Muscarinic receptor subtype in isolated dog and monkey facial vein

Using the cannula inserting method, we investigated vascular responses to ACh and McN-A-343 (a M1-agonist) in isolated and perfused canine and simian facial veins in non-preconstricted conditions. ACh usually induced only a vasoconstriction, but McN-A-343 did not induce any significant vasoconstriction. It is concluded that canine and simian facial veins contain very few receptors of the muscarinic M1-subtype; and according to previous studies, these vessels have abundant M3-receptors.