AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 6 751-R757, Copyright © 1983 by American Physiological Society
Hypothalamic lesions abolish cardiovascular responses to chronic saline ingestion
S. Sasaki and R. D. Bunag
In rats made to drink isotonic saline solution instead of water for 5 wk,
systolic pressure and heart rate, whether recorded indirectly from the tail
or directly from femoral catheters, rose slightly. When the ventromedial
hypothalamus was stimulated electrically, increases in arterial pressure
and sympathetic neural firing were larger in saline-drinking than in
water-drinking rats. By contrast, pressor responses to injections of
norepinephrine or tyramine were unaltered. Following bilateral destruction
of the ventromedial hypothalamus in other rats, none of the effects of
chronic saline ingestion was elicited. Although neither the site nor the
mechanism causing sympathetic overactivity has been determined, our results
are in accord with the interpretation that salt loading elevates blood
pressure, at least in part, by stimulating the ventromedial hypothalamus to
increase sympathetic activity.
