April 2009
Volume 50, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2009
Melanopsin-dependent Light Avoidance in Neonatal Mice
Author Affiliations & Notes
  • D. R. Copenhagen
    Dept of Ophthal-Sch of Med, Univ California - San Franscisco, San Francisco, California
  • V. Wu
    Dept of Ophthal-Sch of Med, Univ California - San Franscisco, San Francisco, California
  • T. Porco
    Dept of Ophthal-Sch of Med, Univ California - San Franscisco, San Francisco, California
  • R. C. Renteria
    Dept of Ophthal-Sch of Med, Univ California - San Franscisco, San Francisco, California
  • R. Van Gelder
    Dept of Ophthal-Sch of Med, Washington University, St. Louis, Missouri
  • J. Johnson
    Dept of Ophthal-Sch of Med, Univ California - San Franscisco, San Francisco, California
  • Footnotes
    Commercial Relationships  D.R. Copenhagen, None; V. Wu, None; T. Porco, None; R.C. Renteria, None; R. Van Gelder, None; J. Johnson, None.
  • Footnotes
    Support  NIH Grant EY01869, Research to Prevent Blindness, That Man May See
Investigative Ophthalmology & Visual Science April 2009, Vol.50, 3053. doi:
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    • Get Citation

      D. R. Copenhagen, V. Wu, T. Porco, R. C. Renteria, R. Van Gelder, J. Johnson; Melanopsin-dependent Light Avoidance in Neonatal Mice. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3053.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : Functional rod and cone visual signaling begins approximately 11 days after birth in mice. Melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) are present at birth. At this age these neurons are photosensitive and light can induce early gene expression in the suprachiasmatic nucleus, a target area for ipRGCs. While ipRGCs can control pupillary responses and circadian photoentrainment in adults, no light-induced physiological function is established for these neurons in younger neonates. We tested the hypothesis that ipRGCs mediate light-induced behavior in mice before the onset of rod and cone visual signaling.

Methods: : We tested neonatal mice between the ages of P6 and P9 for phototactic behavior. An animal’s position in a cylindrical chamber was recorded under infrared illumination. Orientation of the pup as a function of time was quantified. Behavior in darkness was compared to that under conditions when a bright light was directed initially towards the face of the animal. Wild type and melanopsin knockout (opn4 -/-) mice were tested.

Results: : Pups turned away from the light, a behavior termed negative phototaxis. Quantitatively, pups spent significantly less total time faced in their original orientation when stimulated with light than in darkness. The latency to the first turn away from their original position was also significantly faster when mice were stimulated with light. No phototactic behavior could be discerned in melanopsin knockout mice.

Conclusions: : These findings indicate that light avoidance is evident in neonatal pups before the onset of visual signaling from rods and cones. Furthermore, the absence of negative phototaxis in melanopsin knockout mice argues strongly that ipRGCs mediate this behavior.

Keywords: ganglion cells • photoreceptors: visual performance • visual development: infancy and childhood 
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