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Wei L, Chen L. Effects of 5-HT in globus pallidus on haloperidol-induced catalepsy in rats. Neurosci Lett 2009; 454:49-52. [PMID: 19429052 DOI: 10.1016/j.neulet.2009.02.053] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Revised: 02/25/2009] [Accepted: 02/25/2009] [Indexed: 11/18/2022]
Abstract
Histological, behavioral and electrophysiological studies have suggested that 5-HT may regulate motor function by affecting globus pallidus neurons activity. In this study, the effects of 5-HT in globus pallidus on haloperidol-induced catalepsy and its possible receptor mechanisms were examined in rats using bar tests. Bilateral microinjection of 5-HT (10microM) into globus pallidus significantly attenuated haloperidol-induced catalepsy. This anticataleptic effect was completely counteracted by selective 5-HT(1B) receptors antagonist SB-224289 (10microM), while partly reversed by selective 5-HT(4) receptors antagonist GR-113808 (1microM). In addition, the selective 5-HT(7) receptors antagonist SB-269970 (1microM) partly reversed the anticataleptic effect of 5-HT only at the incipient period after the intrapallidal injection. In conclusion, 5-HT in globus pallidus could attenuate haloperidol-induced catalepsy via multiple receptor mechanisms.
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Affiliation(s)
- Lei Wei
- Department of Physiology, Qingdao University, Qingdao 266071, China
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202
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Shpakov AO. Structural functional characteristic of neuronal serotonin receptors and molecular mechanisms of their coupling with G-proteins. NEUROCHEM J+ 2009. [DOI: 10.1134/s1819712409010012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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203
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Functional correlates for 5-HT(1A) receptors in maternally deprived rats displaying anxiety and depression-like behaviors. Prog Neuropsychopharmacol Biol Psychiatry 2009; 33:262-8. [PMID: 19111592 DOI: 10.1016/j.pnpbp.2008.11.017] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 11/25/2008] [Accepted: 11/27/2008] [Indexed: 12/16/2022]
Abstract
Maternal separation is known to induce long-term changes in neuroendocrine and emotional responsiveness to stress in a large variety of models. We examined an animal model of early deprivation in Sprague-Dawley rats consisting of separating litters from their mothers and littermates 3 h daily during postnatal days 2 to 15. In adulthood, maternally deprived rats in comparison with non-deprived controls exhibited an increase in anxiety and depression-related behaviors in the open-field and forced swim tests. Because serotonin (5-HT) 5-HT(1A) receptors seem to play an important role in the pathophysiology of major depression and in the mechanism of action of antidepressants, we investigated if 5-HT(1A) receptor function is altered in deprived rats. Although the hypothermic response to the 5-HT(1A) receptor agonist 8-OH-DPAT was increased in adult deprived rats compared to non-deprived control group, no differences between groups were found in the effect of the systemic 8-OH-DPAT administration on serotoninergic cell firing in dorsal raphe nucleus and in the 5-HT release at the ventral hippocampus levels. These results suggest that 5-HT(1A) receptors are not substantially affected in adult Sprague-Dawley rats that were subjected to a maternal deprivation 3 h daily during the neonatal period.
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204
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Effects of amyloid-β peptides on the serotoninergic 5-HT1A receptors in the rat hippocampus. Neurobiol Aging 2009; 32:103-14. [PMID: 19249128 DOI: 10.1016/j.neurobiolaging.2009.01.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2008] [Revised: 12/29/2008] [Accepted: 01/15/2009] [Indexed: 01/07/2023]
Abstract
A recent [(18)F]MPPF-positron emission tomography study has highlighted an overexpression of 5-HT(1A) receptors in the hippocampus of patients with mild cognitive impairment compared to a decrease in those with Alzheimer's disease (AD) [Truchot, L., Costes, S.N., Zimmer, L., Laurent, B., Le Bars, D., Thomas-Antérion, C., Croisile, B., Mercier, B., Hermier, M., Vighetto, A., Krolak-Salmon, P., 2007. Up-regulation of hippocampal serotonin metabolism in mild cognitive impairment. Neurology 69 (10), 1012-1017]. We used in vivo and in vitro neuroimaging to evaluate the longitudinal effects of injecting amyloid-β (Aβ) peptides (1-40) into the dorsal hippocampus of rats. In vivo microPET imaging showed no significant change in [(18)F]MPPF binding in the dorsal hippocampus over time, perhaps due to spatial resolution. However, in vitro autoradiography with [(18)F]MPPF (which is antagonist) displayed a transient increase in 5-HT(1A) receptor density 7 days after Aβ injection, whereas [(18)F]F15599 (a radiolabelled 5-HT(1A) agonist) binding was unchanged suggesting that the overexpressed 5-HT(1A) receptors were in a non-functional state. Complementary histology revealed a loss of glutamatergic neurons and an intense astroglial reaction at the injection site. Although a neurogenesis process cannot be excluded, we propose that Aβ injection leads to a transient astroglial overexpression of 5-HT(1A) receptors in compensation for the local neuronal loss. Exploration of the functional consequences of these serotoninergic modifications during the neurodegenerative process may have an impact on therapeutics targeting 5-HT(1A) receptors in AD.
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205
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Tremblay ME, Riad M, Chierzi S, Murai KK, Pasquale EB, Doucet G. Developmental course of EphA4 cellular and subcellular localization in the postnatal rat hippocampus. J Comp Neurol 2009; 512:798-813. [PMID: 19086003 DOI: 10.1002/cne.21922] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
From embryonic development to adulthood, the EphA4 receptor and several of its ephrin-A or -B ligands are expressed in the hippocampus, where they presumably play distinct roles at different developmental stages. To help clarify these diverse roles in the assembly and function of the hippocampus, we examined the cellular and subcellular localization of EphA4 in postnatal rat hippocampus by light and electron microscopic immunocytochemistry. On postnatal day (P) 1, the EphA4 immunostaining was robust in most layers of CA1, CA3, and dentate gyrus and then decreased gradually, until P21, especially in the cell body layers. At the ultrastructural level, focal spots of EphA4 immunoreactivity were detected all over the plasma membrane of pyramidal and granule cells, between P1 and P14, from the perikarya to the dendritic and axonal extremities, including growth cones and filopodia. This cell surface immunoreactivity then became restricted to the synapse-associated dendritic spines and axon terminals by P21. In astrocytes, the EphA4 immunolabeling showed a similar cell surface redistribution, from the perikarya and large processes at P1-P7, to small perisynaptic processes at P14-P21. In both cell types, spots of EphA4 immunoreactivity were also detected, with an incidence decreasing with maturation, on the endoplasmic reticulum, Golgi apparatus, and vesicles, organelles involved in protein synthesis, posttranslational modifications, and transport. The cell surface evolution of EphA4 localization in neuronal and glial cells is consistent with successive involvements in the developmental movements of cell bodies first, followed by process outgrowth and guidance, synaptogenesis, and finally synaptic maintenance and plasticity.
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Affiliation(s)
- Marie-Eve Tremblay
- Département de Pathologie et Biologie Cellulaire, Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
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206
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Uphouse L, Hiegel C, Guptarak J, Maswood N. Progesterone reduces the effect of the serotonin 1B/1D receptor antagonist, GR 127935, on lordosis behavior. Horm Behav 2009; 55:169-74. [PMID: 18952090 PMCID: PMC2665997 DOI: 10.1016/j.yhbeh.2008.09.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Revised: 09/25/2008] [Accepted: 09/26/2008] [Indexed: 11/24/2022]
Abstract
Ovariectomized rats were hormonally primed with 10 microg estradiol benzoate or with estradiol benzoate plus 500 microg progesterone. Rats received a bilateral infusion with 200 ng of the 5-HT(1B/1D) receptor antagonist, N-[4-methoxy-3-(4-methyl-1-piperazinyl)phenyl]-2'-methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)-1-1'-biphenyl-4-carboxamide hydrochloride (GR 127935), into the ventromedial nucleus of the hypothalamus (VMN), followed by a 5 min restraint or home cage experience. In estrogen-primed females that had experienced minimal handling between ovariectomy and use in the experiment, infusion with the water vehicle transiently inhibited lordosis behavior, and the 5-HT(1B/1D) receptor antagonist amplified this inhibition. There were no effects in rats hormonally primed with estrogen and progesterone. Handling for two days before the experiment reduced the effects of the infusions in estrogen-primed rats. However, when a 5 min restraint experience followed infusion with GR 127935, there was a significant decline in lordosis behavior that persisted for 10 to 15 min after the experience. Regardless of the prior experience or type of infusion, the addition of progesterone to the hormonal priming completely prevented the lordosis inhibition. These findings are consistent with prior evidence that progesterone protects against the inhibitory effects of a 5 min restraint experience on lordosis behavior. Moreover, these are the first experiments to demonstrate an inhibitory effect of a selective 5-HT(1B/1D) receptor antagonist in the VMN on lordosis behavior of estrogen primed, but not estrogen and progesterone primed, ovariectomized rats.
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Affiliation(s)
- Lynda Uphouse
- Department of Biology, Texas Woman's University, Denton, TX 76204, USA.
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207
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Parent M, Descarries L. Acetylcholine innervation of the adult rat thalamus: Distribution and ultrastructural features in dorsolateral geniculate, parafascicular, and reticular thalamic nuclei. J Comp Neurol 2008; 511:678-91. [DOI: 10.1002/cne.21868] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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208
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Social instigation and aggressive behavior in mice: role of 5-HT1A and 5-HT1B receptors in the prefrontal cortex. Psychopharmacology (Berl) 2008; 201:237-48. [PMID: 18688602 PMCID: PMC4371733 DOI: 10.1007/s00213-008-1269-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2008] [Accepted: 07/18/2008] [Indexed: 12/23/2022]
Abstract
RATIONALE Social instigation is used in rodents to induce high levels of aggression, a pattern of behavior with certain parallels to that of violent individuals. This procedure consists of a brief exposure to a provocative stimulus male, before direct confrontation with an intruder. Studies using 5-HT1A and 5-HT1B receptor agonists show an effective reduction in aggressive behavior. An important site of action for these drugs is the ventral orbitofrontal cortex (VO PFC), an area of the brain which is particularly relevant in the inhibitory control of aggressive and impulsive behavior. OBJECTIVES The objectives of the study are to assess the anti-aggressive effects of 5-HT1A and 5-HT1B agonist receptors [8-hydroxy-2-(di-n-propylamino) tetralin hydrobromide (8-OH-DPAT) and CP-93,129] in the VO PFC of socially provoked male mice. To confirm the specificity of the receptor, 5-HT1A and 5-HT1B antagonist receptors (WAY-100,635 and SB-224,289) were microinjected into the same area, in order to reverse the agonist effects. RESULTS 8-OH-DPAT (0.56 and 1.0 microg) reduced the frequency of attack bites. The lowest dose of CP-93,129 (0.1 microg) also decreased the number of attack bites and lateral threats. 5-HT1A and 5-HT1B receptor agonists differed in their effects on non-aggressive activities, the former decreasing rearing and grooming, and the latter, increasing these acts. Specific participation of the 1A and 1B receptors was verified by reversal of anti-aggressive effects using selective antagonists WAY-100,635 (10.0 microg) and SB-224,289 (1.0 microg). CONCLUSIONS The decrease in aggressiveness observed with microinjections of 5-HT1A and 5-HT1B receptor agonists into the VO PFC of socially provoked mice, supports the hypothesis that activation of these receptors modulates high levels of aggression in a behaviorally specific manner.
