Dopaminergic neurons in the substantia nigra compacta (SNc) of mice. (A): Dopaminergic (TH-ir) neurons were counted in the SNc one week after the last intraperitoneal injection of saline (i.e. controls; WT and AT1a-null males and WT ovx+E2 females) or MPTP in the different experimental groups. The dopaminergic neurons were quantified as the total number of TH-ir neurons in the SNc. Data are means ± SEM. *p < 0.05 relative to the corresponding saline-treated group (males or ovx+E2 females), #p < 0.05 relative to the group treated with MPTP alone (i.e. WT males+MPTP and WT ovx+MPTP). One-way ANOVA and Bonferroni post-hoc test. (B-G): representative photomicrographs of TH-ir neurons in non lesioned WT females with estrogen (ovx+E2; B), MPTP lesioned WT females with (C) and without (D) estrogen, as well as non-lesioned AT1a-null male mice (AT1a-/-; E), AT1a-null male mice lesioned with MPTP (F), and MPTP lesioned WT males (G). AT1-/-, AT1a-null mice; TH-ir, tyrosine hydroxylase immunoreactive; WT, wild type mice. Scale bar: 100 μm.