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Flores-Burgess A, Millón C, Gago B, García-Durán L, Cantero-García N, Coveñas R, Narváez JA, Fuxe K, Santín L, Díaz-Cabiale Z. Galanin (1–15)-fluoxetine interaction in the novel object recognition test. Involvement of 5-HT1A receptors in the prefrontal cortex of the rats. Neuropharmacology 2019; 155:104-112. [DOI: 10.1016/j.neuropharm.2019.05.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Revised: 04/07/2019] [Accepted: 05/18/2019] [Indexed: 10/26/2022]
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Activation of 5-HT₁A receptors in the medial subdivision of the central nucleus of the amygdala produces anxiolytic effects in a rat model of Parkinson's disease. Neuropharmacology 2015; 95:181-91. [PMID: 25797491 DOI: 10.1016/j.neuropharm.2015.03.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 03/02/2015] [Accepted: 03/09/2015] [Indexed: 11/21/2022]
Abstract
Although the medial subdivision of the central nucleus of the amygdala (CeM) and serotonin-1A (5-HT1A) receptors are involved in the regulation of anxiety, their roles in Parkinson's disease (PD)-associated anxiety are still unknown. Here we assessed the importance of CeM 5-HT1A receptors for anxiety in rats with unilateral 6-hydroxydopamine (6-OHDA) lesion of the medial forebrain bundle (MFB). The lesion induced anxiety-like behaviors, increased the firing rate and burst-firing pattern of CeM γ-aminobutyric acid (GABA) neurons, as well as decreased dopamine (DA) levels in the striatum, medial prefrontal cortex (mPFC), amygdala and ventral part of hippocampus (vHip). Intra-CeM injection of the selective 5-HT1A receptor agonist 8-OH-DPAT produced anxiolytic effects in the lesioned rats, and decreased the firing rate of CeM GABAergic neurons in two groups of rats. Compared to sham-operated rats, the duration of the inhibitory effect on the firing rate of GABAergic neurons was shortened in the lesioned rats. The injection increased DA levels in the mPFC and amygdala in two groups of rats and the vHip in the lesioned rats, and increased 5-HT level in the lesioned rats, whereas it decreased NA levels in the mPFC in two groups of rats and the vHip in the lesioned rats. Moreover, the mean density of 5-HT1A receptor and GABA double-labeled neurons in the CeM was reduced after the lesioning. These results suggest that activation of CeM 5-HT1A receptor produces anxiolytic effects in the 6-OHDA-lesioned rats, which involves decreased firing rate of the GABAergic neurons, and changed monoamine levels in the limbic and limbic-related brain regions.
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Woodard GE, Jardín I, Berna-Erro A, Salido GM, Rosado JA. Regulators of G-protein-signaling proteins: negative modulators of G-protein-coupled receptor signaling. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 317:97-183. [PMID: 26008785 DOI: 10.1016/bs.ircmb.2015.02.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Regulators of G-protein-signaling (RGS) proteins are a category of intracellular proteins that have an inhibitory effect on the intracellular signaling produced by G-protein-coupled receptors (GPCRs). RGS along with RGS-like proteins switch on through direct contact G-alpha subunits providing a variety of intracellular functions through intracellular signaling. RGS proteins have a common RGS domain that binds to G alpha. RGS proteins accelerate GTPase and thus enhance guanosine triphosphate hydrolysis through the alpha subunit of heterotrimeric G proteins. As a result, they inactivate the G protein and quickly turn off GPCR signaling thus terminating the resulting downstream signals. Activity and subcellular localization of RGS proteins can be changed through covalent molecular changes to the enzyme, differential gene splicing, and processing of the protein. Other roles of RGS proteins have shown them to not be solely committed to being inhibitors but behave more as modulators and integrators of signaling. RGS proteins modulate the duration and kinetics of slow calcium oscillations and rapid phototransduction and ion signaling events. In other cases, RGS proteins integrate G proteins with signaling pathways linked to such diverse cellular responses as cell growth and differentiation, cell motility, and intracellular trafficking. Human and animal studies have revealed that RGS proteins play a vital role in physiology and can be ideal targets for diseases such as those related to addiction where receptor signaling seems continuously switched on.
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Affiliation(s)
- Geoffrey E Woodard
- Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, Bethesda, MD, USA
| | - Isaac Jardín
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - A Berna-Erro
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - Gines M Salido
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - Juan A Rosado
- Department of Physiology, University of Extremadura, Caceres, Spain
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Dorsomedial hypothalamus serotonin 1A receptors mediate a panic-related response in the elevated T-maze. Brain Res Bull 2014; 109:39-45. [DOI: 10.1016/j.brainresbull.2014.09.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 09/23/2014] [Accepted: 09/24/2014] [Indexed: 11/22/2022]
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de Bortoli VC, Yamashita PSDM, Zangrossi H. 5-HT1A and 5-HT2A receptor control of a panic-like defensive response in the rat dorsomedial hypothalamic nucleus. J Psychopharmacol 2013; 27:1116-23. [PMID: 23787365 DOI: 10.1177/0269881113492900] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The dorsomedial nucleus of the hypothalamus (DMH) has long been implicated in the genesis/regulation of escape, a panic-related defensive behavior. In the dorsal periaqueductal gray matter (dPAG), another key panic-associated area, serotonin, through the activation of 5-HT1A and 5-HT2A receptors, exerts an inhibitory role on escape expression. This panicolytic-like effect is facilitated by chronic treatment with clinically effective antipanic drugs such as fluoxetine and imipramine. It is still unclear whether serotonin within the DMH plays a similar regulatory action. The results showed that intra-DMH injection of the 5-HT1A receptor agonist 8-OH-DPAT, the preferential 5-HT2A receptor agonist DOI, but not the 5-HT2C agonist MK-212, inhibited the escape reaction of male Wistar rats evoked by electrical stimulation of the DMH. Local microinjection of the 5-HT1A antagonist WAY-100635 or the preferential 5-HT2A antagonist ketanserin was ineffective. Whereas chronic (21 days) systemic treatment with imipramine potentiated the anti-escape effect of both 8-OH-DPAT and DOI, repeated administration of fluoxetine enhanced the effect of the latter agonist. The results indicate that 5-HT1A and 5-HT2A receptors within the DMH play a phasic inhibitory role upon escape expression, as previously reported in the dPAG. Facilitation of 5-HT-mediated neurotransmission in the DMH may be implicated in the mode of action of antipanic drugs.
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Burghardt N, Bauer E. Acute and chronic effects of selective serotonin reuptake inhibitor treatment on fear conditioning: Implications for underlying fear circuits. Neuroscience 2013; 247:253-72. [DOI: 10.1016/j.neuroscience.2013.05.050] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 05/14/2013] [Accepted: 05/20/2013] [Indexed: 12/24/2022]
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Li Q, Sullivan NR, McAllister CE, Van de Kar LD, Muma NA. Estradiol accelerates the effects of fluoxetine on serotonin 1A receptor signaling. Psychoneuroendocrinology 2013; 38:1145-57. [PMID: 23219224 PMCID: PMC3610798 DOI: 10.1016/j.psyneuen.2012.11.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 11/05/2012] [Accepted: 11/05/2012] [Indexed: 11/17/2022]
Abstract
A major problem with current anti-depressant therapy is that it takes on average 6-7 weeks for remission. Since desensitization of serotonin (5-HT)1A receptor signaling contributes to the anti-depressive response, acceleration of the desensitization may reduce this delay in response to antidepressants. The purpose of the present study was to test the hypothesis that estradiol accelerates fluoxetine-induced desensitization of 5-HT1A receptor signaling in the paraventricular nucleus of the hypothalamus (PVN) of rats, via alterations in components of the 5-HT1A receptor signaling pathway. Ovariectomized rats were injected with estradiol and/or fluoxetine, then adrenocorticotropic hormone (ACTH) and oxytocin responses to a 5-HT1A receptor agonist (+)-8-hydroxy-2-dipropylaminotetralin (8-OH-DPAT) were examined to assess the function of 5-HT1A receptors in the PVN. Treatment with estradiol for either 2 or 7 days or fluoxetine for 2 days produced at most a partial desensitization of 5-HT1A receptor signaling, whereas 7 days of fluoxetine produced full desensitization. Combined treatment with estradiol and fluoxetine for 2 days produced nearly a full desensitization, demonstrating an accelerated response compared to either treatment alone. With two days of combined treatments, estradiol prevented the fluoxetine-induced increase in 5-HT1A receptor protein, which could contribute to the more rapid desensitization. Furthermore, EB treatment for 2 days decreased the abundance of the 35 kD Gαz protein which could contribute to the desensitization response. We found two isoforms of Gαz proteins with molecular mass of 35 and 33 kD, which differentially distributed in the detergent resistant microdomain (DRM) and in Triton X-100 soluble membrane region, respectively. The 35 kD Gαz proteins in the DRM can be sumoylated by SUMO1. Stimulation of 5-HT1A receptors with 8-OH-DPAT increases the sumoylation of Gαz proteins and reduces the 33 kD Gαz proteins, suggesting that these responses may be related to the desensitization of 5-HT1A receptors. Treatment with estradiol for 2 days also reduced the levels of the G-protein coupled estrogen receptor GPR30, possibly limiting to the ability of estradiol to produce only a partial desensitization response. These data provide evidence that estradiol may be effective as a short-term adjuvant to SSRIs to accelerate the onset of therapeutic effects.
