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Weanling male and female Wistar rats, whose mothers received low protein diet (6.8%) during pregnancy and lactation, were fed on the same diet of their mothers and trained in an active avoidance situation at the ages of 60, 90 or 120 days. Control animals fed on a 20% protein diet of the same age groups were submitted to similar training. The consolidation and performance of the conditioned avoidance response and other behavioral reactions were studied. The malnourished animals showed delay of consolidation and lower frequency of conditioned avoidance responses, escape responses and holdings as well as higher frequency of anticipatory reactions, vocalization, riddance attempts and touching of surroundings. The results show that chronic malnutrition impairs the active avoidance response. They also show that chronic malnutrition affects the emotional behavior more markedly than early malnutrition. Chronic malnutrition also enhances the exploratory activity, in contrast to early malnutrition, and this is attributed to an alimentary drive-dependent mechanism.

1. Rats were fed the "basic regional diet" (BRD) utilized by some human populations in northeastern Brazil, which contains only 7.8% protein (mainly from beans), to produce a form of malnutrition. The effects of chronic malnutrition on nerve impulse conduction velocity was studied in the sciatic nerve of young (121-143 days) and old (420-540 days) rats. 2. BRD rats presented a 50% reduction in sciatic nerve conduction velocity compared to controls fed a diet containing 22% casein. 3. Rats chronically fed a commercially available diet (CD group) containing an intermediate level of protein (14%) presented conduction velocities intermediate between values obtained from control and BRD rats (62% to 76% of the control values). 4. The conduction velocities of animals belonging to the same nutritional group were independent of sex, body weight or age. 5. Nutritional restriction imposed only in adult life by increasing the number of rats per cage in the casein group did not have any effect on the conduction velocity of nerve impulses. 6. The severity of the effects observed in the malnourished rats may be related to the quantity and quality of protein in the diet. In this respect, the present data agree with those reported in the literature on human and animal experiments. 7. The present results justify the use of the foods ingested by malnourished human populations for the development of experimental animal models of malnutrition.