Repeated electroconvulsive stimulation impairs synaptic plasticity in the 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 vivo, as measured by input/output curves, and reduced the degree of long-term potentiation (LTP) obtained following high frequency stimulation. An identical course of ECS had no effect on synaptic responses recorded in the stratum radiatum of CA1 in vitro and did not impair high frequency-induced LTP. These results suggest that either ECS has a selective effect on the sub-fields of the hippocampus or that in vitro recording techniques are unsuitable for detecting the increase in synaptic efficacy produced by the treatments.