Two types of EEG spikes in the kindled rabbit hippocampus

The characteristics of interictal EEG spikes were studied in the rabbit hippocampus. After kindling for 2-4 weeks, rabbits were anesthetized and curarized for acute experiments. There were two types of EEG spikes in the kindled hippocampus; one (B) had its source in the stimulated side, and the other (A) in the contralateral side. In addition, compound EEG spikes (C) were observed that consisted basically of B and A spikes. Intracellular counterparts of A and B spikes were generally a depolarization-hyperpolarization sequence in the CA1 pyramidal cells. On the other hand, counterparts of the C spikes were initial depolarization with a superposed spike burst followed by relatively shorter lasting hyperpolarization which seemed to indicate an enhancement of excitation during the kindling process.