Resumo

Introduction: Stress involves a group of reactions and stimulus able to promote several alterations in the organism, including harmful effects in learning and memory. Among the alterations induced by physical and social stressful stimuli, several researches have demonstrated that learning and memory modulation by stress adhere to the general pattern of the adaptive versus maladaptive stress response pattern, i.e., extreme low or high stress induce memory impairment. It is important to note that most of the studies were taken with male subjects. The aim of the present study is to investigate the effects of physical (restraint stress) and psychological (social isolation and overcrowding) stress in female rats evaluate in the plus-maze discriminative avoidance task. Methods and Results: Female Wistar rats were allocated to the following groups: Control Group (CG), Restraint Stress (RS), Social Isolation (SI) and Overcrowding (OC). The animals of the restraint stress group were placed in cylindrical restraint tubes during 4 hours for seven consecutive days. Each animal of social isolation group was allocated in an individual cage during 18 hours for seven consecutive days and the animals of overcrowding stress were allocated in groups of 5 in a small cage during 18 hours for seven days. Afterwards, the animals were placed in the center of a plus maze with two open and two enclosed arms. In one of the enclosed arms, aversive stimuli (light and noise) were presented every time the animal entered in the aversive arm, lasting until the animal leaves it (training session). After 24h during test session, the stimuli were no longer applied. The time spent in each arms was registered. Our results showed that animals of the restraint stress group demonstrated impaired memory retrieval of the task (CG = 13.6 ± 5.7% and RS = 43.6 ± 12.4% time spent in aversive arm). On the other hand, social isolation (27.5 ± 4.5%) and overcrowding (21.4 ± 4.8%) groups did not show any difference compared to control group. Conclusions: These results indicate that exposure to physical (but not social) stressors can affect learning and memory of an aversive task . Further studies are needed to verify if these differences are related to influence of stress levels on memory consolidation.