A: Laser doppler measurement of blood flow in hind limb of C57BI/6 mice. 670 nm light was applied at increasing intensities (25, 50, 100 mW/cm2) for 15 min. The flow was measured as a difference between the irradiated limb and the other (control) limb of each animal. Upper: Representative image. Lower: Quantification. Values are mean±SE, *p<0.005, **p<0.001 vs. Control B: Red light induces exertion of stable vasodilatory agent from pre-constricted murine facialis arteries. Red light (670 nm, 6 J/cm2) induced dilation of primary blood vessel as measured by pressure myography. The bath buffer was collected, and after 30 min transferred to dilate a second naïve vessel..