Fig. 2. Competitive displacement of ³H-QNB by cisatracurium in membranes prepared from Chinese hamster ovary cells expressing the M2 or M3 muscarinic receptor. Cisatracurium has a higher affinity for the M2 versus  the M3 muscarinic receptor. However, the 50% inhibitory concentration value for the M2 muscarinic receptor falls to the far right of reported plasma concentrations. (n = 3 for M2 and M3, respectively.)