Passive avoidance behavior and response thresholds in adult male rats after early postnatal undernutrition.

Rats were undernourished from birth to 25 days of age. Although severely growth retarded, they had probably received more attention from their mothers than had well fed pups. When the previously undernourished rats were tested as adults in a passive avoidance situation they showed stronger passive avoidance behavior than controls rats. When the rats were retested at a later age in a situation where they were given different intensities of inescapable electric shock, the previously undernourished rats showed more jump responses, and more frequent vocalizations than control rats. Analysis of jump responses revealed that the previously undernourished rats had a lower jump threshold than control rats.