1. The adipose tissue-derived hormone leptin reduces food intake and bodyweight via leptin receptors (Ob-R) in the hypothalamus.

2. Leptin receptor immunoreactivity, demonstrated with an antiserum recognizing all Ob-R isoforms, is present in hypothalamic neurons of the medial and lateral preoptic area, organum vasculosum lamina terminalis, subfornical organ, periventricular, suprachiasmatic, supraoptic (SON), paraventricular (PVN), arcuate (ARC), dorsomedial, ventromedial hypothalamic and tuberomammillary nuclei and lateral hypothalamic area. In the brainstem, Ob-R immunoreactivity is present in the area postrema, nucleus tractus solitarius, hypoglossal nucleus and dorsal motor nucleus of the vagus nerve.

3. Leptin receptor immunoreactivity is present in magnocellular vasopressin and oxytocin neurons of the SON and PVN, in parvocellular corticotropin-releasing hormone neurons of the PVN, neuropeptide Y and pro-opiomelanocortin neurons of the ARC and in melanin-concentrating hormone neurons of the lateral hypothalamic area.

4. The passage of leptin across the blood–brain barrier and the chemical mediators of the action of leptin in the hypothalamus are discussed.