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209
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Nguyen KQ, Tohyama Y, Watanabe A, Hasegawa S, Skelin I, Diksic M. Acute effects of combining citalopram and pindolol on regional brain serotonin synthesis in sham operated and olfactory bulbectomized rats. Neurochem Int 2008; 54:161-71. [PMID: 19073228 DOI: 10.1016/j.neuint.2008.08.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2008] [Revised: 08/25/2008] [Accepted: 08/26/2008] [Indexed: 10/21/2022]
Abstract
The olfactory bulbectomized (OBX) rat is considered to be a good model of the pathology of human depression and also of the functional actions of antidepressant drug therapy. It has been proposed that antidepressant effects of selective serotonin reuptake inhibitors (SSRIs) can be accelerated by blocking 5-HT(1A/B) autoreceptors with pindolol. The underlying mechanism is thought to involve acute unrestricting of 5-HT release and, consequently, relatively enhanced 5-HT turnover throughout the forebrain serotonergic networks. The effect of this combination on 5-HT turnover in sham operated or OBX rats can be assessed at the level of 5-HT synthesis, a very important presynaptic step in serotonergic neurotransmission, using the alpha-[(14)C]methyl-l-tryptophan autoradiography method. In sham rats, acute citalopram (20mg/kg) treatment increased synthesis at almost all serotonergic terminal regions but slightly decreased synthesis at serotonergic cell body regions (i.e. dorsal and median (not significant) raphe; approximately 16%). Combining pindolol (10mg/kg) with citalopram further increased synthesis at many regions in sham rats (relative to treatment with only citalopram). In OBX rats, citalopram decreased synthesis at a few terminal regions and greatly decreased synthesis at the dorsal and median raphe ( approximately 45%; relative to OBX rats treated with saline). Combining pindolol with citalopram greatly increased synthesis at almost all regions in OBX rats (relative to treatment with only citalopram). These results suggest that acute citalopram effects result in elevated terminal 5-HT synthesis, but these effects are restrained by 5-HT(1A/B) autoreceptor feedback to different degrees in sham and OBX rats. Moreover, 5-HT(1A/B) autoreceptor feedback is stronger in OBX rats and may underlie the delay of SSRI effects in OBX rats and, correspondingly, in human depression. Pindolol acceleration and augmentation of SSRI antidepressant therapy for human depression may be mediated by attenuation of 5-HT(1A/B) autoreceptor feedback, permitting unhindered SSRI effects on serotonergic terminals.
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Affiliation(s)
- Khanh Q Nguyen
- Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada
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210
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Jeong HJ, Chenu D, Johnson EE, Connor M, Vaughan CW. Sumatriptan inhibits synaptic transmission in the rat midbrain periaqueductal grey. Mol Pain 2008; 4:54. [PMID: 19014464 PMCID: PMC2588575 DOI: 10.1186/1744-8069-4-54] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Accepted: 11/11/2008] [Indexed: 01/22/2023] Open
Abstract
Background There is evidence to suggest that the midbrain periaqueductal grey (PAG) has a role in migraine and the actions of the anti-migraine drug sumatriptan. In the present study we examined the serotonergic modulation of GABAergic and glutamatergic synaptic transmission in rat midbrain PAG slices in vitro. Results Serotonin (5-hydroxytriptamine, 5-HT, IC50 = 142 nM) and the selective serotonin reuptake inhibitor fluoxetine (30 μM) produced a reduction in the amplitude of GABAA-mediated evoked inhibitory postsynaptic currents (IPSCs) in all PAG neurons which was associated with an increase in the paired-pulse ratio of evoked IPSCs. Real time PCR revealed that 5-HT1A, 5-HT1B, 5-HT1D and 5-HT1F receptor mRNA was present in the PAG. The 5-HT1A, 5-HT1B and 5-HT1D receptor agonists 8-OH-DPAT (3 μM), CP93129 (3 μM) and L694247 (3 μM), but not the 5-HT1F receptor agonist LY344864 (1 – 3 μM) inhibited evoked IPSCs. The 5-HT (1 μM) induced inhibition of evoked IPSCs was abolished by the 5-HT1B antagonist NAS181 (10 μM), but not by the 5-HT1A and 5-HT1D antagonists WAY100135 (3 μM) and BRL15572 (10 μM). Sumatriptan also inhibited evoked IPSCs with an IC50 of 261 nM, and reduced the rate, but not the amplitude of spontaneous miniature IPSCs. The sumatriptan (1 μM) induced inhibition of evoked IPSCs was abolished by NAS181 (10 μM) and BRL15572 (10 μM), together, but not separately. 5-HT (10 μM) and sumatriptan (3 μM) also reduced the amplitude of non-NMDA mediated evoked excitatory postsynaptic currents (EPSCs) in all PAG neurons tested. Conclusion These results indicate that sumatriptan inhibits GABAergic and glutamatergic synaptic transmission within the PAG via a 5-HT1B/D receptor mediated reduction in the probability of neurotransmitter release from nerve terminals. These actions overlap those of other analgesics, such as opioids, and provide a mechanism by which centrally acting 5-HT1B and 5-HT1D ligands might lead to novel anti-migraine pharmacotherapies.
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Affiliation(s)
- Hyo-Jin Jeong
- Pain Management Research Institute, Kolling Institute of Medical Research, Northern Clinical School, The University of Sydney at Royal North Shore Hospital, NSW 2065, Australia.
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211
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Smith VM, Sterniczuk R, Phillips CI, Antle MC. Altered photic and non-photic phase shifts in 5-HT(1A) receptor knockout mice. Neuroscience 2008; 157:513-23. [PMID: 18930788 DOI: 10.1016/j.neuroscience.2008.09.030] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Revised: 09/17/2008] [Accepted: 09/18/2008] [Indexed: 11/30/2022]
Abstract
The mammalian circadian clock located in the suprachiasmatic nucleus (SCN) is thought to be modulated by 5-HT. 5-HT is though to inhibit photic phase shifts by inhibiting the release of glutamate from retinal terminals, as well as by decreasing the responsiveness of retinorecipient cells in the SCN. Furthermore, there is also evidence that 5-HT may underlie, in part, non-photic phase shifts of the circadian system. Understanding the mechanism by which 5-HT accomplishes these goals is complicated by the wide variety of 5-HT receptors found in the SCN, the heterogeneous organization of both the circadian clock and the location of 5-HT receptors, and by a lack of sufficiently selective pharmacological agents for the 5-HT receptors of interest. Genetically modified animals engineered to lack a specific 5-HT receptor present an alternative avenue of investigation to understand how 5-HT regulates the circadian system. Here we examine behavioral and molecular responses to both photic and non-photic stimuli in mice lacking the 5-HT(1A) receptor. When compared with wild-type controls, these mice exhibit larger phase advances to a short late-night light pulse and larger delays to long 12 h light pulses that span the whole subjective night. Fos and mPer1 expression in the retinorecipient SCN is significantly attenuated following late-night light pulses in the 5-HT(1A) knockout animals. Finally, non-photic phase shifts to (+/-)-8-hydroxy-2-(dipropylamino)tetralin hydrobromide (8-OH-DPAT) are lost in the knockout animals, while attenuation of the phase shift to the long light pulse due to rebound activity following a wheel lock is unaffected. These findings suggest that the 5-HT(1A) receptor plays an inhibitory role in behavioral phase shifts, a facilitatory role in light-induced gene expression, a necessary role in phase shifts to 8-OH-DPAT, and is not necessary for activity-induced phase advances that oppose photic phase shifts to long light pulses.
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Affiliation(s)
- V M Smith
- Department of Psychology, University of Calgary, 2500 University Drive Northwest, Calgary, Alberta, Canada T2N 1N4
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212
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de Almeida J, Mengod G. Serotonin 1A receptors in human and monkey prefrontal cortex are mainly expressed in pyramidal neurons and in a GABAergic interneuron subpopulation: implications for schizophrenia and its treatment. J Neurochem 2008; 107:488-96. [PMID: 18761712 DOI: 10.1111/j.1471-4159.2008.05649.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Serotonin 1A (5-HT(1A)) receptors are found in high densities in prefrontal cortex. However, their distribution within cortical cell populations is unknown in both humans and primates. We used double in situ hybridization histochemistry to quantify the percentage of glutamatergic and GABAergic neurons expressing 5-HT(1A) receptors in human and monkey prefrontal cortex. Moreover, in the case of the monkey, we also quantified the parvalbumin and calbindin GABAergic subpopulations expressing this receptor. 5-HT(1A) receptor mRNAs were expressed in about 80% of glutamatergic neurons in external layers II and upper III, and in around 50% in layer VI; they were also present in approximately 20% of GABAergic neurons in both species. Although they were found in up to 43% of the calbindin cell subpopulation they were rarely present in parvalbumin cells in monkey prefrontal cortex. The knowledge of the phenotype of the prefrontal cortex (PFC) cells expressing 5-HT(1A) will help understanding serotonin actions in PFC.
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Affiliation(s)
- Julián de Almeida
- Departament de Neuroquimica i Neurofarmacologia, Institut d'Investigacions Biomèdiques de Barcelona (CSIC), IDIBAPS, Barcelona, Spain
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213
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Peddie C, Davies H, Colyer F, Stewart M, Rodríguez J. Dendritic colocalisation of serotonin1B receptors and the glutamate NMDA receptor subunit NR1 within the hippocampal dentate gyrus: An ultrastructural study. J Chem Neuroanat 2008; 36:17-26. [DOI: 10.1016/j.jchemneu.2008.05.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Revised: 04/08/2008] [Accepted: 05/06/2008] [Indexed: 10/22/2022]
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214
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Fuxe K, Marcellino D, Rivera A, Diaz-Cabiale Z, Filip M, Gago B, Roberts D, Langel U, Genedani S, Ferraro L, de la Calle A, Narvaez J, Tanganelli S, Woods A, Agnati L. Receptor–receptor interactions within receptor mosaics. Impact on neuropsychopharmacology. ACTA ACUST UNITED AC 2008; 58:415-52. [DOI: 10.1016/j.brainresrev.2007.11.007] [Citation(s) in RCA: 167] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Revised: 11/26/2007] [Accepted: 11/29/2007] [Indexed: 01/01/2023]
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215
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Dal Bo G, Bérubé-Carrière N, Mendez JA, Leo D, Riad M, Descarries L, Lévesque D, Trudeau LE. Enhanced glutamatergic phenotype of mesencephalic dopamine neurons after neonatal 6-hydroxydopamine lesion. Neuroscience 2008; 156:59-70. [PMID: 18706980 DOI: 10.1016/j.neuroscience.2008.07.032] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 07/14/2008] [Accepted: 07/15/2008] [Indexed: 10/21/2022]
Abstract
There is increasing evidence that a subset of midbrain dopamine (DA) neurons uses glutamate as a co-transmitter and expresses vesicular glutamate transporter (VGLUT) 2, one of the three vesicular glutamate transporters. In the present study, double in situ hybridization was used to examine tyrosine hydroxylase (TH) and VGLUT2 mRNA expression during the embryonic development of these neurons, and postnatally, in normal rats and rats injected with 6-hydroxydopamine (6-OHDA) at P4 to destroy partially DA neurons. At embryonic days 15 and 16, there was a regional overlap in the labeling of TH and VGLUT2 mRNA in the ventral mesencephalon, which was no longer found at late embryonic stages (E18-E21) and postnatally. In normal pups from P5 to P15, only 1-2% of neurons containing TH mRNA in the ventral tegmental area (VTA) and substantia nigra, pars compacta, also displayed VGLUT2 mRNA. In contrast, after the cerebroventricular administration of 6-OHDA at P4, 26% of surviving DA neurons in the VTA of P15 rats expressed VGLUT2. To search for a colocalization of TH and VGLUT2 protein in axon terminals of these neurons, the nucleus accumbens of normal and 6-OHDA-lesioned P15 rats was examined by electron microscopy after dual immunocytochemical labeling. In normal rats, VGLUT2 protein was found in 28% of TH positive axon terminals in the core of nucleus accumbens. In 6-OHDA-lesioned rats, the total number of TH positive terminals was considerably reduced, and yet the proportion also displaying VGLUT2 immunoreactivity was modestly but significantly increased (37%). These results lead to the suggestion that the glutamatergic phenotype of a VTA DA neurons is highly plastic, repressed toward the end of normal embryonic development, and derepressed postnatally following injury. They also support the hypothesis of co-release of glutamate and DA by mesencephalic neurons in vivo, at least in the developing brain.
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Affiliation(s)
- G Dal Bo
- Department of Pharmacology, Faculty of Medicine, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, QC, Canada H3C 3J7
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Regionally selective changes in neurotransmitter receptors in the brain of the 5-HT1B knockout mouse. J Chem Neuroanat 2008; 35:356-63. [DOI: 10.1016/j.jchemneu.2008.02.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 02/19/2008] [Accepted: 02/20/2008] [Indexed: 11/18/2022]
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217
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Dupre KB, Eskow KL, Steiniger A, Klioueva A, Negron GE, Lormand L, Park JY, Bishop C. Effects of coincident 5-HT1A receptor stimulation and NMDA receptor antagonism on L-DOPA-induced dyskinesia and rotational behaviors in the hemi-parkinsonian rat. Psychopharmacology (Berl) 2008; 199:99-108. [PMID: 18545986 DOI: 10.1007/s00213-008-1135-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Accepted: 03/01/2008] [Indexed: 11/27/2022]
Abstract
RATIONALE Serotonin 1A receptor (5-HT1AR) agonists reduce L-DOPA-induced dyskinesia and enhance motor function in experimental and clinical investigations of Parkinson's disease (PD). While the mechanism(s) by which these effects occur are unclear, recent research suggests that modulation of glutamate neurotransmission contributes. OBJECTIVE To further delineate the relationship between 5-HT1A receptors and glutamate, the current study examined the effects of the 5-HT1AR agonist, +/-8-OH-DPAT and the N-methyl-D-aspartic acid receptor (NMDAR) antagonist, MK-801, on L-DOPA-induced motor behavior. MATERIALS AND METHODS Unilateral 6-hydroxydopamine lesioned male Sprague-Dawley rats were rendered dyskinetic with 1 week of daily L-DOPA (12 mg/kg, i.p.) + benserazide (15 mg/kg, i.p.). On test days, one group of rats received pretreatments of: +/-8-OH-DPAT (0, 0.03, 0.1, 0.3 mg/kg, i.p.) or MK-801 (0, 0.03, 0.1, 0.3 mg/kg, i.p.). A second group was administered combined +/-8-OH-DPAT (0, 0.03 or 0.1 mg/kg, i.p.) + MK-801 (0, 0.1 mg/kg, i.p.). Pretreatments were followed by L-DOPA administration, after which, abnormal involuntary movements (AIMs) and rotations were monitored. To investigate effects on motor performance, subthreshold doses of +/-8-OH-DPAT (0.03 mg/kg, i.p.) + MK-801 (0.1 mg/kg, i.p.) were administered to L-DOPA-naïve hemiparkinsonian rats before the forepaw adjusting steps test. RESULTS Individually, both +/-8-OH-DPAT and MK-801 dose-dependently decreased L-DOPA-induced AIMs without affecting rotations. Combined subthreshold doses of +/-8-OH-DPAT+MK-801 reduced L-DOPA-induced AIMs and potently enhanced contralateral rotations without altering L-DOPA-induced motor improvements. CONCLUSIONS The current results indicate a functional interaction between 5-HT1AR and NMDAR that may improve pharmacological treatment of PD patients.
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Affiliation(s)
- Kristin B Dupre
- Department of Psychology, Behavioral Neuroscience Program, State University of New York at Binghamton, Binghamton, NY 13902-6000, USA
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Le François B, Czesak M, Steubl D, Albert PR. Transcriptional regulation at a HTR1A polymorphism associated with mental illness. Neuropharmacology 2008; 55:977-85. [PMID: 18639564 DOI: 10.1016/j.neuropharm.2008.06.046] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 06/23/2008] [Accepted: 06/24/2008] [Indexed: 12/18/2022]
Abstract
The serotonin-1A (5-HT1A) receptor serves as a hub to regulate the activity and actions of the serotonin system, and is expressed both as a presynaptic autoreceptor on raphe neurons, and as a major postsynaptic receptor in hippocampal, cortical, and hypothalamic regions involved in mood, emotion and stress response. As such, the level of expression of 5-HT1A receptors is implicated in the development of anxiety and depression phenotypes. This review focuses on the C(-1019)G (rs6295) promoter polymorphism of the 5-HT1A receptor gene (HTR1A) and its effect on the activity of transcription factors that recognize the C-allele, including Deaf-1, Hes1 and Hes5; its effects on 5-HT1A receptor expression in pre- and postsynaptic areas; as well as its implication in early postnatal development and adult neurogenesis in the hippocampus and cortex. Although several studies have now replicated the association of the G-allele with depression, panic disorder, neuroticism, and reduced response to antidepressant or antipsychotic treatment, ethnic, disease and genetic heterogeneity among subjects in different studies may obscure such associations. Gene-gene interaction studies suggest that the 5-HT1A receptor G(-1019) allele is a risk allele which could be used as a marker for depression and related mood disorders. Finally, association of the G(-1019) allele with increased raphe 5-HT1A binding potential, increased amygdala reactivity to emotional stimuli, and reduced amygdala volume, particularly in disease states, suggests a functional role for the C(-1019)G site in 5-HT1A receptor dys-regulation and predisposition to mental illness.
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Affiliation(s)
- Brice Le François
- Ottawa Health Research Institute (Neuroscience), University of Ottawa, 451 Smyth Road, Ottawa, ON, Canada K1H 8M5
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Carta M, Carlsson T, Muñoz A, Kirik D, Björklund A. Involvement of the serotonin system in L-dopa-induced dyskinesias. Parkinsonism Relat Disord 2008; 14 Suppl 2:S154-8. [PMID: 18579429 DOI: 10.1016/j.parkreldis.2008.04.021] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ability of L-dopa to relieve the motor impairments in Parkinson's disease patients declines over time, and side-effects, such as dyskinesias, appear--limiting the use of the drug in the advanced stage of the disease. Serotonergic neurons are able to convert L-dopa to dopamine and to store this neurotransmitter in synaptic vesicles. This peculiarity might be very important in the advanced disease, when most of the dopaminergic neurons have degenerated. Indeed, an increasing body of evidence points to dopamine released as a false neurotransmitter from the serotonin terminals as the main pre-synaptic determinant of L-dopa-induced dyskinesias in animal models of Parkinson's disease. These findings make the serotonin system an intriguing target for anti-dyskinetic therapies.
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Affiliation(s)
- Manolo Carta
- Neurobiology Unit, Wallenberg Neuroscience Center, Department of Experimental Medical Science, Lund University, Lund, Sweden.
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220
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Affiliation(s)
- David E Nichols
- Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmaceutical Sciences, Purdue University, West Lafayette, Indiana 47906-2091, USA.
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221
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Hashimoto K, Kita H. Serotonin Activates Presynaptic and Postsynaptic Receptors in Rat Globus Pallidus. J Neurophysiol 2008; 99:1723-32. [DOI: 10.1152/jn.01143.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although recent histological, behavioral, and clinical studies suggest that serotonin (5-HT) plays significant roles in the control of pallidal activity, only little is known about the physiological action of 5-HT in the pallidum. Our recent unit recording study in monkeys suggested that 5-HT provides both presynaptic and postsynaptic modulations of pallidal neurons. The present study using rat brain slice preparations further explored these presynaptic and postsynaptic actions of 5-HT. Bath application of 5-HT or the 5-HT1A/1B/1D/5/7 receptor (R) agonist 5-carboxamidotryptamine maleate (5-CT) depolarized some and hyperpolarized other pallidal neurons. Pretreatments of slices with blockers of the hyperpolarization–cyclic nucleotide-activated current or with the 5-HT2/7R–selective antagonist mesulergine occluded 5-CT–induced depolarization. The 5-HT1AR–selective blocker N-[2[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]- N-2-pyridinylcyclohex- anecarboxamide maleate occluded the 5-CT–induced hyperpolarization. These results suggested involvement of 5-HT7R and 5-HT1AR in the postsynaptic depolarization and hyperpolarization, respectively. 5-CT presynaptically suppressed both internal capsule stimulation–induced excitatory postsynaptic currents (EPSCs) and striatal stimulation–induced inhibitory postsynaptic currents (IPSCs). The potencies of 5-CT on the presynaptic effects were 20- to 25-fold higher than on postsynaptic effects, suggesting that 5-HT mainly modulates presynaptic sites in the globus pallidus. Experiments with several antagonists suggested involvement of 5-HT1B/DR in the presynaptic suppression of EPSCs. However, the receptor type involved in the presynaptic suppression of IPSCs was inconclusive. The present results provided evidence that 5-HT exerts significant control over the synaptic inputs and the autonomous activity of pallidal neurons.
