The resilience of adolescent male rats to acute stress-induced delayed anxiety is age-related and glucocorticoid release-dependent.

Studies investigated how stressful experiences modulate physiological and behavioral responses and the consequences of stress-induced corticosterone release in anxiety-like behavior. Adolescence is crucial to brain maturation, and several neurobiological changes in this period lead individuals to increased susceptibility or resilience to aversive situations. Despite the effects of stress in adults, information about adolescents' responses to acute stress is lacking. We aimed to understand how adolescence affects acute stress responses. Male adolescent rats (30 days old) were 2 h restrained, and anxiety-like behaviors were measured immediately or 10 days after stress in the elevated plus-maze (EPM) and the light-dark box (LDB) tests. To verify the importance of CORT modulation in stress-induced anxiety, another group of rats was treated, 30 min before restraint, with metyrapone to blunt the stress-induced CORT peak and tested immediately after stress. To show that stress effects on behavior were age-dependent, another set of rats was tested in two different periods - early adolescence (30 days old) and mid-adolescence (40 days old) and were treated or not with metyrapone before the stress session and tested immediately or ten days later in the LDB test. Only early adolescent male rats were resilient to delayed anxiety-like behavior in EPM and LDB tests. Metyrapone treatment increased the rats' exploration immediately and ten days after stress. These data suggest a specific age at which adolescent rats are resilient to the delayed effects of acute restraint stress and that the metyrapone treatment has long-term behavioral consequences.

Exploring the light/dark box test: Protocols and implications for neuroscience research.

BACKGROUND: Knowledge on the neurobiological systems underlying psychiatric disorders has considerably evolved due to findings on basic research using animal models. Anxiety-like behaviors in rodents are widely explored in neuroethological apparatuses, such as the light-dark box (LDB) test through different protocols, which have been shown to influence the behavioral outcomes and probably the activation of the hypothalamic-pituitary-adrenal (HPA) axis. NEW METHOD: Adult male Wistar rats were submitted to LDB in different room illumination conditions (25/0, 65/0 and/or 330/0 lux), initial positioning in the LDB compartments and previous stressful experience in the Elevated Plus Maze (EPM) or restraint stress (RS). Rats' behavior (exploratory and risk assessment) was registered during a 15 min period, divided into blocks of 5 min RESULTS: Exploration of the lit compartment decreased in higher luminosity condition, as after positioning rats in the dark compartment or previous exposure to the EPM, while low luminosity increased exploration of the LDB. No differences were observed on serum corticosterone in all groups and experimental conditions. COMPARISON WITH EXISTING METHODS: Light intensity and test duration influenced exploration of the LDB jeopardizing the anxiolytic/anxiogenic effects. Low light intensity increased exploration, while high intensity decreased it. These results suggest that 65/0 lux is a neutral condition to investigate possible anxiolytic/anxiogenic effects of drugs and/or exposure to previous aversive stimuli as the EPM. CONCLUSIONS: Different factors impact on exploratory and risk assessment behaviors which may be related to safety maximization behavior. Unraveling how different factors affect behavior may be a crucial step towards understanding its expression and the contributions on advances in the physiopathology 1 and treatment of psychiatric disorders.

Early and late behavioral consequences of ethanol withdrawal: focus on brain indoleamine 2,3 dioxygenase activity.

Anxiety and depression are symptoms associated with ethanol withdrawal that lead individuals to relapse. In the kynurenine pathway, the enzyme indoleamine 2,3 dioxygenase (IDO) is responsible for the conversion of tryptophan to kynurenine, and dysregulation of this pathway has been associated with psychiatric disorders, such as anxiety and depression. The present study evaluated the early and late behavioral and biochemical effects of ethanol withdrawal in rats. Male Wistar rats were submitted to increasing concentrations of ethanol in drinking water during 21 days. In experiment 1, both control and withdrawal groups were submitted to a battery of behavioral tests 3, 5, 10, 19, and 21 days following ethanol removal. In experiment 2, animals were euthanized 3 days (short-term) or 21 days (long-term) after withdrawal, and the brains were dissected altogether, following kynurenine concentration analysis in prefrontal cortex, hippocampus, and striatum. Short-term ethanol withdrawal decreased the exploration of the open arms in the elevated plus-maze. In the forced swimming test, long-term ethanol-withdrawn rats displayed higher immobility time than control animals. Ethanol withdrawal altered neither locomotion nor motor coordination of rats. In experiment 2, kynurenine concentrations were increased in the prefrontal cortex after a long-term period of withdrawal. In conclusion, short-term ethanol withdrawal produced anxiety-like behaviors, while long-term withdrawal favored depressive-like behaviors. Long-term ethanol withdrawal elevated kynurenine levels, specifically in the prefrontal cortex, suggesting that the depressive-like responses observed after long-term withdrawal might be related to the increased IDO activity.

