Low CSF GABA in Parkinsonian patients who respond poorly to therapy or suffer from the "on-off" phenomenon

The γ-aminobutyric acid concentration in cerebrospinal fluid was measured by radioreceptor assay in 23 parkinsonian patients (“good responders” and “poor responders” to drug therapy, “on-off” state) and 11 age-matched control subjects. Mean concentrations were similar but significantly lower in the poor responders and the “on-off” state than in the good responders and control subjects. Patients who show good response to drug therapy appear to have a normal level of GABAergic activity that is not altered by drug therapy.