Fig. 1.

Bafilomycin A₁ reduced the probability of synaptic transmitter release. A,B, Representative traces of evoked EPSCs in control cultures and after incubation with bafilomycin. In many cases, EPSCs were absent in bafilomycin-treated cultures. When present, the amplitude of EPSCs in bafilomycin was smaller than in control, and the number of synaptic failures was increased by bafilomycin. C, Averaged (n = 10) EPSCs in control and bafilomycin. Shown is the same pair of pre-postsynaptic neurons as in B. D,Mean evoked EPSC amplitude in control and bafilomycin-treated cultures (n = 25 and 35 presynaptic neurons, respectively).E, Mean percentage of synaptic failures observed during trials of 10 stimuli delivered at 1 Hz in control and after incubation with bafilomycin (n = 25 and 35 presynaptic neurons, respectively). F, mEPSCs in control and after incubation with bafilomycin. G, Mean frequency of mEPSCs measured during 1–4 min in control and in bafilomycin-treated cells (n = 9). H, Average cumulative probability plots of the mEPSC amplitude in control (n = 9) and after incubation with bafilomycin (n = 8). Cumulative probability plots were calculated in 1 pA bins and were not significantly different between control and bafilomycin-treated cells (Kolmogorov–Smirnov test). Holding potential was −60 mV. Significant differences with respect to control were established by the Student's t test atp < 0.02 (**) and p < 0.001 (***).