PREJUNCTIONAL AND POSTJUNCTIONAL MUSCARINIC RECEPTOR SUBTYPES IN THE VAS-DEFERENS OF RAT

1. A pharmacological study of the pre- and postjunctional muscarinic r eceptors of the isolated rat vas deferens was carried out using more s elective agonists and antagonists. 2. The prejunctional receptor was c haracterized on electrically stimulated preparations, while the postju nctional receptor was studied on vasa deferentia without stimulation. 3. The results indicate that atropine exhibited a similar affinity for the two populations of muscarinic receptor subtypes of this tissue. 4 . 4-DAMP was able to differentiate with high affinity a subtype locate d at postjunctional level which had pharmacological similarities with the M(3)-ACh subtype and with low affinity a subtype located at prejun ctional level. 5. The selective M(1)-ACh agonist McN-A-343 was not abl e to activate the postjunctional receptor, but showed a similar affini ty to ACh for the prejunctional one. 6. At present, the prejunctional receptor can be considered as an atypical M(1)-ACh subtype based on th e results obtained with the selective drugs available.