Relationship between muscle size and motoneurone survival in temporarily paralyzed embryos.

Neuronal cell death has been postulated to occur as a consequence of there being a limited availability of target. This hypothesis was examined by delaying the onset of motoneurone cell death, by temporary paralysis of chick embryos, until the size of the target had increased. Despite the availability of this enlarged periphery, the extent of cell death was unaltered, although the rate of cell death was retarded. It is argued that the extent of cell death is not simply related to target size and may instead be governed by differences in the capacity of particular motoneurones to compete successfully for target cells.