猫一側尾状核内カイニン酸微量注入により誘発される二次性全般化発作

Kainic Acid-induced Generalized Seizures in Cats : Microinjection into Caudate Nucleus

　無麻酔，無拘束下にて猫一側尾状核にkainic acid（KA）を2μg注入すると，2ないし5分後に猫は注入反対側への回旋運動を行い，脳波上では注入部から初発するfocal seizureが誘発される。15〜25分後には脳波上はsecondarily generalized seizureが繰り返し出現するようになったが，行動上は無動発作であった。1ないし3時間後にはsniffing, searching, mastication, salivationも見られるようになった。6ないし8時間後には脳波上では全誘導同時に始まる発作が起こり，対側下肢の間代性痙攣が見られ，引き続き，対側下肢から始まり，対側上肢，同側上下肢に広がる二次性強直性・間代性全身痙攣発作に発展した。

　カイニン酸誘発による尾状核焦点発作重積ではfocal seizure stageが短く，極めて短時間に二次性全般化発作が出現し，尾状核は，てんかんの全般化に密接に関与していることを明らかにした。

Electroencephalograhic and behavioral changes were observed after 2pg of kainic acid (KA) injec-tion through a chronically implanted cannula into unilateral caudate nucleus (CN) of freely moving and non-anesthetized cats. The control group showed no changes on EEG or behavior during the observation period.

In KA group, from 2 to 5 minutes after KA injec-tion, the cats showed contralateral circling. On EEG, focal spikes were elicited at the injected site of the right CN. From 15 to 25 minutes after the injec-tion, secondarily generalized seizures were observed on EEG repeatedly. However, the behavioral change was not remarkable and only the behavioral arrest was observed during the electrographic generalizedseizure. From 6 to 8 hours after injection, they showed clonic seizure of the cotralateral hindlimb followed by generalized tonic-clonic convulsion. These seizures were frequent during 6 to 16 hours after injection. However, these seizures subsided within 48 hours after the injection and the cats became normal afterward. Histopathological exami-nation revealed focal pyknosis and gliosis only at the jnjection site of caudate nucleus.

The results suggested that an epileptogenic focus of the caudate nucleus demonstrated a rapid evolu-tion from the focal seizure status to the secondarily generalized seizure status. This fact explains that the caudate nucleus may be a possible key structure as a relay nucleus for the secondary generalization of a focal seizure.