Figure 5.

Stx3pep blocks the fusion of NR vesicles while preserving the ability of the initial the RRP and RP to fuse. (A) The capacitance records compare the mean cumulative rise in membrane capacitance over time in response to the stimulus train for stx3pep terminals (solid circles) and stx3con terminals (open circles). For ease of representation, error bars are displayed for every fifth data point. The difference trace (stx3con–stx3pep), representing the stx3pep-sensitive component of release, is shown in red. (B) Bar graphs compare the average magnitude of the capacitance response (upper panel) and Ca²⁺ current (lower panel) evoked by the first 20-ms depolarization (−60 to 0 mV) under peptide-free conditions (gray bars, n = 12), in the presence of stx3con (open bars, n = 13) or in the presence of stx3pep (black bars, n = 13). Shown in blue are the corresponding responses in stx3pep terminals when the first stimulus was given 3 min into the recording (n = 9). (C) Bar graphs compare the average magnitude of the total capacitance response (upper panel) and Ca²⁺ current (lower panel) under peptide-free conditions (gray bars, n = 6), in the presence of stx3con (open bars, n = 5) or in the presence of stx3pep (black bars, n = 6). Shown in blue are the corresponding responses in stx3pep terminals in which the stimulus train delayed until 3 min into the recording (n = 9).