P2RX4 and amyotrophic lateral sclerosis: On the other hand, rats expressing mutated human superoxide dismutase (mSOD1G93A), an animal model for amyotrophic lateral sclerosis (ALS), showed a strong P2X4 immunoreactivity selectively associated with degenerating motoneurons in spinal cord and cerebral cortex as well as in Purkinje cells of the cerebellar cortex.