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222
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Perrier JF, Cotel F. Serotonin differentially modulates the intrinsic properties of spinal motoneurons from the adult turtle. J Physiol 2007; 586:1233-8. [PMID: 18096602 DOI: 10.1113/jphysiol.2007.145706] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
This report considers serotonergic (5-HT) effects on spinal motoneurons, reviewing previous data and presenting a new study showing distinct effects of two 5-HT receptor subtypes. We previously investigated the effects of 5-HT on motoneurons in a slice preparation from the spinal cord of the adult turtle. In agreement with previous studies, we had found that 5-HT applied to the extracellular medium promoted a voltage sensitive plateau potential. However, we also reported that this effect was only observed in half of the motoneurons; 5-HT inhibited the firing of the other half of the motoneurons recorded from. To investigate the reasons for this, we applied 5-HT focally by means of the microiontophoresis technique. Facilitation of plateau potentials was observed when 5-HT was released at sites throughout the somatodendritic region. However, motoneurons were inhibited by 5-HT when selectively applied in the perisomatic region. These two effects could be induced in the same motoneuron. With pharmacological tools, we demonstrate here that the facilitation of plateau potentials is mediated by 5-HT(2) receptors and the inhibitory effect is due to the activation of 5-HT(1A/7) receptors.
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Affiliation(s)
- Jean-François Perrier
- Institute of Neuroscience and Pharmacology, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen, Denmark.
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223
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Chen L, Yung KKL, Chan YS, Yung WH. 5-HT excites globus pallidus neurons by multiple receptor mechanisms. Neuroscience 2007; 151:439-51. [PMID: 18082329 DOI: 10.1016/j.neuroscience.2007.11.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Revised: 10/31/2007] [Accepted: 11/30/2007] [Indexed: 11/26/2022]
Abstract
Anatomical and neurochemical studies indicated that the globus pallidus receives serotonergic innervation from raphe nuclei but the membrane effects of 5-HT on globus pallidus neurons are not entirely clear. We address this question by applying whole-cell patch-clamp recordings on globus pallidus neurons in immature rat brain slices. Under current-clamp recording, 5-HT depolarized globus pallidus neurons and increased their firing rate, an action blocked by both 5-HT(4) and 5-HT(7) receptor antagonists and attributable to an increase in cation conductance(s). Further experiments indicated that 5-HT enhanced the hyperpolarization-activated inward conductance which is blocked by 5-HT(7) receptor antagonist. To determine if 5-HT exerts any presynaptic effects on GABAergic and glutamatergic inputs, the actions of 5-HT on synaptic currents were studied. At 10 microM, 5-HT increased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) but had no effect on both the frequency and amplitude of miniature inhibitory postsynaptic currents (mIPSCs). However, 5-HT at a higher concentration (50 microM) decreased the frequency but not the amplitude of the mIPSCs, indicating an inhibition of GABA release from the presynaptic terminals. This effect was sensitive to 5-HT(1B) receptor antagonist. In addition to the presynaptic effects on GABAergic neurotransmission, 5-HT at 50 microM had no consistent effects on glutamatergic neurotransmission, significantly increased the frequency of miniature excitatory postsynaptic currents (mEPSCs) in 4 of 11 neurons and decreased the frequency of mEPSCs in 3 of 11 neurons. In conclusion, we found that 5-HT could modulate the excitability of globus pallidus neurons by both pre- and post-synaptic mechanisms. In view of the extensive innervation by globus pallidus neurons on other basal ganglia nuclei, this action of 5-HT originated from the raphe may have a profound effect on the operation of the entire basal ganglia network.
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Affiliation(s)
- L Chen
- Department of Physiology, The Chinese University of Hong Kong, Shatin, Hong Kong, China
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224
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Abstract
The lateral giant (LG) command neuron of crayfish responds to an attack directed at the abdomen by triggering a single highly stereotyped escape tail flip. Experimentally applied serotonin (5-hydroxytrptamine, 5-HT) can increase or decrease LG's excitability, depending on the concentration, rate, and duration of 5-HT application. Here we describe three physiological mechanisms that mediate serotonergic facilitation of LG. Two processes strengthen electrical coupling between the primary mechanosensory afferent neurons and LG: first, an early increase in the conductance of electrical synapses between primary afferent neurons and LG dendrites and second, an early increase in the membrane resistance of LG dendrites. The increased coupling facilitates LG's synaptic response and it promotes recruitment of weakly excited afferent neurons to contribute to the response. Third, a delayed increase in the membrane resistance of proximal regions of LG increases the cell's input resistance near the initial segment. Together these mechanisms contribute to serotonergic facilitation of LG's response.
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225
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Hensler JG, Advani T, Monteggia LM. Regulation of serotonin-1A receptor function in inducible brain-derived neurotrophic factor knockout mice after administration of corticosterone. Biol Psychiatry 2007; 62:521-9. [PMID: 17336942 DOI: 10.1016/j.biopsych.2006.10.015] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2006] [Revised: 09/19/2006] [Accepted: 10/12/2006] [Indexed: 11/24/2022]
Abstract
BACKGROUND We examined the effects of a forebrain-specific reduction in brain-derived neurotrophic factor (BDNF) on the regulation of serotonin-1A (5-HT1A) receptor function in serotonergic cell body areas as well as in limbic and cortical structures of mice chronically treated with corticosterone. METHODS 5-HT1A receptor function, at the level of receptor-G protein interaction, was assessed with quantitative autoradiography of [35S]GTPgammaS binding stimulated by the 5-HT1A receptor agonist 8-OH-DPAT. 5-HT1A receptor number was assessed by measuring the binding of the antagonist radioligand [3H] WAY100635. RESULTS We observed a significant attenuation of 5-HT1A receptor function, in the absence of a change in receptor number, in the dorsal hippocampus of BDNF knockout versus control mice. There was no difference between control and BDNF knockout mice in 5-HT1A receptor number or function in the dorsal or median raphe nuclei or medial prefrontal cortex or anterior cingulate cortex. Corticosterone treatment of control mice decreased 5-HT1A receptor function in the dorsal and median raphe but not in hippocampus or frontal cortical areas. The regulation of 5HT1A receptor number or function in the dorsal and median raphe by corticosterone was lost in BDNF knockout mice. CONCLUSIONS Attenuation of BDNF expression in forebrain regions produces differential effects on distinct 5-HT1A receptor populations and on the regulation of these receptor populations by corticosterone.
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Affiliation(s)
- Julie G Hensler
- Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA.
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226
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Ho SSN, Chow BKC, Yung WH. Serotonin increases the excitability of the hypothalamic paraventricular nucleus magnocellular neurons. Eur J Neurosci 2007; 25:2991-3000. [PMID: 17561813 DOI: 10.1111/j.1460-9568.2007.05547.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent evidence that 5-hydroxytryptamine (5-HT or serotonin) enhances the release and the gene expression of vasopressin and oxytocin in the hypothalamic paraventricular nucleus (PVN) suggests that 5-HT can excite the PVN magnocellular neurons. The objective of this study was to examine the underlying mechanisms for such excitatory action in the electrophysiologically identified hypothalamic PVN magnocellular neurons in rats using whole-cell patch-clamp. We found that 5-HT weakly depolarizes 33.3% of PVN magnocellular neurons in the presence of tetrodotoxin. A minuscule inward current was produced by 5-HT in 48% of the cells, which was attenuated when the 5-HT(4) antagonist GR113808 or the 5-HT(7) antagonist SB269970 was added. In addition, 5-HT reduced the frequency of miniature inhibitory postsynaptic currents in a dose-dependent manner. This inhibition was mimicked by the 5-HT(1B) agonist CP93129, and reversed in the presence of 5-HT(1B) antagonists cyanopindolol and SB224289. Besides, 5-HT induced a biphasic effect on the frequency of miniature excitatory postsynaptic currents, comprising a transient inhibition and a delayed concentration-dependent excitation (onset latency approximately 5 min). The facilitation was mimicked by the 5-HT(2A/2C) agonist DOI and abolished in the presence of the 5-HT(2C) antagonist RS102221. Our findings reveal that 5-HT directly increases the excitability of the PVN magnocellular neurons via multiple receptor subtypes and mechanisms. This may help understanding the regulation of 5-HT-induced hormone release and feeding behavior in the PVN.
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Affiliation(s)
- Sara S N Ho
- Department of Zoology, The University of Hong Kong, Pokfulam, Hong Kong, China
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227
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Fuxe K, Dahlström A, Höistad M, Marcellino D, Jansson A, Rivera A, Diaz-Cabiale Z, Jacobsen K, Tinner-Staines B, Hagman B, Leo G, Staines W, Guidolin D, Kehr J, Genedani S, Belluardo N, Agnati LF. From the Golgi–Cajal mapping to the transmitter-based characterization of the neuronal networks leading to two modes of brain communication: Wiring and volume transmission. ACTA ACUST UNITED AC 2007; 55:17-54. [PMID: 17433836 DOI: 10.1016/j.brainresrev.2007.02.009] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 02/21/2007] [Accepted: 02/27/2007] [Indexed: 10/23/2022]
Abstract
After Golgi-Cajal mapped neural circuits, the discovery and mapping of the central monoamine neurons opened up for a new understanding of interneuronal communication by indicating that another form of communication exists. For instance, it was found that dopamine may be released as a prolactin inhibitory factor from the median eminence, indicating an alternative mode of dopamine communication in the brain. Subsequently, the analysis of the locus coeruleus noradrenaline neurons demonstrated a novel type of lower brainstem neuron that monosynaptically and globally innervated the entire CNS. Furthermore, the ascending raphe serotonin neuron systems were found to globally innervate the forebrain with few synapses, and where deficits in serotonergic function appeared to play a major role in depression. We propose that serotonin reuptake inhibitors may produce antidepressant effects through increasing serotonergic neurotrophism in serotonin nerve cells and their targets by transactivation of receptor tyrosine kinases (RTK), involving direct or indirect receptor/RTK interactions. Early chemical neuroanatomical work on the monoamine neurons, involving primitive nervous systems and analysis of peptide neurons, indicated the existence of alternative modes of communication apart from synaptic transmission. In 1986, Agnati and Fuxe introduced the theory of two main types of intercellular communication in the brain: wiring and volume transmission (WT and VT). Synchronization of phasic activity in the monoamine cell clusters through electrotonic coupling and synaptic transmission (WT) enables optimal VT of monoamines in the target regions. Experimental work suggests an integration of WT and VT signals via receptor-receptor interactions, and a new theory of receptor-connexin interactions in electrical and mixed synapses is introduced. Consequently, a new model of brain function must be built, in which communication includes both WT and VT and receptor-receptor interactions in the integration of signals. This will lead to the unified execution of information handling and trophism for optimal brain function and survival.
