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Kalinichenko L, Kornhuber J, Sinning S, Haase J, Müller CP. Serotonin Signaling through Lipid Membranes. ACS Chem Neurosci 2024; 15:1298-1320. [PMID: 38499042 PMCID: PMC10995955 DOI: 10.1021/acschemneuro.3c00823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 02/22/2024] [Accepted: 02/27/2024] [Indexed: 03/20/2024] Open
Abstract
Serotonin (5-HT) is a vital modulatory neurotransmitter responsible for regulating most behaviors in the brain. An inefficient 5-HT synaptic function is often linked to various mental disorders. Primarily, membrane proteins controlling the expression and activity of 5-HT synthesis, storage, release, receptor activation, and inactivation are critical to 5-HT signaling in synaptic and extra-synaptic sites. Moreover, these signals represent information transmission across membranes. Although the lipid membrane environment is often viewed as fairly stable, emerging research suggests significant functional lipid-protein interactions with many synaptic 5-HT proteins. These protein-lipid interactions extend to almost all the primary lipid classes that form the plasma membrane. Collectively, these lipid classes and lipid-protein interactions affect 5-HT synaptic efficacy at the synapse. The highly dynamic lipid composition of synaptic membranes suggests that these lipids and their interactions with proteins may contribute to the plasticity of the 5-HT synapse. Therefore, this broader protein-lipid model of the 5-HT synapse necessitates a reconsideration of 5-HT's role in various associated mental disorders.
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Affiliation(s)
- Liubov
S. Kalinichenko
- Department
of Psychiatry and Psychotherapy, University
Clinic, Friedrich-Alexander-University of Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany
| | - Johannes Kornhuber
- Department
of Psychiatry and Psychotherapy, University
Clinic, Friedrich-Alexander-University of Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany
| | - Steffen Sinning
- Department
of Forensic Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Jana Haase
- School
of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Christian P. Müller
- Department
of Psychiatry and Psychotherapy, University
Clinic, Friedrich-Alexander-University of Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany
- Institute
of Psychopharmacology, Central Institute of Mental Health, Medical
Faculty Mannheim, Heidelberg University, 69047, Mannheim, Germany
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Ahumada LH, Morato S, Lamprea MR. Acute stress increases behaviors that optimize safety and decreases the exploration of aversive areas. LEARNING AND MOTIVATION 2022. [DOI: 10.1016/j.lmot.2022.101855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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3
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Müller CP. Serotonin and Consciousness-A Reappraisal. Behav Brain Res 2022; 432:113970. [PMID: 35716774 DOI: 10.1016/j.bbr.2022.113970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 06/01/2022] [Accepted: 06/06/2022] [Indexed: 11/02/2022]
Abstract
The serotonergic system of the brain is a major modulator of behaviour. Here we describe a re-appraisal of its function for consciousness based on anatomical, functional and pharmacological data. For a better understanding, the current model of consciousness is expanded. Two parallel streams of conscious flow are distinguished. A flow of conscious content and an affective consciousness flow. While conscious content flow has its functional equivalent in the activity of higher cortico-cortical and cortico-thalamic networks, affective conscious flow originates in segregated deeper brain structures for single emotions. It is hypothesized that single emotional networks converge on serotonergic and other modulatory transmitter neurons in the brainstem where a bound percept of an affective conscious flow is formed. This is then dispersed to cortical and thalamic networks, where it is time locked with conscious content flow at the level of these networks. Serotonin acts in concert with other modulatory systems of the brain stem with some possible specialization on single emotions. Together, these systems signal a bound percept of affective conscious flow. Dysfunctions in the serotonergic system may not only give rise to behavioural and somatic symptoms, but also essentially affect the coupling of conscious affective flow with conscious content flow, leading to the affect-stained subjective side of mental disorders like anxiety, depression, or schizophrenia. The present model is an attempt to integrate the growing insights into serotonergic system function. However, it is acknowledged, that several key claims are still at a heuristic level that need further empirical support.
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Affiliation(s)
- Christian P Müller
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany; Centre for Drug Research, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia.
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Both serotonergic and noradrenergic systems modulate the development of tolerance to chronic stress in rats with lesions of the serotonergic neurons of the median raphe nucleus. Behav Brain Res 2017; 357-358:39-47. [PMID: 28662893 DOI: 10.1016/j.bbr.2017.06.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 05/23/2017] [Accepted: 06/24/2017] [Indexed: 11/20/2022]
Abstract
Acute exposure to stress induces significant behavioural changes, while repeated exposure to the same stressor leads to the development of tolerance to stress. The development of tolerance appears to involve the serotonergic projections from the Median Raphe Nucleus (MnRN) to the dorsal Hippocampus (dH), since rats with lesions of this pathway does not develop tolerance to stress. Previous data from our laboratory showed that treatment with imipramine, a serotonin (5-HT) and noradrenaline (NA) reuptake inhibitor, lead to the development of tolerance. However, it remains to be elucidated whether such tolerance involves the participation of the noradrenergic system, apart from the serotonergic projections. Therefore, the aim of this work was to investigate the behavioural and neurochemical effects of chronic treatment with desipramine (NA reuptake inhibitor) or fluoxetine (5-HT reuptake inhibitor) in chronically stressed rats with lesions of the serotonergic neurons of the MnRN. Male Wistar rats with or without lesion in the MnRN were submitted or not to acute (2 h) or chronic restraint (2 h/seven days) stress and tested in the elevated pus maze (EPM). Treatment with fluoxetine, desipramine (10 mg/kg) or saline was performed twice daily (12-12 h interval), for 7 consecutive days. EPM test was conducted 24 h after the treatment. Fluoxetine attenuated the anxiogenic-induced effect of lesion in chronically restrained rats, without changing serotonin and noradrenaline levels in the hippocampus of lesioned rats. A similar profile was also observed after treatment with desipramine. These results suggest that both the serotonergic and the noradrenergic systems are involved in the development of tolerance to chronic stress. Additionally, the integrity of the serotonergic pathway of the MnRN-dH is not essential for the anxiolytic-like effects of these drugs.
