Evaluation of different drugs in two models of immediate hypersensitivity

The effect of the calcium antagonists, verapamil, nicardipine and diltiazem, the two cromones, disodium cromoglycate and SM-857 (11-oxo-11H-pyrido[2,1-b]quinazoline-2-carboxylic acid), and the anthelmintic, diethylcarbamazine citrate, have been compared on the ovalbumin (OA)-induced contraction of the isolated trachea and longitudinal muscle-myenteric plexus (LM-MP) from sensitized guinea-pigs. The calcium antagonists prevented the OA-induced contractions in LM-MP and to a lesser degree the OA-induced contractions in trachea. Similar doses of SM-857 protected both tissues but neither cromoglycate (10(-5)M) nor diethylcarbamazine (10(-5)M) affected these contractions. The OA-induced contraction in trachea had a tonic phase that was not present in the LM-MP response. Only the calcium antagonists succeeded in relaxing this OA tonic component, diltiazem being the more potent. These results unmask different mechanisms of drug action on immediate hypersensitivity and specific sensibilities, depending on the kind of tissue.