The Pituitary-Adrenal Axis and Behavior

Abstract

In 1922, Uno noted that rats, following a six hour period of excitement, exhibited an increase in the weight of the pituitary gland. His finding led him to conclude that the pituitary gland is involved in the responsiveness of the organism to changes in the environment. In a whole series of subsequent experiments begun in 1936, Selye explored further components of this system of responsiveness to adverse environmental shifts. He observed that numerous conditions, such as surgical injuries, chronic pain and inflammation, drug administration and immobilization, caused an enlargement of the adrenal glands with an accompanying loss of lipids from the adrenal cortex. This reaction, which he called the “stress response” or “general adaptation syndrome”, requires the presence of hypothalamic centers and the pituitary gland for the release of the adrenocorticotrophic hormone (ACTH).