Position-sensitive detector studies of the axonal transport of a pulse of radioisotope.

Axonal transport of a pulse of 35S-methionine-labelled material was studied in vitro in amphibian sciatic nerve using position sensitive detectors. Following formation of a pulse of activity using the cold block technique, the nerve was ligated proximal and distal to the pulse and its movement monitored at room temperature (22.5-23.5 degrees C) for up to 16 h. Material transported in the anterograde direction did so with an average maximum velocity of 147 mm/d. The pulse was found to disperse at an average rate of 0.23 mm/mm travel; however, dispersion was found to vary from preparation to preparation more than would be predicted from experimental error alone. Label was observed to reverse direction at the distal ligature in only 2 of 13 preparations. Reversal of label began within approximately 0.4 h of first arrival, and the most rapidly retrogradely transported material moved at a velocity of 80% that of the most rapidly anterogradely transported material.