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H. Liu, C.A. Opere, M. Zhao, C.J. Destache, G.L. Zhan, S.E. Ohia; Effect of 8–isoPGE2 on Catecholamine Levels in Rabbit Retina and Vitreous Humor, in vivo . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2616.
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Isoprostanes have been reported to regulate the release of excitatory amino acids from isolated bovine retinae (Opere et al., Neurochem. Res. 30: 2005). However, the effect of isoprostanes on endogenous catecholamine levels remains unknown.
To determine the effect of intravitreally injected 8–isoprostaglandin (PG)E2 on endogenous retinal and vitreous humor catecholamine levels in rabbits, in vivo.
Albino rabbits (New Zealand strain; 2 kg) were sedated with intramuscular ketamine and xylazine, then injected intravitreally with 8–isoPGE2. Control eyes received an equal volume of vehicle. After 4 hours, animals were sacrificed painlessly with CO2 gas. Vitreous humor and retina were isolated for measurement of catecholamine levels and metabolites by HPLC–ECD system.
Intravitreally injected 8–isoPGE2 (0.1 and 10µM) increased dopamine levels in the retina by 56 % (p<0.01) and 107 % (p<0.001) respectively. In contrast, 8–isoPGE2 had no significant effect on retinal norepinephrine levels in concentrations up to 10 µM. The dopamine metabolite, 3,4–dihydroxyphenylacetic acid (DOPAC) was increased by 25 % at 0.1 µM 8–isoPGE2. Although serotonin was not detected, the concentration of its metabolite, 5–hydroxyindole acetic acid (HIAA) was decreased by 42 % at 0.1 µM 8–isoPGE2. In the vitreous humor, dopamine concentration was increased by 23% at 0.1 µM 8–isoPGE2 but decreased by 10% at the higher concentration of this isoprostane. 8–isoPGE2 (0.1 and 10 µM) decreased norepinephrine levels in the vitreous humor by 43% and 66%, respectively. 8–isoPGE2 (0.1 and 10 µM) decreased DOPAC levels while HIAA concentrations were increased by this isoprostane in the vitreous humor.
We conclude that 8–isoPGE2 can alter catecholamine levels in rabbit retina and vitreous humor, in vivo. The mechanism that underlies the observed changes in neurotransmitter concentrations induced by this isoprostane merits further investigation.
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