The effects of early experience on behavior and growth characteristics.

Abstract

Using a split-litter distribution, half of a sample of albino rats were handled daily for 10-minute periods, starting immediately after weaning and continuing for the next 21 days. At 58 and at 65 days of age the animals were tested for activity in an open field. At 79 days each animal was immobilized for 48 hours under food and water deprivation and was then killed and autopsied. In a second experiment a similar gentling procedure was used, and food intake was measured; in addition these animals received exercise daily in an enclosed maze. A third experiment essentially repeated the first with modifications in activity recording. A final experiment measured adrenal gland weight at 59 days of age after earlier gentling of the type described above. Results indicated that gentling influenced (1) increase in body weight and skeletal length, (2) increase of activity in an open field and (3) decrease in organic damage following immobilization stress. Adrenal glands of non-gentled animals were significantly heavier.