Fig. 4.

Progesterone abbreviated action potential duration (APD) with no effect on resting membrane potential (RMP) in ventricular myocytes from female mice. A: representative action potentials recorded in under control conditions and in the presence of 1 µM progesterone. B and C: mean data show that, while progesterone had no effect on APD at 50% (APD₅₀), it abbreviated APD₉₀. D: application of 1 µM progesterone had no effect on RMP. Values represent means ± SE; n = 10 control myocytes (9 mice) and 9 myocytes in the presence of 1 µM progesterone (4 mice) (*P < 0.05, t-test).