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

High titers of anti-GM(1) ganglioside antibodies (anti-GM(1) antibodie s) may be implicated in lower motor neuron disease. We studied the pat hogenic role of anti-GM(1) antibody using the petroleum jelly-gap volt age clamp technique on isolated single myelinated rat nerve fibers. An ti-GM(1) antisera were obtained from rabbits immunized with GM(1) gang lioside. Extracellularly applied anti-GM(1) antisera without complemen t activity increased both the rate of rise and the amplitude of the K current elicited by step depolarization, with little effect on Na+ cu rrent. In the presence of active complement, however, anti-GM(1) antib odies decreased the Na+ current, and caused a progressive increase of nonspecific leakage current. Neither complement alone nor complement-s upplemented antisera from which anti-GM(1) antibodies were depleted by affinity chromatography had any effect on ionic current. These observ ations indicate that anti-GM(1) antibodies themselves can uncover K+ c hannels in the paranodal region, while anti-GM(1) antibodies bound to the nodal membrane in the presence of complement may form antibody-com plement complexes that block Na+ channels and disrupt the membrane at the node of Ranvier.