AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 3 766-R770, Copyright © 1991 by American Physiological Society
Microdialysis of cat pons reveals enhanced acetylcholine release during state-dependent respiratory depression
R. Lydic, H. A. Baghdoyan and Z. Lorinc
Department of Anesthesia, Pennsylvania State University College of Medicine, Hershey 17033.
Microinjection of cholinergic agonists and acetylcholinesterase inhibitors
into the medial pontine reticular formation (mPRF) causes a state that is
polygraphically similar to rapid-eye-movement (REM) sleep. Respiratory
studies of intact unanesthetized cats during this cholinergically induced
REM sleep-like state have shown that the same cholinoceptive pontine
reticular regions that mediate REM sleep can also cause state-dependent
respiratory depression. The present study investigated the hypothesis that
acetylcholine (ACh) release in the mPRF is increased during the respiratory
depression that accompanies the cholinergically induced REM sleep-like
state. Cats were implanted for polygraphic recording of sleep and
wakefulness and with guide tubes aimed for placing a microinjector in one
mPRF and a microdialysis probe in the contralateral mPRF. ACh release was
measured with high-performance liquid chromatography and electrochemical
detection. Compared with waking levels, ACh was significantly increased and
respiratory frequency was significantly decreased during the
carbachol-induced REM sleep-like state. These results support the
hypothesis that endogenous cholinergic neurotransmission in brain regions
known to regulate REM sleep can also cause state-dependent changes in
respiratory control.