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5
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Silva K, Carvalho M, Padovan C. Tolerance to repeated stress in rats with lesions of the serotoninergic neurons of the Median Raphe Nucleus and chronically treated with imipramine. Behav Brain Res 2016; 302:220-7. [DOI: 10.1016/j.bbr.2016.01.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 01/07/2016] [Accepted: 01/09/2016] [Indexed: 01/08/2023]
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6
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Almeida PVG, Trovo MC, Tokumoto AM, Pereira AC, Padovan CM. Role of serotonin 1A receptors in the median raphe nucleus on the behavioral consequences of forced swim stress. J Psychopharmacol 2013; 27:1134-40. [PMID: 24162801 DOI: 10.1177/0269881113508829] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Despite the intense research on the neurobiology of stress, the role of serotonin (5-HT)1A receptors still remains to be elucidated. In the hippocampus, post-synaptic 5-HT1A receptors activation induces anxiolytic effects in animals previously exposed to stressful situations. However, little is known about somatodendritic 5-HT1A receptors in the median raphe nucleus (MRN). Therefore, the aim of this study was to investigate the role of 5-HT1A receptors located in the MRN in rats exposed to forced swim stress. After recovering from surgery, rats were forced to swim for 15 min in a cylinder. Intra-MRN injections of saline, 8-OH-DPAT (3 nmol/0.2 µL) and/or WAY-100635 (0.3 nmol/0.2 µL) were performed immediately before or after pre-exposure or 24 h later (immediately before test). Non-stressed rats received the same treatment 24 h or 10 min before test. Our data showed that 8-OH-DPAT increased latency to display immobility while decreasing time spent immobile in almost all experimental conditions. These effects were not prevented by previous treatment with WAY-100635. No effects of different treatments were described in non-stressed animals. Taken together, our data suggest that in addition to activation of 5-HT1A, 5-HT7 receptors may also be involved in the behavioural consequences of exposure to swim stress.
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Affiliation(s)
- P V G Almeida
- 1Departamento de Psicologia da Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brasil
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7
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Haleem DJ, Samad N, Perveen T, Haider S, Haleem MA. ROLE OF SEROTONIN-1A RECEPTORS IN RESTRAINT-INDUCED BEHAVIORAL DEFICITS AND ADAPTATION TO REPEATED RESTRAINT STRESS IN RATS. Int J Neurosci 2009; 117:243-57. [PMID: 17365111 DOI: 10.1080/00207450500534084] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), a selective 5-hydroxy-tryptamine (5-HT; serotonin)-1A agonist was used to evaluate the role 5-HT-1 A receptors in restraint-induced behavioral deficits and adaptation to repeated restraint stress in rats. Animals were injected with 8-OH-DPAT at a dose of 0.25 mg/kg 1 h before exposing to an episode of 2 h/day restraint stress daily for 5 days. Effects of drug administration and restraint stress on 24 h cumulative food intakes were monitored daily. Intensity of 8-OH-DPAT-induced serotonin syndrome was also monitored each day before submitting animals to the episode of stress. Exposure to the first episode of 2 h restraint stress resulted in a decrease in 24 h cumulative food intake and an attenuation of 8-OH-DPAT-induced serotonin syndrome monitored next day. The deficits attenuated following 2nd and 3rd 2 h/day restraint were not observed following the 4th and 5th 2 h/day restraint. The decreases of food intake following 1st and 2nd day restraint sessions were smaller in 8-OH-DPAT than saline-injected animals. Administration of 8-OH-DPAT on day 6 elicited comparable serotonin syndrome in unrestrained and repeatedly restrained groups. Brain 5-HT metabolism decreased in unrestrained but not repeatedly restrained animals. The results suggest that a decrease in serotonergic neurotransmission is involved in restraint-induced behavioral deficits while a normalization of serotonin neurotransmission due to desensitization of somatodendritic 5-HT-1A receptors may help cope with the stress demand to produce adaptation to stress.
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Affiliation(s)
- Darakhshan J Haleem
- Department of Biochemistry, Neurochemistry and Biochemical Neuropharmacology, Research Laboratory, University of Karachi, Karachi, Pakistan.
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Carvalho MC, Masson S, Brandão ML, de Souza Silva MA. Anxiolytic-like effects of substance P administration into the dorsal, but not ventral, hippocampus and its influence on serotonin. Peptides 2008; 29:1191-200. [PMID: 18490080 DOI: 10.1016/j.peptides.2008.02.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Revised: 02/18/2008] [Accepted: 02/20/2008] [Indexed: 10/22/2022]
Abstract
Substance P (SP) is known to be involved in processes related to learning and memory, fear, anxiety and stress. SP and NK1 receptors are localized in the hippocampus, a brain structure involved in learning and memory as well as emotional processes. As there is evidence for differential functions of the ventral (VH) and dorsal (DH) hippocampus in a variety of behaviors, we here evaluated the effects of injections of SP into the VH and DH in rats submitted to the elevated plus-maze (EPM) and open field (OF) tests. The results obtained showed that infusions of 100 and 1000 ng of SP into the DH, but not VH, increased open arm activity in the EPM and in the central zone of the OF, indicative of anxiolytic-like action. These effects were observed in the absence of significant changes in general motor activity. In an additional experiment to examine whether these effects of SP are mediated by local serotoninergic mechanisms, extracellular concentrations of this monoamine were assessed by use of in vivo microdialysis. Infusions of SP into the DH did not influence the extracellular concentration of serotonin. These data indicate that neurokinins in the DH, but not VH, are involved in mechanisms associated with anxiety and that the mediation of SP in anxiety-related behaviors is independent of local serotonergic mechanisms.
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Affiliation(s)
- M C Carvalho
- Instituto de Neurociências e Comportamento (INeC), Campus USP, 14040-901 Ribeirão Preto, SP, Brazil
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Joca SRL, Ferreira FR, Guimarães FS. Modulation of stress consequences by hippocampal monoaminergic, glutamatergic and nitrergic neurotransmitter systems. Stress 2007; 10:227-49. [PMID: 17613938 DOI: 10.1080/10253890701223130] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Several findings relate the hippocampal formation to the behavioural consequences of stress. It contains a high concentration of corticoid receptors and undergoes plastic modifications, including decreased neurogenesis and cellular remodelling, following stress exposure. Various major neurotransmitter systems in the hippocampus are involved in these effects. Serotonin (5-HT) seems to exert a protective role in the hippocampus and attenuates the behavioural consequences of stress by activating 5-HT1A receptors in this structure. These effects may mediate the therapeutic actions of several antidepressants. The role of noradrenaline is less clear and possibly depends on the specific hippocampal region (dorsal vs. ventral). The deleterious modifications induced in the hippocampus by stress might involve a decrease in neurotrophic factors such as brain derived neurotrophic factor (BDNF) following glutamate N-methyl-D-aspartate (NMDA) receptor activation. In addition to glutamate, nitric oxide (NO) could also be related to these effects. Systemic and intra-hippocampal administration of nitric oxide synthase (NOS) inhibitors attenuates stress-induced behavioural consequences. The challenge for the future will be to integrate results related to these different neurotransmitter systems in a unifying theory about the role of the hippocampus in mood regulation, depressive disorder and antidepressant effects.
