Figure 2.

Effects of mitochondrial NCE inhibitor, TPP⁺, on PTP and presynaptic residual calcium (Ca_res) at the calyx of Held synapse. A, Time-dependent changes in EPSC amplitude (open circles, left ordinate) and in presynaptic Ca_res (gray dots; calibration: 200 nm) simultaneously recorded at the same synapse (aCSF + γ-DGG). TPP⁺ reduced the time integrals of Ca_res from 3.89 to 0.46 μm · s. B, Ca²⁺ transients during TS with expanded time scale (black, control; gray, TPP⁺). C, D, Mean values for peak [Ca²⁺] of Ca²⁺ transients (C) and time integral of Ca_res (D) induced by TS before and after bath application of TPP⁺. The estimate for ∫Ca_resdt was reduced from 2.03 ± 0.50 to 0.37 ± 0.07 μm · s (n = 5; p = 0.03), whereas the mean peak [Ca²⁺] was little affected (2.77 ± 0.63 μm and 2.75 ± 0.64 μm before and after application of TPP⁺, respectively; n = 5; p = 0.90). E, TPP⁺-sensitive PTP (solid line) and Ca_res (gray dots), calculated from A, decayed with a similar time course (dotted line, an exponential fit to TPP⁺-sensitive PTP with τ = 39.54 s; τ for Ca_res = 35.78 s). F, Mean values for decay time constants (τ) of TPP⁺-sensitive PTP (τ = 23.66 ± 4.34 s; n = 5) and residual Δ[Ca²⁺]_i (τ = 24.61 ± 4.56 s; n = 5). On the bar graphs (C, D, and F), data points measured from the same synapse are connected with a dotted line.