MLCK inhibitor peptide-18 (MLCKip) suppresses the post-tetanic changes in FRP and SRP sizes. (A and B) Presynaptic Ca²⁺ current (A, top), EPSCs (A, bottom) and cumulative quantal release (B). Three traces are superimposed in each panel: recordings at 40 s before (blue solid line) and at 40 s (red solid line) and 120 s (broken line) after HFS. (C–H) Bar graphs illustrate statistical mean of relative values at different time points normalized to the control value measured before HFS. Data from an individual synapse are superimposed on the bar graph (open circles, right ordinate). Error bar, SEM; n.s., not significant (P > 0.05, paired t test).