Nerves--Growth

Mammals, unlike lower vertebrates, cannot normally regenerate injured central nervous system neurons. Although rat retinal ganglion cells (RGCs), following optic nerve crush, will undergo an initial period of sprouting, axon outgrowth is limited and subsequently aborted. This study examined how extensive the changes in fast transported proteins (FTPs) were during the early response to RGC damage and whether these changes were comparable to those known to occur in lower vertebrate RGCs. Changes in mRNA for several known proteins were also analyzed. It was found that, within 2 days, axotomized rat RGCs initiated a program of cell growth, involving the differential synthesis and transport of a broad range of FTPs. This response is very similar to that of lower vertebrates and indicates that rat RGCs are capable of initiating the metabolic responses necessary for regeneration to begin. This response, however, was not sustained beyond 5 days axotomy.