イボテン酸誘発による辺縁系発作と神経変性

IBOTENIC ACID-INDUCED LIMBIC SEIZURES AND NEURONAL DEGENERATION

　抄録　慢性猫の一側扁桃核内に，イボテン酸（IBO）を微量注入し，臨床と脳波所見を2ヵ月にわたって観察し，あわせて病理組織学的検討もおこない，リン酸緩衝液注入の対照群と比較した。IBOを注入して30-60分後に注入部扁桃核から始まる辺縁系発作が誘発された。発作は初回発作が最も強く，臨床的には同側の瞳孔散大と注意反応がおこり，脳波上は注入部扁桃核初発の辺縁系発作で，注入側優位であった。ところがこの発作は数回おこるのみで，3-4時間にて完全に消失し臨床的にはまったく正常となった。経時的脳波記録でも，発作間発射は認められなかった。病理組織学的検査では，注入部扁桃核に，壊死による小空胞を認めた。壊死の周囲には，著明なgliosis, pyknosisが認められた。海馬のremote lesionとしては，neuronal cell lossやpyknosisが認められたが，この変化は，カイニン酸やキスカリン酸の扁桃核内注入によって誘発される海馬変性より軽微であった。対照群はなんら変化を示さなかった。IBOはlesion toolとして優秀な物質であること，破壊実験では無菌的操作が重要であることを強調した。

Electrographic and clinical observations were made as long as 2 months after the injection of ibo-tenic acid (IBO) solution (50 μg in 1 μl of phos-phate buffer solution) through a chronically implanted cannula into unilateralamygdala of freely moving and non-anesthetized cats. The control group (phosphate buffer group) showed no change during the observation period. About 30 to 60 minutes after the injection of IBO, focal amyg-daloid seizures occurred and propagated to the adjacent limbic structures. Clinically, attention and ipsilateral mydriasis were observed. The siezures occurred only 2 to 5 times and ceased within 4 hours. Cats became electroclinically nor-mal afterwards. Histopathological examination revealed a small necrosis at the injected site of the amygdala. Remarkable pyknosis and gliosis were noted around the necrosis. Remote lesions such as neuronal cell loss and pyknosis were observed in the ipsilateral pyramidal cell layer of the hippocampus. But these changes were mild and not so severe as compared to our previous report of kainic acid microinjection in cats.

Authors emphasized that IBO should be an excellent tool for lesion making and also sug-gested that an aseptic manipulation was essential in the lesion study in cats.