (Ki = 12 nM) and selectivity at 5-HT2 receptors relative to 5-HT1A (Ki = 7100 nM), 5-HT1B (Ki = 5000 nM), 5-HT1C (Ki = 120 nM), and 5-HT1D (Ki greater than 10,000 nM) receptors. As a consequence, this is the most 5-HT2-selective indolylalkylamine derivative reported to date. PMID:2213830

  3. The 5-HT7 receptor triggers cerebellar long-term synaptic depression via PKC-MAPK.

    PubMed

    Lippiello, Pellegrino; Hoxha, Eriola; Speranza, Luisa; Volpicelli, Floriana; Ferraro, Angela; Leopoldo, Marcello; Lacivita, Enza; Perrone-Capano, Carla; Tempia, Filippo; Miniaci, Maria Concetta

    2016-02-01

    The 5-HT7 receptor (5-HT7R) mediates important physiological effects of serotonin, such as memory and emotion, and is emerging as a therapeutic target for the treatment of cognitive disorders and depression. Although previous studies have revealed an expression of 5-HT7R in cerebellum, particularly at Purkinje cells, its functional role and signaling mechanisms have never been described. Using patch-clamp recordings in cerebellar slices of adult mice, we investigated the effects of a selective 5-HT7R agonist, LP-211, on the main plastic site of the cerebellar cortex, the parallel fiber-Purkinje cell synapse. Here we show that 5-HT7R activation induces long-term depression of parallel fiber-Purkinje cell synapse via a postsynaptic mechanism that involves the PKC-MAPK signaling pathway. Moreover, a 5-HT7R antagonist abolished the expression of PF-LTD, produced by pairing parallel fiber stimulation with Purkinje cell depolarization; whereas, application of a 5-HT7R agonist impaired LTP induced by 1 Hz parallel fiber stimulation. Our results indicate for the first time that 5-HT7R exerts a fine regulation of cerebellar bidirectional synaptic plasticity that might be involved in cognitive processes and neuropsychiatric disorders involving the cerebellum. PMID:26482421

  4. Varenicline Interactions at the 5-HT3 Receptor Ligand Binding Site are Revealed by 5-HTBP

    PubMed Central

    2015-01-01

    Cys-loop receptors are the site of action of many therapeutic drugs. One of these is the smoking cessation agent varenicline, which has its major therapeutic effects at nicotinic acetylcholine (nACh) receptors but also acts at 5-HT3 receptors. Here, we report the X-ray crystal structure of the 5-HT binding protein (5-HTBP) in complex with varenicline, and test the predicted interactions by probing the potency of varenicline in a range of mutant 5-HT3 receptors expressed in HEK293 cells and Xenopus oocytes. The structure reveals a range of interactions between varenicline and 5-HTBP. We identified residues within 5 Å of varenicline and substituted the equivalent residues in the 5-HT3 receptor with Ala or a residue with similar chemical properties. Functional characterization of these mutant 5-HT3 receptors, using a fluorescent membrane potential dye in HEK cells and voltage clamp in oocytes, supports interactions between varenicline and the receptor that are similar to those in 5-HTBP. The structure also revealed C-loop closure that was less than in the 5-HT-bound 5-HTBP, and hydrogen bonding between varenicline and the complementary face of the binding pocket via a water molecule, which are characteristics consistent with partial agonist behavior of varenicline in the 5-HT3 receptor. Together, these data reveal detailed insights into the molecular interaction of varenicline in the 5-HT3 receptor. PMID:25648658

  5. Serotonin 5-HT2 Receptor Interactions with Dopamine Function: Implications for Therapeutics in Cocaine Use Disorder

    PubMed Central

    Cunningham, Kathryn A.

    2015-01-01

    Cocaine exhibits prominent abuse liability, and chronic abuse can result in cocaine use disorder with significant morbidity. Major advances have been made in delineating neurobiological mechanisms of cocaine abuse; however, effective medications to treat cocaine use disorder remain to be discovered. The present review will focus on the role of serotonin (5-HT; 5-hydroxytryptamine) neurotransmission in the neuropharmacology of cocaine and related abused stimulants. Extensive research suggests that the primary contribution of 5-HT to cocaine addiction is a consequence of interactions with dopamine (DA) neurotransmission. The literature on the neurobiological and behavioral effects of cocaine is well developed, so the focus of the review will be on cocaine with inferences made about other monoamine uptake inhibitors and releasers based on mechanistic considerations. 5-HT receptors are widely expressed throughout the brain, and several different 5-HT receptor subtypes have been implicated in mediating the effects of endogenous 5-HT on DA. However, the 5-HT2A and 5-HT2C receptors in particular have been implicated as likely candidates for mediating the influence of 5-HT in cocaine abuse as well as to traits (e.g., impulsivity) that contribute to the development of cocaine use disorder and relapse in humans. Lastly, new approaches are proposed to guide targeted development of serotonergic ligands for the treatment of cocaine use disorder. PMID:25505168

  6. Compulsive behavior in the 5-HT2C receptor knockout mouse.

    PubMed

    Chou-Green, Jennifer M; Holscher, Todd D; Dallman, Mary F; Akana, Susan F

    2003-04-01

    The efficacy of serotonergic pharmacotherapy indicates that serotonin (5-HT) plays a role in the treatment, if not the etiology, of obsessive-compulsive disorder (OCD). While some clinical evidence implicates 5-HT(2C) receptors in this disorder, a definitive function has yet to be validated. We hypothesized that 5-HT(2C) receptor knockout (KO) mice may display compulsive-like behavior. This paper describes characterization of several distinct, highly organized behaviors in mice lacking functional 5-HT(2C) receptors, which supports a compulsive-like syndrome.Compulsive-like behavior was assessed in male 5-HT(2C) receptor KO and wildtype (WT) mice. Chewing of non-nutritive clay, chewing patterns on plastic-mesh screens, and the frequency of head dipping were measured. 5-HT(2C) receptor KO mice chewed more clay, produced a distinct pattern of "neat" chewing of plastic screens and exhibited reduced habituation of head dipping activity compared to WT mice. We conclude that the 5-HT(2C) receptor null mutant mouse provides a promising model of compulsive behavior and a means to further explore the role of 5-HT in OCD. PMID:12782219

  7. Possible differences in modes of agonist and antagonist binding at human 5-HT6 receptors.

    PubMed

    Pullagurla, Manik R; Westkaemper, Richard B; Glennon, Richard A

    2004-09-01

    A graphics model of the human 5-HT6 receptor was constructed and automated docking studies were performed. The model suggests that 5-HT6 antagonist arylsulfonyltryptamines might bind differently than that of the agonist serotonin. Furthermore, the model explains many of the empirical results from our previous structure-affinity studies. PMID:15357994

  8. Modulation of the vagal bradycardia evoked by stimulation of upper airway receptors by central 5-HT1 receptors in anaesthetized rabbits

    PubMed Central

    Dando, Simon B; Skinner, Matthew R; Jordan, David; Ramage, Andrew G

    1998-01-01

    The effects of central application of 5-HT1A and 5-HT1B/1D receptor ligands on the reflex bradycardia, apnoea, renal sympathoexcitation and pressor response evoked by stimulating upper airway receptors with smoke in atenolol-pretreated anaesthetized rabbits were studied.Intracisternal administration of the 5-HT1A receptor antagonists WAY-100635 (100 μg kg−1) and (−)pindolol (100 μg kg−1) significantly reduced the smoke-induced bradycardia, attenuated the pressor response and in the case of (−)pindolol, sympathetic nerve activity. The same dose of WAY-100635 i.v. was without effect.Buspirone (200 μg kg−1, i.c.) potentiated the reflex bradycardia. This action was prevented if the animals were pretreated with WAY-100635 (100 μg kg−1, i.v.)(+)8-OH-DPAT (25 μg kg−1, i.c.) attenuated the evoked bradycardia, pressor response, apnoea and renal sympathoexcitation. The attenuation of the apnoea and renal sympathoexcitation, but not the bradycardia or pressor response was prevented in animals pretreated with WAY-100635 (100 μg kg−1, i.v.). The attenuation of the reflex bradycardia and the reduction in the renal sympathoexcitation were reduced by pretreatment with the 5-HT1B/1D receptor antagonist GR127935 (100 μg kg−1, i.v.).In WAY-100635 (100 μg kg−1, i.v.) pretreated animals, sumatriptan (a 5-HT1B/1D receptor agonist) reduced the reflex bradycardia and the pressor response. The 5-HT1B/1D receptor antagonist GR127935 (20 μg kg−1, i.c. or 100 μg kg−1, i.v.) had no effect on the reflex responses.In conclusion, the present data are consistent with the hypothesis that activation of central 5-HT1A receptors potentiate whilst activation of 5-HT1B/1D receptors attenuate the reflex activation of cardiac preganglionic vagal motoneurones evoked by stimulation of upper airway receptors with smoke in rabbits. PMID:9786516

  9. Contributions of 5-HT Neurons to Respiratory Control: Neuromodulatory and Trophic Effects

    PubMed Central

    Hodges, Matthew R.; Richerson, George B.

    2008-01-01

    Serotonin (5-hydroxytryptamine; 5-HT) is a neurotransmitter produced by a small number of neurons in the midbrain, pons and medulla. These neurons project widely throughout the neuraxis, where they release 5-HT and co-localized neuropeptides such as substance P (SP) and thyrotropin-releasing hormone (TRH). Each of these chemicals produce effects largely through G protein-coupled receptors, second messenger systems and subsequent neuromodulatory effects on target neurons. Emerging evidence suggests that 5-HT has additional modes of action during development and in adult mammals, including trophic effects (neurogenesis, cell differentiation, proliferation, migration and maturation) and influences on synaptic plasticity. Here, we discuss some of the neuromodulatory and trophic roles of 5-HT in general and in the context of respiratory control, as well as the regulation of release of modulatory neurotransmitters from 5-HT neurons. Future directions of study are also discussed. PMID:18595785

  10. Characterization of putative 5-HT7 receptors mediating tachycardia in the cat

    PubMed Central

    Villalón, Carlos M; Heiligers, Jan P C; Centurión, David; De Vries, Peter; Saxena, Pramod R

    1997-01-01

    It has been suggested that the tachycardic response to 5-hydroxytryptamine (5-HT) in the spinal-transected cat is mediated by ‘5-HT1-like' receptors since this effect, being mimicked by 5-carboxamidotryptamine (5-CT), is not modified by ketanserin or MDL 72222, but it is blocked by methiothepin, methysergide or mesulergine. The present study was set out to reanalyse this suggestion in terms of the IUPHAR 5-HT receptor classification schemes proposed in 1994 and 1996. Intravenous (i.v.) bolus injections of the tryptamine derivatives, 5-CT (0.01, 0.03, 0.1, 0.3, 1, 3, 10 and 30 μg kg−1), 5-HT (3, 10 and 30 μg kg−1) and 5-methoxytryptamine (3, 10 and 30 μg kg−1) as well as the atypical antipsychotic drug, clozapine (1000 and 3000 μg kg−1) resulted in dose-dependent increases in heart rate, with a rank order of agonist potency of 5-CT >> 5-HT > 5-methoxytryptamine >> clozapine. The tachycardic effects of 5-HT and 5-methoxytryptamine were dose-dependently antagonized by i.v. administration of lisuride (30 and 100 μg kg−1), ergotamine (100 and 300 μg kg−1) or mesulergine (100, 300 and 1000 μg kg−1); the highest doses of these antagonists used also blocked the tachycardic effects of 5-CT. Clozapine (1000 and 3000 μg kg−1) did not affect the 5-HT-induced tachycardia, but attenuated, with its highest dose, the responses to 5-methoxytryptamine and 5-CT. However, these doses of clozapine as well as the high doses of ergotamine (300 μg kg−1) and mesulergine (300 and 1000 μg kg−1) also attenuated the tachycardic effects of isoprenaline. In contrast, 5-HT-, 5-methoxytryptamine- and 5-CT-induced tachycardia were not significantly modified after i.v. administration of physiological saline (0.1 and 0.3 ml kg−1), the 5-HT1B/1D receptor antagonist, GR127935 (500 μg kg−1) or the 5-HT3/4 receptor antagonist, tropisetron (3000 μg kg−1). Intravenous injections of the 5-HT1 receptor agonists

  11. Design, Synthesis, and Structure–Activity Relationships of Highly Potent 5-HT3 Receptor Ligands

    PubMed Central

    2012-01-01

    The 5-HT3 receptor, a pentameric ligand-gated ion channel (pLGIC), is an important therapeutic target. During a recent fragment screen, 6-chloro-N-methyl-2-(4-methyl-1,4-diazepan-1-yl)quinazolin-4-amine (1) was identified as a 5-HT3R hit fragment. Here we describe the synthesis and structure–activity relationships (SAR) of a series of (iso)quinoline and quinazoline compounds that were synthesized and screened for 5-HT3R affinity using a [3H]granisetron displacement assay. These studies resulted in the discovery of several high affinity ligands of which compound 22 showed the highest affinity (pKi > 10) for the 5-HT3 receptor. The observed SAR is in agreement with established pharmacophore models for 5-HT3 ligands and is used for ligand–receptor binding mode prediction using homology modeling and in silico docking approaches. PMID:23006041

  12. Effects of age of serotonin 5-HT2 receptors in cocaine abusers and normal subjects

    SciTech Connect

    Wang, G.J.; Volkow, N.D.; Logan, J.

    1995-05-01

    We measured the effect of age on serotonin 5-HT2 receptor availability and compared it with the effects on dopamine D2 receptors on 19 chronic cocaine abusers (35.2{plus_minus}9.8 years, range 18-54 years old) and 19 age matched normal controls using positron emission tomography (PET) and F-18 N-methylspiperone (NMS). 5-HT2 Receptor availability was measure din frontal (FR), occipital (OC), cingulate (CI) and orbitofrontal (OF) cortices using the ratio of the distribution volume in the region of interest to that in the cerebelium (CB) which is a function of Bmax/Kd. D2 receptor availability in the basal ganglia was measured using the {open_quotes}ratio index{close_quotes} (slope of striatum/CB versus time over 180 min of the scan) which is a function of Bmax. 5-HT2 Receptor availability differed among regions and were as follows: CI>OF>OC>FC.5-HT2 Receptor availability decreased significantly with age. This effect was more accentuated for 5-HT2 receptor availability in FR than in OC(df=1, p<0.025). Striatal dopamine D2 receptors were also found to decrease significantly with age (r=0.63, p<0.007). In a given subject, D2 receptor availability was significantly correlated with 5-HT2 receptor availability in FR (r=0.51, p<0.035) but not in OC. The values for 5-HT2 receptor availability were not different in normal subjects and cocaine abusers. These results document a decline in 5-HT2 and D2 receptors with age and document an association between frontal 5-HT2 and striatal D2 receptor availability. These results did not show any changes in 5-HT2 receptor availability in cocaine abusers as compared to control subjects.

  13. Fusion Pore Size Limits 5-HT Release From Single Enterochromaffin Cell Vesicles.

    PubMed

    Raghupathi, Ravinarayan; Jessup, Claire F; Lumsden, Amanda L; Keating, Damien J

    2016-07-01

    Enterochromaffin cells are the major site of serotonin (5-HT) synthesis and secretion providing ∼95% of the body's total 5-HT. 5-HT can act as a neurotransmitter or hormone and has several important endocrine and paracrine roles. We have previously demonstrated that EC cells release small amounts of 5-HT per exocytosis event compared to other endocrine cells. We utilized a recently developed method to purify EC cells to demonstrate the mechanisms underlying 5-HT packaging and release. Using the fluorescent probe FFN511, we demonstrate that EC cells express VMAT and that VMAT plays a functional role in 5-HT loading into vesicles. Carbon fiber amperometry studies illustrate that the amount of 5-HT released per exocytosis event from EC cells is dependent on both VMAT and the H(+)-ATPase pump, as demonstrated with reserpine or bafilomycin, respectively. We also demonstrate that increasing the amount of 5-HT loaded into EC cell vesicles does not result in an increase in quantal release. As this indicates that fusion pore size may be a limiting factor involved, we compared pore diameter in EC and chromaffin cells by assessing the vesicle capture of different-sized fluorescent probes to measure the extent of fusion pore dilation. This identified that EC cells have a reduced fusion pore expansion that does not exceed 9 nm in diameter. These results demonstrate that the small amounts of 5-HT released per fusion event in EC cells can be explained by a smaller fusion pore that limits 5-HT release capacity from individual vesicles. PMID:26574734

  14. Characterization, solubilization and partial purification of serotonin 5-HT1C receptors

    SciTech Connect

    Yagaloff, K.A.

    1986-01-01

    /sup 125/I-Lysergic acid diethylamide (/sup 125/I-LSD) binds with high affinity to a unique serotonergic site on rat choroid plexus. These sites were localized to choroid plexus epithelial cells using a novel high resolution autoradiographic technique. In membrane preparations, the serotonergic site density was 3100 fmol/mg protein, which is 10 fold higher than the density of any other serotonergic site in brain homogenates. The pharmacology of this site, termed the 5-HT1c site, does not match that of 5-Ht1a, 5-HT1b or 5HT2 serotonergic sites. 5-Ht1c sites were solubilized from pig choroid plexus using the zwitterionic detergent, CHAPS. High affinity labelling of the solubilized site was obtained using the serotonergic radioligand, N1-methyl-2-(/sup 125/I)lysergic acid diethylamide (/sup 125/I-MIL). Choroid plexus tumors obtained from transgenic mice were examined for the presence of serotonin 5-HT1c receptors. /sup 125/I-LSD binding to choroid plexus tumors displays a pharmacological profile that matches the properties of 5-HT1c receptors in normal choroid plexus. The tumor exhibits the highest site density of serotonin receptors (6600 fmol/mg protein) found in any tissue. /sup 125/I-LSD autoradiography of brain sections from transgenic mice shows high levels of specific labelling over the tumor. The affinities of various indolealkyl, phenlakyl and beta-carboline derivatives for the serotonin 5-HT1c receptor were measured in pig choroid plexus using /sup 125/I-MIL. Serotonin precursors and metabolites were all very weak inhibitors of specific /sup 125/I-MIL binding. Structure-affinity relationships were determined for a number of indolealkylamine analogues. Only serotonin is present in cerebrospinal fluid at concentrations near its 5-HT1c inhibition constant, suggesting that serotonin is the natural 5-HT1c agonist.

  15. Effect of Peripheral 5-HT on Glucose and Lipid Metabolism in Wether Sheep

    PubMed Central

    Watanabe, Hitoshi; Saito, Ryo; Nakano, Tatsuya; Takahashi, Hideyuki; Takahashi, Yu; Sumiyoshi, Keisuke; Sato, Katsuyoshi; Chen, Xiangning; Okada, Natsumi; Iwasaki, Shunsuke; Harjanti, Dian W.; Sekiguchi, Natsumi; Sano, Hiroaki; Kitazawa, Haruki; Rose, Michael T.; Ohwada, Shyuichi; Watanabe, Kouichi; Aso, Hisashi

    2014-01-01

    In mice, peripheral 5-HT induces an increase in the plasma concentrations of glucose, insulin and bile acids, and a decrease in plasma triglyceride, NEFA and cholesterol concentrations. However, given the unique characteristics of the metabolism of ruminants relative to monogastric animals, the physiological role of peripheral 5-HT on glucose and lipid metabolism in sheep remains to be established. Therefore, in this study, we investigated the effect of 5-HT on the circulating concentrations of metabolites and insulin using five 5-HT receptor (5HTR) antagonists in sheep. After fasting for 24 h, sheep were intravenously injected with 5-HT, following which-, plasma glucose, insulin, triglyceride and NEFA concentrations were significantly elevated. In contrast, 5-HT did not affect the plasma cholesterol concentration, and it induced a decrease in bile acid concentrations. Increases in plasma glucose and insulin concentrations induced by 5-HT were attenuated by pre-treatment with Methysergide, a 5HTR 1, 2 and 7 antagonist. Additionally, decreased plasma bile acid concentrations induced by 5-HT were blocked by pre-treatment with Ketanserin, a 5HTR 2A antagonist. However, none of the 5HTR antagonists inhibited the increase in plasma triglyceride and NEFA levels induced by 5-HT. On the other hand, mRNA expressions of 5HTR1D and 1E were observed in the liver, pancreas and skeletal muscle. These results suggest that there are a number of differences in the physiological functions of peripheral 5-HT with respect to lipid metabolism between mice and sheep, though its effect on glucose metabolism appears to be similar between these species. PMID:24505376

  16. Spinal 5-HT7 receptors induce phrenic motor facilitation via EPAC-mTORC1 signaling.

    PubMed

    Fields, D P; Springborn, S R; Mitchell, G S

    2015-09-01

    Spinal serotonin type 7 (5-HT7) receptors elicit complex effects on motor activity. Whereas 5-HT7 receptor activation gives rise to long-lasting phrenic motor facilitation (pMF), it also constrains 5-HT2 receptor-induced pMF via "cross-talk inhibition." We hypothesized that divergent cAMP-dependent signaling pathways give rise to these distinct 5-HT7 receptor actions. Specifically, we hypothesized that protein kinase A (PKA) mediates cross-talk inhibition of 5-HT2 receptor-induced pMF whereas 5-HT7 receptor-induced pMF results from exchange protein activated by cAMP (EPAC) signaling. Anesthetized, paralyzed, and ventilated rats receiving intrathecal (C4) 5-HT7 receptor agonist (AS-19) injections expressed pMF for >90 min, an effect abolished by pretreatment with a selective EPAC inhibitor (ESI-05) but not a selective PKA inhibitor (KT-5720). Furthermore, intrathecal injections of a selective EPAC activator (8-pCPT-2'-Me-cAMP) were sufficient to elicit pMF. Finally, spinal mammalian target of rapamycin complex-1 (mTORC1) inhibition via intrathecal rapamycin abolished 5-HT7 receptor- and EPAC-induced pMF, demonstrating that spinal 5-HT7 receptors elicit pMF by an EPAC-mTORC1 signaling pathway. Thus 5-HT7 receptors elicit and constrain spinal phrenic motor plasticity via distinct signaling mechanisms that diverge at cAMP (EPAC vs. PKA). Selective manipulation of these molecules may enable refined regulation of serotonin-dependent spinal motor plasticity for therapeutic advantage. PMID:26269554

  17. On the blockade of acetylcholine release at mouse motor nerve terminals by beta-bungarotoxin and crotoxin.

    PubMed Central

    Rowan, E. G.; Pemberton, K. E.; Harvey, A. L.

    1990-01-01

    1. beta-Bungarotoxin and crotoxin are phospholipose A2 neurotoxins, which block irreversibly the evoked release of acetylcholine from motor nerve terminals of mouse triangularis sterni preparations. 2. Extracellular recording of nerve terminal action potentials reveal that inhibition of transmitter release is not associated with failure of the action potential to invade nerve terminals. 3. When evoked transmitter release (measured as intracellularly recorded endplate potentials) was blocked by beta-bungarotoxin, spontaneous acetylcholine release was stimulated as in control experiments by K(+)-induced depolarization and by the Ca2(+)-ionophore A23187. 4. The site of action of the toxins remains to be elucidated but would appear to be associated with the coupling of action potential induced-depolarization to the release mechanism, rather than with the release mechanism itself. PMID:2116202

  18. Mediation of 5-HT-induced external carotid vasodilatation in GR 127935-pretreated vagosympathectomized dogs by the putative 5-HT7 receptor

    PubMed Central

    Villalón, Carlos M; Centurión, David; Luján-Estrada, Miguel; Terrón, José A; Sánchez-López, Araceli

    1997-01-01

    The vasodilator effects of 5-hydroxytryptamine (5-HT) in the external carotid bed of anaesthetized dogs with intact sympathetic tone are mediated by prejunctional sympatho-inhibitory 5-HT1B/1D receptors and postjunctional 5-HT receptors. The prejunctional vasodilator mechanism is abolished after vagosympathectomy which results in the reversal of the vasodilator effect to vasoconstriction. The blockade of this vasoconstrictor effect of 5-HT with the 5-HT1B/1D receptor antagonist, GR 127935, unmasks a dose-dependent vasodilator effect of 5-HT, but not of sumatriptan. Therefore, the present study set out to analyse the pharmacological profile of this postjunctional vasodilator 5-HT receptor in the external carotid bed of vagosympathectomized dogs pretreated with GR 127935 (20 μg kg−1, i.v.).One-minute intracarotid (i.c.) infusions of 5-HT (0.330 μg min−1), 5-carboxamidotryptamine (5-CT; 0.010.3 μg min−1), 5-methoxytryptamine (1100 μg min−1) and lisuride (31000 μg min−1) resulted in dose-dependent increases in external carotid blood flow (without changes in blood pressure or heart rate) with a rank order of agonist potency of 5-CT>>5-HT⩾5-methoxytryptamine>lisuride, whereas cisapride (1001000 μg min−1, i.c.) was practically inactive. Interestingly, lisuride (mean dose of 85±7 μg kg−1, i.c.), but not cisapride (mean dose of 67±7 μg kg−1, i.c.), specifically abolished the responses induced by 5-HT, 5-CT and 5-methoxytryptamine, suggesting that a common site of action may be involved. In contrast, 1 min i.c. infusions of 8-OH-DPAT (33000 μg min−1) produced dose-dependent decreases, not increases, in external carotid blood flow and failed to antagonize (mean dose of 200±33 μg kg−1, i.c.) the agonist-induced vasodilator responses.The external carotid vasodilator responses to 5-HT, 5-CT and 5-methoxytryptamine were not modified by intravenous (i.v.) pretreatment with either saline, (±)-pindolol (4

  19. Effects of physical training on functional activity of 5-HT1B receptors in rat central nervous system: role of 5-HT-moduline.

    PubMed

    Chennaoui, M; Grimaldi, B; Fillion, M P; Bonnin, A; Drogou, C; Fillion, G; Guezennec, C Y

    2000-06-01

    The effect of physical exercise was examined on the sensitivity of 5-HT1B receptors and on 5-HT-moduline tissue concentration in the central nervous system of rats. Rats were trained for 7 consecutive weeks to run on a treadmill. Three groups of animals were selected: group 1, sedentary rats (controls); group 2, animals running for 1 h at 18 m/min for 5 days per week (moderate training) and group 3, animals running for 2 h, at 30 m/min on a 7% grade for 5 days per week (intensive training). The animals were sacrificed 24 h after the last running. Rat brains were dissected out to obtain hippocampus and substantia nigra and kept at -80 degrees C until use. 5-HT1B receptor activity was determined by studying [35S]GTPgammaS binding in a substantia nigra membrane preparation from individual animals, after stimulation by a selective 5-HT1B receptor agonist (CP 93,129). 5-HT-moduline tissue content in hippocampus from individual animals was determined by ELISA using a polyclonal anti-5-HT-moduline antibody. In moderately trained animals (n=5), the CP 93,129-stimulated [35S]GTPgammaS binding curve was shifted to the right compared with controls (n=6), whereas the binding was totally suppressed in intensely trained animals (n=5). In parallel, 5-HT-moduline tissue concentration in the hippocampus was slightly increased in moderately trained animals (117.3 +/- 8.9%) (n=5), whereas it was significantly increased in intensely trained animals (182.6 +/- 29.5%) (n=5) compared to controls (100 +/- 6.11%) (n=6). These results show that 5-HT1B receptors are slightly desensitized in moderately trained animals and totally desensitized in intensely trained animals; moreover, they suggest that the observed desensitization is related to an increase of 5-HT-moduline tissue content; this mechanism may play a role in various pathophysiological conditions. PMID:10882034

  20. Lunar and Martian soil stimulants have different effects on L-[14C]glutamate binding to brain nerve terminals

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Krisanova, Natalia; Nazarova, Anastasiya; Borysov, Arseniy; Chunihin, Olexander

    Nano-sized particles can be deleterious to human physiology because they may be internalized by lung epithelium and overcome the blood-brain barrier. The health effects from exposure to Lunar and Martian dust are almost completely unknown, whereas they can be deleterious to human physiology. The effects of Lunar and Martian Soil Simulants (Orbital Technologies Corporation, Madison, USA) on the conductance of planar lipid membrane, membrane potential, acidification of synaptic vesicles, glutamate uptake, and ambient level of glutamate in isolated rat brain nerve terminals (synaptosomes) were studied using photon correlation spectroscopy, Planar Lipid Bilayer technique, spectrofluorimetry, radiolabeled assay, respectively. Lunar and Martian Soil Simulants did not influence the conductance of planar lipid membrane. It was revealed that nerve terminals were not indifferent to the exposure to inorganic particles of Lunar and Martian Soil Simulants. Using Zetasizer Nanosystem (Malvern Instruments) with helium-neon laser for dynamic light scattering (DLS), the synaptosomal size before and after the addition of Lunar and Martian Soil Simulants was measured and the binding of Lunar and Martian Soil Simulants inorganic particles to nerve terminals was demonstrated. Using potential-sensitive fluorescent dye rhodamine 6G, we showed that Lunar and Martian Soil particles did not influence the potential of the plasma membrane of nerve terminals. Acidification of synaptic vesicles of nerve terminals was not changed in the presence of Lunar and Martian Soil particles that was revealed with pH-sensitive fluorescent dye acridine orange. Martian Soil Simulant particles did not change binding of L-[14C]glutamate to brain nerve terminals, in contrast, Lunar ones changed this parameter and this fact may have harmful consequences to human physiology, in particular, glutamate homeostasis in the mammalian CNS.

  1. Arrest of 5HT neuron differentiation delays respiratory maturation and impairs neonatal homeostatic responses to environmental challenges

    PubMed Central

    Erickson, Jeffery T.; Shafer, Geoffrey; Rossetti, Michael D.; Wilson, Christopher G.; Deneris, Evan S.

    2007-01-01

    Serotonin (5HT) is a powerful modulator of respiratory circuitry in vitro but its role in the development of breathing behavior in vivo is poorly understood. Here we show, using 5HT neuron-deficient Pet-1 (Pet-1−/−) neonates, that serotonergic function is required for the normal timing of postnatal respiratory maturation. Plethysmographic recordings reveal that Pet-1−/− mice are born with a depressed breathing frequency and a higher incidence of spontaneous and prolonged respiratory pauses relative to wild type littermates. The wild type breathing pattern stabilizes by postnatal day 4.5, while breathing remains depressed, highly irregular, and interrupted more frequently by respiratory pauses in Pet-1−/− mice. Analysis of in vitro hypoglossal nerve discharge indicates that instabilities in the central respiratory rhythm generator contribute to the abnormal Pet-1−/− breathing behavior. In addition, the breathing pattern in Pet-1−/− neonates is susceptible to environmental conditions, and can be further destabilized by brief exposure to hypoxia. By postnatal day 9.5, however, breathing frequency in Pet-1−/− animals is only slightly depressed compared to wild type, and prolonged respiratory pauses are rare, indicating that the abnormalities seen earlier in the Pet-1−/− mice are transient. Our findings provide unexpected insight into the development of breathing behavior by demonstrating that defects in 5HT neuron development can extend and exacerbate the period of breathing instability that occurs immediately after birth during which respiratory homeostasis is vulnerable to environmental challenges. PMID:17656160

  2. Interaction of /sup 125/I-labeled botulinum neurotoxins with nerve terminals. II. Autoradiographic evidence for its uptake into motor nerves by acceptor-mediated endocytosis

    SciTech Connect

    Black, J.D.; Dolly, J.O.

    1986-01-01

    Using pharmacological and autoradiographic techniques it has been shown that botulinum neurotoxin (BoNT) is translocated across the motor nerve terminal membrane to reach a postulated intraterminal target. In the present study, the nature of this uptake process was investigated using electron microscopic autoradiography. It was found that internalization is acceptor-mediated and that binding to specific cell surface acceptors involves the heavier chain of the toxin. In addition, uptake was shown to be energy and temperature-dependent and to be accelerated by nerve stimulation, a treatment which also shortens the time course of the toxin-induced neuroparalysis. These results, together with the observation that silver grains were often associated with endocytic structures within the nerve terminal, suggested that acceptor-mediated endocytosis is responsible for toxin uptake. Possible recycling of BoNT acceptors (an important aspect of acceptor-mediated endocytosis of toxins) at motor nerve terminals was indicated by comparing the extent of labeling in the presence and absence of metabolic inhibitors. On the basis of these collective results, it is concluded that BoNT is internalized by acceptor-mediated endocytosis and, hence, the data support the proposal that this toxin inhibits release of acetylcholine by interaction with an intracellular target.