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Affiliation(s)
- Qian Li
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, KS
| | - Nicole R. Sullivan
- Department of Pharmacology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Carrie E. McAllister
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, KS
| | - Louis D Van de Kar
- Department of Pharmacology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Nancy A. Muma
- Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, KS,Corresponding author: Nancy A. Muma, Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, 1251 Wescoe Hall Drive, 5064 Malott Hall, Lawrence, Kansas 66045, , Phone: 785-864-4002, Fax: 785-864-5219
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Li Q, Luo T, Jiang X, Wang J. Anxiolytic effects of 5-HT₁A receptors and anxiogenic effects of 5-HT₂C receptors in the amygdala of mice. Neuropharmacology 2011; 62:474-84. [PMID: 21925519 DOI: 10.1016/j.neuropharm.2011.09.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 09/02/2011] [Accepted: 09/03/2011] [Indexed: 01/14/2023]
Abstract
The aim of the present study is to test a hypothesis that 5-HT(1A) and 5-HT(2C) receptors in the amygdala play an important role in the regulation of anxiety behaviors. We examined alterations in anxiety-like behaviors after manipulation of the expression of 5-HT(1A) and 5-HT(2C) receptors in the amygdala using recombinant adenovirus approaches. Recombinant adenoviruses containing a 5-HT(1A) promoter-controlled 5-HT(1A) antisense sequence or a 5-HT(2C) promoter-controlled 5-HT(2C) sense sequence were injected into the amygdala. Elevated plus-maze (EPM) and open field tests were conducted to determine anxiety-like behavior and locomotor activity. Reductions in the expression of 5-HT(1A) receptors in the amygdala significantly attenuated the time spent in the open arms of EPM and time spent in the center of an open field. Reduction in the percent of time spent in the open arms of EPM is negatively correlated with the density of 5-HT(1A) receptors in the central amygdala. On the other hand, increased expression of 5-HT(2C) receptors reduced the time spent in the open arms of EPM and time spent in the center of an open field. The reductions in the time spent and distance traveled in the open arms of EPM were correlated to the density of 5-HT(2C) receptors in the basolateral nucleus of amygdala. These data suggest that amygdaloid 5-HT(1A) receptors produce anxiolytic and 5-HT(2C) receptors produce anxiogenic effects. Together, the present results demonstrate the important role of the amygdaloid 5-HT(1A) and 5-HT(2C) receptors in the regulation of anxiety-like behaviors. This article is part of a Special Issue entitled 'Anxiety and Depression'.
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Affiliation(s)
- Qian Li
- Department of Psychiatry and Behavioral Sciences, University of Texas Medical Branch, Galveston, TX, USA.
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Chan JSW, Snoeren EMS, Cuppen E, Waldinger MD, Olivier B, Oosting RS. The serotonin transporter plays an important role in male sexual behavior: a study in serotonin transporter knockout rats. J Sex Med 2011; 8:97-108. [PMID: 20704641 DOI: 10.1111/j.1743-6109.2010.01961.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Serotonin (5-HT) is an important neurotransmitter for sexual behaviors. Heterozygous (+/-) serotonin transporter (SERT) rats and SERT knockout rats (-/-) have serotonergic disturbances with significant elevations of basal extracellular 5-HT levels. AIM To investigate the putative role of the SERT in male sexual behavior. METHODS After extensive sexual training, the effects of the 5-HT(1A/7) receptor agonist ± 8-OH-DPAT, the 5-HT(1A) receptor antagonist WAY100 635 and a combination of both on sexual behaviors of SERT(-/-) and SERT(+/-) knockout and wildtype (SERT(+/+) ) male Wistar rats were examined. MAIN OUTCOME MEASURES Male rat sexual behaviors of mounts, intromissions, and ejaculations. RESULTS SERT(-/-) had lower basal ejaculation frequencies than SERT(+/-) and SERT(+/+) animals. ± 8-OH-DPAT enhanced sexual performance in all three genotypes to the same extent. WAY100635 dose-dependently inhibited sexual behavior in all three genotypes with significant dose to genotype interactions. WAY100635 exerted the strongest effects in SERT(-/-) animals. The combination of a dose range of ± 8-OH-DPAT and a selected dose of WAY100635 revealed only partial antagonism by ± 8-OH-DPAT of the sexual inhibitory effects of WAY100635. CONCLUSIONS Absence of the serotonin transporter reduces basal ejaculatory performance in male rats. Pharmacological experiments suggest that separate pools of 5-HT(1A) receptors regulate different aspects of sexual performance in male rats. 5-HT(7) receptors may play a minor role in the partial recovery of sexual behavior after combination of ± 8-OH-DPAT and WAY100635. The SERT(-/-) rat may be a model for chronic SSRI treatment, delayed ejaculation, anorgasmia, and/or low libido.
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Affiliation(s)
- Johnny S W Chan
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences and Rudolf Magnus Institute of Neuroscience, Utrecht University, Sorbonnelaan, Utrecht, The Netherlands.
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da Silva E, Poltronieri S, Nascimento J, Zangrossi Jr. H, Viana M. Facilitation of 5-HT2A/2C-mediated neurotransmission in the ventromedial hypothalamic nucleus decreases anxiety in the elevated T-maze. Behav Brain Res 2011; 216:692-8. [DOI: 10.1016/j.bbr.2010.09.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 09/10/2010] [Accepted: 09/16/2010] [Indexed: 11/27/2022]
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Morphology and distribution of neurons expressing serotonin 5-HT1A receptors in the rat hypothalamus and the surrounding diencephalic and telencephalic areas. J Chem Neuroanat 2010; 39:235-41. [PMID: 20080175 DOI: 10.1016/j.jchemneu.2010.01.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 01/09/2010] [Accepted: 01/09/2010] [Indexed: 11/23/2022]
Abstract
Disorders of serotonergic neurotransmission are involved in disturbances of numerous hypothalamic functions including circadian rhythm, mood, neuroendocrine functions, sleep and feeding. Among the serotonin receptors currently recognized, 5-HT(1A) receptors have received considerable attention due to their importance in the etiology of mood disorders. While previous studies have shown the presence of 5-HT(1A) receptors in several regions of the rat brain, there is no detailed map of the cellular distribution of 5-HT(1A) receptors in the rat diencephalon. In order to characterize the distribution and morphology of the neurons containing 5-HT(1A) receptors in the diencephalon and the adjacent telencephalic areas, single label immunohistochemistry was utilized. Large, multipolar, 5-HT(1A)-immunoreactive (IR) neurons were mainly detected in the magnocellular preoptic nucleus and in the nucleus of diagonal band of Broca, while the supraoptic nucleus contained mainly fusiform neurons. Medium-sized 5-HT(1A)-IR neurons with triangular or round-shaped somata were widely distributed in the diencephalon, populating the zona incerta, lateral hypothalamic area, anterior hypothalamic nucleus, substantia innominata, dorsomedial and premamillary nuclei, paraventricular nucleus and bed nucleus of stria terminalis. The present study provides schematic mapping of 5-HT(1A)-IR neurons in the rat diencephalon. In addition, the morphology of the detected 5-HT(1A)-IR neural elements is also described. Since rat is a widely used laboratory animal in pharmacological models of altered serotoninergic neurotransmission, detailed mapping of 5-HT(1A)-IR structures is pivotal for the neurochemical characterization of the neurons containing 5-HT(1A) receptors.
