The Behavioral Physiology and Antidepressant Mechanisms of Electroconvulsive Shock.

Objective: This study aimed to determine whether the association between antidepressant (AD) and anticonvulsant effects of electroconvulsive therapy constitutes a necessary, causal relationship.

Methods: The rats received corneal kindling to induce an epileptic focus, whereas electroconvulsive shock (ECS) was given antagonistically. The forced swim test (FST; a model of AD efficacy), cumulative kindling scores (indexing epileptogenesis), and clonus duration (measuring anticonvulsant effects) were used to assess the effects of ECS. Intensity and route of administration (corneal vs pinnate) of ECS were varied within or across 2 experiments.

Results: Under various conditions, an increase in mobility in the FST (an index of AD properties) was observed in the absence of any retardation of kindling; under other conditions, an antiepileptogenic effect occurred in the absence of any change in immobility in the FST. In addition, 2 forms of ECS treatment had equal AD properties, whereas only 1 of the 2 treatments reduced clonus time (suggesting an elevated seizure threshold).

Conclusions: In a rat model, putative AD effects of ECS are dissociable from its antiepileptogenic and anticonvulsant effects, suggesting different stimulus thresholds for the various effects of corneal ECS: the antiepileptogenic effect required a lower current dose than the behavioral effect in the FST, whereas the anticonvulsant effect required the highest stimulation level. With transpinnate ECS, the threshold for the behavioral effect in the FST and the antiepileptogenic threshold were reversed.