151
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de Kock CPJ, Cornelisse LN, Burnashev N, Lodder JC, Timmerman AJ, Couey JJ, Mansvelder HD, Brussaard AB. NMDA receptors trigger neurosecretion of 5-HT within dorsal raphe nucleus of the rat in the absence of action potential firing. J Physiol 2006; 577:891-905. [PMID: 17053037 PMCID: PMC1890386 DOI: 10.1113/jphysiol.2006.115311] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Activity and calcium-dependent release of neurotransmitters from the somatodendritic compartment is an important signalling mechanism between neurones throughout the brain. NMDA receptors and vesicles filled with neurotransmitters occur in close proximity in many brain areas. It is unknown whether calcium influx through these receptors can trigger the release of somatodendritic vesicles directly, or whether postsynaptic action potential firing is necessary for release of these vesicles. Here we addressed this question by studying local release of serotonin (5-HT) from dorsal raphé nucleus (DRN) neurones. We performed capacitance measurements to monitor the secretion of vesicles in giant soma patches, in response to short depolarizations and action potential waveforms. Amperometric measurements confirmed that secreted vesicles contained 5-HT. Surprisingly, two-photon imaging of DRN neurones in slices revealed that dendritic calcium concentration changes in response to somatic firing were restricted to proximal dendritic areas. This implied that alternative calcium entry pathways may dominate the induction of vesicle secretion from distal dendrites. In line with this, transient NMDA receptor activation, in the absence of action potential firing, was sufficient to induce capacitance changes. By monitoring GABAergic transmission onto DRN 5-HT neurones in slices, we show that endogenous NMDA receptor activation, in the absence of postsynaptic firing, induced release of 5-HT, which in turn increased the frequency of GABAergic inputs through activation of 5-HT(2) receptors. We propose here that calcium influx through NMDA receptors can directly induce postsynaptic 5-HT release from DRN neurones, which in turn may facilitate GABAergic input onto these cells.
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Affiliation(s)
- C P J de Kock
- Department of Experimental Neurophysiology, Centre for Neurogenomics and Cognitive Research, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands
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152
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Janusonis S, Anderson GM, Shifrovich I, Rakic P. Ontogeny of brain and blood serotonin levels in 5-HT receptor knockout mice: potential relevance to the neurobiology of autism. J Neurochem 2006; 99:1019-31. [PMID: 16981893 DOI: 10.1111/j.1471-4159.2006.04150.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The most consistent neurochemical finding in autism has been elevated group mean levels of blood platelet 5-hydroxytryptamine (5-HT, serotonin). The origin and significance of this platelet hyperserotonemia remain poorly understood. The 5-HT(1A) receptor plays important roles in the developing brain and is also expressed in the gut, the main source of platelet 5-HT. Post-natal tissue levels of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA) and tryptophan were examined in the brain, duodenum and blood of 5-HT(1A) receptor-knockout and wild-type mice. At 3 days after birth, the knockout mice had lower mean brain 5-HT levels and normal mean platelet 5-HT levels. Also, at 3 days after birth, the mean tryptophan levels in the brain, duodenum and blood of the knockout mice were around 30% lower than those of the wild-type mice. By 2 weeks after birth, the mean brain 5-HT levels of the knockout mice normalized, but their mean platelet 5-HT levels became 24% higher than normal. The possible causes of these dynamic shifts were explored by examining correlations between central and peripheral levels of 5-HT, 5-HIAA and tryptophan. The results are discussed in relation to the possible role of 5-HT in the ontogeny of autism.
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Affiliation(s)
- Skirmantas Janusonis
- Department of Neurobiology, Yale University School of Medicine, New Haven, Connecticut, USA.
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153
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Wersinger C, Rusnak M, Sidhu A. Modulation of the trafficking of the human serotonin transporter by human alpha-synuclein. Eur J Neurosci 2006; 24:55-64. [PMID: 16882008 DOI: 10.1111/j.1460-9568.2006.04900.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
alpha-Synuclein (alpha-Syn), a protein primarily localized in the presynaptic compartment of neurons, is known to regulate dopaminergic neurotransmission by negatively modulating dopamine transporter activity and regulating its trafficking to or away from the cell surface. Given the considerable homology between dopamine transporters and the serotonin (5-HT) transporter (SERT), we examined whether alpha-Syn could similarly regulate SERT function. Increasing expression levels of human alpha-Syn gradually decreased [(3)H]5-HT uptake by human SERT in cotransfected Ltk(-) cells, by diminishing its V(max) without changing its K(m), as compared to cells expressing only SERT. Biotinylation studies to label cell-surface proteins showed that alpha-Syn decreased the levels of SERT present at the plasma membrane. alpha-Syn and SERT were able to coimmunoprecipitate (co-IP), suggesting heteromeric complexes between these two proteins through direct protein-protein interactions. The negative modulation of SERT activity by alpha-Syn occurred through the non-Abeta-amyloid component (NAC) domain of alpha-Syn (aa58-107); DNA constructs encoding this region mimicked the full-length alpha-Syn protein by decreasing [(3)H]5-HT uptake by the transporter. Furthermore, only the constructs encoding the NAC domain of alpha-Syn prevented the co-IPs between full-length alpha-Syn and SERT, in both transfected cells and in rat solubilized lysates isolated from the prefrontal cortex. These studies suggest a novel physiological role for alpha-Syn in regulating SERT activity and may be of relevance in certain mental illnesses and in depression, in which SERT function is believed to be dysregulated.
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Affiliation(s)
- Christophe Wersinger
- Department of Biochemistry, Molecular and Cell Biology, Georgetown University, The Research Building, Room W222, 3970 Reservoir Road, NW, Washington, DC 20007, USA
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154
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Lechin F, van der Dijs B, Hernández-Adrián G. Dorsal raphe vs. median raphe serotonergic antagonism. Anatomical, physiological, behavioral, neuroendocrinological, neuropharmacological and clinical evidences: relevance for neuropharmacological therapy. Prog Neuropsychopharmacol Biol Psychiatry 2006; 30:565-85. [PMID: 16436311 DOI: 10.1016/j.pnpbp.2005.11.025] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/30/2005] [Indexed: 01/28/2023]
Abstract
Monoaminergic neurons located in the central nervous system (CNS) are organized into complex circuits which include noradrenergic (NA), adrenergic (Ad), dopaminergic (DA), serotonergic (5-HT), histaminergic (H), GABA-ergic and glutamatergic systems. Most of these circuits are composed of more than one and often several types of the above neurons. Such physiologically flexible circuits respond appropriately to both external and internal stimuli which, if not modulated adequately, can trigger pathophysiologic responses. A great deal of research has been devoted to mapping the multiple functions of the CNS circuitry, thereby forming the basis for effective neuropharmacological therapeutic approaches. Such lineal strategies that seek to normalize complex and mixed physiological disorders, however, meet only partial therapeutic success and are often followed by undesirable side effects and/or total failure. In light of these, we have worked to develop possible models of CNS circuitry that are less affected by physiological interaction using the models to design more effective therapeutic approaches. In the present review, we cite and present evidence supporting the dorsal raphe versus median raphe serotonergic circuitry as one model of a reliable paradigm, necessary to the clear understanding and therapy of many psychiatric and even non-psychiatric disturbances.
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Affiliation(s)
- Fuad Lechin
- Department of Physiological Sciences, Section of Neurochemical, Instituto de Medicina Experimental, Universidad Central de Venezuela, Caracas, Venezuela.
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155
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Brevard ME, Meyer JS, Harder JA, Ferris CF. Imaging brain activity in conscious monkeys following oral MDMA ("ecstasy"). Magn Reson Imaging 2006; 24:707-14. [PMID: 16824965 DOI: 10.1016/j.mri.2006.03.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2005] [Accepted: 03/12/2006] [Indexed: 11/27/2022]
Abstract
Recreational use of 3,4-methylenedioxymethamphetamine (MDMA;"ecstasy") poses worldwide potential health problems. Clinical studies show that repeated exposure to low oral doses of MDMA has toxic effects on the brain, altering cognitive and psychosocial behavior. Functional magnetic resonance imaging in conscious marmoset monkeys was used to evaluate the sensitivity of the brain to an oral dose of MDMA (1 mg/kg). Following MDMA administration, the midbrain raphe nuclei and substantia nigra, major sources of serotonin and dopamine, were activated as were the hippocampus, hypothalamus and amygdala. The corticostriatal circuit of dorsal thalamus, sensorimotor cortex and basal ganglia showed a robust, coherent activation pattern. Two key reward areas, the nucleus accumbens and prefrontal cortex, and most other cortical regions showed little activation. The visual cortex, however, showed intense activation without applied visual stimuli. These data identify brain areas and functional circuits sensitive to a recreational dose of MDMA, some of which may be vulnerable to long-term intermittent exposure to this drug.
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Affiliation(s)
- Mathew E Brevard
- Center for Comparative Neuroimaging, University of Massachusetts Medical School, Worcester, MA 01655, USA.
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156
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Forster GL, Feng N, Watt MJ, Korzan WJ, Mouw NJ, Summers CH, Renner KJ. Corticotropin-releasing factor in the dorsal raphe elicits temporally distinct serotonergic responses in the limbic system in relation to fear behavior. Neuroscience 2006; 141:1047-1055. [PMID: 16713119 DOI: 10.1016/j.neuroscience.2006.04.006] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Revised: 02/12/2006] [Accepted: 04/06/2006] [Indexed: 11/17/2022]
Abstract
The neurotransmitters serotonin and corticotrophin-releasing factor are thought to play an important role in fear and anxiety behaviors. This study aimed to determine the relationship between corticotrophin-releasing factor-evoked changes in serotonin levels within discrete regions of the limbic system and the expression of fear behavior in rats. The effects of corticotrophin-releasing factor administration to the serotonin cell body regions of the dorsal raphe nucleus on fear behavior, behavioral activity, and extracellular serotonin levels were assessed in freely moving rats with microdialysis probes implanted into the central nucleus of the amygdala and the medial prefrontal cortex. Infusion of corticotrophin-releasing factor (0.5 microg) into the dorsal raphe rapidly induced freezing behavior, which was positively correlated with an immediate increase in serotonin release in the central nucleus of the amygdala. In contrast, cessation of freezing behavior correlated with a delayed and prolonged increase in serotonin release within the medial prefrontal cortex. Our findings suggest that corticotrophin-releasing factor-induced freezing behavior is associated with regionally and temporally distinct serotonergic responses in the limbic system that may reflect differing roles for these regions in the expression of fear/anxiety behavior.
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Affiliation(s)
- G L Forster
- Division of Basic Biomedical Sciences, Neuroscience Group, Sanford School of Medicine at the University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA.
| | - N Feng
- Department of Biology, University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA
| | - M J Watt
- Division of Basic Biomedical Sciences, Neuroscience Group, Sanford School of Medicine at the University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA; Department of Biology, University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA
| | - W J Korzan
- Department of Biology, University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA; Department of Biological Sciences, Stanford University, 371 Serra Mall, Stanford, CA 94305, USA
| | - N J Mouw
- Division of Basic Biomedical Sciences, Neuroscience Group, Sanford School of Medicine at the University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA; Department of Biology, University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA
| | - C H Summers
- Division of Basic Biomedical Sciences, Neuroscience Group, Sanford School of Medicine at the University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA; Department of Biology, University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA
| | - K J Renner
- Division of Basic Biomedical Sciences, Neuroscience Group, Sanford School of Medicine at the University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA; Department of Biology, University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA
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157
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Millan MJ. Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application. Pharmacol Ther 2006; 110:135-370. [PMID: 16522330 DOI: 10.1016/j.pharmthera.2005.11.006] [Citation(s) in RCA: 388] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Accepted: 11/28/2005] [Indexed: 12/20/2022]
Abstract
Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.
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Affiliation(s)
- Mark J Millan
- Institut de Recherches Servier, Centre de Recherches de Croissy, Psychopharmacology Department, 125, Chemin de Ronde, 78290-Croissy/Seine, France.
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158
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Ma Z, Pearson E, Isgor C, Tao R. Evidence of reuptake inhibition responsible for mecamylamine-evoked increases in extracellular serotonin. Brain Res 2006; 1073-1074:321-4. [PMID: 16458272 DOI: 10.1016/j.brainres.2005.12.080] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Revised: 12/16/2005] [Accepted: 12/16/2005] [Indexed: 11/23/2022]
Abstract
The present report using microdialysis approach investigates the neurochemical mechanism of mecamylamine in the regulation of extracellular serotonin in the dorsal raphe nucleus of freely behaving rats. These results suggest that mecamylamine may block serotonin reuptake, the effect consistent with its efficacy of antidepressant.
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Affiliation(s)
- Zhiyuan Ma
- Department of Biomedical Science, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431, USA
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159
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Tao R, Ma Z, McKenna JT, Thakkar MM, Winston S, Strecker RE, McCarley RW. Differential effect of orexins (hypocretins) on serotonin release in the dorsal and median raphe nuclei of freely behaving rats. Neuroscience 2006; 141:1101-5. [PMID: 16820265 DOI: 10.1016/j.neuroscience.2006.05.027] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Revised: 05/12/2006] [Indexed: 10/24/2022]
Abstract
Orexin (hypocretin)-containing neurons in the perifornical hypothalamus project to widespread regions of the brain, including the dorsal and median raphe nuclei [Peyron C, Tighe DK, van den Pol AN, de Lecea L, Heller HC, Sutcliffe JG, Kilduff TS (1998) Neurons containing hypocretin (orexin) project to multiple neuronal systems. J Neurosci 18:9996-10015; Wang QP, Koyama Y, Guan JL, Takahashi K, Kayama Y, Shioda S (2005) The orexinergic synaptic innervation of serotonin- and orexin 1-receptor-containing neurons in the dorsal raphe nucleus. Regul Pept 126:35-42]. Orexin-A or orexin-B was infused by reverse microdialysis into the dorsal raphe nucleus or median raphe nucleus of freely behaving rats, and extracellular serotonin was simultaneously collected by microdialysis and analyzed by high-performance liquid chromatography. We have found that orexin-A produced a dose-dependent increase of serotonin in the dorsal raphe nucleus, but not in the median raphe nucleus. However, orexin-B elicited a small but significant effect in both the dorsal raphe nucleus and median raphe nucleus. Orexins may have regionally selective effects on serotonin release in the CNS, implying a unique interaction between orexins and serotonin in the regulation of activities including sleep-wakefulness.
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Affiliation(s)
- R Tao
- Boston VA Healthcare/Harvard Medical School, Department of Psychiatry, Laboratory of Neuroscience, 940 Belmont Street, Brockton, MA 02301, USA.
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160
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Bertrand PP, Paranavitane UT, Chavez C, Gogos A, Jones M, van den Buuse M. The effect of low estrogen state on serotonin transporter function in mouse hippocampus: A behavioral and electrochemical study. Brain Res 2005; 1064:10-20. [PMID: 16298349 DOI: 10.1016/j.brainres.2005.10.018] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Revised: 10/02/2005] [Accepted: 10/11/2005] [Indexed: 11/19/2022]
Abstract
Defects in serotonergic transmission, including serotonin transporter (SERT) function, have been implicated in depression, anxiety disorders and some aspects of schizophrenia. The sex steroid hormone estrogen is known to modulate functional SERT activity, but whether it is up- or down-regulated is unclear. The aim of the present study was to examine the effect of a low estrogen state in mice on the behavioral effect of drugs acting through the SERT, serotonin uptake kinetics and SERT density in the hippocampus. We compared control mice, ovariectomized (OVX) C57BL/6J mice and aromatase knockout (ArKO) mice that are unable to produce estrogen. Fluoxetine treatment, but not fenfluramine treatment, significantly increased prepulse inhibition (PPI), a measure of sensorimotor gating, in C57BL/6J mice. The effect of fluoxetine was greater in OVX compared to sham-operated mice. In ArKO and J129 wild-type mice, fluoxetine increased PPI to the same extent while fenfluramine increased PPI more in ArKO mice compared to controls. Measurement of the time-course for diffusion and reuptake of exogenous serotonin in the CA3 region of the hippocampus showed that, in OVX mice, the fluoxetine-induced slowing of signal decay after application of serotonin was enhanced when compared to sham-operated controls. Similarly, in ArKO mice, the effect of fluoxetine was enhanced, suggesting that SERT function was greater than in J129 wild-type controls. Measurement of SERT density by [3H]-citalopram autoradiography, revealed an 18% decrease in hippocampus of OVX mice compared to intact controls. SERT density was also significantly reduced in nucleus accumbens (26%) but not in other regions, such as the raphe nuclei. Together, these results suggest that a low estrogen state increases SERT activity in the hippocampus despite an apparent reduction in SERT density. The behavioral consequences of these changes depend on the model of estrogen state used.
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Affiliation(s)
- Paul P Bertrand
- Department of Physiology, University of Melbourne, Parkville VIC 3010, Australia
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161
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Olivier B, van Oorschot R. 5-HT1B receptors and aggression: A review. Eur J Pharmacol 2005; 526:207-17. [PMID: 16310769 DOI: 10.1016/j.ejphar.2005.09.066] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2005] [Accepted: 09/23/2005] [Indexed: 01/19/2023]
Abstract
The serotonergic (5-HT) system in the brain is involved in the modulation of offensive aggressive behavior. The dogma that activity of the 5-HT system is inversely related to aggression is obsolete now. Research on the status of the 5-HT system before, during and after the execution of aggression is ongoing but has not yet led to a clear picture about the actual functional role of the 5-HT system, the more because state versus trait aggression seems to play a pivotal role in the outcome. Pharmacological challenges pinpoint 5-HT(1A) and 5-HT(1B) receptors as key players in the modulation of offensive aggression. This review emphasizes in particular the role of postsynaptic 5-HT(1B) (hetero) receptors as a premier site to modulate offensive aggression. Modulation of the firing and 5-HT release of the serotonergic neuron, via presynaptic 5-HT(1A) (auto) receptors, presynaptic 5-HT(1B) (auto) receptors and serotonergic transporters, may also have striking influences on aggression under certain conditions. Therefore, it is hypothesized that postsynaptic 5-HT(1B) (hetero) receptors directly influence the executive, consummatory phases of agonistic behavior, whereas presynaptic serotonergic feedback systems are particularly useful in the introductory (appetitive) phases of the agonistic behavioral complex.
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Affiliation(s)
- Berend Olivier
- Department of Psychopharmacology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Sorbonnelaan 16, The Netherlands.
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162
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Mlinar B, Tatini F, Ballini C, Nencioni S, Della Corte L, Corradetti R. Differential autoinhibition of 5-hydroxytryptamine neurons by 5-hydroxytryptamine in the dorsal raphe nucleus. Neuroreport 2005; 16:1351-5. [PMID: 16056138 DOI: 10.1097/01.wnr.0000175249.25535.bf] [Citation(s) in RCA: 16] [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
5-Hydroxytryptamine neurons in the dorsal raphe nucleus are under autoinhibitory control by endogenous 5-hydroxytryptamine. Tonic activation of 5-hydroxytryptamine 1A autoreceptors was demonstrated in awake animals, but was inconsistently observed in anaesthetized animals and slice preparations, leading to questioning of its physiological significance. We re-evaluated autoinhibition in single-unit recordings from deeply seated 5-hydroxytryptamine neurons in slices in which endogenous 5-hydroxytryptamine bioavailability was restored by supplementing its precursor L-tryptophan. In these conditions, the application of the neutral 5-hydroxytryptamine 1A receptor antagonist WAY-100635 markedly increased 5-hydroxytryptamine neuron firing. Responses to WAY-100635 in single experiments ranged from a lack of effect to a several-fold increase in firing rate, suggesting that 5-hydroxytryptamine neurons in the dorsal raphe nucleus represent a heterogeneous population regarding their susceptibility to autoinhibition by endogenous 5-hydroxytryptamine.
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Affiliation(s)
- Boris Mlinar
- Department of Preclinical and Clinical Pharmacology Mario Aiazzi-Mancini, University of Florence, Viale G. Pieraccini 6, 50139 Florence, Italy.
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163
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Ma Z, Strecker RE, McKenna JT, Thakkar MM, McCarley RW, Tao R. Effects on serotonin of (-)nicotine and dimethylphenylpiperazinium in the dorsal raphe and nucleus accumbens of freely behaving rats. Neuroscience 2005; 135:949-58. [PMID: 16154286 DOI: 10.1016/j.neuroscience.2005.06.074] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 06/14/2005] [Accepted: 06/17/2005] [Indexed: 10/25/2022]
Abstract
The aim of this study was to investigate the neurochemical mechanism underlying the effect of nicotine and dimethylphenylpiperazinium (DMPP) on 5-hydroxytryptamine (5-HT) release in the dorsal raphe nucleus and nucleus accumbens of freely behaving rats. For comparison, lobeline, cytisine and RJR-2403 were also investigated. It was found that all drugs, when infused locally, evoked an increase of 5-HT in the dorsal raphe nucleus. However, the magnitudes of the 5-HT increase were comparatively different between the drugs in the ranking of their potency: DMPP>RJR 2403>>nicotine>lobeline>cytisine. Both methyllycaconitine, a nicotinic acetylcholine receptor (nAChR) antagonist and methyllycaconitine, a selective alpha7-containing nAChR antagonist blocked the effects of nicotine and DMPP, suggesting that alpha7 subunit mediated the increases in 5-HT. However, DMPP was reported to increase 5-HT using non-nAChR mechanism [Lendvai B, Sershen H, Lajtha A, Santha E, Baranyi M, Vizi ES (1996) Differential mechanisms involved in the effect of nicotinic agonists DMPP and lobeline to release [3H]5-HT from rat hippocampal slices. Neuropharmacology 35:1769-1777]. To test if 5-HT carriers were involved, a selective 5-HT reuptake inhibitor citalopram (1 microM) was infused into the dorsal raphe nucleus before administration of nicotine or DMPP. As a result, citalopram significantly blocked the effect of DMPP, whereas it had no influence on nicotine. Finally, the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) was used to test whether the increases in 5-HT were depolarization-dependent. Administration of 8-OH-DPAT (0.1 mg/kg, s.c.) produced significant decreases in 5-HT in the animals treated with nicotine. In contrast, the effect of DMPP was not altered by 8-OH-DPAT, suggesting that the increases in 5-HT were independent of cell membrane depolarization. In conclusion, there are different mechanisms involved in nicotine- and DMPP-evoked increases in 5-HT. This is consistent with prior work suggesting DMPP may primarily act on 5-HT carriers.
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Affiliation(s)
- Z Ma
- Department of Biomedical Science, Charles E. Schmidt College of Science, Florida Atlantic University, 777 Glades Road, P.O. Box 3091, Boca Raton, FL 33431-0991, USA
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164
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Lee M, Bailer UF, Frank GK, Henry SE, Meltzer CC, Price JC, Mathis CA, Putnam KT, Ferrell RE, Hariri AR, Kaye WH. Relationship of a 5-HT transporter functional polymorphism to 5-HT1A receptor binding in healthy women. Mol Psychiatry 2005; 10:715-6. [PMID: 15940302 DOI: 10.1038/sj.mp.4001680] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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165
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Janusonis S. Statistical distribution of blood serotonin as a predictor of early autistic brain abnormalities. Theor Biol Med Model 2005; 2:27. [PMID: 16029508 PMCID: PMC1199627 DOI: 10.1186/1742-4682-2-27] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Accepted: 07/19/2005] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A wide range of abnormalities has been reported in autistic brains, but these abnormalities may be the result of an earlier underlying developmental alteration that may no longer be evident by the time autism is diagnosed. The most consistent biological finding in autistic individuals has been their statistically elevated levels of 5-hydroxytryptamine (5-HT, serotonin) in blood platelets (platelet hyperserotonemia). The early developmental alteration of the autistic brain and the autistic platelet hyperserotonemia may be caused by the same biological factor expressed in the brain and outside the brain, respectively. Unlike the brain, blood platelets are short-lived and continue to be produced throughout the life span, suggesting that this factor may continue to operate outside the brain years after the brain is formed. The statistical distributions of the platelet 5-HT levels in normal and autistic groups have characteristic features and may contain information about the nature of this yet unidentified factor. RESULTS The identity of this factor was studied by using a novel, quantitative approach that was applied to published distributions of the platelet 5-HT levels in normal and autistic groups. It was shown that the published data are consistent with the hypothesis that a factor that interferes with brain development in autism may also regulate the release of 5-HT from gut enterochromaffin cells. Numerical analysis revealed that this factor may be non-functional in autistic individuals. CONCLUSION At least some biological factors, the abnormal function of which leads to the development of the autistic brain, may regulate the release of 5-HT from the gut years after birth. If the present model is correct, it will allow future efforts to be focused on a limited number of gene candidates, some of which have not been suspected to be involved in autism (such as the 5-HT4 receptor gene) based on currently available clinical and experimental studies.
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Affiliation(s)
- Skirmantas Janusonis
- Department of Neurobiology, Yale University School of Medicine, New Haven, CT 06520-8001, USA.
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166
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Fernández-Pastor B, Mateo Y, Gómez-Urquijo S, Javier Meana J. Characterization of noradrenaline release in the locus coeruleus of freely moving awake rats by in vivo microdialysis. Psychopharmacology (Berl) 2005; 180:570-9. [PMID: 15717207 DOI: 10.1007/s00213-005-2181-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2004] [Accepted: 01/10/2005] [Indexed: 11/26/2022]
Abstract
RATIONALE The origin and regulation of noradrenaline (NA) in the locus coeruleus (LC) is unknown. OBJECTIVES The neurochemical features of NA overflow (nerve impulse dependence, neurotransmitter synthesis, vesicle storage, reuptake, alpha2-adrenoceptor-mediated regulation) were characterized in the LC. METHODS Brain microdialysis was performed in awake rats. Dialysates were analyzed for NA. RESULTS NA in the LC decreased via local infusion of Ca2+-free medium (-42+/-5%) or the sodium channel blocker tetrodotoxine (TTX) (-47+/-8%) but increased (333+/-40%) via KCl-induced depolarization. The tyrosine hydroxylase (TH) inhibitor alpha-methyl-p-tyrosine (250 mg kg(-1), i.p.) and the vesicle depletory drug reserpine (5 mg kg(-1), i.p.) decreased NA. Therefore, extracellular NA in the LC satisfies the criteria for an impulse flow-dependent vesicular exocytosis of neuronal origin. Local perfusion of the alpha2-adrenoceptor agonist clonidine (0.1-100 microM) decreased NA (E(max)=-79+/-5%) in the LC, whereas the opposite effect (E(max)=268+/-53%) was observed with the alpha2A-adrenoceptor antagonist BRL44408 (0.1-100 microM). This suggests a tonic modulation of NA release through local alpha2A-adrenoceptors. The selective NA reuptake inhibitor desipramine (DMI) (0.1-100 microM) administered into the LC increased NA in the LC (E(max)=223+/-40%) and simultaneously decreased NA in the cingulate cortex, confirming the modulation exerted by NA in the LC on firing activity of noradrenergic cells and on the subsequent NA release in noradrenergic terminals. CONCLUSION Synaptic processes underlying NA release in the LC are similar to those in noradrenergic terminal areas. NA in the LC could represent local somatodendritic release, but also the presence of neurotransmitter release from collateral axon terminals.
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167
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Greenwood BN, Foley TE, Day HEW, Burhans D, Brooks L, Campeau S, Fleshner M. Wheel running alters serotonin (5-HT) transporter, 5-HT1A, 5-HT1B, and alpha 1b-adrenergic receptor mRNA in the rat raphe nuclei. Biol Psychiatry 2005; 57:559-68. [PMID: 15737672 DOI: 10.1016/j.biopsych.2004.11.025] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2004] [Revised: 09/03/2004] [Accepted: 11/16/2004] [Indexed: 10/25/2022]
Abstract
BACKGROUND Altered serotonergic (5-HT) neurotransmission is implicated in the antidepressant and anxiolytic properties of physical activity. In the current study, we investigated whether physical activity alters factors involved in the regulation of central 5-HT neural activity. METHODS In situ hybridization was used to quantify levels of 5-HT transporter (5-HTT), 5-HT(1A), 5-HT(1B), and alpha(1b)-adrenergic receptor (alpha(1b) ADR) messenger ribonucleic acids (mRNAs) in the dorsal (DRN) and median raphe (MR) nuclei of male Fischer rats after either sedentary housing or 3 days, 3 weeks, or 6 weeks of wheel running. RESULTS Wheel running produced a rapid and lasting reduction of 5-HT(1B) mRNA in the ventral DRN. Three weeks of wheel running decreased 5-HTT mRNA in the DRN and MR and increased alpha(1b) ADR mRNA in the DRN. After 6 weeks of wheel running, 5-HTT mRNA remained reduced, but alpha(1b) ADR mRNA returned to sedentary levels. Serotonin(1A) mRNA was increased in the MR and certain DRN subregions after 6 weeks only. CONCLUSIONS Data suggest that the central 5-HT system is sensitive to wheel running in a time-dependent manner. The observed changes in mRNA regulation in a subset of raphe nuclei might contribute to the stress resistance produced by wheel running and the antidepressant and anxiolytic effects of physical activity.
