C-JUN EXPRESSION IN ADULT-RAT DORSAL-ROOT GANGLION NEURONS - DIFFERENTIAL RESPONSE AFTER CENTRAL OR PERIPHERAL AXOTOMY

The response of the mature central nervous system (CNS) to injury diff ers significantly from the response of the peripheral nervous system ( PNS). Axotomized PNS neurons generally regenerate following injury, wh ile CNS neurons do not. The mechanisms that are responsible for these differences are not completely known, but both intrinsic neuronal and extrinsic environmental influences are likely to contribute to regener ative success or failure. One intrinsic factor that may contribute to successful axonal regeneration is the induction of specific genes in t he injured neurons. In the present study, we have evaluated the hypoth esis that expression of the immediate early gene c-jun is involved in a successful regenerative response. We have compared c-Jun expression in dorsal root ganglion (DRG) neurons following central or peripheral axotomy. We prepared animals that received either a sciatic nerve (per ipheral) lesion or a dorsal rhizotomy in combination with spinal cord hemisection (central lesion). In a third group of animals, severed dor sal roots were placed into the hemisection site along with a fetal spi nal cord transplant. This intervention has been demonstrated to promot e regrowth of severed axons and provides a model to examine DRG neuron s during regenerative growth after central lesion. Our results indicat ed that c-Jun was upregulated substantially in DRG neurons following a peripheral axotomy, but following a central axotomy, only 18% of the neurons expressed c-Jun. Following dorsal rhizotomy and transplantatio n, however, c-Jun expression was upregulated dramatically; under those experimental conditions, 63% of the DRG neurons were c-Jun-positive. These data indicate that c-Jun expression may be related to successful regenerative growth following both PNS and CNS lesions. (C) 1997 Acad emic Press.