Kainic acid induces distinct types of epileptiform discharge with differential involvement of hippocampus and neocortex

A. Medvedev, L. MacKenzie, J. J. Hiscock, J. O. Willoughby

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    Systemic administration of kainic acid (KA), an excitatory amino acid agonist, provides a model of epilepsy due to increased neural excitation. We examined discharges using multi-channel EEG recording and spectral analysis in rats implanted with neocortical and hippocampal electrodes after intravenous infusion of KA (10 mg/kg), until and including the first convulsive seizure. Gamma activity (30-80 Hz) increased in hippocampus from 3-9 min after KA administration. Two types of preconvulsive bilateral rhythmic discharges were observed, both consisting of generalised high voltage sharp waves at low frequencies (<10 Hz) mixed with fast oscillations (<20 Hz): (1) generalised non-convulsive discharges (GNCD) occurred in all animals and (2) spike-wave discharges (SW), predominantly localised in neocortex, occurred in 45% of animals. Convulsive seizure evolved out of a GNCD. Spectral profiles of epileptiform discharges were characterised by an increase in power of low (<10 Hz) and high (beta and gamma range, 20-80 Hz) frequencies which were differently expressed in neocortex and hippocampus. Thus, in this model of convulsive epilepsy caused by increased excitation, there is an early increase in gamma activity, a process that might contribute to synchronisation, and two distinct types of bilateral discharges, hippocampal-neocortical (GNCD) and preferentially neocortical (SW). Neocortical, not hippocampal, changes in EEG power correlated with development of convulsive behaviours. Copyright (C) 2000 Elsevier Science Inc.

    Original languageEnglish
    Pages (from-to)89-98
    Number of pages10
    JournalBrain Research Bulletin
    Issue number2
    Publication statusPublished - 15 May 2000


    • EEG
    • Gamma oscillations
    • Generalised epilepsy
    • Hippocampus
    • Kainic acid
    • Neocortex


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