Factors in the cerebrospinal fluid of multiple sclerosis patients interfering with voltage-dependent sodium channels

The effect of cerebrospinal fluid (CSF) from patients with multiple sclerosis (MS) on voltage-dependent Na+ channels in human myoballs was studied. The transient Na+ currents, elicited by whole-cell depolarization from -85 to -20 mV, were decreased to 75-25% the control value in the presence of CSF from all 7 MS patients investigated. The effect was complete in about 5 s and was fully reversible on admission of standard external fluid. Such decrease was not or only to a minor extent observed with 10 out of 11 control CSFs from patients without inflammatory neurological disease. The origin of the factors interfering with the Na+ channels is unknown. It is suggested that, in addition to demyelination, impaired Na+ channel function might cause the symptoms in MS.