Effects of undernutrition during suckling on footshock escape behavior and of post-training beta-endorphin administration on inhibitory avoidance task test behavior of young rats.
The hypothalamic beta-endorphin system of young Wistar rats of both sexes (21-day-old) responds in a distinct way to behavioral situations when compared to adult rats (90 to 120-day-old). In the present study we investigated whether the post-training amnestic effect of beta-endorphin previously demonstrated in Wistar adult rats is also observed in young (21-day-old) well-nourished and undernourished rats. Rats were undernourished since birth by feeding their dams an 8% casein diet, while well-nourished offspring were fed by dams maintained on a 20% casein diet. beta-endorphin was administered after training in a step-down inhibitory avoidance task using a 0.2- or 0.8-mA footshock. Retention was tested 24 h later. We observed that the dose of beta-endorphin (1 microgram/kg, ip) previously reported to have an amnestic effect on adult rats was ineffective in weanling rats of both nutritional groups. At a higher dose (2 micrograms/kg, ip) and using a 0.2-mA shock, beta-endorphin impaired the retention only of well-nourished rats. Test-to-training difference (in s) in step-down latency for well-nourished beta-endorphin-treated rats was 7 vs 25 s for well-nourished rats treated with saline (P < 0.05). Undernourished rats were hyperreactive to this shock intensity. Footshock escape latency (in s) for undernourished rats was 3.56 vs 5.80 for well-nourished rats (P < 0.05, experiment 1) and 5.01 vs 10.89 (P < 0.05, in experiment 2) and showed better retention than did well-nourished rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Souza
D O
DO
Departamento de Bioquímica, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil.
Vendite
D
D
Mello
C F
CF
Rocha
J B
JB
D000367:Age Factors; D000818:Animals; D000833:Animals, Suckling; D004924:Escape Reaction / Q000187:drug effects* / Q000502:physiology*; D005260:Female; D008297:Male; D009748:Nutrition Disorders / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D001615:beta-Endorphin / Q000494:pharmacology*
D001615:beta-Endorphin