SERIAL CHANGES OF EVOKED POTENTIALS IN KAINIC ACID (KA)-INDUCED LIMBIC SEIZURES IN CHRONIC CATS Shigeya Tanaka 1 , Tatsuya Tanaka 1 , Yukichi Yonemasu 1 1Department of Neurosurgery, Asahikawa Medical College pp.565-570
Published Date 1987/6/1
DOI https://doi.org/10.11477/mf.1406205924
  • Abstract
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On the basis of careful histological works in-cluding the use of experimental techniques, nearly all of the workers came to the conclusion that no neuronal connections between amygdala and hip-pocampus exist, regardless of close topographycal localization or intimate functional cooperation. We examined ipsilateral amygdalo-hippocampal responses (A-H), hippocampo-amygdaloid re-sponses (H-A) and amygdalo-cortical responses (A-Cx) in normal or epileptic cats by means of evoked potential method.

Stereotaxic operations were carried out in ten adult cats. Bipolar electrodes were placed in the left amygdala and ipsilateral dorsal hippocampus, and stainless screws on the dura over the bilateral anterior sigmoid gyrus. A teflon needle with an inner needle guide was also inserted obliquely into the ipsilateral amygdala. The bipolar elec-trodes allowed both to stimulate and to record the electrical activity. Two hundred rectangular pulses (0.3 msec, 5 V, 2 Hz) were given and evoked re-sponses summed and averaged by a computer.

These evoked studies were made before and after KA injection (1 microgram) into the ipsila-teral amygdala. In controls, only A-H were ob-served. During limbic status stage, H-A began to appear and peak latencies of A-H shortened in accordance with seizure development. During generalized seizure stage, A-Cx was newly ob-served and peak latencies of both A-H and H-A shortened. Peak latencies of the evoked potentials began to shorten soon after development of limbic seizure, and stepwise shortening of peak latencies were recognized in some cases. These results suggested that the transmission at synapses were modified by these exitatory effect of epileptic phenomena.

Spike-related evoked potential method was also applied during limbic status stage and generalized seizure stage triggering by the high amplitude interictal discharges. The latencies of A-Cx by this method were considerably shorter than that of evoked potential method. This discrepancy of peak latencies between ordinarily evoked responses and spike-related evoked responses suggests some different mechanism in propagation of electrical activity during seizure.

Copyright © 1987, Igaku-Shoin Ltd. All rights reserved.


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