Figure 1. Effects of chlorpromazine on the increases in intracellular Calcium²+ concentration ([Calcium²+]ⁱ) and force induced by 80 mM Potassium sup + -depolarization. (A) Representative recordings showing changes in the fluorescence and force development induced by 80 mM Potassium sup + -depolarization. The first and second traces from the top show changes in the 500-nm fluorescence intensities obtained at 340 nm (F³⁴⁰) and 380 nm (F³⁸⁰) excitations, respectively. The third trace shows changes in the fluorescence ratio of F³⁴⁰to F sub 380. The lowest trace shows the force development. (B and C) Effects of various concentrations of chlorpromazine on changes in [Calcium²+]ⁱ(B) and force development (C) induced by 80 mM Potassium sup + -depolarization. The strips were pretreated with 0 M (open circle; control), 10 nM (closed circle), 100 nM (closed triangle), and 1 micro Meter (closed square) chlorpromazine. Chlorpromazine was applied for 10 min before and was present during 80 mM Potassium sup + -depolarization. The abscissa scales in (B) and (C) show the time (in min) after the application of 80 mM Potassium sup + -physiologic saline solution. The mean values with SE bars are shown (n = 3-5). The number of experiments refers to the number of strips from each different animal.