Abstract:
Precise and spatially controlled modulation of peripheral arterial tone is important for treating microvascular disorders. Current pharmacological vasodilators are typically systemic and lack local specificity. Light-induced photorelaxation has been proposed as an alternative method for vascular modulation. However, its structural and hemodynamic effects in vivo have not been fully characterized. In this study, real-time functional optical coherence tomography (OCT) was used to visualize and quantify blue-light-induced peripheral arterial photorelaxation in living mice. Arteries in the femoral, tail, and auricular regions were exposed to 473-nm blue-light stimulation and imaged using OCT angiography and Doppler OCT to monitor changes in vessel diameter and blood flow. Blue-light stimulation induced rapid, reversible, and artery-selective vasodilation with minimal effects on adjacent veins. Flow velocity decreased during stimulation whereas the increase in vessel cross-sectional area resulted in higher volumetric blood flow. The vasodilatory response was retained in single opsin-deficient mouse models (Opn3⁻/⁻, Opn4⁻/⁻, and Opn5⁻/⁻) but was absent in Opn4/Opn5 double-knockout mice, indicating a cooperative role of non-visual opsins. These findings demonstrate increased local perfusion during optical stimulation and highlight the potential of photorelaxation as a spatially targeted approach to vascular modulation.