Figure 1. ATP‐dependent and ATP‐independent mechanisms co‐exist at the calyx of Held terminals.

A, sampled Ca²⁺ channel current from a control calyx (ICa, Aa) and membrane capacitance responses (Cm, Ab) following depol_20ms under dialysis with the control pipette solution (Ctrl), 4 mm ATPγS or 4 mm AMP‐PNP, respectively. Bath Ca²⁺ was 2 mm. B, summary of charge of ICa (QCa), exocytosis (ΔCm), initial rate of endocytosis (Rate_endo) and membrane retrieved at 25 s (Endo_25s) induced by depol_20ms for control (n = 7), ATPγS (n = 7) and AMP‐PNP (n = 6). Colour code for treatments also applies to (D) and (F). C and D, sampled ICa from a control calyx (Ca) and Cm responses (Cb) induced by depol_20msX10 at calyces bathed in 2 mm Ca²⁺. Summarized data are from calyces dialysed with control pipette solution (n = 7), ATPγS (n = 7) and AMP‐PNP (n = 5), respectively. E and F, sampled ICa from a control calyx (Ea) and Cm responses (Eb) induced by depol_50msX10 at calyces bathed in 6 mm Ca²⁺. Summarized data are from control (n = 8), ATPγS (n = 9) and AMP‐PNP (n = 9), respectively.