AJP - Heart and Circulatory Physiology, Vol 258, Issue 3 729-H733, Copyright © 1990 by American Physiological Society
Cerebral blood flow during fastigial pressor response in cats
J. L. Williams, M. A. Murray, K. A. Schalk and D. D. Heistad
Department of Internal Medicine, Cardiovascular Center, University of Iowa College of Medicine, Iowa City 52242.
We tested the hypotheses that electrical stimulation of the fastigial
nucleus increases cerebral blood flow by a dilator mechanism, impairs
autoregulation during increases in arterial pressure, and attenuates
increases in cerebral blood flow during acute hypertension by activation of
sympathetic nerves. Cerebral blood flow was measured with microspheres in
anesthetized cats during control and moderate or severe hypertension
produced by stimulation of the rostral fastigial nucleus. Cervical
sympathetic nerves to one cerebral hemisphere were cut to compare responses
in the innervated and denervated hemispheres. Fastigial stimulation at a
level that raised arterial pressure from 94 +/- 10 (mean +/- SE) to 133 +/-
6 mmHg had no significant effect on cerebral blood flow. Autoregulation was
preserved because cerebral vascular resistance increased approximately 40%
during the fastigial pressure response. When mean arterial pressure was
raised to 189 +/- 9 mmHg by stimulation of the fastigial nucleus, cerebral
blood flow increased similarly in the denervated hemisphere and the
hemisphere with intact sympathetic nerves. We conclude that stimulation of
the fastigial nucleus in cats does not have a direct dilator effect on
cerebral vessels, does not impair autoregulation during moderate
hypertension, and does not attenuate increases in cerebral blood flow
during severe hypertension by activation of sympathetic pathways.
