Pontine cholinergic mechanisms enhance trigeminally evoked respiratory suppression in the anesthetized rat.
In the present study, we investigated in anesthetized rats the influences of the pontine rapid-eye-movement (REM) sleep center on trigeminally induced respiratory responses. We evoked the nasotrigeminal reflex by electrical stimulation of the ethmoidal nerve (EN5) and analyzed the EN5-evoked respiratory suppression before and after injections into the pontine reticular nuclei of the cholinergic agonist carbachol. After injections of 80-100 nl of carbachol (20 mM), we observed a decrease in respiratory rate, respiratory minute volume, and blood pressure but an increase in tidal volume. In those cases in which carbachol injections alone caused these REM sleep-like autonomic responses, we also observed that the EN5-evoked respiratory suppression was significantly potentiated. Unfortunately, carbachol injections failed to depress genioglossus electromyogram (EMG) effectively, because the EMG activity was already strongly depressed by the anesthetic alpha-chloralose. We assume that pontine carbachol injections in our anesthetized rats cause autonomic effects that largely resemble REM sleep-like respiratory and vascular responses. We therefore conclude that the observed potentiation of EN5-evoked respiratory suppression after carbachol might be due to REM sleep-associated neuronal mechanisms. We speculate that activation of sensory trigeminal afferents during REM sleep might contribute to pathological REM sleep-associated respiratory failures.
Dutschmann
M
M
Department of Animal Physiology, University of Tübingen, Auf der Morgenstelle 28, D-72076 Tübingen, Germany.
Herbert
H
H
D000758:Anesthesia; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D004558:Electric Stimulation; D004576:Electromyography; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D011149:Pons / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex / Q000187:drug effects / Q000502:physiology; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D012895:Sleep, REM / Q000187:drug effects / Q000502:physiology; D014276:Trigeminal Nerve / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*
D018727:Muscarinic Antagonists; D002217:Carbachol