AJP - Regulatory, Integrative and Comparative Physiology, Vol 241, Issue 1 36-R43, Copyright © 1981 by American Physiological Society
Regional neurohypophyseal blood flow and its control in adult sheep
R. B. Page, D. J. Funsch, R. W. Brennan and M. J. Hernandez
Regional neurohypophyseal and cerebral blood flows were measured by the
radiolabeled microsphere technique in 30 adult sheep under light
barbiturate anesthesia. Regional blood flows were determined under basal
conditions. The responses of regional blood flow to alterations in arterial
PCO2 and to changes in arterial blood pressure wee also determined. In
addition, the relationship between regional neurohypophyseal blood flow and
neurosecretory activity as judged by plasma arginine vasopressin levels was
assessed. Under basal conditions median eminence blood flow averaged 461
ml.100 g-1.min-1 and did not significantly differ from neural lobe blood
flow (436 ml.100 g-1.min-1). Blood flow in the neurohypophysis was about 8
times cortical and 16 times white matter blood flow in these animals.
Median eminence and neural lobe blood flow proportionately increased far
less than regional cortical or white matter blood flow under conditions of
hypercarbia. With alteration of arterial blood pressure, regional
neurohypophyseal blood flow remained constant beyond the limits of cerebral
autoregulation. The neurohypophysis demonstrates a degree of blood flow
homeostasis that exceeds that of any other brain area studied. Although the
neurohypophysis is a diverticulum of the brain, its vascular system forms a
unique functional as well as a unique anatomic unit.
