Abstract

Recent electrophysiological studies of human and mouse muscular dystrophy have prompted the hypothesis that both are of neurogenic rather than myogenic origin. A decreased number of spinal motor neurones might be expected if this hypothesis were correct. The total number of neurones in the anterior grey horns of seven normal mice, six Bar Harbor 129 strain dystrophic mice, and six mice suffering from genetically-determined spinal muscular atrophy have been counted. The number of neurones in the cell types believed to include the motor neurones was significantly reduced to 13 to 71% of normal in mice with spinal muscular atrophy. In mice with muscular dystrophy, the number of anterior horn neurones was higher rather than lower than normal. The significance of these findings is discussed.