一時的血流遮断による脳虚血に対する脳保護に関する研究

Abstract

The purpose of this study was to investigate cerebral protection against transient cerebral ischemia, which was induced in cats by 1-hour occlusion of the middle cerebral artery (MCA) via transorbital approach. Regional cerebral blood flow (rCBF) was measured by means of a laser flowmeter and autoradiography, and through a cranial window pial arteries were continuously observed by means of a videocamera system equipped with a width analyzer computer during ischemia and after reperfusion of MCA. Neuronal damage was evaluated 5 hours after reperfusion by a microcomputer imaging device. As protective agents, calcium-antagonist (TA-3090) for use in increasing collateral circulation and nizofenone for improving the ischemic threshold were administered prior to 5 minutes of ischemia. Pial arteries were dilated up to 49.5% at 5 hours after reperfusion in the controls, to 38.5% in the nizofenone treated group (p＜0.05), and to 19.1% in the TA-3090 group (p＜0.01). With regard to rCBF, postischemic hyperperfusion was found markedly in the controls but the degree of hyperperfusion in the TA-3090 group was decreased compared to the controls (p＜0.01). However, there was no significant difference between the nizofenone group and the cotrols. Observation of neuronal damage revealed the infarcted area on the affected himisphere to be 41.9% in the controls, 29.7% in the nizofenone group, 18.4% in the TA-3090 group and 14.2% in the nizofenone and TA-3090 combined treatment group. These results suggest that increased collateral circulation during ischemia protected the brain from transient ischemia by means of inhibiting postischemic hyperperfusion, and maintained the pial artery after reperfusion. The most effective method of brain protection was to increase collateral circulation while simultaneously improving the threshold of ischemia.