Parallel Labeled-Line Organization of Sympathetic Outflow for Selective Organ Regulation in Mice

The sympathetic nervous system is vital in maintaining homeostasis and responding to environmental changes ^1–3 . This regulation is coordinated by the spinal sympathetic preganglionic neurons (SPNs), which influence various organs both through neuronal pathways via postganglionic neurons and through endocrine processes by innervating the adrenal gland. Despite decades of research supporting the concept of selective control within this system ^1,4–9 , the neural circuit organization responsible for the specificity of sympathetic outflow remains poorly understood. Notably, classical anatomical studies in rats have not revealed a definitive molecular code governing SPNs, nor have they confirmed the existence of SPNs strictly corresponding to specific output targets ^1,6,10,11 . To reconcile this discrepancy, we aim to integrate recent transcriptome data of SPNs ^12,13 in mice with viral-genetic toolkits ¹⁴ to map axonal projections and manipulate the functions of SPNs governing the gastrointestinal tract and adrenal gland. Here, we have identified two subtypes of SPNs in the lower thoracic spinal cord, defined at the molecular level, exhibiting non-overlapping patterns of innervation. Chemogenetic manipulations on these distinct SPN subtypes revealed selective impacts on the digestive functions in the gastrointestinal tracts or glucose metabolism mediated by the adrenal gland, respectively. This molecularly delineated parallel labeled-line organization in sympathetic outflows presents a potential avenue for selectively manipulating organ functions.