Effects of dopaminergic drugs on cerebrospinal fluid GABA concentration in Parkinson's disease

Abstract

Increased striatonigral GABAergic activity reduces striatal dopamine turnover. We measured cerebrospinal fluid (CSF) GABA concentrations in untreated and treated parkinsonian patients and control subjects. The 4 ml sample of cerebrospinal fluid for GABA assay (radioreceptor method of Enna et al.) was collected after 20 ml of CSF had been removed. It was immediately frozen and assayed within six weeks. The mean concentration ( ± SEM) of CSF GABA in untreated parkinsonian patients and control subjects was 181 ( ±34) and 203 ( ± 5) pmoles/ml, respectively. In treated parkinsonian patients taking either levodopa/carbidopa (mean daily dose ± SEM, 1150 115 ± 240 24 mg ) or lergotrile (mean daily dose 50 mg), the mean CSF GABA concentrations ( ± SEM) were 184 ( ± 31) and 215 ( ± 22) pmoles/ml, respectively. Our results suggest that the concentration of released GABA is normal in Parkinson's disease and dopaminergic drugs do not modify the activity of GABAergic neurones.