Deep prepiriform cortex modulates kainate-induced hippocampal injury.

ABSTRACT

As seizure propagation within limbic structures is mediated in part by a small area of deep prepiriform cortex (area tempestas), we investigated the role of area tempestas in modulating hippocampal injury induced by systemic kainate administration. Injury was quantitated by counting the numbers of neurons that stained for the 72,000 mol. wt heat shock protein and with acid-fuchsin dye. Status epilepticus induced these markers of neuronal injury in the CA1 and CA3a regions of the hippocampus, thalamus, piriform cortex and the amygdaloid complex. Microinjection of 2-amino-7-phosphonoheptanoic acid, a competitive antagonist of the N-methyl-D-aspartate subclass of the glutamate receptor, into area tempestas prior to systemic administration of kainate attenuated both heat shock protein induction and acid-fuchsin labeling in CA1 and CA3a pyramidal neurons without reducing the duration of electrographic seizures. Injections of bicuculline, a GABA antagonist, into area tempestas produced hippocampal damage when given with subcytotoxic doses of intravenous kainate. Thus, area tempestas may be a uniquely sensitive anatomical structure involved not just in seizure propagation but also in modulating the extent and pattern of damage induced in hippocampal neurons as a result of prolonged, systemically induced seizures. These effects are due in part to excitatory and inhibitory projections to neurons in area tempestas.