Ethanol withdrawal induces anxiety-like effects: Role of nitric oxide synthase in the dorsal raphe nucleus of rats.

Nitric oxide (NO) mediated transmission in the dorsal raphe nucleus (DRN) has been shown to be involved in the modulation of anxiety-like behaviors. We investigated whether inhibition of nitric oxide synthase (NOS) in the DRN would prevent anxiety-like behavior induced by ethanol withdrawal. Male Wistar rats were treated with ethanol 2-6% (v/v) for a period of 21 days. Ethanol withdrawal was induced by abrupt discontinuation of the treatment. Experiments were performed 48 h after ethanol discontinuation. Rats with a guide cannula aimed at the DRN received intra-DRN injections of the non-selective NOS inhibitor NG-nitro-l-arginine methyl ester (l-NAME), selective neuronal NOS (nNOS) inhibitor N(ω)-propyl-l-arginine (NPLA), or selective inhibitor of inducible NOS (iNOS) N-([3-(aminomethyl)phenyl] methyl) ethanimidamidedihydrochloride (1400W). Five minutes later, the animals were tested in the elevated plus maze (EPM). Plasma ethanol levels were determined by gas chromatography. There was a reduction in plasma ethanol levels 48 h after ethanol withdrawal. Rats from the ethanol withdrawal group showed decreased exploration of the open arms of the EPM with no change in the exploration of enclosed arms. Intra-DRN treatment with l-NAME (100 nmoles/0.2 µL) and 1400W (1 nmol/0.2 µL), but not NPLA (10 nmoles/0.2 µL) in the DRN attenuated the decrease in the exploration of the open arms of the EPM induced by ethanol withdrawal. The major new finding of the present study is that iNOS in the DRN plays a role in the anxiety-like behavior induced by ethanol withdrawal.

Memory, learning, and participation of the cholinergic system in young rats exposed to environmental enrichment.

The present study demonstrates the consequences of animal exposure to an enriched environment compared to animals living in a standard environment regarding learning and space memory. Male albino Wistar rats were exposed to an enriched environment for 4 weeks after the lactation period and tested in the Morris water maze in the distal and proximal clue version and in the arena. In the former test, the animals were tested at 50 days of age with 12 daily trials on two consecutive days. At the end of each session, scopolamine at the dose of 0.6 mg/kg/ml or saline solution was injected intraperitoneally. Twenty-eight days after the first phase, a new test consisting of a single trial was held (retest). An independent group of animals receiving no drug was subjected to the arena test and to the proximal clue version of the Morris maze. In the distal clue version the results did not show differences between groups in the first phase of the experiment. After 28 days (retest), the animals reared in a standard environment and treated with scopolamine exhibited a significant increase in latency compared to the group receiving the same drug and stimulated and to the group receiving saline. The arena data demonstrated a significant increase in exploratory activity in the group of animals reared in an enriched environment. The proximal clue version of the Morris maze did not show differences between groups. The results of the present study indicate that animals exposed to environmental enrichment react less to the amnesic effects of scopolamine and show an increase in exploratory activity.

Chemical neuroanatomical and psychopharmacological evidence that κ receptor-mediated endogenous opioid peptide neurotransmission in the dorsal and ventral mesencephalon modulates panic-like behaviour.

The chemical neuroanatomy and the effects of central administration of opioid antagonists on the innate fear-induced responses elicited by electrical (at escape behaviour threshold) stimulation of the midbrain tectum were determined. The aim of the present work was to investigate the interaction between the tecto-nigral endogenous opioid peptide-mediated disinhibitory pathways and nigro-tectal inhibitory links in the control of panic-like behaviour and their organisation in the continuum comprised by the deep layers of the superior colliculus (dlSC) and the dorsolateral columns of the periaqueductal grey matter (dlPAG). Beta-endorphin-labelled neurons and fibres were found in the dorsal midbrain and also in the substantia nigra. Opioid varicose fibres and terminal buttons were widely distributed in PAG columns and in all substantia nigra subdivisions. Microinjections of naltrexone (a non-selective opioid receptor antagonist; 5.0 µg/0.2 µl) or nor-binaltorphimine (a selective κ-opioid receptor antagonist; 5.0 µg/0.2 µl) in the dlSC/dlPAG continuum, in independent groups of animals, induced significant increases in the escape thresholds for midbrain tectum electrical stimulation. The microinjection of naltrexone or nor-binaltorphimine into the SNpr also increased the escape behaviour threshold for electrical stimulation of dlSC/dlPAG. These morphological and neuropharmacological findings support previous evidence from our team for the role played by the interaction between opioidergic and GABAergic mechanisms in the modulation of innate fear-induced responses. The present data offer a neuroanatomical basis for both intratectal axo-axonic/pre-synaptic and tecto-nigral axo-somatic opioid inhibition of GABAergic nigro-tectal neurons that modulate the dorsal midbrain neurons related to the organisation of fear-related emotional responses.

