title: Injury-associated induction of GAP-43 expression displays axon branch specificity in rat dorsal root ganglion neurons.
abstract: Peripheral nerve injury results in the increased synthesis and axonal transport of the growth-associated protein GAP-43 in dorsal root ganglion (DRG) neurons, coincident with regenerative growth of the injured peripheral axon branches. To determine whether the injury-associated signalling mechanism which leads to GAP-43 induction also operates through the central branches of DRG axons, we used immunocytochemistry to compare the expression of GAP-43 in adult rat DRG neurons 2 weeks after dorsal root crush lesions (central axotomy) or peripheral nerve crush lesions (peripheral axotomy). In uninjured ganglia, a subpopulation of smaller DRG neurons expresses moderate levels of GAP-43, whereas larger neurons generally do not. At 2 weeks following peripheral axotomy, virtually all axotomized neurons, large and small, express high levels of GAP-43. At 2 weeks following dorsal root lesions, no increase in GAP-43 expression is detected. Thus, the injury-associated up-regulation of GAP-43 expression in DRG neurons is triggered by a mechanism that is responsive to injury of only the peripheral, and not the central, axon branches. These findings support the hypothesis that GAP-43 induction in DRG neurons is caused by disconnection from peripheral target tissue, not by axon injury per se.
authors.affiliation: Department of Physiology, Queen's University, Kingston, Canada.
authors.forename: D J
authors.initials: DJ
authors.lastname: Schreyer
authors.forename: J H
authors.initials: JH
authors.lastname: Skene
mesh_terms: D000818:Animals; D001369:Axons / Q000276:immunology / Q000378:metabolism*; D019922:GAP-43 Protein; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism*; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000276:immunology; D009409:Nerve Crush; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000276:immunology; D009474:Neurons / Q000276:immunology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000502:physiology
chemical_list: D019922:GAP-43 Protein; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins