AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 2 476-R480, Copyright © 1994 by American Physiological Society
Aortic baroreceptors play a predominant role in the regulation of hindlimb vascular resistance in rats
B. H. Machado, L. G. Bonagamba, J. A. Castania and J. V. Menani
Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Brazil.
In previous studies using bilateral carotid occlusion in conscious freely
moving rats we suggested that aortic baroreceptors may play a more
important role in the regulation of hindlimb than in renal and mesenteric
vascular resistances. In the present study we performed electrical
stimulation of the aortic baroreceptor nerve and analyzed the changes in
mean arterial pressure and in hindlimb, renal, and mesenteric vascular
resistances. All the experiments were performed under urethan anesthesia.
Unilateral electrical stimulation (3 V, 2 ms, 50 Hz) of the aortic
baroreceptor nerve produced a fall in arterial pressure (-27 +/- 3 mmHg)
and an important reduction in hindlimb vascular resistance (-43 +/- 5%),
with an increase in renal (+3 +/- 14%) and mesenteric (+48 +/- 12%)
vascular resistances. Similar changes in arterial pressure as well as in
the resistance of the three vascular beds studied were also observed during
electrical stimulation of the aortic baroreceptor nerve in rats with
bilateral carotid baroreceptor denervation or in rats treated with
methylatropine. The data obtained with electrical stimulation indicated
that aortic baroreceptors play a more important role in the regulation of
blood flow in hindlimb than in renal and mesenteric vascular beds.
