IMPLANTATION OF PNS GRAFT INHIBITS THE INDUCTION OF NEURONAL NITRIC-OXIDE SYNTHASE AND ENHANCES THE SURVIVAL OF SPINAL MOTONEURONS FOLLOWING ROOT AVULSION

In a spinal root injury model, our previous studies have shown that in duction of nitric oxide synthase (NOS) appears only in spinal motoneur ons of the root-avulsed segment in which significant motoneuron loss o ccurs but not in those of the distal root-axotomized segment (root axo tomy 5-10 mm from the spinal cord) in which most motoneurons survive t he injury. One hypothesis for the different response of motoneurons to root avulsion and distal root axotomy is that neurotrophic factors pr oduced by the remaining peripheral nervous system (PNS) component are available for the distally axotomized motoneurons but are not availabl e following avulsion. This hypothesis is tested in the present study b y implantation of a PNS graft following the root avulsion. Results of the present study show that implantation of a PNS graft significantly enhances the survival of motoneurons following avulsion. Expression of NOS due to avulsion injury is completely inhibited in all motoneurons that regrow into the PNS graft. These results indicate that induction of NOS in avulsed motoneurons may result from the deprivation of neur otrophic factors produced by the PNS component, and the survival promo ting effects of neurotrophic factors may be achieved by modifying cert ain cellular molecules such as NOS. (C) 1994 Academic Press, Inc.