  3. “Late” Macroendosomes and Acidic Endosomes in Vertebrate Motor Nerve Terminals

    PubMed Central

    Stewart, Richard S.; Teng, Haibing; Wilkinson, Robert S.

    2014-01-01

    Activity at the vertebrate nerve—muscle synapse creates large macroendosomes (MEs) via bulk membrane infolding. Visualized with the endocytic probe FM1-43, most (94%) of the ~25 MEs/terminal created by brief (30-Hz, 18-second) stimulation dissipate rapidly (~1 minute) into vesicles. Others, however, remain for hours. Here we study these “ late” MEs by using 4D live imaging over a period of ~1 hour after stimulation. We find that some (51/398 or 13%) disappear spontaneously via exocytosis, releasing their contents into the extracellular milieu. Others (at least 15/1,960 or 1%) fuse or closely associate with a second class of endosomes that take up acidophilic dyes (acidic endosomes [AEs]). AEs are plentiful (~47/terminal) and exist independent of stimulation. Unlike MEs, which exhibit Brownian motion, AEs exhibit directed motion (average, 83 nm/sec) on microtubules within and among terminal boutons. AEs populate the axon as well, where movement is predominantly retrograde. They share biochemical and immunohistochemical markers (e.g., lysosomal-associated membrane protein [LAMP-1]) with lysosomes. Fusion/association of MEs with AEs suggests a sorting/degradation pathway in nerve terminals wherein the role of AEs is similar to that of lysosomes. Based on our data, we propose that MEs serve as sorting endosomes. Thus their contents, which include plasma membrane proteins, vesicle proteins, and extracellular levels of Ca2+, can be targeted either toward the reformation and budding of synaptic vesicles, toward secretion via exocytosis, or toward a degradation process that utilizes AEs either for lysis within the terminal or for transport toward the cell body. PMID:22740045

  4. Systemic inflammation alters central 5-HT function as determined by pharmacological MRI.

    PubMed

    Couch, Yvonne; Martin, Chris J; Howarth, Clare; Raley, Josie; Khrapitchev, Alexandre A; Stratford, Michael; Sharp, Trevor; Sibson, Nicola R; Anthony, Daniel C

    2013-07-15

    Considerable evidence indicates a link between systemic inflammation and central 5-HT function. This study used pharmacological magnetic resonance imaging (phMRI) to study the effects of systemic inflammatory events on central 5-HT function. Changes in blood oxygenation level dependent (BOLD) contrast were detected in selected brain regions of anaesthetised rats in response to intravenous administration of the 5-HT-releasing agent, fenfluramine (10 mg/kg). Further groups of rats were pre-treated with the bacterial lipopolysaccharide (LPS; 0.5 mg/kg), to induce systemic inflammation, or the selective 5-HT2A receptor antagonist MDL100907 prior to fenfluramine. The resultant phMRI data were investigated further through measurements of cortical 5-HT release (microdialysis), and vascular responsivity, as well as a more thorough investigation of the role of the 5-HT2A receptor in sickness behaviour. Fenfluramine evoked a positive BOLD response in the motor cortex (+15.9±2%) and a negative BOLD response in the dorsal raphe nucleus (-9.9±4.2%) and nucleus accumbens (-7.7±5.3%). In all regions, BOLD responses to fenfluramine were significantly attenuated by pre-treatment with LPS (p<0.0001), but neurovascular coupling remained intact, and fenfluramine-evoked 5-HT release was not affected. However, increased expression of the 5-HT2A receptor mRNA and decreased 5-HT2A-dependent behaviour (wet-dog shakes) was a feature of the LPS treatment and may underpin the altered phMRI signal. MDL100907 (0.5 mg/kg), 5-HT2A antagonist, significantly reduced the BOLD responses to fenfluramine in all three regions (p<0.0001) in a similar manner to LPS. Together these results suggest that systemic inflammation decreases brain 5-HT activity as assessed by phMRI. However, these effects do not appear to be mediated by changes in 5-HT release, but are associated with changes in 5-HT2A-receptor-mediated downstream signalling pathways. PMID:23473937

  5. 5-HT2 Receptor Regulation of Mitochondrial Genes: Unexpected Pharmacological Effects of Agonists and Antagonists.

    PubMed

    Harmon, Jennifer L; Wills, Lauren P; McOmish, Caitlin E; Demireva, Elena Y; Gingrich, Jay A; Beeson, Craig C; Schnellmann, Rick G

    2016-04-01

    In acute organ injuries, mitochondria are often dysfunctional, and recent research has revealed that recovery of mitochondrial and renal functions is accelerated by induction of mitochondrial biogenesis (MB). We previously reported that the nonselective 5-HT2 receptor agonist DOI [1-(4-iodo-2,5-dimethoxyphenyl)propan-2-amine] induced MB in renal proximal tubular cells (RPTCs). The goal of this study was to determine the role of 5-HT2 receptors in the regulation of mitochondrial genes and oxidative metabolism in the kidney. The 5-HT2C receptor agonist CP-809,101 [2-[(3-chlorophenyl)methoxy]-6-(1-piperazinyl)pyrazine] and antagonist SB-242,084 [6-chloro-2,3-dihydro-5-methyl-N-[6-[(2-methyl-3-pyridinyl)oxy]-3-pyridinyl]-1H-indole-1-carboxyamide dihydrochloride] were used to examine the induction of renal mitochondrial genes and oxidative metabolism in RPTCs and in mouse kidneys in the presence and absence of the 5-HT2C receptor. Unexpectedly, both CP-809,101 and SB-242,084 increased RPTC respiration and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) mRNA expression in RPTCs at 1-10 nM. In addition, CP-809,101 and SB-242,084 increased mRNA expression of PGC-1α and the mitochondrial proteins NADH dehydrogenase subunit 1 and NADH dehydrogenase (ubiquinone) β subcomplex 8 in mice. These compounds increased mitochondrial genes in RPTCs in which the 5-HT2C receptor was downregulated with small interfering RNA and in the renal cortex of mice lacking the 5-HT2C receptor. By contrast, the ability of these compounds to increase PGC-1α mRNA and respiration was blocked in RPTCs treated with 5-HT2A receptor small interfering RNA or the 5-HT2A receptor antagonist eplivanserin. In addition, the 5-HT2A receptor agonist NBOH-2C-CN [4-[2-[[(2-hydroxyphenyl)methyl]amino]ethyl]-2,5-dimethoxybenzonitrile] increased RPTC respiration at 1-100 nM. These results suggest that agonism of the 5-HT2A receptor induces MB and that the classic 5-HT2C receptor agonist CP

  6. Systemic inflammation alters central 5-HT function as determined by pharmacological MRI

    PubMed Central

    Couch, Yvonne; Martin, Chris J.; Howarth, Clare; Raley, Josie; Khrapitchev, Alexandre A.; Stratford, Michael; Sharp, Trevor; Sibson, Nicola R.; Anthony, Daniel C.

    2013-01-01

    Considerable evidence indicates a link between systemic inflammation and central 5-HT function. This study used pharmacological magnetic resonance imaging (phMRI) to study the effects of systemic inflammatory events on central 5-HT function. Changes in blood oxygenation level dependent (BOLD) contrast were detected in selected brain regions of anaesthetised rats in response to intravenous administration of the 5-HT-releasing agent, fenfluramine (10 mg/kg). Further groups of rats were pre-treated with the bacterial lipopolysaccharide (LPS; 0.5 mg/kg), to induce systemic inflammation, or the selective 5-HT2A receptor antagonist MDL100907 prior to fenfluramine. The resultant phMRI data were investigated further through measurements of cortical 5-HT release (microdialysis), and vascular responsivity, as well as a more thorough investigation of the role of the 5-HT2A receptor in sickness behaviour. Fenfluramine evoked a positive BOLD response in the motor cortex (+ 15.9 ± 2%) and a negative BOLD response in the dorsal raphe nucleus (− 9.9 ± 4.2%) and nucleus accumbens (− 7.7 ± 5.3%). In all regions, BOLD responses to fenfluramine were significantly attenuated by pre-treatment with LPS (p < 0.0001), but neurovascular coupling remained intact, and fenfluramine-evoked 5-HT release was not affected. However, increased expression of the 5-HT2A receptor mRNA and decreased 5-HT2A-dependent behaviour (wet-dog shakes) was a feature of the LPS treatment and may underpin the altered phMRI signal. MDL100907 (0.5 mg/kg), 5-HT2A antagonist, significantly reduced the BOLD responses to fenfluramine in all three regions (p < 0.0001) in a similar manner to LPS. Together these results suggest that systemic inflammation decreases brain 5-HT activity as assessed by phMRI. However, these effects do not appear to be mediated by changes in 5-HT release, but are associated with changes in 5-HT2A-receptor-mediated downstream signalling pathways. PMID:23473937

  7. 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

  8. Involvement of 5-HT3 receptors in the action of vortioxetine in rat brain: Focus on glutamatergic and GABAergic neurotransmission.

    PubMed

    Riga, Maurizio S; Sánchez, Connie; Celada, Pau; Artigas, Francesc

    2016-09-01

    The antidepressant vortioxetine is a 5-HT3-R, 5-HT7-R and 5-HT1D-R antagonist, 5-HT1B-R partial agonist, 5-HT1A-R agonist, and serotonin (5-HT) transporter (SERT) inhibitor. Vortioxetine occupies all targets at high therapeutic doses and only SERT and 5-HT3-R at low doses. Vortioxetine increases extracellular monoamine concentrations in rat forebrain more than selective serotonin reuptake inhibitors (SSRI) and shows pro-cognitive activity in preclinical models. Given its high affinity for 5-HT3-R (Ki = 3.7 nM), selectively expressed in GABA interneurons, we hypothesized that vortioxetine may disinhibit glutamatergic and monoaminergic neurotransmission following 5-HT3-R blockade. Here we assessed vortioxetine effect on pyramidal neuron activity and extracellular 5-HT concentration using in vivo extracellular recordings of rat medial prefrontal cortex (mPFC) pyramidal neurons and microdialysis in mPFC and ventral hippocampus (vHPC). Vortioxetine, but not escitalopram, increased pyramidal neuron discharge in mPFC. This effect was prevented by SR57227A (5-HT3-R agonist) and was mimicked by ondansetron (5-HT3-R antagonist) and by escitalopram/ondansetron combinations. In microdialysis experiments, ondansetron augmented the 5-HT-enhancing effect of escitalopram in mPFC and vHPC. Local ondansetron in vHPC augmented escitalopram effect, indicating the participation of intrinsic mechanisms. Since 5-HT neurons express GABAB receptors, we examined their putative involvement in controlling 5-HT release after 5-HT3-R blockade. Co-perfusion of baclofen (but not muscimol) reversed the increased 5-HT levels produced by vortioxetine and escitalopram/ondansetron combinations in vHPC. The present results suggest that vortioxetine increases glutamatergic and serotonergic neurotransmission in rat forebrain by blocking 5-HT3 receptors in GABA interneurons. PMID:27106166

  9. Distribution of serotonin 5-HT1A-binding sites in the brainstem and the hypothalamus, and their roles in 5-HT-induced sleep and ingestive behaviors in rock pigeons (Columba livia).

    PubMed

    dos Santos, Tiago Souza; Krüger, Jéssica; Melleu, Fernando Falkenburger; Herold, Christina; Zilles, Karl; Poli, Anicleto; Güntürkün, Onur; Marino-Neto, José

    2015-12-15

    Serotonin 1A receptors (5-HT1ARs), which are widely distributed in the mammalian brain, participate in cognitive and emotional functions. In birds, 5-HT1ARs are expressed in prosencephalic areas involved in visual and cognitive functions. Diverse evidence supports 5-HT1AR-mediated 5-HT-induced ingestive and sleep behaviors in birds. Here, we describe the distribution of 5-HT1ARs in the hypothalamus and brainstem of birds, analyze their potential roles in sleep and ingestive behaviors, and attempt to determine the involvement of auto-/hetero-5-HT1ARs in these behaviors. In 6 pigeons, the anatomical distribution of [(3)H]8-OH-DPAT binding in the rostral brainstem and hypothalamus was examined. Ingestive/sleep behaviors were recorded (1h) in 16 pigeons pretreated with MM77 (a heterosynaptic 5-HT1AR antagonist; 23 or 69 nmol) for 20 min, followed by intracerebroventricular ICV injection of 5-HT (N:8; 150 nmol), 8-OH-DPAT (DPAT, a 5-HT1A,7R agonist, 30 nmol N:8) or vehicle. 5-HT- and DPAT-induced sleep and ingestive behaviors, brainstem 5-HT neuronal density and brain 5-HT content were examined in 12 pigeons, pretreated by ICV with the 5-HT neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) or vehicle (N:6/group). The distribution of brainstem and diencephalic c-Fos immunoreactivity after ICV injection of 5-HT, DPAT or vehicle (N:5/group) into birds provided with or denied access to water is also described. 5-HT1ARs are concentrated in the brainstem 5-HTergic areas and throughout the periventricular hypothalamus, preoptic nuclei and circumventricular organs. 5-HT and DPAT produced a complex c-Fos expression pattern in the 5-HT1AR-enriched preoptic hypothalamus and the circumventricular organs, which are related to drinking and sleep regulation, but modestly affected c-Fos expression in 5-HTergic neurons. The 5-HT-induced ingestivebehaviors and the 5-HT- and DPAT-induced sleep behaviors were reduced by MM77 pretreatment. 5,7-DHT increased sleep per se, decreased tryptophan

  10. Interaction between 5-HT1B receptors and nitric oxide in zebrafish responses to novelty.

    PubMed

    Maximino, Caio; Lima, Monica Gomes; Batista, Evander de Jesus Oliveira; Oliveira, Karen Renata Herculano Matos; Herculano, Anderson Manoel

    2015-02-19

    Nitric oxide (NO) and serotonin (5-HT) interact at the molecular and systems levels to control behavioral variables, including agression, fear, and reactions to novelty. In zebrafish, the 5-HT1B receptor has been implicated in anxiety and reactions to novelty, while the 5-HT1A receptor is associated with anxiety-like behavior; this role of the 5-HT1A receptor is mediated by NO. This work investigated whether NO also participates in the mediation of novelty responses by the 5-HT1B receptor. The 5-HT1B receptor inverse agonist SB 224,289 decreased bottom-dwelling and erratic swimming in zebrafish; the effects on bottom-dwelling, but not on erratic swimming, were blocked by pre-treatment with the nitric oxide synthase inhibitor L-NAME. These effects underline a novel mechanism by which 5-HT controls zebrafish reactivity to novel environments, with implications for the study of neotic reactions, exploratory behavior, and anxiety-like states. PMID:25545556

  11. 5-HT1A receptors in mood and anxiety: recent insights into autoreceptor versus heteroreceptor function

    PubMed Central

    Garcia-Garcia, Alvaro; Tancredi, Adrian Newman-; Leonardo, E. David

    2014-01-01

    Rationale Serotonin (5-HT) neurotransmission is intimately linked to anxiety and depression and a diverse body of evidence supports the involvement of the main inhibitory serotonergic receptor, the serotonin-1A (5-HT1A) subtype, in both disorders. Objectives In this review, we examine the function of 5-HT1A receptor sub-populations and re-interpret our understanding of their role in mental illness in light of new data, separating both spatial (autoreceptor vs heteroreceptor) and the temporal (developmental vs adult) roles of the endogenous 5-HT1A receptors, emphasizing their distinct actions in mediating anxiety and depression-like behaviors. Results It is difficult to unambiguously distinguish the effects of different populations of the 5-HT1A receptors with traditional genetic animal models and pharmacological approaches. However, with the advent of novel genetic systems and subpopulation-selective pharmacological agents, direct evidence for distinct roles of these populations in governing emotion related behavior are emerging. Conclusions There is strong and growing evidence for a functional dissociation between auto and heteroreceptor populations in mediating anxiety and depressive-like behaviors respectively. Furthermore, while it is well established that 5-HT1A receptors act developmentally to establish normal anxiety-like behaviors, the developmental role of 5-HT1A heteroreceptors is less clear, and the specific mechanisms underlying the developmental role of each subpopulation are likely to be key elements determining mood control in adult subjects. PMID:24337875

  12. The 5-HT7 receptor in learning and memory. Importance of the hippocampus

    PubMed Central

    Roberts, Amanda J.; Hedlund, Peter B.

    2011-01-01

    The 5-HT7 receptor is a more recently discovered G-protein-coupled receptor for serotonin. The functions and possible clinical relevance of this receptor are not yet fully understood. The present paper reviews to what extent the use of animal models of learning and memory and other techniques have implicated the 5-HT7 receptor in such processes. The studies have used a combination of pharmacological and genetic tools targeting the receptor to evaluate effects on behavior and cellular mechanisms. In tests such as the Barnes maze, contextual fear conditioning and novel location recognition that involve spatial learning and memory there is a considerable amount of evidence supporting an involvement of the 5-HT7 receptor. Supporting evidence has also been obtained in studies of mRNA expression and cellular signaling as well as in electrophysiological experiments. Especially interesting are the subtle but distinct effects observed in hippocampus-dependent models of place learning where impairments have been described in mice lacking the 5-HT7 receptor or after administration of a selective antagonist. While more work is required, it appears that 5-HT7 receptors are particularly important in allocentric representation processes. In instrumental learning tasks both procognitive effects and impairments in memory have been observed using pharmacological tools targeting the 5-HT7 receptor. In conclusion, the use of pharmacological and genetic tools in animal studies of learning and memory suggest a potentially important role for the 5-HT7 receptor in cognitive processes. PMID:21484935

  13. Impact of Lipid Raft Integrity on 5-HT3 Receptor Function and its Modulation by Antidepressants

    PubMed Central

    Nothdurfter, Caroline; Tanasic, Sascha; Di Benedetto, Barbara; Rammes, Gerhard; Wagner, Eva-Maria; Kirmeier, Thomas; Ganal, Vanessa; Kessler, Julia S; Rein, Theo; Holsboer, Florian; Rupprecht, Rainer

    2010-01-01

    Because of the biochemical colocalization of the 5-HT3 receptor and antidepressants within raft-like domains and their antagonistic effects at this ligand-gated ion channel, we investigated the impact of lipid raft integrity for 5-HT3 receptor function and its modulation by antidepressants. Treatment with methyl-β-cyclodextrine (MβCD) markedly reduced membrane cholesterol levels and caused a more diffuse membrane distribution of the lipid raft marker protein flotillin-1 indicating lipid raft impairment. Both amplitude and charge of serotonin evoked cation currents were diminished following cholesterol depletion by either MβCD or simvastatin (Sim), whereas the functional antagonistic properties of the antidepressants desipramine (DMI) and fluoxetine (Fluox) at the 5-HT3 receptor were retained. Although both the 5-HT3 receptor and flotillin-1 were predominantly found in raft-like domains in western blots following sucrose density gradient centrifugation, immunocytochemistry revealed only a coincidental degree of colocalization of these two proteins. These findings and the persistence of the antagonistic effects of DMI and Fluox against 5-HT3 receptors after lipid raft impairment indicate that their modulatory effects are likely mediated through non-raft 5-HT3 receptors, which are not sufficiently detected by means of sucrose density gradient centrifugation. In conclusion, lipid raft integrity appears to be important for 5-HT3 receptor function in general, whereas it is not a prerequisite for the antagonistic properties of antidepressants such as DMI and Fluox at this ligand-gated ion channel. PMID:20200506

  14. Two transmembrane Cys residues are involved in 5-HT4 receptor dimerization.

    PubMed

    Berthouze, Magali; Rivail, Lucie; Lucas, Alexandre; Ayoub, Mohammed A; Russo, Olivier; Sicsic, Sames; Fischmeister, Rodolphe; Berque-Bestel, Isabelle; Jockers, Ralf; Lezoualc'h, Frank

    2007-05-11

    The 5-HT(4) receptor (5-HT(4)R) belongs to the G-protein-coupled receptor (GPCR) family and is of considerable interest for the development of new drugs to treat gastrointestinal diseases and memory disorders. The 5-HT(4)R exists as a constitutive dimer but its molecular determinants are still unknown. Using co-immunoprecipitation and Bioluminescence Resonance Energy Transfer (BRET) techniques, we show here that 5-HT(4)R homodimerization but not 5-HT(4)R-beta(2) adrenergic receptor (beta(2)AR) heterodimerization is largely decreased under reducing conditions suggesting the participation of disulfide bonds in 5-HT(4)R dimerization. Molecular modeling and protein docking experiments identified four cysteine (Cys) residues potentially involved in the dimer interface through intramolecular or intermolecular disulfide bonds. We show that disulfide bridges between Cys112 and Cys145 located within TM3 and TM4, respectively, are of critical importance for 5-HT(4)R dimer formation. Our data suggest that two disulfide bridges between two transmembrane Cys residues are involved in the dimerization interface of a GPCR. PMID:17379184

  15. Application of an Integrated GPCR SAR-Modeling Platform To Explain the Activation Selectivity of Human 5-HT2C over 5-HT2B.

    PubMed

    Heifetz, Alexander; Storer, R Ian; McMurray, Gordon; James, Tim; Morao, Inaki; Aldeghi, Matteo; Bodkin, Mike J; Biggin, Philip C

    2016-05-20

    Agonism of the 5-HT2C serotonin receptor has been associated with the treatment of a number of diseases including obesity, psychiatric disorders, sexual health, and urology. However, the development of effective 5-HT2C agonists has been hampered by the difficulty in obtaining selectivity over the closely related 5-HT2B receptor, agonism of which is associated with irreversible cardiac valvulopathy. Understanding how to design selective agonists requires exploration of the structural features governing the functional uniqueness of the target receptor relative to related off targets. X-ray crystallography, the major experimental source of structural information, is a slow and challenging process for integral membrane proteins, and so is currently not feasible for every GPCR or GPCR-ligand complex. Therefore, the integration of existing ligand SAR data with GPCR modeling can be a practical alternative to provide this essential structural insight. To demonstrate this, we integrated SAR data from 39 azepine series 5-HT2C agonists, comprising both selective and unselective examples, with our hierarchical GPCR modeling protocol (HGMP). Through this work we have been able to demonstrate how relatively small differences in the amino acid sequences of GPCRs can lead to significant differences in secondary structure and function, as supported by experimental data. In particular, this study suggests that conformational differences in the tilt of TM7 between 5-HT2B and 5-HT2C, which result from differences in interhelical interactions, may be the major source of selectivity in G-protein activation between these two receptors. Our approach also demonstrates how the use of GPCR models in conjunction with SAR data can be used to explain activity cliffs. PMID:26900768

  16. Distinct effect of 5-HT1A and 5-HT2A receptors in the medial nucleus of the amygdala on tonic immobility behavior.

    PubMed

    de Paula, Bruna Balbino; Leite-Panissi, Christie Ramos Andrade

    2016-07-15

    The tonic immobility (TI) response is an innate fear behavior associated with intensely dangerous situations, exhibited by many species of invertebrate and vertebrate animals. In humans, it is possible that TI predicts the severity of posttraumatic stress disorder symptoms. This behavioral response is initiated and sustained by the stimulation of various groups of neurons distributed in the telencephalon, diencephalon and brainstem. Previous research has found the highest Fos-IR in the posteroventral part of the medial nucleus of the amygdala (MEA) during TI behavior; however, the neurotransmission of this amygdaloid region involved in the modulation of this innate fear behavior still needs to be clarified. Considering that a major drug class used for the treatment of psychopathology is based on serotonin (5-HT) neurotransmission, we investigated the effects of serotonergic receptor activation in the MEA on the duration of TI. The results indicate that the activation of the 5HT1A receptors or the blocking of the 5HT2 receptors of the MEA can promote a reduction in fear and/or anxiety, consequently decreasing TI duration in guinea pigs. In contrast, blocking the 5HT1A receptors or activating the 5HT2 receptors in this amygdalar region increased the TI duration, suggesting an increase in fear and/or anxiety. These alterations do not appear to be due to a modification of spontaneous motor activity, which might non-specifically affect TI duration. Thus, these results suggest a distinct role of the 5HT receptors in the MEA in innate fear modulation. PMID:27150816

  17. Unraveling mechanisms underlying partial agonism in 5-HT3A receptors.

    PubMed

    Corradi, Jeremías; Bouzat, Cecilia

    2014-12-10

    Partial agonists have emerged as attractive therapeutic molecules. 2-Me-5HT and tryptamine have been defined as partial agonists of 5-HT3 receptors on the basis of macroscopic measurements. Because several mechanisms may limit maximal responses, we took advantage of the high-conductance form of the mouse serotonin type 3A (5-HT3A) receptor to understand their molecular actions. Individual 5-HT-bound receptors activate in long episodes of high open probability, consisting of groups of openings in quick succession. The activation pattern is similar for 2-Me-5HT only at very low concentrations since profound channel blockade takes place within the activating concentration range. In contrast, activation episodes are significantly briefer in the presence of tryptamine. Generation of a full activation scheme reveals that the fully occupied receptor overcomes transitions to closed preopen states (primed states) before opening. Reduced priming explains the partial agonism of tryptamine. In contrast, 2-Me-5HT is not a genuine partial agonist since priming is not dramatically affected and its low apparent efficacy is mainly due to channel blockade. The analysis also shows that the first priming step is the rate-limiting step and partial agonists require an increased number of priming steps for activation. Molecular docking suggests that interactions are similar for 5-HT and 2-Me-5HT but slightly different for tryptamine. Our study contributes to understanding 5-HT3A receptor activation, extends the novel concept of partial agonism within the Cys-loop family, reveals novel aspects of partial agonism, and unmasks molecular actions of classically defined partial agonists. Unraveling mechanisms underlying partial responses has implications in the design of therapeutic compounds. PMID:25505338

  18. Pet imaging of human pituitary 5-HT2 receptors with F-18 setoperone

    SciTech Connect

    Fischman, A.J.; Bonab, A.A.; Babich, J.W.

    1995-05-01

    Serotonin (5-HT) receptors play an important role in the regulation of pituitary function. In particular, 5HT agonists stimulate ACTH, {beta}-endorphin, prolactin and growth hormone secretion but inhibit TSH release. 5-HT binding sites have been identified by autoradiographic studies of rat and human pituitary. In the present investigation, we used PET with F-18 setoperone to image 5-HT2 receptors in normal humans. Setoperone, a piperidine derivative with potent 5-HT2 receptor blocking properties was labelled with F-18 by nucleophilic substitution on the nitro derivative. After HPLC purification, specific activity was between 10,000 and 15,000 mCi/{mu} mole and radiochemical purity was >98%. Six healthy male volunteers were injected with 5-7 mCi of F-18. Setoperone and serial PET images and arterial blood samples were collected over 2 hrs. Specific binding to 5-HT2 receptors in the frontal cortex (FC), striatum (ST) and pituitary (P) was quantitated using the cerebellum (C) as reference. The tracer showed clear retention in FC, ST and P (known to contain a high density of 5-HT2 receptors) relative to C (known to be devoid of 5-HT2 receptors). In all subjects, FC/C, ST/C and P/C ratios increased during the first hr. and remained stable thereafter. For FC and ST, the ratios reached similar values; 3.92{plus_minus}0.73 and 3.53{plus_minus}0.32. For pituitary, a significantly higher ratio, was measured at all times; 6.53{plus_minus}1.82 (p<0.01). These results indicate that F-18 setoperone is an effective PET radiopharmaceutical for imaging 5-HT2 receptors in the human pituitary. Future applications of this agent could provide important new insights into neuroendocrine function.

  19. Mutational analysis of the promoter and the coding region of the 5-HT1A gene

    SciTech Connect

    Erdmann, J.; Noethen, M.M.; Shimron-Abarbanell, D.

    1994-09-01

    Disturbances of serotonergic pathways have been implicated in many neuropsychiatric disorders. Serotonin (5HT) receptors can be subdivided into at least three major families (5HT1, 5HT2, and 5HT3). Five human 5HT1 receptor subtypes have been cloned, namely 1A, 1D{alpha}, 1D{beta}, 1E, and 1F. Of these, the 5HT1A receptor is the best characterized subtype. In the present study we sought to identify genetic variation in the 5HT1A receptor gene which through alteration of protein function or level of expression might contribute to the genetics of neuropsychiatric diseases. The coding region and the 5{prime} promoter region of the 5HT1A gene from 159 unrelated subjects (45 schizophrenic, 46 bipolar affective, and 43 patients with Tourette`s syndrome, as well as 25 controls) were analyzed using SSCA. SSCA revealed the presence of two mutations both located in the coding region of the 5HT1A receptor gene. The first mutation is a rare silent C{r_arrow}T substitution at nucleotide position 549. The second mutation is characterized by a base pair substitution (A{r_arrow}G) at the first position of codon 28 and results in an amino acid exchange (Ile{r_arrow}Val). Since Val28 was found only in a single schizophrenic patient and in none of the other patients or controls, we decided to extend our samples and to use a restriction assay for screening a further 74 schizophrenic, 95 bipolar affective, and 49 patients with Tourette`s syndrome, as well as 185 controls, for the presence of the mutation. In total, the mutation was found in 2 schizophrenic patients, in 3 bipolars, in 1 Tourette patient, and in 5 controls. To our knowledge the Ile-28-Val substitution reported here is the first natural occuring molecular variant which has been identified for a serotonin receptor so far.

  20. Therapeutic Potential of 5-HT2C Receptor Agonists for Addictive Disorders.

    PubMed

    Higgins, Guy A; Fletcher, Paul J

    2015-07-15

    The neurotransmitter 5-hydroxytryptamine (5-HT; serotonin) has long been associated with the control of a variety of motivated behaviors, including feeding. Much of the evidence linking 5-HT and feeding behavior was obtained from studies of the effects of the 5-HT releaser (dex)fenfluramine in laboratory animals and humans. Recently, the selective 5-HT2C receptor agonist lorcaserin received FDA approval for the treatment of obesity. This review examines evidence to support the use of selective 5-HT2C receptor agonists as treatments for conditions beyond obesity, including substance abuse (particularly nicotine, psychostimulant, and alcohol dependence), obsessive compulsive, and excessive gambling disorder. Following a brief survey of the early literature supporting a role for 5-HT in modulating food and drug reinforcement, we propose that intrinsic differences between SSRI and serotonin releasers may have underestimated the value of serotonin-based pharmacotherapeutics to treat clinical forms of addictive behavior beyond obesity. We then highlight the critical involvement of the 5-HT2C receptor in mediating the effect of (dex)fenfluramine on feeding and body weight gain and the evidence that 5-HT2C receptor agonists reduce measures of drug reward and impulsivity. A recent report of lorcaserin efficacy in a smoking cessation trial further strengthens the idea that 5-HT2C receptor agonists may have potential as a treatment for addiction. This review was prepared as a contribution to the proceedings of the 11th International Society for Serotonin Research Meeting held in Hermanus, South Africa, July 9-12, 2014. PMID:25870913

  1. Vascular reactivity, 5-HT uptake, and blood pressure in the serotonin transporter knockout rat.

    PubMed

    Linder, A Elizabeth; Diaz, Jessica; Ni, Wei; Szasz, Theo; Burnett, Robert; Watts, Stephanie W

    2008-04-01

    The handling of serotonin [5-hydroxytryptamine (5-HT)] depends on the serotonin transporter (SERT). A SERT knockout (KO) rat is a useful model to test the hypothesis that SERT is the primary mechanism for arterial 5-HT uptake and to investigate the impact of SERT removal on blood pressure. Wild-type (WT) and KO rats were used to measure 5-HT content (plasma, raphe, aorta, carotid, and mesenteric artery), aortic isometric contraction, and blood pressure. HPLC supported the lack of circulating 5-HT in plasma (ng/ml plasma, WT, 310 +/- 96; and KO, 1.0 +/- 0.5; P < 0.05). Immunohistochemistry and Western blot analyses validated the presence of the SERT protein in the WT rats and a lesser expression in the KO rat. The aorta isolated from KO rats had a normal contraction to phenylephrine and norepinephrine and a normal relaxation to the endothelium-dependent agonist acetylcholine compared with the aorta from WT. In contrast, the potency of 5-HT was increased in the aorta from KO rats compared with WT rats [-log EC(50) (M); WT, 5.71 +/- 0.08; and KO, 6.7 +/- 0.18] and maximum contraction was reduced [%phenylephrine (10 muM) contraction, WT, 113 +/- 6%; and KO, 52 +/- 12%]. 5-HT uptake was reduced but not abolished in arteries of the KO compared with the WT rats. Diurnal mean arterial blood pressure, heart rate, and locomotor activity level of the KO rats were similar to the WT rats. These data suggest that there are other mechanisms of 5-HT uptake in the arteries of the rat and that although the absence of circulating 5-HT and/or SERT function sensitizes arteries to 5-HT, SERT dysfunction does not impair normal blood pressure. PMID:18263707

  2. Familial Risk for Major Depression is Associated with Lower Striatal 5-HT4 Receptor Binding

    PubMed Central

    Madsen, Karine; Torstensen, Eva; Holst, Klaus K.; Haahr, Mette E.; Knorr, Ulla; Frokjaer, Vibe G.; Brandt-Larsen, Malene; Iversen, Pernille; Fisher, Patrick M.

