Biotin-dextran: fast retrograde tracing of sciatic nerve motoneurons.

We present evidence that biotin-dextran (BD) provides good fast retrograde tracing in the rat sciatic nerve. Using BD injected distal to a crush injury of either tibial or common peroneal nerves, spinal cord motoneuron counts after 48 h compare favorably with counts obtained using horseradish peroxidase. Advantages of BD include fine staining of the soma and its branches, increasing the reliability of motoneuron counting, as well as good staining of sciatic nerve axons 30 mm away from the crush site. BD, already demonstrated to be a good anterograde tracer in the central nervous system, is shown to be a good retrograde tracer in a peripheral nervous system model.