Antibodies to GM1 ganglioside are found in some patients with the Guillain-Barré syndrome and multifocal motor neuropathy, and may alter neuronal excitability. We measured voltage-gated sodium channel (VGSC) function by 22Na+ influx in a motor neuronal cell line (NSC19) in which we demonstrated GM1 ganglioside and tetrodotoxin-sensitive VGSC function. We were unable to detect any effect of peripheral neuropathy plasmas, with or without complement, on VGSC function in NSC19 cells.