Baroreceptor denervation prevents sympathoinhibition during angiotensin II-induced hypertension.
Arterial baroreflexes are well established to provide the basis for short-term control of arterial pressure; however, their role in long-term pressure control is more controversial. We proposed that if the sustained decrease in renal sympathetic nerve activity (RSNA) we observed previously in response to angiotensin II-induced hypertension is baroreflex mediated, then the decrease in RSNA in response to angiotensin II would not occur in sinoaortic-denervated (SAD) animals. Arterial pressure and RSNA were recorded continuously via telemetry in sham and SAD rabbits living in their home cages before, during, and after a 7-day infusion of angiotensin II (50 ng . kg(-1) . min(-1)). The arterial pressure responses in the 2 groups of rabbits were not significantly different (82+/-3 mm Hg sham versus 83+/-3 mm Hg SAD before angiotensin II infusion, and 101+/-6 mm Hg sham versus 100+/-4 mm Hg SAD day 6 of angiotensin II). In sham rabbits, there was a significant sustained decrease in RSNA (53+/-7% of baseline on day 2 and 65+/-7% on day 6 of the angiotensin II). On ceasing the angiotensin II, all variables recovered to baseline. In contrast, RSNA did not change in SAD rabbits with the angiotensin II infusion (RSNA was 98+/-8% of baseline on day 2 and 98+/-8% on day 6 of the angiotensin II infusion). These results support our hypothesis that the reduction in RSNA in response to a pressor dose of angiotensin II is dependent on an intact arterial baroreflex pathway.
Barrett
Carolyn J
CJ
Department of Physiology, University of Auckland, New Zealand. c.barrett@auckland.ac.nz
Guild
Sarah-Jane
SJ
Ramchandra
Rohit
R
Malpas
Simon C
SC
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D003714:Denervation; D006973:Hypertension / Q000139:chemically induced / Q000503:physiopathology*; D007668:Kidney / Q000294:innervation; D009433:Neural Inhibition / Q000187:drug effects; D011311:Pressoreceptors / Q000503:physiopathology*; D011817:Rabbits; D012849:Sinoatrial Node / Q000294:innervation; D012850:Sinus of Valsalva / Q000294:innervation; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D014662:Vasoconstrictor Agents; D000804:Angiotensin II