Title

Influence of background vagal c-fiber activity on eupneic breathing pattern in anesthetized dogs

Department

Physical Therapy

Abstract

In 19 dogs anesthetized with xylazine and α-chloralose, we examined the influence of background vagal C-fiber activity on the 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 12 dogs, we examined the effect of vagal perineural capsaicin on the Hering-Breuer expiratory facilitatory inflation reflex, pulmonary chemoreflex, and breathing pattern (tidal volume and expiratory and inspiratory times). Neither the peak height nor integral of the A wave of the compound action potential was significantly affected. 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 tidal volume (0.399 ± 0.031 to 0.498 ± 0.058 liter; P < 0.05), expiratory time (3.62 ± 0.31 to 4.82 ± 0.68 s; P < 0.05), inspiratory time (1.49 ± 0.12 to 1.72 ± 0.17 s; P < 0.10) and total time per breath (5.11 ± 1.08 to 6.54 ± 0.82 s; 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.

Document Type

Article

Publication Date

1-1-1995

Publication Title

Journal of Applied Physiology

ISSN

8750-7587

Volume

79

Issue

2

DOI

10.1152/jappl.1995.79.2.600

First Page

600

Last Page

606

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