SPROUTING OF AXON-LIKE PROCESSES FROM AXOTOMIZED RETINAL GANGLION-CELLS IS INFLUENCED BY THE DISTANCE OF AXOTOMY FROM THE CELL BODY AND THEMODE OF TRANSPLANTATION OF THE PERIPHERAL-NERVE

It is a well known fact that the proximity of an axonal lesion from th e cell body influences the degree of neuronal survival: a lesion close to the cell body leads to more severe cell death and vice versa. On t he other hand, experiments involving transplantation of a peripheral n erve (PN) to various central nervous system (CNS) regions to induce ax onal regeneration have suggested that axonal regrowth is more vigorous when the grafting is performed closer to the cell body. It is not cle ar, however, whether it is the distance of the site of axotomy or the location of the trophic source (PN graft) or both from the cell body w hich dictates the vigorousness of axonal regrowth. Using either a mode l of transplantation of a PN to the retina or implantation of a short PN into the vitreous body of the eye of the adult hamster, we have dem onstrated that sprouting of axon-like processes from retinal ganglion cells (RGCs) depends on the distance of axotomy from the cell body whe n the PN graft is maintained at a constant distance from the cell body . Moreover, it was found that the distance of axotomy at which sprouti ng of axon-like processes could be induced was different for the 2 par adigms: with the intravitreal PN model, sprouting was observed even af ter intracranial ON cut whereas it was absent in the PN grafting-to-re tina paradigm. This suggests that extrinsic influence (in this case an intravitreal PN) can overcome to a certain extent the growth-suppress ive effects due to a long distance of axotomy.