Evaluation of contraction time and recovery period as a parameter in the calcium antagonistic action on the K(+)-depolarized rat duodenum.

Verapamil, nifedipine, phentolamine, tolazoline, gentamicin and neomycin inhibited calcium-induced contractions of K(+)-depolarized duodenum of rat by shifting the concentration-response curves to the right. Non-competitive inhibitions were observed with trifluoperazine, lidoflazine, procaine and tetracaine. Lanthanum behaved as a partial agonist in this preparation, while nitroprusside was ineffective. Contraction times in the presence of the antagonists and recovery time of the Ca2+ responses after the removal of the antagonists from the bathing medium were evaluated. From the findings, it is suggested that the contraction time and the time required for tissue recovery after removal of a Ca2+ antagonist are parameters making K(+)-depolarized rat duodenum a potential tool for the evaluation of the pharmacological effects of Ca2+ antagonists.