Figure 1
From: A Three-Pool Model Dissecting Readily Releasable Pool Replenishment at the Calyx of Held
More intense stimulation slows the RRP replenishment.
(A) Left: Sampled presynaptic calcium current (ICa, upper) and membrane capacitance (Cm, lower) induced by a 20 ms depolarisation followed by a conditioning pulse of 20 ms depolarization with a 0.5 s interval. Right: Similar to Left, except that the stimulus interval is 20 s. (B) Upper: The protocol used to measure the RRP replenishment after a 20 ms depolarisation pulse. Lower: Cm induced by a 20 ms depolarisation applied at various intervals after the conditioning stimulus (n = 8). Data were normalised to the Cm induced by the conditioning pulse and fit with a bi-exponential function (solid line) where A1 = 0.71, τ1 = 0.26 s, A2 = 0.29, τ2 = 9.5 s. (C) Similar to A, except that the conditioning stimulus was 10 pulses of 20 ms depolarisation at 10 Hz. (D) Similar to B, except that the conditioning stimulus was 10 pulses of 20 ms depolarisation at 10 Hz (n = 11). Data were normalised to the Cm induced by a 20 ms depolarisation applied at >30 s after the conditioning stimulus and fit with a bi-exponential function (solid line) where A1 = 0.33, τ1 = 0.38 s, A2 = 0.67, τ2 = 7.8 s. The fitting curve of single pulse was also plotted for comparison (dotted line). (E) Similar to A, except that the conditioning stimulus was 10 pulses of 20 ms depolarisation at 1 Hz. (F) Similar to D, except that the conditioning stimulus was 10 pulses of 20 ms depolarisation at 1 Hz (n = 6). Data were fit with a bi-exponential function where A1 = 0.29, τ1 = 0.25 s, A2 = 0.71, τ2 = 7.9 s. (G) The plot of the normalised RRP replenishmentrapid amplitude versus calcium influx (QICa) in a 20 ms depolarisation pulse and 10 pulses of 20 ms depolarisation at 1–10 Hz (QICa: 38.9 ± 2.6 pC, n = 8, single pulse; 312 ± 34 pC, n = 11, 10 pulses at 10 Hz; 323 ± 15 pC, n = 6, 10 pulses at 1 Hz).
