Membrane fusion of erythrocytes as a model study of the effects of muscle relaxants on presynaptic exocytosis.

Abstract

The exact mechanism by which synaptic vesicles fuse with the presynaptic nerve terminal membrane has not been determined. We therefore investigated the effects of muscle relaxants on membrane fusion using the human red blood cell as a model membrane. The kinetics of calcium-phosphate-induced membrane fusion were monitored continuously by noting the relief of fluorescence self-quenching of octadecyl-rhodamine B chloride (R18)-labeled and unlabeled membranes. The nondepolarizing muscle relaxants, vecuronium and pancuronium, inhibited membrane fusion of ghosts, inside-out vesicles (IOVs), and phosphatidylserine (PS)-loaded IOVs, whereas succinylcholine did not affect membrane fusion. The inhibitory effect of nondepolarizing muscle relaxants on membrane fusion suggests the prejunctional involvement of nondepolarizing muscle relaxants.