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Grzegorzewska M, Maćkowiak M, Wedzony K, Hess G. 5-HT1A receptors mediate detrimental effects of cocaine on long-term potentiation and expression of polysialylated neural cell adhesion molecule protein in rat dentate gyrus. Neuroscience 2009; 166:122-31. [PMID: 20006974 DOI: 10.1016/j.neuroscience.2009.12.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Revised: 11/19/2009] [Accepted: 12/05/2009] [Indexed: 01/11/2023]
Abstract
The present study investigated the involvement of 5-HT(1A) receptors in the inhibitory effect of single administration of cocaine (COC, 15 mg/kg i.p.) on the induction of long-term potentiation (LTP) in slices of rat dentate gyrus (DG), prepared 30 min and 2 days after COC administration. These effects of COC were blocked by an antagonist of 5-HT(1A) receptors, WAY 100635 (0.4 mg/kg i.p.), which had been administered 20 min before COC. The detrimental effect of COC on LTP in slices prepared 30 min after COC administration could be prevented by blocking glucocorticoid receptors (GRs) using mifepristone (RU 38486, 10 mg/kg s.c. given 1 h before COC), similar as in slices obtained 2 days after COC as reported previously [Maćkowiak et al. (2008) Eur J Neurosci 27:2928-2937]. After a single administration of an agonist of 5-HT(1A) receptors, 8-OH-DPAT, (0.5 mg/kg i.p.), the level of LTP in slices prepared 2 days later was significantly decreased resembling the effect of COC. This effect of 8-OH-DPAT was antagonized by WAY 100635 (0.4 mg/kg i.p.), administered 20 min before 8-OH-DPAT and by RU 38486, given 1 h before 8-OH-DPAT. COC-induced inhibition of LTP could be blocked by the inhibitor of mitogen-activated protein kinase kinase 1/2 (MEK1/2), SL 327 (50 mg/kg i.p.), administered 1 h before COC, but not by the inhibitor of phosphatidylinositol 3-kinase (PI3-kinase), LY 294002 (80 mg/kg i.p.). COC-induced reduction in the number of polysialylated neural cell adhesion molecule (PSA-NCAM)-positive neurons in rat dentate gyrus could also be prevented by WAY 100635, given 20 min before COC. These data indicate that the indirect 5-HT(1A) receptor activation by a single COC administration and subsequent stimulation of extracellular signal-regulated kinases (ERK 1/2) signaling pathway result in a decrease of the potential for long-term increase in synaptic efficacy in rat DG lasting at least two but less than 7 days, most likely via activation of the hypothalamic-pituitary-adrenal (HPA) axis.
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Affiliation(s)
- M Grzegorzewska
- Department of Physiology, Institute of Pharmacology, Polish Academy of Sciences, Smetna 12, 31-343 Kraków, Poland
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Freitas RL, Ferreira CMDR, Urbina MAC, Mariño AU, Carvalho AD, Butera G, de Oliveira AM, Coimbra NC. 5-HT1A/1B, 5-HT6, and 5-HT7 serotonergic receptors recruitment in tonic-clonic seizure-induced antinociception: role of dorsal raphe nucleus. Exp Neurol 2009; 217:16-24. [PMID: 19416688 DOI: 10.1016/j.expneurol.2009.01.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Revised: 12/29/2008] [Accepted: 01/03/2009] [Indexed: 01/16/2023]
Abstract
Pharmacological studies have been focused on the involvement of different neural pathways in the organization of antinociception that follows tonic-clonic seizures, including 5-hydroxytryptamine (5-HT)-, norepinephrine-, acetylcholine- and endogenous opioid peptide-mediated mechanisms, giving rise to more in-depth comprehension of this interesting post-ictal antinociceptive phenomenon. The present work investigated the involvement of 5-HT(1A/1B), 5-HT(6), and 5-HT(7) serotonergic receptors through peripheral pretreatment with methiothepin at doses of 0.5, 1.0, 2.0 and 3.0 mg/kg in the organization of the post-ictal antinociception elicited by pharmacologically (with pentylenetetrazole at 64 mg/kg)-induced tonic-clonic seizures. Methiothepin at 1.0 mg/kg blocked the post-ictal antinociception recorded after the end of seizures, whereas doses of 2.0 and 3.0 mg/kg potentiated the post-ictal antinociception. The nociceptive thresholds were kept higher than those of the control group. However, when the same 5-hydroxytryptamine receptors antagonist was microinjected (at 1.0, 3.0 and 5.0 microg/0.2 microL) in the dorsal raphe nucleus, a mesencephalic structure rich in serotonergic neurons and 5-HT receptors, the post-ictal hypo-analgesia was consistently antagonized. The present findings suggest a dual effect of methiothepin, characterized by a disinhibitory effect on the post-ictal antinociception when peripherally administered (possibly due to an antagonism of pre-synaptic 5-HT(1A) serotonergic autoreceptors in the pain endogenous inhibitory system) and an inhibitory effect (possibly due to a DRN post-synaptic 5-HT(1B), 5-HT(6), and 5-HT(7) serotonergic receptors blockade) when centrally administered. The present data also suggest that serotonin-mediated mechanisms of the dorsal raphe nucleus exert a key-role in the modulation of the post-ictal antinociception.
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Affiliation(s)
- Renato Leonardo Freitas
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo, Laboratório de Neuroanatomia & Neuropsicobiologia, Ribeirão Preto, SP, Brazil
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Johnson DA, Ingram CD, Grant EJ, Craighead M, Gartside SE. Glucocorticoid receptor antagonism augments fluoxetine-induced downregulation of the 5-HT transporter. Neuropsychopharmacology 2009; 34:399-409. [PMID: 18496518 DOI: 10.1038/npp.2008.70] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The effects of combined treatment with a glucocorticoid receptor (GR) antagonist, Org 34850, and a selective serotonin reuptake inhibitor (SSRI), fluoxetine, were investigated on pre- and postsynaptic aspects of 5-HT neurotransmission. Rats were treated for 14 days with Org 34850 (15 mg per kg per day subcutaneously), fluoxetine (10 mg per kg per day intraperitoneally), or a combination of both drugs. [(3)H]-citalopram binding (an index of 5-HT transporter (5-HTT) expression) was only slightly affected by Org 34850 alone: decreased in cortex and midbrain and increased in hippocampus. In contrast, chronic fluoxetine markedly decreased 5-HTT levels in all regions. Importantly, this decrease was significantly enhanced by combined Org 34850/fluoxetine treatment. There were no changes in the expression of 5-HTT mRNA, suggesting these effects were not due to changes in gene transcription. Expression of tryptophan hydroxylase mRNA and both 5-HT(1A) autoreceptor mRNA and protein (assessed using [(3)H]-8-OH-DPAT binding) were unchanged by any treatment. The expression of postsynaptic 5-HT(1A) receptor protein in the forebrain was unaltered by fluoxetine, Org 34850 or the combined Org 34850/fluoxetine treatment. This downregulation of 5-HTT by fluoxetine and its enhancement by Org 34850 can explain our recent observation that GR antagonists augment the SSRI-induced increase in extracellular 5-HT. In addition, these data suggest that the augmentation of forebrain 5-HT does not result in downregulation of forebrain 5-HT(1A) receptor expression. Given the importance of 5-HT(1A) receptor-mediated transmission in the forebrain to the antidepressant response, these data indicate that co-administration of GR antagonists may be effective in augmenting the antidepressant response to SSRI treatment.
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Affiliation(s)
- Daniel Anthony Johnson
- Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, UK
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Günther L, Liebscher S, Jähkel M, Oehler J. Effects of chronic citalopram treatment on 5-HT1A and 5-HT2A receptors in group- and isolation-housed mice. Eur J Pharmacol 2008; 593:49-61. [PMID: 18657534 DOI: 10.1016/j.ejphar.2008.07.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Revised: 06/27/2008] [Accepted: 07/09/2008] [Indexed: 01/01/2023]
Abstract
Selective serotonin reuptake inhibitors (SSRI) are characterized by high clinical effectiveness and good tolerability. A 2-3 week delay in the onset of effects is caused by adaptive mechanisms, probably at the serotonergic (5-HT) receptor level. To analyze this in detail, we measured 5-HT(1A) and 5-HT(2A) receptor bindings in vitro after 3 weeks of citalopram treatment (20 mg/kg i.p. daily) in group-housed as well as isolation-housed mice, reflecting neurobiological aspects seen in psychiatric patients. Isolation housing increased somatodendritic (+52%) and postsynaptic (+30-95%) 5-HT(1A) as well as postsynaptic 5-HT(2A) receptor binding (+25-34%), which confirms previous findings. Chronic citalopram treatment did not induce alterations in raphe 5-HT(1A) autoreceptor binding, independent of housing conditions. Housing-dependent citalopram effects on postsynaptic 5-HT(1A) receptor binding were found with increases in group- (+11-42%) but decreases in isolation-housed (-11 to 35%) mice. Forebrain 5-HT(2A) receptor binding decreased between 11 and 38% after chronic citalopram administration, independent of housing conditions. Citalopram's long-term action comprises alterations at the postsynaptic 5-HT(1A) and 5-HT(2A) receptor binding levels. Housing conditions interact with citalopram effects, especially on 5-HT(1A) receptor binding, and should be more strongly considered in pharmacological studies. In general, SSRI-induced alterations were more pronounced and affected more brain regions in isolates, supporting the concept of a higher responsiveness in "stressed" animals. Isolation-induced receptor binding changes were partly normalized by chronic citalopram treatment, suggesting the isolation housing model for further analyses of SSRI effects, especially at the behavioral level.
