Evidence that ATP does not act as a cotransmitter with noradrenaline in field-stimulated preparations of rat seminal vesicles.

Field stimulation (20 pulses, 60 V, 2 ms, 5-70 Hz) of the nerve terminals within the rat seminal vesicle produced monophasic contractions which were blocked by guanethidine 5 microM and phentolamine 1 microM, and minimal in tissues from rats pretreated with reserpine, but unaffected by repeated application of alpha,beta-methylene ATP. Field stimulation at 40 Hz led to the release of ATP (0.39 +/- 0.12 pmol/mg; n = 10). However neither ATP nor alpha,beta-methylene ATP 10 microM caused contraction of the tissue. We conclude that ATP does not act as a cotransmitter in preparations of rat seminal vesicle because P2-purinoceptors appear to be absent.