Distribution of peroxidase activity at nodes of Ranvier after intramuscular administration of horseradish peroxidase in the cat.

The occurrence of intra-axonal peroxidase activity in large myelinated nerve fibres to the plantaris longus muscle of the cat was investigated histochemically 10-12 h after intramuscular administration of horseradish peroxidase. Internodal horseradish peroxidase activity was low. Its demonstration required electron microscopical analysis of serial sections. In contrast to this, many nodal regions did, even in the light-microscope, disclose a high and characteristically distributed horseradish peroxidase activity. At such nodes the distal part of the constricted axon segment was crowded with horseradish peroxidase-positive bodies of which several were of the so-called multivesicular type. The proximal part of the constricted axon segment was almost free of horseradish peroxidase-positive bodies and contained a densely-packed vesiculotubular membranous system. This striking polarization of the nodal axon region is discussed and tentatively interpreted as the consequence of a physiological damming-up of both somatofugally- and somatopetally-transported materials.