Injections of the retrograde tracer cholera toxin b (CTb) into the ventral premammillary nucleus (PMV) of male and female rats. A, D Brightfield images of a reference brain stained with thionin showing two rostro-to-caudal levels of the PMV (A, rostral and D, caudal). B, C, E, F Brightfield images showing hypothalamic sections of a male (B, E, W282) and a female (C, F, W422) rat with CTb injections centered in the PMV. Abbreviations: 3V, third ventricle; Arc, arcuate nucleus; fx, fornix. Scale bar: A–F=500 μm.