The effects of MLCK inhibitors on the baseline synaptic transmission. (A, a and b) Representative EPSCs evoked by a paired pulse stimulation (ISI, 20 ms) of afferent fibers at 0.1 Hz in the presence of 1 mM kynurenate. EPSCs recorded under control conditions (black) and in the presence of ML-9 (20 µM, A, a, red) or ML-7 (20 µM, A, b, blue) are superimposed. (A, c) Percentage change in baseline amplitude of EPSC on application of ML-9 (n = 4) or ML7 (n = 5). (B, a, and C, a) Train of EPSCs (30 pulses at 100 Hz) under control conditions (black) and after bath application of ML9 (B, a, red) or ML-7 (C, a, blue) are superimposed. Inset, enlarged last six EPSCs. Summary graph for the peak amplitude of first EPSC (B, b, and C, b) and for the mean peak amplitude of last 6 EPSCs (B, c, and C, c) under control conditions (ctrl) and in the presence of ML-9 (B) or ML-7 (C). (D, a) EPSCs were evoked by presynaptic step depolarization to 0 mV for 50 ms duration preceded by +70 mV for 2-ms predepolarizing pulse using presynaptic patch pipette containing CaM only (3 µM, black), CaM plus wortmannin (5 µM, red), or CaM plus ML7 (20 µM, blue). EPSCs obtained from different synapses under each intracellular condition were averaged, and the averaged traces are superimposed with error bars (light colored). (D, b and c) Summary graphs for mean sizes of FRP (D, b) and SRP (D, c) estimated from deconvolution analysis of EPSCs evoked by a 50-ms depolarizing pulse with CaM only (CaM), CaM plus wortmannin (WMN), or CaM plus ML-7 (ML7) included in the presynaptic pipette. (D, d) Presynaptic calcium currents (top) and concomitant EPSCs (bottom) evoked by presynaptic depolarization to 0 mV for 1, 2, and 3 ms in duration. Traces under control conditions (black) and those recorded at 5 min after bath application of 5 µM wortmannin are superimposed (red). Presynaptic patch pipette contained 3 µM CaM.