Laser‐irradiation‐induced relaxation of blood vessels in vivo

Abstract

The response of blood vessels to laser irradiation invivo was studied in the dorsal skin flan glass window chamber model of hamsters. The vasodialatory response of venules was critically dependent on the wavelength of irradiating lasser. Relaxation was not produced in arterioles, althought it was tried repeatedly. Vessels were irradiated with the 514.5 nm single line argon laser with irradiances from 1 to 10 W/cm² on a 1.2 mm-diameter spot. Irradiation of venules with 2.2 W/cm² and 4.25 W/cm² produced reversible relaxation. Venules relaxed initially and after the interruption of irradiation returned to their orginal diameter. At higher irradiances (8.5 W/cm²) an irreversible relaxation was observed. At irradiances of 10 W/cm² and above initial relaxation was accompanied with constriction, focal coaguli, and hemostasis. irradiation with the argon-pumed dye laser at 595 nm did not produce any significant relaxation.