Mechanisms of anti-bronchoconstrictive effects of eprozinol. II. In vivo studies on the guinea pig.

The possible interactions of the anti-asthmatic compound, eprozinol, with bronchoconstrictors and adrenergic agents were investigated in the anaesthetised guinea pig by means of the following techniques: (1) study of the inhibition of histamine- and serotonin-induced bronchospasm; (2) investigation of potentiation or antagonism between the anti-bronchoconstrictor effects of eprozinol and isoprenaline; (3) investigation of propranolol-induced blockade of the anti-bronchoconstrictor effects of eprozinol and several reference compounds. In the anaesthetised guinea pig, eprozinol (5 mge . kg-1), isoprenaline (2 micrograms . kg-1) and theophylline (15 mg . kg-1) administered intravenously cause a clear inhibition of the bronchospasm induced by intravenous perfusion of histamine or serotonin, with an intensity not significantly different for all three compounds. The anti-bronchoconstrictor activities of eprozinol and isoprenaline with regard to histamine are directly additive and show absolutely no interference with one another. Propranolol is without effect on in vivo anti-bronchoconstrictor activity of eprozinol on tracheal musculature. It is concluded that the mechanisms brought into play by eprozinol to exert anti-bronchoconstrictor and bronchorelaxant activity, are completely independent of the adrenergic system.