Uptake of GABA and activity of GABA-transaminase in platelets from epileptic patients

The aim of the present study was to assess the activity of GABA-transaminase (GABA-T) and the kinetic parameters of GABA uptake in platelets from patients with distinct epileptic syndromes. We studied 14 patients with juvenile myoclonic epilepsy (JME), 19 patients with refractory localization-related epilepsy (RLE) and 20 healthy volunteers who were matched for age and sex. Acute effects of valproate (VPA) and lamotrigine (LTG) on the uptake of GABA and the activity of GABA-T in platelets in vitro were also analyzed. The mean activity of GABA-T in JME patients was significantly higher than in control subjects, whereas RLE patients did not significantly differ from controls. The capacity of GABA uptake was least in JME patients, intermediate in RLE patients and highest in controls. In vitro VPA (concentrations 150-1200 microM) or LTG (concentrations 1-100 microM) had no significant effects on GABA uptake. Our results indicate marked differences in the platelet uptake of GABA and the activity of catabolic enzyme GABA-T between patients with generalized and localization-related epileptic syndromes. The observed peripheral alterations may indicate an impairment in the function of brain GABAergic systems.