Journal of Applied Physiology, Vol 72, Issue 4 1362-1367, Copyright © 1992 by American Physiological Society

ARTICLES

Vagal modulation of respiratory muscle activity in awake dogs during exercise and hypercapnia

D. M. Ainsworth, C. A. Smith, B. D. Johnson, S. W. Eicker, K. S. Henderson and J. A. Dempsey
John Rankin Laboratory of Pulmonary Medicine, Department of Preventive Medicine, School of Medicine, University of Wisconsin, Madison 53705.

Using chronically instrumented awake tracheotomized dogs, we examined the contributions of vagal feedback to respiratory muscle activities, both electrical and mechanical, during normoxic hypercapnia (inspired CO2 fraction = 0.03, 0.04, 0.05, and 0.06) and during mild treadmill exercise (3, 4.3, and 6.4 km/h). Cooling exteriorized vagal loops eliminated both phasic and tonic mechanoreceptor input during either of these hyperpneas. At a given chemical or locomotor stimulus, vagal cooling caused a further increase in costal, crural, parasternal, and rib cage expiratory (triangularis sterni) muscles. No further change in abdominal expiratory muscle activity occurred secondary to vagal cooling during these hyperpneas. However, removal of mechanoreceptor input during hypercapnia was not associated with consistent changes in end-expiratory lung volume, as measured by the He-N2 rebreathe technique. We conclude that during these hyperpneas 1) vagal input is not essential for augmentation of expiratory muscle activity and 2) decrements in abdominal expiratory muscle activity may be offset by increments in rib cage expiratory muscle activity and contribute to the regulation of end-expiratory lung volume.

This article has been cited by other articles:

				M. Tonkovic-Capin, E. J. Zuperku, E. A. Stuth, J. Bajic, Z. Dogas, and F. A. Hopp Effect of central CO2 drive on lung inflation responses of expiratory bulbospinal neurons in dogs Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2000; 279(5): R1606 - R1618. [Abstract] [Full Text] [PDF]