Potentiation by cholinoceptor agonists of contractions to field stimulation of rat vas deferens

Abstract

Cholinoceptor agonists (arecoline congruent to carbachol greater than acetylcholine greater than pilocarpine) potentiated contractions to field stimulation of rat vas deferens via the activation of an atropine-sensitive muscarinic receptor. The potentiating effect of carbachol was dependent on the level of calcium in the medium, being more potent at higher calcium concentrations. The potentiating effect of carbachol was more pronounced in the epididymal than in the prostatic segment but was not attenuated by prazosin, an alpha 1-adrenoceptor antagonist. Carbachol did not significantly modify the direct contractile effects of noradrenaline nor alter the field-stimulation-evoked release of noradrenaline from the epididymal vas deferens. It is concluded that the potentiating effect of cholinoceptor agonists on the contractions to field stimulation in the rat vas deferens was not a result of an enhancement of adrenergic neurotransmission.