Effects of post-training beta-endorphin and Met-enkephalin administration on two-way active avoidance task in well-nourished and protein malnourished rats.
Protein malnutrition during suckling period or throughout the life affects the hypothalamic beta-endorphinergic system of adult rats. In the present study, rats were undernourished during suckling by feeding their dams an 8% casein diet whereas well-nourished dams received 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 beta-endorphin or Met-enkephalin administration impaired the retention of shuttle avoidance task in both well-nourished and undernourished rats. However, the amnesic effect of the peptides was only achieved in undernourished rats with higher doses of opioids 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 beta-endorphin previously observed both in brain and hypothalamus of early undernourished adult rats.
Souza
D O
DO
Departamento de Bioquimica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil.
Branchtein
L
L
Costa
R D
RD
Rocha
J B
JB
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D001923:Brain Chemistry; D004032:Diet; D004744:Enkephalin, Methionine / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D011502:Protein-Energy Malnutrition / Q000150:complications*; D051381:Rats; D017208:Rats, Wistar; D001615:beta-Endorphin / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*
D004744:Enkephalin, Methionine; D001615:beta-Endorphin