title: Impairment of intrinsically photosensitive retinal ganglion cells associated with late stages of retinal degeneration.
abstract: OBJECTIVE
  To evaluate quantitative and qualitative age-related changes in intrinsically photosensitive melanopsin-containing retinal ganglion cells (ipRGCs) in transgenic P23H rats, an animal model of autosomal dominant retinitis pigmentosa (RP) was examined.
  
  
  METHODS
  ipRGC density, morphology, and integrity were characterized by immunohistochemistry in retinas extracted from P23H and Sprague-Dawley (SD) rats aged 4, 12, and 18 months. Differences between SD and P23H rats throughout the experimental stages, as well as the interactions among them, were morphologically evaluated.
  
  
  RESULTS
  In rat retinas, we have identified ipRGCs with dendrites stratifying in either the outer margin (M1) or inner side (M2) of the inner plexiform layer, and in both the outer and inner plexuses (M3). A small group of M1 cells had their somas located in the inner nuclear layer (M1d). In SD rats, ipRGCs showed no significant changes associated with age, in terms of either mean cell density or the morphologic parameters analyzed. However, the mean density of ipRGCs in P23H rats fell by approximately 67% between 4 and 18 months of age. Moreover, ipRGCs in these animals showed a progressive age-dependent decrease in the dendritic area, the number of branch points and terminal neurite tips per cell, and the Sholl area.
  
  
  CONCLUSIONS
  In the P23H rat model of retinitis pigmentosa, density, wholeness, and dendritic arborization of melanopsin-containing ganglion cells decrease in advanced stages of the degenerative disease.
authors.affiliation: Department of Physiology, Genetics and Microbiology, University of Alicante, Alicante, Spain.
authors.forename: Gema
authors.initials: G
authors.lastname: Esquiva
authors.forename: Pedro
authors.initials: P
authors.lastname: Lax
authors.forename: Nicolás
authors.initials: N
authors.lastname: Cuenca
mesh_terms: D000375:Aging / Q000473:pathology*; D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology*; D012174:Retinitis Pigmentosa / Q000473:pathology*; D017299:Rod Opsins / Q000378:metabolism; D000099210:Melanopsin
chemical_list: D017299:Rod Opsins; D000099210:Melanopsin
keywords: P23H rats; immunoperoxidase; ipRGCs; melanopsin; retinitis pigmentosa