一過性中大脳動脈閉塞ラットにおけるsomatosensory evoked potential と グルコース代謝

SOMATOSENSORY EVOKED POTENTIAL AND LOCAL CEREBRAL GLUCOSE UTILIZATION IN THE TRANSIENT MCA-OCCLUDED RAT

　抄録　脳虚血急性期にその組織がreversibleかirreversibleかをSEP （somatosensory evoked poten-tial），グルコース代謝から判断出来るかどうかを中大脳動脈（MCA）閉塞再開通ラットを用いて検討した。方法は200-250g雄Wistar ratを用い，左MCAをZenのclipで閉塞し2群に分けた。第1群は閉塞1時間後にclipを除去し再開通を行い，第2群は閉塞2時間後に再開通を行った。第1群および第2群共に閉塞前より再開通30分後までSEPをモニターし，¹⁴C-DG autoradiographyを施行した群と，2-3時間後までSEPをモニターしその後麻酔より覚醒させ3日後に組織学的変化を観察した群とに分けた。結果はMCA閉塞によりSEPは消失し，1時間閉塞群では再開通後P₁，　N₁波は正常に回復したが2時間閉塞群ではP₁-N₁のamplitudeの低下とlatencyの遅延を認めた。再開通後30分で施行した¹⁴C-DGオートラディオグラフィーでは1時間閉塞群ではグルコース代謝は対側の78％にまで回復したが，2時間閉塞群では34％にまでしか回復を認めなかった。また再開通72時間後の組織学的検索では1時間閉塞群では梗塞巣を認めず，2時間閉塞群ではsensorimotor cortexに100％梗塞を認めた。以上よりSEP，局所脳グルコース代謝共に脳虚血の予後判定に有用と考えられた。

Wistar rats were used through the experiments. Preparatory operations for the autoradiography and somatosensory evoked potential (SEP) were performed under 1. 5% halothane anesthesia. After a control measurement of SEP, the left MCA was occluded with a micro clip. The animals were divided into 2 groups. In the 1st group (n=8), the clip was removed 1 hour after MCA occlusion and 4 rats were used for the measurement of local cerebral glucose utilization (LCGU) by 14C-DG autoradiography. Another 4 rats were allowed torecover from anesthesia and used for the histopatho-logical examination after 72 hours. In the 2nd group (n 8), the clip was removed 2 hours after occlusion and the same procedures were performed. SEP was monitored throughout the experiment.

Two positive and one negative peaks were recorded before MCA occlusion. SEP diminished immediately after MCA occlusion. Following the removal of the clip, complete recovery of SEP was observed in the 1st group of rats. However, in the2nd group, recovery of SEP was minimal. In the 1st group, LCGU in the sensorimotor cortex at 30 minutes after reperfusion showed 22% reduction compared to that of the contralateral homologous area. In the 2nd group, in the contrast, 66% reduc-tion of LCGU was observed.

Exipermental results indicate that SEP and LCGU in the early recovery period of ischemia are able to predict the reversivility of ischemic brain.