The Role of Antidiuretic Hormone in Corticotrophin Release **

The possibility that the posterior lobe of the pituitary may provide the neuroglandular link for activation of the anterior lobe was entertained by Hensey and Markee as early as 1933 when they postulated that "the pathways from the hypothalamus must activate the posterior lobe of the hypophysis which in turn may exert an influence on the anterior lobe by hormonal transmission."' This relationship has become of more than theoretical interest since vascular links between the anterior and posterior pituitary glands have been demonstrated in the rat,'8 dog," rabbit, cat, guinea pig,'7 and man.' The functional significance of these interlobar vessels has been demonstrated by their ability to maintain the integrity of a significant volume of anterior pituitary following infarction of the stalk of the anterior lobe in the rat, sheep, goat, baboon, rhesus monkey, and man.10 At the present time, evidence has been advanced to demonstrate a role of the neurohypophysis in the control of luteotrophic,' thyrotrophic,'somatotrophic,1' and adrenocorticotrophic hormone release. The evidence that ACTH may be regulated by the neurohypophysis lies along three lines: (i) the administration of exogenous vasopressin results in ACTH discharge; (ii) ADH and ACTH are released or inhibited simultaneously; and (iii) the posterior pituitary is essential for the release of ACTH.