title: Postnatal development and functional adaptations of the melanopsin photoreceptive system in the albino mouse retina.
abstract: OBJECTIVE
  To study the melanopsin system of the albino CD1 mouse retina during postnatal development.
  
  
  METHODS
  Pups were kept under different ambient conditions: light/dark (LD) cycles, constant light (LL), constant darkness (DD), LL followed by LD, and DD followed by LL. Using immunohistochemistry, melanopsin-expressing cells were classified as M1 or M2 according to the location of their somata and dendritic processes and were counted.
  
  
  RESULTS
  Under LD cycles an increase in the number of immunoreactive cells was observed within the first week of postnatal development. When mice were maintained in DD, the increase in the number of immunopositive cells detected was significantly higher than that in LD. On the contrary, when mice were exposed to LL within the same period, no increase was detected. To determine whether the effect of LL during the early postnatal period was reversible, the authors studied animals born in LL and subsequently maintained under LD cycles. After 3 days in LD, these animals showed a significant increase in melanopsin cell number. However, after 1 month in LD, the number was similar to that of the LD controls. Surprisingly, when mice born in DD were exposed to LL, no decrease was detected, though the immunostaining was of low intensity.
  
  
  CONCLUSIONS
  The amount of melanopsin protein per cell varies, depending on ambient light conditions. Periods of darkness or, more likely, the sequence of light and dark periods occurring under the daily cycles might be necessary for the normal development of the melanopsin system.
authors.affiliation: Department of Morphology and Cell Biology, Oviedo University, Oviedo, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: González-Menéndez
authors.forename: Felipe
authors.initials: F
authors.lastname: Contreras
authors.forename: Rafael
authors.initials: R
authors.lastname: Cernuda-Cernuda
authors.forename: Ignacio
authors.initials: I
authors.lastname: Provencio
authors.forename: José M
authors.initials: JM
authors.lastname: García-Fernández
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology*; D000417:Albinism / Q000378:metabolism* / Q000503:physiopathology*; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000378:metabolism; D003623:Dark Adaptation / Q000502:physiology; D003624:Darkness; D003712:Dendrites / Q000378:metabolism; D005260:Female; D007150:Immunohistochemistry; D008029:Lighting; D051379:Mice; D008809:Mice, Inbred C3H; D017440:Photoperiod; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism* / Q000648:ultrastructure; D010858:Pigmentation / Q000502:physiology; D011247:Pregnancy; D012160:Retina / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D017299:Rod Opsins / Q000378:metabolism*; D000099210:Melanopsin
chemical_list: D017299:Rod Opsins; D000099210:Melanopsin