Figure 6.

Stx3pep, but not stx3con, blocks refilling of the RRP. (A) Upper panel shows the average capacitance responses to the first depolarization (ΔC_m1) evoked by each of four stimulus trains given one minute apart. Synaptic terminals were dialyzed with internal solution containing either stx3pep (solid bars) or stx3con (open bars). In a separate cohort of experiments, provided for comparison purposes, terminals were dialyzed with standard, peptide-free internal solution (shaded circles). Lower panel gives the amplitudes of the corresponding Ca²⁺ currents. (B) ΔC_m1 for trains 2–4 were normalized to the ΔC_m1 obtained from train 1. The normalized ΔC_m1 was plotted as a function of train number for each of the three treatment conditions: stx3pep (solid circles), stx3con (open circles) or peptide-free (shaded circles). For (A) and (B) stx3pep terminals: train, 1 n = 6; train 2, n = 5; trains 3–4, n = 3. For stx3con terminals, trains 1–2, n = 5; trains 3–4, n = 4. Peptide free terminals: trains 1, 2 n = 6, trains 3–4, n = 5.