ACTIVATION OF ACTH RELEASE BY NEUROHYPOPHYSIAL PEPTIDES

Control of Adenohypophysis The proximity of the pituitary body to the brain led the earliest arlatomists to suggest tha t the pituitary was under the iilfluence of the brain (1). They visualized the gland as a funnel by which the pitui ta or slime of the brain was led into the nose. The pitui ta was considered to consist of the waste product of the change, which occurred in the verltricles of the brain, of vital into animal spirits. Nowadays, the pituitary glarld is still believed to be influenced by the brain, but in a way a t the same time more complicated and more subtle than that imagined by 16th century anatomists. There is no difficulty in considerirlg tha t the neurohypophysis is under nervous control, as the neurohypophysis is actually a part of the brain, and is connected to other parts of the brain by well-defined nerve tracts. However, in spite of claims to the contrary ( 2 ) , there seem to be no importarlt nervous connections to the adenohypophysis (3). On the other hand, there does exist a network of fine blood vessels in the hypothalamic area a t the base of the brain that coalesces into larger vessels leading down the pituitary stalk from the hypothalamus to the pituitary gland, where they once more break up to serve the blood sinuses in the adenohypophysis. This portal circulation, first described by Popa and Fielding in 1930 (4), is ideally suited to carry products of the hypothalamus directly to the adenohypophysis, and is the keystone of the theory tha t humoral agents from the hypothalamus control the function of the adeilohypophysis (3). Thus modern theory is strikingly similar to tha t of the ancients. The function of the adenohypophysis is to synthesize, store, and release a variety of peptidic hormones, which have profound influence on metabolism and function. These include ACTH (adrenocorticotrop(h)ic hormone, corticotrop(h) in), TSH (thyroid-stimulating hormone, thyrotrop(h) in), STH (somatotrop(h)in, growth hormone), the various gonadotrop(h) ins, and, although this is not a popular idea today, perhaps other powerful hormorlal agents. Each adenohypophysial hormoile is presumably controlled by a specific hypothalamic humor, elaborated in response to rippropriate ilervous