Effects of undernutrition during suckling on novelty-induced analgesia in young and adult rats.

The effects of undernutrition on novelty-induced analgesia were investigated in young and adult rats. Rats were undernourished by feeding their dams an 8% casein diet from birth until weaning (21 days of age). Rats were exposed to an open field (novelty) for 2 min and the nociception was measured by the tail-flick method. At adult age, only well-nourished rats presented novelty-induced analgesia, suggesting that early undernutrition abolishes this response. At 21 days of age, the exposure to the open field had no effect on nociception of both nutritional groups, suggesting that some developmental factor is necessary for the emergence of novelty-induced analgesia.