Abstract
During the first 5 days of life newborn rats were handled, shocked, or exposed to heat stress for 3 min. Controls were not disturbed during this interval. All animals were weaned at 21 days. At 35 days, the four groups were split into thirds and were stressed by exposure to an-open field, electric shock, or heat for 3 min. They were then returned to their home cages and killed 12, 27, or 57 min later and their blood analyzed for plasma corticosterone. The group handled in infancy had a significantly smaller corticosterone response than controls and those who received shock in infancy, regardless of the nature of the stress experienced at 35 days. The data are compatible with the hypothesis that handling has certain unique features not shared by other forms of infant stimulation.
