AJP - Lung Cellular and Molecular Physiology, Vol 268, Issue 2 251-L262, Copyright © 1995 by American Physiological Society
Respiratory nuclei share synaptic connectivity with pontine reticular regions regulating REM sleep
L. H. Lee, D. B. Friedman and R. Lydic
Department of Anesthesia, Pennsylvania State University, College of Medicine, Hershey 17033.
Injection of cholinomimetics into the medial pontine reticular formation
(mPRF) of intact, unanesthetized cat causes a rapid eye movement (REM)
sleep-like state and respiratory depression. The mPRF contains no
concentrations of respiratory neurons, and this study examined the
hypothesis that respiratory depression evoked from the mPRF is synaptically
mediated. The mPRF of conscious cats was injected with bethanechol to
define an mPRF zone causing state-dependent respiratory depression.
Bethanechol caused a 361% increase in the REM sleep-like state and a 37%
decrease in minute ventilation. Additional cats were injected with the
retrograde fluorescent tracers True Blue and either Fluoro-Gold or
Diamidino Yellow aimed for the cholinoceptive mPRF or for the pontine
respiratory group (PRG). After mPRF dye injection, 1) labeling was observed
in the PRG, dorsal respiratory group (DRG), and ventral respiratory group
(VRG); and 2) double-labeled cells were observed in the VRG and PRG. Dye
injections into the PRG produced contralateral and ipsilateral fluorescent
labeling of the mPRF, DRG, and VRG. Thus cholinoceptive regions of the mPRF
involved in REM sleep generation have reciprocal monosynaptic connections
with the PRG and receive monosynaptic projections from the DRG and VRG.
