Figure 5.
A slowing of the release kinetics of FRP vesicles (ves) following low frequency stimulation. A, Presynaptic Ca2+ currents (ICa; middle) and EPSCs (bottom) elicited by a 20 Hz train of presynaptic depolarizations to +28 mV followed by a long depolarization (to +80 mV for 3 ms and to 0 mV for 50 ms; top). B, Presynaptic Ca2+ currents (top) and EPSCs (bottom) in response to a long depolarization that was preceded by a 20 Hz train (red traces) and to a control depolarization given in the naive state (black traces). Note that the predepressed EPSC rose more slowly than the control EPSC, as seen from the peak-scaled trace (red dashed trace; bottom). C, Transmitter release rates (inset) obtained from the deconvolution of the EPSCs shown in B and integrated release rates [cumulative (cum.) release]. Cumulative release traces were fitted with double exponential fits (data not shown). Traces in A–C are from the same recording. D, Average amplitude of the fast release component (Afast) following 20 Hz stimulation (red bar), normalized to the control response obtained in each pair (white bar; n = 5 cell pairs; p < 0.001). E, Average time constants (τfast) of the fast release component following 20 Hz trains (red bar) and under control conditions (black bar; n = 5 pairs).