Facial arteries from C57Bl/6 mice were isolated and pressurized to 60 mmHg before pre-constriction with U46619. A) Energy exposure (R/NIR) produced a time dependent increase in vessel diameter (* p<0.001 vs baseline, n=21). Denudation of the vessel significantly attenuated dilation († p<0.001 vs. R/NIR, n=11). B) Pre-incubation with NOS inhibitor L-NAME (1 mM) did not significantly attenuate R/NIR dilation, however c-PTIO (100 μM) abolished the R/NIR effect (†=p<0.001 vs. R/NIR, n=10). C) Energy exposure (R/NIR) to vessels from eNOS knockout mice produced a similar time dependent increase in vessel diameter when compared to wild type control (*=p<0.001 vs baseline, n=10). D) Pre-incubation with ODQ (10μM) abolished the R/NIR effect (†=p<0.001 vs. R/NIR, n=8). R/NIR dilation curves in panels B–D are duplicated from Panel A.