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Affiliation(s)
- Sâmia Regiane Lourenço Joca
- Department of Pharmacology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
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Hsu HR, Chen TY, Chan MH, Chen HH. Acute effects of nicotine on restraint stress-induced anxiety-like behavior, c-Fos expression, and corticosterone release in mice. Eur J Pharmacol 2007; 566:124-31. [PMID: 17459372 DOI: 10.1016/j.ejphar.2007.03.040] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Revised: 03/14/2007] [Accepted: 03/19/2007] [Indexed: 10/23/2022]
Abstract
Clinical evidence suggests that nicotine reduces anxiety in stressful situations. In the present study, we investigated the effect of nicotine on restraint-enhanced anxiety-like behavior, c-Fos expression, an index of neuronal activation in the brain, and plasma corticosterone. Two-hour restraint stress-enhanced anxiety-like behavior in the elevated plus-maze (EPM) and nicotine hydrogen tartrate (0.25 mg/kg, i.p.) attenuated the stress-induced changes. Pretreatment with the centrally acting nicotinic antagonist, mecamylamine (2 mg/kg), blocked nicotine's effects. In addition, restraint led to significant increases of c-Fos expression in several brain regions related to stress or anxiety including paraventricular hypothalamic nucleus (PVN), lateral hypothalamic area (LH), central amygdaloid nucleus (CeA), medial amygdaloid nucleus (MeA) and cingulate and retrosplenial cortices (Cg/RS), paraventricular thalamic nucleus (PVT), and basolateral amygdaloid nucleus (BLA). Nicotine attenuated the restraint-induced expression of c-Fos in the PVN, LH, CeA, MeA, and Cg/RS, while leaving the BLA and PVT unaffected. In contrast, nicotine did not reverse the increased levels of plasma corticosterone induced by restraint. These findings suggest that nicotine may modify the stress-induced behavioral changes via regulating the neuronal activation in selected brain regions rather than affecting hypothalamo-pituitary-adrenocortical axis hormone responses.
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Affiliation(s)
- Hui-Ru Hsu
- Institute of Pharmacology and Toxicology, Tzu Chi University, Hualien, Taiwan
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11
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Müller CP, Carey RJ, Huston JP, De Souza Silva MA. Serotonin and psychostimulant addiction: Focus on 5-HT1A-receptors. Prog Neurobiol 2007; 81:133-78. [PMID: 17316955 DOI: 10.1016/j.pneurobio.2007.01.001] [Citation(s) in RCA: 239] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2006] [Revised: 12/04/2006] [Accepted: 01/03/2007] [Indexed: 01/03/2023]
Abstract
Serotonin(1A)-receptors (5-HT(1A)-Rs) are important components of the 5-HT system in the brain. As somatodendritic autoreceptors they control the activity of 5-HT neurons, and, as postsynaptic receptors, the activity in terminal areas. Cocaine (COC), amphetamine (AMPH), methamphetamine (METH) and 3,4-methylenedioxymethamphetamine ("Ecstasy", MDMA) are psychostimulant drugs that can lead to addiction-related behavior in humans and in animals. At the neurochemical level, these psychostimulant drugs interact with monoamine transporters and increase extracellular 5-HT, dopamine and noradrenalin activity in the brain. The increase in 5-HT, which, in addition to dopamine, is a core mechanism of action for drug addiction, hyperactivates 5-HT(1A)-Rs. Here, we first review the role of the various 5-HT(1A)-R populations in spontaneous behavior to provide a background to elucidate the contribution of the 5-HT(1A)-Rs to the organization of psychostimulant-induced addiction behavior. The progress achieved in this field shows the fundamental contribution of brain 5-HT(1A)-Rs to virtually all behaviors associated with psychostimulant addiction. Importantly, the contribution of pre- and postsynaptic 5-HT(1A)-Rs can be dissociated and frequently act in opposite directions. We conclude that 5-HT(1A)-autoreceptors mainly facilitate psychostimulant addiction-related behaviors by a limitation of the 5-HT response in terminal areas. Postsynaptic 5-HT(1A)-Rs, in contrast, predominantly inhibit the expression of various addiction-related behaviors directly. In addition, they may also influence the local 5-HT response by feedback mechanisms. The reviewed findings do not only show a crucial role of 5-HT(1A)-Rs in the control of brain 5-HT activity and spontaneous behavior, but also their complex role in the regulation of the psychostimulant-induced 5-HT response and subsequent addiction-related behaviors.
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Affiliation(s)
- Christian P Müller
- Institute of Physiological Psychology I, University of Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany.
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. NS, . TP, . SH, . DJH. Attenuation of Restraint-induced Anorexia and Anxiogenic Behavior by Serotonin-1A Agonists in Rats. JOURNAL OF MEDICAL SCIENCES 2005. [DOI: 10.3923/jms.2005.289.293] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Françolin-Silva AL, Almeida SS. The interaction of housing condition and acute immobilization stress on the elevated plus-maze behaviors of protein-malnourished rats. Braz J Med Biol Res 2004; 37:1035-42. [PMID: 15264011 DOI: 10.1590/s0100-879x2004000700013] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Protein malnutrition induces structural, neurochemical and functional alterations in the central nervous system, leading to behavioral alterations. In the present study, we used the elevated plus-maze (EPM) as a measure of anxiety to evaluate the interaction between acute immobilization and housing conditions on the behavior of malnourished rats. Pups (6 males and 2 females) were fed by Wistar lactating dams receiving a 6% (undernourished) or 16% (well-nourished) protein diet. After weaning, the animals continued to receive the same diets ad libitum until 49 days of age when they started to receive a regular lab chow diet. From weaning to the end of the tests on day 70, the animals were housed under two different conditions, i.e., individual or in groups of three. On the 69th day, half of the animals were submitted to immobilization for 2 h, while the other half were undisturbed, and both groups were tested 24 h later for 5 min in the EPM. Independent of other factors, protein malnutrition increased, while immobilization and social isolation per se decreased, EPM exploration. Analysis of the interaction of diet vs immobilization vs housing conditions showed that the increased EPM exploration presented by the malnourished group was reversed by acute immobilization in animals reared in groups but not in animals reared individually. The interaction between immobilization and housing conditions suggests that living for a long time in social isolation is sufficiently stressful to reduce the responses to another anxiogenic procedure (immobilization), while living in groups prompts the animals to react to acute stress. Thus, it is suggested that housing condition can modulate the effects of an anxiogenic procedure on behavioral responses of malnourished rats in the EPM.
