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Hanan Awad Alkozi, Victoria Eugenia lledó, Jesus J Pintor; Yellow filter effect on melatonin secretion in the eye: Role in IOP regulation. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1664.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate if melatonin levels in the aqueous humour of New Zealand rabbits is modulated by yellow filters and if therefore there is a modification of intraocular pressure.
New Zealand white rabbits were used in this study (n=12). They were divided in two groups, one under controlled 12 h light/dark cycles, while a different group had their cages encased with a yellow filter (465-480 nm). IOP measurements were taken by a TonoVet every week at the same time before they were anesthetized for aqueous humour extraction with a 30-gauge needle in the irido-corneal limbus. After the third week, the melatonin antagonists luzindol and 4PPDOT were administered at a concentration of 100 µM (20 µL), and IOP was measured at 10 to 120 minutes. To verify the participation of melanopsin in the observed effect, the group under white light received a single dose of the melanopsin antagonist AA92593 and IOP measurements were done at 20 min, 40 min, 1, 2, 3, 4, 5, 6 hours after applying the antagonist. Finally melatonin levels in the aqueous humor were analyzed by the HPLC.
Keeping the rabbits under the effect of yellow filter resulted in a decrease in IOP after 3 weeks. IOP decreased to 43.8±7.8% (***p<0.0001, n=6) compared to the control animals. This effect was completely reversed 30 minutes after the topical application of the selective and non-selective melatonin receptors agonists, 4PPDOT and luzindol. Also, blocking melanopsin by its antagonist AA92593 under white light condition decreased IOP up to 32.7±15% (***p<0.0001, n=6) 2 hours after the application of a single dose of melanopsin antagonist compared to the control rabbits. Finally, melatonin levels were found significantly higher in the aqueous humor of rabbits developed under yellow filter compared to rabbits receiving normal white light. Control animals (white light) presented aqueous humor melatonin concentrations of 15.3±3.1 ng/ml, while the animals under the yellow filter presented 37.4±4.2 ng/ml, both measured the third week (***p<0.0001, n=6).
Yellow filters modulate melatonin levels in the aqueous humour of white new Zealand rabbits due to deactivating melanopsin activity. This effect leaded to a decrease in IOP which is mediated by melatonin receptors. The use of yellow filters could be useful to lower IOP and prevent ocular hypertension.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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