Shapoval L N, Sagach V F, Pobegailo L S
Department of Circulation Physiology, A.A. Bogomoletz Institute of Physiology, Kiev, U.S.S.R.
J Auton Nerv Syst. 1991 Dec;36(3):159-72. doi: 10.1016/0165-1838(91)90040-a.
These studies were designed to provide information on both GABA influences on the neuronal structures within the rostral ventrolateral medulla (RVLM) involved in the cardiovascular control, and fine structure of the GABA-sensitive RVLM in cats. By electron microscopy, the S-type asymmetric junctions (believed to mediate excitation) as well as F-type symmetric junctions (thought to provide inhibition) were identified within the RVLM area examined. The axonal terminals thick with spherical electron-transparent synaptic vesicles, measuring about 50 nm in diameter and forming S-type synapses, were distributed within the entire area. Large numbers of axonal terminals forming the F-type synapses and filled with flattened synaptic vesicles with a longitudinal axis of around 60-80 nm were found at the site located 5-6 mm caudal to the trapezoid bodies. Both spherical electron-transparent and flattened synaptic vesicles could be found together with electron-dense vesicles averaging 80-160 nm in diameter. No axonal terminals containing only the latter type of vesicles were found within the area studied. Some axo-axo-dendritic F-S-type synapses were identified within the RVLM. Unilateral injection of GABA into the RVLM site located 2-5 mm caudal to the trapezoid bodies induced a dose-related fall in the systemic arterial pressure and inhibition of the renal nerve sympathetic activity, the most marked responses being found at the site 4-5 mm caudal to the trapezoid bodies. It also resulted in decrease of heart rate and myocardial contractility when injected into a distinct site, located 0-1.5 mm rostral to the outflow of the 12th cranial nerve roots. There was some laterality in GABA effects on heart rate and myocardial contractility following its injections into the RVLM on the left and right side. Injections of bicuculline into the GABA-sensitive RVLM site resulted in an increase in cardio-haemodynamic responses together with the enhancement of renal nerve sympathetic activity in a dose-related fashion. These results suggest that, in cats, GABA-sensitive sympathoexcitatory neuronal structures in the RVLM alter peripheral sympathetic vasomotor and cardiac nerve background activities through GABA action on the bicuculline-sensitive GABAa-receptors.
这些研究旨在提供有关γ-氨基丁酸（GABA）对参与心血管控制的延髓头端腹外侧区（RVLM）内神经元结构的影响，以及猫中对GABA敏感的RVLM精细结构的信息。通过电子显微镜，在所检查的RVLM区域内鉴定出了S型不对称突触（被认为介导兴奋）以及F型对称突触（被认为提供抑制作用）。轴突终末含有直径约50nm的球形电子透明突触小泡，形成S型突触，分布在整个区域。在位于梯形体尾侧5-6mm处发现大量形成F型突触并充满纵向轴约60-80nm扁平突触小泡的轴突终末。球形电子透明突触小泡和平扁突触小泡都可以与平均直径80-160nm的电子致密小泡一起发现。在所研究的区域内未发现仅含有后一种类型小泡的轴突终末。在RVLM内鉴定出了一些轴-轴-树突型F-S型突触。向位于梯形体尾侧2-5mm的RVLM部位单侧注射GABA会导致全身动脉压呈剂量相关下降，并抑制肾神经交感神经活动，在梯形体尾侧4-5mm处发现最明显的反应。当注射到位于第12对脑神经根部流出道头侧0-1.5mm的不同部位时，还会导致心率和心肌收缩力下降。GABA注射到RVLM的左侧和右侧后，其对心率和心肌收缩力的影响存在一定的侧别差异。向对GABA敏感的RVLM部位注射荷包牡丹碱会导致心脏血液动力学反应增加，并以剂量相关的方式增强肾神经交感神经活动。这些结果表明，在猫中，RVLM中对GABA敏感的交感兴奋神经元结构通过GABA对荷包牡丹碱敏感的GABAa受体的作用改变外周交感血管运动和心脏神经的背景活动。
