Neuroendocrine components in the regulation of blood pressure and renin secretion.

N EURALLY regulated variables that affect blood pressure include not only the rate of discharge in vasomotor and cardiac nerves, but the rate of secretion of adrenocorticotrophic hormone (ACTH), growth hormone, vasopressin, and renin. Adrenocorticotrophic hormone produces hypertension in sheep and some humans, and plays a significant role in the regulation of aldosterone secretion. Growth hormone does not appear to stimulate renin or aldosterone secretion, despite some claims to the contrary, but it does help maintain the sensitivity of the zona glomerulosa to stimuli that increase aldosterone secretion.' Vasopressin occupies a pivotal position in water and secondarily in electrolyte homeostasis, and there is some evidence that its secretion is inappropriately high in renal and deoxycorticosterone-salt hypertension.The relation of renin to hypertension is apparent. This paper is concerned primarily with the interactions between the nervous system and the renin-angiotensin system, with comments about vasopressin as it relates to renin. The secretion of vasopressin, ACTH and growth hormone are also discussed as they relate to the function of aadrenergic receptors in the brain. It is worth noting that the interactions between the nervous system and the renin-angiotensin system are multiple and complex. Not only is sympathetic output one of the main regulators of the release of renin from the kidney,' but the angiotensin II formed in the circulation by the action of renin and converting enzyme acts on the brain to increase water intake, increase the secretion of vasopressin and ACTH, and raise blood pressure. In addition, the brain may have a reninangiotensin system of its own. In this paper, the "brain renin-angiotensin system" is briefly reviewed,