E₂ and STX rapidly attenuated the baclofen response in hypothalamic arcuate (POMC) neurons in wild-type and ERαKO, ERβKO and ERαβKO mice. a, Experiments were conducted as described in the Materials and Methods. Four representative traces of the baclofen response in the presence of vehicle, E₂ (100 nm), or STX (100 nm) in arcuate neurons from wild-type (A, B) and ERαKO (C, D) mice are shown. b, Bar graphs summarizing the effects of E₂ or STX in arcuate (POMC) neurons from ovariectomized, wild-type, ERαKO, and ERβKO mice. E₂ and STX (100 nm) rapidly attenuated the outward (GIRK) current induced by the GABA_B receptor agonist baclofen in arcuate (POMC) neurons from ovariectomized wild-type (C57BL/6), ERαKO, and ERβKO mice. Bars represent the mean ± SEM. ^###p < 0.001, E₂-treated wild-type group versus vehicle (Veh) wild-type control; ***p < 0.001, E₂- or STX-treated ERαKO or ERβKO groups versus vehicle ERKO control. The data for the ERαKO and ERβKO control responses were combined in one bar graph. c, Double labeling of POMC neurons that responded to STX from ERαKO (A–C) and ERβKO (D–F) mice. Arcuate neurons were filled with biocytin during the whole-cell recording. A, D, Biocytin–streptavidin–Cy2 labeling of two small pyramidal arcuate neurons. B, E, Immunocytochemical staining of β-endorphin in the same neurons (arrow). C, overlay of A and B; F, overlay of D and E. Nineteen of the 46 responsive neurons (41%) were identified as β-endorphin neurons. Scale bar: A–F, 20 μm. d, Bar graphs summarizing the effects of E₂, STX, or ICI 182,780 in arcuate (POMC) neurons from male ERαβKO mice. E₂ and STX (100 nm) rapidly attenuated the outward (GIRK) current induced by the GABA_B receptor agonist baclofen, which was antagonized by ICI. ICI alone had no effect. Twelve of the 20 (60%) neurons were identified as POMC neurons. Bars represent the mean ± SEM. ^†††p < 0.001, E₂- or STX- versus vehicle-treated cells from ERαβKO mice.