Currents were evoked in non-pregnant (NPM; A) and pregnant (PM; B) rat uterine myocytes by applying a 200 ms depolarizing pulse every 10 s from -60 to +80 mV. Recordings were started immediately after membrane disruption. A and B, time course of Iout with either 10 μM isoprenaline (Iso) in the bath, 10 μM isoprenaline in the bath and 1 μM transducin-βγ (TDβγ+ Iso) in the patch-pipette, or TDβγ in the pipette but no agonist in the bath (TDβγ). Mean values from three different groups are shown in both A and B. Numbers in parentheses denote the number of cells. NPM cells were obtained from five (▵), six (^) and seven rats (□), PM cells from five (▵), six (^) and five rats (□). Current densities were used to calculate the percentage values. **P < 0.01; ***P < 0.001 versus Iso alone.