    2015-01-01

    Background: The 5-HT4 receptor provides a novel potential target for antidepressant treatment. No studies exist to elucidate the 5-HT4 receptor’s in vivo distribution in the depressed state or in populations that may display trait markers for major depression disorder (MDD). The aim of this study was to determine whether familial risk for MDD is associated with cerebral 5-HT4 receptor binding as measured with [11C]SB207145 brain PET imaging. Familial risk is the most potent risk factor of MDD. Methods: We studied 57 healthy individuals (mean age 36 yrs, range 20–86; 21 women), 26 of which had first-degree relatives treated for MDD. Results: We found that having a family history of MDD was associated with lower striatal 5-HT4 receptor binding (p = 0.038; in individuals below 40 years, p = 0.013). Further, we found evidence for a “risk-dose effect” on 5-HT4 receptor binding, since the number of first-degree relatives with a history of MDD binding correlated negatively with 5-HT4 receptor binding in both the striatum (p = 0.001) and limbic regions (p = 0.012). Conclusions: Our data suggest that the 5-HT4 receptor is involved in the neurobiological mechanism underlying familial risk for depression, and that lower striatal 5-HT4 receptor binding is associated with increased risk for developing MDD. The finding is intriguing considering that the 5-HT4 receptor has been suggested to be an effective target for antidepressant treatment. PMID:25522384

  3. Analysis of protein phosphorylation in nerve terminal reveals extensive changes in active zone proteins upon exocytosis.

    PubMed

    Kohansal-Nodehi, Mahdokht; Chua, John Je; Urlaub, Henning; Jahn, Reinhard; Czernik, Dominika

    2016-01-01

    Neurotransmitter release is mediated by the fast, calcium-triggered fusion of synaptic vesicles with the presynaptic plasma membrane, followed by endocytosis and recycling of the membrane of synaptic vesicles. While many of the proteins governing these processes are known, their regulation is only beginning to be understood. Here we have applied quantitative phosphoproteomics to identify changes in phosphorylation status of presynaptic proteins in resting and stimulated nerve terminals isolated from the brains of Wistar rats. Using rigorous quantification, we identified 252 phosphosites that are either up- or downregulated upon triggering calcium-dependent exocytosis. Particularly pronounced were regulated changes of phosphosites within protein constituents of the presynaptic active zone, including bassoon, piccolo, and RIM1. Additionally, we have mapped kinases and phosphatases that are activated upon stimulation. Overall, our study provides a snapshot of phosphorylation changes associated with presynaptic activity and provides a foundation for further functional analysis of key phosphosites involved in presynaptic plasticity. PMID:27115346

  4. Ca2+ and calmodulin initiate all forms of endocytosis during depolarization at a nerve terminal

    PubMed Central

    Xu, Jianhua; Fan, Junmei; Xue, Lei; Melicoff, Ernestina; Adachi, Roberto; Bai, Li; Wu, Ling-Gang

    2016-01-01

    Although endocytosis maintains synaptic transmission, how endocytosis is initiated is unclear. We found that calcium influx initiated all forms of endocytosis at a single nerve terminal in rodents, including clathrin-dependent slow endocytosis, bulk endocytosis, rapid endocytosis and endocytosis overshoot (excess endocytosis), with each being evoked with a correspondingly higher calcium threshold. As calcium influx increased, endocytosis gradually switched from very slow endocytosis to slow endocytosis to bulk endocytosis to rapid endocytosis and to endocytosis overshoot. The calcium-induced endocytosis rate increase was a result of the speeding up of membrane invagination and fission. Pharmacological experiments suggested that the calcium sensor mediating these forms of endocytosis is calmodulin. In addition to its role in recycling vesicles, calcium/calmodulin-initiated endocytosis facilitated vesicle mobilization to the readily releasable pool, probably by clearing fused vesicle membrane at release sites. Our findings provide a unifying mechanism for the initiation of various forms of endocytosis that are critical in maintaining exocytosis. PMID:19633667

  5. TRPA1 activation by lidocaine in nerve terminals results in glutamate release increase

    SciTech Connect

    Piao, L.-H.; Fujita, Tsugumi; Jiang, C.-Y.; Liu Tao; Yue, H.-Y.; Nakatsuka, Terumasa; Kumamoto, Eiichi

    2009-02-20

    We examined the effects of local anesthetics lidocaine and procaine on glutamatergic spontaneous excitatory transmission in substantia gelatinosa (SG) neurons in adult rat spinal cord slices with whole-cell patch-clamp techniques. Bath-applied lidocaine (1-5 mM) dose-dependently and reversibly increased the frequency but not the amplitude of spontaneous excitatory postsynaptic current (sEPSC) in SG neurons. Lidocaine activity was unaffected by the Na{sup +}-channel blocker, tetrodotoxin, and the TRPV1 antagonist, capsazepine, but was inhibited by the TRP antagonist, ruthenium red. In the same neuron, the TRPA1 agonist, allyl isothiocyanate, and lidocaine both increased sEPSC frequency. In contrast, procaine did not produce presynaptic enhancement. These results indicate that lidocaine activates TRPA1 in nerve terminals presynaptic to SG neurons to increase the spontaneous release of L-glutamate.

  6. Transmission block in terminal nerve twigs: a single fibre electromyographic finding in man

    PubMed Central

    Stålberg, Erik; Thiele, Barbara

    1972-01-01

    Single fibre electromyography has been performed in patients with partial nerve lesions, amyotrophic lateral sclerosis, progressive spinal muscle atrophy, muscular dystrophy, and distal hereditary myopathy. The recorded action potentials were often more complex than in the normal muscle due to increased fibre density in the motor unit and the individual spike components showed a large jitter and occasional blockings. Sometimes two or more spikes in a complex disappeared and reappeared simultaneously upon successive discharges. This phenomenon, called `paired blocking', has been further investigated. The jitter of the blocking potentials in relation to the rest of the complex was large, up to 500 μsec. The degree of blocking increased with increasing innervation frequency until it eventually proceeded to total block during continuous activity. Sometimes a slight effect on blocking was seen after edrophonium. This type of block is probably localized in the terminal nerve twigs, perhaps in newly formed sprouts. The phenomenon of neurogenic blocking may contribute to the fatigue clinically experienced in different denervation-reinnervation cases. Images PMID:4337272

  7. Design, Synthesis, and Evaluation of Tetrasubstituted Pyridines as Potent 5-HT2C Receptor Agonists

    PubMed Central

    2015-01-01

    A series of pyrido[3,4-d]azepines that are potent and selective 5-HT2C receptor agonists is disclosed. Compound 7 (PF-04781340) is identified as a suitable lead owing to good 5-HT2C potency, selectivity over 5-HT2B agonism, and in vitro ADME properties commensurate with an orally available and CNS penetrant profile. The synthesis of a novel bicyclic tetrasubstituted pyridine core template is outlined, including rationale to account for the unexpected formation of aminopyridine 13 resulting from an ammonia cascade cyclization. PMID:25815155

  8. Mechanism for the acute effects of organophosphate pesticides on the adult 5-HT system

    PubMed Central

    Judge, Sarah J.; Savy, Claire Y.; Campbell, Matthew; Dodds, Rebecca; Gomes, Larissa Kruger; Laws, Grace; Watson, Anna; Blain, Peter G.; Morris, Christopher M.; Gartside, Sarah E.

    2016-01-01

    The neurotransmitter serotonin (5-HT) is involved in mood disorder aetiology and it has been reported that (organophosphate) OP exposure affects 5-HT turnover. The aim of this study was to elucidate the mechanism underlying OP effects on the adult 5-HT system. First, acute in vivo administration of the OP diazinon (0, 1.3, 13 or 39 mg/kg i.p.) to male Hooded Lister rats inhibited the activity of the cholinergic enzyme acetylcholinesterase in blood and in the hippocampus, dorsal raphe nucleus (DRN), striatum and prefrontal cortex. Diazinon-induced cholinesterase inhibition was greatest in the DRN, the brain's major source of 5-HT neurones. Second, acute in vivo diazinon exposure (0 or 39 mg/kg i.p.) increased the basal firing rate of DRN neurones measured ex vivo in brain slices. The excitatory responses of DRN neurones to α1-adrenoceptor or AMPA/kainate receptor activation were not affected by in vivo diazinon exposure but the inhibitory response to 5-HT was attenuated, indicating 5-HT1A autoreceptor down-regulation. Finally, direct application of the diazinon metabolite diazinon oxon to naive rat brain slices increased the firing rate of DRN 5-HT neurones, as did chlorpyrifos-oxon, indicating the effect was not unique to diazinon. The oxon-induced augmentation of firing was blocked by the nicotinic acetylcholine receptor antagonist mecamylamine and the AMPA/kainate glutamate receptor antagonist DNQX. Together these data indicate that 1) acute OP exposure inhibits DRN cholinesterase, leading to acetylcholine accumulation, 2) the acetylcholine activates nicotinic receptors on 5-HT neurones and also on glutamatergic neurones, thus releasing glutamate and activating 5-HT neuronal AMPA/kainate receptors 3) the increase in 5-HT neuronal activity, and resulting 5-HT release, may lead to 5-HT1A autoreceptor down-regulation. This mechanism may be involved in the reported increase in risk of developing anxiety and depression following occupational OP exposure. PMID

  9. Visualization of endosome dynamics in living nerve terminals with four-dimensional fluorescence imaging.

    PubMed

    Stewart, Richard S; Kiss, Ilona M; Wilkinson, Robert S

    2014-01-01

    Four-dimensional (4D) light imaging has been used to study behavior of small structures within motor nerve terminals of the thin transversus abdominis muscle of the garter snake. Raw data comprises time-lapse sequences of 3D z-stacks. Each stack contains 4-20 images acquired with epifluorescence optics at focal planes separated by 400-1,500 nm. Steps in the acquisition of image stacks, such as adjustment of focus, switching of excitation wavelengths, and operation of the digital camera, are automated as much as possible to maximize image rate and minimize tissue damage from light exposure. After acquisition, a set of image stacks is deconvolved to improve spatial resolution, converted to the desired 3D format, and used to create a 4D "movie" that is suitable for variety of computer-based analyses, depending upon the experimental data sought. One application is study of the dynamic behavior of two classes of endosomes found in nerve terminals-macroendosomes (MEs) and acidic endosomes (AEs)-whose sizes (200-800 nm for both types) are at or near the diffraction limit. Access to 3D information at each time point provides several advantages over conventional time-lapse imaging. In particular, size and velocity of movement of structures can be quantified over time without loss of sharp focus. Examples of data from 4D imaging reveal that MEs approach the plasma membrane and disappear, suggesting that they are exocytosed rather than simply moving vertically away from a single plane of focus. Also revealed is putative fusion of MEs and AEs, by visualization of overlap between the two dye-containing structures as viewed in each three orthogonal projections. PMID:24799002

  10. Evidence of 5-HT components in human sperm: implications for protein tyrosine phosphorylation and the physiology of motility

    PubMed Central

    Jiménez-Trejo, Francisco; Tapia-Rodríguez, Miguel; Cerbón, Marco; Kuhn, Donald M; Manjarrez-Gutiérrez, Gabriel; Mendoza-Rodríguez, C Adriana; Picazo, Ofir

    2016-01-01

    Serotonin (5-hydroxytryptamine; C10H12N2O (5-HT)) is produced in the CNS and in some cells of peripheral tissues. In the mammalian male reproductive system, both 5-HT and tryptophan hydroxylase (TPH) have been described in Leydig cells of the testis and in principal cells of the caput epididymis. In capacitated hamster sperm, it has been shown that 5-HT promotes the acrosomal reaction. The aim of this work was to explore the existence of components of the serotoninergic system and their relevance in human sperm physiology. We used both immunocytochemistry and western blot to detect serotoninergic markers such as 5-HT, TPH1, MAOA, 5-HT1B, 5-HT3, and 5HTT; HPLC for TPH enzymatic activity; Computer Assisted Semen Analysis assays to measure sperm motility parameters and pharmacological approaches to show the effect of 5-HT in sperm motility and tyrosine phosphorylation was assessed by western blot. We found the presence of serotoninergic markers (5-HT, TPH1, MAOA, 5-HT1B, 5-HT2A, 5-HT3, 5-HTT, and TPH enzymatic activity) in human sperm. In addition, we observed a significant increase in tyrosine phosphorylation and changes in sperm motility after 5-HT treatment. In conclusion, our data demonstrate the existence of components of a serotoninergic system in human sperm and support the notion for a functional role of 5-HT in mammalian sperm physiology, which can be modulated pharmacologically. PMID:23028123

  11. Direct measurement of ACh release from exposed frog nerve terminals: constraints on interpretation of non-quantal release.

    PubMed Central

    Grinnell, A D; Gundersen, C B; Meriney, S D; Young, S H

    1989-01-01

    1. Acetylcholine (ACh) release from enzymatically exposed frog motor nerve terminals has been measured directly with closely apposed outside-out clamped patches of Xenopus myocyte membrane, rich in ACh receptor channels. When placed close to the synaptic surface of the terminal, such a membrane patch detects both nerve-evoked patch currents (EPCs) and spontaneous quantal 'miniature' patch currents (MPCs), from a few micrometres length of the terminal, in response to ACh release from the nearest three to five active zones. 2. Chemical measurements of ACh efflux from whole preparations revealed a spontaneous release rate of 4.1 pmol (2 h)-1, and no significant difference in resting efflux between enzyme-treated and control preparations. The ratio of enzyme-treated to contralateral control muscle efflux averaged 1.17, indicating that enzyme treatment did not affect spontaneous ACh release. Vesamicol (1.7 microM), which blocks the ACh transporter in synaptic vesicles, decreased the spontaneous release of ACh to 67% of control. 3. In the absence of nerve stimulation, the frequency of single-channel openings recorded by outside-out patch probes adjacent to nerve terminals was very low (1-2 min-1), and little different at a distance of hundreds of micrometres, suggesting that if ACh was continually leaking from the terminal in a non-quantal fashion, the amount being released near active zone regions on the terminal was below the limit of detection with the patches. 4. Direct measurements of the sensitivity of the patches, coupled with calculated ACh flux rates, lead to the conclusion that the amount of ACh released non-quantally from the synaptic surface of the frog nerve terminal is less than one-tenth the amount expected if all non-quantal release is from this region of the terminal membrane. 5. Following a series of single nerve shocks or a 50 Hz train of nerve stimuli, the frequency of asynchronous single-channel openings increased for several seconds. This transient

  12. Effect of morphine on the nerve terminal impulse and transmitter release from sympathetic varicosities innervating the mouse vas deferens.

    PubMed Central

    Lavidis, N. A.

    1995-01-01

    1 The effect of morphine on both the propagation of the nerve terminal impulse along the sympathetic varicose axons as well as the evoked and spontaneous transmitter release has been evaluated. 2 Morphine (1 microM) did not significantly change the shape or the regularity by which the nerve terminal impulse was recorded while evoked transmitter release was greatly reduced. 3 Morphine induced a uniform decrease in evoked transmitter release irrespective of the release probability of individual varicosities of their position along terminal branches. 4 Procedures which are thought to increase intracellular calcium concentration such as increasing the extracellular calcium concentration, stimulation of the nerve with trains of impulses and increasing the duration of the action potential with 4-aminopyridine reduced the ability of morphine to decrease evoked transmitter release. 5 Morphine had to act directly on the varicosities to induce a decrease in evoked transmitter release. 6 The decrease in evoked quantal release does not involve an affect on the nerve terminal impulse or the vesicle release process and morphine may affect the dependence of the secretory process on calcium. PMID:8680716

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

    NASA Astrophysics Data System (ADS)

    Salzberg, Brian M.

    2008-03-01

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

  14. Functional antagonistic properties of clozapine at the 5-HT3 receptor.

    PubMed

    Hermann, B; Wetzel, C H; Pestel, E; Zieglgänsberger, W; Holsboer, F; Rupprecht, R

    1996-08-23

    The atypical neuroleptic clozapine is thought to exert its psychopharmacological actions through a variety of neurotransmitter receptors. It binds preferentially to D4 and 5-HT2 receptors; however, little is known on it's interaction with the 5-HT3 receptor. Using a cell line stably expressing the 5-HT3 receptor, whole-cell voltage-clamp analysis revealed functional antagonistic properties of clozapine at low nanomolar concentrations in view of a binding affinity in the upper nanomolar range. Because the concentration of clozapine required for an interaction with the 5-HT3 receptor can be achieved with therapeutical doses, functional antagonistic properties at this ligand-gated ion channel may contribute to its unique psychopharmacological profile. PMID:8780717

  15. Serotonin 5-ht2c receptor agonists: potential for the treatment of obesity.

    PubMed

    Miller, Keith J

    2005-10-01

    Obesity continues to be a burgeoning health problem worldwide. Before their removal from the market, fenfluramine and the more active enantiomer dexfenfluramine were considered to be among the most effective of weight loss agents. Much of the weight loss produced by fenfluramine was attributed to the direct activation of serotonin 5-HT(2C) receptors in the central nervous system via the desmethyl-metabolite of fenfluramine, norfenfluramine. Norfenfluramine, however, is non-selective, activating additional serotonin receptors, such as 5-HT(2A) and 5-HT(2B), which likely mediated the heart valve hypertrophy seen in many patients. Development of highly selective 5-HT(2C) agonists may recapitulate the clinical anti-obesity properties observed with fenfluramine while avoiding the significant cardiovascular and pulmonary side effects. PMID:16249524

  16. Regulation of the amyloid precursor protein ectodomain shedding by the 5-HT4 receptor and Epac.

    PubMed

    Robert, Sylvain; Maillet, Marjorie; Morel, Eric; Launay, Jean-Marie; Fischmeister, Rodolphe; Mercken, Luc; Lezoualc'h, Frank

    2005-02-14

    The serotonin 5-hydroxytryptamine (5-HT4) receptor is of potential interest for the treatment of Alzheimer's disease because it increases memory and learning. In this study, we investigated the effect of zinc metalloprotease inhibitors on the amyloid precursor protein (APP) processing induced by the serotonin 5-HT4 receptor in vitro. We show that secretion of the non-amyloidogenic form of APP, sAPPalpha induced by the 5-HT4(e) receptor isoform was not due to a general boost of the constitutive secretory pathway but rather to its specific effect on alpha-secretase activity. Although the h5-HT4(e) receptor increased IP3 production, inhibition of PKC did not modify its effect on sAPPalpha secretion. In addition, we found that alpha secretase activity is regulated by the cAMP-regulated guanine nucleotide exchange factor, Epac and the small GTPase Rac. PMID:15710402

  17. Target size analysis of serotonin 5-HT/sub 1/ and 5-HT/sub 2/ receptors in bovine brain membranes

    SciTech Connect

    Nishino, N.; Tanaka, C.

    1985-09-23

    Freeze-dried crude synaptic membranes prepared from bovine cerebral cortex and striatum were exposed to high energy gamma ray from the source of /sup 60/Co. The size of serotonin 5-HT/sub 1/ receptors labeled by (/sup 3/H)serotonin and that of 5-HT/sub 2/ receptors labeled by (/sup 3/H)spiperone or (/sup 3/H)ketanserin was determined by target size analyses. The values were 57,000 daltons, 145,000 daltons and 152,000 daltons for the cerebral cortex and 56,000 daltons, 141,000 daltons and 150,000 daltons for the striatum, respectively. The estimated sizes were deduced by reference to enzyme standards with known molecular masses and which were irradiated in parallel. These results demonstrate that the molecular entities in situ for 5-HT/sub 1/ receptors are distinct from those for 5-HT/sub 2/ receptors, thus supporting data on the existence of two distinct populations of serotonin receptors, hitherto evidenced physiopharmacologically.

  18. Expression of hippocampal serotonin receptors 5-HT2C and 5-HT5A in a rat model of diet-induced obesity supplemented with tryptophan.

    PubMed

    Lopez-Esparza, Sarahi; Berumen, Laura C; Padilla, Karla; Miledi, Ricardo; García-Alcocer, Guadalupe

    2015-05-01

    Food intake regulation is a complex mechanism that involves endogenous substances and central nervous system structures like hypothalamus or even hippocampus. The neurotransmitter serotonin is distinguished as food intake mediator; within its multiples receptors, the 5-HT2C type is characterized by its inhibitory appetite action but there is no information about 5-HT5A receptors involvement in obesity disease. It is also unknown if there are any changes in the receptors expression in rats hippocampus with induced obesity during development through a high energy diet (HED) supplemented with tryptophan (W). To appreciate the receptors expression pattern in the hippocampus, obesity was induced to young Sprague Dawley rats through a HED and supplemented with W. Immunocytochemical and western blot techniques were used to study the receptor distribution and quantify the protein expression. The rats with HED diet developed obesity until week 13 of treatment. The 5-HT2C receptor expression decreased in CA1, CA2, CA3 and DG of HED group; and also in CA2, CA3 and DG for HEDW group. The 5-HT5A receptor expression only decreased in DG for HED group. Variations of the two serotonin receptors subtypes support their potential role in obesity. PMID:25720309

  19. Serotonin homeostasis and serotonin receptors as actors of cortical construction: special attention to the 5-HT3A and 5-HT6 receptor subtypes

    PubMed Central

    Vitalis, Tania; Ansorge, Mark S.; Dayer, Alexandre G.

    2013-01-01

    Cortical circuits control higher-order cognitive processes and their function is highly dependent on their structure that emerges during development. The construction of cortical circuits involves the coordinated interplay between different types of cellular processes such as proliferation, migration, and differentiation of neural and glial cell subtypes. Among the multiple factors that regulate the assembly of cortical circuits, 5-HT is an important developmental signal that impacts on a broad diversity of cellular processes. 5-HT is detected at the onset of embryonic telencephalic formation and a variety of serotonergic receptors are dynamically expressed in the embryonic developing cortex in a region and cell-type specific manner. Among these receptors, the ionotropic 5-HT3A receptor and the metabotropic 5-HT6 receptor have recently been identified as novel serotonergic targets regulating different aspects of cortical construction including neuronal migration and dendritic differentiation. In this review, we focus on the developmental impact of serotonergic systems on the construction of cortical circuits and discuss their potential role in programming risk for human psychiatric disorders. PMID:23801939

  20. Identification of ginsenoside interaction sites in 5-HT3A receptors.

    PubMed

    Lee, Byung-Hwan; Lee, Jun-Ho; Lee, Sang-Mok; Jeong, Sang Min; Yoon, In-Soo; Lee, Joon-Hee; Choi, Sun-Hye; Pyo, Mi Kyung; Rhim, Hyewhon; Kim, Hyoung-Chun; Jang, Choon-Gon; Lee, Byoung-Cheol; Park, Chul-Seung; Nah, Seung-Yeol

    2007-03-01

    We previously demonstrated that 20(S)-ginsenoside Rg(3) (Rg(3)), one of the active components of Panax ginseng, non-competitively inhibits 5-HT(3A) receptor channel activity on extracellular side of the cell. Here, we sought to elucidate the molecular mechanisms underlying Rg(3)-induced 5-HT(3A) receptor regulation. We used the two-microelectrode voltage-clamp technique to investigate the effect of Rg(3) on 5-HT-mediated ion currents (I(5-HT)) in Xenopus oocytes expressing wild-type or 5-HT(3A) receptors harboring mutations in the gating pore region of transmembrane domain 2 (TM2). In oocytes expressing wild-type 5-HT(3A) receptors, Rg(3) dose-dependently inhibited peak I(5-HT) with an IC(50) of 27.6+/-4.3microM. Mutations V291A, F292A, and I295A in TM2 greatly attenuated or abolished the Rg(3)-induced inhibition of peak I(5-HT). Mutation V291A but not F292A and I295A induced constitutively active ion currents with decrease of current decay rate. Rg(3) accelerated the rate of current decay with dose-dependent manner in the presence of 5-HT. Rg(3) and TMB-8, an open channel blocker, dose-dependently inhibited constitutively active ion currents. The IC(50) values of constitutively active ion currents in V291A mutant receptor were 72.4+/-23.1 and 6.5+/-0.7microM for Rg(3) and TMB-8, respectively. Diltiazem did not prevent Rg(3)-induced inhibition of constitutively active ion currents in occlusion experiments. These results indicate that Rg(3) inhibits 5-HT(3A) receptor channel activity through interactions with residues V291, F292, and I295 in the channel gating region of TM2 and further demonstrate that Rg(3) regulates 5-HT(3A) receptor channel activity in the open state at different site(s) from those of TMB-8 and diltiazem. PMID:17257631

  1. Memory formation, amnesia, improved memory and reversed amnesia: 5-HT role.

    PubMed

    Perez-Garcia, G; Meneses, A

    2008-12-16

    Traditionally, the search for memory circuits has been focused on examinations of amnesic and AD patients, cerebral lesions and neuroimaging. A complementary alternative has become the use of autoradiography with radioligands, aiming to identify neurobiological markers associated with memory formation, amnesia states and (more recently) recovery from memory deficits. Indeed, ex vivo autoradiographic studies offer the advantage of detecting functionally active receptors altered by pharmacological tools during memory formation, amnesia states and memory recovery. Moreover, serotonin (5-hydroxytryptamine, 5-HT) systems have become a pharmacological and genetic target in the treatment of memory disorders. Herein evidence from studies involving expression of 5-HT(1A), 5-HT(2A), 5-HT(4), and 5-HT(6) receptors in memory formation, amnesia conditions (e.g., pharmacological models or aging) and recovery of memory is reviewed. Thus, specific 5-HT receptors were expressed in trained animals relative to untrained in brain areas such as cortex, hippocampus and amygdala. However, relative to the control group, rats showing amnesia or recovered memory, showed in the hippocampus, region where explicit memory is formed, a complex pattern of 5-HT receptor expression. An intermediate expression occurred in amygdala, septum and some cortical areas in charge of explicit memory storage. Even in brain areas thought to be in charge of procedural memory such as basal ganglia, animals showing recovered memory displayed an intermediate expression, while amnesic groups, depending on the pharmacological amnesia model, showed up- or down-regulation. In conclusion, evidence indicates that autoradiography, by using specific radioligands, offers excellent opportunities to map dynamic changes in brain areas engaged in these cognitive processes. The 5-HT modulatory role strengthens or suppresses memory is critically depend on the timing of the memory formation. PMID:18221797

  2. The function of 5-HT3 receptors on colonic transit in rats.

    PubMed

    Haga, K; Asano, K; Fukuda, T; Kobayakawa, T

    1995-12-01

    The function of serotonin (5-HT)3 receptors on colonic transit was investigated in unanesthetized rats. The colonic transit was accelerated by 5-HT (10 mg/kg, s.c.), 2-methyl-5-HT (30 mg/kg, s.c.), neostigmine (0.03-0.1 mg/kg, s.c.), corticotropin releasing factor (CRF; 1 microgram intracerebroventricular administration) and restraint stress (for 45 minutes). A potent and selective 5-HT3 receptor antagonist, azasetron (+/-)-N-(1-azabicyclo[2.2.2]oct-3-yl)-6-chloro- 4-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-8-carboxamide monohydrochloride ; 0.01-10 mg/kg, p.o. inhibited the 5-HT-, CRF- and stress-accelerated colonic transit in a dose-dependent manner. Ondansetron (10 mg/kg, p.o.) and granisetron (1 mg/kg, p.o) also inhibited the stress-accelerated colonic transit, but azasetron was more effective than these two drugs. Atropine methylbromide (0.1 mg/kg, s.c.) and tetrodotoxin (0.01 mg/kg, s.c.) inhibited the accelerated colonic transit under stress conditions, but methysergide (10 mg/kg, s.c.), SDZ205-557 (10 mg/kg, s.c.), domperidone (30 mg/kg, p.o.), trimebutine (300 mg/kg, p.o.), did not. Azasetron (10 micrograms) administered intracerebroventricularly did not inhibit the stress-induced acceleration. These results suggest that endogenous 5-HT which is released through stress accelerates the colonic transit via the 5-HT3 receptors and finally a cholinergic mechanism. It is considered that azasetron inhibits colonic transit particularly under stress conditions through the blockade of the peripheral 5-HT3 receptors. Azasetron may improve bowel function in stress-related colonic dysfunction like irritable bowel syndrome. PMID:8653566

  3. 5-HT6 Receptor Antagonists: Potential Efficacy for the Treatment of Cognitive Impairment in Schizophrenia.

    PubMed

    de Bruin, Natasja M W J; Kruse, Chris G

    2015-01-01

    5-hydroxytryptamine6 receptor (5-HT6R) antagonists have shown efficacy in animal models for cognitive impairment in multiple cognitive domains relevant for schizophrenia. Improvements were found with 5-HT6R antagonists in preclinical tests for episodic memory, social cognition, executive function, working memory and several other tests for both learning and memory. In contrast, there is little evidence for efficacy on attention. It will be interesting to further investigate 5-HT6R antagonists in neurodevelopmental animal models which are based on prenatal exposure to specific environmental insults, and are characterized by a high level of face, construct and predictive validity for cognitive impairments associated with schizophrenia. It is also important to do more add-on preclinical studies of 5-HT6 antagonists with antipsychotics. Possible mechanisms of action to improve cognition have been described. 5-HT6R antagonists decrease GABA release and GABAergic interneuron excitability, which subsequently disinhibits glutamate and/or acetylcholine release and results in enhancement of synaptic plasticity. Furthermore, cognition could be improved by 5-HT6R antagonists, because these compounds increase the number of NCAM PSA-immunoreactive neurons in the dendate gyrus, inhibit mTOR and Fyn-tyrosine kinase and interact with DARPP-32. Interestingly, there is increasing preclinical evidence that could support additional benefits of 5-HT6R ligandson comorbid conditions in schizophrenia such as drug abuse, depression, anxiety, obesity andantipsychotic-induced EPS. Finally, we briefly give an overview of the 5-HT6R compounds that are currently in clinical development for the treatment of cognitive impairment in both schizophrenia and Alzheimer's disease. PMID:26044973

  4. 5-HT3 receptors as important mediators of nausea and vomiting due to chemotherapy.

