The neuron is remarkable as a cell with a prolonged process, the axon. Various substances and organelles are transported up and down the axon. Axotomy profoundly affects this axonal transport. The proximal stump of the axon seals off and organelles accumulate. Terminal sprouts appear and move towards the distal stump. Soon after reinnervation neurotransmission reappears. Initially polyneuronal innervation occurs but this is then eliminated. Somatopetal axonal transport has been studied using tracer macromolecules in the mouse facial neuron model. Transport was blocked by axotomy from terminals in muscle but persisted at the injured axonal membrane. This stopped when the axonal membrane grew over the stump. Transport returned after reinnervation. Such transport may carry the signals that govern neuronal response to axotomy.