Recovery of visual behaviors in adult hamsters with the peripheral nerve graft to the sectioned optic nerve

In adult hamsters, the autologous peripheral nerve (PN) was grafted to the sectioned optic nerve to make a bridge to the superior colliculus (SC). Thr ee behavioral tasks were used to test functional recovery of the restored r etinocollicular pathway. First, change of spontaneous ambulating activity t o a decrease in environmental luminance was examined in an open field. PN-g rafted hamsters showed a significant increase to 186% in ambulating activit y just after light off, though it was lower than that in normal hamsters (4 89%). Second, a classical conditioning of total body movements was tested u sing an increase in luminance as a conditioned stimulus (CS) paired with fo ot shocks. In normal hamsters the magnitude of movements during CS increase d in the acquisition period and then decreased in the extinction period in both the second and the third sessions, while the magnitude remained unchan ged in a blind control. PN-grafted hamsters showed an increase in the magni tude only in the third session, although it was statistically barely signif icant (P = 0.0619). Following section of the grafted nerve, the conditioned response disappeared completely. And third, a shuttle-box avoidance task w as examined using a flickering light as CS. Normal hamsters showed improved avoidance scores, while blind controls did not. PN-grafted hamsters showed a slight increase in the score, which was similar to that in the one-eyed control. anterogradely transported labeling of WGA-HRP, injected into the v itreous body of the grafted eye, was observed in the graft and the superfic ial layers of SC. These results confirm and extend our previous finding tha t PN-grafted hamsters can restore some visual function and further suggest that the extent of recovered visual function is as good as in one-eyed anim als. (C) 1999 Academic Press.