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Affiliation(s)
- Lydia Günther
- AG Neurobiologie, Klinik für Psychiatrie, Universitätsklinikum der TU Dresden, Fetscherstrasse 74, Dresden, Germany.
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16
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Crane JW, Shimizu K, Carrasco GA, Garcia F, Jia C, Sullivan NR, D'Souza DN, Zhang Y, Van de Kar LD, Muma NA, Battaglia G. 5-HT1A receptors mediate (+)8-OH-DPAT-stimulation of extracellular signal-regulated kinase (MAP kinase) in vivo in rat hypothalamus: time dependence and regional differences. Brain Res 2007; 1183:51-9. [PMID: 17976547 DOI: 10.1016/j.brainres.2007.07.101] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Revised: 07/13/2007] [Accepted: 07/19/2007] [Indexed: 11/28/2022]
Abstract
Brain serotonin 1A (5-HT1A) receptors play an important role in mood disorders and can modulate various intracellular signaling mechanisms. We previously reported that systemic administration of either full or partial 5-HT1A agonists increases neuroendocrine responses and that tandospirone, an azapirone partial agonist, can activate (phosphorylate) extracellular signal-regulated kinase (ERK) in the hypothalamic paraventricular nucleus (PVN). In contrast, decreased levels of phosphoERK (pERK) have been reported in hippocampus following in vivo administration of either azapirone or aminotetralin 5-HT1A agonists, such as 8-hydroxy-2-dipropylaminotetralin (8-OH-DPAT). The present study investigated the time-dependent activation of MAP kinase in hypothalamus by (+)8-OH-DPAT to determine the regional differences and receptor specificity of the changes in pERK. Adult male rats received a systemic injection of (+)8-OH-DPAT (200 microg/kg, s.c.). The time-dependent changes in ERK activation were examined in hypothalamic nuclei as well as other brain regions associated with modulation of mood. (+)8-OH-DPAT produced a rapid increase (at 5 min) and transient return (at 15 min) of pERK levels in PVN and medial basal hypothalamus. In contrast, pERK levels in hippocampus were reduced at both 5 and 15 min after (+)8-OH-DPAT. Pretreatment with the 5-HT1A receptor-specific antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide (WAY100635) completely blocked the (+)8-OH-DPAT-mediated changes in pERK levels in PVN, medial basal hypothalamus, and hippocampus. No significant (+)8-OH-DPAT-induced changes in pERK were observed in dorsal raphe or amygdala. In conclusion, these results demonstrate that 8-OH-DPAT activation of MAP kinase signaling in vivo is a transient and region-specific phenomenon and in rat hypothalamus and hippocampus is mediated by 5-HT1A receptors.
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Affiliation(s)
- James W Crane
- Department of Pharmacology, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Avenue, Maywood, IL 60153, USA
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17
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Veening JG, Coolen LM, de Jong TR, Joosten HW, de Boer SF, Koolhaas JM, Olivier B. Do similar neural systems subserve aggressive and sexual behaviour in male rats? Insights from c-Fos and pharmacological studies. Eur J Pharmacol 2005; 526:226-39. [PMID: 16263109 DOI: 10.1016/j.ejphar.2005.09.041] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2005] [Accepted: 09/23/2005] [Indexed: 11/15/2022]
Abstract
It is a common belief that male aggressive and sexual behaviour share many of the underlying neurobiological, neurological, pharmacological and neuroendocrine mechanisms. Therefore, we studied brain activation patterns in male rat after performance of aggressive and sexual behaviour and compared serotonergic pharmacology in the same paradigms to delineate possible similarities and differences. Patterns of Fos-immunoreactivity induced by aggressive and sexual encounters of Wild-type male Brown Norway rats were studied to localise the commonly activated (functionally shared) parts of the circuitry, and the specific (functionally different) parts of the neuronal circuitry. Some brain areas (caudal medial preoptic area and medial amygdala) were commonly activated, but other areas (e.g. posterodorsal parts of the medial amygdala, rostral preoptic and premammillary hypothalamus) showed remarkably specific differences in neural activation. 5-HT(1A) receptor agonists inhibit aggressive, but stimulate male sexual behaviour, whereas 5-HT(1B) receptor agonists inhibit both types of behaviour. Selective serotonin reuptake inhibitors share comparable inhibitory effects in aggression and sexual behaviour, although only at relatively high doses. We propose that separate hard-wired neural systems exist in the brain for aggressive and sexual behaviours, modulated via hierarchically 'higher-level' brain areas that are involved in the integration (gating) of the behavioural outcome of an organism.
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Affiliation(s)
- Jan G Veening
- Department of Anatomy, University Medical Center St Radboud, Nijmegen, The Netherlands.
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18
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Chen Z, Tetzlaff J, Sripathirathan K, Carrasco GA, Shankaran M, Van De Kar LD, Muma NA, Battaglia G. Paroxetine is effective in desensitizing 5-HT1A receptor function in adult offspring exposed prenatally to cocaine. Psychopharmacology (Berl) 2005; 180:316-26. [PMID: 15864558 DOI: 10.1007/s00213-005-2249-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Accepted: 12/11/2004] [Indexed: 10/25/2022]
Abstract
RATIONALE Desensitization of postsynaptic 5-HT(1A) receptors may be responsible for the therapeutic effectiveness of serotonin selective uptake inhibitors (SSRIs). As prenatal cocaine exposure produces long-term deficits in 5-HT neurons in offspring, it may alter the ability of postsynaptic 5-HT(1A) receptors to be desensitized by chronic paroxetine. OBJECTIVES The aim of the study is to determine (1) prenatal cocaine-induced changes in 5-HT(1A) receptor function and (2) the effectiveness of chronic treatment with paroxetine to produce 5-HT(1A) receptor desensitization in adult offspring exposed to cocaine in utero. METHODS Pregnant rats received saline or (-)cocaine (15 mg/kg, s.c.) twice daily from gestational days 13 through 20. Adult male offspring from each of prenatal groups were treated with saline or paroxetine (10 mg/kg/day; i.p.) for 14 days. Eighteen hours post-treatment, rats were challenged with saline or the 5-HT(1A) receptor agonist (+)8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 0.04 or 0.2 mg/kg, s.c.). Plasma oxytocin, adrenocorticotropic hormone (ACTH), corticosterone, renin and prolactin were determined. RESULTS Prenatal cocaine exposure did not alter 5-HT(1A) receptor-mediated neuroendocrine responses. Paroxetine treatment desensitized 5-HT(1A) receptor-mediated increases in oxytocin, ACTH and corticosterone to a comparable extent in all offspring and reduced the E(max) for ACTH only in prenatal cocaine-exposed offspring. Cortical [(3)H]-8-OH-DPAT- or [(3)H]-WAY100635-labeled 5-HT(1A) receptors were unaltered by prenatal cocaine or subsequent paroxetine treatment. CONCLUSIONS Postsynaptic 5-HT(1A) receptor function is unaltered by prenatal cocaine exposure and paroxetine can effectively desensitize 5-HT(1A) receptor function in adult cocaine-exposed offspring. These data suggest that paroxetine may be clinically effective in treating mood disorders in adults exposed in utero to cocaine.
