NEUROPEPTIDE ARCHITECTURE OF THE DORSAL RAPHE NUCLEUS AND ITS MODULATION BY HIGH-FAT DIET

The dorsal raphe nucleus (DR) is a central midbrain hub integrating homeostatic and affective signals, with widespread projections regulating sleep, energy balance, mood, and motivation. The DR contains the majority of forebrain-projecting serotonin (5-HT) cells, which are molecularly and functionally heterogeneous. These neurons co-express glutamatergic and GABAergic markers and engage distinct downstream circuits.
Beyond classical neurotransmitters, the DR expresses a diverse repertoire of neuropeptides and receptors implicated in energy balance, including Neuropeptide Y, Somatostatin, Cholecystokinin, Galanin, and the Melanocortin-4 receptor. However, the spatial organization of these signalling systems and their cell-type-specific expression within the DR remain understudied. To address this, we employed Xenium, an imaging-based spatial transcriptomics platform enabling highly multiplexed, single-cell RNA detection while preserving tissue architecture. Applied to the mouse DR, Xenium enabled simultaneous mapping of neurotransmitter markers, neuropeptides, and receptor transcripts, revealing molecularly defined cell populations and their spatial relationships across DR subdomains. This approach provides a spatially resolved framework for understanding neuropeptide organization in the DR.
Building on this baseline, we examined the effects of chronic high-fat diet (HFD) in mice, a widely used model of Western-style diets that promote obesity and metabolic dysfunction and are associated with altered feeding and affective behaviour. Using Xenium, we find that HFD induces cell-type-specific alterations in neuropeptide and neurotransmitter gene expression within discrete DR populations, suggesting that diet is associated with remodelling of local DR networks.