The influence of background vagal c-fiber activity on eupneic
breathing pattern in anesthetized dogs.
Schelegle, Edward S., Jim K. Mansoor, and Jerry F. Green.
Department of Human Physiology, School of Medicine, University of
California, Davis, California 95616
APStracts 2:0203A, 1995.
In nineteen dogs anesthetized with xylazine and a-chloralose, we
examined the influence of background vagal C-fiber activity on
breathing pattern using a modified perineural capsaicin treatment. In
seven dogs we tested the efficacy of this treatment by recording
compound action potentials before and after capsaicin application. In
the remaining twelve dogs we examined the effect of vagal perineural
capsaicin on the Hering-Breuer Expiratory Facilitatory inflation
reflex, the pulmonary chemoreflex and breathing pattern (VT, TE and
TI). Neither the peak height nor integral of the A-wave of the
compound action potential were significantly effected. However, the
peak height and integral of the C-wave of the compound action
potential were significantly reduced. The myelinated fiber initiated
Hering-Breuer reflex remained intact after perineural capsaicin but
the C-fiber initiated pulmonary chemoreflex was abolished. Perineural
capsaicin increased VT (.399 .031 to .498 .058 liters; P<0.05), TE
(3.62 0.31 to 4.82 0.68 s; p<0.05), TI (1.49 0.12 to 1.72 0.17 s;
p<0.10) and Ttot (5.11 1.08 to 6.54 0.82; P<0.05). We conclude
that background vagal C-fiber activity exerts an inhibitory effect on
tidal volume and an excitatory effect on breathing frequency.
Received 11 October 1994; accepted in final form 21 March 1995.
APS Manuscript Number A1047-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.