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MESH Headings
- Analysis of Variance
- Animals
- Behavior, Animal
- Body Weight/physiology
- Gene Expression Regulation/physiology
- In Situ Hybridization/methods
- Male
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/metabolism
- Membrane Transport Proteins/genetics
- Membrane Transport Proteins/metabolism
- Motor Activity/physiology
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- RNA, Messenger/metabolism
- Raphe Nuclei/anatomy & histology
- Raphe Nuclei/metabolism
- Rats
- Rats, Inbred F344
- Receptor, Serotonin, 5-HT1A/genetics
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptor, Serotonin, 5-HT1B/genetics
- Receptor, Serotonin, 5-HT1B/metabolism
- Receptors, Adrenergic, alpha-1/genetics
- Receptors, Adrenergic, alpha-1/metabolism
- Running
- Serotonin Plasma Membrane Transport Proteins
- Time Factors
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Affiliation(s)
- Benjamin N Greenwood
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado 80309-0354, USA
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168
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Liu RJ, Lambe EK, Aghajanian GK. Somatodendritic autoreceptor regulation of serotonergic neurons: dependence on L-tryptophan and tryptophan hydroxylase-activating kinases. Eur J Neurosci 2005; 21:945-58. [PMID: 15787701 DOI: 10.1111/j.1460-9568.2005.03930.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The somatodendritic 5-HT(1A) autoreceptor has been considered a major determinant of the output of the serotonin (5-HT) neuronal system. However, recent studies in brain slices from the dorsal raphe nucleus have questioned the relevance of 5-HT autoinhibition under physiological conditions. In the present study, we found that the difficulty in demonstrating 5-HT tonic autoinhibition in slice results from in vitro conditions that are unfavorable for sustaining 5-HT synthesis. Robust, tonic 5-HT(1A) autoinhibition can be restored by reinstating in vivo 5-HT synthesizing conditions with the initial 5-HT precursor l-tryptophan and the tryptophan hydroxylase co-factor tetrahydrobiopterin (BH(4)). The presence of tonic autoinhibition under these conditions was revealed by the disinhibitory effect of a low concentration of the 5-HT(1A) antagonist WAY 100635. Neurons showing an autoinhibitory response to L-tryptophan were confirmed immunohistochemically to be serotonergic. Once conditions for tonic autoinhibition had been established in raphe slice, we were able to show that 5-HT autoinhibition is critically regulated by the tryptophan hydroxylase-activating kinases calcium/calmodulin protein kinase II (CaMKII) and protein kinase A (PKA). In addition, at physiological concentrations of L-tryptophan, there was an augmentation of 5-HT(1A) receptor-mediated autoinhibition when the firing of 5-HT cells activated with increasing concentrations of the alpha(1) adrenoceptor agonist phenylephrine. Increased calcium influx at higher firing rates, by activating tryptophan hydroxylase via CaMKII and PKA, can work together with tryptophan to enhance negative feedback control of the output of the serotonergic system.
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Affiliation(s)
- Rong-Jian Liu
- Department of Psychiatry, Yale School of Medicine, New Haven, CT, USA.
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169
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Janusonis S. Serotonergic paradoxes of autism replicated in a simple mathematical model. Med Hypotheses 2005; 64:742-50. [PMID: 15694691 DOI: 10.1016/j.mehy.2004.09.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2004] [Accepted: 09/05/2004] [Indexed: 10/26/2022]
Abstract
The biological causes of autism are unknown. Since the early 1960s, the most consistent pathophysiological finding in autistic individuals has been their statistically elevated blood 5-hydroxytryptamine (5-HT, serotonin) levels. However, many autistic individuals have normal blood 5-HT levels, so this finding has been difficult to interpret. The serotonin transporter (SERT) controls 5-HT uptake by blood platelets and has been implicated in autism, but recent studies have found no correlation between SERT polymorphisms and autism. Finally, autism is considered a brain disorder, but studies have so far failed to find consistent serotonergic abnormalities in autistic brains. A simple mathematical model may account for these paradoxes, if one assumes that autism is associated with the failure of a molecular mechanism that both regulates 5-HT release from gut enterochromaffin cells and mediates 5-HT signaling in the brain. Some 5-HT receptors may play such a dual role. While the failure of such a mechanism may lead to consistent abnormalities of synaptic transmission with no alteration of brain 5-HT levels, its effects on blood 5-HT levels may appear paradoxical.
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Affiliation(s)
- Skirmantas Janusonis
- Department of Neurobiology, Yale University School of Medicine, P.O. Box 208001, New Haven, CT 06520-8001, USA.
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170
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Adell A, Artigas F. The somatodendritic release of dopamine in the ventral tegmental area and its regulation by afferent transmitter systems. Neurosci Biobehav Rev 2004; 28:415-31. [PMID: 15289006 DOI: 10.1016/j.neubiorev.2004.05.001] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2004] [Revised: 05/12/2004] [Accepted: 05/12/2004] [Indexed: 10/26/2022]
Abstract
The release of dopamine in the ventral tegmental area (VTA) plays an important role in the autoinhibition of the dopamine neurons of the mesocorticolimbic system through the activation of somatodendritic dopamine D2 autoreceptors. Accordingly, the intra-VTA application of dopamine D2 receptor agonists reduces the firing rate and release of dopamine in the VTA, and this control appears to possess a tonic nature because the corresponding antagonists enhance the somatodendritic release of the transmitter. In addition, the release of dopamine in the VTA is increased by potassium or veratridine depolarization and abolished by tetrodotoxin and calcium omission. Overall, it appears that the somatodendritic release of dopamine is consistently lower than that in nerve endings. Apart from intrinsic dopaminergic mechanisms, other transmitter systems such as serotonin, noradrenaline, acetylcholine, GABA and glutamate play a role in the control of the activity of dopaminergic neurons of the VTA, although the final action depends on the particular receptor involved as well as the neuronal type where it is localized. Given the involvement of the mesocorticolimbic dopaminergic systems in the pathogenesis of severe neuropsychiatric disorders such as schizophrenia, the knowledge of the factors that regulate the release of dopamine in the VTA could provide new insight into the ethiogenesis of the disease as well as its implication on the mechanisms of action of therapeutic drugs.
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Affiliation(s)
- Albert Adell
- Department of Neurochemistry, Institut d'Investigacions Biomèdiques de Barcelona, CSIC (IDIBAPS), Carrer Rosselló 161, 6th floor, E-08036 Barcelona, Spain.
