RETARDATION OF FAST AXONAL-TRANSPORT IN WOBBLER MICE

To investigate axonal function in a model of early motor neuron diseas e, we examined fast and slow components of anterograde axonal transpor t in the less-affected hindlimb motor neurons of wobbler mice. To stud y the fast component (FC), we injected tritiated amino acids into the lumbar spinal cord and retrieved the sciatic nerve after 2 or 3 h. The transport distance was the extent of the plateau of labeling; regress ion analysis indicated that FC was 25% slower in wobbler mice than in unaffected littermates (P < 0.01). To study slow component (SC), [S-35 ] methionine was injected. Transport distances were to the peaks of la beling for structural proteins after 2 or 3 weeks. Rates for each subc omponent ( SCa and SCb) were unaffected by wobbler disease. Because th e rate of retrograde FC is also unaffected (Mitsumoto et al., Muscle & Nerve 13:121-126, 1990), we conclude that wobbler disease specificall y retards anterograde FC in less-affected hindlimb motor neurons, wher eas all components of axonal transport are retarded in forelimb motor neurons.