AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 3 738-R746, Copyright © 1991 by American Physiological Society

ARTICLES

Cholinergic reticular mechanisms influence state-dependent ventilatory response to hypercapnia

R. Lydic, H. A. Baghdoyan, R. Wertz and D. P. White
Department of Anesthesia, Pennsylvania State University College of Medicine, Hershey 17033.

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.

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				C. A. Smith, K. S. Henderson, L. Xi, C.-M. Chow, P. R. Eastwood, and J. A. Dempsey Neural-mechanical coupling of breathing in REM sleep J Appl Physiol, December 1, 1997; 83(6): 1923 - 1932. [Abstract] [Full Text] [PDF]