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Affiliation(s)
- A L Françolin-Silva
- Laboratório de Nutrição e Comportamento, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
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Andrade CS, Guimarães FS. Anxiolytic-like effect of group housing on stress-induced behavior in rats. Depress Anxiety 2004; 18:149-52. [PMID: 14625880 DOI: 10.1002/da.10124] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Social support is proposed to attenuate behavioral consequences of exposure to uncontrollable stressors. To test this possibility, we compared the effects of two post-stress housing conditions, in pairs or in groups of 10-12 animals per cage, on the behavior of rats tested in the elevated plus-maze (EPM) 24 hr after stress. We also included positive control groups to compare the effects of a standard anxiolytic, diazepam, with those of vehicle. Confirming previous results, diazepam increased the percentage of entries and time spent in the open arms (vehicle, % open entries: 37.0+/-2.7, % time spent in open arms: 17.6+/-1.9; diazepam, % open entries: 46.7+/-2.7, % time spent in open arms: 39.1+/-3.9). Group housing after restraint significantly prevented the anxiogenic effect of restraint (group housing, % open entries: 32.0+/-5.2, % time spent in open arms: 17.6+/-5.0; pair housing, % open entries: 18.7+/-2.2, % time spent in open arms: 6.5+/-1.0). These results suggest that housing conditions could be an important factor in the development of behavioral consequences of stress exposure.
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Padovan CM, Guimarães FS. Antidepressant-like effects of NMDA-receptor antagonist injected into the dorsal hippocampus of rats. Pharmacol Biochem Behav 2004; 77:15-9. [PMID: 14724037 DOI: 10.1016/j.pbb.2003.09.015] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Exposure to uncontrollable stressors causes behavioral changes that have been related to depressive states in humans. Poststress intrahippocampal administration of amino-7-phosphonoheptanoic acid (AP-7), a glutamate NMDA-receptor antagonist, attenuated the restraint-induced decreased exploration of an elevated plus maze 24 h later. The objective of the study was to test if this treatment would also attenuate the increased immobility seem in the forced swim test (FST) due to preexposition to this stressful situation. Male Wistar rats with cannulae aimed at the dorsal hippocampus were submitted to 15 min of forced swimming and tested 24 h later. They received bilateral intrahippocampal injections of AP-7 (10 nmol) either before or after the pretest swimming session or before the test. Poststress treatment increased latency to display the first episode of immobility and tended to reduce total immobility time. The drug was ineffective when given before stress or before test and in nonstressed animals. This suggests that glutamate NMDA receptors located in the dorsal hippocampus are involved in the behavioral changes observed in the FST.
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Affiliation(s)
- C M Padovan
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14049-900, SP, Ribeirão Prêto, Brazil
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Deakin JFW. Depression and antisocial personality disorder: two contrasting disorders of 5HT function. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 2003:79-93. [PMID: 12830930 DOI: 10.1007/978-3-7091-6020-6_5] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Impaired 5HT functioning has been implicated in two very different psychiatric syndromes: antisocial personality disorder and depression. In both, reduced csf concentration of 5HIAA and blunted circulating hormone responses to 5HT drug challenge have been described. The paradox can be resolved by the theory that the two main ascending 5HT pathways mediate adaptive responses to future and current adversity. Projections of the anterior group of raphe 5HT cells (dorsal raphe nucleus) oppose the action of dopamine and mediate avoidance of threats. Impaired function sensitises the dopamine system resulting in impulsivity and drug addiction. Posterior 5HT cells (median raphe nucleus) innervate hippocampus and cingulate gyrus and suppress memory and awareness of current and past adversity. Impaired function results in low mood, low self-esteem, hopelessness and pessimism. Modern imaging methods are providing startling corroboration of these ideas.
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Affiliation(s)
- J F W Deakin
- Neuroscience and Psychiatry Unit, University of Manchester, United Kingdom.
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Joca SRL, Padovan CM, Guimarães FS. Activation of post-synaptic 5-HT(1A) receptors in the dorsal hippocampus prevents learned helplessness development. Brain Res 2003; 978:177-84. [PMID: 12834912 DOI: 10.1016/s0006-8993(03)02943-3] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Activation of post-synaptic 5-HT(1A) receptors in the dorsal hippocampus is proposed to mediate stress adaptation. Chronic social stress and high corticosteroid levels would impair this coping mechanism, predisposing animals to learned helplessness. To test the hypothesis that increasing serotonin levels in the dorsal hippocampus would attenuate the development of learned helplessness, rats received inescapable foot-shock (pre-test session) and were tested in a shuttle box 24-h later. Pre-stressed animals showed impairment of escape responses. This effect was prevented by chronic (21 days) treatment with imipramine (15 mg/kg). Similar results were obtained when the animals received bilateral intra-hippocampal injections, immediately after pre-test, of zimelidine (100 nmol/0.5 microl), a serotonin reuptake blocker, or 8-OH-DPAT (10 nmol), a 5-HT(1A) receptor agonist. The zimelidine effect was prevented by pre-treatment with WAY-100635 (30 nmol), a 5-HT(1A) receptor antagonist. These data suggest that facilitation of serotonergic neurotransmission in the dorsal hippocampus mediates adaptation to severe inescapable stress, probably through the activation of post-synaptic 5-HT(1A) receptors.
