The role of nitric oxide in hyperaemic response to flicker in the retina and optic nerve in cats.
OBJECTIVE
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.


CONCLUSIONS
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.
Kondo
M
M
Department of Physiology and Medical Biophysics, University of Uppsala, Sweden.
Wang
L
L
Bill
A
A
D000818:Animals; D001783:Blood Flow Velocity / Q000528:radiation effects; D002415:Cats; D003623:Dark Adaptation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006940:Hyperemia / Q000209:etiology / Q000503:physiopathology*; D008027:Light; D008863:Microspheres; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D009898:Optic Disk / Q000098:blood supply; D009900:Optic Nerve / Q000098:blood supply / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D010775:Photic Stimulation; D012039:Regional Blood Flow; D012160:Retina / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D012171:Retinal Vessels / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D014664:Vasodilation / Q000187:drug effects / Q000528:radiation effects
D004791:Enzyme Inhibitors; D019335:Nitroarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase