Figure 9.

Elevation of basal [Ca²⁺]_i potentiates δ-cell exocytosis but not CICR. (A) Moderate elevation of [Ca²⁺]_i potentiates exocytosis but not CICR. Exocytosis (ΔC_m, lower) triggered by 500-ms depolarizations from −70 to 0 mV (V_m, top) in δ-cells infused with 103 nM or 240 nM free Ca²⁺ through patch pipettes. (B) Bar graph summarizing the effects of indicated number of independent experiments (n) from two or three animals for each condition. *, P < 0.05 vs. 103 nM [Ca²⁺]_i. (C) δ-cell [Ca²⁺]_i transients (lower, ΔF/F₀) triggered by 500-ms depolarizations (from −70 to 0 mV) before (pulse 1) and after (pulse 2) a 2-min depolarization from −70 to −40 mV (top). The average AUC of [Ca²⁺]_i transients triggered by pulses 1 and 2 of indicated number of independent experiments (n, from three animals) are summarized in D. Experiments in A and B were conducted using standard whole-cell technique. Data in B and D are presented as mean ± SEM of the numbers of independent experiments as indicated. Experiments in C and D were conducted using perforated patch clamp technique.