COMPARISON OF ACTIONS OF PAPAVERINE, ASPAMINOL AND ISOPRENALINE ON ISOLATED RAT UTERUS

Inhibitory responses of the isolated rat uterus to papaverine, Aspaminol and isoprenaline were potentiated by aminophylline that inhibits phosphodiesterase. The inhibitory responses to papaverine and isoprenaline were decreased by imidazole that stimulates phosphodiesterase activity, while the inhibitory response to Aspaminol was little influenced by imidazole. Papaverine strongly inhibited phosphodiesterase from the rat uterus, but Aspaminol did not influence phosphodiesterase activity. These results indicate that papaverine and isoprenaline are mediated through an increase of the intracellular level of cyclic AMP and also indicate that the inhibitory response of the rat uterus to Aspaminol is not concerned with the amount of intracellular cyclic AMP increased by inhibiting phosphodiesterase. Further, the results support the theory that there are two mechanisms for the so-called papaverine-like antispasmodics.