Behavior tests and immunohistochemical retinal response analyses in RCS rats with subretinal implantation of Okayama University-type retinal prosthesis Short title: Behavior tests in rats with retinal prostheses

We have developed a photoelectric dye-coupled polyethylene film as a prototype of retinal prosthesis, named “Okayama University-type retinal prosthesis. The purposes of this study are to conduct behavior tests to assess vision in Royal College of Surgeons (RCS) rats which underwent subretinal implantation of the dye-coupled film, and are also to reveal the retinal response to the dye-coupled film by immunohistochemistry. Polyethylene films were made of polyethylene powder at refined purity, and photoelectric dyes were coupled to the film surface at higher density, compared with the prototype. The dye-coupled film or the dye-uncoupled plain film, as a control, was implanted subretinally from a scleral incision in both eyes of a RCS rat at 6 weeks of the age. Behavior tests, 2, 4, 6, and 8 weeks after the implantation, were conducted by observing head-turning or body-turning in the direction, consistent with clockwise or anticlockwise rotation of a black-and-white-striped drum around a transparent cage, housed with a rat. After the behavior tests at 8 weeks, rats’ eyes were enucleated to confirm the subretinal implantation of the films and were processed for immunohistochemistry. In the behavior tests, the number of head-turning, consistent with the direction of the drum rotation, was significantly larger in RCS rats with dye-coupled film implantation, compared with rats with plain film implantation (P<0.05,