Henry J L, Sessle B J
Neuroscience. 1985 Mar;14(3):863-73. doi: 10.1016/0306-4522(85)90149-6.
Recent studies have implicated glutamate and substance P in synaptic transmission in the nuclei tractus solitarii and in central regulation of cardiorespiratory functions. Consequently, in chloralose-anaesthetized cats that were artificially ventilated, we examined the effects of the microiontophoretic application of both chemicals (and the substance P homologue, eledoisin-related peptide) on single neurones of the nuclei tractus solitarii implicated in the control of respiration and respiratory tract reflexes. These neurones were functionally identified as either respiratory neurones or presumed reflex interneurones, and showed functional properties comparable to those previously documented for each of these two types. The iontophoretic application of glutamate produced an excitation of rapid onset in 23 or 25 reflex interneurones tested, but the respiratory neurones showed a differential sensitivity: one type (n = 32) was "glutamate-sensitive" and showed rapid excitation with glutamate applications of less than 30 nA, the other type of respiratory neurone (n = 26) was termed "glutamate-insensitive" since it either showed excitation only with applications of 60 nA or more or showed no response even with currents up to 94 nA. Each neurone studied was clearly of one type or the other. Glutamate could increase the number of spikes per rhythmic burst and the burst duration of respiratory neurones, it facilitated evoked activity in the reflex interneurones and in those respiratory neurones having a superior laryngeal nerve or vagus nerve afferent input, and the magnitude of the excitatory responses to glutamate varied directly with the amount of ejecting current. Substance P and eledoisin-related peptide also had excitatory effects on respiratory neurones and reflex interneurones, but compared with glutamate-induced effects the excitation was slower in onset and more prolonged in after-discharge. Both rhythmic and evoked activity could be facilitated, and the magnitude of the effect varied directly with the magnitude of the ejecting current. In showing that both glutamate and substance P (and its analogue, eledoisin-related peptide) have excitatory effects on the activity of respiratory neurones and reflex interneurones, this study provides evidence suggesting that these neurones have receptors for these neural chemicals, supportive of a role for each chemical in the regulation of respiration and respiratory tract reflexes.
近期研究表明，谷氨酸和P物质参与孤束核的突触传递以及心肺功能的中枢调节。因此，在人工通气的氯醛糖麻醉猫中，我们研究了微量离子导入这两种化学物质（以及P物质同系物，eledoisin相关肽）对参与呼吸控制和呼吸道反射的孤束核单个神经元的影响。这些神经元在功能上被鉴定为呼吸神经元或推测的反射中间神经元，并且表现出与之前记录的这两种类型神经元相当的功能特性。对23或25个测试的反射中间神经元进行离子导入谷氨酸后，会迅速产生兴奋，但呼吸神经元表现出不同的敏感性：一种类型（n = 32）为“谷氨酸敏感型”，在施加小于30 nA的谷氨酸时表现出快速兴奋，另一种类型的呼吸神经元（n = 26）被称为“谷氨酸不敏感型”，因为它要么仅在施加60 nA或更高电流时才表现出兴奋，要么即使施加高达94 nA的电流也无反应。所研究的每个神经元显然属于这两种类型之一。谷氨酸可以增加呼吸神经元每个节律性爆发的动作电位数量和爆发持续时间，它促进反射中间神经元以及那些有喉上神经或迷走神经传入输入的呼吸神经元的诱发活动，并且对谷氨酸的兴奋性反应幅度与喷射电流的大小直接相关。P物质和eledoisin相关肽对呼吸神经元和反射中间神经元也有兴奋作用，但与谷氨酸诱导的效应相比，兴奋的起始较慢且后放电持续时间更长。节律性和诱发活动均可被促进，且效应的大小与喷射电流的大小直接相关。本研究表明谷氨酸和P物质（及其类似物eledoisin相关肽）对呼吸神经元和反射中间神经元的活动均有兴奋作用，为这些神经元具有这些神经化学物质的受体提供了证据，支持每种化学物质在呼吸和呼吸道反射调节中的作用。
