Cardiovascular effects of posterior hypothalamic stimulation in baroreflex-denervated rats.
The overall purpose of this study was to examine the effect of sinoaortic baroreceptor denervation (SAD) on the cardiovascular and sympathetic outflow responses to electrical stimulation of the posterior hypothalamus. In anesthetized rats that had undergone SAD 7-10 days before experimentation, electrical stimulation of the posterior hypothalamus elicited greater increases in mean arterial pressure, iliac vascular resistance, mesenteric vascular resistance, and lumbar sympathetic nerve activity than in sham-operated baroreceptor-intact animals. Similarly, the pressor effects of intravenous norepinephrine were also augmented in the baroreceptor-denervated group compared with the baroreceptor-intact group. When posterior hypothalamic and intravenous norepinephrine pressor stimuli, which produced equivalent pressor responses in sham-operated baroreceptor-intact animals, were compared in baroreceptor-denervated animals, the pressor effects of the central hypothalamic stimulus were enhanced to a greater degree than the norepinephrine pressor effects. These data provide evidence that arterial baroreceptor reflexes exert greater buffering of pressor stimuli initiated from the central nervous system compared with pressor responses due to peripheral vascular vasoconstrictor agents.
Barron
K W
KW
Department of Physiology and Biophysics, College of Medicine, University of Kentucky, Lexington 40536.
Heesch
C M
CM
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002320:Cardiovascular Physiological Phenomena; D003714:Denervation; D004558:Electric Stimulation; D007031:Hypothalamus / Q000502:physiology*; D007085:Ilium / Q000098:blood supply; D008161:Lumbosacral Region; D008297:Male; D008643:Mesentery; D009638:Norepinephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow; D013152:Splanchnic Circulation; D013564:Sympathetic Nervous System / Q000502:physiology
D009638:Norepinephrine