迷走神经运动背核内心迷走神经元的GABA能突触前支配受谷氨酸能紧张性调控

谷氨酸能和GABA能支配是心迷走节前神经元(cardiac vagal neuron,CVN)的主要兴奋性和抑制性突触传入.在CVN的活动调节中,这两种支配是否有相互作用、以及如何相互作用目前尚不清楚.本研究用神经元逆行荧光染料标记法和电压膜片钳方法证明,谷氨酸NMDA型和非NMDA型受体拮抗剂AP5和CNQX在全脑片应用条件下,对疑核(nucleus ambiguus,NA)内CVN的GABA能突触前活动无明显影响,而对迷走神经运动背核(dorsal motor nucleus ofthe vagus,DMNX)内CVN的GABA能突触前活动有显著的抑制作用.这些观察结果提示支配迷走神经运动背核内CVN的GABA能神经元可能接受紧张性谷氨酸能支配,而支配疑核内CVN的GABA能神经元则没有这种紧张性谷氨酸能支配.疑核内和迷走神经运动背核内CVN的这种调节差异,是两个核团的CVN在心率和心功能调节中功能分工的可能机制之一.

GABAergic neurons innervating the preganglionic cardiac vagal neurons in the dorsal motor nucleus receive tonic glutamatergic control

The glutamatergic innervations and the GABAergic innervations are respectively the major excitatory and inhibitory inputs of preganglionic cardiac vagal neurons (CVNs). Whether and how these two kinds of innervations interact in the regulation of CVNs is unknown. Using retrograde fluorescent labeling of CVNs and voltage patch-clamp technique, we demonstrated that mixed global application of glutamatergic NMDA and non-NMDA antagonists AP5 and CNQX, while had no effect on the GABAergic synaptic events of the CVNs in the nucleus ambiguus (NA), significantly decreased the GABAergic synaptic events of the CVNs in the dorsal motor nucleus of the vagus (DMNX). These results suggest that the GABAergic neurons preceding the CVNs in the DMNX receive tonic glutamatergic control, whereas the GABAergic neurons preceding the CVNs in the NA receive little, if any, glutamatergic innervations. This differential central regulation of the CVNs in the DMNX from those in the NA might be a possible mechanism that enables the CVNs in the DMNX play different roles from those in the NA in the parasympathetic control of heart rate and cardiac functions.