The human endogenous local anesthetic-like factor (ELLF) is functionally neutralized by serum albumin

The cerebrospinal fluid (CSF) of patients with multiple sclerosis or Guillain-Barré syndrome contains a factor that inhibits excitation of nerve and muscle cells like local anesthetics. CSF samples containing the endogenous local anesthetic-like factor (ELLF) were analyzed by gel filtration chromatography and ultraviolet (UV) absorption at 210 nm. The active component was in a single peak corresponding to a molecular weight of 600–800 Da. This peak was decreased and the Na + channel blocking activity was neutralized by the addition of 40 g/l human serum albumin to the CSF. When the albumin was separated from the CSF/albumin mixture by acetonitrile treatment, the Na + channel blocking activity reappeared. The ELLF and its neutralization may be of relevance for the clinical fluctuations known with these diseases.