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171
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Yan QS, Zheng SZ, Yan SE. Involvement of 5-HT1B receptors within the ventral tegmental area in regulation of mesolimbic dopaminergic neuronal activity via GABA mechanisms: a study with dual-probe microdialysis. Brain Res 2004; 1021:82-91. [PMID: 15328035 DOI: 10.1016/j.brainres.2004.06.053] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/27/2004] [Indexed: 11/21/2022]
Abstract
This study was designed to assess the involvement of 5-HT1B receptors within the ventral tegmental area (VTA) in the regulation of mesolimbic dopaminergic transmission. Dual-probe microdialysis was performed in freely moving adult Sprague-Dawley rats with one probe within the VTA and the other within the ipsilateral nucleus accumbens (NACC). Drugs were administered into the VTA via retrograde dialysis. Dialysates from both the VTA and the NAC were collected for determination of dopamine (DA) and gamma-aminobutyric acid (GABA) by high-performance liquid chromatography with electrochemical detection. Intra-tegmental infusion of CP 93129 (20, 40, and 80 microM), a 5-HT1B receptor agonist, increased extracellular DA concentrations in a concentration-dependent manner not only in the NACC but also in the VTA, indicating increased mesolimbic DA neuron activity. Administration of CP 93129 at 80 microM into the VTA also significantly decreased extracellular GABA concentrations in this region. Co-infusion of the 5-HT1B receptor antagonist SB 216641 (10 microM), but not the 5-HT1A receptor antagonist WAY 100635 (10 microM) or the 5-HT1D/1A receptor antagonist BRL 15572 (10 microM), antagonized not only the effects of intra-tegmental CP 93129 (80 microM) on VTA DA and NAC DA but also on VTA GABA. The results suggest that activation of VTA 5-HT1B receptors increases mesolimbic DA neuron activities. The increased DA neuron activity may be associated, at least in part, with the 5-HT1B receptor-mediated inhibition of VTA GABA release.
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Affiliation(s)
- Qing-Shan Yan
- Department of Biomedical and Therapeutic Sciences, University of Illinois College of Medicine at Peoria, Peoria, IL 61656, USA.
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172
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Abstract
BACKGROUND Those with early-onset alcoholism may better respond to ondansetron (a 5-HT3 receptor antagonist) than to selective serotonin reuptake inhibitor (SSRI) treatment, whereas those with late-onset alcoholism may present the reverse response pattern. Johnson and colleagues proposed a model that attempts to explain the observed treatment response patterns of those with early and late alcoholism onset by focusing on the influence of a common genetic variant in the serotonin transporter regulatory region (5-HTTLPR) on serotonin (5-HT) and dopamine (DA) system function. METHODS The present study formalizes and extends Johnson's descriptive model into a computer simulation consisting of differential equations. For each of 16 conditions defined by genotype, drinking status, diagnostic status, and drug treatment, data were generated by 100 simulation runs. RESULTS In every condition, the S/_ genotype (S/S and S/L) had higher extracellular 5-HT levels than did the L/L genotype. The S/_ genotype also had higher rates of postsynaptic DA firing than did the L/L genotype with the exception of the SSRI treatment condition, where the firing rates were similar. Drinking generally increased levels of extracellular 5-HT, reduced rates of presynaptic 5-HT firing, and increased rates of postsynaptic DA firing. Drinking produced increases in DA activation that were greater for the L/L genotype in the SSRI treatment condition and for the S/_ genotype in the ondansetron treatment condition. CONCLUSIONS Genotype at 5-HTTLPR may influence relative reward of drinking alcohol while a person is under pharmacological treatment for alcoholism. Alternatively, 5-HTTLPR genotype may influence pathways of alcohol craving. Clinical studies should examine these hypotheses.
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Affiliation(s)
- Scott F Stoltenberg
- University of Michigan, Department of Psychiatry, Addiction Research Center, Ann Arbor 48108, USA.
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173
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Zimmer L, Riad M, Rbah L, Belkacem-Kahlouli A, Le Bars D, Renaud B, Descarries L. Toward brain imaging of serotonin 5-HT1A autoreceptor internalization. Neuroimage 2004; 22:1421-6. [PMID: 15219613 DOI: 10.1016/j.neuroimage.2004.03.020] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2004] [Revised: 03/09/2004] [Accepted: 03/11/2004] [Indexed: 11/29/2022] Open
Abstract
Enhancing cerebral serotonin (5-hydroxytryptamine, 5-HT) neurotransmission is a common property of antidepressant treatments and the basis for their efficacy. 5-HT1A receptors located on the cell body and dendrites of 5-HT neurons (autoreceptors) play a key role in this regard. Because they normally mediate an inhibition of neuronal firing, their desensitization is a prerequisite to the delayed enhancement of 5-HT neurotransmission upon treatment with monoamine oxidase (MAOI) inhibitors or specific serotonin reuptake inhibitors (SSRI). Using beta-sensitive microprobes in vivo, we measured a significant decrease (-30%) in binding sites for the 5-HT1A PET radioligand [18F]MPPF associated with an equivalent reduction (-34%) in the cell surface density of 5-HT1A receptor immunoreactivity (internalization), in the nucleus raphe dorsalis (autoreceptors), but not hippocampus (heteroreceptors), of rats given a single dose of the specific 5-HT1A receptor agonist, 8-OH-DPAT (0.5 mg/kg, iv). This effect was completely blocked by pretreatment with the selective 5-HT1A antagonist WAY 100635. Having ruled out that this decreased density of [18F]MPPF binding in the nucleus raphe dorsalis of 8-OH-DPAT-treated rats resulted from a local blood flow effect, we obtained autoradiographic evidence indicating that the total amount of specific binding of [18F]MPPF in tissue sections was unaffected by the 8-OH-DPAT treatment in either NRD or hippocampus. It was therefore concluded that the internalization of 5-HT1A autoreceptors accounted for the decreased binding in vivo of [18F]MPPF in the nucleus raphe dorsalis of rats treated with 8-OH-DPAT. Thus, PET imaging might provide a mean to measure 5-HT1A receptor internalization in human brain and thus assess responsiveness to antidepressant treatment.
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Affiliation(s)
- L Zimmer
- Laboratoire de Neuropharmacologie et Neurochimie, INSERM U512, Université Claude Bernard, Lyon, France.
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174
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Schweighofer N, Doya K, Kuroda S. Cerebellar aminergic neuromodulation: towards a functional understanding. ACTA ACUST UNITED AC 2004; 44:103-16. [PMID: 15003388 DOI: 10.1016/j.brainresrev.2003.10.004] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/14/2003] [Indexed: 11/24/2022]
Abstract
Although a number of neuromodulators influence the cerebellar circuitry, their functions remain largely unknown. By reviewing and combining results from data-driven and theory-driven studies, we attempt to provide an integrated systems view of cerebellar neuromodulation. First, we review the short- and long-term effects of neuromodulators on the cerebellar circuitry. Second, we review recent theories of the cerebellum and show that a number of modulatory signals are needed for powerful cerebellar learning and control. Finally, we attempt to match each theoretically derived modulatory signal with a specific neuromodulator. In particular, we propose that serotonin controls the 'responsibility' of each cerebellar unit (or microcomplex) in cerebellar learning and control; norepinephrine gates unsupervised learning in the cerebellar cortex; dopamine enhances goal-oriented cerebellar learning; and, finally, acetylcholine controls the speed of supervised learning in Purkinje cells.
