Blockade and Disruption of Neocortical Long-term Potentiation Following Electroconvulsive Shock in the Adult, Freely Moving Rat

Although the neocortex has been considered to be highly resistant to the induction of long-term potentiation (LTP), we have recently shown that spaced and repeated stimulation of white matter afferents reliably induces neocortical LTP in the freely moving rat. The following study examined the effects of maximal electroconvulsive shock (MES) stimulation on the induction of LTP in the chronically prepared rat. MES stimulation was applied at different intervals following LTP-inducing trains over a 10 day period. High-frequency LTP-inducing stimulation resulted in amplitude changes in both early (9.28 ms to peak) and late (20.81 ms to peak) components of the evoked EPSP, as well as of the population spikes. There was a window of time following high-frequency stimulation within which MES could interrupt the induction of LTP MES stimulation applied immediately, or 1 h after, LTP-inducing trains prevented the induction of LTP LTP was not blocked, however, when the MES stimulation was applied 6 h after the LTP-inducing trains. MES stimulation applied to a fully potentiated animal transiently attenuated both the population spike and polysynaptic measures, but both components recovered within 24 h. These data support the idea of a consolidation gradient for neocortical LTP similar to that seen in behavioural studies.