Mapping Axonal Connectivity Patterns Between The Spinal Cord and Nucleus Tractus Solitarius Using AAV2 Viral Tracing

Overview

The nucleus tractus solitarius (NTS) and the spinal cord are important sensory hubs that project interoceptive and somatosensory information to similar brain regions, respectively; however, the convergence of their projections is less established. The somatosensory pathway is far more established compared to the interoceptive pathway. Mapping these pathways could reveal functional mechanisms of the interoceptive pathway and whether complementary and unique NTS projections occur alongside the spinal cord. This will enhance understanding of how internal physiological states influence sensory information processing. We hypothesized that overlapping projection patterns indicated complementary region-specific behavioral roles in the NTS and interoceptive pathway. Three adult C57BL/6J mice received a stereotaxic injection in the NTS of AAV2-CAG-GFP and bilateral intraspinal injections of AAV2-CAG-tdTomato in the cervical and lumbar dorsal horn. Following a 2-3-week incubation period, transcardial perfusion was performed, brain and spinal cord tissue were coronally sectioned, and analyzed under a fluorescence microscope. Pixel light intensity measurements were collected for regions exhibiting converging pathways, including the parabrachial nucleus, periaqueductal gray, and periolivary region. The paraventricular hypothalamus was utilized as an anatomical control for labeling specificity.  Results show the NTS projects unique, state-dependent interoceptive information, supporting our hypothesis and highlighting how region-specific convergence shapes sensory processing and autonomic regulation. The results provide preliminary evidence of interoceptive pathways sharing parallel functional mechanisms with somatosensory pathways. This provides an integral framework relevant to producing therapeutic strategies targeted at integration nodes, leading to treating conditions which disrupt homeostasis, and potentially repurposing of drugs targeted towards somatosensation to treat visceral conditions.

Competition history

• CSEF 2026 Medicine & Physiology (Senior Division) · Entry S-15-26

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