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Editors Selection IGR 16-4
Examination methods: IOP
Comment by Jonathan Crowston on:
15201 Effect of light cycle on 24-hour pattern of mouse intraocular pressure, Sugimoto E; Aihara M; Ota T et al., Journal of Glaucoma, 2006; 15: 505-511
The molecular processes that regulate 24-hour (circadian) IOP variation are not well understood, Sugimoto et al. (1051) in this elegant study demonstrate robust variation in circadian IOP in the ddY albino mouse eye, which was similar to that reported previously in Swiss white mice. These data are of interest because of our ability to manipulate the mouse genome and thus use transgenic and knockout mice to investigate the roleof individual genes in circadian IOP control.
Intraocular pressure in the ddY mice was lower during the daytime light-phase compared to the nocturnal dark-phase. The authors also demonstrated that housing mice in constant light or constant dark for four weeks prior to IOP measurement, completely abrogated the circadian IOP variation present in mice exposed to alternating 12-hour light-dark cycles. Interestingly, mice maintained in constant dark had a significantly higher mean IOP compared to mice maintained in constant light.
Light exposure therefore appears to play an important role in circadian IOP variation. However, it is not yet clear whether the effect of lighting on IOP was a direct effect or secondary to other behavioral changes such as feeding, physical activity and stress that may also be influenced by lighting and are known to affect IOP. Once this is established, investigation of 24-hour IOP in genetically modified mice may shed new insights into the endogenous processes that control IOP variation.
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