TY - JOUR
T1 - Nitric oxide synthase inhibition does not affect regulation of muscle sympathetic nerve activity during head-up tilt
AU - Cui, Jian
AU - Zhang, Rong
AU - Wilson, Thad E.
AU - Witkowski, Sarah
AU - Crandall, Craig G.
AU - Levine, Benjamin D.
PY - 2003/11
Y1 - 2003/11
N2 - 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 ± 4 bursts/min; change in total activity: 209 ± 36 U/min) was similar to that during head-up tilt without L-NMMA (change in burst rate: 23 ± 4 bursts/min; change in total activity: 251 ± 52 U/min, n = 6, all P > 0.05). Moreover, changes in TPR and heart rate during head-up tilt were virtually identical between the two conditions. These results suggest that systemic inhibition of NO synthase with L-NMMA does not affect the regulation of sympathetic outflow and vascular resistance during head-up tilt in humans.
AB - 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 ± 4 bursts/min; change in total activity: 209 ± 36 U/min) was similar to that during head-up tilt without L-NMMA (change in burst rate: 23 ± 4 bursts/min; change in total activity: 251 ± 52 U/min, n = 6, all P > 0.05). Moreover, changes in TPR and heart rate during head-up tilt were virtually identical between the two conditions. These results suggest that systemic inhibition of NO synthase with L-NMMA does not affect the regulation of sympathetic outflow and vascular resistance during head-up tilt in humans.
KW - Autonomic
KW - Baroreceptors
KW - Microneurography
KW - Nervous system
KW - Orthostatic
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U2 - 10.1152/ajpheart.01076.2002
DO - 10.1152/ajpheart.01076.2002
M3 - Article
C2 - 12842819
AN - SCOPUS:0142169978
SN - 0363-6135
VL - 285
SP - H2105-H2110
JO - American Journal of Physiology - Heart and Circulatory Physiology
JF - American Journal of Physiology - Heart and Circulatory Physiology
IS - 5 54-5
ER -