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Light adaptation characteristics of melanopsin

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  • NSTL
  • Elsevier
Following photopigment bleaching, the rhodopsin and cone-opsins show a characteristic exponential regenera-tion in the dark with a photocycle dependent on the retinal pigment epithelium. Melanopsin pigment regener-ation in animal models requires different pathways to rods and cones. To quantify melanopsin-mediated light adaptation in humans, we first estimated its photopigment regeneration kinetics through the photo-bleach re-covery of the intrinsic melanopsin pupil light response (PLR). An intense broadband light (similar to 120,000 Td) bleached 43% of melanopsin compared to 86% of the cone-opsins. Recovery from a 43% bleach was 3.4X slower for the melanopsin than cone-opsin. Post-bleach melanopsin regeneration followed an exponential growth with a 2.5 min time-constant (tau) that required 11.2 min for complete recovery; the half-bleaching level (Ip) was similar to 4.47 log melanopic Td (16.10 log melanopsin effective photons.cm(-2).s(-1); 8.25 log photoisomerisations.photo-receptor(-1).s(-1)). The effect on the cone-directed PLR of the level of the melanopsin excitation during continuous light adaptation was then determined. We observed that cone-directed pupil constriction amplitudes increased by similar to 10% when adapting lights had a higher melanopic excitation but the same mean photometric luminance. Our findings suggest that melanopsin light adaptation enhances cone signalling along the non-visual retina-brain axis. Parameters tau and Ip will allow estimation of the level of melanopsin bleaching in any light units; the data have implications for quantifying the relative contributions of putative melanopsin pathways to regulate the post-bleach photopigment regeneration and adaptation.

Dark adaptationLight adaptationMelanopsinPhotopigment bleachingPhotopigment regenerationPupil light responseRETINAL GANGLION-CELLSDARK-ADAPTATIONROD PHOTORECEPTORSA-WAVEBRIGHTNESS-DISCRIMINATIONPIGMENT REGENERATIONCONE PHOTORECEPTORSMESOPIC RODPHOTOPIGMENTRHODOPSIN

Pant, Mukund、Zele, Andrew J.、Feigl, Beatrix、Adhikari, Prakash

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Ctr Vis & Eye Res,Queensland Univ Technol QUT

2021

10.1016/j.visres.2021.07.005

Vision Research

Vision Research

SCI
ISSN：0042-6989
年,卷(期)：2021.188
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