Muscarinic receptor subtypes in the bisected vas deferens of the rat.

1. The nature of muscarinic receptor subtypes in the isolated prostatic and epididymal segments of the vas deferens of the rat were studied. 2. Presynaptic receptors were characterized in segments under neurogenic transmural stimulation; postsynaptic receptors in segments without stimulation. 3. The present work suggests that the potency of ACh required to activate muscarinic receptors is higher in the prostatic than in the epididymal segment. 4. McN-A-343 was only able to induce dose-dependent contractions in the prostatic segment. 5. The pA2 value for 4-DAMP suggests that in the prostatic segment the postsynaptical ACh receptors seem to be pharmacologically similar to the ACh-M3 subtype. 6. Antagonism of the presynaptic ACh receptor subtype by pirenzepine supports the evidence that these receptors belong to the ACh-M1 subtype.