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Affiliation(s)
- Zhuo Chen
- Department of Pharmacology and Center for Serotonin Disorders Research, Stritch School of Medicine, Loyola University of Chicago, 2160 South First Avenue, Maywood, IL 60153, USA
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19
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Carrasco GA, Barker SA, Zhang Y, Damjanoska KJ, Sullivan NR, Garcia F, D'souza DN, Muma NA, van De Kar LD. Estrogen treatment increases the levels of regulator of G protein signaling-Z1 in the hypothalamic paraventricular nucleus: possible role in desensitization of 5-hydroxytryptamine1A receptors. Neuroscience 2004; 127:261-7. [PMID: 15262317 DOI: 10.1016/j.neuroscience.2004.05.031] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2004] [Revised: 05/16/2004] [Accepted: 05/24/2004] [Indexed: 11/22/2022]
Abstract
Desensitization of post-synaptic serotonin1A (5-HT1A) receptors may underlie the clinical improvement of neuropsychiatric disorders. In the hypothalamic paraventricular nucleus, Galphaz proteins mediate the 5-HT1A receptor-stimulated increases in hormone release. Regulator of G protein signaling-Z1 (RGSZ1) is a GTPase-activating protein selective for Galphaz proteins. RGSZ1 regulates the duration of interaction between Galphaz proteins and effector systems. The present investigation determined the levels of RGSZ1 in the hypothalamic paraventricular nucleus of rats subjected to four different treatment protocols that produce desensitization of 5-HT1A receptors. These protocols include: daily administration of beta estradiol 3-benzoate (estradiol) for 2 days; daily administration of fluoxetine for 3 and 14 days; daily administration of cocaine for 7 or 14 days; and acute administration of (+/-)-1-(2,5 dimethoxy-4-iodophenyl)-2-amino-propane HCl (DOI; a 5-HT2A/2C receptor agonist). Estradiol treatment was the only protocol that increased the levels of RGSZ1 protein in the hypothalamic paraventricular nucleus in a dose-dependent manner (46%-132% over control). Interestingly, previous experiments indicate that only estradiol produces a decreased Emax of 5-HT1A receptor-stimulation of hormone release, whereas fluoxetine, cocaine and DOI produce a shift to the right (increased ED50). Thus, the desensitization of 5-HT1A receptors by estradiol might be attributable to increased levels of RGSZ1 protein. These findings may provide insight into the adaptation of 5-HT1A receptor signaling during pharmacotherapies of mood disorders in women and the well-established gender differences in the vulnerability to depression.
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Affiliation(s)
- G A Carrasco
- Center for Serotonin Disorder Research and Department of Pharmacology Loyola University of Chicago, Stritch School of Medicine, 2160 South First Avenue, Maywood, IL 60153, USA
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20
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Zhang Y, Gray TS, D'Souza DN, Carrasco GA, Damjanoska KJ, Dudas B, Garcia F, Zainelli GM, Sullivan Hanley NR, Battaglia G, Muma NA, Van de Kar LD. Desensitization of 5-HT1A receptors by 5-HT2A receptors in neuroendocrine neurons in vivo. J Pharmacol Exp Ther 2004; 310:59-66. [PMID: 15064330 DOI: 10.1124/jpet.103.062224] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
An imbalance between serotonin-2A (5-HT2A) and 5-HT1A receptors may underlie several mood disorders. The present studies determined whether 5-HT2A receptors interact with 5-HT1A receptors in the rat hypothalamic paraventricular nucleus (PVN). The sensitivity of the hypothalamic 5-HT1A receptors was measured as oxytocin and adrenocorticotropic hormone (ACTH) responses to the 5-HT1A receptor agonist (+)-8-hydroxy-2-(di-n-propylamino) tetralin hydrobromide [(+)8-OH-DPAT] (40 microg/kg s.c.). The 5-HT(2A/2C) receptor agonist (-)DOI [(-)-1-(2,5-dimethoxy-4-iodophenyl)2-aminopropane HCl] (1 mg/kg s.c.) injected 2 h prior to (+)8-OH-DPAT significantly reduced the oxytocin and ACTH responses to (+)8-OH-DPAT, producing a heterologous desensitization of the 5-HT1A receptors. Microinjection of the 5-HT2A receptor antagonist MDL100,907 [(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidinemethanol; 0, 10, or 20 nmol, 15 min prior to (-)DOI] into the PVN dose-dependently prevented the desensitization of 5-HT1A receptors induced by the 5-HT2A receptor agonist (-)DOI. Double-label immunocytochemistry revealed a high degree of colocalization of 5-HT1A and 5-HT2A receptors in the oxytocin and corticotropin-releasing factor neurons of the PVN. Thus, activation of 5-HT2A receptors in the PVN may directly induce a heterologous desensitization of 5-HT1A receptors within individual neuroendocrine cells. These findings may provide insight into the long-term adaptation of 5-HT1A receptor signaling after changes in function of 5-HT2A receptors; for example, during pharmacotherapy of mood disorders.
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Affiliation(s)
- Yahong Zhang
- Center for Serotonin Disorders Research and Department of Pharmacology, Loyola University of Chicago, Stritch School of Medicine, Maywood, Illinois 60153, USA
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21
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Hanley NR, Van de Kar LD. Serotonin and the neuroendocrine regulation of the hypothalamic--pituitary-adrenal axis in health and disease. VITAMINS AND HORMONES 2003; 66:189-255. [PMID: 12852256 DOI: 10.1016/s0083-6729(03)01006-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Serotonin (5-hydroxytryptamine, 5-HT)-containing neurons in the midbrain directly innervate corticotropin-releasing hormone (CRH)-containing cells located in paraventricular nucleus of the hypothalamus. Serotonergic inputs into the paraventricular nucleus mediate the release of CRH, leading to the release of adrenocorticotropin, which triggers glucocorticoid secretion from the adrenal cortex. 5-HT1A and 5-HT2A receptors are the main receptors mediating the serotonergic stimulation of the hypothalamic-pituitary-adrenal axis. In turn, both CRH and glucocorticoids have multiple and complex effects on the serotonergic neurons. Therefore, these two systems are interwoven and communicate closely. The intimate relationship between serotonin and the hypothalamic-pituitary-adrenal axis is of great importance in normal physiology such as circadian rhythm and stress, as well as pathophysiological disorders such as depression, anxiety, eating disorders, and chronic fatigue.
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Affiliation(s)
- N R Hanley
- Department of Pharmacology, Center for Serotonin Disorders Research, Loyola University of Chicago, Stritch School of Medicine, Maywood, Illinois 60153, USA
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22
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Dremencov E, Gur E, Lerer B, Newman ME. Effects of chronic antidepressants and electroconvulsive shock on serotonergic neurotransmission in the rat hippocampus. Prog Neuropsychopharmacol Biol Psychiatry 2003; 27:729-39. [PMID: 12921903 DOI: 10.1016/s0278-5846(03)00123-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The hippocampus may play a critical role in the pathophysiology and treatment of depression. There are two main lines of evidence for this: firstly, many of its functions correspond to those altered in depression, and secondly, many hippocampal functions are regulated by the serotonergic (5-HT) system, which is a common target of antidepressant treatments. Chronic effects of antidepressants and electroconvulsive shock (ECS) have been studied by various methods using electrophysiology, in vivo microdialysis or ex vivo neurochemical measurements. The aim of the current review is to point out possible correlations between these studies based on different methods and to suggest neurochemical mechanisms that result in the observed changes in hippocampal physiology and neurogenesis. These changes in hippocampal neurochemistry are reviewed and compared with the abnormalities associated with stress, corticosterone or depression.
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Affiliation(s)
- Eliyahu Dremencov
- Life Sciences Faculty, Bar-Ilan University, Ramat-Gan 52900, Israel.
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23
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Hensler JG. Regulation of 5-HT1A receptor function in brain following agonist or antidepressant administration. Life Sci 2003; 72:1665-82. [PMID: 12559389 DOI: 10.1016/s0024-3205(02)02482-7] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Adaptive changes in the serotonergic system are generally believed to underlie the therapeutic effectiveness of the azapirone anxiolytics and a variety of antidepressant drugs. The serotonin-1A (5-HT(1A)) receptor has been implicated in affective disorders. Thus, studies of the regulation of 5-HT(1A) receptor function may have important implications for our understanding the role of this receptor in the mechanism of action of these therapeutic agents. This review focuses on the regulation of central 5-HT(1A) receptor function following administration of 5-HT(1A) receptor agonists or antidepressant drugs expected to increase the synaptic concentration of the neurotransmitter 5-HT. The majority of evidence supports regional differences in the regulation of central 5-HT(1A) receptor function following repeated agonist or antidepressant administration, which may be due to differences in processes involved in desensitization of the receptor at the cellular level. Region-specific differences in the regulation of 5-HT(1A) receptor function may be based on compensatory changes distal to the receptor, such as regulatory changes at the level of effector (e.g. adenylyl cyclase or ion channel), or at the level of the G protein such as changes in G protein expression, or phosphorylation of the G protein. It may be that the increase in serotonin neurotransmission, due to somatodendritic autoreceptor desensitization following agonist or antidepressant treatment, to normo-sensitive 5-HT(1A) receptors in certain brain regions (e.g. hippocampus or cortex) and to sub-sensitive 5-HT(1A) receptors in other brain regions (e.g. amygdala or hypothalamus) underlies the therapeutic efficacy of these drugs.
