Sympathetic nerve-mediated release of ATP from the guinea-pig vas deferens is unaffected by reserpine

Abstract

The release of ATP from the guinea-pig vas deferens was measured using the luciferin-luciferase assay. The effects of reserpine, tetrodotoxin, 6-hydroxydopamine and guanethidine on this efflux were investigated. Reserpine, which produced extensive loss of noradrenaline (NA) (about 99%) and eliminated the second phase of the nerve-mediated contraction, failed to impair either ATP release from the vas deferens or the concomitant 'twitch' contraction; in fact both were increased. Therefore the neurotransmitter mediating the twitch cannot be NA, thus excluding the gamma-receptor hypothesis. Furthermore, since the release of ATP is unaffected by reserpine, it is unlikely that ATP is being released from smooth muscle as a consequence of the post-junctional actions of NA. Tetrodotoxin, 6-hydroxydopamine and guanethidine substantially reduced or abolished the release of ATP and both phases of the nerve-mediated response. To conclude, in the guinea-pig vas deferens, ATP co-released with NA from sympathetic nerves, mediates the twitch phase of the contraction and its underlying electrical events.