    PubMed

    Navari, Rudolph M

    2015-10-01

    Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles, and patient risk factors significantly influence CINV. The use of a combination of a 5-hydroxytryptamine-3 (5-HT3) receptor antagonist, dexamethasone, and a neurokinin-1 (NK-1) receptor antagonist has significantly improved the control of acute and delayed emesis in single-day chemotherapy. The first generation 5-HT3 receptor antagonists have been very effective in the control of chemotherapy induced emesis in the first 24 h postchemotherapy (acute emesis), but have not been as effective against delayed emesis (24-120 h postchemotherapy). Palonosetron, a second generation 5-HT3 receptor antagonist with a different half-life, a different binding capacity, and a different mechanism of action than the first generation 5-HT3 receptor antagonists appears to be the most effective agent in its class. Despite the control of emesis, nausea has not been well controlled by current agents. Olanzapine, a FDA approved antipsychotic that blocks multiple neurotransmitters: dopamine at D1, D2, D3, D4 brain receptors, serotonin at 5-HT2a, 5-HT2c, 5-HT3, 5-HT6 receptors, catecholamines at alpha1 adrenergic receptors, acetylcholine at muscarinic receptors, and histamine at H1 receptors, has emerged in recent trials as an effective preventative agent for chemotherapy-induced emesis and nausea, as well as a very effective agent for the treatment of breakthrough emesis and nausea. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers. PMID:25838122

  5. Anxiolytic effects of prelimbic 5-HT(1A) receptor activation in the hemiparkinsonian rat.

    PubMed

    Hui, Yan Ping; Wang, Tao; Han, Ling Na; Li, Li Bo; Sun, Yi Na; Liu, Jian; Qiao, Hong Fei; Zhang, Qiao Jun

    2015-01-15

    This study sought to assess whether unilateral lesions of the medial forebrain bundle (MFB) using 6-hydroxydopamine in rats are able to induce anxiety-like behaviors, the role of serotonin-1A (5-HT1A) receptors of the prelimbic (PrL) sub-region of ventral medial prefrontal cortex in the regulation of these behaviors, the density of 5-HT neurons in the dorsal raphe nucleus (DRN) and co-localization of 5-HT1A receptor and neuronal glutamate transporter EAAC1-immunoreactive (EAAC1-ir) cells in the PrL. Unilaterally lesioning the MFB induced anxiety-like behaviors as measured by the open-field and elevated plus maze tests when compared to sham-operated rats. Intra-PrL injection of 5-HT1A receptor agonist 8-OH-DPAT (50, 100, and 500 ng/rat) decreased the percentage of time spent in the center of the open-field and percentages of open arm entries and open arm time in sham-operated rats, indicating the induction of anxiogenic responses, and administration of 5-HT1A receptor antagonist WAY-100635 (60, 120, and 240 ng/rat) showed anxiolytic effects. However, 8-OH-DPAT, at the same doses, increased the percentage of time spent in the center of the open-field and percentages of open arm entries and open arm time in the lesioned rats, indicating the induction of anxiolytic effects, and WAY-100635 produced anxiogenic responses. Unilateral MFB lesion decreased the density of 5-HT neurons in the DRN, and percentage of EAAC1-ir cells expressing 5-HT1A receptors in the PrL. These results suggest that unilateral lesions of the MFB in rats may induce anxiety-like behaviors, and activation of 5-HT1A receptors in the PrL has anxiolytic effects in the rat model of Parkinson's disease. PMID:24906197

  6. The 5-HT and alpha-adrenoceptor antagonist effect of four benzylisoquinoline alkaloids on rat aorta.

    PubMed

    Catret, M; Ivorra, M D; D'Ocón, M P; Anselmi, E

    1998-03-01

    The action of four benzylisoquinoline alkaloids (two aporphines-glaucine and apomorphine, a benzylisoquinoline-papaverine and a bisbenzyltetrahydroisoquinoline-antioquine) on 5-HT-induced contraction in rat thoracic aorta has been examined and compared with that of the control drugs: ketanserin, nifedipine, prazosin and phentolamine. The relaxant action on 5-HT-induced contraction was contrasted with that on the contraction induced by noradrenaline and KCl. The results obtained with control drugs show that ketanserin has clear selectivity for 5-HT receptors, whereas prazosin and phentolamine have high selectivity for the alpha1-adrenoceptor and nifedipine seems to have a more potent effect on KCl-induced contraction than on that induced by 5-HT or noradrenaline. The contraction evoked by 5-HT (10 microM) was inhibited in a concentration-dependent manner by all the alkaloids. The order of potency was: papaverine = glaucine > apomorphine > antioquine. Papaverine had a non-specific relaxant action on 5-HT-, noradrenaline- and KCl-induced contraction, antioquine had a weak relaxant action on the agonist assays, and glaucine and apomorphine inhibited noradrenaline- and 5-HT-induced contraction more potently than they inhibited the K+-depolarized response. These results indicate that the aporphines assayed, S-glaucine and R-aporphine, had selective action against agonist (noradrenaline or 5-HT)-induced contraction rather than against KCl-depolarization of rat aorta. In contrast papaverine, a benzylisoquinoline alkaloid, relaxes all agents used non-selectively as could be expected from the lack of specificity that characterizes this alkaloid. PMID:9600725

  7. High yield and efficient expression and purification of the human 5-HT3A receptor

    PubMed Central

    Wu, Zhong-shan; Cui, Zhi-cheng; Cheng, Hao; Fan, Chen; Melcher, Karsten; Jiang, Yi; Zhang, Cheng-hai; Jiang, Hua-liang; Cong, Yao; Liu, Qian; Xu, H Eric

    2015-01-01

    Aim: To establish a method for efficient expression and purification of the human serotonin type 3A receptor (5-HT3A) that is suitable for structural studies. Methods: Codon-optimized cDNA of human 5-HT3A was inserted into a modified BacMam vector, which contained an IgG leader sequence, an 8×His tag linked with two-Maltose Binding Proteins (MBP), and a TEV protease cleavage site. The BacMam construct was used to generate baculoviruses for expression of 5-HT3A in HEK293F cells. The proteins were solubilized from the membrane with the detergent C12E 9, and purified using MBP affinity chromatography. The affinity tag was removed by TEV protease treatment and immobilized metal ion affinity chromatography. The receptors were further purified by size-exclusion chromatography (SEC). Western blot and SDS-PAGE were used to detect 5-HT3A during purification. The purified receptor was used in crystallization and analyzed with negative stain electron microscopy (EM). Results: The BacMam system yielded 0.5 milligram of the human 5-HT3A receptor per liter of cells. MBP affinity purification resulted in good yields with high purity and homogeneity. SEC profiles indicated that the purified receptors were pentameric. No protein crystals were obtained; however, a reconstructed 3D density map generated from the negative stain EM data fitted well with the mouse 5-HT3A structure. Conclusion: With the BacMam system, robust expression of the human 5-HT3A receptor is obtained, which is monodisperse, therefore enabling 3D reconstruction of an EM map. This method is suitable for high-throughput screening of different constructs, thus facilitating structural and biochemical studies of the 5-HT3A receptor. PMID:26073329

  8. PET imaging of the serotonin transporter and 5HT1A receptor in alcohol dependence

    PubMed Central

    Martinez, Diana; Slifstein, Mark; Gil, Roberto; Hwang, Dah-Ren; Huang, Yiyun; Perez, Audrey; Frankle, W. Gordon; Laruelle, Marc; Krystal, John; Abi-Dargham, Anissa

    2009-01-01

    Background Rodent models as well as studies in humans have suggested alterations in serotonin (5HT) innervation and transmission in early onset genetically determined or type II alcoholism. This study examines two indices of serotonergic transmission, 5HT transporter levels and 5-HT1A availability, in vivo, in type II alcoholism. This is the first report of combined tracers for pre and post-synaptic serotonergic transmission in the same alcoholic subjects and the first study of 5HT1A receptors in alcoholism. Method Fourteen alcohol dependent subjects were scanned (11 with both tracers, 1 with [11C]DASB only and two with [11C]WAY100635 only). Twelve healthy controls (HC) subjects were scanned with [11C]DASB and another 13 were scanned with [11C]WAY100635. Binding Potential (BPp, mL/cm3) and the specific to nonspecific partition coefficient (BPND, unitless) were derived for both tracers using 2 tissue compartment model and compared to HC across different brain regions. Relationships to severity of alcoholism were assessed. Results No significant differences were observed in regional BPp or BPND between patients and controls in any of the regions examined. No significant relationships were observed between regional 5HT transporter availability, 5-HT1A availability, and disease severity with the exception of a significant negative correlation between SERT and years of dependence in amygdala and insula. Conclusion This study did not find alterations in measures of 5-HT1A or 5HT transporter levels in patients with type II alcoholism. PMID:18962444

  9. Function and Distribution of 5-HT2 Receptors in the Honeybee (Apis mellifera)

    PubMed Central

    Thamm, Markus; Rolke, Daniel; Jordan, Nadine; Balfanz, Sabine; Schiffer, Christian; Baumann, Arnd; Blenau, Wolfgang

    2013-01-01

    Background Serotonin plays a pivotal role in regulating and modulating physiological and behavioral processes in both vertebrates and invertebrates. In the honeybee (Apis mellifera), serotonin has been implicated in division of labor, visual processing, and learning processes. Here, we present the cloning, heterologous expression, and detailed functional and pharmacological characterization of two honeybee 5-HT2 receptors. Methods Honeybee 5-HT2 receptor cDNAs were amplified from brain cDNA. Recombinant cell lines were established constitutively expressing receptor variants. Pharmacological properties of the receptors were investigated by Ca2+ imaging experiments. Quantitative PCR was applied to explore the expression patterns of receptor mRNAs. Results The honeybee 5-HT2 receptor class consists of two subtypes, Am5-HT2α and Am5-HT2β. Each receptor gene also gives rise to alternatively spliced mRNAs that possibly code for truncated receptors. Only activation of the full-length receptors with serotonin caused an increase in the intracellular Ca2+ concentration. The effect was mimicked by the agonists 5-methoxytryptamine and 8-OH-DPAT at low micromolar concentrations. Receptor activities were blocked by established 5-HT receptor antagonists such as clozapine, methiothepin, or mianserin. High transcript numbers were detected in exocrine glands suggesting that 5-HT2 receptors participate in secretory processes in the honeybee. Conclusions This study marks the first molecular and pharmacological characterization of two 5-HT2 receptor subtypes in the same insect species. The results presented should facilitate further attempts to unravel central and peripheral effects of serotonin mediated by these receptors. PMID:24324783

  10. Selective 5-HT2C receptor agonists: Design and synthesis of pyridazine-fused azepines.

    PubMed

    Green, Martin P; McMurray, Gordon; Storer, R Ian

    2016-08-15

    Heterocycle-fused azepines are discussed as potent 5-HT2C receptor agonists with excellent selectivity over 5-HT2B agonism. Synthesis and structure activity relationships are outlined for a series of bicyclic pyridazino[3,4-d]azepines. By comparison with earlier published work, in vitro assays predict a high probability for achieving CNS penetration for a potent and selective compound 15a, a pre-requisite to achieve in vivo efficacy. PMID:27381086

  11. Impaired Social Behavior in 5-HT3A Receptor Knockout Mice

    PubMed Central

    Smit-Rigter, Laura A.; Wadman, Wytse J.; van Hooft, Johannes A.

    2010-01-01

    The 5-HT3 receptor is a ligand-gated ion channel expressed on interneurons throughout the brain. So far, analysis of the 5-HT3A knockout mouse revealed changes in nociceptive processing and a reduction in anxiety related behavior. Recently, it was shown that the 5-HT3 receptor is also expressed on Cajal-Retzius cells which play a key role in cortical development and that knockout mice lacking this receptor showed aberrant growth of the dendritic tree of cortical layer II/III pyramidal neurons. Other mouse models in which serotonergic signaling was disrupted during development showed similar morphological changes in the cortex, and in addition, also deficits in social behavior. Here, we subjected male and female 5-HT3A knockout mice and their non-transgenic littermates to several tests of social behavior. We found that 5-HT3A knockout mice display impaired social communication in the social transmission of food preference task. Interestingly, we showed that in the social interaction test only female 5-HT3A knockout mice spent less time in reciprocal social interaction starting after 5 min of testing. Moreover, we observed differences in preference for social novelty for male and female 5-HT3A knockout mice during the social approach test. However, no changes in olfaction, exploratory activity and anxiety were detected. These results indicate that the 5-HT3A knockout mouse displays impaired social behavior with specific changes in males and females, reminiscent to other mouse models in which serotonergic signaling is disturbed in the developing brain. PMID:21103015

  12. Potentiation of 5-methoxy-N,N-dimethyltryptamine-induced hyperthermia by harmaline and the involvement of activation of 5-HT1A and 5-HT2A receptors.

    PubMed

    Jiang, Xi-Ling; Shen, Hong-Wu; Yu, Ai-Ming

    2015-02-01

    5-Methoxy-N,N-dimethyltryptamine (5-MeO-DMT) and harmaline are serotonin (5-HT) analogs often abused together, which alters thermoregulation that may indicate the severity of serotonin toxicity. Our recent studies have revealed that co-administration of monoamine oxidase inhibitor harmaline leads to greater and prolonged exposure to 5-HT agonist 5-MeO-DMT that might be influenced by cytochrome P450 2D6 (CYP2D6) status. This study was to define the effects of harmaline and 5-MeO-DMT on thermoregulation in wild-type and CYP2D6-humanized (Tg-CYP2D6) mice, as well as the involvement of 5-HT receptors. Animal core body temperatures were monitored noninvasively in the home cages after implantation of telemetry transmitters and administration of drugs. Harmaline (5 and 15 mg/kg, i.p.) alone was shown to induce hypothermia that was significantly affected by CYP2D6 status. In contrast, higher doses of 5-MeO-DMT (10 and 20 mg/kg) alone caused hyperthermia. Co-administration of harmaline (2, 5 or 15 mg/kg) remarkably potentiated the hyperthermia elicited by 5-MeO-DMT (2 or 10 mg/kg), which might be influenced by CYP2D6 status at certain dose combination. Interestingly, harmaline-induced hypothermia was only attenuated by 5-HT1A receptor antagonist WAY-100635, whereas 5-MeO-DMT- and harmaline-5-MeO-DMT-induced hyperthermia could be suppressed by either WAY-100635 or 5-HT2A receptor antagonists (MDL-100907 and ketanserin). Moreover, stress-induced hyperthermia under home cage conditions was not affected by WAY-100635 but surprisingly attenuated by MDL-100907 and ketanserin. Our results indicate that co-administration of monoamine oxidase inhibitor largely potentiates 5-MeO-DMT-induced hyperthermia that involves the activation of both 5-HT1A and 5-HT2A receptors. These findings shall provide insights into development of anxiolytic drugs and new strategies to relieve the lethal hyperthermia in serotonin toxicity. PMID:25446678

  13. Potentiation of 5-methoxy-N,N-dimethyltryptamine-induced hyperthermia by harmaline and the involvement of activation of 5-HT1A and 5-HT2A receptors

    PubMed Central

    Jiang, Xi-Ling; Shen, Hong-Wu; Yu, Ai-Ming

    2014-01-01

    5-Methoxy-N,N-dimethyltryptamine (5-MeO-DMT) and harmaline are serotonin (5-HT) analogs often abused together, which alters thermoregulation that may indicate the severity of serotonin toxicity. Our recent studies have revealed that co-administration of monoamine oxidase inhibitor harmaline leads to greater and prolonged exposure to 5-HT agonist 5-MeO-DMT that might be influenced by cytochrome P450 2D6 (CYP2D6) status. This study was to define the effects of harmaline and 5-MeO-DMT on thermoregulation in wild-type and CYP2D6-humanized (Tg-CYP2D6) mice, as well as the involvement of 5-HT receptors. Animal core body temperatures were monitored noninvasively in the home cages after implantation of telemetry transmitters and administration of drugs. Harmaline (5 and 15 mg/kg, i.p.) alone was shown to induce hypothermia that was significantly affected by CYP2D6 status. In contrast, higher doses of 5-MeO-DMT (10 and 20 mg/kg) alone caused hyperthermia. Co-administration of harmaline (2, 5 or 15 mg/kg) remarkably potentiated the hyperthermia elicited by 5-MeO-DMT (2 or 10 mg/kg), which might be influenced by CYP2D6 status at certain dose combination. Interestingly, harmaline-induced hypothermia was only attenuated by 5-HT1A receptor antagonist WAY-100635, whereas 5-MeO-DMT- and harmaline-5-MeO-DMT-induced hyperthermia could be suppressed by either WAY-100635 or 5-HT2A receptor antagonists (MDL-100907 and ketanserin). Moreover, stress-induced hyperthermia under home cage conditions was not affected by WAY-100635 but surprisingly attenuated by MDL-100907 and ketanserin. Our results indicate that co-administration of monoamine oxidase inhibitor largely potentiates 5-MeO-DMT-induced hyperthermia that involves the activation of both 5-HT1A and 5-HT2A receptors. These findings shall provide insights into development of anxiolytic drugs and new strategies to relieve the lethal hyperthermia in serotonin toxicity. PMID:25446678

  14. Serotonin decreases aggression via 5-HT1A receptors in the fighting fish Betta splendens.

    PubMed

    Clotfelter, Ethan D; O'Hare, Erin P; McNitt, Meredith M; Carpenter, Russ E; Summers, Cliff H

    2007-01-01

    The role of the monoamine neurotransmitter serotonin (5-HT) in the modulation of conspecific aggression in the fighting fish (Betta splendens) was investigated using pharmacological manipulations. We used a fish's response to its mirror image as our index of aggressive behavior. We also investigated the effects of some manipulations on monoamine levels in the B. splendens brain. Acute treatment with 5-HT and with the 5-HT1A receptor agonist 8-OH-DPAT both decreased aggressive behavior; however, treatment with the 5-HT1A receptor antagonist WAY-100635 did not increase aggression. Chronic treatment with the selective serotonin reuptake inhibitor fluoxetine caused no significant changes in aggressive behavior and a significant decline in 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) concentrations. Treatment with the serotonin synthesis inhibitor p-chlorophenylalanine resulted in no change in aggression, yet serotonergic activity decreased significantly. Finally, a diet supplemented with L-tryptophan (Trp), the precursor to 5-HT, showed no consistent effects on aggressive behavior or brain monoamine concentrations. These results suggest a complex role for serotonin in the expression of aggression in teleost fishes, and that B. splendens may be a useful model organism in pharmacological and toxicological studies. PMID:17553555

  15. 5-HT2B Receptor Antagonists Inhibit Fibrosis and Protect from RV Heart Failure

    PubMed Central

    Janssen, Wiebke; Schymura, Yves; Novoyatleva, Tatyana; Luitel, Himal; Tretyn, Aleksandra; Pullamsetti, Soni Savai; Weissmann, Norbert; Seeger, Werner; Ghofrani, Hossein Ardeschir; Schermuly, Ralph Theo

    2015-01-01

    Objective. The serotonin (5-HT) pathway was shown to play a role in pulmonary hypertension (PH), but its functions in right ventricular failure (RVF) remain poorly understood. The aim of the current study was to investigate the effects of Terguride (5-HT2A and 2B receptor antagonist) or SB204741 (5-HT2B receptor antagonist) on right heart function and structure upon pulmonary artery banding (PAB) in mice. Methods. Seven days after PAB, mice were treated for 14 days with Terguride (0.2 mg/kg bid) or SB204741 (5 mg/kg day). Right heart function and remodeling were assessed by right heart catheterization, magnetic resonance imaging (MRI), and histomorphometric methods. Total secreted collagen content was determined in mouse cardiac fibroblasts isolated from RV tissues. Results. Chronic treatment with Terguride or SB204741 reduced right ventricular fibrosis and showed improved heart function in mice after PAB. Moreover, 5-HT2B receptor antagonists diminished TGF-beta1 induced collagen synthesis of RV cardiac fibroblasts in vitro. Conclusion. 5-HT2B receptor antagonists reduce collagen deposition, thereby inhibiting right ventricular fibrosis. Chronic treatment prevented the development and progression of pressure overload-induced RVF in mice. Thus, 5-HT2B receptor antagonists represent a valuable novel therapeutic approach for RVF. PMID:25667920

  16. The 5-HT2A serotonin receptor in executive function: Implications for neuropsychiatric and neurodegenerative diseases.

    PubMed

    Aznar, Susana; Hervig, Mona El-Sayed

    2016-05-01

    Executive function entails the interplay of a group of cognitive processes enabling the individual to anticipate consequences, attain self-control, and undertake appropriate goal-directed behaviour. Serotonin signalling at serotonin 2A receptors (5-HT2AR) has important effects on these behavioural and cognitive pathways, with the prefrontal cortex (PFC) as the central actor. Indeed, the 5-HT2ARs are highly expressed in PFC, where they modulate cortical activity and local network oscillations (brain waves). Numerous psychiatric and neurodegenerative diseases result in disrupted executive function. Animal and human studies have linked these disorders with alterations in the 5-HT2AR system, making this an important pharmacological target for the treatment of disorders with impaired cognitive function. This review aims to describe the current state of knowledge on the role of 5-HT2AR signalling in components of executive function, and how 5-HT2AR systems may relate to executive dysfunctions occurring in psychiatric and neurodegenerative diseases. We hope thereby to provide insight into how pharmacotherapy targeting the 5-HT2AR may ameliorate (or exacerbate) aspects of these disorders. PMID:26891819

  17. 5-HT1A autoreceptor levels determine vulnerability to stress and response to antidepressants

    PubMed Central

    Richardson-Jones, Jesse W; Craige, Caryne P; Guiard, Bruno P; Stephen, Alisson; Metzger, Kayla L; Kung, Hank F; Gardier, Alain M; Dranovsky, Alex; David, Denis J; Beck, Sheryl G; Hen, René; Leonardo, E David

    2010-01-01

    Summary Most depressed patients don't respond to their first drug treatment, and the reasons for this treatment resistance remain enigmatic. Human studies implicate a polymorphism in the promoter of the serotonin-1A (5-HT1A) receptor gene in increased susceptibility to depression and decreased treatment response. Here we develop a new strategy to manipulate 5-HT1A autoreceptors in raphe nuclei without affecting 5-HT1A heteroreceptors, generating mice with higher (1A-High) or lower (1A-Low) autoreceptor levels. We show that this robustly affects raphe firing rates, but has no effect on either basal forebrain serotonin levels or conflict-anxiety measures. However, compared to 1A-Low mice, 1A-High mice show a blunted physiological response to acute stress, increased behavioral despair, and no behavioral response to antidepressant, modeling patients with the 5-HT1A risk allele. Furthermore, reducing 5-HT1A autoreceptor levels prior to antidepressant treatment is sufficient to convert non-responders into responders. These results establish a causal relationship between 5-HT1A autoreceptor levels, resilience under stress, and response to antidepressants. PMID:20152112

  18. Optimising PET approaches to measuring 5-HT release in human brain.

    PubMed

    Tyacke, Robin J; Nutt, David J

    2015-10-01

    A major goal in neuroscience is the measurement of neurotransmitters in living human brain. To date this has only been done reliably with dopamine using certain PET and SPECT radiotracers. The use of this technique has greatly advanced our understanding of dopamine and the dopaminergic system in normal and abnormal brain function. Transferring this technology to other neurotransmitter systems has proved less fruitful. The serotonergic system (5-HT) is one such system. 5-HT has been implicated in a wide range of brain functions and their disorders. The ability to measure 5-HT using this technique would be invaluable. In this article, we explore the key pharmacological features of current radiotracers for 5-HT receptors that might be sensitive to endogenous 5-HT. We also estimate the likely brain concentrations of the current available tranche of agents that might be used to enhance synaptic 5-HT concentration, so taking into account the potential for these to interact with the receptors directly and produce a spurious displacement signal. PMID:26089243

  19. Heart rate within male crayfish: social interactions and effects of 5-HT.

    PubMed

    Listerman, L R; Deskins, J; Bradacs, H; Cooper, R L

    2000-02-01

    Behaviors, such as those that establish dominant and subordinate social status, are thought to be driven by various neuromodulators and hormones. In crustaceans, the level of serotonin (5-HT) in the hemolymph is correlated with degree of aggressiveness. The crustacean heart is neurogenic and is modulated by neural secretion of 5-HT in the hemolymph, which bathes the cardiac tissue. We discuss and present the results of measuring heart rate (HR) of crayfish during interactions, as an indication of their state of excitability. HR is the result of multiple influences: a cocktail of hormones and modulators. HR was monitored during the periods in which crayfish established aggressive and submissive social status, during sham injections, and following injections of various doses of 5-HT. Crayfish, during an interaction to establish social status, can increase HR. Both the aggressive and submissive crayfish can dampen their HR within seconds during a pause in the interaction, while still posturing in an aggressive or submissive state. Injections of 5-HT to obtain systemic levels of approximately 100 nM-10 microM increase HR substantially for hours. This suggests that aggressive interactions and the establishment of a dominant posture may not be related to large increases in the free concentrations of 5-HT within the circulating hemolymph, since a sustained HR is not observed in aggressive animals. Instead, the results may demonstrate that inhibitory cardiac regulation is present in the aggressors during interactions and that a regulator is possibly 5-HT. PMID:10825697

  20. Sensitivity of transformed (phasic to tonic) motor neurons to the neuromodulator 5-HT.

    PubMed

    Griffis, B; Bonner, P; Cooper, R L

    2000-12-01

    Long-term adaptation resulting in a 'tonic-like' state can be induced in phasic motor neurons of the crayfish, Procambarus clarkii, by daily low-frequency stimulation [Lnenicka, G.A., Atwood, H.L., 1985b. Long-term facilitation and long-term adaptation at synapses of a crayfish phasic motoneuron. J. Neurobiol. 16, 97-110]. To test the hypothesis that motor neurons undergoing adaptation show increased responses to the neuromodulator serotonin (5-HT), phasic motor neurons innervating the deep abdominal extensor muscles of crayfish were stimulated at 2.5 Hz, 2 h/day, for 7 days. One day after cessation of conditioning, contralateral control and conditioned motor neurons of the same segment were stimulated at 1 Hz and the induced excitatory post-synaptic potentials (EPSPs) were recorded from DEL(1) muscle fibers innervated by each motor neuron type. Recordings were made in saline without and with 100 nM 5-HT. EPSP amplitudes were increased by 5-HT exposure in all cases. Conditioned muscles exposed to 5-HT showed a 2-fold higher percentage of increase in EPSP amplitude than did control muscles. Thus, the conditioned motor neurons behaved like intrinsically tonic motoneurons in their response to 5-HT. While these results show that long-term adaptation (LTA) extends to 5-HT neuromodulation, no phenotype switch could be detected in the postsynaptic muscle. Protein isoform profiles, including the myosin heavy chains, do not change after 1 week of conditioning their innervating motor neurons. PMID:11154946

  1. Cannabidiol induces rapid-acting antidepressant-like effects and enhances cortical 5-HT/glutamate neurotransmission: role of 5-HT1A receptors.

    PubMed

    Linge, Raquel; Jiménez-Sánchez, Laura; Campa, Leticia; Pilar-Cuéllar, Fuencisla; Vidal, Rebeca; Pazos, Angel; Adell, Albert; Díaz, Álvaro

    2016-04-01

    Cannabidiol (CBD), the main non-psychotomimetic component of marihuana, exhibits anxiolytic-like properties in many behavioural tests, although its potential for treating major depression has been poorly explored. Moreover, the mechanism of action of CBD remains unclear. Herein, we have evaluated the effects of CBD following acute and chronic administration in the olfactory bulbectomy mouse model of depression (OBX), and investigated the underlying mechanism. For this purpose, we conducted behavioural (open field and sucrose preference tests) and neurochemical (microdialysis and autoradiography of 5-HT1A receptor functionality) studies following treatment with CBD. We also assayed the pharmacological antagonism of the effects of CBD to dissect out the mechanism of action. Our results demonstrate that CBD exerts fast and maintained antidepressant-like effects as evidenced by the reversal of the OBX-induced hyperactivity and anhedonia. In vivo microdialysis revealed that the administration of CBD significantly enhanced serotonin and glutamate levels in vmPFCx in a different manner depending on the emotional state and the duration of the treatment. The potentiating effect upon neurotransmitters levels occurring immediately after the first injection of CBD might underlie the fast antidepressant-like actions in OBX mice. Both antidepressant-like effect and enhanced cortical 5-HT/glutamate neurotransmission induced by CBD were prevented by 5-HT1A receptor blockade. Moreover, adaptive changes in pre- and post-synaptic 5-HT1A receptor functionality were also found after chronic CBD. In conclusion, our findings indicate that CBD could represent a novel fast antidepressant drug, via enhancing both serotonergic and glutamate cortical signalling through a 5-HT1A receptor-dependent mechanism. PMID:26711860

  2. 5-HT loss in rat brain following 3,4-methylenedioxymethamphetamine (MDMA), p-chloroamphetamine and fenfluramine administration and effects of chlormethiazole and dizocilpine.

    PubMed Central

    Colado, M. I.; Murray, T. K.; Green, A. R.

    1993-01-01

    1. The present study has investigated whether the neurotoxic effects of the relatively selective 5-hydroxytryptamine (5-HT) neurotoxins, 3,4-methylenedioxymethamphetamine (MDMA or 'Ecstasy'), p-chloroamphetamine (PCA) and fenfluramine on hippocampal and cortical 5-HT terminals in rat brain could be prevented by administration of either chlormethiazole or dizocilpine. 2. Administration of MDMA (20 mg kg-1, i.p.) resulted in an approximate 30% loss of cortical and hippocampal 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) content 4 days later. Injection of chlormethiazole (50 mg kg-1) 5 min before and 55 min after the MDMA provided complete protection in both regions, while dizocilpine (1 mg kg-1, i.p.) protected only the hippocampus. 3. Administration of a single dose of chlormethiazole (100 mg kg-1) 20 min after the MDMA also provided complete protection to the hippocampus but not the cortex. This regime also attenuated the sustained hyperthermia (approx +2.5 degrees C) induced by the MDMA injection. 4. Injection of PCA (5 mg kg-1, i.p.) resulted in a 70% loss of 5-HT and 5-HIAA content in hippocampus and cortex 4 days later. Injection of chlormethiazole (100 mg kg-1, i.p.) or dizocilpine (1 mg kg-1, i.p.) 5 min before and 55 min after the PCA failed to protect against the neurotoxicity, nor was protection afforded by chlormethiazole when a lower dose of PCA (2.5 mg kg-1, i.p.) was given which produced only a 30% loss of 5-HT content.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7682129

  3. The role of calcium in depolarization—secretion coupling at the motor nerve terminal

    PubMed Central

    Cooke, J. D.; Okamoto, K.; Quastel, D. M. J.

    1973-01-01

    1. The relation between m.e.p.p. frequency (F) and [Ca] was studied at the mouse neuromuscular junction, at varied concentrations of K+ and at nerve terminals depolarized by focal depolarization. 2. Under all conditions the relation between log F and log [Ca] was sigmoid, with a maximum slope that increased with depolarization or raised [K+]. In addition, depolarization or raised K+ caused a progressive shift of the sigmoid curve upward and to the left (to reduced log [Ca]) and increased the range over which log F could be altered by [Ca]. 3. Reduction of osmotic pressure changed the relation between log F and log [Ca] in the same way as increase of depolarization, while increase of osmotic pressure did the opposite. 4. Raised [Mg] acted in two ways: (a) to shift the curve of log F vs. log [Ca] to the right and (b) to reduce maximum Δ log F/Δ log [Ca] without altering the range of log F sensitive to [Ca]. 5. The relation between log quantal content of e.p.p.s and log [Ca] was similar to that between log m.e.p.p. frequency and log [Ca]. 6. Individual nerve terminals varied in both Ca-dependent and Ca-independent fractions of log F; a large Ca-independent portion appears to be associated with a low Ca-dependent portion and vice versa. With large prolonged depolarization the Ca-independent portion was increased, apparently at the expense of the Ca-dependent portion. 7. The results of all experiments were summarized in terms of parameters found by fitting the observed log release —log [Ca] curves to two theoretical equations, each derived on the basis of a model: (a) all-or-nothing activation of release probability by Ca-complex(es) and (b) graded activation of release probability by Ca complex(es). 8. On the basis of the all-or-nothing model, from which follows alinear relation between F and amounts of Ca complex(es), the number of Ca2+ atoms that `cooperate' to mediate release appeared to increase progressively with presynaptic depolarization, to a value of 4 or

  4. Neuronal Ablation of p-Akt at Ser473 Leads to Altered 5-HT1A/2A Receptor Function

    PubMed Central

    Saunders, Christine; Siuta, Michael; Robertson, Sabrina D.; Davis, Adeola R.; Sauer, Jennifer; Matthies, Heinrich J.G.; Gresch, Paul J.; Airey, David; Lindsley, Craig W.; Schetz, John A.; Niswender, Kevin D.

    2014-01-01

    The serotonergic system regulates a wide range of behavior, including mood and impulsivity, and its dysregulation has been associated with mood disorders, autism spectrum disorder, and addiction. Diabetes is a risk factor for these conditions. Insulin resistance in the brain is specifically associated with susceptibility to psychostimulant abuse. Here, we examined whether phosphorylation of Akt, a key regulator of the insulin signaling pathway, controls serotonin (5-HT) signaling. To explore how impairment in Akt function regulates 5-HT homeostasis, we used a brain-specific rictor knockout (KO) mouse model of impaired neuronal phosphorylation of Akt at Ser473. Cortical 5-HT1A and 5-HT2A receptor binding was significantly elevated in rictor KO mice. Concomitant with this elevated receptor expression, the 5-HT1A receptor agonist 8-Hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) led to an increased hypothermic response in rictor KO mice. The increased cortical 5-HT1A receptor density was associated with higher 5-HT1A receptor levels on the cortical cell surface. In contrast, rictor KO mice displayed significantly reduced head-twitch response (HTR) to the 5-HT2A/C agonist 2,5-dimethoxy-4-iodoamphetamine (DOI), with evidence of impaired 5-HT2A/C receptor signaling. In vitro, pharmacological inhibition of Akt significantly increased 5-HT1A receptor expression and attenuated DOI-induced 5-HT2A receptor signaling, thereby lending credence to the observed in vivo cross-talk between neuronal Akt signaling and 5-HT receptor regulation. These data reveal that defective central Akt function alters 5-HT signaling as well as 5-HT-associated behaviors, demonstrating a novel role for Akt in maintaining neuronal 5-HT receptor function. PMID:24090638

  5. Design, synthesis, and pharmacological evaluation of multitarget-directed ligands with both serotonergic subtype 4 receptor (5-HT4R) partial agonist and 5-HT6R antagonist activities, as potential treatment of Alzheimer's disease.

    PubMed

    Yahiaoui, Samir; Hamidouche, Katia; Ballandonne, Céline; Davis, Audrey; de Oliveira Santos, Jana Sopkova; Freret, Thomas; Boulouard, Michel; Rochais, Christophe; Dallemagne, Patrick

    2016-10-01

    5-HT4 receptor (5-HT4R) activation and blockade of the 5-HT6 receptor (5-HT6R) are known to enhance the release of numerous neurotransmitters whose depletion is implicated in Alzheimer's disease (AD). Furthermore, 5-HT4R agonists seem to favor production of the neurotrophic soluble amyloid protein precursor alpha (sAPPα). Consequently, combining 5-HT4R agonist/5-HT6R antagonist activities in a single chemical compound would constitute a novel approach able to display both a symptomatic and disease-modifying effect in AD. Seventeen novel derivatives of RS67333 (1) were synthesized and evaluated as potential dual-target compounds. Among them, four agents showed nanomolar and submicromolar affinities toward 5-HT4R and 5-HT6R, respectively; one of them, 7m, was selected on the basis of its in vitro affinity (Ki5-HT4R = 5.3 nM, Ki5-HT6R = 219 nM) for further in vivo experiments, where 7m showed an antiamnesic effect in the mouse at 1 mg/kg ip. PMID:27266998

  6. Transmitter release by mammalian motor nerve terminals in response to focal polarization

    PubMed Central

    Cooke, J. D.; Quastel, D. M. J.

    1973-01-01

    1. A method is described by which mammalian motor nerve terminals may be uniformly polarized by focally applied current, and the extra-cellular potential in the synaptic cleft, corresponding to any current, estimated. 2. The relationship between log m.e.p.p. frequency and local extra-cellular field is flat for hyperpolarization and ascends linearly with depolarization. With depolarization, m.e.p.p. frequency is multiplied about tenfold for every — 18 mV. This characteristic becomes steeper the closer the polarizing electrode to the nerve terminal with a limiting value of ten-fold per — 15 mV. 3. There exists a population of small m.e.p.p.s which are generated at the same end-plate as normal m.e.p.p.s. 4. Following a prolonged depolarizing pulse there is an increase of m.e.p.p. frequency which continues for periods of up to several minutes. 5. With hyperpolarizing pulses m.e.p.p. frequency may increase in a characteristic `bursty' manner. Similar bursts of m.e.p.p.s also occur spontaneously, but far less frequently, without polarization. 6. During a depolarizing pulse, m.e.p.p. frequency becomes maximal or near maximal within 2 sec. There is little subsequent alteration of m.e.p.p. frequency. Numbers of m.e.p.p.s occurring during depolarizing pulses follow the Poisson distribution. 7. Following a depolarizing pulse, numbers of m.e.p.p.s released by a subsequent pulse may be either increased or diminished. 8. Comparison of the response of m.e.p.p. frequency to raised [K] and to extrinsic presynaptic polarization leads to the conclusion that the presynaptic transmembrane potential change corresponding to any focal current pulse is about two thirds of the local extracellular potential field. Hence the slope of the linear portion of the presynaptic transfer function is about tenfold per 10 mV presynaptic depolarization. PMID:4346991

  7. Berberine Inhibits the Release of Glutamate in Nerve Terminals from Rat Cerebral Cortex

    PubMed Central

    Lu, Cheng-Wei; Huang, Shu-Kuei; Wang, Su-Jane

    2013-01-01

    Berberine, an isoquinoline plant alkaloid, protects neurons against neurotoxicity. An excessive release of glutamate is considered to be one of the molecular mechanisms of neuronal damage in several neurological diseases. In this study, we investigated whether berberine could affect endogenous glutamate release in nerve terminals of rat cerebral cortex (synaptosomes) and explored the possible mechanism. Berberine inhibited the release of glutamate evoked by the K+ channel blocker 4-aminopyridine (4-AP), and this phenomenon was prevented by the chelating extracellular Ca2+ ions and the vesicular transporter inhibitor bafilomycin A1, but was insensitive to the glutamate transporter inhibitor DL-threo-beta-benzyl-oxyaspartate. Inhibition of glutamate release by berberine was not due to it decreasing synaptosomal excitability, because berberine did not alter 4-AP-mediated depolarization. The inhibitory effect of berberine on glutamate release was associated with a reduction in the depolarization-induced increase in cytosolic free Ca2+ concentration. Involvement of the Cav2.1 (P/Q-type) channels in the berberine action was confirmed by blockade of the berberine-mediated inhibition of glutamate release by the Cav2.1 (P/Q-type) channel blocker ω-agatoxin IVA. In addition, the inhibitory effect of berberine on evoked glutamate release was prevented by the mitogen-activated/extracellular signal-regulated kinase kinase (MEK) inhibitors. Berberine decreased the 4-AP-induced phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) and synapsin I, the main presynaptic target of ERK; this decrease was also blocked by the MEK inhibition. Moreover, the inhibitory effect of berberine on evoked glutamate release was prevented in nerve terminals from mice lacking synapsin I. Together, these results indicated that berberine inhibits glutamate release from rats cortical synaptosomes, through the suppression of presynaptic Cav2.1 channels and ERK/synapsin I signaling

  8. Altered Active Zones, Vesicle Pools, Nerve Terminal Conductivity, and Morphology during Experimental MuSK Myasthenia Gravis

    PubMed Central

    Patel, Vishwendra; Oh, Anne; Voit, Antanina; Sultatos, Lester G.; Babu, Gopal J.; Wilson, Brenda A.; Ho, Mengfei; McArdle, Joseph J.

    2014-01-01

    Recent studies demonstrate reduced motor-nerve function during autoimmune muscle-specific tyrosine kinase (MuSK) myasthenia gravis (MG). To further understand the basis of motor-nerve dysfunction during MuSK-MG, we immunized female C57/B6 mice with purified rat MuSK ectodomain. Nerve-muscle preparations were dissected and neuromuscular junctions (NMJs) studied electrophysiologically, morphologically, and biochemically. While all mice produced antibodies to MuSK, only 40% developed respiratory muscle weakness. In vitro study of respiratory nerve-muscle preparations isolated from these affected mice revealed that 78% of NMJs produced endplate currents (EPCs) with significantly reduced quantal content, although potentiation and depression at 50 Hz remained qualitatively normal. EPC and mEPC amplitude variability indicated significantly reduced number of vesicle-release sites (active zones) and reduced probability of vesicle release. The readily releasable vesicle pool size and the frequency of large amplitude mEPCs also declined. The remaining NMJs had intermittent (4%) or complete (18%) failure of neurotransmitter release in response to 50 Hz nerve stimulation, presumably due to blocked action potential entry into the nerve terminal, which may arise from nerve terminal swelling and thinning. Since MuSK-MG-affected muscles do not express the AChR γ subunit, the observed prolongation of EPC decay time was not due to inactivity-induced expression of embryonic acetylcholine receptor, but rather to reduced catalytic activity of acetylcholinesterase. Muscle protein levels of MuSK did not change. These findings provide novel insight into the pathophysiology of autoimmune MuSK-MG. PMID:25438154

  9. Molecular and behavioral pharmacology of two novel orally-active 5HT2 modulators: potential utility as antipsychotic medications

    PubMed Central

    Morgan, Drake; Kondabolu, Krishnakanth; Kuipers, Allison; Sakhuja, Rajeev; Robertson, Kimberly L.; Rowland, Neil E.; Booth, Raymond G.

    2013-01-01

    Background Desired serotonin 5HT2 receptor pharmacology for treatment of psychoses is 5HT2A antagonism and/or 5HT2C agonism. No selective 5HT2A antagonist has been approved for psychosis and the only approved 5HT2C agonist (for obesity) also activates 5HT2A and 5HT2B receptors, which can lead to clinical complications. Studies herein tested the hypothesis that a dual-function 5HT2A antagonist/5HT2C agonist that does not activate 5HT2B receptors would be suitable for development as an antipsychotic drug, without liability for weight gain. Methods The novel compounds (+)- and (−)-trans-4-(4′-chlorophenyl)-N,N-dimethyl-2-aminotetralin (p-Cl-PAT) were synthesized, characterized in vitro for affinity and functional activity at human 5HT2 receptors, and administered by intraperitoneal (i.p.) and oral (gavage) routes to mice in behavioral paradigms that assessed antipsychotic efficacy and effects on feeding behavior. Results (+)- and (−)-p-Cl-PAT activated 5HT2C receptors, with (+)-p-Cl-PAT being 12-times more potent, consistent with its higher affinity across 5HT2 receptors. Neither p-Cl-PAT enantiomer activated 5HT2A or 5HT2B receptors at concentrations up to 300-times greater than their respective affinity (Ki), and (+)-p-Cl-PAT was shown to be a 5HT2A competitive antagonist. When administered i.p. or orally, (+)- and (−)-p-Cl-PAT attenuated the head-twitch response (HTR) in mice elicited by the 5HT2 agonist (−)-2,5-dimethoxy-4-iodoamphetamine (DOI) and reduced intake of a highly palatable food in non-food-deprived mice, with (+)-p-Cl-PAT being more potent across behavioral assays. Conclusions The novel in vitro pharmacology of (+)-p-Cl-PAT (5HT2A antagonism/5HT2C agonism without activation of 5HT2B) translated in vivo to an orally-active drug candidate with preclinical efficacy to treat psychoses without liability for weight gain. PMID:23665356

  10. A biochemical approach to study sub-second endogenous release of diverse neurotransmitters from central nerve terminals.

    PubMed

    Leenders, A G Miriam; Hengst, Pieter; Lopes da Silva, Fernando H; Ghijsen, Wim E J M

    2002-01-15

    Exocytosis in central nerve terminals is rapidly triggered by the influx of calcium through high voltage sensitive Ca2+ -channels. Mainly due to their small size, studies in which neurotransmitter release from these terminals was determined at the sub-second time-scale are still rather limited. Here we describe the use of a pneumatic rapid mixing device, allowing application of short (> or = 50 ms) K+ -depolarizing pulses to purified nerve terminals, synaptosomes, to trigger endogenous release of different transmitter types. A consistent, Ca2+ -dependent exocytotic release of the amino acid transmitters, glutamate and GABA, from synaptosomes purified from rat and mouse brain was observed after 100 ms depolarization. For determination of amino acid release after longer depolarizations (> 100 ms), transporter blockers had to be added to prevent clearance of the vesicularly released transmitters. Ca2+ -dependent release of the neuropeptide cholecystokinin occured only after 250 ms depolarization. In addition, the time-courses of amino acid and cholecystokinin release were clearly different. The fast Ca2+ -dependent release of all transmitters was selectively and strongly inhibited by the P/Q-type Ca2+ -channel blocker omega-Agatoxin IVA. In conclusion, this approach allows direct measurement of Ca2+ -dependent release of diverse endogenous neurotransmitters from central nerve terminals upon depolarization pulses at a physiologically relevant, sub-second, time scale. PMID:11741718

  11. Memory consolidation and amnesia modify 5-HT6 receptors expression in rat brain: an autoradiographic study.

    PubMed

    Meneses, A; Manuel-Apolinar, L; Castillo, C; Castillo, E

    2007-03-12

    Traditionally, the search for memory circuits has been centered on examinations of amnesic and AD patients, cerebral lesions and, neuroimaging. A complementary alternative might be the use of autoradiography with radioligands. Indeed, ex vivo autoradiographic studies offer the advantage to detect functionally active receptors altered by pharmacological tools and memory formation. Hence, herein the 5-HT(6) receptor antagonist SB-399885 and the amnesic drugs scopolamine or dizocilpine were used to manipulate memory consolidation and 5-HT(6) receptors expression was determined by using [(3)H]-SB-258585. Thus, memory consolidation was impaired in scopolamine and dizocilpine treated groups relative to control vehicle but improved it in SB-399885-treated animals. SB-399885 improved memory consolidation seems to be associated with decreased 5-HT(6) receptors expression in 15 out 17 brain areas. Scopolamine or dizocilpine decreased 5-HT(6) receptors expression in nine different brain areas and increased it in CA3 hippocampus or other eight areas, respectively. In brain areas thought to be in charge of procedural memory such basal ganglia (i.e., nucleus accumbens, caudate putamen, and fundus striate) data showed that relative to control animals amnesic groups showed diminished (scopolamine) or augmented (dizocilpine) 5-HT(6) receptor expression. SB-399885 showing improved memory displayed an intermediate expression in these same brain regions. A similar intermediate expression occurs with regard to amygdala, septum, and some cortical areas in charge of explicit memory storage. However, relative to control group amnesic and SB-399885 rats in the hippocampus, region where explicit memory is formed, showed a complex 5-HT(6) receptors expression. In conclusion, these results indicate neural circuits underlying the effects of 5-HT(6) receptor antagonists in autoshaping task and offer some general clues about cognitive processes in general. PMID:17267053

  12. Pathways and Barriers for Ion Translocation through the 5-HT3A Receptor Channel

    PubMed Central

    Di Maio, Danilo; Chandramouli, Balasubramanian; Brancato, Giuseppe

    2015-01-01

    Pentameric ligand gated ion channels (pLGICs) are ionotropic receptors that mediate fast intercellular communications at synaptic level and include either cation selective (e.g., nAChR and 5-HT3) or anion selective (e.g., GlyR, GABAA and GluCl) membrane channels. Among others, 5-HT3 is one of the most studied members, since its first cloning back in 1991, and a large number of studies have successfully pinpointed protein residues critical for its activation and channel gating. In addition, 5-HT3 is also the target of a few pharmacological treatments due to the demonstrated benefits of its modulation in clinical trials. Nonetheless, a detailed molecular analysis of important protein features, such as the origin of its ion selectivity and the rather low conductance as compared to other channel homologues, has been unfeasible until the recent crystallization of the mouse 5-HT3A receptor. Here, we present extended molecular dynamics simulations and free energy calculations of the whole 5-HT3A protein with the aim of better understanding its ion transport properties, such as the pathways for ion permeation into the receptor body and the complex nature of the selectivity filter. Our investigation unravels previously unpredicted structural features of the 5-HT3A receptor, such as the existence of alternative intersubunit pathways for ion translocation at the interface between the extracellular and the transmembrane domains, in addition to the one along the channel main axis. Moreover, our study offers a molecular interpretation of the role played by an arginine triplet located in the intracellular domain on determining the characteristic low conductance of the 5-HT3A receptor, as evidenced in previous experiments. In view of these results, possible implications on other members of the superfamily are suggested. PMID:26465896

  13. Effects of white spirits on rat brain 5-HT receptor functions and synaptic remodeling.

    PubMed

    Lam, H R; Plenge, P; Jørgensen, O S

    2001-01-01

    Previously, inhalation exposure to different types of white spirit (i.e. complex mixtures of aliphatic, aromatic, alkyl aromatic, and naphthenic hydrocarbons) has been shown to induce neurochemical effects in rat brains. Especially, the serotonergic system was involved at the global, regional, and subcellular levels. This study investigates the effects of two types of white spirit on 5-hydroxytryptamine (5-HT) transporters (5-HTT), 5-HT(2A) and 5-HT(4) receptor expression in forebrain, and on neural cell adhesion molecule (NCAM) and 25-kDa synaptosomal associated protein (SNAP-25) concentrations when applied as indices for synaptic remodeling in forebrain, hippocampus, and entorhinal cortex. Male Wistar rats were exposed to 0, 400, or 800 ppm of aromatic (20 vol.% aromatic hydrocarbons) or dearomatized white spirit (catalytically hydrogenated white spirit) in the inhaled air for 6 h/day, 7 days/week for 3 weeks. The 5-HTT B(max) and K(d) were not affected. Both types of white spirit at 800 ppm decreased B(max) for the 5-HT(2A) receptor. The aromatic type decreased the K(d) of the 5-HT(2A) and 5-HT(4) receptors at 800 ppm. Aromatic white spirit did not affect NCAM or SNAP-25 concentrations or NCAM/SNAP-25 ratio in forebrain, whereas NCAM increased in hippocampus and the NCAM/SNAP-25 ratio decreased in entorhinal cortex. Dearomatized white spirit did not affect NCAM, SNAP-25, or NCAM/SNAP-25 ratio in any brain region. The affected 5-HT receptor expression and synaptic plasticity marker proteins indicate that inhalation exposure to high concentrations of white spirit may be neurotoxic to rats, especially the aromatic white spirit type. PMID:11792528

  14. 5-HT obesity medication efficacy via POMC activation is maintained during aging.

    PubMed

    Burke, Luke K; Doslikova, Barbora; D'Agostino, Giuseppe; Garfield, Alastair S; Farooq, Gala; Burdakov, Denis; Low, Malcolm J; Rubinstein, Marcelo; Evans, Mark L; Billups, Brian; Heisler, Lora K

    2014-10-01

    The phenomenon commonly described as the middle-age spread is the result of elevated adiposity accumulation throughout adulthood until late middle-age. It is a clinical imperative to gain a greater understanding of the underpinnings of age-dependent obesity and, in turn, how these mechanisms may impact the efficacy of obesity treatments. In particular, both obesity and aging are associated with rewiring of a principal brain pathway modulating energy homeostasis, promoting reduced activity of satiety pro-opiomelanocortin (POMC) neurons within the arcuate nucleus of the hypothalamus (ARC). Using a selective ARC-deficient POMC mouse line, here we report that former obesity medications augmenting endogenous 5-hydroxytryptamine (5-HT) activity d-fenfluramine and sibutramine require ARC POMC neurons to elicit therapeutic appetite-suppressive effects. We next investigated whether age-related diminished ARC POMC activity therefore impacts the potency of 5-HT obesity pharmacotherapies, lorcaserin, d-fenfluramine, and sibutramine and report that all compounds reduced food intake to a comparable extent in both chow-fed young lean (3-5 months old) and middle-aged obese (12-14 months old) male and female mice. We provide a mechanism through which 5-HT anorectic potency is maintained with age, via preserved 5-HT-POMC appetitive anatomical machinery. Specifically, the abundance and signaling of the primary 5-HT receptor influencing appetite via POMC activation, the 5-HT2CR, is not perturbed with age. These data reveal that although 5-HT obesity medications require ARC POMC neurons to achieve appetitive effects, the anorectic efficacy is maintained with aging, findings of clinical significance to the global aging obese population. PMID:25051442

  15. Impact of intracellular domain flexibility upon properties of activated human 5-HT3 receptors*

    PubMed Central

    Kozuska, J L; Paulsen, I M; Belfield, W J; Martin, I L; Cole, D J; Holt, A; Dunn, S M J

    2014-01-01

    Background and Purpose It has been proposed that arginine residues lining the intracellular portals of the homomeric 5-HT3A receptor cause electrostatic repulsion of cation flow, accounting for a single-channel conductance substantially lower than that of the 5-HT3AB heteromer. However, comparison of receptor homology models for wild-type pentamers suggests that salt bridges in the intracellular domain of the homomer may impart structural rigidity, and we hypothesized that this rigidity could account for the low conductance. Experimental Approach Mutations were introduced into the portal region of the human 5-HT3A homopentamer, such that putative salt bridges were broken by neutralizing anionic partners. Single-channel and whole cell currents were measured in transfected tsA201 cells and in Xenopus oocytes respectively. Computational simulations of protein flexibility facilitated comparison of wild-type and mutant receptors. Key Results Single-channel conductance was increased substantially, often to wild-type heteromeric receptor values, in most 5-HT3A mutants. Conversely, introduction of arginine residues to the portal region of the heteromer, conjecturally creating salt bridges, decreased conductance. Gating kinetics varied significantly between different mutant receptors. EC50 values for whole-cell responses to 5-HT remained largely unchanged, but Hill coefficients for responses to 5-HT were usually significantly smaller in mutants. Computational simulations suggested increased flexibility throughout the protein structure as a consequence of mutations in the intracellular domain. Conclusions and Implications These data support a role for intracellular salt bridges in maintaining the quaternary structure of the 5-HT3 receptor and suggest a role for the intracellular domain in allosteric modulation of cooperativity and agonist efficacy. Linked Article This article is commented on by Vardy and Kenakin, pp. 1614–1616 of volume 171 issue 7. To view this commentary

  16. Pathways and Barriers for Ion Translocation through the 5-HT3A Receptor Channel.

    PubMed

    Di Maio, Danilo; Chandramouli, Balasubramanian; Brancato, Giuseppe

    2015-01-01

    Pentameric ligand gated ion channels (pLGICs) are ionotropic receptors that mediate fast intercellular communications at synaptic level and include either cation selective (e.g., nAChR and 5-HT3) or anion selective (e.g., GlyR, GABAA and GluCl) membrane channels. Among others, 5-HT3 is one of the most studied members, since its first cloning back in 1991, and a large number of studies have successfully pinpointed protein residues critical for its activation and channel gating. In addition, 5-HT3 is also the target of a few pharmacological treatments due to the demonstrated benefits of its modulation in clinical trials. Nonetheless, a detailed molecular analysis of important protein features, such as the origin of its ion selectivity and the rather low conductance as compared to other channel homologues, has been unfeasible until the recent crystallization of the mouse 5-HT3A receptor. Here, we present extended molecular dynamics simulations and free energy calculations of the whole 5-HT3A protein with the aim of better understanding its ion transport properties, such as the pathways for ion permeation into the receptor body and the complex nature of the selectivity filter. Our investigation unravels previously unpredicted structural features of the 5-HT3A receptor, such as the existence of alternative intersubunit pathways for ion translocation at the interface between the extracellular and the transmembrane domains, in addition to the one along the channel main axis. Moreover, our study offers a molecular interpretation of the role played by an arginine triplet located in the intracellular domain on determining the characteristic low conductance of the 5-HT3A receptor, as evidenced in previous experiments. In view of these results, possible implications on other members of the superfamily are suggested. PMID:26465896

  17. Striatal 5-HT6 Receptors Regulate Cocaine Reinforcement in a Pathway-Selective Manner.

    PubMed

    Brodsky, Matthew; Gibson, Alec W; Smirnov, Denis; Nair, Sunila G; Neumaier, John F

    2016-08-01

    The nucleus accumbens (NAc) in the ventral striatum integrates many neurochemical inputs including dopamine and serotonin projections from midbrain nuclei to modulate drug reward. Although D1 and D2 dopamine receptors are differentially expressed in the direct and indirect pathway medium spiny neurons (dMSNs and iMSNs, respectively), 5-HT6 receptors are expressed in both pathways, more strongly than anywhere else in the brain, and are an intriguing target for neuropsychiatric disorders. In the present study, we used viral vectors utilizing dynorphin or enkephalin promoters to drive expression of 5-HT6 receptors or green fluorescent protein (GFP) selectively in the dMSNs or iMSNs of the NAc shell. Rats were then trained to self-administer cocaine. Increased 5-HT6 receptor expression in dMSNs did not change any parameter of cocaine self-administration measured. However, increasing 5-HT6 receptors in iMSNs reduced the amount of cocaine self-administered under fixed-ratio schedules, especially at low doses, increased the time to the first response and the length of the inter-infusion interval, but did not alter motivation as measured by progressive ratio 'break point' analysis. Modeling of cocaine pharmacokinetics in NAc showed that increased 5-HT6 receptors in iMSNs reduced the rat's preferred tissue cocaine concentration at each dose. Finally, increased 5-HT6 receptors in iMSNs facilitated conditioned place preference for a low dose of cocaine. We conclude that 5-HT6 receptors in iMSNs of NAcSh increase the sensitivity to the reinforcing properties of cocaine, particularly at low doses, suggesting that these receptors may be a therapeutic target for the treatment of cocaine addiction. PMID:27032690

  18. The muscarinic antagonists scopolamine and atropine are competitive antagonists at 5-HT3 receptors.

    PubMed

    Lochner, Martin; Thompson, Andrew J

    2016-09-01

    Scopolamine is a high affinity muscarinic antagonist that is used for the prevention of post-operative nausea and vomiting. 5-HT3 receptor antagonists are used for the same purpose and are structurally related to scopolamine. To examine whether 5-HT3 receptors are affected by scopolamine we examined the effects of this drug on the electrophysiological and ligand binding properties of 5-HT3A receptors expressed in Xenopus oocytes and HEK293 cells, respectively. 5-HT3 receptor-responses were reversibly inhibited by scopolamine with an IC50 of 2.09 μM. Competitive antagonism was shown by Schild plot (pA2 = 5.02) and by competition with the 5-HT3 receptor antagonists [(3)H]granisetron (Ki = 6.76 μM) and G-FL (Ki = 4.90 μM). The related molecule, atropine, similarly inhibited 5-HT evoked responses in oocytes with an IC50 of 1.74 μM, and competed with G-FL with a Ki of 7.94 μM. The reverse experiment revealed that granisetron also competitively bound to muscarinic receptors (Ki = 6.5 μM). In behavioural studies scopolamine is used to block muscarinic receptors and induce a cognitive deficit, and centrally administered concentrations can exceed the IC50 values found here. It is therefore possible that 5-HT3 receptors are also inhibited. Studies that utilise higher concentrations of scopolamine should be mindful of these potential off-target effects. PMID:27108935

  19. Autoradiographic Evaluation of [(18)F]FECUMI-101, a High Affinity 5-HT1AR Ligand in Human Brain.

    PubMed

    Kumar, J S Dileep; Underwood, Mark D; Simpson, Norman R; Kassir, Suham A; Prabhakaran, Jaya; Majo, Vattoly J; Bakalian, Mihran J; Parsey, Ramin V; Mann, J John; Arango, Victoria

    2016-05-12

    [(18)F]FECUMI-101 ([(18)F]1) is a 5HT1AR ligand demonstrating specific binding in brain regions corresponding to the distribution of 5-HT1AR in baboons. However, we detected moderate uptake of [(18)F]1 in baboon thalamus, a brain region lacking 5-HT1AR. We sought to investigate the relative binding of [(18)F]1 to 5-HT1AR, α1R, and 5-HT7R in vitro. Using autoradiography in human brain sections, specific binding of [(18)F]1 to 5-HT1AR was confirmed. However, [(18)F]1 also showed 26% binding to α1R in PFC. The hippocampal formation exhibited 51% and 92% binding of [(18)F]1 to α1R and 5-HT1AR, respectively. Thalamus and cerebellum showed very little binding. There is no measurable specific binding of [(18)F]1 to 5-HT7R and no effect of temperature on [(18)F]1 specific binding to 5-HT1AR or α1R. These results indicate that, while [(18)F]FECUMI-101 is not a completely selective 5-HT1AR ligand for receptor quantification, it may be useful for occupancy measurements of drugs acting at 5-HT1AR in vivo. PMID:27190597

  20. Identification of spinal 5-HT sub 3 receptors and their role in the modulation of nociceptive responses in the rat

    SciTech Connect

    Glaum, S.R.

    1988-01-01

    The project consisted of two related studies: (1) the characterization of serotonin binding sites in crude and purified synaptic membranes prepared from the rat spinal cord, and (2) the association of serotonin binding sites with functional 5-HT receptor responses in the modulation of nociceptive information at the level of the spinal cord. The first series of experiments involved the preparation of membranes from the dorsal and ventral halves of the rat spinal cord and the demonstration of specific ({sup 3}H)serotonin binding to these membranes. High affinity binding sites which conformed to the 5-HT{sub 3} subtype were identified in dorsal, but not ventral spinal cord synaptic membranes. These experiments also confirmed the presence of high affinity ({sup 3}H)5-HT binding sites in dorsal spinal cord synaptic membranes of the 5-HT{sub 1} subtype. The second group of studies demonstrated the ability of selective 5-HT{sub 3} antagonists to inhibit the antinociceptive response to intrathecally administered 5-HT, as measured by a change in tail flick and hot plate latencies. Intrathecal pretreatment with the selective 5-HT{sub 3} antagonists ICS 205-930 or MDL 72222 abolished the antinociceptive effects of 5-HT. Furthermore, the selective 5-HT{sub 3} agonist 2-methyl-5-HT mimicked the antinociceptive effects of 5-HT.

  1. Micromolar-Affinity Benzodiazepine Receptors Regulate Voltage-Sensitive Calcium Channels in Nerve Terminal Preparations

    NASA Astrophysics Data System (ADS)

    Taft, William C.; Delorenzo, Robert J.

    1984-05-01

    Benzodiazepines in micromolar concentrations significantly inhibit depolarization-sensitive Ca2+ uptake in intact nerve-terminal preparations. Benzodiazepine inhibition of Ca2+ uptake is concentration dependent and stereospecific. Micromolar-affinity benzodiazepine receptors have been identified and characterized in brain membrane and shown to be distinct from nanomolar-affinity benzodiazepine receptors. Evidence is presented that micromolar, and not nanomolar, benzodiazepine binding sites mediate benzodiazepine inhibition of Ca2+ uptake. Irreversible binding to micromolar benzodiazepine binding sites also irreversibly blocked depolarization-dependent Ca2+ uptake in synaptosomes, indicating that these compounds may represent a useful marker for identifying the molecular components of Ca2+ channels in brain. Characterization of benzodiazepine inhibition of Ca2+ uptake demonstrates that these drugs function as Ca2+ channel antagonists, because benzodiazepines effectively blocked voltage-sensitive Ca2+ uptake inhibited by Mn2+, Co2+, verapamil, nitrendipine, and nimodipine. These results indicate that micromolar benzodiazepine binding sites regulate voltage-sensitive Ca2+ channels in brain membrane and suggest that some of the neuronal stabilizing effects of micromolar benzodiazepine receptors may be mediated by the regulation of Ca2+ conductance.

  2. Mitochondrial Calcium Uptake Modulates Synaptic Vesicle Endocytosis in Central Nerve Terminals*

    PubMed Central

    Marland, Jamie Roslin Keynes; Hasel, Philip; Bonnycastle, Katherine; Cousin, Michael Alan

    2016-01-01

    Presynaptic calcium influx triggers synaptic vesicle (SV) exocytosis and modulates subsequent SV endocytosis. A number of calcium clearance mechanisms are present in central nerve terminals that regulate intracellular free calcium levels both during and after stimulation. During action potential stimulation, mitochondria rapidly accumulate presynaptic calcium via the mitochondrial calcium uniporter (MCU). The role of mitochondrial calcium uptake in modulating SV recycling has been debated extensively, but a definitive conclusion has not been achieved. To directly address this question, we manipulated the expression of the MCU channel subunit in primary cultures of neurons expressing a genetically encoded reporter of SV turnover. Knockdown of MCU resulted in ablation of activity-dependent mitochondrial calcium uptake but had no effect on the rate or extent of SV exocytosis. In contrast, the rate of SV endocytosis was increased in the absence of mitochondrial calcium uptake and slowed when MCU was overexpressed. MCU knockdown did not perturb activity-dependent increases in presynaptic free calcium, suggesting that SV endocytosis may be controlled by calcium accumulation and efflux from mitochondria in their immediate vicinity. PMID:26644474

  3. alpha2-Adrenoceptors control the release of noradrenaline but not neuropeptide Y from perivascular nerve terminals.

