THE EFFECT OF DEHYDRATION, STARVATION, AND PITRESSIN INJECTIONS ON THYROID ACTIVITY IN THE RAT1

Abstract

ONE of the usual effects of severe stress in experimental animals is depression of the activity of the thyroid gland (1-6). In studies of the role that the hypothalamus plays in this response it has been demonstrated that section of the pituitary stalk prevents the usual thyroid inhibitory reaction to pain or restraint in the rabbit (7, 8). Pituitary stalk section will also prevent the usual discharge of adrenocorticotrophic hormone (ACTH) which follows “emotional stress” in the rabbit (7, 9) or rat (10). Taking into consideration the absence of secreto-motor nerves to the anterior pituitary gland (11) it has been postulated that both the thyroid inhibition and the increased adrenal cortical activity which are observed following “emotional” stress are brought about through the effects on the anterior pituitary gland of neurohumeral substances transmitted by way of the hypophysial portal vessels (8, 9, 12). The identity of these suspected neurohumors is not known at present, but a number of observations point to the possibility that the anti-diuretic hormone (ADH) or a substance closely associated with it in the neurohypophysis may be responsible for the release of ACTH in certain stressful conditions (13–18).