Platelet and brain GABA-transaminase and monoamine oxidase activities in patients with complex partial seizures

The activities of gamma-aminobutyrate aminotransferase (GABA-T) and monoamine oxidase (MAO-A and -B) were measured in blood platelets from 27 patients and hippocampal tissues from eight (GABA-T) and ten (MAO) patients with complex partial seizures. The activity of platelet GABA-T was found to be higher in the epileptic patients (43.37 +/- 13.53 pmol/min/mg protein, P < 0.005) in comparison with that found in 14 healthy volunteer subjects (29.59 +/- 13.14 pmol/min/mg protein). This difference was most pronounced in patients treated with carbamazepine (CBZ) (P < 0.01) and phenytoin (PHT) (P < 0.01). Contrary to the platelets, the activity of GABA-T in the hippocampi from the epileptic patients (6.937 +/- 2.204 nmol/min/mg protein) did not differ significantly from that found in seven non-epileptic control cases (7.158 +/- 0.951 nmol/min/mg protein). The increase in GABA-T activity in the blood platelets from the epileptic patients could not be explained by a direct effect of the antiepileptic compounds, since there were no changes in the activities on exposure to PHT, CBZ or VPA in vitro, either of blood platelets or of brain tissue. With regard to platelet MAO, no difference in the activity was found between the two groups, whereas the MAO-B activity in the hippocampi was significantly higher in the epileptic patients (3.51 +/- 1.32 nmol/mg/mg protein) than in the control cases (1.21 +/- 0.73 nmol/mg/mg protein) (P < 0.0004). There was no difference in MAO-A activity in the hippocampi between epileptic patients and controls.

In the hippocampi from patients with complex partial seizures the activities of the mitochondrial enzymes GABA-T and MAO-A were similar to those found in control subjects. The activity of MAO-B, however, was significantly higher indicating that there is an increased proportion of reactive astrocytes in epileptic hippocampus.