Respiratory motor responses to cranial nerve afferent stimulation
in rats.
Hayashi, F., and D. R. McCrimmon.
Department of Physiology, Northwestern University Medical School,
303 E. Chicago Ave., Chicago, Illinois 60611-3008
APStracts 3:0170R, 1996.
It was hypothesized that since rats appear to lack a prominent
disynaptic projection from the dorsal respiratory group (DRG) to
phrenic (Phr) motoneurons, 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, 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, a predominantly ipsilateral excitation of IX and
PhX. Single pulse stimulation of SLN or X 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.
Received 4 October 1995; accepted in final form 22 April 1996.
APS Manuscript Number R624-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96