Abstract
Purpose: :
To characterize Brn3a expression in adult albino rat retina and to quantify the population of RGCs expressing Brn3a in naïve as well as its temporal loss induced by intraorbital optic nerve transection (IONT) or crush (IONC).
Methods: :
Brn3a expression was characterized using morphometric methods. RGCs were doubly labelled with the regrotrade neuronal tracer Fluorogold applied to both superior colliculi (SCi), and with antibodies to POU-domain protein Brn3a. Eyes were extracted at increasing survival intervals (2, 5, 9, or 14 days) after axotomy, and the retinas were analyzed to determine the population of RGCs positive for Brn3a and FG.
Results: :
Brn3a expression was limited to the ganglion cell layer. The percentage of RGCs positive for FG and Brn3a in naïve retinas was 92,2%. Quantification of the whole RGC population showed that in naïve retinas there were a mean of 80,251±2210 RGCs-FG+ and 83,449±4541 RGCs-Brn3a+ per retina (mean ±SD; n=14). The temporal course of RGC-Brn3a+ and RGCs-FG+ loss induced by IONC or IONT followed a similar trend, however the loss of RGCs-Brn3a+ was significant earlier than the loss of FG-labelled RGCs.
Conclusions: :
The great majority of the RGCs-FG+ were also Brn3a+, thus Brn3a can be used as a reliable and efficient immunocytochemical marker for RGCs in control and optic nerve injured adult rat retinas. Axotomy induced RGC loss was detected earlier with Brn3a than with FG.
Keywords: retina • ganglion cells • neuroprotection