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Affiliation(s)
- Kjell Fuxe
- Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden.
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Mignon L, Wolf WA. Postsynaptic 5-HT1A receptor stimulation increases motor activity in the 6-hydroxydopamine-lesioned rat: implications for treating Parkinson's disease. Psychopharmacology (Berl) 2007; 192:49-59. [PMID: 17265149 DOI: 10.1007/s00213-006-0680-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2006] [Accepted: 12/11/2006] [Indexed: 10/23/2022]
Abstract
RATIONALE We have shown that the 5-HT1A agonist R-(+)-hydroxy-2-(di-n-propylamino)tetralin [R-(+)-8-OHDPAT] enhances motor activity in the monoamine-depleted rat, an acute model of Parkinson's disease. The present work extends these findings by investigating motor effects of R-(+)-8-OHDPAT in the unilateral 6-hydroxydopamine-lesioned rat, a chronic model of Parkinson's disease. OBJECTIVE The objectives of the present study were to assess the motor response to R-(+)-8-OHDPAT in rats with unilateral destruction of the nigrostriatal dopamine system and to determine the involvement of postsynaptic 5-HT1A receptors in this response. MATERIALS AND METHODS Rotational behavior after R-(+)-8-OHDPAT was investigated in rats that received 6-hydroxydopamine unilaterally into the median forebrain bundle 2 weeks before testing. RESULTS A dose of 0.3 mg/kg subcutaneously (s.c.) R-(+)-8-OHDPAT induced significant ipsilateral turning in unilateral 6-OHDA-lesioned rats. Pretreatment with the selective 5-HT(1A) antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinyl-cyclohexanecarboxiamide maleate (WAY-100635, 0.1 mg/kg, s.c.) blocked turning. Blockade of 5-HT synthesis and 5-HT depletion caused by the tryptophan hydroxylase inhibitor DL: -p-chlorophenylalanine did not decrease R-(+)-8-OHDPAT-induced turning. Finally, a subset of animals were tested for their turning response to the dopamine agonist apomorphine after tests with R-(+)-8-OHDPAT had been completed. Correlation analysis indicated no relationship existed between the turning response to apomorphine and the turning response to R-(+)-8-OHDPAT. CONCLUSION R-(+)-8-OHDPAT induces ipsilateral turning in unilateral 6-OHDA lesioned rats by stimulating postsynaptic 5-HT1A receptors, not by altering 5-HT synthesis and release. The mechanism underlying the motor effects of R-(+)-8-OHDPAT appears to differ from classic dopaminergic anti-parkinsonian agents suggesting that 5-HT1A agonists might prove useful adjunctive therapy in the treatment of Parkinson's disease.
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Affiliation(s)
- Laurence Mignon
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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Tremblay ME, Riad M, Bouvier D, Murai KK, Pasquale EB, Descarries L, Doucet G. Localization of EphA4 in axon terminals and dendritic spines of adult rat hippocampus. J Comp Neurol 2007; 501:691-702. [PMID: 17299751 DOI: 10.1002/cne.21263] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Eph receptors and their ephrin ligands assume various roles during central nervous system development. Several of these proteins are also expressed in the mature brain, and notably in the hippocampus, where EphA4 and ephrins have been shown to influence dendritic spine morphology and long-term potentiation (LTP). To examine the cellular and subcellular localization of EphA4 in adult rat ventral hippocampus, we used light and electron microscopic immunocytochemistry with a specific polyclonal antibody against EphA4. After immunoperoxidase labeling, EphA4 immunoreactivity was found to be enriched in the neuropil layers of CA1, CA3, and dentate gyrus. In all examined layers of these regions, myelinated axons, small astrocytic leaflets, unmyelinated axons, dendritic spines, and axon terminals were immunolabeled in increasing order of frequency. Neuronal cell bodies and dendritic branches were immunonegative. EphA4-labeled dendritic spines and axon terminals corresponded to 9-19% and 25-40% of the total number of spines and axon terminals, respectively. Most labeled spines were innervated by unlabeled terminals, but synaptic contacts between two labeled elements were seen. The vast majority of synaptic junctions made by labeled elements was asymmetrical and displayed features of excitatory synapses. Immunogold labeling of EphA4 was located mostly on the plasma membrane of axons, dendritic spines, and axon terminals, supporting its availability for surface interactions with ephrins. The dual preferential labeling of EphA4 on pre- or postsynaptic specializations of excitatory synapses in adult rat hippocampus is consistent with roles for this receptor in synaptic plasticity and LTP.
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Affiliation(s)
- Marie-Eve Tremblay
- Département de pathologie et biologie cellulaire and Groupe de recherche sur le système nerveux central, Université de Montréal, Montréal, Québec, Canada
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Schneider AM, Simson PE. NAN-190 potentiates the impairment of retention produced by swim stress. Pharmacol Biochem Behav 2007; 87:73-80. [PMID: 17490739 DOI: 10.1016/j.pbb.2007.04.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2006] [Revised: 03/27/2007] [Accepted: 04/03/2007] [Indexed: 10/23/2022]
Abstract
Exposing rats to stress in the form of forced swim immediately after passive-avoidance training impaired retention. In contrast, exposure to the same stressor 2 h after training failed to impair retention. Systemic administration of the 5-HT1A receptor antagonist NAN-190 (1 mg/kg) immediately after forced swim markedly potentiated the stress-induced impairment of retention. In contrast, NAN-190 failed to affect retention when administered 2 h after forced swim or in forced swim's absence. These findings provide evidence for a NAN-190-sensitive system modulating retention that is 1) activated during a critical period shortly after exposure to swim stress, and 2) protective of memory, thereby limiting the extent to which retention is impaired by experiential stress.
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Affiliation(s)
- Allen M Schneider
- Department of Psychology, Swarthmore College, Swarthmore, Pennsylvania 19081, USA.
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231
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Czesak M, Burns AM, Remes Lenicov F, Albert PR. Characterization of rat rostral raphe primary cultures: multiplex quantification of serotonergic markers. J Neurosci Methods 2007; 164:59-67. [PMID: 17498810 DOI: 10.1016/j.jneumeth.2007.04.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Revised: 03/21/2007] [Accepted: 04/02/2007] [Indexed: 11/27/2022]
Abstract
Previous reports establishing raphe cultures typically yield less than 1% serotonin (5-HT)-positive neurons and are impractical for transcriptional studies. In this study, we have established primary cultures enriched in 5-HT neurons and quantified the proportion of cells expressing serotonergic and non-serotonergic markers. We have also shown the feasibility of using the multiplex real-time PCR technique to measure the relative amounts of RNA for some of these markers. Rostral raphe cells derived from E13-15 rat embryos were cultured for 7 days and analyzed by quantitative immunofluorescence and western blot analysis. In these cultures, approximately 8% of neurons were immunopositive for serotonergic markers (5-HT or tryptophan hydroxylase (TPH)). The percentage of cells labeled for GFAP (glial marker), tyrosine hydroxylase (catecholaminergic), and GAD65/67 (GABAergic) was 5, 1, and 54%, respectively. Transcription factors REST/NRSF and Deaf-1 were present in 9 and 98% of cells, respectively. Multiplex quantitative RT-PCR (Q-PCR) analysis was done for TPH2, 5-HT1A receptor or Deaf-1 RNAs paired with GAPDH RNA as control. Using this approach, standard curves for each RNA were obtained over 200-fold concentration range of dilution with r2 values >0.99. The relative abundances determined by Q-PCR are consistent with the expression of TPH2>Deaf-1>5-HT1A receptor RNA in serotonergic raphe cells. The standard error of TPH2 RNA levels between cultures was <20%, indicating a consistent purity of 5-HT neurons. Thus, we have generated a highly consistent and reproducible model system that is enriched in 5-HT neurons and that will be valuable in future investigation of serotonergic regulation.
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Affiliation(s)
- Margaret Czesak
- Ottawa Health Research Institute (Neuroscience), Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada K1H 8M5
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Lemos JC, Pan YZ, Ma X, Lamy C, Akanwa AC, Beck SG. Selective 5-HT receptor inhibition of glutamatergic and GABAergic synaptic activity in the rat dorsal and median raphe. Eur J Neurosci 2007; 24:3415-30. [PMID: 17229091 PMCID: PMC2837807 DOI: 10.1111/j.1460-9568.2006.05222.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The dorsal (DR) and median (MR) raphe nuclei contain 5-hydroxytryptamine (5-HT) cell bodies that give rise to the majority of the ascending 5-HT projections to the forebrain. The DR and MR have differential roles in mediating stress, anxiety and depression. Glutamate and GABA activity sculpt putative 5-HT neuronal firing and 5-HT release in a seemingly differential manner in the MR and DR, yet isolated glutamate and GABA activity within the DR and MR has not been systematically characterized. Visualized whole-cell voltage-clamp techniques were used to record excitatory and inhibitory postsynaptic currents (EPSC and IPSC) in 5-HT-containing neurons. There was a regional variation in action potential-dependent (spontaneous) and basal [miniature (m)] glutamate and GABAergic activity. mEPSC activity was greater than mIPSC activity in the DR, whereas in the MR the mIPSC activity was greater. These differences in EPSC and IPSC frequency indicate that glutamatergic and GABAergic input have distinct cytoarchitectures in the DR and MR. 5-HT(1B) receptor activation decreased mEPSC frequency in the DR and the MR, but selectively inhibited mIPSC activity only in the MR. This finding, in concert with its previously described function as an autoreceptor, suggests that 5-HT(1B) receptors influence the ascending 5-HT system through multiple mechanisms. The disparity in organization and integration of glutamatergic and GABAergic input to DR and MR neurons and their regulation by 5-HT(1B) receptors may contribute to the distinction in MR and DR regulation of forebrain regions and their differential function in the aetiology and pharmacological treatment of psychiatric disease states.
