A tentative transmission mechanism for the twitch elicited in guinea-pig vas deferens by field stimulation.

The twitch response to nerve activity in the vas deferens does not behave as if it were adrenergic since it is enhanced by adrenoceptor blockers and often inhibited by noradrenaline and other sympathomimieic amines. Potassium (K+) ions have a strong reinforcing action on the twitch and easily restore it after blockade by lanthanum. The hypothesis is advanced that K+ ions have a transmitter function in the vas deferens and that K+ ions released in conjunction with the nerve stimulus may reach a concentration at the postsynaptic membrane sufficient to excite the muscle cell and produce a twitch.