The affinity of atropine for muscarine receptors in human sphincter pupillae.
Concentration-dependent contractions in response to carbachol were determined on isolated pieces of human iris. Atropine competivtively antagonized the effect of carbachol. An apparent dissociation equilibrium constant of 0.4--0.7 nM was estimated for the muscarine receptor-atropine complex.
D001285:Atropine / Q000378:metabolism* / Q000494:pharmacology; D002217:Carbachol / Q000037:antagonists & inhibitors / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007498:Iris / Q000378:metabolism*; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000378:metabolism*; D011950:Receptors, Cholinergic / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000378:metabolism*
D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D001285:Atropine; D002217:Carbachol