Fig. 4.

Rundown of synaptic responses in the presence of dynasore. (A) Example of responses of sypH-expressing synapses to repeated stimulation (20 APs at 20 Hz) delivered every minute. In control conditions (DMSO), responses remain stable. But responses diminish with repeated stimulation in the presence of dynasore. Note the lack of endocytosis in the presence of dynasore. Each set of traces is an average of 20 synapses from one experiment. Numbers on top refer to the trial number. (B) Average responses normalized to the first response clearly shows the decay of responses in the presence of dynasore. DMSO data were fitted with a straight line and dynasore data with a single exponential (n = 2 and 3 experiments, 40 and 60 boutons, respectively, for DMSO and dynasore). (C) Integrated response over the 10 trials reaches an asymptotic value of ≈4 (normalized to the first response) for dynasore-treated synapses. The addition of NH₄Cl after the 10th trial reveals an additional pool of vesicles that is similar in size to the total released vesicles.