Impairment of Neural Nitric Oxide-mediated Relaxation after Antigen Exposure in Guinea Pig Airways in vitro

Nitric oxide (NO), a neurotransmitter of inhibitory nonadrenergic noncholinergic (iNANC) nerves in airways, is a radical with a short half-life, and its function may be modified by airway inflammation. To test this hypothesis, we examined whether airway allergic inflammation affects iNANC responses mediated by NO in guinea pigs in vitro. Animals sensitized with ovalbumin (OA) were challenged with 0.03% OA (OA group) or saline (saline group) by inhalation on 3 consecutive days. On the day after the final challenge, iNANC responses elicited by electrical field stimulation (2 to 16 Hz) or relaxation responses to 3-morpholinosydnonimine (SIN-1), 10− 8 to 10− 4 M, were obtained in the tracheal strips precontracted by histamine (3 × 10− 6 M) in the presence of atropine and propranolol (both 10− 6 M). The iNANC responses of the OA group were significantly attenuated compared with those of the saline group (p < 0.05), and the inhibitory effect of a NO synthase (NOS) inhibitor, Nω-nitro-l-arginine methyl ester, on...