Abstract
Summary
It was demonstrated that the plasma corticosterone response to ACTH is extremely weak in the 7-day-old rat. The present results indicate that pretreatment with 2 IU of ACTH in a beeswax-oil suspension on day 5 of age resulted in a 7-day-old rat that is capable of responding to ACTH in a manner comparable to that seen in younger and older rats. It is concluded from these studies that the “biphasic pattern” seen in the neonatal rat (characterized by a depressed adrenal response at day 7) is due to a depressed ability of the adrenal cortex to respond to ACTH. The hypothesis is presented that the depressed ability of the adrenal cortex to respond is the result of a relative lack in circulating ACTH. It is suggested that decreased ACTH secretion is the result of a failure of CRF to get to the pituitary because the hypothalamic-pituitary system is not complete in the 7-day-old rat.
Get full access to this article
View all access options for this article.