Barman S M, Gebber G L
Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824-1317, USA.
J Neurophysiol. 1997 Jan;77(1):65-75. doi: 10.1152/jn.1997.77.1.65.
This study was designed to answer three questions concerning rostral ventrolateral medullary (RVLM) and caudal medullary raphe (CMR) neurons with activity correlate to sympathetic nerve discharge (SND). 1) What are the proportions of RVLM and CMR neurons that have activity correlated to both the cardiac-related and 10-Hz rhythms in SND, to only the 10-Hz rhythm, and to only the cardiac-related rhythm? 2) Which of these cell types project to the spinal cord? 3) Do the outputs of the cardiac-related and 10-Hz rhythm generators converge at the level of bulbospinal neurons or their antecedent interneurons? To address these issues we recorded from 44 RVLM and 48 CMR neurons with sympathetic nerve-related activity in urethan-anesthetized cats with intact carotid sinus nerves, but sectioned aortic depressor and vagus nerves. Spike-triggered averaging, arterial pulse-triggered analysis, and coherence analysis revealed that the naturally occurring discharges of 24 of these RVLM neurons and 41 of these CMR neurons were correlated to both the 10-Hz and cardiac-related rhythms in inferior cardiac postganglionic SND. The discharges of the other neurons were correlated to only the 10-Hz rhythm (15 RVLM and 6 CMR neurons) or to only the cardiac-related rhythm (5 RVLM neurons and 1 CMR neuron) in SND. The time-controlled collision test verified that 16 of 18 RVLM and 31 of 34 CMR neurons with activity correlated to both rhythms were antidromically activated by stimulation of the white matter of the first thoracic (T1) segment of the spinal cord. In contrast, only 1 of 10 RVLM neurons and 0 of 4 CMR neurons with activity correlated to only the 10-Hz rhythm could be antidromically activated by stimulation at T1. Also 0 of 3 RVLM neurons with activity correlated to only the cardiac-related rhythm in SND were antidromically activated by spinal stimulation. These data show for the first time that bulbospinal sympathetic pathways emanating from the RVLM and CMR are comprised almost exclusively of neurons whose discharges are correlated to both the cardiac-related and 10-Hz rhythms in SND. Moreover, the data support the hypothesis that the outputs of the cardiac-related and 10-Hz rhythm generators converge on RVLM and CMR bulbospinal neurons rather than on their antecedent interneurons. Finally, the data demonstrate that a substantial proportion of RVLM neurons and a small group of CMR neurons with activity correlated to SND do not project to the thoracic spinal cord. Their discharges were correlated to only one of the rhythms in SND. Their axonal trajectories and functions are unknown.
本研究旨在回答三个关于延髓头端腹外侧区（RVLM）和延髓尾端中缝核（CMR）神经元的问题，这些神经元的活动与交感神经放电（SND）相关。1）RVLM和CMR神经元中，其活动与SND中与心脏相关及10赫兹节律均相关、仅与10赫兹节律相关、仅与心脏相关节律相关的神经元比例分别是多少？2）这些细胞类型中哪些投射至脊髓？3）与心脏相关及10赫兹节律发生器的输出在延髓脊髓神经元或其前体中间神经元水平是否汇聚？为解决这些问题，我们在颈总动脉窦神经完整但主动脉减压神经和迷走神经切断的乌拉坦麻醉猫中，记录了44个RVLM和48个CMR中具有交感神经相关活动的神经元。触发尖峰平均法、动脉脉搏触发分析和相干分析显示，这些RVLM神经元中的24个以及CMR神经元中的41个的自然放电与低位心脏节后SND中的10赫兹和心脏相关节律均相关。其他神经元的放电仅与SND中的10赫兹节律（15个RVLM和6个CMR神经元）或仅与心脏相关节律（5个RVLM神经元和1个CMR神经元）相关。时间控制碰撞试验证实，18个RVLM神经元中的16个以及34个CMR神经元中的31个其活动与两种节律均相关的神经元，可通过刺激脊髓第一胸段（T1）的白质被逆向激活。相比之下，10个仅与10赫兹节律相关的RVLM神经元中只有1个，4个CMR神经元中无一个可通过T1刺激被逆向激活。同样，SND中仅与心脏相关节律相关的3个RVLM神经元中无一个可通过脊髓刺激被逆向激活。这些数据首次表明，源自RVLM和CMR的延髓脊髓交感神经通路几乎完全由其放电与SND中与心脏相关及10赫兹节律均相关的神经元组成。此外，数据支持以下假设，即与心脏相关及10赫兹节律发生器的输出汇聚于RVLM和CMR延髓脊髓神经元而非其前体中间神经元。最后，数据表明，相当比例的RVLM神经元以及一小群与SND相关的CMR神经元并不投射至胸段脊髓。它们的放电仅与SND中的一种节律相关。它们的轴突轨迹和功能尚不清楚。
