Baroreflex control of arterial pressure under simulated micro gravity in dogs

本研究的目的是评估清醒犬RSNA的压力反射控制的急性修改。用苯肾上腺素（150 μ g iv.）升高和降低体动脉压时，同步记录颈动脉窦神经活动（CSNA）和RSNA。和硝普钠（300 μ g iv.），9只清醒犬。通过将获得的值拟合到S形方程来分析平均颈动脉压（Pmca）与RSNA之间的关系; Pmca=A1/（1+exp（A2（X-A3））+A4 ;其中X是RSNA ; A1，Pmca的范围; A2，Pmca-RSNA响应的增益; A3，中点压力（最大增益时的Pmca）; A4，Pmca的最小值。WI引起RSNA对颈动脉窦压力感受性反射控制的急性改变，因为A2增加了84%，A3减少了17 mmHg，而A1和A4保持不变。这些数据表明，WI导致Pmca-RSNA关系的显著偏移。分析Pmca-CSNA的关系类似于研究WI期间颈动脉窦压力感受器的性质。Pmca-CSNA曲线在对照期、WI期和恢复期均无变化，表明Pmca-RSNA关系的改变并不归因于颈动脉窦压力感受器性质的改变。结论：WI引起RSNA在颈动脉上压力感受器部位的压力反射控制的急性改变。

The purpose of the present study was to evaluate an acute modification of baroreflex control of RSNA in conscious dogs. Simultaneous recordings of carotid sinus nerve activity (CSNA) and RSNA were made during raising and lowering systemic arterial pressure by administrations of phenylephrine (150 ug iv.) and nitroprusside (300 ug iv.), respectively, in 9 conscious dogs. Relationship between mean carotid arterial pressure (Pmca) and RSNA was analyzed by fitting obtained values to a sigmoidal equation ; Pmca=A1/(1+exp(A2(X-A3))+A4 ; where X is RSNA ; A1, a range of Pmca ; A2, a gain of Pmca-RSNA response ; A3, a midpoint pressure (Pmca at the maximum gain) ; A4, a minimum value of Pmca. WI induced an acute modification of carotid sinus baroreflex control of RSNA, because A2 increased by 84%, A3 decreased by 17 mmHg, whereas A1 and A4 were constant. These data indicate that WI results in a leftward shift of the Pmca-RSNA relationship. The Pmca-CSNA relationship was analyzed similarly to study nature of carotid sinus baroreceptors during WI. The Pmca-CSNA curve did not change during control, WI and recovery periods, indicating that the modification of Pmca-RSNA relationship was not attributed to changes in a nature of carotid sinus baroreceptors. It is concluded that WI induces an acute modification of baroreflex control of RSNA at site of the supra-carotid baroreceptors.