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Affiliation(s)
- Julia C. Lemos
- Department of Anaesthesiology, Children’s Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Yu-Zhen Pan
- Department of Pediatrics, 4 North ARC, room 402 A, Children’s Hospital of Philadelphia and University of Pennsylvania, 3615 Civic Center Boulevard, Philadelphia, PA 19104–4318, USA
| | - Xiaohong Ma
- Department of Pediatrics, 4 North ARC, room 402 A, Children’s Hospital of Philadelphia and University of Pennsylvania, 3615 Civic Center Boulevard, Philadelphia, PA 19104–4318, USA
| | - Christophe Lamy
- Department of Pediatrics, 4 North ARC, room 402 A, Children’s Hospital of Philadelphia and University of Pennsylvania, 3615 Civic Center Boulevard, Philadelphia, PA 19104–4318, USA
| | - Adaure C. Akanwa
- Department of Pediatrics, 4 North ARC, room 402 A, Children’s Hospital of Philadelphia and University of Pennsylvania, 3615 Civic Center Boulevard, Philadelphia, PA 19104–4318, USA
| | - Sheryl G. Beck
- Department of Pediatrics, 4 North ARC, room 402 A, Children’s Hospital of Philadelphia and University of Pennsylvania, 3615 Civic Center Boulevard, Philadelphia, PA 19104–4318, USA
- Department of Anaesthesiology, Children’s Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA 19104, USA
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233
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Bubeníková-Valesová V, Votava M, Pálenícek T, Horácek J. The opposite effect of a low and a high dose of serotonin-1A agonist on behavior induced by MK-801. Neuropharmacology 2007; 52:1071-8. [PMID: 17196227 DOI: 10.1016/j.neuropharm.2006.11.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Revised: 11/09/2006] [Accepted: 11/12/2006] [Indexed: 11/28/2022]
Abstract
The purpose of the present study was to investigate the opposite effect of the pre- and postsynaptic serotonin-1A (5-HT(1A)) receptors on the psychotic-like behavior induced by a non-competitive antagonist of the NMDA receptor, dizocilpine (MK-801). Male Wistar rats received two doses (0.025mg/kg and 1mg/kg) of 5-HT(1A) receptor agonist 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino) tetralin) and/or MK-801 in two different doses, 0.1mg/kg or 0.3mg/kg. We measured sensorimotor gating by testing prepulse inhibition of acoustic startle response (PPI) and locomotor activity of rats. We found an opposite effect of the low and high 5-HT(1A) receptor agonist doses on MK-801 induced deficit in PPI and hyperlocomotion in habituated rats. The low dose of 8-OH-DPAT, which preferentially acts on presynaptic 5-HT(1A) receptors, restored the deficit in PPI and hyperlocomotion in MK-801 (0.1mg/kg)-treated habituated rats. However, the high dose of 8-OH-DPAT, which activates both pre- and postsynaptic 5-HT(1A) receptors, decreased PPI and increased locomotor activity after administration of the low dose of MK-801. Administration of 8-OH-DPAT itself dose-dependently decreased PPI. However, only the high dose of 8-OH-DPAT increased spontaneous locomotor activity of rats. Our results indicate that there is an interaction between the NMDA and 5-HT(1A) receptors. In addition, these findings could indicate that activation of the 5-HT(1A) autoreceptor could be effective as a treatment in schizophrenia, but full potent agonism of the receptor could worsen the psychotic symptoms.
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234
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Müller CP, Carey RJ, Huston JP, De Souza Silva MA. Serotonin and psychostimulant addiction: Focus on 5-HT1A-receptors. Prog Neurobiol 2007; 81:133-78. [PMID: 17316955 DOI: 10.1016/j.pneurobio.2007.01.001] [Citation(s) in RCA: 232] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2006] [Revised: 12/04/2006] [Accepted: 01/03/2007] [Indexed: 01/03/2023]
Abstract
Serotonin(1A)-receptors (5-HT(1A)-Rs) are important components of the 5-HT system in the brain. As somatodendritic autoreceptors they control the activity of 5-HT neurons, and, as postsynaptic receptors, the activity in terminal areas. Cocaine (COC), amphetamine (AMPH), methamphetamine (METH) and 3,4-methylenedioxymethamphetamine ("Ecstasy", MDMA) are psychostimulant drugs that can lead to addiction-related behavior in humans and in animals. At the neurochemical level, these psychostimulant drugs interact with monoamine transporters and increase extracellular 5-HT, dopamine and noradrenalin activity in the brain. The increase in 5-HT, which, in addition to dopamine, is a core mechanism of action for drug addiction, hyperactivates 5-HT(1A)-Rs. Here, we first review the role of the various 5-HT(1A)-R populations in spontaneous behavior to provide a background to elucidate the contribution of the 5-HT(1A)-Rs to the organization of psychostimulant-induced addiction behavior. The progress achieved in this field shows the fundamental contribution of brain 5-HT(1A)-Rs to virtually all behaviors associated with psychostimulant addiction. Importantly, the contribution of pre- and postsynaptic 5-HT(1A)-Rs can be dissociated and frequently act in opposite directions. We conclude that 5-HT(1A)-autoreceptors mainly facilitate psychostimulant addiction-related behaviors by a limitation of the 5-HT response in terminal areas. Postsynaptic 5-HT(1A)-Rs, in contrast, predominantly inhibit the expression of various addiction-related behaviors directly. In addition, they may also influence the local 5-HT response by feedback mechanisms. The reviewed findings do not only show a crucial role of 5-HT(1A)-Rs in the control of brain 5-HT activity and spontaneous behavior, but also their complex role in the regulation of the psychostimulant-induced 5-HT response and subsequent addiction-related behaviors.
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Affiliation(s)
- Christian P Müller
- Institute of Physiological Psychology I, University of Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany.
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235
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Jacobs C, Van Den Broeck W, Simoens P. Neurons expressing serotonin-1B receptor in the basolateral nuclear group of the amygdala in normally behaving and aggressive dogs. Brain Res 2007; 1136:102-9. [PMID: 17223093 DOI: 10.1016/j.brainres.2006.11.096] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Revised: 11/17/2006] [Accepted: 11/27/2006] [Indexed: 01/09/2023]
Abstract
The present study aimed to quantify neurons expressing the serotonin-1B receptor and evaluate numerical differences in normally behaving and pathologically aggressive dogs in order to assess whether the serotonin-1B receptor is involved in pathological canine aggression. Because previous studies have reported structural alterations in the basolateral nuclear group (BNG) of the amygdaloid body of aggressive dogs, this structure was selected as region of interest in the present study. Indirect immunohistochemistry was applied to visualise the serotonin-1B-receptor-positive neurons. Immunoreactivity was located predominantly within the neuronal cell bodies and adjacent neuronal processes. In the aggressive dogs the BNGs contained a significantly higher number of serotonin-1B-receptor-positive neurons compared to the normally behaving dogs. This number was strongly correlated with the total number of neurons per BNG, which was also significantly increased in aggressive dogs compared to normal dogs. The percentage of neurons expressing the serotonin-1B receptor did not differ significantly between both groups. No significant asymmetries were observed for the number and percentage of serotonin-1B-receptor-positive neurons. Potential relationships between the present findings and the etiology of aggressive behaviour, the neuroprotective role of the serotonin-1B receptor and receptor dysfunction are discussed.
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Affiliation(s)
- C Jacobs
- Department of Morphology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
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236
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Muller JF, Mascagni F, McDonald AJ. Serotonin-immunoreactive axon terminals innervate pyramidal cells and interneurons in the rat basolateral amygdala. J Comp Neurol 2007; 505:314-35. [PMID: 17879281 DOI: 10.1002/cne.21486] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The basolateral nuclear complex of the amygdala (BLC) receives a dense serotonergic innervation that appears to play a critical role in the regulation of mood and anxiety. However, little is known about how serotonergic inputs interface with different neuronal subpopulations in this region. To address this question, dual-labeling immunohistochemical techniques were used at the light and electron microscopic levels to examine inputs from serotonin-immunoreactive (5-HT+) terminals to different neuronal subpopulations in the rat BLC. Pyramidal cells were labeled by using antibodies to calcium/calmodulin-dependent protein kinase II, whereas different interneuronal subpopulations were labeled by using antibodies to a variety of interneuronal markers including parvalbumin (PV), vasoactive intestinal peptide (VIP), calretinin, calbindin, cholecystokinin, and somatostatin. The BLC exhibited a dense innervation by thin 5-HT+ axons. Electron microscopic examination of the anterior basolateral nucleus (BLa) revealed that 5-HT+ axon terminals contained clusters of small synaptic vesicles and a smaller number of larger dense-core vesicles. Serial section reconstruction of 5-HT+ terminals demonstrated that 76% of these terminals formed synaptic junctions. The great majority of these synapses were symmetrical. The main targets of 5-HT+ terminals were spines and distal dendrites of pyramidal cells. However, in light microscopic preparations it was common to observe apparent contacts between 5-HT+ terminals and all subpopulations of BLC interneurons. Electron microscopic analysis of the BLa in sections dual-labeled for 5-HT/PV and 5-HT/VIP revealed that many of these contacts were synapses. These findings suggest that serotonergic axon terminals differentially innervate several neuronal subpopulations in the BLC.
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Affiliation(s)
- Jay F Muller
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, South Carolina 29208, USA
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237
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Samadi P, Rouillard C, Bédard PJ, Di Paolo T. Functional neurochemistry of the basal ganglia. HANDBOOK OF CLINICAL NEUROLOGY 2007; 83:19-66. [DOI: 10.1016/s0072-9752(07)83002-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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238
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Birthelmer A, Ehret A, Riegert C, Rothmaier AK, Leemhuis J, Jackisch R. Modulation of electrically evoked serotonin release in cultured rat raphe neurons. J Neurochem 2006; 100:1613-25. [PMID: 17348865 DOI: 10.1111/j.1471-4159.2006.04287.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Electrically evoked release of serotonin (5-HT) and its modulation via 5-HT autoreceptors and alpha(2)-heteroreceptors was studied in primary cell cultures prepared from the embryonic (ED 15) rat mesencephalic brain region comprising the raphe nuclei. Cultures were grown for up to 3 weeks on circular glass coverslips. They developed a dense network of non-neuronal and neuronal cells, some of which were positive for tryptophan hydroxylase. To measure 5-HT release, the cultures were pre-incubated with [(3)H]5-HT (in the presence of the selective noradrenaline reuptake inhibitor oxaprotiline [1 micromol/L]), superfused with modified Krebs-Henseleit medium containing 6-nitroqipazine [1 micromol/L] and electrically stimulated using two conditions. Condition A: 360 pulses, 3 Hz, 0.5 ms, 90 mA, or condition B: 4 pulses 100 Hz, 0.5 ms, 90 mA (a condition which diminishes interactions with endogenously released transmitters during ongoing stimulation). After only 1 week in culture, the electrically evoked overflow of [(3)H] was Ca(2+) dependent and tetrodotoxin sensitive, suggesting an action-potential-induced exocytotic release of 5-HT. Using stimulation condition A in cultures grown for 2 weeks, both basal and evoked 5-HT release were strongly enhanced by methiotepine (1 micromol/L) but unaffected by the 5-HT(1B) autoreceptor agonist CP-93, 129 (1 micromol/L) and the alpha(2)-adrenoceptor agonist UK-14, 304 (1 micromol/L). Conversely, using stimulation condition B, not only CP-93, 129 (IC(50) 8.1 +/- 1.4 nmol/L) and UK-14, 304 (IC(50) 14.9 +/- 1.6 nmol/L) had inhibitory effects on cells grown for 2 weeks, but also the 5-HT(1A) agonist 8-hydroxy-2-(di-n-propylamino)tetralin. In conclusion, we describe for the first time electrically evoked release of 5-HT from primary cultures of fetal raphe cells and its modulation via 5-HT(1B) and 5-HT(1A) auto- and alpha(2)-heteroreceptors. Such cultured raphe cells may represent a suitable model to study expression and development of presynaptic receptors on serotonergic neurons in-vitro.
