Distribution of retrogradely labeled neurons in the male and female hippocampus and hypothalamus. A, D, G Brightfield images of a reference brain stained with thionin showing the cytoarchitecture of a control (female) brain. B and C Brightfield images showing cholera toxin b immunoreactive neurons (CTb-ir) in the ventral subiculum (Sv) of male (B) and female (C) rats. E and F Brightfield images showing CTb-ir neurons in the medial preoptic nucleus (MPN) of male (E) and female (F) rats. H and G Brightfield images showing CTb-ir neurons in the ventrolateral subdivision of the ventromedial nucleus of the hypothalamus (VMHvl), lateral hypothalamic area (LHA) and arcuate nucleus (Arc) of male (H) and female (I) rats. Abbreviations: 3V, third ventricle; BSTpr, bed nucleus of the stria terminalis, principal subdivision; DG, dentate gyrus; fx, fornix; LPO, lateral preoptic area; Or, stratus oriens; Pe, periventricular nucleus. Scale bar: A–B, D–I=300 μm; C=150 μm.