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Affiliation(s)
- Nicolas Schweighofer
- CREST, Japan Science and Technology Agency, ATR, 2-2-2, Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan.
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175
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Graeff FG. Serotonin, the periaqueductal gray and panic. Neurosci Biobehav Rev 2004; 28:239-59. [PMID: 15225969 DOI: 10.1016/j.neubiorev.2003.12.004] [Citation(s) in RCA: 197] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2003] [Revised: 12/15/2003] [Accepted: 12/15/2003] [Indexed: 10/26/2022]
Abstract
This article reviews experimental evidence and theoretical constructs that implicate serotonin (5-HT) modulation of defensive behavior within the midbrain periaqueductal gray in panic disorder (PD). Evidence with conflict tests in experimental animals indicates that 5-HT enhances anxiety, whereas results with aversive stimulation of the dorsal periaqueductal gray point to an anxiolytic role of 5-HT. To solve this contradiction, it has been suggested that the emotional states determined by the two types of animal model are different. Conflict tests would generate conditioned anxiety, whereas periaqueductal gray stimulation would produce unconditioned fear, as evoked by proximal threat. Clinically, the former would be related to generalized anxiety while the latter to PD. Thus, 5-HT is supposed to facilitate anxiety, but to inhibit panic. This hypothesis has been tested in the animal model of anxiety and panic named the elevated T-maze, in two procedures of human experimental anxiety applied to healthy volunteers or panic patients, and in CO2-induced panic attacks. Overall, the obtained results have shown that drugs that enhance 5-HT function increase different indexes of anxiety, but decrease indexes of panic. Drugs that impair 5-HT function have the opposite effects. Thus, so far the predictions derived from the above hypothesis have been fulfilled.
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Affiliation(s)
- Frederico G Graeff
- Department of Neurology, Psychiatry and Medical Psychology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Brazil.
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176
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Bortolozzi A, Amargós-Bosch M, Toth M, Artigas F, Adell A. In vivo efflux of serotonin in the dorsal raphe nucleus of 5-HT1A receptor knockout mice. J Neurochem 2004; 88:1373-9. [PMID: 15009637 DOI: 10.1046/j.1471-4159.2003.02267.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the dorsal raphe nucleus (DR), extracellular serotonin (5-HT) regulates serotonergic transmission through 5-HT1A autoreceptors. In this work we used in vivo microdialysis to examine the effects of stressful and pharmacological challenges on DR 5-HT efflux in 5-HT1A receptor knockout (5-HT1A-/-) mice and their wild-type counterparts (5-HT1A+/+). Baseline 5-HT concentrations did not differ between both lines of mice, which is consistent with a lack of tonic control of 5-HT1A autoreceptors on DR 5-HT release. (R)-(+)-8-Hydroxy-2-(di-n-propylamino)tetralin hydrobromide (8-OH-DPAT, 0.5 mg/kg) reduced 5-HT levels to 30% of basal values in 5-HT1A+/+ mice, but not in 5-HT1A-/- mice. The selective 5-HT1B receptor agonist 1,4-dihydro-3-(1,2,3,6-tetrahydro-4-pyridinyl)-5H-pyrrolo[3,2-b]pyridin-5-one dihydrochloride (CP 93129, 300 micro m) reduced dialysate 5-HT to the same extent (30-40% of baseline) in the two genotypes, which suggests a lack of compensatory changes in 5-HT1B receptors in the DR of such mutant mice. Both a saline injection and handling for 3 min increased DR dialysate 5-HT in mutants, but not in 5-HT1A+/+ mice. Fluoxetine (5 and 20 mg/kg) elevated 5-HT in a dose-dependent manner in both genotypes. However, this effect was markedly more pronounced in the 5-HT1A-/- mice. The increased responsiveness of the extracellular 5-HT in the DR of 5-HT1A receptor knockout mice reflects a lack of the autoinhibitory control exerted by 5-HT1A autoreceptors.
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Affiliation(s)
- Analía Bortolozzi
- Department of Neurochemistry, Instituto de Investigaciones Biomédicas de Barcelona, CSIC (IDIBAPS), Barcelona, Spain
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177
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Will MJ, Der-Avakian A, Bland ST, Grahn RE, Hammack SE, Sparks PD, Pepin JL, Watkins LR, Maier SF. Electrolytic lesions and pharmacological inhibition of the dorsal raphe nucleus prevent stressor potentiation of morphine conditioned place preference in rats. Psychopharmacology (Berl) 2004; 171:191-8. [PMID: 13680080 DOI: 10.1007/s00213-003-1572-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2003] [Accepted: 06/18/2003] [Indexed: 11/26/2022]
Abstract
RATIONALE Exposure to a single session of uncontrollable inescapable shock (IS), but not to identical controllable escapable shock, produces a potentiation of morphine's rewarding properties that is unusual in that the stressor can be given a number of days before the drug administration in an environment quite different from the drug context. Many other behavioral outcomes of stressors that depend on the uncontrollability of the stressor are mediated by alterations in serotonergic (5-HT) neurons within the dorsal raphe nucleus (DRN). OBJECTIVES The present experiments examined the role of the DRN and 5-HT in mediating the effect of IS on the rewarding properties of morphine as assessed by conditioned place preference (CPP). METHODS In experiment 1, subjects received small electrolytic lesions of the DRN and were tested for morphine (3.0 mg/kg, SC) CPP after IS or control treatment. In experiment 2, subjects received an intra-DRN microinjection of the 5-HT(1A) agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 1.0 microg/0.5 microl) either before IS or before morphine (3.0 mg/kg, SC) injections during CPP testing. RESULTS IS potentiated morphine CPP in controls, but both DRN lesion and intra-DRN 8-OH-DPAT, either before IS or before morphine administration, completely blocked this effect. CONCLUSIONS These data implicate alterations in DRN 5-HT neurons in the potentiation of morphine reward produced by uncontrollable stress.
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Affiliation(s)
- Matthew J Will
- Department of Psychiatry, University of Wisconsin-Madison Medical School, Madison, WI 53719, USA
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178
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Rbah L, Leviel V, Zimmer L. Displacement of the PET ligand 18F-MPPF by the electrically evoked serotonin release in the rat hippocampus. Synapse 2003; 49:239-45. [PMID: 12827643 DOI: 10.1002/syn.10235] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The effects of the electrically evoked serotonin release were evaluated on the binding of (18)F-MPPF in the hippocampus of anesthetized rats. The specific binding of (18)F-MPPF was measured by an implanted beta-microprobe and the serotonin (5-HT) extracellular concentration was measured by microdialysis under the same conditions. Our results showed that the 10-, 20-, or 30-min electrical stimulation of the raphe nucleus elicited a significant increase in extracellular 5-HT, only detectable in the presence of a 5-HT reuptake inhibitor in the perfusate (5 microM clomipramine). Interestingly, the raphe stimulations were associated with a 27-76% reversible decrease of the (18)F-MPPF specific binding in the hippocampus, but an unchanged extracellular (18)F-MPPF collected in dialysates. Considered together, these observations suggest that (18)F-MPPF binding is sensitive to 5-HT released at a neuronal level. This compartment, explored by the beta-microprobe, is probably distinct from the extracellular compartment, explored by microdialysis.
