[Effect of verapamil, nicardipine and disodium cromoglycate on the bronchoconstrictor effects of histamine].

The effects of nicardipine, verapamil and sodium cromoglycate (SCG) on the increase in pulmonary airway resistance (Raw) and decrease in pulmonary dynamic compliance (C.Dyn.) induced by histamine (Hist) (3 and 30 micrograms x kg-1, i.v.) and acetylcholine (ACh) (3 and 30 micrograms x kg-1, i.v.) were investigated in anaesthetized guinea-pigs. The effects of these three agents on the contractile effects of Hist and ACh were tested on isolated tracheal preparations of the guinea pig. Nicardipine (0.3 and 1 mg . kg-1, i.v.) and verapamil (1 mg . kg-1, i.v.) as well as SCG (3 and 10 mg . kg-1, i.v.) partially but significantly inhibited the effects of Hist on Raw. These substances had no effect on Hist-induced decrease in C.Dyn. Nicardipine and verapamil had no effect on ACh-induced bronchoconstriction in vivo. SCG partially but significantly inhibited the effects of ACh (30 micrograms . kg-1) on Raw. In concentrations higher than 3 x 10(-6) M, nicardipine and verapamil inhibited the contractile effects of Hist and ACh on guinea-pig isolated trachea. SCG had no effect on this preparation. The results suggest that nicardipine, verapamil and SCG partially reduce the component of bronchoconstriction associated with stimulation of irritant receptor by Hist. However, the site and mechanism of action of Ca++-entry antagonists remain uncertain.