    PubMed

    Donoso, M Veronica; Carvajal, Andrés; Paredes, Alfonso; Tomic, Alexander; Koenig, Cecilia S; Huidobro-Toro, J Pablo

    2002-09-01

    Neuropeptide Y (NPY) and noradrenaline (NA) are co-transmitters at many sympathetic synapses, but it is not yet clear if their release is independently regulated. To address this question, we quantified the electrically evoked release of these co-transmitters from perivascular nerve terminals to the mesenteric circulation in control and drug-treated rats. 6-Hydroxydopamine reduced the tissue content and the electrically evoked release of ir-NPY and NA as well as the rise in perfusion pressure. A 0.001 mg/kg reserpine reduced the content of ir-NPY and NA, but did not modify their release nor altered the rise in perfusion pressure elicited by the electrical stimuli. However, 0.1mg/kg reserpine reduced both the content and release of NA but decreased only the content but not the release of ir-NPY; the rise in perfusion pressure was halved. Clonidine did not affect the release of ir-NPY while it lowered the outflow of NA, not altering the rise in perfusion pressure elicited by the electrical stimuli. Yohimbine, did not modify the release of ir-NPY but increased the NA outflow, it antagonized the clonidine effect. Therefore, presynaptic alpha2-adrenoceptors modulate the release of NA but not NPY, implying separate regulatory mechanisms. PMID:12217427

  4. Analysis of protein phosphorylation in nerve terminal reveals extensive changes in active zone proteins upon exocytosis

    PubMed Central

    Kohansal-Nodehi, Mahdokht; Chua, John JE; Urlaub, Henning; Jahn, Reinhard; Czernik, Dominika

    2016-01-01

    Neurotransmitter release is mediated by the fast, calcium-triggered fusion of synaptic vesicles with the presynaptic plasma membrane, followed by endocytosis and recycling of the membrane of synaptic vesicles. While many of the proteins governing these processes are known, their regulation is only beginning to be understood. Here we have applied quantitative phosphoproteomics to identify changes in phosphorylation status of presynaptic proteins in resting and stimulated nerve terminals isolated from the brains of Wistar rats. Using rigorous quantification, we identified 252 phosphosites that are either up- or downregulated upon triggering calcium-dependent exocytosis. Particularly pronounced were regulated changes of phosphosites within protein constituents of the presynaptic active zone, including bassoon, piccolo, and RIM1. Additionally, we have mapped kinases and phosphatases that are activated upon stimulation. Overall, our study provides a snapshot of phosphorylation changes associated with presynaptic activity and provides a foundation for further functional analysis of key phosphosites involved in presynaptic plasticity. DOI: http://dx.doi.org/10.7554/eLife.14530.001 PMID:27115346

  5. Immunoglobulins from amyotrophic lateral sclerosis patients enhance spontaneous transmitter release from motor-nerve terminals.

    PubMed Central

    Uchitel, O D; Appel, S H; Crawford, F; Sczcupak, L

    1988-01-01

    Amyotrophic lateral sclerosis (ALS) is an incapacitating neuromuscular disease of unknown etiology. Although laboratory evidence is lacking, circumstantial evidence supports the importance of immune factors in the pathogenesis of ALS. In the present study immunoglobulins from 4 of 8 ALS patients induced a significant increase in spontaneous quantal transmitter release as monitored by miniature end-plate potential (MEPP) frequency in mouse phrenic nerve-diaphragm preparations at 23 degrees C, whereas immunoglobulins from normal individuals and from patients with other neuromuscular diseases had no effect. At 32 degrees C neither normal nor disease control immunoglobulins influenced MEPP frequency, but 8 of 11 ALS immunoglobulin samples produced a significant increase in spontaneous quantal transmitter release. The enhancing effect could be prevented by 10 mM Mg2+. No effects were noted on MEPP amplitude and muscle resting potential. These findings suggest that the presynaptic terminal of the motor neuron may be an early target and that immunological factors may play an important role in the disease process. PMID:2902629

  6. Mitochondrial bioenergetics and neuronal survival modelled in primary neuronal culture and isolated nerve terminals.

    PubMed

    Nicholls, David G; Brand, Martin D; Gerencser, Akos A

    2015-04-01

    Mitochondria play multiple roles in the maintenance of neuronal function under physiological and pathological conditions. In addition to ATP generation, they can act as major short-term calcium sinks and can both generate, and be damaged by, reactive oxygen species. Two complementary preparations have been extensively employed to investigate in situ neuronal mitochondrial bioenergetics, primary neuronal cultures and acutely isolated nerve terminals, synaptosomes. A major focus of the cell culture preparation has been the investigation of glutamate excitotoxicity. Oxidative phosphorylation, calcium transport and reactive oxygen species play complex interlocking roles in the life and death of the glutamate exposed neuron. Synaptosomes may be isolated from specific brain regions at any developmental stage and therefore provide a valuable ex vivo approach in studying mouse models. Recent advances have allowed synaptosomal bioenergetics to be studied on a microgram scale, and, in combination with approaches to correct for functional and transmitter heterogeneity, have allowed hypotheses concerning presynaptic mitochondrial dysfunction to be tested on a variety of genetic models of neurodegenerative disorders. PMID:25172197

  7. Mitochondrial Calcium Uptake Modulates Synaptic Vesicle Endocytosis in Central Nerve Terminals.

    PubMed

    Marland, Jamie Roslin Keynes; Hasel, Philip; Bonnycastle, Katherine; Cousin, Michael Alan

    2016-01-29

    Presynaptic calcium influx triggers synaptic vesicle (SV) exocytosis and modulates subsequent SV endocytosis. A number of calcium clearance mechanisms are present in central nerve terminals that regulate intracellular free calcium levels both during and after stimulation. During action potential stimulation, mitochondria rapidly accumulate presynaptic calcium via the mitochondrial calcium uniporter (MCU). The role of mitochondrial calcium uptake in modulating SV recycling has been debated extensively, but a definitive conclusion has not been achieved. To directly address this question, we manipulated the expression of the MCU channel subunit in primary cultures of neurons expressing a genetically encoded reporter of SV turnover. Knockdown of MCU resulted in ablation of activity-dependent mitochondrial calcium uptake but had no effect on the rate or extent of SV exocytosis. In contrast, the rate of SV endocytosis was increased in the absence of mitochondrial calcium uptake and slowed when MCU was overexpressed. MCU knockdown did not perturb activity-dependent increases in presynaptic free calcium, suggesting that SV endocytosis may be controlled by calcium accumulation and efflux from mitochondria in their immediate vicinity. PMID:26644474

  8. 5-HT7 receptor modulates GABAergic transmission in the rat dorsal raphe nucleus and controls cortical release of serotonin

    PubMed Central

    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. PMID:26347612

  9. Chemoproteomic Approach to Explore the Target Profile of GPCR ligands: Application to 5-HT1A and 5-HT6 Receptors.

    PubMed

    Gamo, Ana M; González-Vera, Juan A; Rueda-Zubiaurre, Ainoa; Alonso, Dulce; Vázquez-Villa, Henar; Martín-Couce, Lidia; Palomares, Óscar; López, Juan A; Martín-Fontecha, Mar; Benhamú, Bellinda; López-Rodríguez, María L; Ortega-Gutiérrez, Silvia

    2016-01-22

    Determination of the targets of a compound remains an essential aspect in drug discovery. A complete understanding of all binding interactions is critical to recognize in advance both therapeutic effects and undesired consequences. However, the complete polypharmacology of many drugs currently in clinical development is still unknown, especially in the case of G protein-coupled receptor (GPCR) ligands. In this work we have developed a chemoproteomic platform based on the use of chemical probes to explore the target profile of a compound in biological systems. As proof of concept, this methodology has been applied to selected ligands of the therapeutically relevant serotonin 5-HT1A and 5-HT6 receptors, and we have identified and validated some of their off-targets. This approach could be extended to other drugs of interest to study the targeted proteome in disease-relevant systems. PMID:26560738

  10. Rat exposure in mice with neuropathic pain induces fear and antinociception that is not reversed by 5-HT2C receptor activation in the dorsal periaqueductal gray.

    PubMed

    Furuya-da-Cunha, Elke Mayumi; Souza, Rimenez Rodrigues de; Canto-de-Souza, Azair

    2016-07-01

    Previous studies have demonstrated that serotonin 5-HT2C receptors in the dorsal periaqueductal gray (dPAG) mediate both anxiety and antinociception in mice submitted to the elevated plus maze. The present study examined the effects of intra-dPAG infusion of the serotonin 5-HT2C receptor agonist (MK-212) in the defensive reactions and antinociception in mice with neurophatic pain confronted by a predator. Neuropathic pain was induced by chronic constriction injury (CCI) of the sciatic nerve, and predator confrontation was performed using the rat exposure test (RET). Our results demonstrated that both sham-operated and CCI mice exhibited intense defensive reactions when confronted by rats. However, rat-exposed CCI mice showed reduced pain reactivity in comparison to CCI mice exposed to a toy rat. Intra-dPAG infusion of MK-212 prior to predator exposure did not significantly alter defensive or antinociceptive responses. To our knowledge, our results represent the first evidence of RET-induced antinociception in mice. Moreover, the results of the present study suggest that 5-HT2C receptor activation in the dPAG is not critically involved in the control of predator-evoked fearful or antinociceptive responses. PMID:27059332

  11. Drug-induced defaecation in rats: role of central 5-HT1A receptors.

    PubMed Central

    Croci, T.; Landi, M.; Bianchetti, A.; Manara, L.

    1995-01-01

    1. We investigated the acute effects of 5-hydroxytryptamine (5-HT), and of the 5-HT1A receptor agonists, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), buspirone and SR 57746A, on rat faecal pellet output and water content. 2. 5-HT, 8-OH-DPAT, buspirone and SR 57746A, a new selective 5-HT1A receptor agonist, displaced [3H]-8-OH-DPAT from specific binding sites in rat hippocampus membranes (Ki, nM; 1.8, 1.2, 15, 3.1 respectively) and stimulated rat defaecation dose-dependently. SR 57746A and buspirone induced 1 g dry weight of faeces at 1.3 and 6.1 mg kg-1, p.o. (AD1) respectively. 8-OH-DPAT and 5-HT stimulated defaecation after s.c. injection (AD1, 0.07 and 7.5 mg kg-1, respectively). All these agents increased faecal water content. 3. The putative 5-HT1A receptor antagonist, pindolol, injected s.c. or i.c.v., significantly reduced the defaecation induced by systemically administered 8-OH-DPAT, buspirone or SR 57746A, but not 5-HT. 4. Pretreatment with p-chlorophenylalanine (i.p.) or 5,7-dihydroxytryptamine (i.c.v.), according to protocols designed to cause either generalized or CNS-limited 5-HT depletion respectively, also reduced the defaecation induced by buspirone or SR 57746A. 5. No specific 5-HT1A binding sites could be labelled by incubating rat colon membranes with [3H]-8-OH-DPAT, and in vitro preparations of rat colon segments showed no response to 8-OH-DPAT or SR 57746A up to 5 microM. 6. After eight days' repeated daily treatment, complete tolerance developed to the stimulant effects of SR 57746A and buspirone on faecal water content, but not on faecal pellet output.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7647978

  12. SB 242084, a selective and brain penetrant 5-HT2C receptor antagonist.

    PubMed

    Kennett, G A; Wood, M D; Bright, F; Trail, B; Riley, G; Holland, V; Avenell, K Y; Stean, T; Upton, N; Bromidge, S; Forbes, I T; Brown, A M; Middlemiss, D N; Blackburn, T P

    1997-01-01

    SB 242084 has a high affinity (pKi 9.0) for the cloned human 5-HT2C receptor and 100- and 158-fold selectivity over the closely related cloned human 5-HT2B and 5-HT2A subtypes respectively. SB 242084 had over 100-fold selectivity over a range of other 5-HT, dopamine and adrenergic receptors. In studies of 5-HT-stimulated phosphatidylinositol hydrolysis using SH-SY5Y cells stably expressing the cloned human 5-HT2C receptor, SB 242084 acted as an antagonist with a pKb of 9.3, which closely resembled its corresponding receptor binding affinity. SB 242084 potently inhibited m-chlorophenylpiperazine (mCPP, 7 mgkg i.p. 20 min pre-test)-induced hypolocomotion in rats, a model of in vivo central 5-HT2C receptor function, with an ID50 of 0.11 mg/kg i.p., and 2.0 mg/kg p.o. SB 242084 (0.1-1 mg/kg i.p.) exhibited an anxiolytic-like profile in the rat social interaction test, increasing time spent in social interaction, but having no effect on locomotion. SB 242084 (0.1-1 mg/kg i.p.) also markedly increased punished responding in a rat Geller-Seifter conflict test of anxiety, but had no consistent effect on unpunished responding. A large acute dose of SB 242084 (30 mg/kg p.o.) had no effect on seizure susceptibility in the rat maximal electroshock seizure threshold test. Also, while SB 242084 (2 and 6 mg/kg p.o. 1 hr pre-test) antagonized the hypophagic response to mCPP, neither acute nor subchronic administration of the drug, for 5 days at 2 or 6 mg/kg p.o. twice daily, affected food intake or weight gain. The results suggest that SB 242084 is the first reported selective potent and brain penetrant 5-HT2C receptor antagonist and has anxiolytic-like activity, but does not possess either proconvulsant or hyperphagic properties which are characteristic of mutant mice lacking the 5-HT2C receptor. PMID:9225286

  13. Antidepressant- and Anxiolytic-Like Effects of New Dual 5-HT1A and 5-HT7 Antagonists in Animal Models

    PubMed Central

    Pytka, Karolina; Partyka, Anna; Jastrzębska-Więsek, Magdalena; Siwek, Agata; Głuch-Lutwin, Monika; Mordyl, Barbara; Kazek, Grzegorz; Rapacz, Anna; Olczyk, Adrian; Gałuszka, Adam; Błachuta, Marian; Waszkielewicz, Anna; Marona, Henryk; Sapa, Jacek; Filipek, Barbara; Wesołowska, Anna

    2015-01-01

    The aim of this study was to further characterize pharmacological properties of two phenylpiperazine derivatives: 1-{2-[2-(2,6-dimethlphenoxy)ethoxy]ethyl}-4-(2-methoxyphenyl)piperazynine hydrochloride (HBK-14) and 2-[2-(2-chloro-6-methylphenoxy)ethoxy]ethyl-4-(2- methoxyphenyl)piperazynine dihydrochloride (HBK-15) in radioligand binding and functional in vitro assays as well as in vivo models. Antidepressant-like properties were investigated in the forced swim test (FST) in mice and rats. Anxiolytic-like activity was evaluated in the four-plate test in mice and elevated plus maze test (EPM) in rats. Imipramine and escitalopram were used as reference drugs in the FST, and diazepam was used as a standard anxiolytic drug in animal models of anxiety. Our results indicate that HBK-14 and HBK-15 possess high or moderate affinity for serotonergic 5-HT2, adrenergic α1, and dopaminergic D2 receptors as well as being full 5-HT1A and 5-HT7 receptor antagonists. We also present their potent antidepressant-like activity (HBK-14—FST mice: 2.5 and 5 mg/kg; FST rats: 5 mg/kg) and (HBK-15—FST mice: 1.25, 2.5 and 5 mg/kg; FST rats: 1.25 and 2.5 mg/kg). We show that HBK-14 (four-plate test: 2.5 and 5 mg/kg; EPM: 2.5 mg/kg) and HBK-15 (four-plate test: 2.5 and 5 mg/kg; EPM: 5 mg/kg) possess anxiolytic-like properties. Among the two, HBK-15 has stronger antidepressant-like properties, and HBK-14 displays greater anxiolytic-like activity. Lastly, we demonstrate the involvement of serotonergic system, particularly 5-HT1A receptor, in the antidepressant- and anxiolytic-like actions of investigated compounds. PMID:26554929

  14. Enhanced head-twitch response to 5-HT-related agonists in thiamine-deficient mice.

    PubMed

    Nakagawasai, O; Murata, A; Arai, Y; Ohba, A; Wakui, K; Mitazaki, S; Niijima, F; Tan-No, K; Tadano, T

    2007-01-01

    While many studies suggest an involvement of brain serotonergic systems in neuro-psychiatric disorders such as schizophrenia and depression, their role in Wernicke-Korsakoff syndrome (WKS) remains unclear. Since dietary thiamine deficiency (TD) in mice is considered as a putative model of WKS, it was used in the present study to investigate the function of serotonergic neurons in this disorder. After 20 days of TD feeding, the intensity of tryptophan hydroxylase immunofluorescence was found to be significantly decreased in the dorsal and medial raphe nuclei. In addition, the head-twitch response (HTR) elicited by the intracerebroventricular administration of the 5-HT(2A) agonist 2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI) was significantly increased in TD versus control mice, whereas the injection of ketanserin, a 5-HT(2A) receptor antagonist, prevented this enhancement. A single injection of thiamine HCl on the 19th day of TD feeding did not reduce the enhanced DOI-induced HTR. On the other hand, the administration of d-fenfluramine, a 5-HT releaser, did not enhance the HTR in TD mice. Together, our results indicate that TD causes a super-sensitivity of 5-HT(2A) receptors by reducing presynaptic 5-HT synthesis derived from degenerating neurons projecting from the raphe nucleus. PMID:17372673

  15. Novel N-acyl-carbazole derivatives as 5-HT7R antagonists.

    PubMed

    Kim, Youngjae; Yeom, Miyoung; Tae, Jinsung; Rhim, Hyewhon; Choo, Hyunah

    2016-03-01

    To discover a novel 5-HT7R antagonist for treatment of depression, we designed N-acyl-carbazole derivatives which were synthesized and biologically evaluated against 5-HT7R. Among total 30 compounds synthesized, four compounds 27-30 showed good binding affinities with Ki values of <100 nM. The compound 28, 1-(9H-carbazol-9-yl)-6-(4-(2-methoxyphenyl)piperazin-1-yl)hexan-1-one, showed good selectivity over other serotonin receptor subtypes and turned out to be a novel selective 5-HT7R antagonist following functional assays. The compound 28 showed moderate activity on hERG channel and good stability in microsomal stability test. The compound 28 exhibited a good pharmacokinetic profile with 67.8% oral bioavailability and good penetration to the brain. The compound 28 was also tested in in vivo depression animal model and showed antidepressant effect in the forced swimming test. Therefore, the selective 5-HT7R antagonist 28 can be considered as a good lead for discovery of novel 5-HT7R antagonists as antidepressants. PMID:26852005

  16. Reappraisal of the serotonin 5-HT(1B) receptor gene in alcoholism: of mice and men.

    PubMed

    Gorwood, Philip; Aissi, Franck; Batel, Philippe; Adès, Jean; Cohen-Salmon, Charles; Hamon, Michel; Boni, Claudette; Lanfumey, Laurence

    2002-01-01

    Because pharmacological and genetic data supported the idea that serotonin receptors of the 5-HT(1B) type can play a modulatory role in alcohol consumption in both human and rodents, the 5-HT(1B) receptor gene is considered as a candidate gene for alcohol dependence. However, contradictory results have been reported as a positive association between alcohol dependence, and either the 861C or the 861G allele of the G861C polymorphism of the 5-HT(1B) receptor gene can be found in the literature. Further investigations in a population of 136 male alcoholics compared with 72 male control subjects demonstrated that none of these alleles was actually associated with alcohol dependence. In addition, in contrast with previous results of the literature, ethanol intake under free choice conditions (i.e., ethanol solution vs. water) was found to be similar in 5-HT(1B)-/- knock mice and paired wild-type controls. The 5-HT(1B) receptor gene may thus not be a key component in the genetic background underlying alcohol dependence in human and alcohol preference in rodents, although these results should be considered as preliminary according to the small size of our sample. PMID:11827742

  17. The Role of Hippocampal 5HT3 Receptors in Harmaline-Induced Memory Deficit

    PubMed Central

    Nasehi, Mohammad

    2015-01-01

    Introduction: The plethora of studies indicated that there is a cross talk relationship between harmaline and serotonergic (5-HT) system on cognitive and non-cognitive behaviors. Thus, the purpose of this study is to assess the effects of hippocampal 5-HT4 receptor on memory acquisition deficit induced by harmaline. Methods: Harmaline was injected peritoneally, while 5-HT4 receptor agonist (RS67333) and antagonist (RS23597-190) were injected intra-hippocampal. A single-trial step-down passive avoidance, open field and tail flick tasks were used for measurement of memory, locomotor activity and pain responses, respectively. Results: The data revealed that pre-training injection of higher dose of harmaline (1 mg/kg), RS67333 (0.5 ng/mouse) and RS23597-190 (0.5 ng/mouse) decreased memory acquisition process in the adult mice. Moreover, concurrent pre-training administration of subthreshold dose of RS67333 (0.005 ng/mouse) or RS23597-190 (0.005 ng/mouse) with subthreshold dose of harmaline (0.5 mg/kg, i.p.) intensify impairment of memory acquisition. All above interventions did not change locomotion and tail flick behaviors. Discussion: The results demonstrated that the synergistic effect between both hippocampal 5-HT4 receptor agonist and antagonist with impairment of memory acquisition induced by harmaline, indicating a modulatory effect for hippocampal 5HT4 receptor on Harmaline induced amnesia. PMID:26904173

  18. Prostaglandin potentiates 5-HT responses in stomach and ileum innervating visceral afferent sensory neurons.

    PubMed

    Kim, Sojin; Jin, Zhenhua; Lee, Goeun; Park, Yong Seek; Park, Cheung-Seog; Jin, Young-Ho

    2015-01-01

    Gastrointestinal disorder is a common symptom induced by diverse pathophysiological conditions that include food tolerance, chemotherapy, and irradiation for therapy. Prostaglandin E2 (PGE2) level increase was often reported during gastrointestinal disorder and prostaglandin synthetase inhibitors has been used for ameliorate the symptoms. Exogenous administration of PGE2 induces gastrointestinal disorder, however, the mechanism of action is not known. Therefore, we tested PGE2 effect on visceral afferent sensory neurons of the rat. Interestingly, PGE2 itself did not evoked any response but enhanced serotonin (5-HT)-evoked currents up to 167% of the control level. The augmented 5-HT responses were completely inhibited by a 5-HT type 3 receptor antagonist, ondansetron. The PGE2-induced potentiation were blocked by a selective E-prostanoid type 4 (EP4) receptors antagonist, L-161,982, but type 1 and 2 receptor antagonist AH6809 has no effect. A membrane permeable protein kinase A (PKA) inhibitor, KT5720 also inhibited PGE2 effects. PGE2 induced 5-HT current augmentation was observed on 15% and 21% of the stomach and ileum projecting neurons, respectively. Current results suggest a synergistic signaling in visceral afferent neurons underlying gastrointestinal disorder involving PGE2 potentiation of 5-HT currents. Our findings may open a possibility for screen a new type drugs with lower side effects than currently using steroidal prostaglandin synthetase inhibitors by selectively targeting EP4 receptor/PKA pathway without interrupt prostaglandin synthesis. PMID:25446121

  19. Life Beyond Kinases: Structure-based Discovery of Sorafenib as Nanomolar Antagonist of 5-HT Receptors

    PubMed Central

    Lin, Xingyu; Huang, Xi-Ping; Chen, Gang; Whaley, Ryan; Peng, Shiming; Wang, Yanli; Zhang, Guoliang; Wang, Simon X.; Wang, Shaohui; Roth, Bryan L.; Huang, Niu

    2012-01-01

    Of great interest in recent years has been computationally predicting the novel polypharmacology of drug molecules. Here, we applied an “induced-fit” protocol to improve the homology models of 5-HT2A receptor, and we assessed the quality of these models in retrospective virtual screening. Subsequently, we computationally screened the FDA approved drug molecules against the best induced-fit 5-HT2A models, and chose six top scoring hits for experimental assays. Surprisingly, one well-known kinase inhibitor, sorafenib has shown unexpected promiscuous 5-HTRs binding affinities, Ki = 1959, 56 and 417 nM against 5-HT2A, 5-HT2B and 5-HT2C, respectively. Our preliminary SAR exploration supports the predicted binding mode, and further suggests sorafenib to be a novel lead compound for 5HTR ligand discovery. Although it has been well known that sorafenib produces anticancer effects through targeting multiple kinases, carefully designed experimental studies are desirable to fully understand whether its “off-target” 5-HTR binding activities contribute to its therapeutic efficacy or otherwise undesirable side effects. PMID:22694093

  20. Intact sciatic myelinated primary afferent terminals collaterally sprout in the adult rat dorsal horn following section of a neighbouring peripheral nerve.

    PubMed

    Doubell, T P; Mannion, R J; Woolf, C J

    1997-03-31

    Peripheral nerve section induces sprouting of the central terminals of axotomized myelinated primary afferents outside their normal dorsoventral termination zones in lamina I, III, and IV of the dorsal horn into lamina II, an area that normally only receives unmyelinated C-fiber input. This axotomy-induced regenerative sprouting is confined to the somatotopic boundaries of the injured nerve in the spinal cord. We examined whether intact myelinated sciatic afferents are able to sprout novel terminals into neighbouring areas of the dorsal horn in the adult rat following axotomy of two test nerves, either the posterior cutaneous nerve of the thigh or the saphenous nerve. These peripheral nerves have somatotopically organized terminal areas in the dorsal horn that overlap in some areas and are contiguous in others, with that of the sciatic central terminal field. Two weeks after cutting either the posterior cutaneous or the saphenous nerve, intact sciatic myelinated fibers labelled with the B fragment of cholera toxin conjugated to horseradish peroxidase (B-HRP) sprouted into an area of lamina II normally only innervated by the adjacent injured test nerve. This collateral sprouting was strictly limited, however, to those particular areas of the dorsal horn where the A-fiber terminal field of the control sciatic and the C-fiber terminal field of the injured test nerve overlapped in the dorsoventral plane. No mediolateral sprouting was seen into those areas of neuropil solely innervated by the test nerve. We conclude that intact myelinated primary afferents do have the capacity to collaterally sprout, but that any resultant somatotopic reorganization of central projections is limited to the dorsoventral plane. These changes may contribute to sensory hypersensitivity at the edges of denervated skin. PMID:9073085

  1. Brain-Derived Neurotrophic Factor Inhibits Calcium Channel Activation, Exocytosis, and Endocytosis at a Central Nerve Terminal

    PubMed Central

    Baydyuk, Maryna; Wu, Xin-Sheng; He, Liming

    2015-01-01

    Brain-derived neurotrophic factor (BDNF) is a neurotrophin that regulates synaptic function and plasticity and plays important roles in neuronal development, survival, and brain disorders. Despite such diverse and important roles, how BDNF, or more generally speaking, neurotrophins affect synapses, particularly nerve terminals, remains unclear. By measuring calcium currents and membrane capacitance during depolarization at a large mammalian central nerve terminal, the rat calyx of Held, we report for the first time that BDNF slows down calcium channel activation, including P/Q-type channels, and inhibits exocytosis induced by brief depolarization or single action potentials, inhibits slow and rapid endocytosis, and inhibits vesicle mobilization to the readily releasable pool. These presynaptic mechanisms may contribute to the important roles of BDNF in regulating synapses and neuronal circuits and suggest that regulation of presynaptic calcium channels, exocytosis, and endocytosis are potential mechanisms by which neurotrophins achieve diverse neuronal functions. PMID:25788684

  2. Target-specific regulation of presynaptic release properties at auditory nerve terminals in the avian cochlear nucleus.

    PubMed

    Ahn, J; MacLeod, K M

    2016-03-01

    Short-term synaptic plasticity (STP) acts as a time- and firing rate-dependent filter that mediates the transmission of information across synapses. In the auditory brain stem, the divergent pathways that encode acoustic timing and intensity information express differential STP. To investigate what factors determine the plasticity expressed at different terminals, we tested whether presynaptic release probability differed in the auditory nerve projections to the two divisions of the avian cochlear nucleus, nucleus angularis (NA) and nucleus magnocellularis (NM). Estimates of release probability were made with an open-channel blocker ofN-methyl-d-aspartate (NMDA) receptors. Activity-dependent blockade of NMDA receptor-mediated excitatory postsynaptic currents (EPSCs) with application of 20 μM (+)-MK801 maleate was more rapid in NM than in NA, indicating that release probability was significantly higher at terminals in NM. Paired-pulse ratio (PPR) was tightly correlated with the blockade rate at terminals in NA, suggesting that PPR was a reasonable proxy for relative release probability at these synapses. To test whether release probability was similar across convergent inputs onto NA neurons, PPRs of different nerve inputs onto the same postsynaptic NA target neuron were measured. The PPRs, as well as the plasticity during short trains, were tightly correlated across multiple inputs, further suggesting that release probability is coordinated at auditory nerve terminals in a target-specific manner. This highly specific regulation of STP in the auditory brain stem provides evidence that the synaptic dynamics are tuned to differentially transmit the auditory information in nerve activity into parallel ascending pathways. PMID:26719087

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

    PubMed

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

    2015-05-01

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

  4. Pulsatile release of acetylcholine by nerve terminals (synaptosomes) isolated from Torpedo electric organ.

    PubMed Central

    Girod, R; Eder-Colli, L; Medilanski, J; Dunant, Y; Tabti, N; Poo, M M

    1992-01-01

    1. Electrophysiological detection of acetylcholine (ACh) release by synaptosomes from the electric organ of Torpedo was searched for by laying the isolated nerve terminals on a culture of Xenopus embryonic muscle cells (myocytes), and by recording the ACh-induced inward currents in the myocytes. 2. Whole-cell recording in one of the myocytes revealed rapid inward currents that where generated soon after synaptosome application. These pulsatile events strongly resembled those occurring normally during the early phase of synaptogenesis after nerve-muscle contact in Xenopus cell cultures. They were called spontaneous synaptic currents (SSCs). 3. The SSCs produced by the synaptosomes had a rapid time course, with mean time-to-peak and half-decay times of 2.6 +/- 0.4 ms and 6.0 +/- 1.1 ms, respectively. Most events had a falling phase that could be fitted with a single exponential. The mean time constant of decay was 6.2 +/- 1.1 ms. More than half of the SSCs (approximately 60%) constituted a rather homogenous population in which the time-to-peak versus amplitude showed a positive relationship, the smallest events displaying a shorter time course. The rest of the SSCs had a more variable and slower time course. Such events are also observed in young and mature junctions in situ. 4. The amplitudes of SSCs had a wide distribution which was skewed towards the smallest values. The mean amplitude was 65.2 +/- 16.1 pA. 5. During the minutes following an application of synaptosomes, the frequency of the SSCs tended to decrease, but their mean amplitude remained constant. Such behaviour could be reproduced during several successive additions of synaptosomes while recording in the same myocyte. 6. Just after synaptosome application, the SSCs were superposed to a noisy inward current that lasted for 20-60 s. Noise analysis of this current gave the values of 0.7 +/- 0.1 pA for the mean amplitude of the elementary event, and 4.7 +/- 0.2 ms for its mean duration, values that compare

  5. GABA, 5-HT and amino acids in the rotifers Brachionus plicatilis and Brachionus rotundiformis.

    PubMed

    Gallardo, W G; Hagiwara, A; Hara, K; Soyano, K; Snell, T W

    2000-11-01

    gamma-Aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) have been shown to increase the reproduction of the Brachionus plicatilis (NH3L strain). In the present study, the endogenous presence of GABA and 5-HT in the rotifers B. plicatilis (NH3L and Kamiura strains) and Brachionus rotundiformis (Langkawi strain) were confirmed by dot blot immunoassay and high-performance liquid chromatography (HPLC). HPLC showed that GABA and 5-HT concentrations in the three rotifer strains range from 71 to 188 pmol/mg and from 12 to 64 pmol/mg, respectively. A total of 33 amino acids were also detected in B. plicatilis and B. rotundiformis, with glutamic acid, serine, glycine, taurine, threonine, alanine, arginine, proline, valine and isoleucine in high concentrations relative to other amino acids. PMID:11118940

  6. A-to-I editing of the 5HT2C receptor and behaviour.

    PubMed

    Gardiner, Katheleen; Du, Yunzhi

    2006-03-01

    Site-specific deamination of five adenosine residues in the pre-mRNA of the serotonin 2C receptor, 5HT2CR, alters the amino acid sequence of the encoded protein. Such RNA editing can produce 32 mRNA variants, encoding 24 protein isoforms that vary in biochemical and pharmacological properties. Because serotonin functions in the regulation of mood and behaviour, modulation of serotonin signalling by RNA editing may be relevant to such psychiatric disorders as anxiety and depression. Several recent human studies have reported changes in 5HT2CR editing in schizophrenia, major depression or suicide, but results are variable and not conclusive. Rodent studies have begun to examine effects of drug treatments and stress. Understanding the importance of 5HT2CR editing in mood and behaviour will be assisted by experiments designed to analyse multiple strains of mice, in different behavioural tests, with optimal evaluation of the time course of molecular changes. PMID:16769676

  7. 3D Pharmacophore, hierarchical methods, and 5-HT4 receptor binding data.

