LONG-TERM ENHANCEMENT OF ENTORHINAL-DENTATE EVOKED-POTENTIALS FOLLOWING MODIFIED ECS IN THE RAT

Electroconvulsive therapy (ECT) is widely used as a treatment for drug -resistant depression. The animal analogue of ECT is electroconvulsive shock (ECS) seizures. We have recently shown that repeated ECS seizur es cause a long-lasting, perhaps permanent, enhancement in entorhinal- dentate evoked potentials in the rat. Our study, however, involved 'un modified' ECS, whereas in clinical practice ECT is now usually given i n its 'modified' form (with near-threshold currents, a short-acting ba rbiturate, muscle relaxant and oxygen). We have therefore repeated our experiments using modified ECS. Entorhinal-dentate evoked potentials were measured in Long-Evans rats before and after: (1) eight modified ECS seizures; or (2) eight sham modified ECS trials. Despite the use o f the modified procedure, a significant and long-lasting enhancement i n population spike amplitude was seen in the ECS group. We conclude th at the modified procedure does not protect rats against the long-lasti ng enhancement of evoked potentials. Similar changes may be occurring in the brains of patients subjected to modified ECT. (C) 1997 Elsevier Science B.V.