Biophoton imaging identification of delayed functional neural circuit injury after cerebral ischemia-reperfusion

The evaluation of structural changes after stroke has made great progress; however, it remains difficult to evaluate functional neural changes.

Here, we report a novel imaging technique that could monitor delayed functional neural circuit injury in an animal model of cerebral ischemia-reperfusion. The changes in 50 mM glutamate-induced biophotonic activities in functional neural circuits in rat brain slices after middle cerebral artery occlusion were investigated with an ultraweak biophoton imaging system.

Six hours after ischemia-reperfusion, the rats presented a significant decrease in motion ability together with a large part of the unstained 2,3,5-Triphenyltetrazolium chloride (TTC) area in the ischemia-reperfusion side, whereas the intensity of the biophoton emissions was consistent on both the ischemia-reperfusion and non-ischemic sides of brain slices. Twenty-four hours after reperfusion, the behavior evaluation and TTC staining recovered slightly, and the intensity of the biophoton emissions was weaker on the ischemia-reperfusion side than on the contralateral side. One week after reperfusion, the behavioral test and TTC staining recovered to normal levels; however, the intensity of the biophoton emissions was decreased significantly on both the ischemia-reperfusion and contralateral sides, and such changes were even distinguished in different brain areas, such as the sensory and motor coteries and striatum.

These findings suggest that delayed functional neural circuit injury induced by cerebral ischemia-reperfusion could be identified with biophoton imaging techniques, providing a novel functional evaluation method for animal models of cerebral ischemia-reperfusion.