Rhodopsin P347L transgenic (Tg) rabbit, a medium-sized animal model of retinitis pigmentosa (RP), is considered to play an important role in the research and development of RP. Therefore, it is essential to understand the changes in the visual function and retinal structure of Tg rabbits. We evaluated the visual function by recording electroretinograms (ERG) and electrically evoked potentials (EEPs) elicited after transcorneal electrical stimulation and histopathologically analyzed the structural changes in the excised eyeball and optic nerve. According to ERG results, it was observed that the rod function almost completely disappeared at approximately 12 months of age and the cone function disappeared at 54 months of age. In the process of retinal degeneration until ERG disappearance, it was confirmed that not only the oscillatory potentials and ON bipolar cell component, which have been confirmed in the previous reports, but also the OFF bipolar cell component was enhanced in Tg rabbits. EEPs were recordable even in Tg rabbits with severe retinal degeneration, in which the ERG disappeared, suggesting that the optic nerve function was intact. Conversely, amplitudes of the first positive wave (P1) were significantly reduced in Tg rabbits compared to that in wild-type rabbits. The number of optic nerve axons was also significantly reduced in Tg rabbits compared to that in wild-type rabbits. However, the degree of reduction in the amplitude of P1 was greater than the degree of reduction in the number of optic nerve axons. Therefore, while considering artificial retinal treatment, it is necessary to pay attention to the difference between changes in EEPs and changes in the number of optic nerve axons.
Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 125: 1003-1012,2021.