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Affiliation(s)
- Julie G Hensler
- Department of Pharmacology, University of Texas Health Science Center-San Antonio, 7703 Floyd Curl Drive, MC 7764, San Antonio, TX 78229-3900, USA.
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24
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Naudon L, El Yacoubi M, Vaugeois JM, Leroux-Nicollet I, Costentin J. A chronic treatment with fluoxetine decreases 5-HT(1A) receptors labeling in mice selected as a genetic model of helplessness. Brain Res 2002; 936:68-75. [PMID: 11988231 DOI: 10.1016/s0006-8993(02)02548-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Two lines of mice were bred for their opposite helpless behavior in the tail suspension test, i.e., helpless (HL) mice and non helpless (NHL) mice. The 5-HT(1A) receptor labeling was quantified by means of autoradiography with (3)H-8-OH-DPAT on brain sections from mice of these two lines. We observed a significantly higher level of (3)H-8-OH-DPAT binding sites density in HL mice comparatively to NHL mice, in the medial prefrontal, cingulate, motor and sensorial cortices, in several regions of the limbic system, such as CA3 field of hippocampus, dentate gyrus, medial and baso-medial amygdala, and in dorsal and median raphe nuclei. A chronic 21-day treatment with the antidepressant fluoxetine (10 mg/kg, i.p. daily) attenuated significantly the spontaneous helplessness in HL mice but did not alter the behavior of NHL mice. In the brain of HL mice chronically injected with fluoxetine, the elevated (3)H-8-OH-DPAT binding sites density was no longer observed after treatment in several regions, among which the raphe nuclei. Conversely, the antidepressant treatment did not modify the (3)H-8-OH-DPAT binding sites density in NHL mice. The variation of 5-HT(1A) receptors binding density in the HL mice in response to a chronic fluoxetine treatment parallels the attenuation of the spontaneous helplessness observed in the tail suspension test, and may underlie this behavior.
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MESH Headings
- 8-Hydroxy-2-(di-n-propylamino)tetralin
- Animals
- Binding, Competitive/drug effects
- Binding, Competitive/physiology
- Brain/cytology
- Brain/drug effects
- Brain/metabolism
- Depression/drug therapy
- Depression/genetics
- Depression/metabolism
- Disease Models, Animal
- Down-Regulation/drug effects
- Down-Regulation/genetics
- Drug Administration Schedule
- Female
- Fluoxetine/pharmacology
- Helplessness, Learned
- Mice
- Mice, Inbred Strains
- Motor Activity/drug effects
- Motor Activity/physiology
- Mutation/drug effects
- Mutation/physiology
- Neurons/drug effects
- Neurons/metabolism
- Radioligand Assay
- Receptors, Serotonin/drug effects
- Receptors, Serotonin/genetics
- Receptors, Serotonin/metabolism
- Receptors, Serotonin, 5-HT1
- Serotonin/metabolism
- Serotonin Receptor Agonists
- Selective Serotonin Reuptake Inhibitors/pharmacology
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
- Tritium
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Affiliation(s)
- Laurent Naudon
- Unité de Neuropsychopharmacologie Expérimentale, UMR 6036 CNRS-IFRMP No. 23, Faculté de Médecine et de Pharmacie de Rouen, 22 Boulevard Gambetta, 76183 Rouen, Cedex, France.
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25
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Pejchal T, Foley MA, Kosofsky BE, Waeber C. Chronic fluoxetine treatment selectively uncouples raphe 5-HT(1A) receptors as measured by [(35)S]-GTP gamma S autoradiography. Br J Pharmacol 2002; 135:1115-22. [PMID: 11877317 PMCID: PMC1573219 DOI: 10.1038/sj.bjp.0704555] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
1. Selective Serotonin Reuptake Inhibitors (SSRIs) are thought to have a delay in therapeutic efficacy because of the need to overcome the inhibitory influence of raphe 5-HT(1A) autoreceptors. Prolonged SSRI administration has been reported to desensitize these autoreceptors. We have used [(35)S]-GTP gamma S autoradiography to determine whether this desensitization occurs at the level of receptor/G protein coupling. 2. Male mice were injected intraperitoneally once a day with saline or 20 mg kg(-1) fluoxetine for either 2 days or 14 days. 5-HT(1A) receptor binding and coupling to G proteins were assessed using [(3)H]-8-OH-DPAT and [(35)S]-GTP gamma S autoradiography, respectively. 3. The 5-HT receptor agonist 5-carboxamidotryptamine (5-CT) stimulated [(35)S]-GTP gamma S binding in the substantia nigra, as well as in hippocampus and dorsal raphe nucleus. The 5-HT(1A) receptor antagonist p-MPPF (4-fluoro-N-(2-[4-(2-methoxyphenyl)1-piperazinyl]ethyl)-N-(2-pyridinyl)benzamide) blocked this effect in the latter regions, whereas the 5-HT(1B/D) antagonist GR-127,935 (2'-methyl-4'-(5-methyl-[1,2,4]oxadiazol-3-yl)-biphenyl-4-carboxylic acid [4-methoxy-3-(4-methyl-piperazin-l-yl)-phenyl]-amide) only decreased labelling in substantia nigra. 4. Fourteen-day fluoxetine treatment decreased 5-CT-stimulated [(35)S]-GTP gamma S binding in dorsal raphe (saline: 112 +/- 12% stimulation; fluoxetine: 66 +/- 13%), but not in substantia nigra (99 +/- 14% vs 103 +/- 7%) or hippocampus (157 +/- 3% vs 148 +/- 18%). Two-day fluoxetine treatment did not alter 5-CT-stimulated [(35)S]-GTP gamma S binding in any of the brain areas investigated. 5. Decreased [(35)S]-GTP gamma S binding was not due to receptor down-regulation, since the density of raphe [(3)H]-8-OH-DPAT binding sites was unaffected by fluoxetine treatment. 6. These results suggest that the desensitization of presynaptic 5-HT(1A) receptor function occurs at the level of receptor-G protein interaction on dorsal raphe neurons, and may underlie the therapeutic efficacy of long-term SSRI treatment.
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Affiliation(s)
- Tina Pejchal
- Massachusetts General Hospital, Harvard Medical School, Neuroscience Center, Room 6403, Charlestown, MA 02129, U.S.A
| | - Melissa A Foley
- Massachusetts General Hospital, Harvard Medical School, Neuroscience Center, Room 6403, Charlestown, MA 02129, U.S.A
| | - Barry E Kosofsky
- Massachusetts General Hospital, Harvard Medical School, Neuroscience Center, Room 6403, Charlestown, MA 02129, U.S.A
| | - Christian Waeber
- Massachusetts General Hospital, Harvard Medical School, Neuroscience Center, Room 6403, Charlestown, MA 02129, U.S.A
- Author for correspondence:
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26
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Martín-Ruiz R, Ugedo L. Electrophysiological evidence for postsynaptic 5-HT(1A) receptor control of dorsal raphe 5-HT neurones. Neuropharmacology 2001; 41:72-8. [PMID: 11445187 DOI: 10.1016/s0028-3908(01)00050-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Postsynaptic 5-hydroxytryptamine(1A) (5-HT(1A)) receptors have been proposed to participate in the control of dorsal raphe 5-HT neurone activity. To further investigate this hypothesis we performed single-unit extracellular recordings in anaesthetized rats. Pertussis toxin (2 microg/4 microl/day; 2 days, 24-72 h before the experiment) was applied close to the dorsal raphe nucleus to uncouple somatodendritic 5-HT(1A) autoreceptors from their effector system. After this treatment the spontaneous firing rate was higher (approximately +60% P<0.005) than in the vehicle-pretreated group. In addition, intravenous administration of 8-hydroxy-2-(di-n-propylamino)tetralin HBr (8-OH-DPAT) inhibited 5 out of 11 cells of the pertussis toxin-pretreated group (ED(50)=1.65+/-0.94 microg/kg), whereas in the vehicle-pretreated group, all tested cells were inhibited (ED(50)=1.87+/-0.39 microg/kg). Local administration of 8-OH-DPAT did not affect cells (n=12) in pertussis toxin-pretreated rats, even at doses much higher than those needed to completely inhibit 5-HT cells in vehicle-pretreated rats (ED(50)=3.34+/-0.62 fmol). These results confirm the involvement of distal postsynaptic 5-HT(1A) receptors in the control of 5-HT neurone activity in the dorsal raphe nucleus. However, this control does not appear to be exerted on all 5-HT neurones, but rather on a subpopulation of them.
