Growth-associated protein expression in the frontal and occipital cortices of callosotomized rats.

Neurons confined to the central nervous system usually fall to regenerate their axons after injury, although evidence of axonal re-growth has been reported. In this study, rat transcallosal fibres were severed in the midline in order to investigate the reactive plasticity responses in the frontal and occipital cortices of both sides. The expression of growth-associated proteins, tyrosinated alpha-tubulin and GAP-43, was monitored at different time-points post-injury. Protein levels dropped during the first days post-axotomy, but subsequently returned to control levels. This initial decrease could be due, to degeneration, and the subsequent increase connected to the reactive neosynaptogenesis and fibre sprouting from surrounding ipsilateral neurons, which is responsible for the reinnervation of the denervated area. Although transcallosal neurons are usually considered poorly regenerative, their axotomy may therefore induce reactive events.