家兔主动脉神经低阈压力感受反射快速重调中枢过程的特征

40只家兔,乌拉坦静脉麻醉。切断双侧主动脉神经(AN)、窦神经及迷走神经。以选择兴奋 AN 有髓传人纤维的条件刺激(0.02ms,50Hz,4—6V,5min)给予切断的 AN 中枢段,模拟导致低阈压力感受反射快速重调的保持压背景,借以诱导快速重调的中枢过程。实验表明:该中枢过程使 AN 有髓纤维传入所激发的压力感受反射降压效应衰减41.82%(P<0.01),肾交感神经活动抑制效应衰减19.31%(P

CHARACTERISTICS OF CENTRAL ACUTE RESETTING OF LOW THRESHOLD BAROREFLEX IN RABBIT'S AORTIC NERVE

Experiments were performed on 40 urethane-anesthetized rabbits. The aortic nerves, carotid sinus nerves and vagus nerves were cut, mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) were recorded. The conditional stimulation (0.02 ms, 50 Hz, 4-6 V, 5 min) of central cut end of aortic nerve was used to evoke the afferent A-fibers and to mimic the response of low threshold baroreflex to holding pressure, so as to induce the central process of acute resetting. It was observed that after conditional stimulation ceased 1 min, the MAP and RSNA for response to stimulation of myelinated aortic afferent was attenuated at 41.8 +/- 7.6% (P less than 0.01, n = 11) and 19.31 +/- 2.6% (P less than 0.05, n = 11), but both MAP and RSNA were not significantly changed for non-myelinated fibers. The result suggests that the characteristics of central resetting were dependent on the component of baroreflex afferent fibers. The central resetting of low threshold myelinated afferent activities was attenuated only on the baroreflex produced by myelinated afferent fibers.