Figure 1.

Whole-brain mapping of efferent projections of PVN^MC4R+neurons. (A) Schematic showing unilateral viral injection into the PVN of MC4R-Cre⁺ mouse for anterograde tract-tracing (n = 4). (B) Representative image showing unilateral GFP expression in the PVN^MC4R+ neurons. Inset shows cell bodies of PVN^MC4R+ neurons expressing GFP. (C–W) Representative images showing the projections of PVN^MC4R+ neurons to different brain regions. (Y) Schematic depicting major PVN^MC4R+ axonal projections throughout the brain. Abbreviations: bed nucleus of the stria terminalis (BNST), lateral (LS), medial septum (MS), preoptic area (POA), dorsomedial hypothalamic nucleus (DMH), ventromedial hypothalamic nucleus (VMH), lateral hypothalamic area (LHA), arcuate hypothalamic nucleus (ARC), median eminence (ME), medial amygdaloid nucleus (MeA), lateral habenular nucleus (LHb), paraventricular nucleus of the thalamus (PVT), posterior hypothalamic nucleus (PH), premammillary nucleus (PMN), Supramammillary nucleus (SUM), nucleus of the posterior commissure (Pcom), precommissural nucleus (Prc), periaqueductal grey (PAG), ventral tegmental area (VTA), substantia nigra (SN), subbrachial nucleus (SubB), dorsal raphe nucleus (DRN), ventrolateral PAG (vlPAG), parabrachial nucleus (PBN), pre-locus coeruleus (pre-LC), medial PBN (MBP), Gigantocellular reticular nucleus (Gi), Rostral ventrolateral medulla (RVLM), nucleus of solitary tract (NTS), dorsal motor nucleus of the vagus (DMV), area postrema (AP), Caudal ventrolateral medulla (CVLM), and thoracic spinal cord (TSC), lateral ventricle (LV), anterior commissure, anterior part (aca), 3rd ventricle (3V), fornix (f), optic tract (opt), dorsal 3rd ventricle (D3V), (fr), mammillothalamic tract (mt), principal mammillary tract (pm), posterior commissure (pc), commissure of the superior colliculus (csc), aqueduct (Aq), 4th ventricle (4V), superior cerebellar peduncle (scp), perifacial zone (P7), ambiguus nucleus (Amb), central canal (CC). Scale bar: 200 μm for B–W, 50 μm for X.