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Affiliation(s)
- Sâmia Regiane Lourenço Joca
- Department of Pharmacology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Av Bandeirantes 3900, 14049-900, Ribeirão Preto, SP, Brazil
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Klenerová V, Jurcovicová J, Kaminský O, Sída P, Krejcí I, Hlinák Z, Hynie S. Combined restraint and cold stress in rats: effects on memory processing in passive avoidance task and on plasma levels of ACTH and corticosterone. Behav Brain Res 2003; 142:143-9. [PMID: 12798275 DOI: 10.1016/s0166-4328(02)00401-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effect of restraint stress combined with water immersion (IMO+C), applied at various intervals before and after the acquisition of a passive avoidance task, was studied in rats. The procedure started with two pre-training trials. On the single training trial the rats received a footshock (0.3 mA, 3s) after they entered the preferred dark compartment. The exposure to IMO+C lasting 1 h terminated 4 or 1 h before application of the footshock or started immediately or 3 h after this aversive stimulus. Retention tests were performed 1 and 2 days after the acquisition trial. In an attempt to relate the behavioural responses to the stressor with plasma levels of two stress hormones we measured ACTH and corticosterone under similar conditions as were used in the behavioural experiments. IMO+C exposure terminating 1 h before the training resulted in very short avoidance latencies during retention testing. A similar impairment of retention test performance was found in animals exposed to the stressor immediately after training. When IMO+C exposure terminated 4 h before training the stressed rats exhibited comparably long avoidance latencies as shown by the controls. IMO+C presented 3 h after acquisition trial also did not influence retention of avoidance learning. The hormones were estimated 1 and 4 h after IMO+C, both in the absence and presence of footshock. Both ACTH and corticosterone were significantly increased 1 h after IMO+C termination, and their plasma levels returned to control values within 4 h. Footshock alone increased plasma corticosterone, however, the hormone levels were significantly lower than those estimated after IMO+C terminating 1 h before blood collection. Footshock substantially increased ACTH levels in rats exposed to IMO+C 1 h before footshock, but not in stressed rats with already high levels of corticosterone. In conclusion, IMO+C represents a strong stress stimulus exerting amnesic effect when applied shortly before or after the acquisition trial. Further, the findings indicate the restraint and cold stressor to interfere with consolidation of passive avoidance response. We suggest that the moderate circulating levels of corticosterone found after footshock may be positively related to the memory consolidation, while the exceedingly high levels have an opposite effect.
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Affiliation(s)
- Vera Klenerová
- 1st Medical Faculty, Institute of Pharmacology, Charles University in Prague, Albertov 4, 128 00 Prague 2, Czech Republic.
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Netto SM, Silveira R, Coimbra NC, Joca SRL, Guimarães FS. Anxiogenic effect of median raphe nucleus lesion in stressed rats. Prog Neuropsychopharmacol Biol Psychiatry 2002; 26:1135-41. [PMID: 12452536 DOI: 10.1016/s0278-5846(02)00248-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Serotonin (5-HT) neurons located in the median raphe nucleus (MRN) may have a role in the development of behavioral changes to stress. The objective of the present work was to investigate the effects of a selective lesion of 5-HT neurons located in the MRN in previously stressed male Wistar rats submitted to the elevated plus maze (EPM). In an initial experiment, the animals (n=20-22) were submitted to one (acute) or seven (chronic) daily restraint stress periods (2 h) and tested in the EPM 24 h later. Results showed that acute restraint caused a significant decrease in the number of entries into the open arms, as compared to nonstressed controls. This effect disappeared when the animals were submitted to chronic restraint. In the next set of experiments, animals (n=6-8) received, 1 week before the behavioral studies, intra-MRN injection of 5,7-dihydroxytryptamine (5,7-DHT; 8 microg/1 microl). Neurochemical analysis showed that this treatment significantly decreases 5-HT and 5-hydroxy-indoleacetic acid (5-HIAA) levels in the hippocampus, but not in the striatum. No difference between lesioned and sham-operated animals in EPM performance was found in nonstressed animals or in those submitted to acute restraint. In chronically restrained animals, however, lesioned rats showed a significant decrease in the number of entries and time spent in the open arms. These results suggest that lesions of 5-HT neurons located in the MRN cause anxiogenic-like behavior in animals that have been chronically restrained.
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Affiliation(s)
- Sueli Mendonça Netto
- Faculdade de Filosofia, Laboratório de Psicobiologia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14049-900, Ribeirdo Preto, SP, Brazil
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20
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Carey RJ, De Palma G, Damianopoulos E. 5-HT1A agonist/antagonist modification of cocaine stimulant effects: implications for cocaine mechanisms. Behav Brain Res 2002; 132:37-46. [PMID: 11853856 DOI: 10.1016/s0166-4328(01)00383-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The 5-HT1A receptor site has been demonstrated to be an important pharmacological target in the modulation of unconditioned behavioral effects induced by cocaine. In this study, separate groups of rats (n=7) received a series of the 5-HT1A agonist treatments, 8-OHDPAT (0.2,0.4 mg/kg) in combination with saline or cocaine (10 mg/kg). Using a crossover design, the treatments were subsequently switched to the 5-HT1A antagonist, WAY 100635 (0.4,0.8 mg/kg) and then, switched back again to 8-OHDPAT (0.2,0.4 mg/kg). When the 8-OHDPAT was given in combination with cocaine, locomotion was substantially enhanced but when the treatment was switched to WAY 100635, the cocaine induced locomotion was suppressed. Neither the 8-OHDPAT or WAY 100635 given with saline affected locomotion as compared to saline treated animals. These findings indicated a reciprocal facilitatory/inhibitory influence of 5-HT1A agonists/antagonists upon cocaine induced locomotion. The 8-OHDPAT treatments, however, did not enhance all cocaine behavioral responses. Initially, 8-OHDPAT suppressed cocaine induced rearing and central zone entry, but with repeated treatments, these response suppression effects subsided. As a consequence, the facilitative influence of 8-OHDPAT upon cocaine induced locomotion could not be attributed to response redistribution effects. While WAY 100635 markedly reduced cocaine induced locomotion and rearing to nearly saline response levels, the same WAY 100635 treatments did not modify locomotor stimulant effects induced by caffeine (10 mg/kg). In that caffeine stimulant effects are not directly linked to serotonergic mechanisms, the absence of an influence of WAY 100635 upon caffeine induced locomotor stimulation lent further support to the proposition that the 5-HT1A receptor site contributes to locomotor behavior in situations where the serotonergic system is pharmacologically activated by drugs such as cocaine. These findings point to a potential role for 5-HT1A antagonists in treatment of cocaine abuse.
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Affiliation(s)
- Robert J Carey
- VA Medical Center and SUNY Health Science Center, Research and Development 800 Irving Avenue, Syracuse, NY 13210, USA.
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21
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Nunes-de-Souza RL, Canto-de-Souza A, Rodgers RJ. Effects of intra-hippocampal infusion of WAY-100635 on plus-maze behavior in mice. Influence of site of injection and prior test experience. Brain Res 2002; 927:87-96. [PMID: 11814435 DOI: 10.1016/s0006-8993(01)03335-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The positive profile of systemically-administered 5-HT(1A) receptor antagonists in several rodent models of anxiolytic activity suggests an important role for postsynaptic 5-HT(1A) receptor mechanisms in anxiety. To test this hypothesis, we investigated the effects of WAY-100635 microinfusions (0, 0.1, 1.0 or 3.0 microg in 0.2 microl) into the dorsal (DH) or ventral (VH) hippocampus on behaviours displayed by male Swiss-Webster mice in the elevated plus-maze. As prior experience is known to modify pharmacological responses in this test, the effects of intra-hippocampal infusions were examined both in maze-naïve and maze-experienced subjects. Test videotapes were scored for conventional indices of anxiety (% open arm entries/time) and locomotor activity (closed arm entries), as well as a range of ethological measures (e.g. risk assessment). In maze-naïve mice, intra-VH (but not intra-DH) infusions of WAY-100635 (3.0 microg but not lower doses) increased open arm exploration and reduced risk assessment. These effects were observed in the absence of significant changes in locomotor activity. In contrast, neither intra-VH nor intra-DH infusions of WAY-100635 altered the behaviour of maze-experienced mice. These findings suggest that postsynaptic 5-HT(1A) receptors in the ventral (but not dorsal) hippocampus play a significant role both in the mediation of plus-maze anxiety in mice and in experientially-induced alterations in responses to this test.
