Composite dose–response curves for E2 and STX illustrating the difference in potency between E2 and STX in arcuate POMC neurons. a, Experiments were conducted as described in Materials and Methods. Cells were perfused with different concentrations of E2 (0, 10, 50, 100, and 1000 nm) or STX (0, 1, 10, 50, and 100 nm). Data are presented as mean ± SEM (n = 4–11 cells/data point). Based on a logistics equation fit to the data points (see Materials and Methods), the EC50 for STX was 2.6 nm, which is 17-fold lower than that found for E2 (46.0 nm). The Hill slope for E2 and STX was 0.80 and 1.24, respectively. b, A, Biocytin–streptavidin–Cy2 labeling of a small pyramidal arcuate neuron that responded to STX. B, Immunocytochemical staining of β-endorphin in the same neuron (arrow). C, Overlay of A and B. Forty percent of the neurons (n = 49) were identified as POMC neurons. Scale bar: A–C, 20 μm. c, The chemical structures of 17-β-estradiol (E2) and the diphenylacrylamide STX.
