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Nitric Oxide Synthase Inhibition Does Not Affect Regulation Of Muscle Sympathetic Nerve Activity During Head-Up Tilt, Jian Cui, Rong Zhang, Thad E. Wilson, Sarah Witkowski, Craig G. Crandall, Benjamin D. Levine

Exercise and Sport Studies: Faculty Publications

To test the hypothesis that systemic inhibition of nitric oxide (NO) synthase does not alter the regulation of sympathetic outflow during head-up tilt in humans, in eight healthy subjects NO synthase was blocked by intravenous infusion of NG-monomethyl-L-arginine (L-NMMA). Blood pressure, heart rate, cardiac output, total peripheral resistance (TPR), and muscle sympathetic nerve activity (MSNA) were recorded in the supine position and during 60° head-up tilt. In the supine position, infusion of L-NMMA increased blood pressure, via increased TPR, and inhibited MSNA. However, the increase in MSNA evoked by head-up tilt during L-NMMA infusion (change in burst rate: 24 ± …