[Ovalbumin sensitization affects nonadrenergic noncholinergic relaxation response on guinea-pig tracheal smooth...

We investigated the effects of anaphylactic challenge on nonadrenergic noncholinergic (NANC) relaxation response to electrical field stimulation (EFS) or to aminophylline in sensitized guinea pig tracheal smooth muscles. An anaphylactic challenge with ovalbumin (OA) reduced the relaxation response to EFS (20 V. 5 Hz. 300 pulse. duration 1 msec.), but the relaxation response to aminophylline was not affected by OA exposure. NG-monomethyl L-arginine, a nitric oxide (NO) synthesis inhibitor, reduced the relaxation response to EFS in the OA sensitized guinea pig. While the relaxation response to EFS on the sensitized guinea pig tracheal smooth muscle was significantly attenuated compared with that on the non-sensitized guinea-pig, there was no significant difference between the tracheal strip of OA challenge group and that of control group in sensitized guinea-pig under the existence of NO synthesis inhibitor. These results suggest that the attenuation of NANC relaxation response associated with sensitization plays an important role in airway hyperreactivity and is responsible for the decrease in NO amount.