AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 3 544-R554, Copyright © 1993 by American Physiological Society
Pedunculopontine stimulation alters respiration and increases ACh release in the pontine reticular formation
R. Lydic and H. A. Baghdoyan
Department of Anesthesia, College of Medicine, Pennsylvania State University, Hershey 17033.
The present study examined the hypothesis that cholinergic neurons in the
pedunculopontine tegmental nucleus (PPT) can cause the release of
acetylcholine (ACh) in the pontine reticular formation and contribute to
respiratory depression. In vivo microdialysis of the gigantocellular
tegmental field (FTG) was performed in 10 adult male cats while respiration
was being measured. In four intact, unanesthetized cats these measurements
were obtained during states of quiet wakefulness and during the rapid eye
movement (REM) sleeplike state caused by FTG microinjections of carbachol.
The results demonstrate a simultaneous time course of enhanced ACh release
in the FTG and respiratory rate depression. In six barbiturate-anesthetized
cats similar measurements were obtained while PPT regions containing
NADPH-positive neurons were electrically stimulated. PPT stimulation caused
increased ACh release in the FTG and caused respiratory rate depression.
Together, these findings are consistent with the hypothesis of a causal
relationship between ACh release in the FTG and respiratory depression.
