Regenerating Axons Reclaim Sensory Targets from Collateral Nerve Sprouts

There is a critical period for the sprouting of intact low-threshold mechanosensory cutaneous nerves in rats; functional invasion of adjacent denervated skin does not occur in animals older than about 20 days of age, and it is largely confined to denervated skin within the ``domain'' of the parent dermatome. These nerves can regenerate readily in the adult, however, and such regenerating nerves do not respect domain borders; moreover, they functionally displace endings of intact nerves that earlier had sprouted into denervated skin.