Antagonism of calcineurin inhibits uptake of FM1–43 but not FM2–10. A, Cultures were loaded and unloaded with either FM2–10 or FM1–43 using the same protocol as in Figure 1A. Where indicated, cultures were preincubated with 10 μm CsA for 10 min before and during S2 loading. B, C, Cumulative histograms of the effect of CsA on either FM2–10 (B) or FM1–43 (C) loading in individual nerve terminals (ΔS2/ΔS1, n = 233, FM2–10 control; n = 180, FM2–10 CsA; n = 258, FM1–43 control; n = 168, FM1–43 CsA). D, Cultures were loaded and unloaded with either FM2–10 or FM1–43 using the same protocol as in Figure 1A. Where indicated, cultures were preincubated with 10 μm CsA for 10 min before and during S2 unloading. E, F, Cumulative histograms of the effect of CsA on either FM2–10 (E) or FM1–43 (F) unloading in individual nerve terminals (ΔS2/ΔS1, n = 270, FM2–10 CsA; n = 270, FM1–43 CsA). Open symbols, FM2–10; closed symbols, FM1–43; gray symbols, CsA. For all experiments, n = 3.