Ryan K L, Taylor W F, Bishop V S
Department of Physiology, The University of Texas Health Science Center, San Antonio, Texas 78284-7764, USA.
J Appl Physiol (1985). 1997 Dec;83(6):2091-7. doi: 10.1152/jappl.1997.83.6.2091.
The purpose of this study was to determine whether nonthermal baroreflexes arising from cardiopulmonary and/or arterial baroreceptors modulate rabbit ear blood flow (EBF) during hyperthermia. Intact and sinoaortic-denervated (SAD) rabbits were chronically instrumented with a Doppler ultrasonic flow probe for measurement of EBF velocity (kHz). During whole body heating in conscious rabbits, EBF and ear vascular conductance (EVC) increased as core temperature increased until maximal plateau levels of EBF and EVC were reached. The maximal plateau level of EVC attained during heat stress was lower in SAD than in intact rabbits. Subsequent intrapericardial administration of procaine at maximal EBF blocked cardiac afferents but did not alter EVC in either animal group. In a second experiment, ramp decreases in mean arterial pressure were produced by vena caval occlusion at maximal EBF. In intact rabbits, EBF and EVC decreased linearly as mean arterial pressure fell, but EBF and EVC did not decrease during vena caval occlusion in SAD rabbits. Thus neither pharmacological nor mechanical unloading of cardiac baroreceptors results in reflex vasoconstriction in the heat-stressed rabbit ear. However, baroreflexes arising from arterial baroreceptors may modulate EBF in heat-stressed rabbits.
本研究的目的是确定在体温过高期间，源自心肺和/或动脉压力感受器的非热压力反射是否会调节兔耳血流量（EBF）。完整和经窦主动脉去神经（SAD）的兔子长期植入多普勒超声血流探头，用于测量EBF速度（kHz）。在清醒兔子全身加热过程中，EBF和耳血管传导率（EVC）随着核心温度升高而增加，直到达到EBF和EVC的最大平台水平。热应激期间达到的EVC最大平台水平在SAD兔子中低于完整兔子。随后在EBF最大时心包内注射普鲁卡因阻断心脏传入神经，但两组动物的EVC均未改变。在第二个实验中，在EBF最大时通过腔静脉闭塞使平均动脉压呈斜坡式下降。在完整兔子中，EBF和EVC随着平均动脉压下降呈线性下降，但在SAD兔子腔静脉闭塞期间EBF和EVC并未下降。因此，无论是药物性还是机械性卸载心脏压力感受器，在热应激的兔耳中均不会导致反射性血管收缩。然而，源自动脉压力感受器的压力反射可能会调节热应激兔子的EBF。
