Re-emergence of GAP-43 in cochlear nucleus and superior olive following cochlear ablation in the rat

The effect of cochlear lesion on the expression of the growth associated protein GAP-43 in superior olive and cochlear nucleus was studied in the rat. In normal development of these auditory brainstem nuclei, GAP-43 immunoreactivity is high perinatally but low 10 days postnatally or thereafter. Removal of one spiral ganglion in grown-up animals caused a substantial re-emergence of GAP-43 immunoreactivity in varicose fibers of the ipsilateral ventral cochlear nucleus and cell bodies of the lateral superior olive. These findings suggest that a reactive synaptogenesis takes place in the cochlear nucleus as a consequence of deafening through spiral ganglion loss.