Journal of Applied Physiology, Vol 69, Issue 4 1336-1346, Copyright © 1990 by American Physiological Society

ARTICLES

Vagal innervation of guinea pig bronchial smooth muscle

B. J. Undem, A. C. Myers, H. Barthlow and D. Weinreich
Johns Hopkins University Asthma and Allergy Center, Baltimore, Maryland 21224.

We isolated the guinea pig right bronchus with the vagus nerves intact and evaluated the changes in isometric tension of the smooth muscle in response to nerve stimulation. Brief (10-s) trains of electrical field stimulation or vagus nerve stimulation caused a biphasic contraction: the "first phase" sensitive to atropine and the "second phase" sensitive to capsaicin. The two phases could be dissociated by adjusting the stimulus intensity; greater stimulus intensities (pulse durations or voltage) were required to evoke the capsaicin-sensitive phase. When stimulated at 30-min intervals, the magnitude of both phases of the contractions declined over a 2-h period of repeated stimulation; however, this was prevented by indomethacin. Stimulation of the left vagus nerve resulted in a monophasic contraction of the right bronchus, with little evidence of a capsaicin-sensitive phase. Blocking neurotransmission through the bronchial ganglion, as monitored by intracellular recording techniques, abolished the first-phase contraction but had no effect on the capsaicin-sensitive phase. Selective blockade of muscarinic M1 receptors had no effect on vagus nerve-mediated contractions. The results demonstrate that the left and right vagus nerves carry preganglionic fibers to the right bronchial ganglion. The right but not the left vagus nerve also carries capsaicin-sensitive afferent fibers that, when stimulated, result in a persistent contraction of the right bronchus. Finally, we provide functional and electrophysiological evidence supporting the hypothesis that capsaicin-sensitive afferent neurons communicate with postganglionic motoneurons within the bronchus.

This article has been cited by other articles:

				M. S. Hazari, J. H. Pan, and A. C. Myers Nerve growth factor acutely potentiates synaptic transmission in vitro and induces dendritic growth in vivo on adult neurons in airway parasympathetic ganglia Am J Physiol Lung Cell Mol Physiol, April 1, 2007; 292(4): L992 - L1001. [Abstract] [Full Text] [PDF]

				B. J. Canning, S. M. Reynolds, L. U. Anukwu, R. Kajekar, and A. C. Myers Endogenous neurokinins facilitate synaptic transmission in guinea pig airway parasympathetic ganglia Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2002; 283(2): R320 - R330. [Abstract] [Full Text] [PDF]

				M. J. CARR, N. M. SCHECHTER, and B. J. UNDEM Trypsin-induced, Neurokinin-mediated Contraction of Guinea Pig Bronchus Am. J. Respir. Crit. Care Med., November 1, 2000; 162(5): 1662 - 1667. [Abstract] [Full Text]

				J. J. P. Fontan, C. T. Diec, and C. R. Velloff Bilateral distribution of vagal motor and sensory nerve fibers in the rat's lungs and airways Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2000; 279(2): R713 - R728. [Abstract] [Full Text] [PDF]

				P. J. Barnes, K. F. Chung, and C. P. Page Inflammatory Mediators of Asthma: An Update Pharmacol. Rev., December 1, 1998; 50(4): 515 - 596. [Abstract] [Full Text] [PDF]

				M. Bard, S. Salmeron, C. Coirault, F.-X. Blanc, and Y. Lecarpentier Effects of initial length on intrinsic tone in guinea pig tracheal smooth muscle Am J Physiol Lung Cell Mol Physiol, December 1, 1998; 275(6): L1026 - L1030. [Abstract] [Full Text] [PDF]

				M. A. Mcalexander, A. C. Myers, and B. J. Undem Inhibition of 5-Lipoxygenase Diminishes Neurally Evoked Tachykinergic Contraction of Guinea Pig Isolated Airway J. Pharmacol. Exp. Ther., May 1, 1998; 285(2): 602 - 607. [Abstract] [Full Text]

				A. Fischer, W.-G. Forssmann, and B. J. Undem Nociceptin-Induced Inhibition of Tachykinergic Neurotransmission in Guinea Pig Bronchus, J. Pharmacol. Exp. Ther., May 1, 1998; 285(2): 902 - 907. [Abstract] [Full Text]