Effects of forskolin in rat vas deferens--evidence for facilitatory beta-adrenoceptors.

Forskolin inhibited the response to electrical field stimulation (0.1 Hz) and antagonised contractile responses to noradrenaline in the isolated rat vas deferens. The inhibition of the response to electrical stimulation (IC50 0.1 microM) was not affected by either propranolol or yohimbine. Both isoprenaline and forskolin enhanced the total tritium efflux during transmural stimulation of vas deferens which had been prelabelled with [3H]noradrenaline. These data provide evidence that beta-adrenoceptor stimulation enhances noradrenaline release in the vas deferens, although the postsynaptic relaxant effect on smooth muscle predominates in determining the net response. The data are consistent with a stimulation of adenylate cyclase in mediation of both presynaptic and postsynaptic effects of beta-adrenoceptor agonists in the vas deferens.