Pre- and postjunctional muscarinic receptor subtypes in the vas deferens of rat

• 1.1. A pharmacological study of the pre- and postjunctional muscarinic receptors of the isolated rat vas deferens was carried out using more selective agonists and antagonists.
• 2.2. The prejunctional receptor was characterized on electrically stimulated preparations, while the postjunctional receptor was studied on vasa deferentia without stimulation.
• 3.3. The results indicate that atropine exhibited a similar affinity for the two populations of muscarinic receptor subtypes of this tissue.
• 4.4. 4-DAMP was able to differentiate with high affinity a subtype located at postjunctional level which had pharmacological similarities with the M₃-ACh subtype and with low affinity a subtype located at prejunctional level.
• 5.5. The selective M₁-ACh agonist McN-A-343 was not able to activate the postjunctional receptor, but showed a similar affinity to ACh for the prejunctional one.
• 6.6. At present, the prejunctional receptor can be considered as an atypical M₁-ACh subtype based on the results obtained with the selective drugs available.