Dorsal column sensory axons lack TrkC and are not rescued by local neurotrophin-3 infusions following spinal cord contusion in adult rats. 2007

K Adam Baker, and Shojiro Nakashima, and Theo Hagg
Kentucky Spinal Cord Injury Research Center, Department of Neurological Surgery, MDR Building, Room 616, University of Louisville, Louisville, KY 40292, USA.

By reducing the progressive degeneration and disconnection of axons following spinal cord injury the functional outcome should improve. After direct transection of dorsal column sensory axons, neurotrophin-3 (NT-3) treatment can reduce degeneration and promote regeneration of the proximal stumps. Here, we tested in adult rats whether NT-3 infusion at the site of a moderate T9 spinal cord contusion would rescue sensory connections to the gracile nucleus in the medulla. Sensory projections were anterogradely traced bilaterally with injections of cholera toxin B (CTB) into the sciatic nerve 3 days before analysis. Seven days after the contusion plus intrathecal (subarachnoid) vehicle infusion as a control, the CTB-positive innervation of the gracile nucleus was reduced to approximately 25% of sham-operated rats. Intrathecal infusion of 10 microg/day of NT-3 did not affect this reduced innervation. To ensure good tissue penetration and high concentrations of NT-3 early after the injury, other rats received intraparenchymal infusions of vehicle or NT-3 near the injury site starting 2 days before until 7 days after the injury. This NT-3 treatment also did not affect the reduced innervation. This suggests that local NT-3 treatments cannot protect sensory axons from secondary degeneration after a contusive spinal cord injury. These results are likely because TrkC is not present in axons of the dorsal columns or gracile nucleus, or in other dorsal column cell types, even after the contusion. Together with published results, our data suggest that NT-3 is a peripherally--but not centrally--derived neurotrophic factor for sensory neurons.

UI MeSH Term Description Entries
D008526 Medulla Oblongata The lower portion of the BRAIN STEM. It is inferior to the PONS and anterior to the CEREBELLUM. Medulla oblongata serves as a relay station between the brain and the spinal cord, and contains centers for regulating respiratory, vasomotor, cardiac, and reflex activities. Accessory Cuneate Nucleus,Ambiguous Nucleus,Arcuate Nucleus of the Medulla,Arcuate Nucleus-1,External Cuneate Nucleus,Lateral Cuneate Nucleus,Nucleus Ambiguus,Ambiguus, Nucleus,Arcuate Nucleus 1,Arcuate Nucleus-1s,Cuneate Nucleus, Accessory,Cuneate Nucleus, External,Cuneate Nucleus, Lateral,Medulla Oblongatas,Nucleus, Accessory Cuneate,Nucleus, Ambiguous,Nucleus, External Cuneate,Nucleus, Lateral Cuneate
D009410 Nerve Degeneration Loss of functional activity and trophic degeneration of nerve axons and their terminal arborizations following the destruction of their cells of origin or interruption of their continuity with these cells. The pathology is characteristic of neurodegenerative diseases. Often the process of nerve degeneration is studied in research on neuroanatomical localization and correlation of the neurophysiology of neural pathways. Neuron Degeneration,Degeneration, Nerve,Degeneration, Neuron,Degenerations, Nerve,Degenerations, Neuron,Nerve Degenerations,Neuron Degenerations
D009475 Neurons, Afferent Neurons which conduct NERVE IMPULSES to the CENTRAL NERVOUS SYSTEM. Afferent Neurons,Afferent Neuron,Neuron, Afferent
D002408 Catheters, Indwelling Catheters designed to be left within an organ or passage for an extended period of time. Implantable Catheters,In-Dwelling Catheters,Catheter, In-Dwelling,Catheter, Indwelling,Catheters, In-Dwelling,In Dwelling Catheters,In-Dwelling Catheter,Indwelling Catheter,Indwelling Catheters
D002772 Cholera Toxin An ENTEROTOXIN from VIBRIO CHOLERAE. It consists of two major protomers, the heavy (H) or A subunit and the B protomer which consists of 5 light (L) or B subunits. The catalytic A subunit is proteolytically cleaved into fragments A1 and A2. The A1 fragment is a MONO(ADP-RIBOSE) TRANSFERASE. The B protomer binds cholera toxin to intestinal epithelial cells and facilitates the uptake of the A1 fragment. The A1 catalyzed transfer of ADP-RIBOSE to the alpha subunits of heterotrimeric G PROTEINS activates the production of CYCLIC AMP. Increased levels of cyclic AMP are thought to modulate release of fluid and electrolytes from intestinal crypt cells. Cholera Toxin A,Cholera Toxin B,Cholera Toxin Protomer A,Cholera Toxin Protomer B,Cholera Toxin Subunit A,Cholera Toxin Subunit B,Choleragen,Choleragenoid,Cholera Enterotoxin CT,Cholera Exotoxin,Cholera Toxin A Subunit,Cholera Toxin B Subunit,Procholeragenoid,Enterotoxin CT, Cholera,Exotoxin, Cholera,Toxin A, Cholera,Toxin B, Cholera,Toxin, Cholera
D003288 Contusions Injuries resulting in hemorrhage, usually manifested in the skin. Bruise,Bruises,Contusion
D004334 Drug Administration Schedule Time schedule for administration of a drug in order to achieve optimum effectiveness and convenience. Administration Schedule, Drug,Administration Schedules, Drug,Drug Administration Schedules,Schedule, Drug Administration,Schedules, Drug Administration
D005260 Female Females
D000344 Afferent Pathways Nerve structures through which impulses are conducted from a peripheral part toward a nerve center. Afferent Pathway,Pathway, Afferent,Pathways, Afferent
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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