Sex differences in the regulation of mERα levels in adult hypothalamic astrocytes. Using surface biotinylation, hypothalamic astrocytes from female and male wild type mice have similar levels of baseline estrogen receptor-α (ERα) at the cell membrane (P > 0.05). Upon exposure to 1 nmol/l estradiol for 30 minutes, mERα levels significantly increased in the female astrocytes (P < 0.05 versus controls). However, estradiol did not regulate mERα concentration in the male astrocytes (P > 0.05 versus controls). *Significantly different compared with all other groups (P < 0.05, one-way ANOVA with Student-Newman-Keuls post hoc test).