Antidepressants: knowledge and use among nursing students.

This study examined the knowledge of nursing students in regard to using antidepressant medication and proposes actions such that nurses contribute to a safe and effective antidepressant therapy. This cross-sectional and descriptive study was conducted in a public nursing school in the state of São Paulo, Brazil, between March and November 2008. Fifty-two (19%) out of the 273 participants were using or had used antidepressants. Instruction concerning the use of antidepressants was provided by physicians. Even after receiving instruction concerning the antidepressant treatment before its administration, the majority of users (chi(1)2=0.07, p> 0.05) still had doubts about its use. Fluoxetine was the most prevalent antidepressant. Actions to improve knowledge concerning the use of antidepressant medications, their side and therapeutic effects, seem to be necessary and relevant.

Antidepressants: knowledge and use among nursing students / Antidepressivos: uso e conhecimento entre estudantes de enfermagem / Antidepresivos: uso y conocimiento entre estudiantes de enfermería

This study examined the knowledge of nursing students in regard to using antidepressant medication and proposes actions such that nurses contribute to a safe and effective antidepressant therapy. This cross-sectional and descriptive study was conducted in a public nursing school in the state of São Paulo, Brazil, between March and November 2008. Fifty-two (19 percent) out of the 273 participants were using or had used antidepressants. Instruction concerning the use of antidepressants was provided by physicians. Even after receiving instruction concerning the antidepressant treatment before its administration, the majority of users (cII1=0.07, p> 0.05) still had doubts about its use. Fluoxetine was the most prevalent antidepressant. Actions to improve knowledge concerning the use of antidepressant medications, their side and therapeutic effects, seem to be necessary and relevant.

Este estudo teve como objetivos analisar o nível de conhecimento de estudantes universitários de enfermagem que usam antidepressivos e propor ações para que os enfermeiros contribuam para a farmacoterapia antidepressiva segura e efetiva. Trata-se de estudo transversal e descritivo, realizado em uma Escola de Enfermagem pública do Estado de São Paulo, entre março e novembro de 2008. Dos 273 estudantes entrevistados, 52 (19 por cento) participantes utilizam ou já utilizaram antidepressivos. A orientação do uso dessa classe medicamentosa foi realizada majoritariamente pelo médico. Mesmo com a orientação pré-administração do antidepressivo, a maioria dos usuários (cII1=0,07; p>0,05) tem dúvida a respeito do uso de antidepressivos. A fluoxetina foi o medicamento antidepressivo mais utilizado. Ações para produzir maior conhecimento quanto ao uso, efeitos colaterais e terapêuticos dos antidepressivos, por parte dos enfermeiros, parecem ser necessárias e oportunas.

Este estudio tuvo como objetivo examinar los conocimientos de los estudiantes que utilizan los antidepresivos y proponer acciones que contribuyan para que los enfermeros realicen una terapia segura y eficaz. Este es un estudio descriptivo transversal realizado en una Escuela de Enfermería pública en el estado de Sao Paulo entre marzo y noviembre de 2008. De los 273 participantes del estudio, 52 (19 por ciento) participantes utilizan o han utilizado antidepresivos. La orientación se realizó principalmente por el médico. Incluso, con la orientación previa a la administración de antidepresivos, la mayoría de los estudiantes (cII1 = 0,07, p> 0,05) tiene dudas sobre el uso de antidepresivos. La fluoxetina es el fármaco más utilizado. Acciones para generar mayor conocimiento sobre el uso y efectos terapéuticos de los antidepresivos por parte de las enfermeras, parecen necesarias y apropiadas.

Restraint stress induces beta-amyloid precursor protein mRNA expression in the rat basolateral amygdala.

Several studies have shown the involvement of beta-amyloid precursor proteins (APP) isoforms in physiological process like development of the central nervous system (CNS), functional roles in mature brain, and in pathological process like Alzheimer's disease, neuronal experimental damage, and stress, among others. However, the APP functions are still not clear. In the brain, APP(695) isoform is predominantly found in neurons while APP(751/770) isoforms are predominantly found in astroglial cells and have been associated to neurodegenerative processes. Acute or chronic stress in rats may trigger specific response mechanisms in several brain areas such as amygdala, hippocampus and cortex with the involvement of multiple neurotransmitters. Chronic stress may also induce neuronal injury in rat hippocampus. In situ hybridization (ISH) was used to investigate the expression of APP(695) and APP(751/770) mRNA in amygdala and hippocampus of male Wistar rats (n=4-6 per group) after acute (2 or 6h) or chronic (2h daily/7 days or 6h daily/21 days) restraint stress. Only the APP(695) mRNA expression was significantly increased in the basolateral amygdaloid nuclei following acute or chronic restraint. No APP isoform changed in hippocampus after any stress condition. These results suggest that restraint stress induces changes in gene expression of APP(695) in basolateral amygdaloid nucleus, an area related to stress response.

Estresse, depressäo e hipocampo / Stress, depression and the hippocampus

A exposiçäo a fatores estressantes tem papel importante no desenvolvimento de transtornos depressivos. Os mecanismos envolvidos nesta relaçäo, no entanto, ainda säo pouco conhecidos, mas algumas evidências sugerem a participaçäo da formaçäo hipocampal: 1. o estresse pode causar alteraçöes plásticas no hipocampo, que incluem remodelaçäo dendrítica e inibiçäo de neurogênese. Drogas antidepressivas impendem estes efeitos, possivelmente por aumentarem a expressäo de fatores neurotróficos; 2. a facilitaçäo da neurotransmissäo serotoninérgica no hipocampo atenua conseqüências comportamentais do estresse e produz efeitos antidepressivos em modelos animais; 3. o antagonismo do principal neurotransmissor excitatório no hipocampo, o glutamato, produz efeitos semelhantes; 4. o hipocampo parece estar "hiperativo" em animais mais sensíveis em modelos de depressäo e em humanos resistentes à antidepressivos; 5. o hipocampo, em conjunto com o complexo amigdalar, parece ter papel fundamental na consolidaçäo e evocaçäo de memórias aversivas. Näo obstante estas evidências, o desafio futuro será o de tentar integrar os resultados destes diferentes campos (farmacológico, molecular, eletrofisiológico, clínico) em uma teoria unificadora sobre o papel do hipocampo na regulaçäo do humor e seus transtornos bem como nos efeitos de tratamentos antidepressivos

Activation of post-synaptic 5-HT(1A) receptors in the dorsal hippocampus prevents learned helplessness development.

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.

[Stress, depression and the hippocampus]. / Estresse, depressão e hipocampo.

Stress exposure is an important factor in the development of depressive disorders. Although the mechanisms of this relationship are largely unknown, several pieces of evidence point to an involvement of the hippocampal formation: 1. stressful stimuli cause remodeling of hipocampal pyramidal cells and inhibit neurogenesis in the dentate gyrus. Antidepressive drugs attenuate these effects, probably by increasing the expression of neurotrophic factors; 2. facilitation of serotonergic neurotransmission in the hippocampus attenuates behavioral consequences of stress and produce antidepressive-like effects in several animal models; 3. antagonism of glutamate, the main excitatory neurotransmitter of the hippocampus, also induce antidepressive-like effects; 4. increased hippocampal activity has been described in genetically selected rats that are more sensitive to depression models. Similar result was found in depressive patients that fail to respond to antidepressant drugs; 5. together with the amygdala, the hippocampus plays a key role on consolidation and evocation of aversive memories. The challenge for the future will be to integrate the results from these different fields (clinical, electrophysiological, pharmacological and molecular) in an unifying theory about the role of the hippocampus on mood regulation, depressive disorder and antidepressant effects.

Effects of isolation-rearing on serotonin-1A and M1-muscarinic receptor messenger RNA expression in the hipocampal formation of rats.

The aim of the present work was to investigate if isolation rearing could change 5-HT1A or M1 muscarinic receptors messenger RNA (mRNA) expression in the hippocampal formation. Male Wistar rats were isolated either in single cages or in groups of six per cage soon after wearing during 30 days. After this period they were sacrificed and their brains removed for 'in situ' hybridization study using 32P-labeled oligonucleotide probes complementary to 5-HT1A or M1 muscarinic receptor mRNA. The results were analyzed by computerized densitometry. They showed a significant (P < 0.05, Mann-Whitney test) serotonin 1A (5-HT1A) mRNA expression increase in the dentate gyrus and CA3 areas of isolated animals. The signal also tended to be higher (P < 0.10) in CA1 and CA4 regions. No significant change on M1 mRNA expression was found. These results may reflect up-regulation of 5-HT1A gene transcription in response to deficits in hippocampal serotonin neurotransmission induced by social isolation.