Recording of Visually Evoked Potentials and Behavioral Assessment in Light Induced Photoreceptor Degenerated Rats Transferring the Channelrhodopsin-2 Gene

Abstract

Purpose:: To investigate whether a microbial-type rhodopsin, channelopsin-2 restore visual and behavioral responses in light induced photoreceptor degenerated (LD) rats, we transferred the channelopsin-2 gene into the retinal cells using the adeno-associated virus (AAV) vector.

Methods:: To induce the photoreceptor degeneration, adult male Sprague Dawley (SD) rats (6-7 weeks old) were exposed to 3000 lux intensity of fluorescent light for 10 days. The viral vector construct (AAV-Chop2V) for the expression of the Chop2V in the retina was made by subcloning into an adeno-associated virus vector cassette including a CAG promoter. The AAV-Chop2V virus vector was injected into vitreous cavity in eyes of LD rats. The VEP recordings were performed at pre-injection or once a week after the virus vector injection. The Behaivoral assessment was performed using a head-tracking apparatus.

Results:: Amplitudes of visually evoked potentials in SD rats markedly decreased after the exposure of 3000 lux light. The delayed latencies of P1 were recorded. Two weeks after the injection of the AAV-chop2V, increased amplitudes and normal latencies were observed. The amplitudes of VEPs increased depending on the stimulus intensities of blue LED. The fluorescence of Chop2V was observed in inner retinal neurons including ganglion cells.

Conclusions:: The gene therapy using AAV-chop2V can be useful for restoring vision after photoreceptor degeneration.

Keywords: gene transfer/gene therapy • photoreceptors • retina