Pre- and postsynaptic bradykinin responses in the rat vas deferens: Asymmetric distribution of the postsynaptic effect

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The application of bradykinin to isolated segments of the epididymal or prostatic portion of the rat vas deferens increased the basal muscular tension mainly of the epididymal portion of the organ. Upon low frequency transmural electrical stimulation, the epididymal and the prostatic end of the organ both reacted to the application of bradykinin with an increase of twitch height. The increase in muscular tension observed in the epididymal portion of the ductus was resistant to tetrodotoxin but obliterated by 1 microM verapamil or nifedipine. The augmentation of the magnitude of the electrically driven muscle twitches was blocked by tetrodotoxin but not affected by 1 microM verapamil or nifedipine. Preincubation of the segments of the ductus with 10 microM indomethacin significantly reduced the increase in basal muscular tension caused by low concentrations of bradykinin but did not affect the electrically driven muscle twitches. Results suggest the existence of bradykinin receptors in the nerve endings of the adrenergic terminals of the organ and in the smooth muscle membrane. Whereas the neurogenic response found in both segments of the organ was of equal magnitude, the musculotropic response was predominantly found in the epididymal half of the organ.