DUAL CONTROL OF ADRENOCORTICOTROPHIN RELEASE^*

The role of hypothalamo‐hypophysial connexions in thyroid secretion

“…We have in several respects reached conclusions similar to those drawn by Fortier (1951) studying the dual control of adrenocorticotropin.…”

“…However, all available data of any significance indicate that such grafts do not regain normal activity unless they have been revascularized from the hypothalamo-hypophysial portal vessels (Harris & Jacobsohn, 1952;Jacobsohn, 1954). Nevertheless, viable and partially functional grafts of anterior pituitary may be useful for the study of some endocrine CURT VON EULER AND BJORN HOLMGREN mechanisms (Cheng, Sayers, Goodman & Swinyard, 1949;Fortier, 1951;Greer, Scow & Grobstein, 1953;Silberberg, Silberberg & Opdyke, 1954). Greer and his collaborators were the first to report on thyroid activity in hypophysectomized rats bearing anterior pituitary grafts as judged from thyroid cytology and uptake of 131I (Greer, 1952;Greer et al 1953;.…”

Depletion of pituitary corticotrophin by various stresses and by neurohypophysial preparations

“…Miallie-Voloss (1958) that a sound stimulus depresses the corticotrophin stores in the posterior lobe of the pituitary, but histamine does not. Contrary to the report of Mialhe-Voloss, sound stress did evoke a depletion of anterior lobe corticotrophin; however, the maximum decrease occurred later than that in the posterior lobe.The differential effect of different forms of stress on the two lobes of the pituitary supports the thesis of Fortier (1951) that two categories of stressors exist: neurotropic stimuli, such as sound, which impinge on the pituitary-adrenal axis solely via nervous pathways, and systemic stimuli, such as histamine, which are stressors by virtue of causing alteration in tissue chemistry and metabolism. The separation into two categories is not meant to imply that there is no overlap and that a systemic stressor may not have a neurotropic component as well.…”

“…On the other hand, stressors that alter tissue chemistry and metabolism may act via & humoral mechanism that by-passes the corticotrophin in the posterior lobe and only affects that in the anterior lobe. In this connexion it may be pointed out that the original division of stressors into the two categories was based partly on the observation that only the systemic stressors called forth signs of corticotrophin release from transplanted hypophysial tissue, in which only the anterior lobe tissue was viable (Fortier, 1951). Destruction of hypothalamic centres severs nervous connexions to the posterior lobe, and so may prevent the response to a neurotropic stress, but only more extensive lesions, which interfere with the blood supply to the adenohypophysis, may prevent response to systemic stresses, thus accounting for some of the different effects of hypothalamic lesions on various stresses (Fortier, Harris & McDonald, 1957).…”

The Role of the Adrenal Gland in Homeostasis

“…from the anterior lobe. Other observations, however, point to additional possibilities [Fortier, 1951]. Thus the response to, at least, certain forms of stress is abolished by producing bilateral lesions in the hypothalamus [de Groot and Harris, 1950], so that the receptors activated under these conditions lie in the central nervous system, which is found to exert some control over the anterior lobe.…”