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22
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Blanchard C, Blanchard R, Fellous JM, Guimarães FS, Irwin W, Ledoux JE, McGaugh JL, Rosen JB, Schenberg LC, Volchan E, Da Cunha C. The brain decade in debate: III. Neurobiology of emotion. Braz J Med Biol Res 2001; 34:283-93. [PMID: 11262578 DOI: 10.1590/s0100-879x2001000300001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This article is a transcription of an electronic symposium in which active researchers were invited by the Brazilian Society of Neuroscience and Behavior (SBNeC) to discuss the advances of the last decade in the neurobiology of emotion. Four basic questions were debated: 1) What are the most critical issues/questions in the neurobiology of emotion? 2) What do we know for certain about brain processes involved in emotion and what is controversial? 3) What kinds of research are needed to resolve these controversial issues? 4) What is the relationship between learning, memory and emotion? The focus was on the existence of different neural systems for different emotions and the nature of the neural coding for the emotional states. Is emotion the result of the interaction of different brain regions such as the amygdala, the nucleus accumbens, or the periaqueductal gray matter or is it an emergent property of the whole brain neural network? The relationship between unlearned and learned emotions was also discussed. Are the circuits of the former the underpinnings of the latter? It was pointed out that much of what we know about emotions refers to aversively motivated behaviors, like fear and anxiety. Appetitive emotions should attract much interest in the future. The learning and memory relationship with emotions was also discussed in terms of conditioned and unconditioned stimuli, innate and learned fear, contextual cues inducing emotional states, implicit memory and the property of using this term for animal memories. In a general way it could be said that learning modifies the neural circuits through which emotional responses are expressed.
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Affiliation(s)
- C Blanchard
- Department of Neurobiology, University of Hawaii, Honolulu, HI, USA
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Irvine EE, Cheeta S, File SE. Tolerance to nicotine's effects in the elevated plus-maze and increased anxiety during withdrawal. Pharmacol Biochem Behav 2001; 68:319-25. [PMID: 11267637 DOI: 10.1016/s0091-3057(00)00449-4] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In the elevated plus-maze test of anxiety, nicotine (0.1 mg/kg sc; 30 min after injection) had a significant anxiogenic effect, shown by specific decreases in the percentage of time spent on the open arms and in the percentage of open-arm entries. Tolerance developed to this anxiogenic effect after 7 days of nicotine treatment (0.1 mg/kg/day). Five minutes after an acute injection, nicotine (0.1 mg/kg) was ineffective, but after 7 days of treatment a significant anxiolytic effect, shown by specific increases in the percentage of time spent on the open arms and in the percentage of open-arm entries, emerged. After 14 days of nicotine treatment, tolerance developed to this anxiolytic effect. There was a complete dissociation between the effects of nicotine on the measures of anxiety, and on the locomotor activity as measured by closed-arm entries. No changes in closed-arm entries were found after acute administration of nicotine, but rats tested 30 min after their 7th injection made significantly fewer, and those tested 5 min after their 14th injection made significantly more, entries than their respective controls. Rats that were tested after 24 h withdrawal from six daily nicotine injections showed a significant anxiogenic effect. A low dose of nicotine (5 ng) injected into the dorsal hippocampus was without effect in vehicle pretreated rats, but it was able to reverse the anxiogenic effect found after 24 h of withdrawal from 6 days of nicotine treatment.
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Affiliation(s)
- E E Irvine
- Psychopharmacology Research Unit, Centre for Neuroscience, GKT School of Biomedical Sciences, King's College London, Hodgkin Building, Guy's Campus, SE1 1UL, London, UK
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24
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Padovan CM, Del Bel EA, Guimarães FS. Behavioral effects in the elevated plus maze of an NMDA antagonist injected into the dorsal hippocampus: influence of restraint stress. Pharmacol Biochem Behav 2000; 67:325-30. [PMID: 11124397 DOI: 10.1016/s0091-3057(00)00361-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The objective of the study was to investigate the influence of restraint stress on the effects of 2-amino-7-phosphonoheptanoic acid (AP7), an NMDA receptor antagonist, injected into the hippocampus of rats submitted to the elevated plus maze (EPM). Male Wistar rats with cannulas aimed to the dorsal hippocampus were forced immobilized for 2 h. Twenty four hours later they received bilateral injections of saline or AP7 (10 nmol/0.5 microl), and were tested in the EPM. In another experiment the animals received the treatment immediately before or after the restraint period, and were tested in the EPM 24 h later. AP7 had no effect in any anxiety measure in non-stressed rats. In stressed animals the drug increased the percentage of open arm entries when injected before the test in the EPM. When administered immediately after the restraint period, AP7 increased the percentage of time spent in the open arms and tended to do the same with the percentage of entries in these same arms. The results suggest that interference with hippocampal NMDA receptors modify the anxiogenic effect of restraint stress in an EPM.
