The inhibitory effect induced by delta9-tetrahydrocannabinol on the contractions of the isolated rat vas deferens.

To analyse the influence of delta9-Tetrahydrocannabinol (THC) on the effects induced by sympathomimetic, parasympathomimetic and direct spasmogenic drugs, the isolated rat vas deferens preparation was chosen. Instead of the usual emulsifying agents, we have used 1% ethanol (ET-OH) to keep the cannabinoids in homogeneous dispersion in the bath. THC exerted a non-competitive inhibition of noradrenaline and of acetylcholine responses but no synergistic action nor competitive antagonism was seen on the dose range used. BaCl2 was potentiated by ethanol and this effect was abolished by THC. The water soluble derivative SP 111 showed actions similar to those of THC on noradrenaline and acetylcholine responses. It did not affect BaCl2 contractions, indicating that the cannabinoid might act by depressing early events of membrane activation.