The effect of light stimulation or optic nerve transection on the expression of NADPH-d in a sub-population of amacrine cells

Abstract

Purpose: Amongst the variety of amacrine cells in the retina, there is a sub–population of cells expressing NADPH–d (Nicotinamide Adenine Dinucleotide Phosphate–diaphorase). However their roles in the processing of visual information are not well established. This study investigated the effect of light stimulation or optic nerve (ON) transection on the NADPH–d expressing amacrine cells in hamsters. Methods: 4 groups of adult golden hamster were used: a) normal control reared in normal light cycle (12 hours light and 12 hours dark cycle), b) normal dark reared animals, c) ON transection reared in normal light cycle, d) ON transection dark reared animals. The expression of NADPH–d in the ganglion cell layer (GCL) and inner nuclear layer (INL) of the retina was monitored at determined time points (one to four weeks). Results: In the normal control group, the NADPH–d expressing amacrine cells were found in both GCL and INL. In all the other 3 groups of animal: the dark reared normal, the dark reared ON transection, and the ON transection group reared in normal light cycle, the number of NADPH–d expressing amacrine cells in the GCL was down–regulated approximately 40%, whereas in the INL of hamster retina, it did not change significantly. Conclusions: The NADPH–d expressing amacrine cells in GCL and INL of hamster retina were differentially affected by light stimulation or ON transection, as the number of NADPH–d expressing amacrine cells in INL were not affected and yet there was about 40% down–regulation in the GCL in the dark rearing condition or after retinal ganglion cell (RGC) degeneration. This study suggests that the expression of NADPH–d in a sub–population of amacrine cells in GCL is sensitive to light stimulation and functionally dependent on the presence of RGC.