Effect of nitric oxide synthase inhibitor on optic nerve head circulation in conscious rabbits.
OBJECTIVE
To study the effect of a nitric oxide synthase inhibitor on tissue circulation in the optic nerve head (ONH) of conscious rabbits.


METHODS
N(G)-nitro-L-arginine methyl ester (L-NAME) (1, 10, or 100 mg/kg), D-NAME (10 mg/kg), or physiological saline was administered intravenously to albino rabbits. A quantitative index of blood velocity, the normalized blur (NB), was measured in the ONH by laser speckle tissue circulation analyzer. The intraocular pressure (IOP) and blood pressure (BP) were also measured. L-arginine (10 mg/kg) was intravenously administered 20 minutes after L-NAME (10 mg/kg) injection. Acetylcholine (ACh; 10 microg/kg per minute) was infused for 15 minutes, with or without pretreatment of L-NAME (1 mg/kg).


RESULTS
L-NAME induced a continuous decrease of the NB in a dose-dependent manner, but D-NAME caused no significant change. At 100 mg/kg, L-NAME significantly increased the IOP, mean BP, and ocular perfusion pressure, but the other doses caused no significant changes. When L-arginine was administered after L-NAME injection, the NB returned to its initial level and remained there. Pretreatment with L-NAME inhibited the increase of NB induced by ACh.


CONCLUSIONS
These results indicate that nitric oxide regulates basal tissue circulation in the ONH of conscious rabbits and suggest that ACh increases the circulation by promoting nitric oxide synthesis.
Sugiyama
T
T
Department of Ophthalmology, Osaka Medical College, Takatsuki, Japan. opt017@poh.osaka-med.ac.jp
Oku
H
H
Ikari
S
S
Ikeda
T
T
D000109:Acetylcholine / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000008:administration & dosage / Q000494:pharmacology; D001775:Blood Circulation / Q000187:drug effects*; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D007275:Injections, Intravenous; D007429:Intraocular Pressure / Q000187:drug effects; D017078:Laser-Doppler Flowmetry; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D052250:Nitric Oxide Synthase Type III; D009898:Optic Disk / Q000098:blood supply*; D011817:Rabbits; D012039:Regional Blood Flow / Q000502:physiology
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester