CSF and plasma GABA levels in Parkinson's disease.

CSF gamma-aminobutyric acid (GABA) levels were reduced in patients with idiopathic Parkinson's disease when compared with age matched controls, but the difference was not significant. However, when the Parkinsonian patients were subdivided, CSF GABA levels were lower in the levodopa treated group than in the untreated group and the controls. There was no difference in plasma GABA levels between Parkinsonian patients and controls.