    PubMed

    Varin, Thibault; Saettel, Nicolas; Villain, Jonathan; Lesnard, Aurelien; Dauphin, François; Bureau, Ronan; Rault, Sylvain

    2008-10-01

    5-Hydroxytryptamine subtype-4 (5-HT(4)) receptors have stimulated considerable interest amongst scientists and clinicians owing to their importance in neurophysiology and potential as therapeutic targets. A comparative analysis of hierarchical methods applied to data from one thousand 5-HT(4) receptor-ligand binding interactions was carried out. The chemical structures were described as chemical and pharmacophore fingerprints. The definitions of indices, related to the quality of the hierarchies in being able to distinguish between active and inactive compounds, revealed two interesting hierarchies with the Unity (1 active cluster) and pharmacophore fingerprints (4 active clusters). The results of this study also showed the importance of correct choice of metrics as well as the effectiveness of a new alternative of the Ward clustering algorithm named Energy (Minimum E-Distance method). In parallel, the relationship between these classifications and a previously defined 3D 5-HT(4) antagonist pharmacophore was established. PMID:18821249

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

    PubMed Central

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

    2015-01-01

    Fructose reacts spontaneously with proteins in the brain to form advanced glycation end products (AGE) that may elicit neuroinflammation and cause brain pathology, including Alzheimer’s disease. We investigated whether fructose is eliminated by oxidative metabolism in neocortex. Injection of [14C]fructose or its AGE-prone metabolite [14C]glyceraldehyde into rat neocortex in vivo led to formation of 14C-labeled alanine, glutamate, aspartate, GABA, and glutamine. In isolated neocortical nerve terminals, [14C]fructose labeled glutamate, GABA, and aspartate, indicating uptake of fructose into nerve terminals and oxidative fructose metabolism in these structures. Hexokinase 1, which channels fructose into glycolysis, was highly expressed, and enzyme activity was similar with fructose or glucose as substrates, whereas the fructose-specific ketohexokinase was weakly expressed. The fructose transporter Glut5 was expressed at only ~4% of the level of neuronal glucose transporter Glut3, suggesting transport across plasma membranes of brain cells as the limiting factor in removal of extracellular fructose. Fructose may be formed from glucose through the polyol pathway. The genes encoding enzymes of this pathway, aldose reductase and sorbitol dehydrogenase, were expressed in rat neocortex. We conclude that fructose is transported into neocortical cells, including nerve terminals, and that it is metabolized and thereby detoxified primarily through hexokinase activity. PMID:25708447

  9. Individual Differences in Impulsive Action Reflect Variation in the Cortical Serotonin 5-HT2A Receptor System

    PubMed Central

    Fink, Latham HL; Anastasio, Noelle C; Fox, Robert G; Rice, Kenner C; Moeller, F Gerard; Cunningham, Kathryn A

    2015-01-01

    Impulsivity is an important feature of multiple neuropsychiatric disorders, and individual variation in the degree of inherent impulsivity could play a role in the generation or exacerbation of problematic behaviors. Serotonin (5-HT) actions at the 5-HT2AR receptor (5-HT2AR) promote and 5-HT2AR antagonists suppress impulsive action (the inability to withhold premature responses; motor impulsivity) upon systemic administration or microinfusion directly into the medial prefrontal cortex (mPFC), a node in the corticostriatal circuit that is thought to play a role in the regulation of impulsive action. We hypothesized that the functional capacity of the 5-HT2AR, which is governed by its expression, localization, and protein/protein interactions (eg, postsynaptic density 95 (PSD95)), may drive the predisposition to inherent impulsive action. Stable high-impulsive (HI) and low-impulsive (LI) phenotypes were identified from an outbred rodent population with the 1-choice serial reaction time (1-CSRT) task. HI rats exhibited a greater head-twitch response following administration of the preferential 5-HT2AR agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) and were more sensitive to the effects of the selective 5-HT2AR antagonist M100907 to suppress impulsive action relative to LI rats. A positive correlation was observed between levels of premature responses and 5-HT2AR binding density in frontal cortex ([3H]-ketanserin radioligand binding). Elevated mPFC 5-HT2AR protein expression concomitant with augmented association of the 5-HT2AR with PSD95 differentiated HI from LI rats. The observed differential sensitivity of HI and LI rats to 5-HT2AR ligands and associated distinct 5-HT2AR protein profiles provide evidence that spontaneously occurring individual differences in impulsive action reflect variation in the cortical 5-HT2AR system. PMID:25666313

  10. Side effect profile of 5-HT treatments for Parkinson's disease and L-DOPA-induced dyskinesia in rats

    PubMed Central

    Lindenbach, D; Palumbo, N; Ostock, C Y; Vilceus, N; Conti, M M; Bishop, C

    2015-01-01

    BACKGROUND AND PURPOSE Treatment of Parkinson's disease (PD) with L-DOPA eventually causes abnormal involuntary movements known as dyskinesias in most patients. Dyskinesia can be reduced using compounds that act as direct or indirect agonists of the 5-HT1A receptor, but these drugs have been reported to worsen PD features and are known to produce ‘5-HT syndrome’, symptoms of which include tremor, myoclonus, rigidity and hyper-reflexia. EXPERIMENTAL APPROACH Sprague-Dawley rats were given unilateral nigrostriatal dopamine lesions with 6-hydroxydopamine. Each of the following three purportedly anti-dyskinetic 5-HT compounds were administered 15 min before L-DOPA: the full 5-HT1A agonist ±-8-hydroxy-2-dipropylaminotetralin (±8-OH-DPAT), the partial 5-HT1A agonist buspirone or the 5-HT transporter inhibitor citalopram. After these injections, animals were monitored for dyskinesia, 5-HT syndrome, motor activity and PD akinesia. KEY RESULTS Each 5-HT drug dose-dependently reduced dyskinesia by relatively equal amounts (±8-OH-DPAT ≥ citalopram ≥ buspirone), but 5-HT syndrome was higher with ±8-OH-DPAT, lower with buspirone and not present with citalopram. Importantly, with or without L-DOPA, all three compounds provided an additional improvement of PD akinesia. All drugs tempered the locomotor response to L-DOPA suggesting dyskinesia reduction, but vertical rearing was reduced with 5-HT drugs, potentially reflecting features of 5-HT syndrome. CONCLUSIONS AND IMPLICATIONS The results suggest that compounds that indirectly facilitate 5-HT1A receptor activation, such as citalopram, may be more effective therapeutics than direct 5-HT1A receptor agonists because they exhibit similar anti-dyskinesia efficacy, while possessing a reduced side effect profile. PMID:25175895

  11. Individual Differences in Impulsive Action Reflect Variation in the Cortical Serotonin 5-HT2A Receptor System.

    PubMed

    Fink, Latham H L; Anastasio, Noelle C; Fox, Robert G; Rice, Kenner C; Moeller, F Gerard; Cunningham, Kathryn A

    2015-07-01

    Impulsivity is an important feature of multiple neuropsychiatric disorders, and individual variation in the degree of inherent impulsivity could play a role in the generation or exacerbation of problematic behaviors. Serotonin (5-HT) actions at the 5-HT2AR receptor (5-HT2AR) promote and 5-HT2AR antagonists suppress impulsive action (the inability to withhold premature responses; motor impulsivity) upon systemic administration or microinfusion directly into the medial prefrontal cortex (mPFC), a node in the corticostriatal circuit that is thought to play a role in the regulation of impulsive action. We hypothesized that the functional capacity of the 5-HT2AR, which is governed by its expression, localization, and protein/protein interactions (eg, postsynaptic density 95 (PSD95)), may drive the predisposition to inherent impulsive action. Stable high-impulsive (HI) and low-impulsive (LI) phenotypes were identified from an outbred rodent population with the 1-choice serial reaction time (1-CSRT) task. HI rats exhibited a greater head-twitch response following administration of the preferential 5-HT2AR agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) and were more sensitive to the effects of the selective 5-HT2AR antagonist M100907 to suppress impulsive action relative to LI rats. A positive correlation was observed between levels of premature responses and 5-HT2AR binding density in frontal cortex ([(3)H]-ketanserin radioligand binding). Elevated mPFC 5-HT2AR protein expression concomitant with augmented association of the 5-HT2AR with PSD95 differentiated HI from LI rats. The observed differential sensitivity of HI and LI rats to 5-HT2AR ligands and associated distinct 5-HT2AR protein profiles provide evidence that spontaneously occurring individual differences in impulsive action reflect variation in the cortical 5-HT2AR system. PMID:25666313

  12. Mechanistic model for the acute effect of fluvoxamine on 5-HT and 5-HIAA concentrations in rat frontal cortex.

    PubMed

    Geldof, Marian; Freijer, Jan I; Peletier, Lambertus A; van Beijsterveldt, Ludy; Danhof, Meindert

    2008-03-01

    A mechanistic model is proposed to predict the time course of the concentrations of 5-HT and its metabolite 5-hydroxyindolacetic acid (5-HIAA) in rat frontal cortex following acute administration of SSRIs. In the model, SSRIs increase synaptic 5-HT concentrations by reversible blockade of the SERT in a direct concentration-dependent manner, while the 5-HT response is attenuated by negative feedback via 5-HT autoreceptors. In principle, the model allows for the description of oscillatory patterns in the time course of 5-HT and 5-HIAA concentrations in brain extracellular fluid. The model was applied in a pharmacokinetic-pharmacodynamic (PK/PD) investigation on the time course of the microdialysate 5-HT and 5-HIAA response in rat frontal cortex following a 30-min intravenous infusion of 3.7 and 7.3mg/kg fluvoxamine. Directly after administration of fluvoxamine, concentrations of 5-HT were increased to approximately 450-600% of baseline values while 5-HIAA concentrations were decreased. Thereafter 5-HT and 5-HIAA concentrations gradually returned to baseline values in 6-10h, respectively. The PK/PD analysis revealed that inhibition of 5-HT reuptake was directly related to the fluvoxamine concentration in plasma, with 50% inhibition of 5-HT reuptake occurring at a plasma concentration of 1.1ng/ml (EC50). The levels of 5-HT at which 50% of the inhibition of the 5-HT response was reached (IC50) amounted to 272% of baseline. The model was unable to capture the oscillatory patterns in the individual concentration time curves, which appeared to occur randomly. The proposed mechanistic model is the first step in modeling of complex neurotransmission processes. The model constitutes a useful basis for prediction of the time course of median 5-HT and 5-HIAA concentrations in the frontal cortex in behavioral pharmacology studies in vivo. PMID:18207708

  13. Gaddum and LSD: the birth and growth of experimental and clinical neuropharmacology research on 5-HT in the UK

    PubMed Central

    Green, A R

    2008-01-01

    The vasoconstrictor substance named serotonin was identified as 5-hydroxytryptamine (5-HT) by Maurice Rapport in 1949. In 1951, Rapport gave Gaddum samples of 5-HT substance allowing him to develop a bioassay to both detect and measure the amine. Gaddum and colleagues rapidly identified 5-HT in brain and showed that lysergic acid diethylamide (LSD) antagonized its action in peripheral tissues. Gaddum accordingly postulated that 5-HT might have a role in mood regulation. This review examines the role of UK scientists in the first 20 years following these major discoveries, discussing their role in developing assays for 5-HT in the CNS, identifying the enzymes involved in the synthesis and metabolism of 5-HT and investigating the effect of drugs on brain 5-HT. It reviews studies on the effects of LSD in humans, including Gaddum's self-administration experiments. It outlines investigations on the role of 5-HT in psychiatric disorders, including studies on the effect of antidepressant drugs on the 5-HT concentration in rodent and human brain, and the attempts to examine 5-HT biochemistry in the brains of patients with depressive illness. It is clear that a rather small group of both preclinical scientists and psychiatrists in the UK made major advances in our understanding of the role of 5-HT in the brain, paving the way for much of the knowledge now taken for granted when discussing ways that 5-HT might be involved in the control of mood and the idea that therapeutic drugs used to alleviate psychiatric illness might alter the function of cerebral 5-HT. PMID:18516072

  14. Differential expression of 5-HT-related genes in symptomatic pulmonary embolism patients

    PubMed Central

    Jin, Yun; Wang, Lemin; Duan, Qianglin; Gong, Zhu; Yang, Fan; Song, Yanli

    2015-01-01

    Objective: Whole human genome oligo microarrays were employed to systematically investigate the mRNA expression profile of 5-HT synthetase, transporter, receptor, and factors in 5-HT signaling pathway in peripheral blood karyocytes from pulmonary embolism (PE) patients. Methods: A total of 20 PE patients and 20 healthy subjects matched in gender and age were recruited. The human genome microarrays were performed to detect the mRNA expression profile of 5-HT synthetase, transporter, receptor, and factors in 5-HT signal pathway of two groups. The random variance model corrected t-test was used for analysis. Results: Our results showed (1) tryptophan hydroxylase (TPH1)-related gene expression was markedly down-regulated in PE patients (P < 0.01); (2) monoamine oxidases (MAO)-related gene (MAOB) expression was significantly up-regulated in PE patients (P < 0.01); (3) the expression of 17 genes of 7 5-HT receptors showed a down-regulated tendency in PE patients, and significant difference was observed in the expression of HTR1E, HTR3B, HTR4 and HTR5A between them (P < 0.05); (4) the expression of DalDAG-GEF I, Tubby, PKA and EPAC in 5-HT signal pathways was dramatically up-regulated in PE patients (P < 0.05); the expression of SPA1, RIAM, RAPL, Talin, PKC, PLC and Pyk2 was remarkably up-regulated in PE patients (P < 0.05); (5) the expression of integrin genes ITGA2B, ITGB1 and ITGB3 was significantly up-regulated in PE patients (P < 0.05). Conclusion: In PE patients, the expression of TPH1 and HTR4 was down-regulated as a negative feedback; the MAOB expression was up-regulated. Consistent with the expression of 5-HTR1E and 5-HTR4 and the abnormally activated Tubby, the expression of integrins in platelets was activated. PMID:25785024

  15. Antidepressants and antipsychotic drugs colocalize with 5-HT3 receptors in raft-like domains.

    PubMed

    Eisensamer, Brigitte; Uhr, Manfred; Meyr, Sabrina; Gimpl, Gerald; Deiml, Tobias; Rammes, Gerhard; Lambert, Jeremy J; Zieglgänsberger, Walter; Holsboer, Florian; Rupprecht, Rainer

    2005-11-01

    Despite different chemical structure and pharmacodynamic signaling pathways, a variety of antidepressants and antipsychotics inhibit ion fluxes through 5-HT3 receptors in a noncompetitive manner with the exception of the known competitive antagonists mirtazapine and clozapine. To further investigate the mechanisms underlying the noncompetitive inhibition of the serotonin-evoked cation current, we quantified the concentrations of different types of antidepressants and antipsychotics in fractions of sucrose flotation gradients isolated from HEK293 (human embryonic kidney 293) cells stably transfected with the 5-HT3A receptor and of N1E-115 neuroblastoma cells in relation to the localization of the 5-HT3 receptor protein within the cell membrane. Western blots revealed a localization of the 5-HT3 receptor protein exclusively in the low buoyant density (LBD) fractions compatible with a localization within raft-like domains. Also, the antidepressants desipramine, fluoxetine, and reboxetine and the antipsychotics fluphenazine, haloperidol, and clozapine were markedly enriched in LBD fractions, whereas no accumulation occurs for mirtazapine, carbamazepine, moclobemide, and risperidone. The concentrations of psychopharmacological drugs within LBD fractions was strongly associated with their inhibitory potency against serotonin-induced cation currents. The noncompetitive antagonism of antidepressants at the 5-HT3 receptor was not conferred by an enhancement of receptor internalization as shown by immunofluorescence studies, assessment of receptor density in clathrin-coated vesicles, and electrophysiological recordings after coexpression of a dominant-negative mutant of dynamin I, which inhibits receptor internalization. In conclusion, enrichment of antidepressants and antipsychotics in raft-like domains within the cell membrane appears to be crucial for their antagonistic effects at ligand-gated ion channels such as 5-HT3 receptors. PMID:16267227

  16. The 5-HT7 receptor as a potential target for treating drug and alcohol abuse.

    PubMed

    Hauser, Sheketha R; Hedlund, Peter B; Roberts, Amanda J; Sari, Youssef; Bell, Richard L; Engleman, Eric A

    2014-01-01

    Alcohol and drug abuse take a large toll on society and affected individuals. However, very few effective treatments are currently available to treat alcohol and drug addiction. Basic and clinical research has begun to provide some insights into the underlying neurobiological systems involved in the addiction process. Several neurotransmitter pathways have been implicated and distinct reward neurocircuitry have been proposed-including the mesocorticolimbic dopamine (MCL-DA) system and the extended amygdala. The serotonin (5-HT) neurotransmitter system is of particular interest and multiple 5-HT receptors are thought to play significant roles in alcohol and drug self-administration and the development of drug dependence. Among the 5-HT receptors, the 5-HT7 receptor is currently undergoing characterization as a potential target for the treatment of several psychiatric disorders. Although this receptor has received only limited research regarding addictive behaviors, aspects of its neuroanatomical, biochemical, physiological, pharmacological, and behavioral profiles suggest that it could play a key role in the addiction process. For instance, genomic studies in humans have suggested a link between variants in the gene encoding the 5-HT7 receptor and alcoholism. Recent behavioral testing using high-affinity antagonists in mice and preliminary tests with alcohol-preferring rats suggest that this receptor could mediate alcohol consumption and/or reinforcement and play a role in seeking/craving behavior. Interest in the development of new and more selective pharmacological agents for this receptor will aid in examining the 5-HT7 receptor as a novel target for treating addiction. PMID:25628528

  17. The 5-HT7 receptor as a potential target for treating drug and alcohol abuse

    PubMed Central

    Hauser, Sheketha R.; Hedlund, Peter B.; Roberts, Amanda J.; Sari, Youssef; Bell, Richard L.; Engleman, Eric A.

    2015-01-01

    Alcohol and drug abuse take a large toll on society and affected individuals. However, very few effective treatments are currently available to treat alcohol and drug addiction. Basic and clinical research has begun to provide some insights into the underlying neurobiological systems involved in the addiction process. Several neurotransmitter pathways have been implicated and distinct reward neurocircuitry have been proposed—including the mesocorticolimbic dopamine (MCL-DA) system and the extended amygdala. The serotonin (5-HT) neurotransmitter system is of particular interest and multiple 5-HT receptors are thought to play significant roles in alcohol and drug self-administration and the development of drug dependence. Among the 5-HT receptors, the 5-HT7 receptor is currently undergoing characterization as a potential target for the treatment of several psychiatric disorders. Although this receptor has received only limited research regarding addictive behaviors, aspects of its neuroanatomical, biochemical, physiological, pharmacological, and behavioral profiles suggest that it could play a key role in the addiction process. For instance, genomic studies in humans have suggested a link between variants in the gene encoding the 5-HT7 receptor and alcoholism. Recent behavioral testing using high-affinity antagonists in mice and preliminary tests with alcohol-preferring rats suggest that this receptor could mediate alcohol consumption and/or reinforcement and play a role in seeking/craving behavior. Interest in the development of new and more selective pharmacological agents for this receptor will aid in examining the 5-HT7 receptor as a novel target for treating addiction. PMID:25628528

  18. 5-HT7 receptor activation promotes an increase in TrkB receptor expression and phosphorylation

    PubMed Central

    Samarajeewa, Anshula; Goldemann, Lolita; Vasefi, Maryam S.; Ahmed, Nawaz; Gondora, Nyasha; Khanderia, Chandni; Mielke, John G.; Beazely, Michael A.

    2014-01-01

    The serotonin (5-HT) type 7 receptor is expressed throughout the CNS including the cortex and hippocampus. We have previously demonstrated that the application of 5-HT7 receptor agonists to primary hippocampal neurons and SH-SY5Y cells increases platelet-derived growth factor (PDGF) receptor expression and promotes neuroprotection against N-methyl-D-aspartate-(NMDA)-induced toxicity. The tropomyosin-related kinase B (TrkB) receptor is one of the receptors for brain-derived neurotrophic factor (BDNF) and is associated with neurodevelopmental and neuroprotective effects. Application of LP 12 to primary cerebral cortical cultures, SH-SY5Y cells, as well as the retinal ganglion cell line, RGC-5, increased both the expression of full length TrkB as well as its basal phosphorylation state at tyrosine 816. The increase in TrkB expression and phosphorylation was observed as early as 30 min after 5-HT7 receptor activation. In addition to full-length TrkB, kinase domain-deficient forms may be expressed and act as dominant-negative proteins toward the full length receptor. We have identified distinct patterns of TrkB isoform expression across our cell lines and cortical cultures. Although TrkB receptor expression is regulated by cyclic AMP and Gαs-coupled GPCRs in several systems, we demonstrate that, depending on the model system, pathways downstream of both Gαs and Gα12 are involved in the regulation of TrkB expression by 5-HT7 receptors. Given the number of psychiatric and degenerative diseases associated with TrkB/BDNF deficiency and the current interest in developing 5-HT7 receptor ligands as pharmaceuticals, identifying signaling relationships between these two receptors will aid in our understanding of the potential therapeutic effects of 5-HT7 receptor ligands. PMID:25426041

  19. 5-HT Obesity Medication Efficacy via POMC Activation is Maintained During Aging

    PubMed Central

    Burke, Luke K.; Doslikova, Barbora; D'Agostino, Giuseppe; Garfield, Alastair S.; Farooq, Gala; Burdakov, Denis; Low, Malcolm J.; Rubinstein, Marcelo; Evans, Mark L.; Billups, Brian

    2014-01-01

    The phenomenon commonly described as the middle-age spread is the result of elevated adiposity accumulation throughout adulthood until late middle-age. It is a clinical imperative to gain a greater understanding of the underpinnings of age-dependent obesity and, in turn, how these mechanisms may impact the efficacy of obesity treatments. In particular, both obesity and aging are associated with rewiring of a principal brain pathway modulating energy homeostasis, promoting reduced activity of satiety pro-opiomelanocortin (POMC) neurons within the arcuate nucleus of the hypothalamus (ARC). Using a selective ARC-deficient POMC mouse line, here we report that former obesity medications augmenting endogenous 5-hydroxytryptamine (5-HT) activity d-fenfluramine and sibutramine require ARC POMC neurons to elicit therapeutic appetite-suppressive effects. We next investigated whether age-related diminished ARC POMC activity therefore impacts the potency of 5-HT obesity pharmacotherapies, lorcaserin, d-fenfluramine, and sibutramine and report that all compounds reduced food intake to a comparable extent in both chow-fed young lean (3–5 months old) and middle-aged obese (12–14 months old) male and female mice. We provide a mechanism through which 5-HT anorectic potency is maintained with age, via preserved 5-HT–POMC appetitive anatomical machinery. Specifically, the abundance and signaling of the primary 5-HT receptor influencing appetite via POMC activation, the 5-HT2CR, is not perturbed with age. These data reveal that although 5-HT obesity medications require ARC POMC neurons to achieve appetitive effects, the anorectic efficacy is maintained with aging, findings of clinical significance to the global aging obese population. PMID:25051442

  20. Role of 5-HT(1A) receptors in fluoxetine-induced lordosis inhibition.

    PubMed

    Guptarak, Jutatip; Sarkar, Jhimly; Hiegel, Cindy; Uphouse, Lynda

    2010-07-01

    The selective serotonin reuptake inhibitor (SSRI), fluoxetine (Prozac(R)), is an effective antidepressant that is also prescribed for other disorders (e.g. anorexia, bulimia, and premenstrual dysphoria) that are prevalent in females. However, fluoxetine also produces sexual side effects that may lead patients to discontinue treatment. The current studies were designed to evaluate several predictions arising from the hypothesis that serotonin 1A (5-HT(1A)) receptors contribute to fluoxetine-induced sexual dysfunction. In rodent models, 5-HT(1A) receptors are potent negative modulators of female rat sexual behavior. Three distinct experiments were designed to evaluate the contribution of 5-HT(1A) receptors to the effects of fluoxetine. In the first experiment, the ability of the 5-HT(1A) receptor antagonist, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY100635), to prevent fluoxetine-induced lordosis inhibition was examined. In the second experiment, the effects of prior treatment with fluoxetine on the lordosis inhibitory effect of the 5-HT(1A) receptor agonist, (+/-)-8-hydroxy-2-(dipropylamino)tetralin (8-OH-DPAT), were studied. In the third experiment, the ability of progesterone to reduce the acute response to fluoxetine was evaluated. WAY100635 attenuated the effect of fluoxetine; prior treatment with fluoxetine decreased 8-OH-DPAT's potency in reducing lordosis behavior; and progesterone shifted fluoxetine's dose-response curve to the right. These findings are consistent with the hypothesis that 5-HT(1A) receptors contribute to fluoxetine-induced sexual side effects. PMID:20223238

  1. [Design, synthesis and 5-HT/NE dual reuptake inhibitory activity of aromatic heterocyclic arylamidine derivatives].

    PubMed

    Wen, Hui; Yang, Jing; Zhang, Jian-jun; Wang, Ya-fang; Ji, Cheng-xue; Yang, Guang-zhong

    2009-03-01

    Based on the pharmacophore information and the analysis of structure-activity relationship of SSRIs and SNRIs, a series of substituted aromatic heterocyclic arylamidine derivatives were designed and synthesized in order to search for lead compounds with dual activity. All of them were new compounds, and their structures were confirmed by 1H NMR and HRMS. Preliminary in vitro pharmacological tests showed that all target compounds exhibited 5-HT reuptake inhibitory activity and some compounds exhibited NE reuptake inhibitory activity. These aromatic heterocyclic arylamidine designed can be further optimized for finding more potent 5-HT/NE dual reuptake inhibitors and antidepressant candidates as well. PMID:19449528

  2. Compositions and methods related to serotonin 5-HT1A receptors

    DOEpatents

    Mukherjee, Jogeshwar; Saigal, Neil

    2010-06-08

    Contemplated substituted arylpiperazinyl compounds, and most preferably 18F-Mefway, exhibit desirable in vitro and in vivo binding characteristics to the 5-HT1A receptor. Among other advantageous parameters, contemplated compounds retain high binding affinity, display optimal lipophilicity, and are radiolabeled efficiently with 18F-fluorine in a single step. Still further, contemplated compounds exhibit high target to non-target ratios in receptor-rich regions both in vitro and in vivo, and selected compounds can be effectively and sensitively displaced by serotonin, thus providing a quantitative tool for measuring 5-HT1A receptors and serotonin concentration changes in the living brain.

  3. Compositions and methods related to serotonin 5-HT1A receptors

    DOEpatents

    Mukherjee, Jogeshwar; Saigal, Neil; Saigal, legal representative, Harsh

    2012-09-25

    Contemplated substituted arylpiperazinyl compounds, and most preferably 18F-Mefway, exhibit desirable in vitro and in vivo binding characteristics to the 5-HT1A receptor. Among other advantageous parameters, contemplated compounds retain high binding affinity, display optimal lipophilicity, and are radiolabeled efficiently with 18F-fluorine in a single step. Still further, contemplated compounds exhibit high target to non-target ratios in receptor-rich regions both in vitro and in vivo, and selected compounds can be effectively and sensitively displaced by serotonin, thus providing a quantitative tool for measuring 5-HT1A receptors and serotonin concentration changes in the living brain.

  4. Prostaglandin potentiates 5-HT responses in stomach and ileum innervating visceral afferent sensory neurons

    SciTech Connect

    Kim, Sojin; Jin, Zhenhua; Lee, Goeun; Park, Yong Seek; Park, Cheung-Seog; Jin, Young-Ho

    2015-01-02

    Highlights: • Prostaglandin E2 (PGE{sub 2}) effect was tested on visceral afferent neurons. • PGE{sub 2} did not evoke response but potentiated serotonin (5-HT) currents up to 167%. • PGE{sub 2}-induced potentiation was blocked by E-prostanoid type 4 receptors antagonist. • PGE{sub 2} effect on 5-HT response was also blocked by protein kinase A inhibitor KT5720. • Thus, PGE{sub 2} modulate visceral afferent neurons via synergistic signaling with 5-HT. - Abstract: Gastrointestinal disorder is a common symptom induced by diverse pathophysiological conditions that include food tolerance, chemotherapy, and irradiation for therapy. Prostaglandin E{sub 2} (PGE{sub 2}) level increase was often reported during gastrointestinal disorder and prostaglandin synthetase inhibitors has been used for ameliorate the symptoms. Exogenous administration of PGE{sub 2} induces gastrointestinal disorder, however, the mechanism of action is not known. Therefore, we tested PGE{sub 2} effect on visceral afferent sensory neurons of the rat. Interestingly, PGE{sub 2} itself did not evoked any response but enhanced serotonin (5-HT)-evoked currents up to 167% of the control level. The augmented 5-HT responses were completely inhibited by a 5-HT type 3 receptor antagonist, ondansetron. The PGE{sub 2}-induced potentiation were blocked by a selective E-prostanoid type4 (EP{sub 4}) receptors antagonist, L-161,982, but type1 and 2 receptor antagonist AH6809 has no effect. A membrane permeable protein kinase A (PKA) inhibitor, KT5720 also inhibited PGE{sub 2} effects. PGE{sub 2} induced 5-HT current augmentation was observed on 15% and 21% of the stomach and ileum projecting neurons, respectively. Current results suggest a synergistic signaling in visceral afferent neurons underlying gastrointestinal disorder involving PGE{sub 2} potentiation of 5-HT currents. Our findings may open a possibility for screen a new type drugs with lower side effects than currently using steroidal prostaglandin

  5. Oligomer size of the serotonin 5-hydroxytryptamine 2C (5-HT2C) receptor revealed by fluorescence correlation spectroscopy with photon counting histogram analysis: evidence for homodimers without monomers or tetramers.

    PubMed

    Herrick-Davis, Katharine; Grinde, Ellinor; Lindsley, Tara; Cowan, Ann; Mazurkiewicz, Joseph E

    2012-07-01

    Fluorescence correlation spectroscopy (FCS) and photon counting histogram (PCH) are techniques with single molecule sensitivity that are well suited for examining the biophysical properties of protein complexes in living cells. In the present study, FCS and PCH were applied to determine the diffusion coefficient and oligomeric size of G-protein-coupled receptors. FCS was used to record fluctuations in fluorescence intensity arising from fluorescence-tagged 5-hydroxytryptamine 2C (5-HT(2C)) receptors diffusing within the plasma membrane of HEK293 cells and rat hippocampal neurons. Autocorrelation analysis yielded diffusion coefficients ranging from 0.8 to 1.2 μm(2)/s for fluorescence-tagged receptors. Because the molecular brightness of a fluorescent protein is directly proportional to the number of fluorescent proteins traveling together within a protein complex, it can be used to determine the oligomeric size of the protein complex. FCS and PCH analysis of fluorescence-tagged 5-HT(2C) receptors provided molecular brightness values that were twice that of GFP and YFP monomeric controls, similar to a dimeric GFP control, and unaltered by 5-HT. Bimolecular fluorescence complementation of the N- and C-terminal halves of YFP attached to 5-HT(2C) receptors was observed in endoplasmic reticulum/Golgi and plasma membranes with a brightness equal to monomeric YFP. When GFP-tagged 5-HT(2C) receptors were co-expressed with a large excess of untagged, non-fluorescent 5-HT(2C) receptors, the molecular brightness was reduced by half. PCH analysis of the FCS data were best described by a one-component dimer model without monomers or tetramers. Therefore, it is concluded that 5-HT(2C) receptors freely diffusing within the plasma membrane are dimeric. PMID:22593582

  6. Mechanism of action of ATP on canine pulmonary vagal C fibre nerve terminals.

    PubMed Central

    Pelleg, A; Hurt, C M

    1996-01-01

    1. The effects of extracellular adenosine 5'-triphosphate (ATP) on pulmonary vagal afferent fibres (n = 46) was studied in a canine model in vivo (n = 38). 2. ATP (3-6 mumol kg-1), administered as a rapid bolus into the right atrium, elicited a transient burst of action potentials in cervical vagal fibres, which was not affected by either blockade of ganglionic transmission (hexamethonium) or a drop in arterial blood pressure (nitroglycerine). 3. The fibres with ATP-sensitive terminals were otherwise quiescent with no activity related to either cardiac or respiratory cycles and their conduction velocity was 0.85 +/- 0.13 m s-1 (n = 7). 4. Inflation of the lungs to 2-3 times the tidal volume triggered brief bursts of action potentials in these fibres. 5. Capsaicin (10 micrograms kg-1), given as a rapid bolus into the right atrium, elicited a burst of action potentials in these ATP-sensitive fibres. 6. Smaller amounts of ATP and capsaicin (0.5-3 mumol kg-1 and 1-5 micrograms kg-1, respectively) had similar effects when the two compounds were given into the right pulmonary artery. 7. Adenosine, adenosine 5'-monophosphate, or adenosine 5'-diphosphate did not excite these fibres (n = 30). 8. The non-degradable analogue of ATP alpha,beta-methylene ATP (alpha,beta-mATP) was tenfold more potent than ATP while beta,gamma-methylene ATP (beta,gamma-mATP) was in active. 9. The selective P2x-purinoceptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid markedly attenuated the effect of ATP but not of capsaicin. The P2Y-purinoceptor antagonist Reactive Blue 2 was without effect. 10. Pretreatment with pertussis toxin (PTX) did not affect this action of ATP. 11. In the canine lungs ATP activates vagal C fibre nerve terminals. This action is mediated by P2X-purinoceptors and is independent of a PTX-sensitive guanine nucleotide binding protein (G protein). PMID:8745294

  7. 5-HT2C Receptor Desensitization Moderates Anxiety in 5-HTT Deficient Mice: From Behavioral to Cellular Evidence

    PubMed Central

    Martin, Cédric BP; Martin, Vincent S.; Trigo, José M.; Chevarin, Caroline; Maldonado, Rafael; Fink, Latham H.; Cunningham, Kathryn A.; Hamon, Michel; Lanfumey, Laurence

    2015-01-01

    Background: Desensitization and blockade of 5-HT2C receptors (5-HT2CR) have long been thought to be central in the therapeutic action of antidepressant drugs. However, besides behavioral pharmacology studies, there is little in vivo data documenting antidepressant-induced 5-HT2CR desensitization in specific brain areas. Methods: Mice lacking the 5-HT reuptake carrier (5-HTT-/-) were used to model the consequences of chronic 5-HT reuptake inhibition with antidepressant drugs. The effect of this mutation on 5-HT2CR was evaluated at the behavioral (social interaction, novelty-suppressed feeding, and 5-HT2CR–induced hypolocomotion tests), the neurochemical, and the cellular (RT-qPCR, mRNA editing, and c-fos–induced expression) levels. Results: Although 5-HTT-/- mice had an anxiogenic profile in the novelty-suppressed feeding test, they displayed less 5-HT2CR–mediated anxiety in response to the agonist m-chlorophenylpiperazine in the social interaction test. In addition, 5-HT2CR–mediated inhibition of a stress-induced increase in 5-HT turnover, measured in various brain areas, was markedly reduced in 5-HTT-/- mutants. These indices of tolerance to 5-HT2CR stimulation were associated neither with altered levels of 5-HT2CR protein and mRNA nor with changes in pre-mRNA editing in the frontal cortex. However, basal c-fos mRNA production in cells expressing 5-HT2CR was higher in 5-HTT-/- mutants, suggesting an altered basal activity of these cells following sustained 5-HT reuptake carrier inactivation. Furthermore, the increased c-fos mRNA expression in 5-HT2CR–like immune-positive cortical cells observed in wild-type mice treated acutely with the 5-HT2CR agonist RO-60,0175 was absent in 5-HTT-/- mutants. Conclusions: Such blunted responsiveness of the 5-HT2CR system, observed at the cell signaling level, probably contributes to the moderation of the anxiety phenotype in 5-HTT-/- mice. PMID:25522398

  8. Inhibition of native 5-HT3 receptor-evoked contractions in guinea pig and mouse ileum by antimalarial drugs.

    PubMed

    Kelley, Stephen P; Walsh, Jacqueline; Kelly, Mark C; Muhdar, Simerjyot; Adel-Aziz, Mohammed; Barrett, Iain D; Wildman, Scott S

    2014-09-01

    Quinine, chloroquine and mefloquine are commonly used to treat malaria, however, with associated gastrointestinal (GI) side-effects. These drugs act as antagonists at recombinant 5-HT3 receptors and modulate gut peristalsis. These gastrointestinal side effects may be the result of antagonism at intestinal 5-HT3 receptors. Ileum from male C57BL/6 mice and guinea pigs was mounted longitudinally in organ baths. The concentration-response curves for 5-HT and the selective 5-HT3 agonist 2-Me-5-HT were obtained with 5-HT (pEC50 = 7.57 ± 0.33, 12) more potent (P = 0.004) than 2-Me-5-HT (pEC50 = 5.45 ± 0.58, n = 5) in mouse ileum. There was no difference in potency of 5-HT (pEC50 = 5.42 ± 0.15, n = 8) and 2-Me-5-HT (pIC50 = 5.01 ± 0.55, n = 11) in guinea pig ileum (P > 0.05). Quinine, chloroquine or mefloquine was applied for 10 min and inhibitions prior to submaximal agonist application. In mouse ileum, quinine, chloroquine and mefloquine antagonised 5-HT-induced contractions (pIC50 = 4.9 ± 0.17, n = 7; 4.76 ± 0.14, n = 5; 6.21 ± 0.2, n = 4, correspondingly) with mefloquine most potent (P < 0.05). Quinine, chloroquine and mefloquine antagonised 2-me-5-HT-induced contractions (pIC50 = 6.35 ± 0.11, n = 8; 4.64 ± 0.2, n = 7; 5.11 ± 0.22, n = 6, correspondingly) with quinine most potent (P < 0.05). In guinea-pig ileum, quinine, chloroquine and mefloquine antagonised 5-HT-induced contractions (pIC50 = 5.02 ± 0.15, n = 6; 4.54 ± 0.1, n = 7; 5.32 ± 0.13, n = 5) and 2-me-5-HT-induced contractions (pIC50 = 4.62 ± 0.25, n = 5; 4.56 ± 0.14, n = 6; 5.67 ± 0.12, n = 4) with chloroquine least potent against 5-HT and mefloquine most potent against 2-me-5-HT (P < 0.05). These results support previous studies identifying anti-malarial drugs as antagonists at recombinant 5-HT3 receptors and may also demonstrate the ability of these drugs to influence native 5-HT3 receptor-evoked contractile responses which may account for their associated GI side-effects. PMID:24886883

  9. Brain-derived neurotrophic factor facilitates in vivo internalization of tetanus neurotoxin C-terminal fragment fusion proteins in mature mouse motor nerve terminals.

    PubMed

    Roux, Sylvie; Saint Cloment, Cécile; Curie, Thomas; Girard, Emmanuelle; Miana Mena, Francisco-Javier; Barbier, Julien; Osta, Rosario; Molgó, Jordi; Brûlet, Philippe

    2006-09-01

    In a previous study it was reported that fusion proteins composed of the atoxic C-terminal fragment of tetanus toxin (TTC) and green fluorescent protein or beta-galactosidase (GFP-TTC and beta-gal-TTC, respectively) rapidly cluster at motor nerve terminals of the mouse neuromuscular junction (NMJ). Because this traffic involves presynaptic activity, probably via the secretion of active molecules, we examined whether it is affected by brain-derived neurotrophic factor (BDNF). Quantitative confocal microscopy and a fluorimetric assay for beta-gal activity revealed that co-injecting BDNF and the fusion proteins significantly increased the kinetics and amount of the proteins' localization at the NMJ and their internalization by motor nerve terminals. The observed increases were independent of synaptic vesicle recycling because BDNF did not affect spontaneous quantal acetylcholine release. In addition, injecting anti-BDNF antibody shortly before injecting GFP-TTC, and before co-injecting GFP-TTC and BDNF, significantly reduced the fusion protein's localization at the NMJ. Co-injecting GFP-TTC with neurotrophin-4 (NT-4) or glial-derived neurotrophic factor (GDNF), but not with nerve growth factor, neurotrophin-3 or ciliary neurotrophic factor, also significantly increased the fusion protein's localization at the NMJ. Thus, TTC probes may use for their neuronal internalization endocytic pathways normally stimulated by BDNF, NT-4 and GDNF binding. Different tyrosine kinase receptors with similar signalling pathways are activated by BDNF/NT-4 and GDNF binding. Thus, activated components of these signalling pathways may be involved in the TTC probes' internalization, perhaps by facilitating localization of receptors of TTC in specific membrane microdomains or by recruiting various factors needed for internalization of TTC. PMID:17004918

  10. Regulatory role of a neurotransmitter (5-HT) on glial Na+/K(+)-ATPase in the rat brain.

    PubMed

    Mercado, R; Hernández, J

    1992-07-01

    In the present work we studied the effect of serotonin (5-HT) on the kinetics of Na+/K(+)-ATPase in subcellular preparations of the cerebral cortex from male Wistar rats using various concentrations of ATP and K+ with and without added 5-HT. Also we studied the effect of 5-HT on the enzyme in glial or neuronal preparations. The results indicated that there was a significant increase (P < 0.05) of the Vmax in the presence of 5-HT in the whole tissue preparation (homogenate) but not in the subcellular fractions, suggesting that the interaction could be preferentially with the glial pump. Further results supported that this was the case since activation by 5-HT was mainly in the glial preparations. Kinetic data and the binding of [3H]ouabain supported that the enzyme is activated by 5-HT through the exposure of more enzymatic active sites. PMID:1303137

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

    PubMed Central

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

    2007-01-01

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

  12. Optical Monitoring of Living Nerve Terminal Labeling in Hair Follicle Lanceolate Endings of the Ex Vivo Mouse Ear Skin.

    PubMed

    Bewick, Guy S; Banks, Robert W

    2016-01-01

    A novel dissection and recording technique is described for optical monitoring staining and de-staining of lanceolate terminals surrounding hair follicles in the skin of the mouse pinna. The preparation is simple and relatively fast, reliably yielding extensive regions of multiple labeled units of living nerve terminals to study uptake and release of styryl pyridinium dyes extensively used in studies of vesicle recycling. Subdividing the preparations before labeling allows test vs. control comparisons in the same ear from a single individual. Helpful tips are given for improving the quality of the preparation, the labeling and the imaging parameters. This new system is suitable for assaying pharmacologically and mechanically-induced uptake and release of these vital dyes in lanceolate terminals in both wild-type and genetically modified animals. Examples of modulatory influences on labeling intensity are given. PMID:27077818

  13. Optical Monitoring of Living Nerve Terminal Labeling in Hair Follicle Lanceolate Endings of the Ex Vivo Mouse Ear Skin

    PubMed Central

    Bewick, Guy S.; Banks, Robert W.

    2016-01-01

    A novel dissection and recording technique is described for optical monitoring staining and de-staining of lanceolate terminals surrounding hair follicles in the skin of the mouse pinna. The preparation is simple and relatively fast, reliably yielding extensive regions of multiple labeled units of living nerve terminals to study uptake and release of styryl pyridinium dyes extensively used in studies of vesicle recycling. Subdividing the preparations before labeling allows test vs. control comparisons in the same ear from a single individual. Helpful tips are given for improving the quality of the preparation, the labeling and the imaging parameters. This new system is suitable for assaying pharmacologically and mechanically-induced uptake and release of these vital dyes in lanceolate terminals in both wild-type and genetically modified animals. Examples of modulatory influences on labeling intensity are given. PMID:27077818

  14. Functional expression of 5-HT{sub 2A} receptor in osteoblastic MC3T3-E1 cells

    SciTech Connect

    Hirai, Takao; Kaneshige, Kota; Kurosaki, Teruko; Nishio, Hiroaki

    2010-05-28

    In the previous study, we reported the gene expression for proteins related to the function of 5-hydroxytryptamine (5-HT, serotonin) and elucidated the expression patterns of 5-HT{sub 2} receptor subtypes in mouse osteoblasts. In the present study, we evaluated the possible involvement of 5-HT receptor subtypes and its inactivation system in MC3T3-E1 cells, an osteoblast cell line. DOI, a 5-HT{sub 2A} and 5-HT{sub 2C} receptor selective agonist, as well as 5-HT concentration-dependently increased proliferative activities of MC3T3-E1 cells in their premature period. This effect of 5-HT on cell proliferation were inhibited by ketanserin, a 5-HT{sub 2A} receptor specific antagonist. Moreover, both DOI-induced cell proliferation and phosphorylation of ERK1 and 2 proteins were inhibited by PD98059 and U0126, selective inhibitors of MEK in a concentration-dependent manner. Furthermore, treatment with fluoxetine, a 5-HT specific re-uptake inhibitor which inactivate the function of extracellular 5-HT, significantly increased the proliferative activities of MC3T3-E1 cells in a concentration-dependent manner. Our data indicate that 5-HT fill the role for proliferation of osteoblast cells in their premature period. Notably, 5-HT{sub 2A} receptor may be functionally expressed to regulate mechanisms underlying osteoblast cell proliferation, at least in part, through activation of ERK/MAPK pathways in MC3T3-E1 cells.

  15. Antidepressant-like activity of Tagetes lucida Cav. is mediated by 5-HT(1A) and 5-HT(2A) receptors.

    PubMed

    Bonilla-Jaime, H; Guadarrama-Cruz, G; Alarcon-Aguilar, F J; Limón-Morales, O; Vazquez-Palacios, G

    2015-10-01

    It has been demonstrated that the aqueous extract of Tagetes lucida Cav. shows an antidepressant-like effect on the forced swimming test (FST) in rats. The aim of this study was to analyze the participation of the serotoninergic system in the antidepressant-like effect of the aqueous extract of T. lucida. Different doses of the extract of T. lucida were administered at 72, 48, 24, 18 and 1 h before FST. The animals were pretreated with a 5-HT1A receptor antagonist (WAY-100635, 0.5 mg/kg), a 5-HT2A receptor antagonist (ketanserin, 5 mg/kg), a β-noradrenergic receptor antagonist (propranolol, 200 mg/kg), and with a α2-noradrenergic receptor antagonist (yohimbine, 1 mg/kg) alone or combined with the extract and pretreated with a serotonin synthesis inhibitor (PCPA) before treatment with 8-OH-DPAT + the extract of T. lucida. In addition, suboptimal doses of the 5-HT1A agonist (8-OH-DPAT) + non-effective dose of extract was analyzed in the FST. To determine the presence of flavonoids, the aqueous extract of T. lucida (20 µl, 4 mg/ml) was injected in HPLC; however, a quercetin concentration of 7.72 mg/g of extract weight was detected. A suboptimal dose of 8-OH-DPAT + extract of T. lucida decreased immobility and increased swimming and climbing. An antidepressant-like effect with the aqueous extract of T. lucida at doses of 100 and 200 mg/kg was observed on the FST with decreased immobility behavior and increased swimming; however, this effect was blocked by WAY-100635, ketanserin and PCPA but not by yohimbine and propranolol, suggesting that the extract of T. lucida could be modulating the release/reuptake of serotonin. PMID:26062718

  16. Discovery and pharmacological profile of new hydrophilic 5-HT(4) receptor antagonists.

    PubMed

    Brudeli, Bjarne; Navaratnarajah, Mirusha; Andressen, Kjetil Wessel; Manfra, Ornella; Moltzau, Lise Román; Nilsen, Nils Olav; Levy, Finn Olav; Klaveness, Jo

    2014-09-15

    The synthesis and pharmacological data of some new and potent hydrophilic 5-HT4 receptor antagonists are described. Propanediol derivative 25 was identified as a potent antagonist with low affinity for the hERG potassium channel and promising pharmacokinetics. PMID:25149506

  17. Genetic depletion of brain 5HT reveals a common molecular pathway mediating compulsivity and impulsivity

    PubMed Central

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

    2012-01-01

    Neuropsychiatric disorders characterized by behavioral disinhibition, including disorders of compulsivity (e.g., obsessive-compulsive disorder; OCD) and impulse-control (e.g., impulsive aggression), are severe, highly prevalent and chronically disabling. Treatment options for these diseases are extremely limited. The pathophysiological bases of disorders of behavioral disinhibition are poorly understood but it has been suggested that serotonin dysfunction may play a role. Mice lacking the gene encoding brain tryptophan hydroxylase 2 (Tph2−/−), the initial and rate-limiting enzyme in the synthesis of serotonin, were tested in numerous behavioral assays that are well known for their utility in modeling human neuropsychiatric diseases. Mice lacking Tph2 (and brain 5HT) show intense compulsive and impulsive behaviors to include extreme aggression. The impulsivity is motor in form and not cognitive because Tph2−/− mice show normal acquisition and reversal learning on a spatial learning task. Restoration of 5HT levels by treatment of Tph2−/− mice with its immediate precursor 5-hydroxytryptophan attenuated compulsive and impulsive-aggressive behaviors. Surprisingly, in Tph2−/− mice, the lack of 5HT was not associated with anxiety-like behaviors. The results indicate that 5HT mediates behavioral disinhibition in the mammalian brain independent of anxiogenesis. PMID:22443164

  18. Serotomide and Safflomide Modulate Forskolin-Stimulated cAMP Formation via 5-HT1 Receptor

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Serotomide (N-caffeoylserotonin) and safflomide (N-caffeoyltryptamine) are serotonin-derived phenylpropenoid amides found in plants. In this paper, safflomide and serotomide were investigated to determine their effects on serotonin receptor 5-HT1 in the renal epithelial (OK) cells, due to their stru...

  19. Spatial memory deficit across aging: current insights of the role of 5-HT7 receptors

    PubMed Central

    Beaudet, Gregory; Bouet, Valentine; Jozet-Alves, Christelle; Schumann-Bard, Pascale; Dauphin, François; Paizanis, Eleni; Boulouard, Michel; Freret, Thomas

    2015-01-01

    Elderly persons often face biological, psychological or social changes over time that may cause discomfort or morbidity. While some cognitive domains remain stable over time, others undergo a decline. Spatial navigation is a complex cognitive function essential for independence, safety and quality of life. While egocentric (body-centered) navigation is quite preserved during aging, allocentric (externally-centered) navigation—based on a cognitive map using distant landmarks—declines with age. Recent preclinical studies showed that serotonergic 5-HT7 receptors are localized in brain regions associated with allocentric spatial navigation processing. Behavioral assessments with pharmacological or genetic tools have confirmed the role of 5-HT7 receptors in allocentric navigation. Moreover, few data suggested a selective age-related decrease in the expression of 5-HT7 receptors in pivotal brain structures implicated in allocentric navigation such as the hippocampal CA3 region. We aim to provide a short overview of the potential role of 5-HT7 receptors in spatial navigation, and to argue for their interests as therapeutic targets against age-related cognitive decline. PMID:25642173

  20. Mapping of the serotonin 5-HT{sub 1D{beta}} autoreceptor gene on chromosome 6 and direct analysis for sequence variants

    SciTech Connect

    Lappalainen, J.; Dean, M.; Virkkunen, M.

    1995-04-24

    Abnormal brain serotonin function may be characteristic of several neuropsychiatric disorders. Thus, it is important to identify polymorphic genes and screen for functional variants at loci coding for genes that control normal serotonin functions. 5-HT{sub 1D{beta}} is a terminal serotonin autoreceptor which may play a role in regulating serotonin synthesis and release. Using an SSCP technique we screened for 5-HT{sub 1D{beta}} coding sequence variants in psychiatrically interviewed populations, which included controls, alcoholics, and alcoholic arsonists and alcoholic violent offenders with low CSF concentrations of the main serotonin metabolite 5-HIAA. A common polymorphism was identified in the 5-HT{sub 1D{beta}} gene with allele frequencies of 0.72 and 0.28. The SSCP variant was caused by a silent G to C substitution at nucleotide 861 of the coding region. This polymorphism could also be detected as a HincII RFLP of amplified DNA. DNAs from informative CEPH families were typed for the HincII RFLP and analyzed with respect to 20 linked markers on chromosome 6. Multipoint analysis placed the 5-HT{sub 1D{beta}} receptor gene between markers D6S286 and D6S275. A maximum two-point lod score of 10.90 was obtained to D6S26, which had been previously localized on 6q14-15. Chromosomal aberrations involving this region have been previously shown to cause retinal anomalies, developmental delay, and abnormal brain development. This region also contains the gene for North Carolina-type macular dystrophy. 34 refs., 3 figs., 1 tab.

  1. Modulatory effect of the 5-HT1A agonist buspirone and the mixed non-hallucinogenic 5-HT1A/2A agonist ergotamine on psilocybin-induced psychedelic experience.

    PubMed

    Pokorny, Thomas; Preller, Katrin H; Kraehenmann, Rainer; Vollenweider, Franz X

    2016-04-01

    The mixed serotonin (5-HT) 1A/2A/2B/2C/6/7 receptor agonist psilocybin dose-dependently induces an altered state of consciousness (ASC) that is characterized by changes in sensory perception, mood, thought, and the sense of self. The psychological effects of psilocybin are primarily mediated by 5-HT2A receptor activation. However, accumulating evidence suggests that 5-HT1A or an interaction between 5-HT1A and 5-HT2A receptors may contribute to the overall effects of psilocybin. Therefore, we used a double-blind, counterbalanced, within-subject design to investigate the modulatory effects of the partial 5-HT1A agonist buspirone (20mg p.o.) and the non-hallucinogenic 5-HT2A/1A agonist ergotamine (3mg p.o.) on psilocybin-induced (170 µg/kg p.o.) psychological effects in two groups (n=19, n=17) of healthy human subjects. Psychological effects were assessed using the Altered State of Consciousness (5D-ASC) rating scale. Buspirone significantly reduced the 5D-ASC main scale score for Visionary Restructuralization (VR) (p<0.001), which was mostly driven by a reduction of the VR item cluster scores for elementary and complex visual hallucinations. Further, buspirone also reduced the main scale score for Oceanic Boundlessness (OB) including derealisation and depersonalisation phenomena at a trend level (p=0.062), whereas ergotamine did not show any effects on the psilocybin-induced 5D-ASC main scale scores. The present finding demonstrates that buspirone exerts inhibitory effects on psilocybin-induced effects, presumably via 5-HT1A receptor activation, an interaction between 5-HT1A and 5-HT2A receptors, or both. The data suggest that the modulation of 5-HT1A receptor activity may be a useful target in the treatment of visual hallucinations in different psychiatric and neurological diseases. PMID:26875114

  2. Modulation of cannabinoid signaling by hippocampal 5-HT4 serotonergic system in fear conditioning.

    PubMed

    Nasehi, Mohammad; Farrahizadeh, Maryam; Ebrahimi-Ghiri, Mohaddeseh; Zarrindast, Mohammad-Reza

    2016-09-01

    Behavioral studies have suggested a key role for the cannabinoid system in the modulation of conditioned fear memory. Likewise, much of the literature has revealed that the serotonergic system affects Pavlovian fear conditioning and extinction. A high level of functional overlap between the serotonin and cannabinoid systems has also been reported. To clarify the interaction between the hippocampal serotonin (5-HT4) receptor and the cannabinoid CB1 receptor in the acquisition of fear memory, the effects of 5-HT4 agents, arachidonylcyclopropylamide (ACPA; CB1 receptor agonist), and the combined use of these drugs on fear learning were studied in a fear conditioning task in adult male NMRI mice. Pre-training intraperitoneal administration of ACPA (0.1 mg/kg) decreased the percentage of freezing time in both context- and tone-dependent fear conditions, suggesting impairment of the acquisition of fear memory. Pre-training, intra-hippocampal (CA1) microinjection of RS67333, a 5-HT4 receptor agonist, at doses of 0.1 and 0.2 or 0.2 µg/mouse impaired contextual and tone fear memory, respectively. A subthreshold dose of RS67333 (0.005 µg/mouse) did not alter the ACPA response in either condition. Moreover, intra-CA1 microinjection of RS23597 as a 5-HT4 receptor antagonist did not alter context-dependent fear memory acquisition, but it did impair tone-dependent fear memory acquisition. However, a subthreshold dose of the RS23597 (0.01 µg/mouse) potentiated ACPA-induced fear memory impairment in both conditions. Therefore, we suggest that the blockade of hippocampal 5-HT4 serotonergic system modulates cannabinoid signaling induced by the activation of CB1 receptors in conditioned fear. PMID:27296273

  3. Activation of 5-HT3 receptors leads to altered responses 6 months after MDMA treatment.

    PubMed

    Gyongyosi, Norbert; Balogh, Brigitta; Katai, Zita; Molnar, Eszter; Laufer, Rudolf; Tekes, Kornelia; Bagdy, Gyorgy

    2010-03-01

    The recreational drug "Ecstasy" [3,4-methylenedioxymethamphetamine (MDMA)] has a well-characterised neurotoxic effect on the 5-hydroxytryptamine (5-HT) neurons in animals. Despite intensive studies, the long-term functional consequencies of the 5-HT neurodegeneration remains elusive. The aim of this study was to investigate whether any alteration of 5-hydroxytryptamine-3 (5-HT(3)) receptor functions on the sleep-wake cycle, motor activity, and quantitative EEG could be detected 6 months after a single dose of 15 mg/kg of MDMA. The selective 5-HT(3) receptor agonist m-chlorophenylbiguanide (mCPBG; 1 mg/kg, i.p.) or vehicle was administered to freely moving rats pre-treated with MDMA (15 mg/kg, i.p.) or vehicle 6 months earlier. Polysomnographic and motor activity recordings were performed. Active wake (AW), passive wake (PW), light slow wave sleep (SWS-1), deep slow wave sleep (SWS-2), and paradoxical sleep were classified. In addition, EEG power spectra were calculated for the second hour after mCPBG treatment for each stage. AW increased and SWS-1 decreased in the second hour after mCPBG treatment in control animals. mCPBG caused significant changes in the EEG power in states with cortical activation (AW, PW, paradoxical sleep). In addition, mCPBG had a biphasic effect on hippocampal theta power in AW with a decrease in 7 Hz and a stage-selective increase in the upper range (8-9 Hz). Effects of mCPBG on the time spent in AW and SWS-1 were eliminated or reduced in MDMA-treated animals. In addition, mCPBG did not increase the upper theta power of AW in rats pre-treated with MDMA. These data suggest long-term changes in 5-HT(3) receptor function after MDMA. PMID:20052506

  4. Role of maternal 5-HT1A receptor in programming offspring emotional and physical development

    PubMed Central

    van Velzen, Annelies; Toth, Miklos

    2010-01-01

    Serotonin1A receptor (5-HT1AR) deficiency has been associated with anxiety and depression and mice with genetic receptor inactivation exhibit heightened anxiety. We have reported that 5-HT1AR is not only a genetic but also a maternal “environmental” factor in the development of anxiety in Swiss-Webster mice. Here we tested if the emergence of maternal genotype dependent adult anxiety is preceded by early behavioral abnormalities or if it is manifested following a normal emotional development. Pups born to null or heterozygote mothers had significantly reduced ultrasonic vocalization between postnatal day (P) 4 and 12 indicating an influence of the maternal genotype. The offspring’s own genotype had an effect limited to P4. Furthermore, we observed reduced weight gain in the null offspring of null but not heterozygote mothers indicating that a complete maternal receptor deficiency compromises offspring physical development. Except a short perinatal deficit during the dark period, heterozygote females displayed normal maternal behavior which, with the early appearance of ultrasonic vocalization deficit, suggests a role for 5-HT1AR during pre/perinatal development. Consistent with this notion, adult anxiety in the offspring is determined during the pre/perinatal period. In contrast to heterozygote females, null mothers exhibited impaired pup retrieval and nest building that may explain the reduced weight gain of their offspring. Taken together, our data indicate an important role for the maternal 5-HT1AR in regulating offspring emotional and physical development. Since reduced receptor binding has been reported in depression, including postpartum depression, reduced 5-HT1AR function in mothers may influence the emotional development of their offspring. PMID:20633050

  5. Characterization and distribution of putative 5-ht7 receptors in guinea-pig brain.

    PubMed Central

    To, Z. P.; Bonhaus, D. W.; Eglen, R. M.; Jakeman, L. B.

    1995-01-01

    1. In the presence of (-)-cyanopindolol (1.0 microM) and sumatriptan (1.0 microM), 0.5 nM [3H]-carboxamidotrytamine ([3H]-5-CT) labelled a single population of receptors in guinea-pig cerebral cortex membranes. 2. 5-HT-displaceable binding was rapid, saturable and reversible. A high affinity binding site was characterized both by equilibrium saturation (Kd = 0.76 +/- 0.28 nM; Bmax = 68.1 +/- 26.7 fmol mg-1 protein) and kinetic (Kd = 0.18 +/- 0.05 nM) analysis. The pharmacological profile of this site was similar to the profile obtained in transfected CHO-K1 cells expressing guinea-pig 5-ht7 receptors. 3. Autoradiographic analysis revealed a discrete localization of binding sites in guinea-pig brain, with the highest density of sites in the medial thalamic nuclei and related limbic and cortical regions. Moderate levels of binding were detected in sensory relay nuclei, substantia nigra, hypothalamus, central grey and dorsal raphe nuclei. This distribution corresponded to that observed using in situ hybridization with [35S]-UTP labelled riboprobes complementary to mRNA encoding the guinea-pig 5-ht7 receptor. 4. In conclusion, under appropriate conditions, [3H]-5-CT labelled a single population of saturable binding sites that corresponded to an endogenous 5-ht7 receptor in guinea-pig brain. The distribution of 5-ht7 receptors in thalamocortical and limbic brain regions suggests a role for these receptors in sensory and affective behaviours. Images Figure 5 Figure 6 PMID:7647964

  6. Inhibition of trigeminal neurones after intravenous administration of naratriptan through an action at 5-hydroxy-tryptamine (5-HT1B/1D) receptors

    PubMed Central

    Goadsby, Peter J; Knight, Yolande

    1997-01-01

    nerve and there are no inhibitory effects mediated within the trigeminal ganglion. Furthermore, given that this inhibition could be reversed by the relatively selective 5-HT1B/1D receptor antagonist GR127935, it is highly likely that the anti-migraine effects of drugs of this class with central nervous system access are mediated, at least in part, by 5-HT1B/1D receptors within the trigeminal nucleus. PMID:9384509

  7. Hispidulin inhibits the release of glutamate in rat cerebrocortical nerve terminals

    SciTech Connect

    Lin, Tzu-Yu; Lu, Cheng-Wei; Wang, Chia-Chuan; Lu, Jyh-Feng; Wang, Su-Jane

    2012-09-01

    Hispidulin, a naturally occurring flavone, has been reported to have an antiepileptic profile. An excessive release of glutamate is considered to be related to neuropathology of epilepsy. We investigated whether hispidulin affected endogenous glutamate release in rat cerebral cortex nerve terminals (synaptosomes) and explored the possible mechanism. Hispidulin inhibited the release of glutamate evoked by the K{sup +} channel blocker 4-aminopyridine (4-AP). The effects of hispidulin on the evoked glutamate release were prevented by the chelation of extracellular Ca{sup 2+} ions and the vesicular transporter inhibitor bafilomycin A1. However, the glutamate transporter inhibitor DL-threo-beta-benzyl-oxyaspartate did not have any effect on hispidulin action. Hispidulin reduced the depolarization-induced increase in cytosolic free Ca{sup 2+} concentration ([Ca{sup 2+}]{sub C}), but did not alter 4-AP-mediated depolarization. Furthermore, the effect of hispidulin on evoked glutamate release was abolished by blocking the Ca{sub v}2.2 (N-type) and Ca{sub v}2.1 (P/Q-type) channels, but not by blocking ryanodine receptors or mitochondrial Na{sup +}/Ca{sup 2+} exchange. Mitogen-activated protein kinase kinase (MEK) inhibition also prevented the inhibitory effect of hispidulin on evoked glutamate release. Western blot analyses showed that hispidulin decreased the 4-AP-induced phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) and synaptic vesicle-associated protein synapsin I, a major presynaptic substrate for ERK; this decrease was also blocked by the MEK inhibitor. Moreover, the inhibition of glutamate release by hispidulin was strongly attenuated in mice without synapsin I. These results show that hispidulin inhibits glutamate release from cortical synaptosomes in rats through the suppression of presynaptic voltage-dependent Ca{sup 2+} entry and ERK/synapsin I signaling pathway. -- Highlights: ► Hispidulin inhibited glutamate release from rat

  8. Isoflurane depresses hippocampal CA1 glutamate nerve terminals without inhibiting fiber volleys

    PubMed Central

    Winegar, Bruce D; MacIver, M Bruce

    2006-01-01

    Background Anesthetic-induced CNS depression is thought to involve reduction of glutamate release from nerve terminals. Recent studies suggest that isoflurane reduces glutamate release by block of Na channels. To further investigate this question we examined the actions of isoflurane, TTX, extracellular Ca2+, CNQX and stimulus voltage (stim) on glutamate-mediated transmission at hippocampal excitatory synapses. EPSPs were recorded from CA1 neurons in rat hippocampal brain slices in response to Schaffer-collateral fiber stimulation. Results Isoflurane (350 μM; 1 MAC) reversibly depressed EPSP amplitudes by ~60% while facilitation increased ~20%. Consistent with previous studies, these results indicate a presynaptic site of action that involves reduced excitation-release coupling. EPSPs were depressed to comparable levels by TTX (60 nM) or lowered stim, but facilitation was not changed, indicating a simple failure of axonal conduction. Similarly, partial antagonism of postsynaptic glutamate receptors with CNQX (10 μM) depressed EPSP amplitudes with no change in facilitation. However, EPSP depression by low external Ca2+ (0.8 mM) was accompa