Epileptic-like activity induces multiple forms of plasticity in hippocampal area CA1

Mesial temporal lobe epilepsy is a relatively common form of epilepsy that afflicts many thousands of people. It has been suggested that the developme nt of primary and secondary foci may involve mechanisms similar to long-ter m potentiation (LTP). In vitro seizure models typically involve an increase in spontaneous asynchronous bursting activity (epileptiform activity) indu ced either by increasing excitation or decreasing inhibition. Previous expe riments have indicated that these models often generate bursting activity t hat closely resembles epileptic activity. LTP is often observed following e pileptiform activity. In area CA1 of the hippocampus two forms of LTP that are dependent on the activation of either the L-type voltage dependent calc ium channel (vdccLTP) or the N-methyl-D-aspartate receptor/channel (nmdaLTP ) have been described. It is unclear from previous experiments which type o f LTP results from epileptiform activity. Recent evidence indicates that nm daLTP is most likely a short-term type of plasticity while vdccLTP may be a long-lasting form of synaptic plasticity. Given the characteristics of vdc cLTP it is a likely candidate mechanism to underlie the development and for mation of secondary seizure foci. We have therefore tested the ability of e pileptiform. activity induced by elevated potassium chloride to induce mult iple forms of LTP in area CA1 of the rat hippocampus. Elevation of extracel lular potassium chloride resulted in spontaneous asynchronous bursting. The net result of the spontaneous asynchronous bursting was to induce a compou ndLTP consisting of nmdaLTP and vdccLTP components. (C) 2001 Published by E lsevier Science BY.