Photoinactivation of Dynamin results in the formation of large membrane inclusions. (A–H) FM 1-43 labeling in yw and shi^12-12B; shi-4C animals treated (+) or not treated (−) with FlAsH for 10 min and/or illumination for 2 min (±). All preparations were stimulated with KCl in the presence of FM 1-43 for 5 min. (I) Quantification of the number of FM 1-43–labeled membrane accumulations (accum.) per boutonic area in yw controls (n = 72 boutons from eight larvae) and in shi^12-12B; shi-4C after FALI (n = 72 boutons from 16 larvae). Error bars show SEMs; t test: ***, P < 0.0001. stim., stimulation. (J) Quantification of FM 1-43 labeling intensity (int.) after loading and unloading of yw controls (40 boutons from five larvae) and yw; shi-4C (n = 24 boutons from six larvae) after FALI normalized to the yw control (images shown in M–P). Error bars show SEMs. t test: ***, P < 0.0001. (K and L) FM 1-43 labeling (K) and quantification of the number of FM 1-43–labeled membrane accumulations per boutonic area (L) in yw (n = 32 boutons from five larvae) and shi^12-12B; shi-4C animals (n = 24 boutons from six larvae) after FALI when preparations were stimulated at 10 Hz for 5 min in the presence of FM 1-43. Error bars show SEMs. t test: ***, P < 0.0001. (M–P) Loading and unloading of FM 1-43 in yw and shi^12-12B; shi-4C after FALI. Preparations were loaded with FM 1-43 for 5 min in the presence of KCl (M and O, load) and unloaded using KCl stimulation for 10 min (N and P, unload; quantification in J). Bars, 5 µm.