An Experimental Study on the Functional Significance of the Hippocampal Seizure

Abstract

Electrophysiological studies on the effect of hippocampal seizure were investigated in rabbits. When the seizure discharge was induced by hippocampal electric stimulation (100Hz,1 m sec,2.0-4.0V), followings were observed.
1) The threshold of both arousal reaction and evoked muscular discharge due to stimulation of the brain stem reticular formation (RF) increased.2) The frequency of spontaneous unit discharges of the brain stem reticular formation (RF-unit) decreased.3) The threshold of evoked muscular discharge due to stimulation of the cerebral cortex or the hippocampus (HPC) increased.4) Late components (N4-N7) of cortical somatosensory evoked potential to tibial nerve stimulation, were suppressed in amplitude.5) Some components (HN1, HN2, HN6) of hippocampal somatosensory evoked potential (SPE-HPC) to tibial nerve stimulation, also decreased in amplitude.6) The amplitude of the nociceptive reflex induced in tibialis anterior decreased.7)The amplitude of both M and H wave induced in gastrocnemius decreased.8) The amplitude of photoevoked eyelid microvibration (MV) was inhibited.9) There was no significant change in latency of 4) 8).10) In EEG topography the amplitudepower of the Delta, Theta, Alpha and Beta-1 waves decreased.11) Among these,1),2),3)-HPC,5),8), and 10) were eliminated after electric lesions in the nucleus ventralis anterior (VA), while the above-mentioned findings (1),3)-8)) were not observed after administration of either Barbiturate or Carbamazepine.
These results suggest that hippocampal seizure discharges suppress the function of RF, motor and reflex systems. Moreover, VA plays an important role on hippocampal impulses to spread out to cause these suppressive effects.