Maturation of nonadrenergic noncholinergic inhibitory system in normal and allergen-sensitized rabbits.
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)
Colasurdo
G N
GN
Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, University of Colorado School of Medicine, Denver 80206.
Loader
J E
JE
Graves
J P
JP
Larsen
G L
GL
D000367:Age Factors; D000485:Allergens / Q000276:immunology*; D000818:Animals; D004558:Electric Stimulation; D007114:Immunization; D009119:Muscle Contraction / Q000187:drug effects; D009433:Neural Inhibition; D015288:Neurokinin A / Q000494:pharmacology; D011817:Rabbits; D014132:Trachea / Q000294:innervation* / Q000502:physiology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D000485:Allergens; D014660:Vasoactive Intestinal Peptide; D015288:Neurokinin A