title: The astrocytic barrier to axonal regeneration at the dorsal root entry zone is induced by rhizotomy.
abstract: After dorsal rhizotomy, sensory axons fail to regenerate beyond the astrocytic glia limitans at the dorsal root entry zone (DREZ) but this inhibition can be overcome with the delivery of exogenous neurotrophin-3. We investigated whether axonal inhibition at the DREZ is constitutive or induced after dorsal rhizotomy. Primary afferent neurones from enhanced green fluorescent protein-expressing mice were transplanted into adult rat dorsal root ganglia in the presence or absence of dorsal rhizotomy. In the absence of dorsal rhizotomy mouse axons freely extended into the rat central nervous system. After host dorsal rhizotomy, mouse axons were unable to cross the DREZ. However, in rats that received a dorsal rhizotomy concomitant with intrathecal neurotrophin-3, the mouse axons were able to cross the DREZ. These results indicate that, under normal circumstances, the adult DREZ is permissive to the regeneration of adult sensory axons and that it only becomes inhibitory once dorsal root axons have been injured and astrocytes at the DREZ have become reactive.
authors.affiliation: ICORD (International Collaboration On Repair Discoveries), The University of British Columbia, Biosciences Building, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Lowell T
authors.initials: LT
authors.lastname: McPhail
authors.forename: Ward T
authors.initials: WT
authors.lastname: Plunet
authors.forename: Partha
authors.initials: P
authors.lastname: Das
authors.forename: Matt S
authors.initials: MS
authors.lastname: Ramer
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D001369:Axons / Q000187:drug effects / Q000502:physiology* / Q000637:transplantation; D002490:Central Nervous System / Q000502:physiology; D003952:Diagnostic Imaging / Q000379:methods; D005727:Ganglia, Spinal / Q000502:physiology* / Q000637:transplantation; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D051379:Mice; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology*; D009475:Neurons, Afferent / Q000378:metabolism / Q000502:physiology / Q000637:transplantation; D020933:Neurotrophin 3 / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D019051:Rhizotomy / Q000379:methods*; D012583:Schwann Cells / Q000502:physiology
chemical_list: D005904:Glial Fibrillary Acidic Protein; D020933:Neurotrophin 3; D049452:Green Fluorescent Proteins