AJP - Lung Cellular and Molecular Physiology, Vol 267, Issue 6 739-L744, Copyright © 1994 by American Physiological Society

ARTICLES

Maturation of nonadrenergic noncholinergic inhibitory system in normal and allergen-sensitized rabbits

G. N. Colasurdo, J. E. Loader, J. P. Graves and G. L. Larsen
Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, University of Colorado School of Medicine, Denver 80206.

We investigated the functional existence of the nonadrenergic noncholinergic inhibitory (NANCi) system in developing rabbit airways in vitro. Furthermore, we evaluated the effect of parenteral exposure to a specific allergen (ragweed) on the maturation of this neural pathway. NANCi responses were studied on tracheal smooth muscle (TSM) segments obtained from normal and ragweed-sensitized New Zealand White rabbits at 1, 2, 4, and 12 wk of age. The TSM segments were removed and placed in tissue baths containing modified Krebs-Henseleit solution, atropine (1 x 10(-5) M), and propranolol (5 x 10(-6) M). After contraction with neurokinin A (1 x 10(-5) M), electrical field stimulation was applied at stimulation frequencies ranging from 5 to 30 Hz to determine the frequency that produced maximal relaxation. The NANCi response to EFS was measured and expressed as the mean (+/- SE) percent relaxation at 20 Hz, because this stimulation frequency gave the maximal NANCi response at each age studied. TSM segments obtained from control rabbits at 1 wk of age did not demonstrate a NANCi response at the frequencies of stimulation used. By contrast, a reproducible NANC relaxation was demonstrated in TSM from 2-, 4-, and 12-wk-old rabbits. The magnitude of this response was 27 +/- 4.7 (n = 10), 29 +/- 4.8 (n = 9), and 37 +/- 4% (n = 18), respectively. The same experiments performed on TSM segments obtained from ragweed-sensitized animals gave significantly decreased values of NANCi response. In 2-, 4-, and 12-wk-old rabbits, the NANCi responses were 11.5 +/- 3.4 (n = 9), 11 +/- 2 (n = 13), and 16 +/- 4.2% (n = 14).(ABSTRACT TRUNCATED AT 250 WORDS)

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