Remodeling of synaptic actin induced by photoconductive stimulation

Use-dependent synapse remodeling is thought to provide a cellular mechanism for encoding durable memories, yet whether activity triggers an actual str uctural change has remained controversial. We. use photoconductive stimulat ion to demonstrate activity dependent morphological synaptic plasticity by video imaging of GFP-actin at individual synapses. A single tetanus transie ntly moves presynaptic actin toward and postsynaptic actin away from the sy naptic junction. Repetitive spaced tetani induce glutamate receptor-depende nt stable restructuring of synapses. Presynaptic actin redistributes and fo rms new puncta that label for an active synapse marker FM5-95 within 2 hr. Postsynaptic actin sprouts projections toward the new presynaptic actin pun cta, resembling the axon-dendrite interaction during synaptogenesis. Our re sults indicate that activity-dependent presynaptic structural plasticity fa cilitates the formation of new active presynaptic terminals.