Dependence of GAP43 (B50, F1) transport on axonal regeneration in rat dorsal root ganglion neurons.

The axonal transport of protein GAP43 (B50, F1) has been studied in rat sciatic nerve after application of L-[35S]methionine to the lumbar dorsal root ganglia. Within 24 h of a crush axotomy of the sciatic nerve a significant increase in labelling of transported GAP43 was detected. After 14 days, levels were approximately 60 times greater than in normal nerve, and thereafter declined, returning to the normal range by 114 days. In contrast, after a resection, which impeded regeneration, transport of labelled GAP43 remained elevated for at least 114 days. I conclude that GAP43 synthesis is regulated by a suppressive factor derived from the periphery which is depleted by axotomy and restored by regeneration. The time-course of down-regulation of GAP43 synthesis during regeneration is consistent with the target tissues being the source of the factor.