Publication: Transient Downregulation of Melanopsin Expression After Retrograde Tracing or Optic Nerve Injury in Adult Rats
Authors
Francisco M. Nadal-Nicolás ; Maria H. Madeira ; Manuel Salinas-Navarro ; Manuel Jiménez-López ; Caridad Galindo-Romero ; Arturo Ortín-Martínez ; Ana Raquel Santiago ; Manuel Vidal-Sanz ; Marta Agudo-Barriuso
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Facultades de la UMU::Facultad de Medicina
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Publisher
Association for Research in Vision and Ophthalmology.
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DOI
doi: 10.1167/iovs.15-16963.
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info:eu-repo/semantics/article
Description
Abstract
PURPOSE. To investigate the effect of retrograde tracing or axotomy on melanopsin mRNA expression and immunodetection in albino and pigmented rat retinas.
METHODS. Groups were (1) intact-na¨ıve retinas; (2) optic nerve crush (ONC) analyzed at 7 days (7d) or 2 months (2m); (3) Fluorogold (FG) tracing from the superior colliculi (SCi) analyzed at 7d or 2m; (4) tracing from the intact optic nerve (ON) with FG or hydroxystilbamidine methanesulfonate (OHSt), analyzed 3d later; and (5) sham tracing from the ON or sham surgery. Brn3a and melanopsin were double stained in whole mounts to quantify and assess the distribution of orthotopic and displaced Brn3aþ retinal ganglion cells (Brn3aþRGCs) and melanopsinþRGCs (mþRGCs). Freshly dissected retinas were used for melanopsin mRNA quantitative PCR.
RESULTS. Tracing from the SCi did not affect the number of Brn3aþRGCs or mþRGCs counted in pigmented rats. However, only 55% of mþRGCs were immunodetected in albinos at 7d, although by 2m the mþRGCs counts returned to normal. Optic nerve tracing had a more dramatic effect (38% or 77% of mþRGCs were immunodetected in albino or pigmented rats) that occurred irrespectively of the tracer (OHSt or FG). This effect was not observed in the sham groups. After ONC, Brn3aþRGCs decreased to 37% and 8% by 7d and 2m, respectively. Melanopsin þRGC counts diminished to 30% at 7d, but recovered to 49% of controls by 2m. Melanopsin mRNA was downregulated after ON tracing or 7d after ONC, but did not differ from intact values 2m after ONC.
CONCLUSIONS. Following ON injury or retrograde tracing there is a transient melanopsin downregulation that should be taken into account when assessing mþRGC survival.
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Citation
Invest Ophthalmol Vis Sci. 2015 Jul;56(8):4309-23.
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