Early malnutrition alters the effect of chlordiazepoxide on inhibitory avoidance.

In order to study the functional consequences of brain changes caused by early malnutrition, rats were fed a protein-deficient diet from birth until 49 days of age and a balanced diet from day 50 to day 70. The animals were submitted to a step-down inhibitory avoidance task and to the flinch-jump nociceptive test at 49 and 70 days of age. Malnourished rats showed longer step-down latencies and lower flinch and jump thresholds than eutrophic animals. Chlordiazepoxide (5 mg/kg, ip) shortened step-down latency of well-nourished rats, whereas it failed to do so in malnourished rats. Since well-nourished animals also became resistant to chlordiazepoxide when tested with a higher shock intensity, generating avoidance latencies comparable to those of malnourished animals, we conclude that the drug resistance induced by malnutrition may be secondary to enhanced pain sensitivity and/or reactivity.