Fig. 6.

Effects on α₁-AR stimulation on Ca²⁺ handling as assessed with caffeine-induced contractures. A: records of caffeine-induced Ca²⁺ transients in LV cells before the addition of PE and 10 min after PE induced either a NIE or a PIE. B: summary of caffeine-induced Ca²⁺ transients before (Con) and after α₁-AR stimulation induced a NIE or PIE in RV or LV cells. C: summary of the time course of decline of the caffeine-induced Ca²⁺ transient as assessed from the relaxation half-time (RT₅₀; same groups as in B). RV and LV myocyte numbers were 17 and 14 for Con, 8 and 8 for NIE, and 9 and 7 for PIE, respectively. *P < 0.05; ***P < 0.001.