Cell bodies of hypocretin/orexin- (blue dots) and MCH-containing (red dots) neurons are mainly localized in the perifornical-lateral hypothalamic area. These two groups of neurons intermingle but do not overlap. Reciprocal synaptic innervations between hypocretin/orexin and MCH neurons are reported as shown in the box. Synaptic contacts among hypocretin/orexin neurons (solid blue boutons on hypocretin/orexin neurons) and among MCH neurons (broken red boutons on MCH neurons) have been reported. Abbreviations: 3V, the third ventricle; PVN, periventricular nucleus; ARC, arcuate nucleus; DMH, dorsomedial hypothalamus; VMH, ventromedial hypothalamus; LH, lateral hypothalamus; f, fornix.