PROJECT SUMMARY/ABSTRACT Lung is one of the largest internal sensory organs. Chronic exposure of the lung to allergens or other irritants has been shown to influence stress, anxiety, depression, and dementia. On the other hand, practices that modulate respiration including deep breathing in meditation or Qi Gong are linked to improved central nervous system (CNS) health. However, the functional neuroanatomical connections between brain and lung at the molecular and cellular level remain largely unknown. This R01 application proposes to test the hypothesis, using mouse models, that allergen-induced signals detected by interoceptors in the lung are transmitted via vagal afferent neurons to nucleus tractus solitarius (NTS) (aim 1), and then from NTS to other central integrators in the brain, potentially including paraventricular nucleus (PVH) in the hypothalamus (aim 2), and lastly from dorsal motor nucleus of the vagus (DMV) to descending spinal cord efferents that project back to the lung (aim 3) to sense and regulate airway hyperresponsiveness. The aims will incorporate cutting-edge cell-type specific circuit and viral tracing techniques, lightsheet 3-D imaging, and candidate multiplex RNA in situ and unbiased snRNAseq approaches to map the neural circuits and identify the signature of signal-activated neurons in peripheral ganglia, NTS and other brain regions. In addition, they will combine chemogenetic, optogenetic and toxin-based approaches with neural activity readouts including cFOS, in vivo calcium imaging, electrophysiology, and lung physiology to assess gain and loss of functional effects of key lung, vagal, spinal and brain connections.