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Affiliation(s)
- C M Padovan
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, 14049-900, Ribeirão Preto, Brazil
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File SE, Kenny PJ, Cheeta S. The role of the dorsal hippocampal serotonergic and cholinergic systems in the modulation of anxiety. Pharmacol Biochem Behav 2000; 66:65-72. [PMID: 10837844 DOI: 10.1016/s0091-3057(00)00198-2] [Citation(s) in RCA: 193] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A review of the literature suggests that the dorsal hippocampal serotonergic system, and, in particular, the postsynaptic 5-HT(1A) receptor, mediates an anxiogenic response, whereas endogenous dorsal hippocampal cholinergic tone mediates an anxiolytic response. Accordingly, it has been shown that direct dorsal hippocampal administration of the 5-HT(1A) receptor agonist, 8-OH-DPAT, the nicotinic receptor antagonist, mecamylamine, and the M(1) muscarinic receptor antagonist, pirenzepine, all have anxiogenic effects in rats tested in the social interaction test. It is therefore surprising that nicotine also has an anxiogenic effect in this test following dorsal hippocampal administration. However, the anxiogenic effects of mecamylamine and nicotine in the dorsal hippocampus are blocked by coadministration of the 5-HT(1A) receptor antagonist, WAY 100635, suggesting that both of these compounds act by enhancing hippocampal serotonergic transmission, thereby stimulating postsynaptic 5-HT(1A) receptors. This conclusion is supported by the observation that both nicotine and mecamylamine stimulate basal [3H]-5-HT release from dorsal hippocampal slices. A possible mechanism by which nicotinic receptor ligands modulate hippocampal 5-HT release is discussed, and it is proposed that the dorsal hippocampal serotonergic and cholinergic systems are tightly coupled and function antagonistically in the modulation of anxiety, as measured in the social interaction test. These systems are relatively unimportant in controlling behaviour on trial 1 in the plus-maze. On trial 2 in the elevated plus-maze, a model of specific phobia, the endogenous cholinergic system, nicotine, and the M(1) receptor agonist, McN-A-343, all mediate an anxiolytic effect, whereas stimulation of 5-HT(1A) receptors mediates an anxiogenic effect. It is proposed that the hippocampus may predominantly control the avoidance components of phobic anxiety, with other regions, such as the dorsomedial hypothalamus, controlling the escape components.
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Affiliation(s)
- S E File
- Psychopharmacology Research Unit, Centre for Neuroscience, GKT School of Biomedical Sciences, King's College London, Hodgkin Building, Guy's Campus, SE1 IUL, London, UK
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26
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Abstract
Rodents submitted to restraint stress show decreased activity in an elevated plus-maze (EPM) 24 h later. The objective of the present study was to determine if a certain amount of time is needed after stress for the development of these changes. We also wanted to verify if behavioral tolerance of repeated daily restraint would be detectable in this model. Male Wistar rats were restrained for 2 h and tested in the EPM 1, 2, 24 or 48 h later. Another group of animals was immobilized daily for 2 h for 7 days, being tested in the EPM 24 h after the last restraint period. Restraint induced a significant decrease in the percent of entries and time spent in the open arms, as well as a decrease in the number of enclosed arm entries. The significant effect in the number of entries and the percentage of time spent in the open arms disappeared when the data were submitted to analysis of covariance using the number of enclosed arm entries as a covariate. This suggests that the restraint-induced hypoactivity influences the measures of open arm exploration. The modifications of restraint-induced hypoactivity are evident 24 or 48 h, but not 1 or 2 h, after stress. In addition, rats stressed daily for seven days became tolerant to this effect.
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Affiliation(s)
- C M Padovan
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
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27
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Amat J, Matus-Amat P, Watkins LR, Maier SF. Escapable and inescapable stress differentially and selectively alter extracellular levels of 5-HT in the ventral hippocampus and dorsal periaqueductal gray of the rat. Brain Res 1998; 797:12-22. [PMID: 9630480 DOI: 10.1016/s0006-8993(98)00368-0] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The effects of escapable and yoked inescapable electric tailshocks on extracellular levels of serotonin (5-HT) in the ventral hippocampus and dorsal periaqueductal gray (dPAG) were measured by in vivo microdialysis. Inescapable, but not escapable shock increased extracellular 5-HT in the ventral hippocampus relative to restrained controls. Basal levels of 5-HT were elevated 24 h after inescapable shock, and previously inescapably shocked subjects exhibited an exaggerated 5-HT response to 2 brief footshocks. In contrast, escapable, but not inescapable shock, increased extracellular 5-HT in the dPAG, increased basal 5-HT in the dPAG 24 h later, and led to an enhanced 5-HT response to subsequent brief footshock.
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Affiliation(s)
- J Amat
- Instituto de Medicina Experimental, Universidad Central de Venezuela, Caracas, Venezuela
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28
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Avanzi V, Castilho VM, de Andrade TG, Brandão ML. Regulation of contextual conditioning by the median raphe nucleus. Brain Res 1998; 790:178-84. [PMID: 9593883 DOI: 10.1016/s0006-8993(97)01538-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The median raphe nucleus (MRN) has been suggested as the origin of a behavioral inhibition system that projects to the septum and hippocampus. Electrical stimulation of this mesencephalic area causes behavioral and autonomic manifestations characteristic of fear such as, freezing, defecation and micturition. In this study we extend these observations by analyzing the behavioral and autonomic responses of rats with lesions in the MRN submitted to a contextual conditioning paradigm. The animals underwent electrolytic or sham lesions of the median raphe nucleus. One day (acute) or 7 days (chronic) later they were tested in an experimental chamber where they received 10 foot-shocks (0.7 mA, 1 s with 20-s interval). The next day, sham and MRN-lesioned animals were tested again either in the same or in a different experimental chamber. During this, the duration of freezing, rearings, bouts of micturition and number of fecal boli were recorded. Sham-operated rats placed in the same chamber showed more freezing than rats exposed to a different context. This freezing behavior was clearly suppressed in rats with acute or chronic lesions in the MRN. MRN lesions also reduced the bouts of micturition and number of fecal boli. These rats showed a reduced number of rearings than sham-lesioned rats. This effect is probably the result of the displacement effect provoked by freezing since no significant differences in the number of rearings could be observed between these animals and the NMR-lesioned rats tested in an open field. This lesion produced higher horizontal locomotor activity in this test than the controls (sham-lesioned rats). These results point to the importance of the median raphe nucleus in the processing of fear conditioning with freezing being the most salient feature of it. Behavioral inhibition is also under control of MRN but its neural substrate seems to be dissociated from that of contextual fear.
