Smith‐Edwards, Kristen

Introduction: Inflammatory bowel disease is characterized by remitting and relapsing bouts of intestinal inflammation accompanied by sensory and motor dysfunction that persists beyond the active periods of inflammation. Evidence suggests that neural pathways of the Gut-Brain Axis, particularly the sensory and sympathetic nervous system, are involved in pathophysiology, but until recently technical restrictions have limited our understanding of the underlying neural circuit mechanisms. In this study, we examined how sensory-sympathetic circuits are modified by colitis and how these alterations contribute to dysfunction during both active inflammation and post-inflammatory recovery. Methods: E2a-GCaMP mice were treated with vehicle or 3% dextran sodium sulfate (DSS) for 5 days to induce experimental colitis and switched to normal drinking water. Mice were assessed at two time points: Day 7 (two days after ending DSS treatment), representing active inflammation, and Day 21 to represent recovery. Inflammation and mucosal damage were evaluated using disease activity index scores and hematoxylin and eosin (H&E) staining. Colon motility was assessed in vivo via colonic bead expulsion and ex vivo using whole-colon preparations. We performed Ca 2+ imaging of sympathetic motor neurons in prevertebral ganglia (PVG) and sensory neurons in dorsal root ganglia (DRG) neurons in ex vivo preparations that preserve extrinsic neural circuitry with the colon (intestinofugal-sympathetic and spinal cord-sympathetic pathways). Results: Histological analysis confirmed hallmark features of colitis, including colon shortening, immune infiltration, and mucosal damage at 7 days post-DSS (p< 0.05, n=3–4), which resolved after recovery. During active inflammation, in vivo colon transit time was significantly faster, and this persisted after recovery (p< 0.05, n=7-9). Ex vivo motility assays in isolated colons also revealed DSS-induced dysmotility during active inflammation, but the irregular colon motor complexes became normal after recovery (p< 0.05, n=7-9), suggesting that extrinsic neural pathways contribute to prolonged dysmotility. In preparations without the spinal cord, PVG neurons exhibited increased activity and increased responses to distension during active inflammation but returned to baseline after recovery (p< 0.05, n=3-4), suggesting alternative sensory-PVG pathways contribute to persistent dysmotility. In preparations with spinal circuits intact, thoracolumbar (TL), but not lumbosacral (LS), DRG sensory neurons were hypersensitive to colonic distension during inflammation (p< 0.05, n=8-9). Furthermore, TL spinal stimulation evoked more responses in PVG neurons during active inflammation, but this was associated with decreased inhibition of ENS motor circuits (p< 0.05, n=6-7) and increased Ca 2+ signaling in the epithelium (p< 0.05, n=5), suggesting shifts in TL spinal-sympathetic motor output. Preliminary studies show an increase in spontaneous activity of TL DRG neurons in recovery that does not occur at LS levels (p< 0.05, n=3-6), which suggests that thoracolumbar spinal pathways remain hyperexcitable after recovery.Conclusions: Our findings indicate that TL spinal pathways associated with sympathetic motor outflow contribute to pain and dysmotility during active inflammation and may contribute to the post-inflammatory recovery processes that seem to go awry in IBD patients with relapsing inflammation. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Background: As part of the bidirectional gut-brain communication system that influences gastrointestinal function, vagal pathways coordinate with the activity of interstitial cells of Cajal (ICC) to regulate gastric motility. Impairments in ICC slow wave activity and altered vagal tone have been implicated in diabetic gastroparesis and obesity, but technical limitations have restricted our ability to measure integrated and bidirectional activity in vagal-ICC pathways. Furthermore, the influence of physiological and meal-induced stimuli like gastric distension on these pathways is not well understood. We aimed to develop a calcium imaging approach in ex vivo nodose ganglion-vagus nerve-stomach preparations to investigate vagal-ICC pathways and test the effects of gastric distension on vagal activation, ICC network activity, and their functional interactions. Methods: Calcium imaging was performed in ex vivo preparations, in which the stomach and vagus nerves (with or without the ganglion) remain intact. EIIa-GCaMP6 (n=3) and cKit-GCaMP6 (n=3) mice were used to image Ca 2 + signals from both vagal neurons and ICC or ICC alone, respectively. Two-minute recordings were captured in the following stomach conditions: (1) Undistended; (2) Undistended + vagal nerve stimulation (VNS, 20 Hz, 1 s); (3) Distended (0.25 ml volume distension); (4) Distended + VNS. Ca 2 + signals in ICC and neurons, along with tissue displacement, were analyzed using Image J. Data from both GCaMP models were pooled for ICC. Results: Acute gastric distension significantly activated vagal sensory neurons in nodose ganglion compared to baseline (p=0.0193), and VNS evoked Ca 2 + responses in ICC and neurons, confirming intact nerve pathways. Both VNS and gastric distension altered the direction of ICC propagation, significantly increasing retrograde waves (p=0.0025 and p=0.0032, respectively), and VNS had no effect on retrograde waves in distended stomachs. VNS and distension also reduced length of propagation of anterograde ICC waves (p=0.019 and p=0.0004, respectively), and again, VNS effects were not observed during distension. VNS increased the velocity of ICC wave propagation, but only in undistended stomach (p=0.0283). Finally, VNS increased ICC pacemaker frequency regardless of the distension state (p=0.0123). Conclusion: Both acute gastric distension and VNS altered ICC network activity, with similar effects on network parameters. However, most of the VNS effects on ICC were blocked during distension. VNS increased the frequency of ICC network waves in both undistended and distended stomachs, suggesting that VNS can influence ICC pacemakers regardless of distension state. These findings have important implications for designing therapeutic strategies for gastroparesis. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.