Selective Impairments of ON/OFF–Center Retinal Ganglion Cells in Short–Term Diabetes

Abstract

Purpose: : The dendritic field positions in the inner plexiform layer (IPL) were observed to detect the selective impairments of ON/OFF–center retinal ganglion cells (RGC) in short–term diabetes.

Methods: : The somas and dendritic fields of RGCs in the isolated retinas of the rat streptozotocin (STZ)–induced diabetes model were labeled in detail by using gene gun techniques. The isolated retinas were incubated in oxygenated Ames solution containing 1 mg/ml 4,6–diamidino–2– phenynolindole (DAPI, Sigma D9542, St. Louis, MO), being constantly bubbled with 95% O2 and 5% CO2 for 1 h to stain all cells in the retina. We collected data from the RGCs with a Leica DMRA microscope equipped with a Spot cooled CCD camera for comparison. The DAPI–labeled somas were used to estimate the dendritic stratification of ganglion cells in the IPL. The level of stratification was defined as 0–100% from the border of the inner nuclear layer to border of the ganglion cell layer and measured by the z–axis reading on the Leica DMRA microscope. RGCs were classified into ON/OFF–center RGC according to the rule that most RGCs with dendritic field positions in the 0–40% IPL were OFF–center RGCs while the one with dendritic field positions in the 40–100% IPL were ON–center RGC.

Results: : We collected 368 well classified RGCs in the 3–month diabetic rats, which were divided into ON–center RGC group and OFF–center RGC group. The dendritic field positions in IPL of OFF–center RGCs shifted towards the inner nuclear layer (P<0.001), especially in RG_B and RG_C. No obvious changes detected in ON–center RGC group.

Conclusions: : RGCs were classified into ON/OFF–center RGC according to the dendritic field position in the IPL. This classification has been confirmed by their electricity behavior before. The scale of the ON/OFF–center RGC in a normal retina is almost 1:1, which is considered in strong relationship with the contrast sensitivity and so the disturb on dendrites position in the IPL of OFF–center RGCs may contribute to the deterioration of contrast sensitivity in short–term diabetes.

Keywords: diabetes • retinal degenerations: cell biology • shape and contour