Effect of freezing on gamma-aminobutyric acid levels in human cerebrospinal fluid.

Using a radioreceptor assay, the concentration of gamma-aminobutyric acid (GABA) in human cerebrospinal fluid (CSF) was found to be elevated significantly following a single deep-freeze to --70 degrees C and thaw. Mean CSF GABA (+/- SD) in unfrozen CSF was 173 +/0 73 pmol/ml (n = 24). After a single deep-freeze, the mean level was 243 +/- 106 pmol/ml (p less than 0.02). Subsequent freeze-thaw cycles resulted in further irregular and unpredictable elevations in CSF GABA. Mean level after two freezes was 379 +/- 125 pmol/ml and after three freezes 654 +/- 411 pmol/ml. These changes could result in the incorrect interpretation of results in patients suffering from neurological diseases.