マウスにおけるローズベンガル光血栓性脳卒中モデルの血行動態および電気生理学的進行

The photothrombotic stroke model is gaining popularity due to its relative simplicity, minimal invasiveness, and clinical relevance. Photothrombosis involves the delivery of an intravascular photosensitizer (Rose Bengal) followed by its photoactivation, resulting in vessel occlusion and ischemia. Using a combination of complementary optical and non-optical techniques, we characterized the physiological changes in mice undergoing photothrombosis. We report that Rose Bengal has vasoconstrictive properties, inducing hypoemia both in the brain and periphery even in the absence of its photoactivation. Conversely, we find that light, when used at photothrombosis-appropriate intensities and durations, induces large amounts of tissue heating and hyperemia even in the distal non-illuminated hemisphere. Furthermore, we show that use of the optimal photothrombotic wavelength based on the Rose Bengal absorption spectrum (yellow-561nm) produces a more consistent and pronounced drop in blood flow, and a shorter latency to the initial spreading depolarization (SD), ultimately resulting in a larger stroke. Similarly, when yellow light is used to induce a stroke in ChR2-expressing mice, the electrophysiological and hemodynamic confounds from green light cross activation of ChR2 are eliminated. Finally, we observe across cohorts that male mice have larger strokes than females. Altogether, we extensively describe important caveats and confounds concerning photothrombosis and provide a detailed characterization of its early ischemic events.Significance statement Photothrombosis is a powerful model of ischemic stroke which uses light to photoactivate an intravascular dye (Rose Bengal). However, little is known about the independent effects of both the Rose Bengal and the light used to activate it. We show that both manipulations introduce separate confounds relevant to stroke outcomes, something which should be considered and accounted for when using this technique. In addition, we demonstrate that by using the optimal Rose Bengal excitation wavelength, the blood flow drop is more pronounced and consistent, resulting in larger strokes. Furthermore, we show that precautions can be taken to avoid spectral overlap when integrating photothrombosis in optogenetic experiments. Finally, we explore sex differences in lesion volume.