Axonal labyrinths in the rat spinal cord: a consequence of degenerative atrophy

Transection, crush or local colchicine treatment of a peripheral nerve induces degenerative atrophy of central terminals of primary sensory neurons in the Rolando substance of the rat spinal cord. In addition to osmiophilic alterations that occur in the course of degenerative processes in general, degenerative atrophy is characterized by the appearance of spectacular labyrinthine formations. Electron-microscopic analysis reveals that these consist of flattened axonal profiles. Axonal labyrinths are interpreted as signs of futile regenerative efforts of axon terminals undergoining degenerative atrophy. Labyrinths disappear from the Rolando substance several months after peripheral nerve injury, when degenerative atrophy of the central terminal is replaced by regenerative proliferation.