Elimination of [Ca²⁺]_i elevations cancels potentiation of UTP- and trypsin-evoked exocytosis. All cells were preincubated with 5 μM thapsigargin in Ca²⁺-free solution (0 Ca²⁺) for at least 10 min to deplete intracellular Ca²⁺ stores. All experiments were performed in Ca²⁺-free solution. Representative [Ca²⁺]_i recording (A) and average normalized rate of exocytosis (B; n = 7) evoked by 1 μM FSK plus 2 μM UTP in cells. Representative trace of [Ca²⁺]_i (C) and the average normalized rate of exocytosis (D; n = 10) evoked by 1 μM FSK plus 100 nM trypsin after depletion of Ca²⁺ stores by using thapsigargin. In B and D, red dotted lines taken from Fig. 3 (B and D) show the exocytotic responses to UTP or trypsin without the thapsigargin treatment.