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Affiliation(s)
- Anja Birthelmer
- Institute for Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Laboratory of Neuropharmacology, Freiburg, Germany
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239
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Aznavour N, Zimmer L. [18F]MPPF as a tool for the in vivo imaging of 5-HT1A receptors in animal and human brain. Neuropharmacology 2006; 52:695-707. [PMID: 17101155 DOI: 10.1016/j.neuropharm.2006.09.023] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Revised: 09/21/2006] [Accepted: 09/29/2006] [Indexed: 11/18/2022]
Abstract
Serotonin (5-hydroxytryptamine, 5-HT) and its various receptors are involved in numerous CNS functions and psychiatric disorders. 5-HT(1A), the best-characterized subtype of currently known 5-HT receptors, is tightly implicated in the pathogenesis of depression, anxiety, epilepsy and eating disorders. It thus represents an important target for drug therapy. Specific radioligands and positron emission tomography (PET) allow for a quantitative imaging of brain 5-HT(1A) receptor distribution in living animals and humans. Recently, the selective 5-HT(1A) receptor antagonist, MPPF, has been successfully labeled with [(18)F]fluorine ([(18)F]MPPF), and an increasing number of academic and industry centres have used this radiotracer in preclinical and clinical studies. After a brief account of some of the structural, distributional and electrophysiological characteristics of brain 5-HT(1A) receptors, this review focuses on studies conducted with [(18)F]MPPF, with emphasis on preclinical results illustrating the actual and potential value of this PET radioligand for clinical research and drug development.
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Affiliation(s)
- Nicolas Aznavour
- Laboratoire de Neuropharmacologie, Université Lyon 1, Lyon, France
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240
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Aznavour N, Rbah L, Riad M, Reilhac A, Costes N, Descarries L, Zimmer L. A PET imaging study of 5-HT1A receptors in cat brain after acute and chronic fluoxetine treatment. Neuroimage 2006; 33:834-42. [PMID: 16996750 DOI: 10.1016/j.neuroimage.2006.08.012] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Revised: 08/04/2006] [Accepted: 08/05/2006] [Indexed: 11/28/2022] Open
Abstract
Immuno-electron microscopic and beta-microprobe studies have demonstrated that the internalization of serotonin 5-HT(1A) autoreceptors, after acute treatment with the selective 5-HT(1A) receptor agonist 8-OH-DPAT or with the specific serotonin reuptake inhibitor (SSRI) fluoxetine, is associated with a marked decrease in the in vivo binding of [(18)F]MPPF in the nucleus raphe dorsalis (NRD) of rat. To determine whether this event might be amenable to brain imaging, the present [(18)F]MPPF positron emission tomographic (PET) study was carried out in anesthetized cats given or not a single dose (5 mg/kg, i.v.) or chronically treated with fluoxetine (5 mg/kg, s.c. for 21 days). Compared to control, [(18)F]MPPF binding potential was considerably (and visibly) decreased in the cat NRD after acute fluoxetine treatment, while it remained unchanged in other brain regions. Unexpectedly, after chronic fluoxetine treatment, [(18)F]MPPF binding potential was not affected in any brain region. In parallel immuno-electron microscopic experiments carried out in rat, the density of 5-HT(1A) autoreceptors on the plasma membrane of NRD dendrites was comparable to control after chronic fluoxetine treatment. If the decrease in [(18)F]MPPF binding at the onset of SSRI treatment was detectable by PET imaging, it could potentially serve as a biological index of efficacy.
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Affiliation(s)
- Nicolas Aznavour
- Laboratoire de Neuropharmacologie, Faculté de Pharmacie, Université Lyon 1, Lyon, France
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241
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Alex KD, Pehek EA. Pharmacologic mechanisms of serotonergic regulation of dopamine neurotransmission. Pharmacol Ther 2006; 113:296-320. [PMID: 17049611 PMCID: PMC2562467 DOI: 10.1016/j.pharmthera.2006.08.004] [Citation(s) in RCA: 413] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Accepted: 08/24/2006] [Indexed: 01/19/2023]
Abstract
The neurotransmitter dopamine (DA) has a long association with normal functions such as motor control, cognition, and reward, as well as a number of syndromes including drug abuse, schizophrenia, and Parkinson's disease. Studies show that serotonin (5-HT) acts through several 5-HT receptors in the brain to modulate DA neurons in all 3 major dopaminergic pathways. There are at least fourteen 5-HT receptor subtypes, many of which have been shown to play some role in mediating 5-HT/DA interactions. Several subtypes, including the 5-HT1A, 5-HT1B, 5-HT2A, 5-HT3 and 5-HT4 receptors, act to facilitate DA release, while the 5-HT2C receptor mediates an inhibitory effect of 5-HT on DA release. Most 5-HT receptor subtypes only modulate DA release when 5-HT and/or DA neurons are stimulated, but the 5-HT2C receptor, characterized by high levels of constitutive activity, inhibits tonic as well as evoked DA release. This review summarizes the anatomical evidence for the presence of each 5-HT receptor subtype in dopaminergic regions of the brain and the neuropharmacological evidence demonstrating regulation of each DA pathway. The relevance of 5-HT receptor modulation of DA systems to the development of therapeutics used to treat schizophrenia, depression, and drug abuse is discussed. Lastly, areas are highlighted in which future research would be maximally beneficial to the treatment of these disorders.
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Affiliation(s)
- K D Alex
- Department of Neurosciences, Case Western Reserve School of Medicine, Cleveland, OH 44106, USA
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242
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Lacoste B, Riad M, Descarries L. Immunocytochemical evidence for the existence of substance P receptor (NK1) in serotonin neurons of rat and mouse dorsal raphe nucleus. Eur J Neurosci 2006; 23:2947-58. [PMID: 16819984 DOI: 10.1111/j.1460-9568.2006.04833.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In addition to its neurotransmitter/modulator role in pain perception, substance P (SP) is involved in a regulation of mood, as antagonists of its neurokinin-1 receptor (NK1r) have been found to have antidepressant-like effects in humans. In rodents, treatment with NK1r antagonists has been shown to increase the firing of dorsal raphe nucleus (DRN) serotonin (5-hydroxytryptamine, 5-HT) neurons and to induce a desensitization of their 5-HT1A autoreceptors, suggesting local interactions between the SP and 5-HT systems. To search for the presence of NK1r on 5-HT neurons of the DRN, we used light and electron microscopic immunocytochemistry, as well as confocal microscopy, after single- and double-labelling of NK1r and of the biosynthetic enzyme of 5-HT, tryptophan hydroxylase (TpOH). A significant number of 5-HT (TpOH-positive) cell bodies and dendrites endowed with NK1r were thus demonstrated in the caudal part of rat and mouse DRN. As visualized by electron microscopy after gold immunolabelling, NK1r was mostly cytoplasmic in 5-HT neurons, while predominating on the plasma membrane in the case of TpOH-negative dendrites. The proportion of NK1r observed on the plasma membrane of 5-HT neurons was, however, slightly higher in mouse than rat. Thus, in both rat and mouse DRN, a subpopulation of 5-HT neurons is endowed with NK1r receptors and may be directly involved in the antidepressant-like effects of NK1r antagonists. These 5-HT neurons represent a new element in the neuronal circuitry currently proposed to account for the role of SP in mood regulation.
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Affiliation(s)
- Baptiste Lacoste
- Département de pathologie et biologie cellulaire, and Centre de recherche en sciences neurologiques, Faculté de médecine, Université de Montréal, Montreal, Quebec, Canada H3C 3J7
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243
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Carrel D, Hamon M, Darmon M. Role of the C-terminal di-leucine motif of 5-HT1A and 5-HT1B serotonin receptors in plasma membrane targeting. J Cell Sci 2006; 119:4276-84. [PMID: 17003106 DOI: 10.1242/jcs.03189] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 5-HT1A and 5-HT1B serotonin receptors exhibit different subcellular localizations in neurons. Evidence has been reported that the C-terminal domain is involved in the somato-dendritic and axonal targeting of 5-HT1AR and 5-HT1BR, respectively. Here we analyzed the consequences of the mutation of a di-leucine motif and palmitoylated cysteines within this domain. Replacement of I414-I415 by a di-alanine in 5-HT1AR led to endoplasmic reticulum (ER) sequestration of the corresponding mutant expressed in cell lines as well as in hippocampal neurons in culture. Furthermore, di-leucine-mutated receptors were unable to bind 5-HT1A agonists and presented a major deficit in their glycosylation state, suggesting that they are misfolded. By contrast, mutation of the di-leucine motif in the C-terminal domain of 5-HT1BR had no major consequence on its subcellular targeting. However, in the case of the 1ActB chimera (substitution of the C-terminal domain of the 5-HT1BR into 5-HT1AR), this mutation was also found to cause sequestration within the ER. Replacement of palmitoylated cysteines by serines had no consequence on either receptor type. These data indicate that the di-leucine motif of the 5-HT1AR and 5-HT1BR tails is implicated in proper folding of these receptors, which is necessary for their ER export.
