Agarwal S K, Gelsema A J, Calaresu F R
Department of Physiology, University of Western Ontario, London, Canada.
Am J Physiol. 1989 Aug;257(2 Pt 2):R265-70. doi: 10.1152/ajpregu.1989.257.2.R265.
Recent evidence suggests that neurons in the caudal ventrolateral medulla (CVLM) exert a tonic inhibition on the neurons in the rostral ventrolateral medulla (RVLM) that are essential for the maintenance of arterial pressure (AP). To test the hypothesis that selective activation of cell bodies in the CVLM can inhibit the discharge of neurons in the RVLM, activity from 88 neurons in the RVLM was recorded extracellularly while 2-30 nl sodium glutamate (Glu; 0.15 M) were microinjected into depressor sites of the CVLM of urethan-anesthetized male Wistar rats. Results obtained from spontaneously breathing and artificially ventilated rats were essentially similar and are presented together. Twenty-five neurons were characterized as cardiovascular because they were inhibited by baroreceptor activation and showed rhythmicity of their spontaneous activity in synchrony with the cardiac cycle. Activation of cell bodies in the CVLM inhibited the firing rate of 23 of these cardiovascular neurons and excited 2. The remaining 63 neurons could not be considered cardiovascular because they either were not barosensitive or lacked cardiac cycle-related rhythmicity. Injection of Glu into the CVLM inhibited 26 of these neurons, excited 22, and had no effect on 15. These results provide direct evidence for the existence of an inhibitory pathway from neurons located in the CVLM to cardiovascular neurons in the RVLM.
最近的证据表明，延髓尾端腹外侧区（CVLM）的神经元对延髓头端腹外侧区（RVLM）中维持动脉血压（AP）所必需的神经元施加持续性抑制作用。为了验证CVLM中细胞体的选择性激活能够抑制RVLM中神经元放电的假说，在对乌拉坦麻醉的雄性Wistar大鼠的CVLM降压位点微量注射2 - 30 nl谷氨酸钠（Glu；0.15 M）的同时，细胞外记录了RVLM中88个神经元的活动。从自主呼吸和人工通气的大鼠获得的结果基本相似，一并呈现。25个神经元被鉴定为心血管相关神经元，因为它们受到压力感受器激活的抑制，并且其自发活动与心动周期同步呈现节律性。CVLM中细胞体的激活抑制了这些心血管相关神经元中的23个的放电频率，兴奋了2个。其余63个神经元不能被视为心血管相关神经元，因为它们要么对压力不敏感，要么缺乏与心动周期相关的节律性。向CVLM注射Glu抑制了这些神经元中的26个，兴奋了22个，对15个没有影响。这些结果为从CVLM中的神经元到RVLM中的心血管神经元存在抑制性通路提供了直接证据。
