Effects of post-training ß-endorphin and Met-enkephalin administration on two-way active avoidance task in well-nourished and protein malnourished rats

RESUMO

Protein malnutrition during suckling period or throughout the life affects the hypothalamic ß-endorphinergic system of adult rats. In the present study, rats were under nourished during suckling by feeding their dams an 8% casein diet whereas well-nourished dams recived a 25% casein diet from birth until weaning (21 day of postnatal life). After weaning, the offsprings were maintained with the same diet as their dams. When rats were 3 month-old, they were subjected to two-way active avoidance task. Protein malnutrition did not affect the performance in the two-way active avoidance task. Post-training ß-endorphin or Met-enkephalin administration impaired the retention of shuttle avoidance tast in both well-nourished and undernourished rats. However, the amnesic effect of the peptides was only achieved in undernourished rats with higher doses of apioids when compared to the well-nourished rats. These data suggest that undernourished rats present alterations in opioid sensitivity which may be related to changes in the levels of ß-endorphin previously observed both in brain and hypothalamus of early undernourished adults rats