Inhibition of NO synthesis does not potentiate dynamic cardiovascular response to sympathetic nerve activity.
We examined whether the inhibition of nitric oxide (NO) synthesis potentiates the dynamic sympathetic regulation of the cardiovascular system through the baroreflex. In anesthetized rabbits, we imposed random pressure perturbations on the isolated carotid sinuses to evoke random changes in sympathetic nerve activity (SNA). We estimated the transfer functions from SNA to both aortic pressure (AoP) and heart rate (HR). The inhibition of NO synthesis by NG-monomethyl-L-arginine (L-NMMA, 40 mg/ kg) altered neither the transfer function from SNA to AoP nor that from SNA to HR. In contrast, sodium nitroprusside (3-6 micrograms.kg-1.min-1) significantly decreased the steady-state gain (40.3 +/- 11.7% of the control, P < 0.05) of the transfer function from SNA to AoP without affecting the HR responses. We conclude that the basal release of NO may have a role in the tonic blood pressure regulation, whereas it may not be involved in the dynamic sympathetic regulation of AoP or HR through the baroreflex.
Miyano
H
H
Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Osaka, Japan.
Kawada
T
T
Sugimachi
M
M
Shishido
T
T
Sato
T
T
Alexander
J
J
Sunagawa
K
K
D000818:Animals; D001011:Aorta / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D002346:Carotid Sinus / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006706:Homeostasis; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D011311:Pressoreceptors / Q000502:physiology; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000502:physiology*; D013997:Time Factors; D019323:omega-N-Methylarginine / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase