Fig. 5.

Differential effect of CPA on depleting IP₃-sensitive versus caffeine-sensitive Ca²⁺ stores. (A) Averaged Ca²⁺ responses ± s.e. (n = 6) of chromaffin cells to carbachol (500 μM) delivered to the cells via a pressure ejection pipette (arrow). Error bars not shown are within the thickness of the line. (B) Averaged fluorescence traces ± s.e. (n = 24) showing the lack of a Ca²⁺ response to carbachol (arrow) in the presence of CPA (gray bar). Error bars not shown are within the thickness of the line. (C) Representative trace of Ca²⁺ released from the ER in CPA-treated cells (upper solid line) in response to caffeine (50 mM) applied by perfusion (lower solid line). In both B and C, cells were pretreated with 30 μM CPA for 15 min prior to the experiment, which was carried out in the continued presence of CPA. (D) Representative traces of Ca²⁺ released from the ER in non-CPA-treated cells in response to caffeine (50 mM) applied by perfusion (solid line).