Lydic R, Baghdoyan H A, Wertz R, White D P
Department of Anesthesia, Pennsylvania State University College of Medicine, Hershey 17033.
Am J Physiol. 1991 Sep;261(3 Pt 2):R738-46. doi: 10.1152/ajpregu.1991.261.3.R738.
Breathing is impaired by the loss of wakefulness that accompanies sleep, certain comatose states, and anesthesia. Although state-dependent decrements in breathing and the ability to respond to hypercapnic stimuli are characteristic of most mammals, the neural mechanisms that cause state-dependent changes in respiratory control remain poorly understood. The present study examined the hypothesis that cholinergic mechanisms in the medial pontine reticular formation (mPRF) can cause state-dependent changes in breathing and in the hypercapnic ventilatory response (HCVR). Six cats were anesthetized with halothane and chronically instrumented for subsequent studies of breathing during wakefulness, non-rapid-eye-movement (NREM) sleep, rapid-eye-movement (REM) sleep, and during the REM sleep-like state caused by mPRF microinjections of carbachol or bethanechol. Minute ventilation was significantly decreased during the carbachol-induced REM sleep-like state (DCarb) compared with wakefulness. The HCVR in NREM, REM, DCarb, and after bethanechol was less than the waking HCVR. These results show for the first time that cholinoceptive regions in the mPRF can cause state-dependent reductions in normocapnic minute ventilation and in the ventilatory response to hypercapnia.
睡眠、某些昏迷状态以及麻醉所伴随的觉醒丧失会损害呼吸功能。尽管呼吸状态依赖性下降以及对高碳酸血症刺激的反应能力是大多数哺乳动物的特征，但导致呼吸控制出现状态依赖性变化的神经机制仍知之甚少。本研究检验了以下假设：脑桥内侧网状结构（mPRF）中的胆碱能机制可导致呼吸以及高碳酸通气反应（HCVR）出现状态依赖性变化。对6只猫用氟烷进行麻醉，并长期植入仪器，以便后续研究清醒、非快速眼动（NREM）睡眠、快速眼动（REM）睡眠以及mPRF微量注射卡巴胆碱或氨甲酰甲胆碱所引起的类似REM睡眠状态下的呼吸情况。与清醒状态相比，卡巴胆碱诱导的类似REM睡眠状态（DCarb）期间的分钟通气量显著降低。NREM、REM、DCarb以及氨甲酰甲胆碱给药后的HCVR均低于清醒时的HCVR。这些结果首次表明，mPRF中的胆碱能感受区域可导致正常碳酸血症时的分钟通气量以及对高碳酸血症的通气反应出现状态依赖性降低。
