ACCELERATION OF MEMBRANE RECYCLING BY AXOTOMY OF CULTURED APLYSIA NEURONS

The rapid transition of a stationary axon into a motile growth cone re quires the recruitment of membrane and its strategic insertion into th e neurolemma. The source of membrane to support the initial rapid grow th postaxotomy is not known. Using membrane capacitance measurements, we examined quantitative aspects of membrane dynamics following axotom y of cultured Aplysia neurons. Axotomy activates two processes in para llel: membrane retrieval and exocytosis. Unexpectedly, membrane retrie val is the dominant process in the majority of the experiments. Thus, while a growth cone is vigorously extending, the total neuronal surfac e area decreases. We suggest that the initial rapid extension phase of the newly formed growth cone postaxotomy is supported by a pool of in tracellular membrane that is rapidly retrieved from the neurolemma.