REPEATED ELECTROCONVULSIVE STIMULATION IMPAIRS SYNAPTIC PLASTICITY INTHE DENTATE GYRUS IN-VIVO BUT HAS NO EFFECT IN CA1 IN-VITRO

Repeated electroconvulsive stimulation (ECS) spaced at 48 h intervals significantly increased the synaptic response in the dentate gyms in v ivo, as measured by input/output curves, and reduced the degree of lon g-term potentiation (LTP) obtained following high frequency stimulatio n. An identical course of ECS had no effect on synaptic responses reco rded in the stratum radiatum of CA1 in vitro and did not impair high f requency-induced LTP. These results suggest that either ECS has a sele ctive effect on the sub-fields of the hippocampus or that in vitro rec ording techniques are unsuitable for detecting the increase in synapti c efficacy produced by the treatments.