Fig. 1.

Time course of F-actin depolymerization and loss of synaptophysin (syn) clusters in 5-d-old cultured hippocampal neurons. Phalloidin labeling shows that latrunculin A depolymerizes most F-actin by 4 hr and essentially all of it by 8 hr (A, arrow at 0 hr indicates axon). After incubation in fresh medium overnight, F-actin levels are similar to those seen at 0 hr, but growth cones become particularly enriched (arrows in A, recovery). Synaptophysin labeling (B) over the same time course reveals a progressive loss of synaptic clusters along dendrites that is replaced by lightly labeled, small granules that extend through most processes (compare insets). After recovery, synaptophysin clusters are indistinguishable from those in control cultures. Scale bar, 20.2 μm; insets, 10.1 μm.