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Affiliation(s)
- Latifa Rbah
- CERMEP Biomedical Cyclotron, 59 boulevard Pinel, F-69003 Lyon, France
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McLean DL, Sillar KT. Spinal and supraspinal functions of noradrenaline in the frog embryo: consequences for motor behaviour. J Physiol 2003; 551:575-87. [PMID: 12909679 PMCID: PMC2343235 DOI: 10.1113/jphysiol.2003.045229] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The monoamine noradrenaline (NA) can initiate and/or modulate locomotion in a variety of vertebrates. Here we report that exogenous NA application can facilitate two completely different fictive behaviours in embryos of the common frog Rana temporaria, depending on whether spinal networks are connected to supraspinal centres. When the nervous system is intact, NA elicits a non-rhythmic coiling motor response, reminiscent of a spontaneous behaviour appropriate to drive hatching movements, but has only minor effects on evoked swimming activity. After the spinal cord has been severed from the brain, spontaneous coiling is no longer observed, nor can NA elicit it, but the amine can 'release' swimming rhythm generation in response to electrical skin stimulation. The rhythm is similar, but relatively inflexible when compared to fictive swimming recorded from intact animals. Our pharmacological tests indicate that alpha 1-adrenoreceptors are involved in the permissive role of NA during spinalised rhythmic swimming and that the fictive coiling response to NA in intact animals involves descending inputs and the activation of beta 1-adrenoreceptors. Furthermore, the subtle effects of NA on evoked swimming in intact animals were mimicked by either alpha 1- or alpha 2-adrenoreceptor activation, reversibly decreasing motor burst durations and increasing their frequency. We discuss our results with reference to the known synergistic actions of NA with another aminergic neuromodulator, serotonin, and raise the possibility that these amines may actively regulate the release of one another during locomotion, in addition to their respective post-synaptic targets in the spinal cord.
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Affiliation(s)
- David L McLean
- School of Biology, Bute Medical Buildings, University of St Andrews, St Andrews, Fife KY16 9TS, Scotland, UK
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180
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Taylor BK, Basbaum AI. Systemic morphine-induced release of serotonin in the rostroventral medulla is not mimicked by morphine microinjection into the periaqueductal gray. J Neurochem 2003; 86:1129-41. [PMID: 12911621 DOI: 10.1046/j.1471-4159.2003.01907.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We used in vivo microdialysis in awake rats to test the hypothesis that intravenous morphine increases serotonin (5-HT) release within the rostral ventromedial medulla (RVM). We also injected morphine into various sites along the rostrocaudal extent of the periaqueductal gray (PAG), and examined the extent of its diffusion to the RVM. Intravenous morphine (3.0 mg/kg) produced thermal antinociception and increased RVM dialysate 5-HT, 5-hydroxyindole acetic acid (5-HIAA), and homovanillic acid (HVA) in a naloxone-reversible manner. As neither PAG microinjection of morphine (5 micro g/0.5 micro L) nor RVM administration of fentanyl or d-Ala(2),NMePhe(4),Gly-ol(5)]enkephalin (DAMGO) increased RVM 5-HT, we were unable to determine the precise site of action of morphine. Surprisingly, peak morphine levels in the RVM were higher after microinjection into the caudal PAG as compared to either intravenous injection or microinjection into more rostral sites within the PAG. Naloxone-precipitated withdrawal in morphine-tolerant rats not only increased extracellular 5-HT in the RVM, but also dopamine (DA) and HVA. We conclude that substantial amounts of morphine diffuse from the PAG to the RVM, and speculate that opioid receptor interactions at multiple brain sites mediate the analgesic effects of PAG morphine. Further studies will be required to elucidate the contribution of 5-HT and DA release in the RVM to opioid analgesia and opioid withdrawal.
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Affiliation(s)
- Bradley K Taylor
- Department of Pharmacology SL83, Health Sciences Center, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70118, USA.
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Meneses A. A pharmacological analysis of an associative learning task: 5-HT(1) to 5-HT(7) receptor subtypes function on a pavlovian/instrumental autoshaped memory. Learn Mem 2003; 10:363-72. [PMID: 14557609 PMCID: PMC218002 DOI: 10.1101/lm.60503] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Recent studies using both invertebrates and mammals have revealed that endogenous serotonin (5-hydroxytryptamine [5-HT]) modulates plasticity processes, including learning and memory. However, little is currently known about the mechanisms, loci, or time window of the actions of 5-HT. The aim of this review is to discuss some recent results on the effects of systemic administration of selective agonists and antagonists of 5-HT on associative learning in a Pavlovian/instrumental autoshaping (P/I-A) task in rats. The results indicate that pharmacological manipulation of 5-HT1-7 receptors or 5-HT reuptake sites might modulate memory consolidation, which is consistent with the emerging notion that 5-HT plays a key role in memory formation.
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Affiliation(s)
- Alfredo Meneses
- Depto De Farmacobiología, CINVESTAV-IPN, México City 14330, México.
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182
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Abstract
Fear is an adaptive component of the acute "stress" response to potentially-dangerous (external and internal) stimuli which threaten to perturb homeostasis. However, when disproportional in intensity, chronic and/or irreversible, or not associated with any genuine risk, it may be symptomatic of a debilitating anxious state: for example, social phobia, panic attacks or generalized anxiety disorder. In view of the importance of guaranteeing an appropriate emotional response to aversive events, it is not surprising that a diversity of mechanisms are involved in the induction and inhibition of anxious states. Apart from conventional neurotransmitters, such as monoamines, gamma-amino-butyric acid (GABA) and glutamate, many other modulators have been implicated, including: adenosine, cannabinoids, numerous neuropeptides, hormones, neurotrophins, cytokines and several cellular mediators. Accordingly, though benzodiazepines (which reinforce transmission at GABA(A) receptors), serotonin (5-HT)(1A) receptor agonists and 5-HT reuptake inhibitors are currently the principle drugs employed in the management of anxiety disorders, there is considerable scope for the development of alternative therapies. In addition to cellular, anatomical and neurochemical strategies, behavioral models are indispensable for the characterization of anxious states and their modulation. Amongst diverse paradigms, conflict procedures--in which subjects experience opposing impulses of desire and fear--are of especial conceptual and therapeutic pertinence. For example, in the Vogel Conflict Test (VCT), the ability of drugs to release punishment-suppressed drinking behavior is evaluated. In reviewing the neurobiology of anxious states, the present article focuses in particular upon: the multifarious and complex roles of individual modulators, often as a function of the specific receptor type and neuronal substrate involved in their actions; novel targets for the management of anxiety disorders; the influence of neurotransmitters and other agents upon performance in the VCT; data acquired from complementary pharmacological and genetic strategies and, finally, several open questions likely to orientate future experimental- and clinical-research. In view of the recent proliferation of mechanisms implicated in the pathogenesis, modulation and, potentially, treatment of anxiety disorders, this is an opportune moment to survey their functional and pathophysiological significance, and to assess their influence upon performance in the VCT and other models of potential anxiolytic properties.
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Affiliation(s)
- Mark J Millan
- Psychopharmacology Department, Centre de Rescherches de Croissy, Institut de Recherches (IDR) Servier, 125 Chemin de Ronde, 78290 Croissy-sur-Seine, Paris, France.
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