TY - JOUR
T1 - Upright tilt resets dynamic transfer function of baroreflex neural arc to minify the pressure disturbance in total baroreflex control
AU - Kamiya, Atsunori
AU - Kawada, Toru
AU - Yamamoto, Kenta
AU - Mizuno, Masaki
AU - Shimizu, Shuji
AU - Sugimachi, Masaru
PY - 2008/6
Y1 - 2008/6
N2 - Maintenance of arterial pressure (AP) under orthostatic stress against gravitational fluid shift and pressure disturbance is of great importance. One of the mechanisms is that upright tilt resets steady-state baroreflex control to a higher sympathetic nerve activity (SNA). However, the dynamic feedback characteristics of the baroreflex system, a hallmark of fast-acting neural control, remain to be elucidated. In the present study, we tested the hypothesis that upright tilt resets the dynamic transfer function of the baroreflex neural arc to minify the pressure disturbance in total baroreflex control. Renal SNA and AP were recorded in ten anesthetized, vagotomized and aortic-denervated rabbits. Under baroreflex open-loop condition, isolated intracarotid sinus pressure (CSP) was changed according to a binary white noise sequence at operating pressure ± 20 mmHg, while the animal was placed supine and at 60° upright tilt. Regardless of the postures, the baroreflex neural (CSP to SNA) and peripheral (SNA to AP) arcs showed dynamic high-pass and low-pass characteristics, respectively. Upright tilt increased the transfer gain of the neural arc (resetting), decreased that of the peripheral arc, and consequently maintained the transfer characteristics of total baroreflex feedback system. A simulation study suggests that postural resetting of the neural arc would significantly increase the transfer gain of the total arc in upright position, and that in closed-loop baroreflex the resetting increases the stability of AP against pressure disturbance under orthostatic stress. In conclusion, upright tilt resets the dynamic transfer function of the baroreflex neural arc to minify the pressure disturbance in total baroreflex control.
AB - Maintenance of arterial pressure (AP) under orthostatic stress against gravitational fluid shift and pressure disturbance is of great importance. One of the mechanisms is that upright tilt resets steady-state baroreflex control to a higher sympathetic nerve activity (SNA). However, the dynamic feedback characteristics of the baroreflex system, a hallmark of fast-acting neural control, remain to be elucidated. In the present study, we tested the hypothesis that upright tilt resets the dynamic transfer function of the baroreflex neural arc to minify the pressure disturbance in total baroreflex control. Renal SNA and AP were recorded in ten anesthetized, vagotomized and aortic-denervated rabbits. Under baroreflex open-loop condition, isolated intracarotid sinus pressure (CSP) was changed according to a binary white noise sequence at operating pressure ± 20 mmHg, while the animal was placed supine and at 60° upright tilt. Regardless of the postures, the baroreflex neural (CSP to SNA) and peripheral (SNA to AP) arcs showed dynamic high-pass and low-pass characteristics, respectively. Upright tilt increased the transfer gain of the neural arc (resetting), decreased that of the peripheral arc, and consequently maintained the transfer characteristics of total baroreflex feedback system. A simulation study suggests that postural resetting of the neural arc would significantly increase the transfer gain of the total arc in upright position, and that in closed-loop baroreflex the resetting increases the stability of AP against pressure disturbance under orthostatic stress. In conclusion, upright tilt resets the dynamic transfer function of the baroreflex neural arc to minify the pressure disturbance in total baroreflex control.
KW - Baroreflex
KW - Blood pressure
KW - Sympathetic nervous system
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U2 - 10.2170/physiolsci.RP004308
DO - 10.2170/physiolsci.RP004308
M3 - Article
C2 - 18471343
AN - SCOPUS:45349092939
SN - 1880-6546
VL - 58
SP - 189
EP - 198
JO - Journal of Physiological Sciences
JF - Journal of Physiological Sciences
IS - 3
ER -