AXON MEMBRANE FLOWS FROM THE GROWTH CONE TO THE CELL BODY

During the growth of axons, the surface area of the neuron increases d ramatically. Membrane addition as well as exchange could contribute to rapid membrane dynamics or flow. Using diffusing latex beads to monit or membrane flow, we find that axonal membrane flows rapidly (7 mu m/m in) from growth cone to cell body during axon growth and that flow is inhibited by brefeldin A. To power this flow, there is a membrane tens ion gradient from growth cone to cell body that could draw the membran e over the axon at that rate. Further, when an artificial flow is indu ced to the center of the axon by use of laser tweezers, the primary so urce of the membrane is from the growth cone. We suggest that during n euron growth, there is excess membrane added at the growth cone in chi ck dorsal root ganglia (DRGs) that undergoes endocytosis at the cell b ody, thereby creating a flow that can rapidly alter the content of the axon membrane.