NEITHER INTRAOCULAR GRAFTS OF RETINAL CELL HOMOGENATES NOR LIVE NON-RETINAL NEURONS PRODUCE BEHAVIORAL RECOVERY IN RATS WITH LIGHT-DAMAGED RETINAS

Previously we have observed that fetal retinal cells grafted to the su bretinal space of blind rats produced a functional recovery as determi ned by testing the visual inhibition of the startle response. Followin g those studies, we performed experiments to test whether the injectio n itself, cell by-products, or unrelated neural cells could also produ ce an effect. Visual function was tested by examining the inhibitory e ffect of a brief light flash (300 lx) on the acoustic startle response to an immediately following intense noise burst in light blinded Fisc her 344 rats. Animals were tested before and after grafts of fetal ret inal cell homogenates, dissociated perinatal cerebellar cells, and sha m injections in the subretinal space. Behavioral testing continued eve ry 2 wk for 14 wk after the graft. In the pretests, the light flash in hibited the startle response, maximal at intervals of 40-70 ms with re covery thereafter. In contrast, after exposure or 4 wk to fluorescent light (300 lx) and a rest in a normal 12/12 h light/dark environment t he rats showed reflex facilitation to the light, maximal at an interva l of 110 ms, followed by a late period of reflex inhibition. The light flash had no effect on other rats that had been blinded by bilateral enucleation. Light blinded animals receiving either cerebellar grafts or retinal cell homogenates were no different in performance from thei r sham injected control animals. The present data suggest that neither subretinal injections of neural cells nor nonspecific neurochemical f actors are able to elicit a positive behavioral response in visually i mpaired animals.