A Quantitative Analysis of the Effects of the Intraneural Injection of Lysophosphatidyl Choline

Abstract

Some quantitative aspects of the demyelinating lesion, and its progress, produced by the in vivo injection of lysophosphatidyl choline (LPC) into the myelinated peripheral nerves of adult mice have been investigated. The extent of the lesion has been shown to be highly localized to the injection site and dependent on the concentration of LPC. The length of the demyelinating zone appears to be determined within the first hour following the injection. The resulting demyelination occurs in units of whole internodes and over 40% of the fibres involved show the loss of only one internode. The length of the demyelinated zone does not show any obvious dependency on axon diameter. Remyelination has started by day 14 and involves on average the replacement of each original internode by 2 new segments. There is a cellular proliferation in response to the injection, starting within the first week and achieving a maximum between 2-3 weeks. Of the extra cells 70-80% are not axon-associated and of these 50% are supernumary Schwann cells. The use of 14C-oleate and 3H-stearyl LPC indicates that the injected LPC can be converted into lecithin, but also that the fatty acid moiety of LPC becomes distributed amongst the other lipid classes. Pretreatment of the nerve with small amounts of KCN blocks the metabolism of the injected LPC and renders all of the cells subject to lysis.