RESUMO
The present study investigated the effect of repeated stress applied to female rats on memory evaluated by three behavioral tasks: two-way shuttle avoidance, inhibitory avoidance and habituation to an open field. Repeated stress had different effects on rat behavior when different tasks were considered. In the two-way active avoidance test the stressed animals presented memory of the task, but their memory scores were impaired when compared to all other groups. In the habituation to the open field, only the control group showed a significant difference in the number of rearings between training and testing sessions, which is interpreted as an adequate memory of the task. In the handled and chronically stressed animals, on the other hand, no memory was observed, suggesting that even a very mild repeated stress would be enough to alter habituation to this task. The performance in the inhibitory avoidance task presented no significant differences between groups. The findings suggest that repeated restraint stress might induce cognitive impairments that are dependent on the task and on stress intensity.
Assuntos
Aprendizagem da Esquiva , Memória , Estresse Fisiológico , Análise de Variância , Animais , Comportamento Animal , Feminino , Ratos , Ratos Wistar , Restrição Física , Estresse Fisiológico/psicologiaRESUMO
The present study investigated the effect of repeated stress applied to female rats on memory evaluated by three behavioral tasks: two-way shuttle avoidance, inhibitory avoidance and habituation to an open field. Repeated stress had different effects on rat behavior when different tasks were considered. In the two-way active avoidance test the stressed animals presented memory of the task, but their memory scores were impaired when compared to all other groups. In the habituation to the open field, only the control group showed a significant difference in the number of rearings between training and testing sessions, which is interpreted as an adequate memory of the task. In the handled and chronically stressed animals, on the other hand, no memory was observed, suggesting that even a very mild repeated stress would be enough to alter habituation to this task. The performance in the inhibitory avoidance task presented no significant differences between groups. The findings suggest that repeated restraint stress might induce cognitive impairments that are dependent on the task and on stress intensity
Assuntos
Animais , Ratos , Feminino , Aprendizagem da Esquiva , Memória , Estresse Fisiológico , Análise de Variância , Comportamento Animal , Ratos Wistar , Restrição Física , Estresse Fisiológico/psicologiaRESUMO
Epinephrine released or administered soon after a given training task modulates memory processes. Since epinephrine does not readily cross the blood-brain barrier, studies have suggested that some of the central effects of epinephrine might be mediated by peripheral release of glucose. These experiments examined the involvement of blood glucose levels in the posttraining effects of peripherally administered epinephrine. The effects of the administration of epinephrine (25 and 625 microg/kg) [corrected] on memory of an inhibitory avoidance task were evaluated in fed and fasted rats (depleted glycogen stores in liver). Blood glucose levels after the task in each group were also measured. Female Wistar rats were divided in two groups. Fed and 48-h-fasted animals were submitted to the inhibitory avoidance task and received i.p. epinephrine or saline immediately after training. The test session was carried out 48 h after training. Epinephrine (25 or 625 microg/kg) [corrected] caused an increased glycemia in fed rats, but no effect was observed in fasted animals. Administration of epinephrine 25 microg/kg [corrected] induced a facilitation of memory, while epinephrine 625 microg/kg [corrected] impaired retention (either in fasted or in fed animals). There was no relation between increased glycemia induced by epinephrine and its effects on memory, since this drug presented its classical effects independently of the previous state of the animal (fed or fasted). The results of the present study suggest that the effects of systemic released or administered epinephrine on memory processes are not dependent on hepatic glucose release.
Assuntos
Aprendizagem da Esquiva/efeitos dos fármacos , Glicemia/metabolismo , Epinefrina/farmacologia , Fígado/efeitos dos fármacos , Rememoração Mental/efeitos dos fármacos , Retenção Psicológica/efeitos dos fármacos , Animais , Relação Dose-Resposta a Droga , Feminino , Inibição Psicológica , Glicogênio Hepático/metabolismo , Ratos , Ratos Wistar , Tempo de Reação/efeitos dos fármacosRESUMO
The expression of appetite reflects the complex functioning of a psychobiological system organized in different levels closely related to each other, in which emotional changes can influence feeding behavior. Benzodiazepines are widely used as anxiolytics and can change behaviors caused by stress. The aim of the present study was to verify the feeding behavior of rats, submitted or not to fasting, after acute and chronic restraint stress. We also evaluated the response to the ingestion of sweet food of chronically restrained animals after the administration of diazepam. Male adult Wistar rats were exposed to restraint 1 h/day for 50 days in the chronic model. In the acute model, there was a single exposure. Four hours after the stress, the animals were placed in a lightened area in the presence of 10 pellets of sweet food (Froot Loops). The number of ingested Froot Loops was measured during a period of 3 min in the presence or absence of fasting. The groups acutely stressed showed ingestion similar to that of the control group, whether they had been fasted or not. The chronically stressed animals showed increased ingestion of sweet food. Diazepam given 60 min before the test session of the stressed rats reduced the ingestion of these animals to control levels. Thus, the chronic stress increases appetite for sweet food, independently of hunger, and diazepam is able to reverse this behavior.