NEURON VOLUME IN THE VENTRAL HORN IN WOBBLER MOUSE MOTONEURON DISEASE- A LIGHT-MICROSCOPE STEREOLOGICAL STUDY

Previous pathological reports have indicated that swollen and vacuolat ed motoneuron cell bodies are the most predominant feature characteris ing Wobbler mouse motoneuron disease, but there has been little suppor tive evidence using area measurements. The present study focuses on th e possible role of changes in neuronal nuclear and perikaryal volumes in the cervical spinal cord ventral horn, using new and traditional st ereological probes which provide unbiased estimates of volume. Semithi n sections from the Ventral horn of Wobbler mice and age and sex-match ed phenotypically normal littermates were examined at 2 ages (young an d old). The young Wobbler group had significantly larger volume weight ed mean perikaryal volumes compared with age-matched controls, reflect ing the presence of large swollen cells characteristic of this group; this situation was reversed in the control group. Number-weighted peri karyal volume estimates in the old Wobbler group were smaller than in age-matched controls. The variation in perikaryal volume was greatest in the young Wobbler group in which the coefficient of variation was 1 27 %. The mean number weighted and volume weighted mean nuclear volume s were significantly smaller in the old Wobbler group compared with ag e-matched controls and young Wobbler groups. The application of new st ereological probes has enabled us to document more precisely these cha nges in neuronal structure in the Wobbler mutant mouse.