Figure 3

Increase in [Ca²]_i depends on extracellular Ca²⁺ influx following the application of cafedrine alone or theodrenaline alone. When experiments were performed in Ca²-free buffer, the maximum [Ca²]_i provoked by (A, B) 20:1 cafedrine/theodrenaline was comparable to the peak [Ca²]_i seen in Ca²⁺-containing buffer; however, peak [Ca²]_i observed after the application of (C, D) cafedrine alone and (E, F) theodrenaline alone was significantly reduced. When theodrenaline was applied, [Ca²]_i did not return to its baseline value during the whole observation period. Subsequent application of potassium chloride (200 mM) confirmed the vitality of the included cells (not shown). The control group is represented by the same 30 cells in each chart. FURA-2 340/380 ratio was normalized after a 100-s resting period, and each group consists of 30 cells from at least three different coverslips, ensuring independent measurements. Scale bar width represents 100 s. n = number of individual cells, ***p < 0.001, ns: not significant, Mann–Whitney U test, adjusted α-level = 0.013. ⊥ SEM, box and whisker plots indicate median, interquartile range (box), minimum and maximum (whiskers).