Ketamine and phenobarbital do not reduce the evoked-potential enhancement induced by electroconvulsive shock seizures in the rat

Electroconvulsive shock (ECS) seizures provide an animal analog of electroc onvulsive therapy (ECT). Repeated ECS seizures cause a long-lasting, and pe rhaps permanent, enhancement of entorhinal-dentate evoked potentials (EPs) in the rat. Recently it has been reported that ketamine protects against EC S-induced EP enhancement. The present study was designed to replicate these findings and to extend them by incorporating a phenobarbital group (to con trol for ketamine's partial diminution of seizures) and an animal test of a ntidepressant activity (the Porsolt test). Unexpectedly, we found that neit her ketamine nor phenobarbital protected against ECS-induced enhancement of EPs. Both, however, diminished the 'therapeutic' effects of ECS, as modele d by the Porsolt test. These data suggest that the use of ketamine would no t eliminate the unwanted effects of ECT and that it might diminish ECT's th erapeutic benefits. (C) 1999 Elsevier Science Ireland Ltd. All rights reser ved.