Morales‐Soto, Wilmarie

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.

The gastrointestinal tract is made up of specialized organs that work in tandem to facilitate digestion. The colon regulates the final steps in this process where complex motor patterns in proximal regions facilitate the formation of fecal pellets that are propelled along the distal colon via self-sustaining neural peristalsis and temporarily stored before defecation. Historically, our understanding of colonic motility has focused primarily on distal regions, and the intrinsic reflex circuits of the enteric nervous system involved in neural peristalsis have been defined, but we do not yet have a clear grasp on the mechanisms orchestrating motor function in proximal regions. New approaches have brought to the forefront the unique structural, neurochemical, and functional characteristics that exist in distinct regions of the mouse and human colon. In this mini-review, we highlight key differences along the proximal-distal colonic axis and discuss how these differences relate to region-specific motor function.

This study challenges prevailing views on neural innervation in perivascular adipose tissue (PVAT) and its role in adrenergic-driven anticontractile effects on vasculature. Contrary to existing paradigms, limited anatomical and functional connections were found between PVAT nerve fibers and adipocytes, underscoring the importance of exploring alternative mechanistic pathways. Understanding the mechanisms involved in PVAT’s anticontractile effects is critical for developing potential therapeutic interventions against dysregulated vascular tone, hypertension, and cardiovascular disease.

Perivascular adipose tissue (PVAT) has emerged as a regulator of blood pressure by releasing anticontractile factors, which may be disrupted in disease. The production of adipocyte anticontractile factors is driven by norepinephrine (NE), a sympathetic neurotransmitter; however, the source of NE remains unknown. Here, we tested the hypothesis that neuronal innervation of PVAT stimulates adipocytes via NE. Mesenteric (mPVAT), aortic (aPVAT), and subcutaneous fat (sc) depots were studied in healthy male and female mice aged 8-12 weeks. Immunostaining with neuronal and vasculature markers was performed to assess anatomical evidence of neural innervation (n=3 region/sex). Adipocyte activity was studied in Adiponectin Cre;GCaMP 5g-tdT mice, which express the calcium indicator GCaMP5g in adipocytes (125-350 cells/group). Adipocytes were challenged with NE, a parasympathomimetic (bethanechol, 10uM, bath application), and nerve fibers were activated by electrical field stimulation (EFS; +100V, 0.1ms, 10 Hz). Immunolabeling data show that nerve fibers run adjacent to the larger blood vessels within adipose tissue, rather than radiating throughout. Stimulation with NE induced large responses (female: 0.91±0.73, 1.15±0.73, 1.45±0.9 dF/F 0 ; male: 0.75±0.57, 1.01±0.78, 0.73±0.53 dF/F 0 in aPVAT, mPVAT, sc, respectively). Both the parasympathomimetic and EFS induced minimal adipocyte responses compared to NE (% NE = [dF/F 0 bethanechol or EFS / dF/F 0 NE]*100%; bethanechol - female: 39.5%, 13.9%, 9.7%, male: 24.0%, 14.6%, 15.1% in aPVAT, mPVAT, sc, respectively; EFS - female: 31%, 12.2%, 9.7%, male: 28%, 13.9%, 13.7% in aPVAT, mPVAT, sc, respectively). These findings suggest that neural innervation within the PVAT, and functional regulation of adipocytes, is limited. Nerve fibers present within the PVAT are not the primary source of NE driving adipocyte production of anticontractile factors in the PVAT. Rather, this NE originates from other mechanisms including local production by non-neuronal cells or circulation of neurotransmitters.