Effects of undernutrition during suckling and of novelty on hypothalamic beta-endorphin immunoreactivity in young rats.

The present report examines the effect of undernutrition and of exposure to an open-field (novelty) on hypothalamic beta-endorphin immunoreactivity in 21-day old rats. The effect of posttraining beta-endorphin administration in open-field performance was also studied. Undernutrition and novelty had no effect on hypothalamic beta-endorphin. Post-training administration of beta-endorphin did not alter the performance of rats in either nutritional group in the test session. The results suggest that the hypothalamic beta-endorphinergic system of young rats is not activated by novelty and that the effect of undernutrition on this system found in adult rats is not detectable at this age.