GAP-43 (B-50) and C-Jun are up-regulated in axotomized neurons of Clarke'snucleus after spinal cord injury in the adult rat

The growth-associated protein GAP-43 (B-50) and the transcription factor C- Jun are involved in regeneration of the injured nervous system. In this stu dy, we investigated the possibility of the induction of GAP-43 and C-Jun in axotomized neurons of Clarke's nucleus (CN) in adult rats, of which a larg e population undergoes degeneration several weeks after a low thoracic late ral funiculotomy of the spinal cord. In situ hybridization and immunohistoc hemistry revealed a transient up-regulation of GAP-43 mRNA, C-Jun protein, and its activated, phosphorylated form, peaking around 7 days after injury in preferentially large diameter ON-neurons ipsilateral and caudal to the l esion. Our results document that some populations of axotomized central ner vous system neurons, similar to axotomized regenerating neurons of the peri pheral nervous system, can up-regulate GAP-43 and C-Jun, even if they are d estined to degenerate. This might reflect a transient regenerative capacity , which fails overtime. (C) 1999 Academic Press.