ANTIBODIES AGAINST GM(1) GANGLIOSIDE AFFECT K+ AND NA+ CURRENTS IN ISOLATED RAT MYELINATED NERVE-FIBERS

High titers of anti-GM(1) ganglioside antibodies (anti-GM(1) antibodies) may be implicated in lower motor neuron disease. We studied the pathogenic role of anti-GM(1) antibody using the petroleum jelly-gap voltage clamp technique on isolated single myelinated rat nerve fibers. Anti-GM(1) antisera were obtained from rabbits immunized with GM(1) ganglioside. Extracellularly applied anti-GM(1) antisera without complement activity increased both the rate of rise and the amplitude of the K+ current elicited by step depolarization, with little effect on Na+ current. In the presence of active complement, however, anti-GM(1) antibodies decreased the Na+ current, and caused a progressive increase of nonspecific leakage current. Neither complement alone nor complement-supplemented antisera from which anti-GM(1) antibodies were depleted by affinity chromatography had any effect on ionic current. These observations indicate that anti-GM(1) antibodies themselves can uncover K+ channels in the paranodal region, while anti-GM(1) antibodies bound to the nodal membrane in the presence of complement may form antibody-complement complexes that block Na+ channels and disrupt the membrane at the node of Ranvier.