Non-invasive peripheral focused ultrasound neuromodulation of the celiac plexus ameliorates symptoms in a rat model of inflammatory bowel disease.

NEW FINDINGS: What is the central question of this study? Does peripheral non-invasive focused ultrasound targeted to the celiac plexus improve inflammatory bowel disease? What is the main finding and its importance? Peripheral non-invasive focused ultrasound targeted to the celiac plexus in a rat model of ulcerative colitis improved stool consistency and reduced stool bloodiness, which coincided with a longer and healthier colon than in animals without focused ultrasound treatment. The findings suggest that this novel neuromodulatory technology could serve as a plausible therapeutic approach for improving symptoms of inflammatory bowel disease. ABSTRACT: Individuals suffering from inflammatory bowel disease (IBD) experience significantly diminished quality of life. Here, we aim to stimulate the celiac plexus with non-invasive peripheral focused ultrasound (FUS) to modulate the enteric cholinergic anti-inflammatory pathway. This approach may have clinical utility as an efficacious IBD treatment given the non-invasive and targeted nature of this therapy. We employed the dextran sodium sulfate (DSS) model of colitis, administering lower (5%) and higher (7%) doses to rats in drinking water. FUS on the celiac plexus administered twice a day for 12 consecutive days to rats with severe IBD improved stool consistency scores from 2.2 ± 1 to 1.0 ± 0.0 with peak efficacy on day 5 and maximum reduction in gross bleeding scores from 1.8 ± 0.8 to 0.8 ± 0.8 on day 6. Similar improvements were seen in animals in the low dose DSS group, who received FUS only once daily for 12 days. Moreover, animals in the high dose DSS group receiving FUS twice daily maintained colon length (17.7 ± 2.5 cm), while rats drinking DSS without FUS exhibited marked damage and shortening of the colon (13.8 ± 0.6 cm) as expected. Inflammatory cytokines such as interleukin (IL)-1ß, IL-6, IL-17, tumour necrosis factor-α and interferon-γ were reduced with DSS but coincided with control levels after FUS, which is plausibly due to a loss of colon crypts in the former and healthier crypts in the latter. Lastly, overall, these results suggest non-invasive FUS of peripheral ganglion can deliver precision therapy to improve IBD symptomology.

Pharmacological comparison of P2X receptors on rat coeliac, mouse coeliac and mouse pelvic ganglion neurons.

Characteristics of P2X receptors on neurons of the rat coeliac, mouse coeliac and mouse pelvic ganglia have been studied using the whole cell voltage-clamp technique. Fast application of ATP (100 microM) on to isolated neurons voltage clamped at -70 mV induced a slowly desensitising inward current in 96% of the cells tested. Concentration-response curves for ATP yielded EC50 values of 86 microM, 64 microM and 123 microM, for rat coeliac, mouse coeliac and mouse pelvic ganglion neurons, respectively, while alpha,beta-methylene ATP was inactive. The response to ATP was antagonised by suramin, Cibacron blue and pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS). The potency of ATP was increased by extracellular acidification and by co-application of micromolar concentrations of Zn2+, while raising pH decreased it. On rat coeliac ganglion neurons, the EC50 values for ATP were 35 microM and 253 microM at pH 6.8 and 8.0, respectively. On mouse coeliac and pelvic ganglion neurons, altering the pH produced comparable changes. In conclusion, our results indicate that, in contrast to the guinea-pig coeliac ganglion, the characteristics of the P2X receptors present on rat coeliac, mouse coeliac and mouse pelvic ganglia are all identical to those present on rat pelvic ganglion, i.e. they are homomeric P2X2 receptors, or heteromultimers with P2X2 being the dominant subunit.

Neurotensin facilitates release of substance P in the guinea-pig inferior mesenteric ganglion.

1. Intracellular, electrophysiological techniques were combined with radio-immunological, chromatographic and pharmacological techniques to determine if nerve terminals containing substance P mediated transient depolarizing responses of principal ganglion cells induced by neurotensin. Experiments were performed in vitro on guinea-pig inferior mesenteric ganglia. 2. In 61% of principal ganglion cells tested in normal ganglia, neurotensin caused a transient membrane depolarization. In ganglia which were removed from animals which had been pre-treated with capsaicin, transient responses to neurotensin were virtually abolished. 3. In normal ganglia, neurotensin increased the amplitude and duration of noncholinergic slow EPSPs evoked by electrical stimulation of the lumbar colonic nerve. Such increases were absent in ganglia obtained from animals pre-treated with capsaicin. 4. In guinea-pigs pre-treated with capsaicin, the content of substance P-like material was significantly reduced in inferior mesenteric and coeliac ganglia, dorsal root ganglia and lumbar spinal cord, compared to control animals. The content of substance P-like material in segments of distal colon was slightly reduced. The content of vasoactive intestinal polypeptide-, cholecystokinin- and bombesin-like material in the same tissues from animals pre-treated with capsaicin was not significantly different from control animals. 5. Chromatographic analysis using HPLC (high-performance liquid chromatography) techniques revealed that the material depleted from inferior mesenteric and coeliac ganglia, dorsal root ganglia and lumbar spinal cord by capsaicin pre-treatment co-eluted with synthetic substance P. 6. Electrical stimulation of the lumbar colonic nerve released substance P-like material from isolated inferior mesenteric ganglia as determined by radioimmunoassay of samples of superfusate. Exogenous administration of neurotensin caused a significant increase in the amount of substance P-like material released during nerve stimulation. 7. Transient depolarizing responses evoked by neurotensin were markedly attenuated when ganglion cells were postsynaptically desensitized to exogenously administered substance P. 8. Taken together, these findings suggest that transient depolarizations mediated by an indirect action of neurotensin and facilitation of electrically evoked non-cholinergic slow EPSPs by neurotensin involved presynaptic release of substance P from collateral nerve terminals of primary afferent nerve fibres in the inferior mesenteric ganglion. 9. It was suggested that under normal in vivo conditions, neurotensin or a C-terminal-related peptide contained in central preganglionic nerve endings might function as an excitatory neuromodulator to enhance the release of substance P from primary afferent nerve terminals thereby facilitating non-cholinergic peripheral afferent synaptic input to prevertebral ganglion cells.