Response of the adrenals to stress in animals from litters with different numbers of young.

Undernutrition and overnutrition during the suckling period -- achieved by adjusting the number of infant rats per litter to 4, 8 and 14 -- resulted in a decrease in the plasma corticosterone level and in corticosterone production by the adrenals in vitro in overfed animals at the age of 30, 180 and 300--360 days. An enhanced response to ether anaesthesia or immobilization stress was found in overfed animals from the smallest litters. The results show that a change in postnatal nutrition and in social relationships in the litter influences maturation of the hypoathalamo-hypophysio-adrenal regulatory system; in adulthood this is manifested in changes in production of the adrenal hormones and in the reaction of the adrenals to stress.