Respiratory motor responses to cranial nerve afferent stimulation in rats.
It was hypothesized that, because rats appear to lack a prominent disynaptic projection from the dorsal respiratory group to phrenic motoneurons (Phr), they would lack the short-latency excitation of Phr output seen in cats in response to stimulation of some cranial nerve afferents. Single-pulse superior laryngeal nerve (SLN) stimulation elicited a short-latency bilateral excitation of glossopharyngeal (IX) and hypoglossal (XII) nerves and an ipsilateral excitation of pharyngeal branch of vagus (PhX) in 67% of rats, but no excitation of Phr. Vagus (X) stimulation elicited a bilateral excitation of Phr and a predominantly ipsilateral excitation of IX and PhX. Single-pulse stimulation of SLN or X also elicited longer-latency, bilateral decreases in activity of all recorded nerves. Repetitive stimulation (50 Hz) of SLN or X suppressed inspiratory activity and prolonged expiration. Lung inflation (7.5 cmH2O) inhibited Phr and PhX activity; X stimulation inhibited Phr but prolonged PhX activity. In conclusion, rats predictably lack the SLN-induced short latency Phr excitation but exhibit other short latency reflexes for which the underlying circuitry is not clear.
Hayashi
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F
Department of Physiology, Northwestern University Medical School, Chicago, Illinois 60611-3008, USA.
McCrimmon
D R
DR
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D003679:Deglutition / Q000502:physiology; D004558:Electric Stimulation / Q000379:methods; D005930:Glossopharyngeal Nerve / Q000502:physiology*; D007002:Hypoglossal Nerve / Q000502:physiology*; D007823:Laryngeal Nerves / Q000502:physiology; D008168:Lung / Q000502:physiology; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D010791:Phrenic Nerve / Q000166:cytology / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012119:Respiration; D012132:Respiratory Muscles / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology