Fig. 4. Inhibition of the electrical-field-evoked Ca²⁺ response by anion channel inhibitors. Multicellular prostate tumor spheroids were pretreated for 60 minutes with the anion channel inhibitors tamoxifen (50 µM) (B), niflumic acid (200 µM) (C), and NPPB (50 µM) (D). Under these experimental conditions the electrical-field-induced [Ca²⁺]_i response (A) was totally inhibited. Representative tracings recorded from single cells in multicellular tumor spheroids. The tumor spheroids were treated with electrical field during the time indicated by the horizontal solid bar.