一時的脳虚血におけるプリン代謝産物と脳軟膜動脈血管径 : 特に脳梗塞との関連について

Abstract

Twenty adult cats were divided into 4 groups. Ischemia of 30 minutes and 1, 2 and 3 hours duration was respectively induced by unilateral occlusion of the left middle cerebral artery. Extracellular purine catabolites in the gray matter at the ectosylvian gyrus were analyzed with in vivo brain microdialysis technique. Simultaneously, diameter of the pial arteriole was measured through the cranial window using an intravital microscope and a width analyzer. Extracellular concentrations of adenosine, hypoxanthine and xanthine were found to be 0.86±0.16μM, 4.01±2.73μM, and 3.93±2.39μM, respectively. During ischemia, the concentration of adenosine increased 8.7-fold and arterioles dilated in diameter to 170% in comparison with the resting values. These findings in extracellular adenosine concentration and pial arteriolar dilatation during ischemia support a role of adenosine in regulation of cerebral blood flow and protection of the brain tissue. After reperfusion, arteriolar diameter had returned to 120%o of the resting state. But 50 minutes after reperfusion, pial arteriole began to dilate. This late arteriolar dilatation was coincident with the increasing of the xanthine concentration in 1-3 hours ischemia animals. These results suggest that free radicals might be produced and could affect pial arterioles and brain tissue 50 minutes after reperfusion in 1-3 hours ischemia animals. In the 30 minutes ischemia, pial arterioles did not dilate again and the xanthine concentra- tion was unchanged. We speculate that D-to-O conversion might not be promoted in the 30 minutes ischemia animals.