Resealing of transected myelinated mammalian axons in vivo: Evidence for involvement of calpain

M. J. Howard, G. David, J. N. Barrett

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

The mechanisms underlying resealing of transected myelinated rat dorsal root axons were investigated in vivo using an assay based on exclusion of a hydrophilic dye (Lucifer Yellow-biocytin conjugate). Smaller caliber axons (<5μm outer diameter) resealed faster than larger axons. Resealing was Ca2+ dependent, requiring micromolar levels of extracellular [Ca2+] to proceed, and further accelerated in 1mM Ca2+. Two hours after transection, 84% of axons had resealed in saline containing 2mM Ca2+, 28% had resealed in saline containing no added Ca2+ and only 3% had resealed in the Ca2+ buffer BAPTA (3mM). The enhancing effect of Ca2+ could be overcome by both non-specific cysteine protease inhibitors (e.g., leupeptin) and inhibitors specific for the calpain family of Ca2+-activated proteases. Resealing in 2mM Ca2+ was not inhibited by an inhibitor of phospholipase A2. Resealing in low [Ca2+] was not enhanced by agents which disrupt microtubules, but was enhanced by dimethylsulfoxide (0.5-5%).These results suggest that activation of endogenous calpain-like proteases by elevated intra-axonal [Ca2+] contributes importantly to membrane resealing in transected myelinated mammalian axons in vivo. Copyright (C) 1999 IBRO.

Original languageEnglish (US)
Pages (from-to)807-815
Number of pages9
JournalNeuroscience
Volume93
Issue number2
DOIs
StatePublished - Jul 1 1999

Keywords

  • Axon
  • Calcium
  • Calpain
  • Dimethylsulfoxide
  • Mechanical injury
  • Membrane resealing

ASJC Scopus subject areas

  • Neuroscience(all)

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