in vitro comparative study of the effect of Verapamil and aminophylline on the histamine induced contraction of the guinea pig tracheal chain

We investigated the inhibitory effect of verapamil, a calcium channel blocker, against histamine induced contraction [HIC] on the isolated guinea pig tracheal smooth muscle and compared it with aminophylline. Results showed that verapamil [1.1 and 2.2 X 10[-4]M] significantly inhibited HIC when incubated with the tissue before histamine challenge. Aminophylline was less effective when incubated with the tissue in equimolecular concentrations. In higher concentrations however, aminophylline [3.6 X 10[-4]M] significantly prevented HIC. As regards to the reversal of HIC, aminophylline was found to be more potent than verapamil