Abstract
Methods: Spiking activity of retinal ganglion cells (RGCs) in retinal patches adjacent to and distant from the point of the injection of a recombinant adeno-associated virus delivering halorhodopsin was tested using multi electrode array recording. Retinal patches were stimulated with 455 nm light of different duration/intensity.
Results: Light responses were observed in 48 out of 71 RGCs identified in the retinal patch adjacent to the injection point. Observed light responses could be grouped into four main types: sustained ON- (7 cells), transient ON- (22 cells), fast developing OFF- (11 cells) and slow developing OFF-responses (peak at ~2 s after stimulation offset, 8 cells). RGCs firing returned to basal levels rather slowly (up to 5 s); at least 18 s in the dark was needed for restoration of the response amplitude during repetitive stimulations. Maximum response amplitude was up to 60–80 Hz depending on the cell type. Robust responses were observed at the low intensity level of just 0.1 mW/cm2. No light responses were observed in the control (untreated) retinal patch.
Conclusions: Partial restoration of the visual function in the treated canine retina was confirmed by the observation of the robust and diverse ON- and OFF- RGC responses at low intensity levels while only basal firing was detected in the control retinal patch at all light intensities. Further work is required to improve halorhodopsin kinetics in order to resolve higher frequency visual stimuli.
Support: NEI 8DP1 EY023177, NEI P30 EY01583 (Vision Research Core of the University of Pennsylvania)