Intraspinal sprouting of rat primary afferents after deafferentation

To test intraspinal sprouting of primary afferent fibers, unilateral chronic, followed by contralateral acute, dorsal rhizotomies were done 3 segments above and below a spared segment (T9) in rats. Following perfusion with 4% paraformaldehyde, T9 spinal cord segments were frozen, sectioned and reacted by a modified Gomori procedure for fluoride-resistant acid phosphatase (FRAP) enzyme activity, a marker for primary afferent terminals. As determined by light microscopy, there was greater and extended FRAP reaction product in laminae I and II on the chronically denervated side than on the contralateral acutely denervated side. These data support the hypothesis of axonal sprouting and synaptogenesis of primary afferent fibers after spinal cord deafferentation.