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Affiliation(s)
- R Martín-Ruiz
- Department of Pharmacology, Faculty of Medicine, University of the Basque Country, 48940 Leioa, Vizcaya, Spain
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27
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Srinivas BN, Subhash MN, Vinod KY. Cortical 5-HT(1A) receptor downregulation by antidepressants in rat brain. Neurochem Int 2001; 38:573-9. [PMID: 11290382 DOI: 10.1016/s0197-0186(00)00123-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Total 5-HT binding sites and 5-HT(1A) receptor density was measured in brain regions of rats treated with imipramine (5 mg/kg body wt), desipramine (10 mg/kg body wt) and clomipramine (10 mg/kg body wt), for 40 days, using [3H]5-HT and [3H]8-OH-DPAT, respectively. It was observed that chronic exposure to tricyclic antidepressants (TCAs) results in significant downregulation of total [3H]5-HT binding sites in cortex (42-76%) and hippocampus (35-67%). The 5-HT(1A) receptor density was, however, decreased significantly (32-60%) only in cortex with all the three drugs. Interestingly, in hippocampus imipramine treatment increased the 5-HT(1A) receptor density (14%). The affinity of [3H]8-OH-DPAT was increased only with imipramine treatment both in cortex and hippocampus. The affinity of [3H]5-HT to 5-HT binding sites in cortex was increased with imipramine treatment and decreased with desipramine and clomipramine treatment. 5-HT sensitive adenylyl cyclase (AC) activity was significantly increased in cortex with imipramine (72%) and clomipramine (17%) treatment, whereas in hippocampus only imipramine treatment significantly increased AC activity (50%). In conclusion, chronic treatment with TCAs results in downregulation of cortical 5-HT(1A) receptors along with concomitant increase in 5-HT stimulated AC activity suggesting the involvement of cortical 5-HT(1A) receptors in the mechanism of action of TCAs.
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Affiliation(s)
- B N Srinivas
- Department of Neurochemistry, National Institute of Mental Health and Neurosciences, P.B. No. 2900, Bangalore 560 029, India
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Reduction in the density and expression, but not G-protein coupling, of serotonin receptors (5-HT1A) in 5-HT transporter knock-out mice: gender and brain region differences. J Neurosci 2001. [PMID: 11050108 DOI: 10.1523/jneurosci.20-21-07888.2000] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The aim of the present study was to investigate the mechanisms underlying the desensitization of 5-HT(1A) receptors in the dorsal raphe and hypothalamus of serotonin (5-HT) transporter knock-out mice (5-HTT -/-). The density of 5-HT(1A) receptors in the dorsal raphe was reduced in both male and female 5-HTT -/- mice. This reduction was more extensive in female than in male 5-HTT -/- mice. 8-OH-DPAT-induced hypothermia was absent in female 5-HTT -/- and markedly attenuated in 5-HTT +/- mice. The density of 5-HT(1A) receptors also was decreased significantly in several nuclei of the hypothalamus, amygdala, and septum of female 5-HTT -/- mice. 5-HT(1A) receptor mRNA was reduced significantly in the dorsal raphe region, but not in the hypothalamus or hippocampus, of female 5-HTT +/- and 5-HTT -/- mice. G-protein coupling to 5-HT(1A) receptors and G-protein levels in most brain regions were not reduced significantly, except that G(o) and G(i1) proteins were reduced modestly in the midbrain of 5-HTT -/- mice. These data suggest that the desensitization of 5-HT(1A) receptors in 5-HTT -/- mice may be attributable to a reduction in the density of 5-HT(1A) receptors. This reduction is brain region-specific and more extensive in the female mice. The reduction in the density of 5-HT(1A) receptors may be mediated partly by reduction in the gene expression of 5-HT(1A) receptors in the dorsal raphe, but also by other mechanisms in the hypothalamus of 5-HTT -/- female mice. Finally, alterations in G-protein coupling to 5-HT(1A) receptors are unlikely to be involved in the desensitization of 5-HT(1A) receptors in 5-HTT -/- mice.
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Raap DK, DonCarlos L, Garcia F, Muma NA, Wolf WA, Battaglia G, Van de Kar LD. Estrogen desensitizes 5-HT(1A) receptors and reduces levels of G(z), G(i1) and G(i3) proteins in the hypothalamus. Neuropharmacology 2000; 39:1823-32. [PMID: 10884563 DOI: 10.1016/s0028-3908(99)00264-6] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study investigated whether estrogen would desensitize hypothalamic serotonin(1A) (5-HT(1A)) receptors by examining the neuroendocrine response to 8-OH-DPAT, a 5-HT(1A) agonist. Rats were ovariectomized, allowed to recover for 5 days, then given 2 daily injections of estradiol benzoate or vehicle (10 microg/day, s.c.). Twenty-four hours after the second injection, rats were challenged with a sub-maximal dose of 8-OH-DPAT (50 microg/kg, sc) or saline 15 min prior to sacrifice. 8-OH-DPAT produced a significant increase in plasma oxytocin, ACTH and corticosterone levels in ovariectomized rats. While estrogen treatment for 2 days did not alter basal hormone levels, it did significantly reduce the magnitude of oxytocin, ACTH and corticosterone responses to 8-OH-DPAT. The reduction in hormone responses was accompanied by a significant reduction in hypothalamic levels of G(z), G(i1) and G(i3) proteins (by 50%, 30% and 50%, respectively). These findings suggest that a reduction in these G proteins may contribute to the mechanisms underlying estrogen-induced desensitization of 5-HT(1A) receptors. The desensitization of 5-HT(1A) receptors has been suggested to underlie the therapeutic effects of antidepressant 5-HT uptake inhibitors (SSRIs). Thus, the present results suggest that estrogen or estrogen-like substances in combination with SSRIs may prove effective in developing novel therapeutic strategies for neuropsychiatric disorders in women.
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Affiliation(s)
- D K Raap
- Department of Pharmacology, Stritch School of Medicine, Loyola University Chicago, 2160 S. First Avenue, IL 60153, Maywood, USA
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Abstract
Using in situ hybridization and immunoblot analysis, the present studies identified G(z) mRNA and G(z)-protein in the hypothalamic paraventricular nucleus. The role of G(z)-proteins in hypothalamic 5-HT(1A) receptor signaling was examined in vivo. Activation of 5-HT(1A) receptors increases the secretion of oxytocin and ACTH, but not prolactin. Intracerebroventricular infusion (3-4 d) of G(z) antisense oligodeoxynucleotides, with different sequences and different phosphorothioate modification patterns, reduced the levels of G(z)-protein in the hypothalamic paraventricular nucleus, whereas missense oligodeoxynucleotides had no effect. Neither antisense nor missense oligodeoxynucleotide treatment altered basal plasma levels of ACTH, oxytocin, or prolactin, when compared with untreated controls. An antisense-induced decrease in hypothalamic G(z)-protein levels was paralleled by a significant decrease in the oxytocin and ACTH responses to the 5-HT(1A) agonist 8-hydroxy-dipropylamino-tetralin (8-OH-DPAT). In contrast, the prolactin response to 8-OH-DPAT (which cannot be blocked by 5-HT(1A) antagonists) was not inhibited by G(z) antisense oligodeoxynucleotides. G(z)-proteins are the only members of the G(i)/G(o)-protein family that are not inactivated by pertussis toxin. In a control experiment, pertussis toxin treatment (1 microgram/5 microliter, i.c.v.; 48 hr before the 8-OH-DPAT challenge) did not inhibit the ACTH response, potentiated the oxytocin response, and eliminated the prolactin response to 8-OH-DPAT. Thus, pertussis toxin-sensitive G(i)/G(o)-proteins do not mediate the 5-HT(1A) receptor-mediated increase in ACTH and oxytocin secretion. Combined, these studies provide the first in vivo evidence for a key role of G(z)-proteins in coupling hypothalamic 5-HT(1A) receptors to effector mechanisms.
