Fig. 6. Inhibition of atropine (1 μm)–induced [³H]N-methylscopolamine (³H-NMS) dissociation from the human M3 muscarinic receptors in membranes prepared from Chinese hamster ovary-M3 cells by (  A ) rapacuronium, (  B ) gallamine, (  C ) vecuronium, and (  D ) rocuronium. Rapacuronium (50–100 μm), gallamine (100 μm), vecuronium (50–100 μm), and rocuronium (10–100 μm) each significantly inhibited atropine-induced ³H-NMS dissociation, demonstrating allosteric interactions with the M3 muscarinic receptor. Rapacuronium was the only relaxant studied that had allosteric interactions within clinically achieved concentrations. #  P < 0.01 compared with atropine alone; n = 6.