Neurosecretion Following Hypophysectomy

Elucidation of the various factors controlling the pituitary gland has been a major problem of science for many years. Harris( 1 ) has admirably reviewed the literature concerning the neural control of the hypophysis. His statement. “The pars distalis of the pituitary may in general terms be described as a gland under nervous control but lacking a nerve supply,” most aptly phrases one of the oldest problems of neuroendocrinology, and the same statement may well be extended to parts of the hypothalamico-hypophyseal system other than the pars distalis. However, a careful survey and analysis of the literature reveals that in addition to a direct neural control via nerve fibers at least three additional controlling or influencing mechanisms are known or postulated. They are: (A) a hypothalamico-hypophyseal portal system( 2 - 5 ); (B) the reciprocal reactions and related functions of parts of the hypophysis to the other endocrine glands (literature too numerous to list); (C) and last, the fact that secretory material elaborated by the hypothalamic neurons may pass to the hypophysis via neurons or by way of the perineuronal spaces( 6 , 7 ).

Although Scharrer and co-investigators have thoroughly covered the morphological aspects of neuroasecretion, extremely little or virtually no experimental observation has been undertaken in the field of neurosecretion. This is especially true in the vertebrates. Speidel( 8 ) conducted some of the earliest experiments on neuro-secretion, using skates as an experimental animal, with negative results. The only positive evidence so far published regarding the relationship of neurosecretion to any other physiological processes of the vertebrate has been offered by Drager( 9 ). A full report of this work with additional experimental evidence is in preparation.

In certain neuro-endocrine studies of the tropical indigo snake, Spilotes corals, the animals were hypophysectomized according to a method described previously( 10 ), and following hypophysectomy the empty sella turcica was packed with fibrin foam.