AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 6 1832-R1839, Copyright © 1994 by American Physiological Society
Descending pathways of powerful pressor response elicited by suprapontine cerebral ischemia in rabbits
J. Horiuchi and T. Takeuchi
Department of Physiology, Yamanashi Medical University, Japan.
We determined the magnitude of the pressor and sympathoexcitatory responses
elicited by suprapontine cerebral ischemia (SCI) and the descending
pathways in the rostral medulla mediating them. The suprapontine structures
of anesthetized and artificially ventilated rabbits were selectively
exposed to cerebral ischemia, by combined occlusions of basilar and common
carotid artery. SCI produced a pressor response of 78 +/- 9 (SE) mmHg and
an increase in renal sympathetic nerve activity of 289 +/- 21% compared
with preischemic levels. The magnitude of the pressor and
sympathoexcitatory response to SCI was comparable to those in response to
global cerebral ischemia. Microinjection of the neurotoxin kainic acid into
the pressor sites of the rostral ventrolateral medulla significantly (P
< 0.05) reduced the SCI pressor response to 34 +/- 11% of the prelesion
control response. Chemical lesions of the pressor sites in the rostral
medial and ventromedial medulla resulted in a significant decrease in the
pressor response to SCI to 78 +/- 12% of the control response. These
results indicate that the suprapontine structures play an important role in
the generation of the powerful pressor response elicited by cerebral
ischemia and that the pressor response to SCI is mediated by pressor
neurons in the rostral medulla.
