A, Cultures were loaded with 10 μM FM1-43 using a train of 200 action potentials (10 Hz) at S1 and a train of 800 action potentials (80 Hz) at S2. In both cases, dyes were washed away immediately after stimulation and cultures were left to rest for 10 min. At both S1 and S2 the RRP was unloaded with a train of 60 action potentials (30 Hz) and the reserve pool (RP) was unloaded with three consecutive trains of 400 action potentials (40 Hz). Cells were left to rest for 20 min between S1 and S2. B, A representative trace of the average fluorescence drop of nerve terminals is shown (10 Hz load – S1; 80 Hz load – S2). Unloading stimulations are represented by bars. Traces were normalised (between 1 and 0) to the size of the S2 recycling pool (RRP + RP) for each nerve terminal. C, Proportion of the S1 and S2 RRP and RP as a percentage of their respective recycling pools is shown. D, Average proportion of the RRP and RP expressed as a percentage of the S1 SV recycling pool (RRP - solid bars; RP – dotted bars). All experiments n = 4 ± SEM, * p<0.05, ** p<0.01, *** p<0.001, for both RRP and RP, one-way ANOVA.