EDTA inhibits in vitro increases in the GABA content of human CSF

Aliquots of pooled samples of lumbar CSF from patients with neurological disorders were subjected to storage at room temperature for different periods of time up to 4 days. The determination of gamma-aminobutyric acid (GABA) levels in CSF by a radioreceptor assay showed a progressive increase in GABA content with time, which could be counteracted by addition of EDTA (5 mM). Similar results were obtained with cisternal CSF collected from dogs. The in vitro increases in GABA levels of untreated CSF might relate to the action of a metal-enzyme which is inhibited by metal-trapping substances such as EDTA.