Axonal sprouting of motor nerve in acrylamide-intoxicated rats with progressive weakness.

Quantitative morphologic studies on the motor axons in endplates of extensor digitorum longus muscle (EDL M) and soleus muscle, and on the myelinated fibers of the nerve to EDL M and other lower limb nerves were made on rats showing progressive weakness, intoxicated with acrylamide for 4 weeks (test), using silver staining. Terminal sproutings were significantly greater in frequencies in test compared with control in both muscles. In addition, morphologic changes in test consisted of a significant increase in the number of axon terminal branches and in the frequency of swellings of the preterminal, terminal, and ultraterminal axons and in an increase of myelinated fibers showing axonal degeneration in the nerve to EDL M. Such findings were in contrast with the previous report that cumulative doses of acrylamide inhibit sprouting of motor axons in endplates.