FUNCTIONING OF HYPOTHALAMO-PITUITARY-ADRENAL SYSTEM DURING POSTNATAL DEVELOPMENT IN RATS

Growth rate, and adrenal and pituitary functions were followed in a group of developing postnatal rats. This was accomplished by direct hormone estimation in the gland and the circulating blood, or by releasing the hormone into the incubating medium, both at rest and following stimulation by exogenous ACTH or synthetic lysine vasopressin. Two-day-old adrenals produce steroids of the same type as those of adult rats, and they are able to respond to exogenous ACTH. Plasma corticosterone concentrations in 2-day-old rats are lower than in adults, but decline significantly towards day 11 and rise again at 16 days. The content of pituitary ACTH and CRF in the median eminence during the first two weeks is low, but from then on it increases. However, following exogenous lysine vasopressin, the pituitary of 2-day-old rats increases ACTH production and release. © 1968.