Acid-base balance in brain extracellular fluid (EDF) and control of breathing

本研究揭示了中枢化学感受器的动力学特性和定位的新发现.为了反复刺激中枢化学感受器，我们开发了一种技术，椎动脉注射二氧化碳饱和盐水去大脑，自主呼吸猫。注射诱发了对正在进行的呼吸活动的初始瞬时抑制，随后是随后的兴奋：初始抑制是由于血管伤害感受器的激活，随后的兴奋是由于中枢化学感受器的刺激（J. Appl. Physiol.）。2.应用该技术，我们研究了146个单位的延髓神经元非时相放电活动的变化。发现18个单位仅由刺激中枢化学感受器（即pH敏感神经元的可能候选者）兴奋，并且它们主要分布在腹侧呼吸组（VRG）神经元附近以及 关于我们 背侧区腹侧的孤束（ST），但数量较少（脑研究1988）。使用液膜pH微电极，我们发现髓内区域中ECF pH值转移到酸侧在同一时间过程中呼吸兴奋时，椎动脉中的CO2逐步提高。这些区域被发现与“pH敏感神经元的可能候选者”的区域重叠。上述区域显示由以下船只供应（通过Technovit）;小脑前下动脉、小脑后下动脉和基底动脉发出的一无名动脉，根据上述证据，我们推测中枢化学感受器由pH敏感神经元及其周围结构组成（毛细血管和神经胶质细胞）调节ECF pH，并且它们位于VRG附近和ST腹侧的背侧区，其由椎基底动脉系统灌注。少

The present project has revealed the following new findings on dynamic properties and locations of the central chemoreceptors.1. In order to stimulate repeatedly the central chemoreceptors, we developed a technique of vertebral arterial injections of CO2-saturated saline in decerebrated, spontaneously breathing cats. The injections evoked an initial transient inhibition of ongoing respiratory activity, followed by the subsequent excitation: the initial inhibition was due to activation of vascular nociceptors and the subsequent excitation due to stimulation of the central chemoreceptors (J. Appl. Physiol.).2. Applying this technique, we studied the changes in activity of medullary neurons (146 units) with non-phasic discharges. Eighteen units were found to be excited exclusively by stimulation of the central chemoreceptors (namely, possible candidates for pH-sensitive neurons), and they were distributed mainly in the vicinity of ventral respiratory group (VRG) neurons as well as in the … More dorsal area ventral to the solitary tract (ST), though less in number (Brain Res. 1988).3. Using liquid membrane pH microelectrodes, we found intramedullary regions in which ECF pH shifted to the acid side in the same time course as respiratory excitation when CO2 in the vertebral artery was raised in stepwise fashion. These areas were found to overlap with the regions of "possible candidates for pH-sensitive neurons"4. The regions described above were revealed to be supplied by the following vessels (by means of Technovit); the anterior inferior cerebellar artery, the Posterior inferior cerebellar artery and an unnamed artery arising from the basilar artery.Based upon the foregoing evidence, we have hypothesized that the central chemoreceptors would consist of pH-sensitive neurons and the surrounding structures (capillaries and glial cells) which regulate ECF pH, and that they are located in the vicinity of the VRG and in the dorsal area ventral to the ST, which were perfused by the vertebral basilar arterial system. Less