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Cholinergic reticular mechanisms influence state-dependent ventilatory response to hypercapnia
R Lydic1, H A Baghdoyan, R Wertz
1Department of Anesthesia, Pennsylvania State University College of Medicine, Hershey 17033.
The American Journal of Physiology
|September 1, 1991
Summary
Cholinergic mechanisms in the medial pontine reticular formation (mPRF) reduce breathing during sleep and anesthesia. This study shows mPRF stimulation causes state-dependent decreases in ventilation and the hypercapnic ventilatory response (HCVR).
Area of Science:
- Neuroscience
- Respiratory Physiology
Background:
- Breathing is impaired during sleep, coma, and anesthesia due to loss of wakefulness.
- State-dependent breathing changes and reduced responses to hypercapnia are common in mammals, but underlying neural mechanisms are unclear.
Purpose of the Study:
- To investigate if cholinergic mechanisms in the medial pontine reticular formation (mPRF) cause state-dependent changes in breathing and hypercapnic ventilatory response (HCVR).
Main Methods:
- Six cats were instrumented for breathing studies during wakefulness, NREM sleep, REM sleep, and a REM sleep-like state induced by mPRF microinjections.
- Studied minute ventilation and HCVR under various states, including carbachol-induced REM sleep-like state (DCarb).
Main Results:
- Minute ventilation was significantly lower in the DCarb state compared to wakefulness.
- HCVR was reduced in NREM, REM, DCarb, and after bethanechol administration compared to wakefulness.
Conclusions:
- Cholinergic regions within the mPRF can induce state-dependent reductions in resting ventilation.
- These findings demonstrate that mPRF cholinergic activity impairs the ventilatory response to hypercapnia, contributing to breathing impairment during reduced states of consciousness.