Propagation of hippocampal seizure activity arising from the hippocampus: a local cerebral blood flow study.

We studied the propagation of spike discharges and the changes in local cerebral blood flow (LCBF) by means of the electroencephalogram (EEG) and autoradiographs to elucidate the underlying mechanism and the propagation pathway in rats with limbic seizures. Seizures were induced by the unilateral microinjection of kainic acid (KA) into the dorsal hippocampus during which behavioral, EEG and LCBF changes were documented. Overall, the results indicate an initial spreading to the contralateral hippocampus from the ipsilateral hippocampus, followed by activation of the ipsilateral amygdala, other limbic structures, striatum and sensorimotor cortex. Finally, seizure activity spreads to the ipsilateral globus pallidus, substantia nigra, subthalamic nucleus, thalamus, septum and parietal cortex. The activation of the contralateral hippocampus in the KA model studied here occurs earlier than in the acute amygdaloid seizure model. Elucidation of the mechanisms underlying this difference in the propagation pathway will require the application in parallel of techniques examining these and other aspects of seizure activity.