Human CSF GABA Concentrations: Revised Dowd for Controls, but Not Decreased in Huntington's Chorea

Abstract

GABA concentrations were measured in CSF specimens from 2 large groups of control subjects, one without neurological or psychiatric disease, and one with a variety of neurological disorders not known to involve altered GABAergic function in brain. CSF GABA was also measured in patients with Huntington''s chorea and in patients with other choreiform disorders. GABA was measured in CSF by a modification of the ion exchange-fluorometric method that featured use of a relatively large cation exchange column, and a markedly decreased quantity of sulfosalicylic acid for deproteinization of CSF. Mean GABA concentrations in CSF were 87 and 77 nmol/liter for neurologically normal and abnormal control subjects, 82 nmol/liter for the Huntington''s chorea patients, and 105 nmol/liter for patients with other forms of chorea. The mean concentration of homocarnosine was not reduced in CSF of Huntington''s chorea patients compared with controls. Mean CSF GABA concentrations found in control subjects were less than half the lowest control means previously reported. These low values are attributable in part to a reduction in on-column hydrolysis of conjugated forms of GABA in CSF, which can be produced by excessive sulfosalicylic acid, and in part to improved chromatographic resolution of GABA from other unknown o-phthalaldehyde-reactive compounds in CSF. Analysis of free GABA in CSF does not appear useful for diagnosis of suspected Huntington''s chorea, nor as a possible predictive test for persons genetically at risk for Huntington''s chorea.