Automatic Quantification of the Total Number of S and M/l Cones and Their Detailed Topography in Albino and Pigmented Adult Rats

Abstract

Purpose: : To quantify the whole population of short wavelength cones (S cones) and long-medium wavelength cones (M/L cones) and to study their topographical distribution in the albino (Sprague Dawley, SD) and pigmented (Pieblad Virol Glax, PVG) rats.

Methods: : Whole mounted retinas were double immunodetected with antibodies against UV-sensitive opsin and opsin red/green to detect the S and M/L cones, respectively. An automatic method was developed to quantify the whole population of each type cone. Detailed topographical distribution of S and M/L cones was observed with isodensity maps based upon the quantification data. Mirror distribution of retinal ganglion cells (RGC) and M/L cones was achieved by double immunodetection of Brn3a and Opsin red/green, respectively

Results: : The mean number±SEM of S cones in albino and pigmented strain is 41,028±5,074 and 27,316± 2,235, respectively. In SD retinas there are 231,736±14,517 M/L cones and in PVG ones 239,939±6,494. In the S cones distribution is observed an increasing density gradient along the infero-nasal quadrant, though their highest densities are found in the retinal rim. The topography of S and M/L cones seems to be complementary. The highest densities of M/L cones are observed in the superior naso-temporal axis, paralleling the distribution of Brn3a positive RGCs

Conclusions: : These data ascertain, for the first time, the total number and the topographical distribution of S and M/L cones in two rat strains and demonstrate the correlation of M/L cones and RGC spatial distribution

Keywords: opsins • photoreceptors • color pigments and opsins