Figure 1.

A stimulus train applied to a single synaptic terminal demonstrates that stimulus-evoked exocytosis can continue for seconds. (A) A high-resolution capacitance recording from an isolated bipolar cell synaptic terminal demonstrates that exocytosis is evoked throughout an ∼10 s stimulus train. The stimulus train was comprised of 136 and 20-ms depolarizing voltage steps (−60 to 0 mV) with an interpulse interval of 50 ms. The shaded bar indicates the timing of the stimulus train. (B) A representative family of Ca²⁺ current (I_Ca), capacitance (C_m), series conductance (G_s) and membrane conductance (G_m) traces evoked by the first voltage step in the stimulus train is shown on an expanded timescale. Same terminal as in (A). Gaps in the C_m, G_s, and G_m traces correspond to the 20-ms period when Ca²⁺ channels were conducting, and thus, measurement of these parameters is unreliable (37, 44). There were no correlated changes C_m, G_s, and G_m.