Effect of peripheral deprivation on mammalian motoneurone development.

Foetal rat hindlimbs were removed at 18 days gestation to determine the effect of target tissue removal on the development of mammalian motoneurones. At 25 days postnatal there was a large reduction in the numbers of motoneurones with a corresponding drop in the activity of choline acetyltransferase as well as in the total protein content on the ipsilateral side of the spinal cord. These results show that in mammals, as in other vertebrates, the size of a neuronal population is regulated by the size of the peripheral field innervated.