A horseradish peroxidase procedure for tracing the central projections of peripheral nerves in exsanguinated...

This report outlines a procedure for demonstrating the central connections of peripheral nerves in anamniotes by exposing the nerves to horseradish peroxidase (HRP) subsequent to perfusion of the animal with cold saline. The tissue is fixed by immersion after a 6-10 h exposure to the HRP, embedded, sectioned and finally reacted using tetramethylbenzidine as a chromogen. The pattern of afferent projections of the posterior lateral line nerve in the teleost fish Crenicichla as demonstrated by this 'pre-perfused' technique is very similar to the pattern seen when using a standard HRP procedure requiring a post-operative survival period. The utility of the pre-perfused technique is discussed.