Time course of loss of 4-AP responsiveness and Kv4.3 expression in pregnant mouse myometrium. Myometrial samples were obtained from nonpregnant (NP, n = 5), 7 days pregnant (P7, n = 3), 10 days pregnant (P10, n = 3), 15 days pregnant (P15, n = 4) and term-pregnant (P20, n = 5) mice. Panel A: Results from non-cumulative concentration-response experiments are presented as mean percentages of the maximal response to 4-AP in NP tissues. Panel B: Densitometry of Kv4.3 expression in the same samples evaluated in panel (A) and typical Western blot results demonstrating expression of Kv4.3 as well as Kv1.4 and γ-actin to confirm equal protein loading. Band densities are expressed in graph as a percentage of the maximal band density on each film; asterisks denote a significant difference (P = 0.01) between average NP and term-pregnant sample band densities.