The adrenal cortex of the newborn rat reacts by enlarged nuclear size to an injection of ACTH given at birth. A similar change is induced by the stress due to formalin injection, but no change is observed following hydrocortisone. Daily administration of the same substances until the 4th postnatal day results in changes in the adrenal cortex similar to those seen in the adult animal. ACTH, hydrocortisone, and stress, administered as a single application on the 1st day of life, induce a decrease in nuclear size in the ventromedial and in the arcuate nuclei, presumably due to corticoid feed-back, while daily administration of these agents results in cellular atrophy. A growth in nuclear size is observed in the same area, following adrenalectomy. On the basis of these findings it may be assumed that the adrenal cortex and hypothalamus of the newborn rat arc already functionally similar to those of the adult.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Endocrine and Autonomic Systems
- Cellular and Molecular Neuroscience