Purpose: To elucidate the role of nitric oxide (NO) in the eye and the flicker-induced vascular response.
Methods: The blood flow in the retina and different parts of the optic nerve was compared in cats treated with the NO-synthase blocker, N(G)-nitro-L-arginine methyl ester and in control animals. In both groups, one of the eyes was dark-adapted, the other was subjected to 8 Hz flickering light. The regional blood flow was measured with the microsphere method.
Results: In control animals, flickering light increased blood flow in the retina and optic nerve head by 39% and 256%, respectively. Pretreatment with N(G)-nitro-L-arginine methyl ester prevented this increase in retinal blood flow and markedly reduced the blood flow in the optic nerve heads.
Conclusion: NO release may mediate much of the vasodilating effect of flicker in cats, and play a role in maintaining normal vascular tone in the optic nerve head.