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Affiliation(s)
- V Avanzi
- Laboratório de Psicobiologia, FFCLRP, Campus USP, Av. Bandeirantes 3900, 14049-901, Ribeirão Preto, SP, Brazil
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29
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Mendonça FH, Guimarães FS. Intra-hippocampal administration of cycloheximide attenuates the restraint-induced exploratory deficit of an elevated plus maze. Behav Brain Res 1998; 91:207-11. [PMID: 9580415 DOI: 10.1016/s0166-4328(97)00129-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Rats submitted to 2 h of restraint stress show a reduced open arm exploration in the elevated plus maze 24 h later. The stress-induced exploratory deficit is prevented by i.c.v. pre-stress administration of cycloheximide (CHX), a protein synthesis inhibitor. The objective of the present work was to determine if the hippocampus could be involved in this effect. CHX (4 or 8 microg) was injected into the dorsal hippocampus of male Wistar rats (200-250 g), immediately before (n = 9-20 animals/group) a 2 h period of forced restraint. After 24 h the animals were tested in the elevated plus maze. Non-stressed, control groups, received saline (SAL) or cycloheximide (CHX, n = 6-12/group) and were tested 1 or 24 h later in the maze. Pre-stress microinjections of cycloheximide increased exploration of open arms in the elevated plus maze (percentage of entries, SAL = 10.3 +/- 2.7, CHX 4 microg = 24.5 +/- 4.6, CHX 8 microg = 28.2 +/- 4.8, percentage of time spent, SAL = 2.0 +/- 0.6, CHX 4 microg = 8.4 +/- 2.3, CHX 8 microg = 9.6 +/- 2.6, Duncan test, P < 0.05). No drug effect was observed in non stressed animals. These results suggest that blockade of protein synthesis in the dorsal hippocampus during the restraint period may attenuate the behavioural consequences of stress.
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Affiliation(s)
- F H Mendonça
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brazil
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30
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Fiore M, Alleva E, Probert L, Kollias G, Angelucci F, Aloe L. Exploratory and displacement behavior in transgenic mice expressing high levels of brain TNF-alpha. Physiol Behav 1998; 63:571-6. [PMID: 9523900 DOI: 10.1016/s0031-9384(97)00514-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Studies reported recently have shown that tumor necrosis factor-alpha (TNF-alpha) a cytokine released by macrophages and monocytes plays a key role in inflammatory processes and immune and neuro-endocrine regulation. TNF-alpha is also produced in the central nervous system (CNS). However, the role of this cytokine in the CNS is largely unknown, although evidence indicates that it is involved in various neurobehavioral manifestations. Using transgenic mice expressing high amounts of murine TNF-alpha transgene in the neurons of the CNS, we investigated the stereotyped, exploratory, and displacement activities in the hole-board and black/white box. Transgenic mice and their normal control littermates were hybrids of the CBA x C57BL/6 genetic backgrounds and were obtained by backcrossing the CBA x C57BL/6 founder female and her progeny with F1 hybrid mates. Transgenic mice did not show changes in the stereotyped behavior on the hole-board, but they displayed several alterations in the exploratory activities both in the hole-board and black/white box. Transgenic mice also exhibited an increase in grooming when exposed to a highly unfamiliar environmental stimuli in the black/white box. The study suggests that supranormal endogenous TNF-alpha in the brain affects the behavioral responses to stressful conditions.
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Affiliation(s)
- M Fiore
- Institute of Neurobiology, CNR, Rome, Italy
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31
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Lino de Oliveira C, Guimarães FS, Del Bel EA. c-jun mRNA expression in the hippocampal formation induced by restraint stress. Brain Res 1997; 753:202-8. [PMID: 9125404 DOI: 10.1016/s0006-8993(96)01490-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The effect of restraint stress on c-jun mRNA expression in the hippocampal formation was investigated by in situ hybridization, dot blot and northern blot. c-jun mRNA expression increased after 60 min of forced restraint in the dentate gyrus, CA1 and CA3 regions of the hippocampal formation. The effect in the dentate gyrus was attenuated by pre-stress i.c.v. injection of the anxiolytic benzodiazepine midazolam (20 nmol/2 microl) or the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-7-phosphonoheptanoic acid (AP-7, 5 nmol/2 microl), but not by the 5-HT1A agonist, (+/-) 8-hydroxy-dipropylaminotetralin (8-OH-DPAT, 20 nmol/2 microl). These results suggest that the hippocampal formation is activated during restraint stress, and that this activation is modulated by benzodiazepine/GABA-A or NMDA receptors.
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Affiliation(s)
- C Lino de Oliveira
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto,SP, Brazil
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32
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Abstract
There are conflicting results on the function of 5-HT in anxiety and depression. To reconcile this evidence, Deakin and Graeff have suggested that the ascending 5-HT pathway that originates in the dorsal raphe nucleus (DRN) and innervates the amygdala and frontal cortex facilitates conditioned fear, while the DRN-periventricular pathway innervating the periventricular and periaqueductal gray matter inhibits inborn fight/flight reactions to impending danger, pain, or asphyxia. To study the role of the DRN 5-HT system in anxiety, we microinjected 8-OH-DPAT into the DRN to inhibit 5-HT release. This treatment impaired inhibitory avoidance (conditioned fear) without affecting one-way escape (unconditioned fear) in the elevated T-maze, a new animal model of anxiety. We also applied three drug treatments that increase 5-HT release from DRN terminals: 1) intra-DRN microinjection of the benzodiazepine inverse agonist FG 4172, 2) intra-DRN microinjection of the excitatory amino acid kainic acid, and 3) intraperitoneal injection of the 5-HT releaser and uptake blocker D-fenfluramine. All treatments enhanced inhibitory avoidance in T-maze. D-Fenfluramine and intra-DRN kainate also decreased one-way escape. In healthy volunteers, D-fenfluramine and the 5-HT agonist mCPP (mainly 5-HT2C) increased, while the antagonists ritanserin (5-HT2A/2C) and SR 46349B (5-HT2A) decreased skin conductance responses to an aversively conditioned stimulus (tone). In addition, D-fenfluramine decreased, whereas ritanserin increased subjective anxiety induced by simulated public speaking, thought to represent unconditioned anxiety. Overall, these results are compatible with the above hypothesis. Deakin and Graeff have suggested that the pathway connecting the median raphe nucleus (MRN) to the dorsal hippocampus promotes resistance to chronic, unavoidable stress. In the present study, we found that 24 h after electrolytic lesion of the rat MRN glandular gastric ulcers occurred, and the immune response to the mitogen concanavalin A was depressed. Seven days after the same lesion, the ulcerogenic effect of restraint was enhanced. Microinjection of 8-OH-DPAT, the nonselective agonist 5-MeO-DMT, or the 5-HT uptake inhibitor zimelidine into the dorsal hippocampus immediately after 2 h of restraint reversed the deficits of open arm exploration in the elevated plus-maze, measured 24 h after restraint. The effect of the two last drugs was antagonized by WAY-100135, a selective 5-HT1A receptor antagonist. These results are compatible with the hypothesis that the MRN-dorsal hippocampus 5-HT system attenuates stress by facilitation of hippocampal 5-HT1A-mediated neurotransmission. Clinical implications of these results are discussed, especially with regard to panic disorder and depression.
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Affiliation(s)
- F G Graeff
- Laboratório de Psicofarmacologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto, Brasil.
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