The interaction of pancuronium and vecuronium with cardiac muscarinic receptors

The interaction of vecuronium, a monoquaternary analogue of pancuronium, with the cardiac muscarinic receptors in canine hearts was investigatedin vitroby [3H] QNB binding assay and compared with that of pancuronium. Both pancuronium and vecuronium, which are nicotinic antagonists of competitive types, inhibited the binding of [3H] QNB to cardiac muscarinic receptors with values of IC50of 5.41 × 10‐7mol/l and 3.97 × 10‐6mol/l respectively. According to the Kd and Bmax values on the Scatchard plot, pancuronium, while not influencing the number of receptors, had a 3‐fold greater inhibitory effect than vecuronium on the affinity of the muscarinic receptors. The K1values of vecuronium and pancuronium showed that pancuronium had a 7.3‐fold greater affinity with the receptors than vecuronium. We concluded that vecuronium had a direct inhibitory action on the binding of [3H] QNR to the canine heart muscarinic receptors, but this action was much weaker than pancuronium.