AJP - Heart and Circulatory Physiology, Vol 249, Issue 3 672-H680, Copyright © 1985 by American Physiological Society
Sympathetic regulation of cerebral blood flow during reflex hypertension
P. Lacombe, M. C. Miller and J. Seylaz
The cerebral circulatory effects of physiological stimulation of the
sympathetic nervous system have been examined in the present study. In
lightly anesthetized rabbits, reflex sympathetic activation was provoked by
bilateral sinus deafferentation and vagotomy. Regional cerebral blood flow
(CBF) was measured by the [14C]-ethanol technique and compared in paired
brain structures following unilateral superior cervical ganglionectomy. Two
subgroups of hypertensive rabbits were statistically distinguished. In the
first (19 of 28 rabbits), CBF in the innervated hemisphere was little
modified by hypertension but there was a significant side-to-side
difference in CBF between the hemispheres. In the second group (9 rabbits)
CBF was markedly increased by the systemic hypertension, and little
difference was noted between innervated and denervated hemispheres. We
demonstrate that, during acute hypertension, the superior cervical system
contributes to cerebrovascular autoregulation; this contribution varies
according to the brain region studied. In a subgroup of animals, little
sympathetic activity could be evidenced, and it is hypothesized that in
these rabbits a vasodilatory system was activated that counteracted the
myogenic, autoregulatory responses.
