The effects of lysolecithin on non-myelinated axons in vitro.

Abstract

Previous work showed that lysolecithin injected into rat sciatic nerve produced axonal degeneration of non-myelinated fibres. The possibility was raised that the swollen axons observed proximal to the injection site were the cause rather than the result of axonal degeneration (Mitchell and Caren 1982). The two main objectives of the present study were to examine the effects of different concentrations of lysolecithin on a nerve composed mainly of nonmyelinated fibres and by histochemical means, to study axoplasmic transport in the lysolecithin exposed nerves. The guinea-pig inferior mesenteric ganglion (IMG) and its associated hypogastric nerves, which were ligated, was placed in a three compartment chamber and maintained in vitro for 24 h at 37° C. This in vitro preparation was chosen because the concentration of lysolecithin added to the hypogastric nerves could be accurately measured and axonal transport in the lysolecithin-exposed nerves could be studied using two different methods. Horseradish peroxidase (HRP) applied to the ligated nerve compartment was used to study retrograde transport and the endogenous noradrenaline (NA) content of the sympathetic hypogastric nerves was used to study orthograde transport. The lysolecithin-induced changes were dose dependent and similar to those observed previously in vivo. When the damage was restricted to Schwann cells both HRP and NA were transported along the axons in the lysolecithin-exposed segment of nerve. Only when the lysolecithin produced ultrastructural evidence of axonal degeneration was there any observed accumulation of HRP or NA. These results and the value of this preparation for studying the effects of different toxins on nonmyelinated fibres are discussed.