Organization of the axolemma in amyelinated axons: a cytochemical study in dy/dy dystrophic mice

Previous studies using a variety of techniques have shown that in normal myelinated fibres there are structural differences between the axon membrane at nodes of Ranvier and in the internodes beneath the myelin sheath. The present paper reports the results of a cytochemical study on the axon membrane in amyelinated axons in dy/dy dystrophic mice, in which myelination is focally absent owing to a genetic defect. The results indicate that the amyelinated axon membrane, which is known to be capable of sustaining continuous impulse conduction, is structurally different from normal nodal membrane. Comparison of the cytochemical results with physiological and pharmacological data suggests that the amyelinated dystrophic axon membrane may exhibit a lower sodium channel density than normal nodal membrane.