Evidence for pharmacological similarity between alpha 2-adrenoceptors in the vas deferens and central nervous system of the rat.

Seven alpha 2-adrenoceptor antagonists with diverse chemical structures have been examined for their effects at alpha 2-adrenoceptors in the vas deferens and central nervous system of the rat. Antagonist potency assessed against the presynaptic alpha 2-adrenoceptor agonist action of clonidine in the isolated vas deferens (RX 781094 greater than Wy 26703 greater than yohimbine greater than rauwolscine greater than piperoxan greater than mianserin greater than RS 21361) was highly correlated with the ability of these drugs to displace saturable [3H]-RX 781094 binding from cerebral cortex membranes. Similarly, antagonist potency in the vas deferens was highly correlated with antagonist activity in reversing the centrally-mediated mydriasis induced by the selective alpha 2-adrenoceptor agonist, guanoxabenz, in pentobarbitone-anaesthetized rats. The results indicate that the presynaptic alpha 2-adrenoceptors in the vas deferens are pharmacologically similar to characterized these alpha 2-adrenoceptors in the central nervous system of the rat.