Repeated Electroconvulsive Shock Selectively Alters gamma-Aminobutyric Acid Levels in the Rat Brain: Effect of Electrode Placement.

The neurochemical mechanisms of electroconvulsive therapy (ECT) are not fully elucidated. We examined the effects of electroconvulsive shock (ECS) on brain gamma-aminobutyric acid (GABA) systems. Male Wistar-Furth rats were given ECS via auricular (ear-clip) or corneal electrodes once per day (120 V, 0.5 s) for 10 consecutive days. Two groups of sham ECS rats, one for auricular placement and one for corneal placement, served as controls. Current was measured and seizures were scored during each ECS trial. Rats receiving ECS via corneal electrodes were subjected to more electrical current compared to rats treated with auricular electrodes. Although both groups exhibited behavioral seizures of similar duration, electrode placement had a differential influence on the expression of tonic hindlimb extension and clonic hindlimb activity over the 10-day regimen. GABA levels were increased in all brain regions examined in rats treated with auricular electrodes except the hippocampus and nucleus accumbens; rats treated with corneal electrodes exhibited GABA increases in the hippocampus, frontal cortex, hypothalamus, and olfactory bulbs; a significant decrease in nucleus accumbens; and no change in the substantia nigra and striatum. The mode of ECS delivery selectively alters the pattern of regional alterations of brain GABA level induced by ECS. This effect may be a function of current intensity or localization.