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Frank JL, Hendricks SE, Olson CH. Multiple ejaculations and chronic fluoxetine: effects on male rat copulatory behavior. Pharmacol Biochem Behav 2000; 66:337-42. [PMID: 10880687 DOI: 10.1016/s0091-3057(00)00191-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Male rats were treated with fluoxetine (FLX) or vehicle daily for 14 days and copulatory behavior tested on day 15. Rats were either mated to three ejaculations or to sexual exhaustion. Both standard measures and the mount bout analysis were used to evaluate the effects of the chronic FLX on male rat copulatory behavior. Only 56.25% of the animals treated with FLX achieved three ejaculations. FLX inhibited the consumatory aspect of male sexual behavior, especially the ability to achieve three ejaculations, but there was no effect on the propensity of the male to pursue the female. These differences were observed for the first three ejaculations. Analysis of the last three ejaculations in those animals that mated to exhaustion did not reveal an effect of FLX. The behavioral pattern of FLX-treated animals during the first three ejaculations resembled that observed during the last three ejaculatory series in the vehicle-treated animals that mated to exhaustion. The results are discussed in terms of the serotonergic effects on male rat sexual behavior.
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Affiliation(s)
- J L Frank
- Department of Psychology, University of Nebraska at Omaha, Omaha, NE 68182, USA
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Abstract
Selective serotonin (5-HT) reuptake inhibitors (SSRIs) are effective drugs for the treatment of several neuropsychiatric disorders associated with reduced serotonergic function. Serotonergic neurons play an important role in the regulation of neuroendocrine function. This review will discuss the acute and chronic effects of SSRIs on neuroendocrine function. Acute administration of SSRIs increases the secretion of several hormones, but chronic treatment with SSRIs does not alter basal blood levels of hormones. However, adaptive changes are induced by long-term treatment with SSRIs in serotonergic, noradrenergic and peptidergic neural function. These adaptive changes, particularly in the function of specific post-synaptic receptor systems, can be examined from altered adrenocorticotrophic hormone (ACTH), cortisol, oxytocin, vasopressin, prolactin, growth hormone (GH) and renin responses to challenges with specific agonists. Neuroendocrine challenge tests both in experimental animals and in humans indicate that chronic SSRIs produce an increase in serotonergic terminal function, accompanied by desensitization of post-synaptic 5-HT1A receptor-mediated ACTH, cortisol, GH and oxytocin responses, and by supersensitivity of post-synaptic 5-HT2A (and/or 5-HT2C) receptor-mediated secretion of hormones. Chronic exposure to SSRIs does not alter the neuroendocrine stress-response and produces inconsistent changes in alpha2 adrenoceptor-mediated GH secretion. Overall, the effects of SSRIs on neuroendocrine function are dependent on adaptive changes in specific neurotransmitter systems that regulate the secretion of specific hormones.
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Affiliation(s)
- D K Raap
- Department of Pharmacology, Loyola University Chicago, Stritch School of Medicine, Maywood, IL 60153, USA
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Abstract
Exposure to hostile conditions initiates the secretion of several hormones, including corticosterone/cortisol, catecholamines, prolactin, oxytocin, and renin, as part of the survival mechanism. Such conditions are often referred to as "stressors" and can be divided into three categories: external conditions resulting in pain or discomfort, internal homeostatic disturbances, and learned or associative responses to the perception of impending endangerment, pain, or discomfort ("psychological stress"). The hormones released in response to stressors often are referred to as "stress hormones" and their secretion is regulated by neural circuits impinging on hypothalamic neurons that are the final output toward the pituitary gland and the kidneys. This review discusses the forebrain circuits that mediate the neuroendocrine responses to stressors and emphasizes those neuroendocrine systems that have previously received little attention as stress-sensitive hormones: renin, oxytocin, and prolactin. Anxiolytic drugs of the benzodiazepine class and other drugs that affect catecholamine, GABAA, histamine, and serotonin receptors alter the neuroendocrine stress response. The effects of these drugs are discussed in relation to their effects on forebrain neural circuits that regulate stress hormone secretion. For psychological stressors such as conditioned fear, the neural circuits mediating neuroendocrine responses involve cortical activation of the basolateral amygdala, which in turn activates the central nucleus of the amygdala. The central amygdala then activates hypothalamic neurons directly, indirectly through the bed nucleus of the stria terminalis, and/or possibly via circuits involving brainstem serotonergic and catecholaminergic neurons. The renin response to psychological stress, in contrast to those of ACTH and prolactin, is not mediated by the bed nucleus of the stria terminalis and is not suppressed by benzodiazepine anxiolytics. Stressors that challenge cardiovascular homeostasis, such as hemorrhage, trigger a pattern of neuroendocrine responses that is similar to that observed in response to psychological stressors. These neuroendocrine responses are initiated by afferent signals from cardiovascular receptors which synapse in the medulla oblongata and are relayed either directly or indirectly to hypothalamic neurons controlling ACTH, prolactin, and oxytocin release. In contrast, forebrain pathways may not be essential for the renin response to hemorrhage. Thus current evidence indicates that although a diverse group of stressors initiate similar increases in ACTH, renin, prolactin, and oxytocin, the specific neural circuits and neurotransmitter systems involved in these responses differ for each neuroendocrine system and stressor category.
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Affiliation(s)
- L D Van de Kar
- Department of Pharmacology, Loyola University of Chicago, Stritch School of Medicine, 2160 South First Avenue, Maywood, Illinois, 60153, USA.
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Davidson C, Stamford JA. Contrasting effects of chronic paroxetine on 5-HT1A control of dorsal raphe cell firing and 5-HT release. Neuroreport 1998; 9:2535-8. [PMID: 9721928 DOI: 10.1097/00001756-199808030-00020] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To test the role of 5-HT1A receptors in the action of antidepressants, we investigated the effect of chronic paroxetine (10 mg/kg, p.o. for 21 days) on functional assays of 5-HT1A sensitivity. We constructed cumulative concentration response curves to the selective 5-HT1A agonist (+)-8-OH-DPAT on both extracellular recordings of 5-HT neurones and electrically stimulated 5-HT release in dorsal raphe brain slices. Chronic paroxetine desensitized the 5-HT1A receptors controlling firing, with an increase in EC50 from 10.7 nM to 46.2 nM 8-OH-DPAT. Chronic paroxetine did not, however, desensitize the 5-HT1A receptors controlling 5-HT release but increased the 8-OH-DPAT Emax from 54.9% to 79.2% inhibition of 5-HT release. These data suggest that there are either two distinct populations of 5-HT1A receptors or separate second messenger systems, one controlling 5-HT release and another influencing firing. Furthermore chronic paroxetine treatment can differentially modulate these different populations.
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Affiliation(s)
- C Davidson
- Academic Department of Anaesthesia and Intensive Care, St Bartholomew's and the Royal London School of Medicine and Dentistry, Royal London Hospital, UK
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Vicentic A, Li Q, Battaglia G, Van de Kar LD. WAY-100635 inhibits 8-OH-DPAT-stimulated oxytocin, ACTH and corticosterone, but not prolactin secretion. Eur J Pharmacol 1998; 346:261-6. [PMID: 9652368 DOI: 10.1016/s0014-2999(97)01607-5] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Previous studies suggest that the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) increases the secretion of oxytocin, adrenocorticotropic hormone (ACTH), corticosterone and prolactin but not renin. However, the lack of selective 5-HT1A receptor antagonists made it difficult to confirm that 5-HT1A receptors mediate the neuroendocrine responses to 8-OH-DPAT. This study investigated the effects of increasing doses of a selective 5-HT1A receptor antagonist, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexanecarboxamide (WAY-100635) on neuroendocrine responses induced by the 5-HT1A receptor agonist 8-OH-DPAT in adult male rats. 8-OH-DPAT, 500 microg/kg s.c., increased plasma levels of oxytocin (to 970% above basal levels); ACTH (to 1622% above basal levels), corticosterone (to 458% above basal levels) and prolactin (to 313% above basal levels), but not renin. The lowest dose of WAY-100635 (0.1 mg/kg s.c.) significantly inhibited the 8-OH-DPAT-induced increase in plasma oxytocin but not ACTH or corticosterone levels. At a dose of 1 mg/kg (s.c.), WAY-100635 completely blocked the oxytocin and ACTH responses and maximally inhibited the corticosterone response to 8-OH-DPAT, although corticosterone levels were still above basal. In contrast, the increase in prolactin secretion, induced by 8-OH-DPAT was not inhibited by any dose of WAY-100635. At the highest dose of WAY-100635 (10 mg/kg, s.c.), basal prolactin levels were markedly elevated (1550%) and administration of 8-OH-DPAT significantly elevated plasma renin concentration. Taken together, these data indicate that: (1) 8-OH-DPAT stimulates oxytocin, ACTH, and corticosterone but not prolactin secretion via activation of 5-HT1A receptors and (2) blockade of 5-HT1A receptors may unmask 8-OH-DPAT simulation of renin secretion via non-5-HT1A receptor mechanisms.
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Affiliation(s)
- A Vicentic
- Department of Pharmacology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA
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