Ezure K, Manabe M
Department of Neurobiology, Tokyo Metropolitan Institute for Neurosciences, Japan.
Exp Brain Res. 1989;74(3):501-11. doi: 10.1007/BF00247352.
In Nembutal-anesthetized, immobilized, and artificially ventilated cats, we studied the connectivity of medullary collaterals of bulbospinal inspiratory (BS-I) neurons in the ventral respiratory group (VRG). BS-I neurons which projected to the contralateral spinal cord were isolated extracellularly and intracellular recordings were made from the respiratory neurons in the contralateral VRG. The intracellular membrane potentials were averaged using extracellular spikes of the BS-I neurons as triggers (spike-triggered averaging method). Fast-rising and short-lasting depolarizing potentials locked to the triggering spikes were obtained and shown to be unitary EPSPs induced monosynaptically by the medullary collaterals of BS-I neurons. A total of 137 pairs were analyzed and unitary EPSPs were found in 11 pairs. Four BS-I neurons and 7 inspiratory vagal motoneurons received EPSPs from the medullary collaterals of BS-I neurons. These findings suggest that 1) BS-I neurons in the VRG drive medullary motoneurons of accessory respiratory muscles and phrenic or intercostal motoneurons simultaneously, 2) BS-I neurons on both sides synchronize via the excitatory connections, and 3) the augmenting firing pattern of BS-I neurons might partly be produced by this reexcitatory connection within the population of BS-I neurons.
在戊巴比妥麻醉、固定并进行人工通气的猫身上，我们研究了腹侧呼吸组（VRG）中延髓脊髓吸气（BS-I）神经元的延髓侧支的连接性。将投射到对侧脊髓的BS-I神经元在细胞外分离出来，并从对侧VRG中的呼吸神经元进行细胞内记录。利用BS-I神经元的细胞外动作电位作为触发信号（触发信号平均法）对细胞内膜电位进行平均。获得了与触发动作电位锁定的快速上升和短暂持续的去极化电位，并证明它们是由BS-I神经元的延髓侧支单突触诱导的单位兴奋性突触后电位（EPSP）。总共分析了137对，在11对中发现了单位EPSP。4个BS-I神经元和7个吸气性迷走运动神经元从BS-I神经元的延髓侧支接受了EPSP。这些发现表明：1）VRG中的BS-I神经元同时驱动辅助呼吸肌的延髓运动神经元以及膈神经或肋间运动神经元；2）两侧的BS-I神经元通过兴奋性连接实现同步；3）BS-I神经元的增强放电模式可能部分是由BS-I神经元群体内的这种再兴奋性连接产生的。
