ラット局所脳虚血における脳内カテコールアミンの変動—HPLC-ECD法による測定

CHANGES IN REGIONAL CEREBRAL CATECHOLAMINES FOLLOWING MIDDLE CEREBRAL ARTERY OCCLUSION IN THE RAT

　抄録　局所脳虚血後の脳内カテコールアミン（CA）の経時的変化，および虚血病巣から遠隔の脳内領域での影響について検討した。ラットの中大脳動脈を閉塞後，1／2,1,2,3,6,12,24時間に断頭し，両側の線条体・大脳皮質・小脳半球の計6箇所の切片を作製した。CAは高速クロマトグラフィーで測定した。Dopa—mine （DA）は虚血側の線条体・大脳皮質では1時間後から減少し，6時間にはそれぞれコントロール値の40％，30％に達し以後ほぼ同じ値であった。Norepinephrine （NE）は虚血側大脳皮質で，1時間に50％に低下し以後ほぼ同じ値を示した。以上DA・NEとも虚血病巣内では減少することが確認されたが，NEの減少はDAより急激でありNEの代謝障害は早期に起きるものと推測された。また虚血30分に両側大脳皮質のNE値が，一過性に増加し，対側皮質の増加はDAの減少を伴っていた。この対側皮質の変化は遠隔効果を示唆する所見であり，この機序につき若干の考察を加えた。

Ischemic brain injury affects the content and metabolism of brain monomines. Our aim was to know the time course of changes in regional cere-bral catecholamines during focal cerebral ischemia, and whether focal cerebral ischemia may affect the metabolism of catecholamines in distant area of the brain.

Methods Fifty-five rats were subjected to oc-clusion of the middle cerebral artery (MCA) on the olfactory tract, under halothane anesthesia. Fourteen animals were sham-operated group. Ani-mals were decapitated at 1/2, 1, 2, 3, 6,12 and 24 hours post-occlusion (PO), respectively. The brains were removed, and the brain structures dissected out include bilateral corpus striatum, cerebral cortex (MCA territory) and cerebellar hemisphere. Catecholamines were extracted by alumina procedure, and determined by high-per-formance liquid chromatography with electroche-mical detection.

Results Dopamine (DA) contents, in ipsilateral corpus striatum and cerebral cortex to the ische-mia, decreased at 1 hour PO, and reached, at 6 hours PO, to 40% of control value in corpus striatum and 30% in cerebral cortex, respectively. After 6 hours PO, DA remained low. Norepine-phrine (NE) content in the ipsilaterl corpus stria-tum gradually reduced and reached to 60% of control value at 24 hours PO. NE in the ipsila-teral cerebral cortex decreased to 50% of control at 1 hour PO, and thereafter remained reduced. In the contralateral corpus striatum and cerebral cortex, either DA or NE showed no significant changes, except 1/2 hour PO. NE contents in bilateral cerebral cortex showed a transient in-crease at 1/2 hour PO. Cerebellar NE content, bilaterally, reduced slowly to 70% of control at 24 hours PO.

Conclusion Our results clearly demonstrated that catecholamine contents reduced gradually after cerebral ischemia. NE content reduced more ra-pidly than DA content, and NE mediated neurons seem to more susceptible to ischemia than that of DA. The rise in NE content, observed in contra-lateral cerebral cortex at 1/2 hour PO, is consid-ered to be "transneural remote effect". The mecha-nism of transneural remote effect was discussed.