Agarwal S K, Calaresu F R
Department of Physiology, University of Western Ontario London, Canada.
Brain Res. 1992 Mar 6;574(1-2):320-4. doi: 10.1016/0006-8993(92)90833-u.
Recent evidence indicates that the cell bodies of vagal cardioinhibitory neurons are located principally in the external formation of the nucleus ambiguus (NA). As activation of baroreceptor afferent fibers projecting to the nucleus tractus solitarius (NTS) elicits a decrease in heart rate it is likely that there is a connection between the NTS and NA. To test the hypothesis that stimulation of the NTS can excite vagal preganglionic cardiomotor neurons (VPCN) in the NA, activity from 78 neurons in the NA was recorded extracellularly before and during stimulation of a depressor site in the NTS (1 Hz, 0.1 ms) in urethan anesthetized and artificially ventilated male Wistar rats. Sixteen neurons were characterized as vagal preganglionic cardiomotor neurons (VPCN) because they were excited by baroreceptor activation (1-3 micrograms phenylephrine i.v.) and showed rhythmicity of their spontaneous activity in synchrony with the cardiac cycle. Stimulation of the NTS increased the firing rate of all these VPCN. The remaining 62 neurons could not be considered as VPCN because they either had respiratory rhythmicity or were not sensitive to baroreceptor activation, or they were sensitive to baroreceptor activation but did not display cardiac cycle related rhythmicity. These results provide evidence for the existence of an excitatory pathway from NTS to vagal preganglionic cardiomotor neurons in the NA.
最近的证据表明，迷走神经心脏抑制神经元的细胞体主要位于疑核（NA）的外侧部。由于投射到孤束核（NTS）的压力感受器传入纤维的激活会引起心率下降，因此NTS与NA之间可能存在联系。为了验证刺激NTS可兴奋NA中迷走神经节前心脏运动神经元（VPCN）这一假设，在乌拉坦麻醉并人工通气的雄性Wistar大鼠中，于刺激NTS中的降压位点（1 Hz，0.1 ms）之前和期间，细胞外记录了NA中78个神经元的活动。16个神经元被鉴定为迷走神经节前心脏运动神经元（VPCN），因为它们被压力感受器激活（静脉注射1 - 3微克去氧肾上腺素）所兴奋，并且其自发活动与心动周期同步呈现节律性。刺激NTS增加了所有这些VPCN的放电频率。其余62个神经元不能被视为VPCN，因为它们要么具有呼吸节律性，要么对压力感受器激活不敏感，或者它们对压力感受器激活敏感但未表现出与心动周期相关的节律性。这些结果为存在从NTS到NA中迷走神经节前心脏运动神经元的兴奋性通路提供了证据。
