The effect of nitric oxide synthase inhibitor on form-deprivation myopia.
OBJECTIVE
Form-deprivation myopia (FDM) is believed to result principally from actions of substances that modulate information processing in the retina. We used a chick model to investigate what role nitric oxide (NO), a gaseous neuromodulator, might play in the development of FDM.


METHODS
We injected different concentrations of the NO synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) (30 ml) into the left eyes and the same volume of saline into the right eyes of 6-day-old chicks. Both eyes of most chicks were occluded for 6 days with translucent goggles. After removal of the goggles, the refraction was measured by retinoscopy and the axial lengths with an A-mode ultrasound. In some chicks we measured the concentration of NOx (nitrite and nitrate) in the retina. A few chicks, not wearing occluders after injection of L-NAME and saline, ERG and refraction, were examined 6 days after the treatment.


RESULTS
In chicks that wore occluders, refractive error and axial length were significantly less affected in eyes injected with L-NAME (180, 360, or 540 mM) compared to control (right) eyes. ERG changes were reversible, except in eyes injected with the highest concentration (540 mM) of L-NAME. The eyes of chicks, injected with L-NAME and reared without occlusion, had normal refractive values. After 6 days of form deprivation, the concentration of NOx in the retina of eyes injected with L-NAME (180 mM) was significantly less than the concentration in eyes injected with saline.


CONCLUSIONS
The injection of L-NAME before occlusion of developing chick eyes leads to reversible modifications in retinal function and inhibits the development of form-deprivation myopia.
Fujikado
T
T
Department of Ophthalmology, Osaka University Medical School, Japan.
Kawasaki
Y
Y
Fujii
J
J
Taniguchi
N
N
Okada
M
M
Suzuki
A
A
Ohmi
G
G
Tano
Y
Y
D000818:Animals; D002645:Chickens; D004596:Electroretinography; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005556:Form Perception; D009216:Myopia / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D009573:Nitrites / Q000378:metabolism; D012029:Refraction, Ocular; D012160:Retina / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D012683:Sensory Deprivation
D004791:Enzyme Inhibitors; D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester