Hirasawa M, Nishihara M, Takahashi M
Department of Veterinary Physiology, Veterinary Medical Science, University of Tokyo, Japan.
Brain Res. 1996 Jun 17;724(2):186-90. doi: 10.1016/0006-8993(96)00306-x.
We recently reported that a train of episodic neural discharges within the ventromedial nucleus of the hypothalamus (VMH) associated with suppression of the circulatory system had been determined by monitoring multiple unit activity (MUA). Abrupt increases in neural activity (MUA volleys; 1 to 4 min in duration) accompanied transient decreases in heart rate (HR) and blood pressure (BP), and showed circadian rhythm, occurring every 15 to 30 min in the light phase but seldom in the dark phase. The present study was aimed to determine if neurons in the vasomotor area of the rostral ventrolateral medulla (RVL) are involved in this VMH-induced cardiovascular suppression. MUAs of the VMH and RVL were monitored simultaneously with HR and BP in urethane-anesthetized rats. In synchrony with each MUA volley in the VMH, spontaneous activity of RVL neurons significantly decreased, as well as HR and BP. These RVL neurons are most likely vasomotor neurons because MUA of the RVL was attenuated by baroreceptor reflex activation, and electrical stimulation of these cells through the MUA recording electrodes produced pressor responses. These data suggest that VMH neurons that show a train of episodic discharges suppress the circulatory system at least in part by inhibiting the excitability of vasomotor neurons in the RVL.
我们最近报道，通过监测多单位活动（MUA）确定，下丘脑腹内侧核（VMH）内一连串与循环系统抑制相关的阵发性神经放电。神经活动突然增加（MUA群峰；持续1至4分钟）伴随着心率（HR）和血压（BP）的短暂下降，并呈现昼夜节律，在光照期每15至30分钟出现一次，而在黑暗期很少出现。本研究旨在确定延髓头端腹外侧区（RVL）的血管运动区域中的神经元是否参与这种VMH诱导的心血管抑制。在乌拉坦麻醉的大鼠中，同时监测VMH和RVL的MUA以及HR和BP。与VMH中的每个MUA群峰同步，RVL神经元的自发活动以及HR和BP均显著下降。这些RVL神经元很可能是血管运动神经元，因为RVL的MUA通过压力感受器反射激活而减弱，并且通过MUA记录电极对这些细胞进行电刺激会产生升压反应。这些数据表明，表现出一连串阵发性放电的VMH神经元至少部分地通过抑制RVL中血管运动神经元的兴奋性来抑制循环系统。