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MESH Headings
- Amino Acid Sequence
- Animals
- Binding Sites/genetics
- COS Cells
- Cell Membrane/metabolism
- Cells, Cultured
- Chlorocebus aethiops
- Cysteine/genetics
- Cysteine/metabolism
- Endoplasmic Reticulum/metabolism
- Fluorescent Antibody Technique, Indirect/methods
- Leucine/genetics
- Leucine/metabolism
- Leucine/physiology
- Molecular Sequence Data
- Mutation/genetics
- Protein Binding
- Protein Transport/drug effects
- Receptor, Serotonin, 5-HT1A/genetics
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptor, Serotonin, 5-HT1B/genetics
- Receptor, Serotonin, 5-HT1B/metabolism
- Serotonin 5-HT1 Receptor Agonists
- Serotonin Receptor Agonists/pharmacology
- Swine
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Affiliation(s)
- Damien Carrel
- INSERM, U677, University Pierre et Marie Curie, Paris 75013, France
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244
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Bockaert J, Claeysen S, Bécamel C, Dumuis A, Marin P. Neuronal 5-HT metabotropic receptors: fine-tuning of their structure, signaling, and roles in synaptic modulation. Cell Tissue Res 2006; 326:553-72. [PMID: 16896947 DOI: 10.1007/s00441-006-0286-1] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Accepted: 06/13/2006] [Indexed: 12/31/2022]
Abstract
Serotonin (5-hydroxytryptamine, 5-HT) is, without doubt, the neurotransmitter for which the number of receptors is the highest. Fifteen genes encoding functional 5-HT receptors have been cloned in mammalian brain. 5-HT(3) receptors are ionotropic receptors, whereas all the others are metabotropic G-protein-coupled receptors (GPCRs). 5-HT receptor diversity is further increased by post-genomic modifications, such as alternative splicing (up to 10 splice variants for the 5-HT(4) receptor) or by mRNA editing in the case of 5-HT(2C) receptors. The cellular and behavioral implications of 5-HT(2C) receptor editing are of great physiological importance. Signaling of 5-HT receptors involves a great variety of pathways, but only some of these have been demonstrated in neurons. The classical view of neurotransmitter receptors localized within the synaptic cleft cannot be applied to 5-HT receptors, which are mostly (but not exclusively) localized at extra-synaptic locations either pre- or post-synaptically. 5-HT receptors are engaged in pre- or post-synaptic complexes composed of many GPCR-interacting proteins. The functions of these proteins are starting to be revealed. These proteins have been implicated in targeting, trafficking to or from the membrane, desensitization, and fine-tuning of signaling.
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245
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Lanoir J, Hilaire G, Seif I. Reduced density of functional 5-HT1A receptors in the brain, medulla and spinal cord of monoamine oxidase-A knockout mouse neonates. J Comp Neurol 2006; 495:607-23. [PMID: 16498683 DOI: 10.1002/cne.20916] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Abnormally high brain 5-HT levels in monoamine oxidase-A knockout (MAO-A KO) mouse neonates raise the question of whether the distribution and density of the 5-HT1A receptors (5-HT1AR) expressed in the brain by postnatal day P7 are affected and, if so, whether the 5-HT1A autoreceptors in the dorsal raphe are modified in the same way as the postsynaptic 5-HT1AR present in raphe target structures. [3H]8-OH-DPAT binding and quantitative autoradiography were performed to answer these questions. Binding specificity was first confirmed in adult wild-type mice and rat brain sections. 5-HT1AR binding was then analyzed in four MAO-A mutant vs. five wild-type neonatal brains, from olfactory bulb to cervical cord. Among 12 structures expressing postsynaptic 5-HT1AR in wild-type neonates, the highest densities involved the retrosplenial cortex, entorhinal cortex, and septum (52-46 fmol/mg tissue); low densities occurred in the hippocampus and spinal cord (24 fmol/mg tissue); in addition, the raphe autoreceptor density was only 20 fmol/mg tissue. In mutants, the distribution of postsynaptic 5-HT1AR was unchanged, but an overall decrease in density occurred (-32% to -63%); the raphe autoreceptors decreased in mutants by at least -79%. Data are discussed with reference to the ectopic 5-HT uptake and accumulation reported to occur during the first 10 postnatal days in wild-type and MAO-A KO mice. As previously suggested to explain the raphe autoreceptor loss in 2-month-old MAO-A KO mice, the overall 5-HT1AR down-regulation in mutant pups probably results from extracellular 5-HT excess in both raphe and target structures. The greater the 5-HT excess, the more the functional receptor density decreases.
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Affiliation(s)
- Jeanne Lanoir
- Centre National de la Recherche Scientifíque-Groupe d'Etude des Reseaux Moteurs et Université de la Méditerranée, F-13009 Marseille, France.
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246
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Villalba RM, Raju DV, Hall RA, Smith Y. GABA(B) receptors in the centromedian/parafascicular thalamic nuclear complex: an ultrastructural analysis of GABA(B)R1 and GABA(B)R2 in the monkey thalamus. J Comp Neurol 2006; 496:269-87. [PMID: 16538684 DOI: 10.1002/cne.20950] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Strong gamma-aminobutyric acid type B (GABA(B)) receptor binding has been shown throughout the thalamus, but the distribution of the two GABA(B) receptor subunits, GABA(B) receptor subunit 1 (GABA(B)R1) and GABA(B) receptor subunit 2 (GABA(B)R2), remains poorly characterized. In primates, the caudal intralaminar nuclei, centromedian and parafascicular (CM/PF), are an integral part of basal ganglia circuits and a main source of inputs to the striatum. In this study, we analyzed the subcellular and subsynaptic distribution of GABA(B) receptor subunits by using light and electron microscopic immunocytochemical techniques. Quantitative immunoperoxidase and immunogold analysis showed that both subunits display a similar pattern of distribution in CM/PF, being expressed largely at extrasynaptic and perisynaptic sites in neuronal cell bodies, dendrites, and axon-like processes and less abundantly in axon terminals. Postsynaptic GABA(B)R1 labeling was found mostly on the plasma membrane (70-80%), whereas GABA(B)R2 was more evenly distributed between the plasma membrane and intracellular compartments of CM/PF neurons. A few axon terminals forming symmetric and asymmetric synapses were also labeled for GABA(B)R1 and GABA(B)R2, but the bulk of presynaptic labeling was expressed in small axon-like processes. About 20% of presynaptic vesicle-containing dendrites of local circuit neurons displayed GABA(B)R1/R2 immunoreactivity. Vesicular glutamate transporters (vGluT1)-containing terminals forming asymmetric synapses expressed GABA(B)R1 and/or displayed postsynaptic GABA(B)R1 at the edges of their asymmetric specialization. Overall, these findings provide evidence for multiple sites where GABA(B) receptors could modulate GABAergic and glutamatergic transmission in the primate CM/PF complex.
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Affiliation(s)
- Rosa M Villalba
- Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30322, USA.
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247
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Abstract
Monoaminergic systems, and in particular serotoninergic neurons of the raphe system, have been involved in the physiopathology and treatment of major depression in a great number of studies. One of the most reproducible effects of antidepressant treatment is the increase of central 5-HT (serotonin) tone. However, the identification of novel potential therapeutic targets (neurohormones, neuropeptides) for treating depression has led to elaborating novel cellular and molecular concepts accounting for stress-related mood disorders. In particular, recent studies have demonstrated that chronic administration of all classes of antidepressants up-regulates neurogenesis in adult rodent hippocampus. The possibility that structural remodelling may contribute to the physiopathology of mood disorders provides new avenues of research toward understanding the cellular basis of mood disorders.
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Affiliation(s)
- Laurence Lanfumey
- UMR 677; INSERM-UPMC, Faculté de Médecine Pitié-Salpêtrière, Paris, France.
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248
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Grimes JM, Melloni RH. Serotonin-1B receptor activity and expression modulate the aggression-stimulating effects of adolescent anabolic steroid exposure in hamsters. Behav Neurosci 2006; 119:1184-94. [PMID: 16300425 DOI: 10.1037/0735-7044.119.5.1184] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Repeated high dose (5.0 mg/kg) anabolic-androgenic steroid (AAS) exposure during adolescence stimulates offensive aggression in male Syrian hamsters. These studies examined whether AAS-induced aggression was regulated by the activity of serotonin (5HT) type-1B receptors and correlated with altered 5HT1B expression. AAS-treated hamsters were tested for offensive aggression following the administration of the 5HT1B agonist anpirtoline (0.125-0.5 mg/kg). Anpirtoline dose-dependently reduced select components of the AAS-induced aggressive response, with significant reductions observed at 0.25 mg/kg. Aggressive, AAS-treated hamsters showed significant decreases in the area covered by 5HT1B-containing neuronal puncta and increases in the number of 5HT1B-containing neuronal somata in select brain regions implicated in aggression control. Together, these data support a role for site-specific alterations in 5HT1B signaling and expression in adolescent AAS-induced aggression.
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Affiliation(s)
- Jill M Grimes
- Behavioral Neuroscience Program, Department of Psychology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
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249
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Kocsis B, Varga V, Dahan L, Sik A. Serotonergic neuron diversity: identification of raphe neurons with discharges time-locked to the hippocampal theta rhythm. Proc Natl Acad Sci U S A 2006; 103:1059-64. [PMID: 16418294 PMCID: PMC1347988 DOI: 10.1073/pnas.0508360103] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The serotonergic system plays a key role in the regulation of brain states, and many of the known features of serotonergic neurons appear to match this function. Midbrain raphe nuclei provide a diffuse projection to all regions of the forebrain, and raphe neurons exhibit a slow metronome-like activity that sets the ambient levels of serotonin across the sleep-wake cycle. Serotonergic cells have also been implicated, however, in a variety of more specific functions that can hardly be related to their low-rate monotonous patterns of discharges. The amazing variety of serotonergic receptors and their type-specific distribution on cortical neurons also raise the possibility of a more intimate coordination between the activity of serotonergic neurons and their target cortical circuits. Here we report an unexpected diversity in the behavior of immunohistochemically identified serotonergic neurons. Two outstanding subpopulations were identified by using the in vivo juxtacellular recording and labeling technique. The first subpopulation of serotonergic cells exhibited the classic clock-like activity with no apparent short timescale interaction with the hippocampal electroencephalogram. The other subpopulation discharged action potentials that were phase-locked to the hippocampal theta rhythm, the oscillatory pattern associated with acquisition of information and memory formation. These results indicate that the ascending serotonergic system comprises cells involved in complex information processing beyond the regulation of state transitions. The heterogeneity of serotonergic neuron behavior can also help to explain the complexity of symptoms associated with serotonergic dysfunction.
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Affiliation(s)
- Bernat Kocsis
- Laboratory of Neurophysiology, Harvard Medical School, Boston, MA 02215, USA
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Mengod G, Vilaró MT, Cortés R, López-Giménez JF, Raurich A, Palacios JM. Chemical Neuroanatomy of 5-HT Receptor Subtypes in the Mammalian Brain. THE SEROTONIN RECEPTORS 2006. [DOI: 10.1007/978-1-59745-080-5_10] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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