title: BDNF abolishes the survival effect of NT-3 in axotomized Clarke neurons of adult rats.
abstract: Neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF) have previously been shown to support survival and axonal regeneration in various types of neurons. Also, synergistic neuroprotective effects of these neurotrophins have been reported in descending rubrospinal neurons after cervical spinal cord injury (Novikova et al., [2000] Eur. J. Neurosci. 12:776-780). The present study investigates the effects of intrathecally delivered NT-3 and BDNF on the survival and atrophy of ascending spinocerebellar neurons of Clarke nucleus (CN) after cervical spinal cord injury in adult rats. At 8 weeks after cervical spinal cord hemisection, 40% of the axotomized CN neurons had been lost, and the remaining cells exhibited marked atrophy. Microglial activity was significantly increased in CN of the operated side. Intrathecal infusion of NT-3 for 8 weeks postoperatively resulted in 91% cell survival and a reduction in cell atrophy, but did not reduce microglial activity. In spite of the fact that the CN neurons expressed both TrkC and TrkB receptors, only NT-3 had a neuroprotective effect, whereas BDNF was ineffective. Furthermore, when a combination of BDNF and NT-3 was administered, the neuroprotective effect of NT-3 was lost. The present results indicate a therapeutic potential for NT-3 in the treatment of spinal cord injury, but also demonstrate that in certain neuronal populations the neuroprotection obtained by a combination of neurotrophic factors may be less than that of a single neurotrophin.
authors.affiliation: Department of Integrative Medical Biology, Section for Anatomy, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: L N
authors.initials: LN
authors.lastname: Novikova
authors.forename: L N
authors.initials: LN
authors.lastname: Novikov
authors.forename: J O
authors.initials: JO
authors.lastname: Kellerth
mesh_terms: D000818:Animals; D019771:Axotomy / Q000009:adverse effects*; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects* / Q000502:physiology; D002531:Cerebellum / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D004347:Drug Interactions / Q000502:physiology*; D005260:Female; D017628:Microglia / Q000166:cytology / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D018696:Neuroprotective Agents / Q000494:pharmacology; D020933:Neurotrophin 3 / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D051381:Rats / Q000033:anatomy & histology / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D012183:Retrograde Degeneration / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D013116:Spinal Cord / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D013119:Spinal Cord Injuries / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D018696:Neuroprotective Agents; D020933:Neurotrophin 3; D019001:Nitric Oxide Synthase