Journal of Applied Physiology, Vol 59, Issue 5 1521-1526, Copyright © 1985 by American Physiological Society

ARTICLES

Hindlimb muscular contraction reflexly decreases total pulmonary resistance in dogs

M. P. Kaufman, K. J. Rybicki and J. H. Mitchell

We have previously shown that contraction of the gracilis muscles of anesthetized dogs reflexly relaxes tracheal smooth muscle. We have also found that electrical stimulation of these afferents decreases total pulmonary resistance (TPR), a calculation that provides a functional index of airway caliber. Despite these findings, we have yet to show that muscular contraction reflexly decreases TPR. Therefore, in 11 alpha-chloralose-anesthetized dogs, we contracted the hindlimb muscles by electrically stimulating the L6-L7 ventral roots while measuring TPR breath by breath. We found that static contraction decreased TPR from 12.6 +/- 1.1 to 10.4 +/- 0.9 cmH2O X l-1 X s (P less than 0.05). This decrease was reflex in origin because it was prevented by section of the spinal roots innervating the working hindlimb. Repetitive twitch contractions (5 Hz) also reflexly decreased TPR, but the effect was smaller than that evoked by static contraction. The reflex decreases in TPR evoked by contraction were unaffected by propranolol but were abolished by atropine. We conclude that muscular contraction dilates the airways by a reflex mechanism whose efferent arm consists of a withdrawal of cholinergic input to airway smooth muscle.

This article has been cited by other articles:

				B. J. Canning Reflex regulation of airway smooth muscle tone J Appl Physiol, September 1, 2006; 101(3): 971 - 985. [Abstract] [Full Text] [PDF]

				M. A. Haxhiu, P. Kc, C. T. Moore, S. S. Acquah, C. G. Wilson, S. I. Zaidi, V. J. Massari, and D. G. Ferguson Brain stem excitatory and inhibitory signaling pathways regulating bronchoconstrictive responses J Appl Physiol, June 1, 2005; 98(6): 1961 - 1982. [Abstract] [Full Text] [PDF]

				C. T. Moore, C. G. Wilson, C. A. Mayer, S. S. Acquah, V. J. Massari, and M. A. Haxhiu A GABAergic inhibitory microcircuit controlling cholinergic outflow to the airways J Appl Physiol, January 1, 2004; 96(1): 260 - 270. [Abstract] [Full Text] [PDF]

				M. A. Haxhiu, P. Kc, B. Neziri, B. K. Yamamoto, D. G. Ferguson, and V. J. Massari Catecholaminergic microcircuitry controlling the output of airway-related vagal preganglionic neurons J Appl Physiol, May 1, 2003; 94(5): 1999 - 2009. [Abstract] [Full Text] [PDF]

				G. A. Fontana, T. Pantaleo, F. Lavorini, F. Bongianni, M. Mannelli, P. D. Bridge, and M. Pistolesi Handgrip-induced airway dilation in asthmatic patients with bronchoconstriction induced by MCh inhalation J Appl Physiol, November 1, 2002; 93(5): 1723 - 1730. [Abstract] [Full Text] [PDF]

				M. A. Haxhiu, B. K. Yamamoto, I. A. Dreshaj, and D. G. Ferguson Activation of the midbrain periaqueductal gray induces airway smooth muscle relaxation J Appl Physiol, August 1, 2002; 93(2): 440 - 449. [Abstract] [Full Text] [PDF]

				K. Ishida, Y. Sato, K. Katayama, and M. Miyamura Initial ventilatory and circulatory responses to dynamic exercise are slowed in the elderly J Appl Physiol, November 1, 2000; 89(5): 1771 - 1777. [Abstract] [Full Text] [PDF]

				C. A. Beyaert, J. M. Hill, B. K. Lewis, and M. P. Kaufman Effect on airway caliber of stimulation of the hypothalamic locomotor region J Appl Physiol, April 1, 1998; 84(4): 1388 - 1394. [Abstract] [Full Text] [PDF]