Pre-ischemic exercise preserves cerebral blood flow during reperfusion in stroke

The neuroprotective nature of exercise has been well established and the mechanisms of this protection are still a subject of much research. This study aims to determine if cerebral blood flow is constituently higher during the ischemia or reperfusion events in stroke.

Adult male Sprague-Dawley rats were randomly assigned into exercise or non-exercise (control) groups. Exercised rats underwent 30 minutes of running on a treadmill for 3 weeks. A 2 hour unilateral middle cerebral artery occlusion using an intraluminal filament was performed to induce ischemic stroke, followed by a 24 hour reperfusion. A sham control without exercise and middle cerebral artery occlusion was used. Laser Doppler flowmetry (LDF) and (15)O-H(2)O positron emission tomography (PET) were used to determine cerebral blood flow, respectively. (18)F-fluorodeoxy-D-glucose was used to determine cerebral metabolism in some animals. Histological analysis determined infarct volume in the same animal after blood flow examination.

LDF and PET both indicated that middle cerebral artery occlusion significantly (p<0.05) reduced cerebral blood flow during ischemia and reperfusion in association with reduced cerebral metabolism after stroke. However, pre-ischemic exercise significantly (p<0.05) improved cerebral blood flow during reperfusion, although cerebral blood flow remained at a similar level to that of the non-exercise stroke group during the middle cerebral artery occlusion. This improved cerebral blood flow during reperfusion was associated with decreased brain infarct volume.

This study revealed that pre-ischemic exercise in rats improved cerebral blood flow during reperfusion, suggesting that exercise provides neuroprotection by partially ameliorating the 'no reflow' phenomenon in stroke.