AJP - Heart and Circulatory Physiology, Vol 244, Issue 3 406-H412, Copyright © 1983 by American Physiological Society
Mechanisms of protection against stroke in stroke-prone spontaneously hypertensive rats
S. Sadoshima, D. W. Busija and D. D. Heistad
The purpose of this study was to examine mechanisms by which sympathetic
nerves protect against cerebral hemorrhage and ischemic infarction (i.e.,
"stroke") in stroke-prone spontaneously hypertensive rats (SHRSP). When
unilateral superior cervical ganglionectomy was performed in SHRSP at 1 mo
of age, development of cerebral vascular hypertrophy was inhibited and
stroke developed only in the denervated hemisphere in 79% of the rats (P
less than 0.05). Because "trophic" effects of sympathetic nerves on
vascular growth may be less in older animals, unilateral sympathetic
denervation was performed in SHRSP at 3 mo of age. The incidence of stroke
was similar in the innervated and denervated hemispheres. In another group
of rats that had unilateral ganglionectomy at 1 mo, we examined regulation
of cerebral blood flow (CBF) when the rats were 4-5 mo of age, before
neurologic signs of stroke. CBF, measured with microspheres, was similar in
the innervated and denervated hemispheres during control conditions and
during maximal vasodilatation produced by bicuculline. In contrast, when
mean arterial pressure was raised acutely, CBF increased more in the
denervated hemisphere than in the innervated hemisphere. We conclude that
1) in contrast to effects of denervation at 1 mo, sympathetic denervation
at 3 mo of age (when trophic effects are less) does not lead to stroke, and
2) chronic denervation impairs the cerebral vasoconstrictor response to
acute increases in arterial pressure.
