Verapamil enhances the non-adrenergic twitch response of rat vas deferens.
Verapamil (3 X 10(-6)-3 X 10(-5) M) enhanced the twitch contractions of the epididymal and prostatic portions of vas deferens stimulated at 0.1 Hz. This verapamil effect was essentially similar to those of diltiazem, D-600 and Bay K 8644. However, when stimulation at 2 Hz was used verapamil (3 X 10(-5) M) attenuated the contractions of the epididymal portion by half but still augmented those of the prostatic portion. Verapamil enhanced the reserpine- and prazosin-resistant component of the stimulation-induced contractions of both portions of the vas deferens. Yohimbine augmented the twitch response but attenuated the verapamil-augmented response. Verapamil did not augment norepinephrine- or tyramine-induced contractions whereas it augmented ATP-induced contractions of the prostatic portion but not of the epididymal portion. Verapamil increased the stimulation-evoked 3H-efflux from the vas deferens labelled with [3H]norepinephrine. It is suggested that verapamil augments non-adrenergic responses of both portions of the vas deferens by acting as a Ca agonist on the prejunctional site to increase the release of co-transmitter, or by acting on the postjunctional site to enhance the action of the substance released. Its effect in augmenting norepinephrine release is concluded not to contribute to the potentiating action.
D000818:Animals; D001341:Autonomic Nervous System / Q000187:drug effects* / Q000502:physiology; D004558:Electric Stimulation; D005711:Gallopamil / Q000494:pharmacology; D006892:Hydroxydopamines / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000378:metabolism; D016627:Oxidopamine; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D012110:Reserpine / Q000494:pharmacology; D014649:Vas Deferens / Q000187:drug effects / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology*; D015016:Yohimbine / Q000494:pharmacology
D006892:Hydroxydopamines; D015016:Yohimbine; D005711:Gallopamil; D012110:Reserpine; D016627:Oxidopamine; D014700:Verapamil; D009638:Norepinephrine; D011224:Prazosin