Microdialysis of cat pons reveals enhanced acetylcholine release during state-dependent respiratory depression.
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.
Lydic
R
R
Department of Anesthesia, Pennsylvania State University College of Medicine, Hershey 17033.
Baghdoyan
H A
HA
Lorinc
Z
Z
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002217:Carbachol / Q000494:pharmacology*; D002415:Cats; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003956:Dialysis / Q000295:instrumentation / Q000379:methods; D008297:Male; D011149:Pons / Q000187:drug effects / Q000502:physiology*; D012119:Respiration / Q000187:drug effects / Q000502:physiology*; D012154:Reticular Formation / Q000502:physiology*; D012890:Sleep; D012895:Sleep, REM / Q000187:drug effects; D014851:Wakefulness
D002217:Carbachol; D000109:Acetylcholine