The effects of electroconvulsive therapy on GABAergic function in major depressive patients

It has been proposed that major depression is associated with a dysfunction of the gamma-aminobutyric acid (GABA) system. This study was planned to investigate whether there are any alterations in GABAergic activities in major depressive patients and, if there are, whether electroconvulsive therapy (ECT) has any effect on these changes.

Twenty-five depressed inpatients who responded to a course of ECT and 23 healthy subjects were included in the study. Serum GABA levels were measured 2 days before and 10 minutes after the first ECT and 3 days after the last ECT, and a baclofen challenge test was performed 2 days before the first ECT and 3 days after the last ECT in the patients. The same tests were carried out only once in the control group.

Depressive patients had lower serum GABA levels compared with healthy individuals, and ECT caused a significant increase in these levels. The acute effect of the one-ECT procedure was a huge increase in the baseline GABA levels. Although there was no difference in the maximum alteration in growth hormone with baclofen between the patients and controls before the therapeutic ECT course, it became significantly higher in the depressive patients than in the controls after the treatment.

The findings of this study support the GABA deficit hypothesis of major depression because major depressive patients have lower levels of serum GABA that are increased by a completed ECT course. ECT seems to increase brain GABA levels as well as GABAB activity, and these effects may contribute to its mechanism of therapeutic effect.