Anterograde and retrograde transport of horseradish peroxidase isoenzymes in the retino-tectal fibres of xenopus larvae

Abstract

Commercial horseradish peroxidase (HRP) was separated into basic and acidic isoenzyme fractions. The ability of each of these two fractions to be taken up and transported by nerve vells was tested in the retino-tectal tract of Xenopus laevis at midlarval stages. HRP isoenzymes were injected with a glass micropipette into the eye, while scratching the optic disc to break the axons of ganglion cells leaving the retina. Both basic and acidic HRP were taken up by broken optic fibres and transported anterogradely. The same HRP preparations were delivered to the nerve endings of retinal ganglion cells by injecting them into the optic tectum. Uptake and retrograde transport could be demonstrated with basic HRP, but not with acidic HRP. Results are schematically shown in Fig. 3. The different behaviour of HRP isoenzymes could be exploited in neuroanatomical tracing techniques.