Quantitative demonstration of the retrograde axonal transport of endogenous nerve growth factor

The level of endogenous nerve growth factor (NGF) in rat sciatic nerve was determined using a highly sensitive two-site enzyme immunoassay. After crushing this nerve NGF accumulated linearly distal to the crush during the first 12 h to reach levels 13-fold higher than in the uncrushed contralateral side. In contrast, proximal to the crush NGF levels approached or were below the detection limit of the assay. The asymmetrical distribution of NGF on the two sides of a crush is direct evidence for the retrograde axonal transport of endogenous NGF.