DISCHARGE OF ADRENOCORTICOTROPHIC HORMONE IN THE ABSENCE OF NEURAL CONNECTIONS BETWEEN THE PITUITARY AND HYPOTHALAMUS

Abstract

The discharge of adrenocorticotrophic hormone (ACTH) from the pituitary in response to an acute stress (histamine phosphate, 1 mg. per 100 g. acting for 1 hr.) was studied in normal and stalk-sectioned male rats. Discharge of ACTH was measured by the depletion of adrenal ascorbic acid. None of the completely hypophysectomized rats responded to histamine with a significant reduction in adrenal ascorbic acid. In contrast, the reduction in adrenal ascorbic acid in the stalk-sectioned rats given histamine was as marked as that in the control group similarly treated. The completeness of disruption of the neural connections between the pituitary and the hypothalamus was proven by (1) the absence of grossly visible connections between the pituitary and the brain, (2) polydipsia and polyuria and (3) the degeneration of the supra-optic nucleus. It is, therefore, concluded that the prompt release of adrenocorticotrophic hormone from the adenohypophysis in response to stress is not dependent on direct neural connections between the hypothalamus and the anterior pituitary. However, it does not rule out the possibility that the pituitary might be excited by a neurohumor carried through the hypophyseal portal system.