Development of the topographical projection of motor neurons to amphibian muscle accompanies motor neuron death.

The topographical projection of segmental nerves 8 and 9 to the glutaeus muscle of developing frogs was determined during the motor neuron death period (stages 54 to 59). Electrophysiological techniques showed that at stage 54 the entire glutaeus muscle received an innervation from both nerves 8 and 9. By stage 59 the muscle received an innervation from nerve 8 only on one side and by nerve 9 only on the opposite side. The emergence of this mature innervation pattern is accompanied by motor neuron death, with which it may be causally related.