Fig. 4.

Barium-sensitive inwardly rectifying K⁺ (IRK) current is activated by GTPγS dialysis of diestrous lactotrophs treated in vitro with E₂. A: internal dialysis of GTPγS (250 μM) does not activate IRK current in vehicle-treated, diestrous lactotrophs. B: diestrous cells treated overnight with E₂ (40 pg/ml) develop Ba²⁺-sensitive IRK during internal dialysis with GTPγS. C: summary of IRK currents recorded from diestrous lactotrophs dialyzed with GTPγS. E₂-treated lactotrophs have an increased IRK current over control diestrous lactotrophs. The effect of E₂ is blocked by coincubation with ICI-182,780 (ICI, 40 nM) or cycloheximide (Chx, 35 μM). Numbers in bars indicate number of lactotroph cells tested in each treatment group. Cells were derived from four independent preparations (4 rats). Treatment groups were compared using one-way ANOVA with Tukey's multiple-comparison post hoc test (***P < 0.001).