Effects of staurosporine on exocytosis and endocytosis at frog motor nerveterminals

Observations of the dynamic staining and destaining of FM1-43 in frog motor nerve terminals (Henkel and Betz, 1995) suggested that staurosporine might shorten the interval between exocytosis and endocytosis, inducing a "kiss and run" mode of exocytosis and endocytosis. We tested this hypothesis by u sing FM1-43 imaging (to measure the time course of FM1-43 endocytosis), int racellular recording of evoked synaptic potentials (to measure acetylcholin e release), and electron microscopy (to examine synaptic vesicle distributi on). Staurosporine reduced FM1-43 uptake during but not after a tetanus, in creased the speed of end plate potential (EPP) amplitude rundown, and great ly slowed the recovery from synaptic depression. Ultrastructural observatio ns showed pronounced vesicle depletion near active zones after tetanic stim ulation in staurosporine-treated preparations. These results suggest that s taurosporine acted primarily to impair mobilization of synaptic vesicles du ring tetanic stimulation.