The loss of motorneurons corresponding to specific muscles in the wobbler mutant mouse.

The spinal motorneuronal pools specific to a peripheral muscular territory were studied in the wobbler mutant mouse, with the use of retrograde transport of horseradish peroxidase, which was injected into the musculo-cutaneous nerve and into the distal part of the sciatic nerve. Counts of labeled cells showed that the mean percentage of surviving motorneurons was 48.4% in the case of the musculo-cutaneous nerve and 83.6% in the case of the sciatic nerve. The cell loss was not found to be different in old compared to young mutants, suggesting that motorneuron degeneration is an early event in the course of the disease.