Distinct sprouting responses of sympathetic and peptidergic sensory axons proximal to a sciatic nerve transection in guinea pigs and rats

Sprouting of sympathetic and peptidergic sensory neurones proximal to nerve lesions may reflect upregulation of growth factors around damaged dorsal r oot ganglion (DRG) cells. Axons containing noradrenaIine or calcitonin gene -related peptide were visualized in DRGs and spinal roots of guinea pigs an d rats. After sciatic transection in rats, varicose terminals of both types appeared around large DRG somata. These neurones were surrounded by prolif erated satellite cells expressing glial fibrillary acidic protein (GFAP) an d p75. This did not occur in guinea pigs. Instead, sympathetic axons grew t hrough the DRG and centrally along the dorsal roots (which contained p75-po sitive glia), avoiding the DRG somata. Thus the glial reaction to periphera l injury differs between species such that, in guinea pigs, the environment in the spinal roots rather than in the DRGs favours sympathetic sprouting. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.