Effect of motilin on gastric distension sensitive neurons in arcuate nucleus and gastric motility in rat

Effects of remimazolam tosilate on gastrointestinal hormones and gastrointestinal motility in patients undergoing gastrointestinal endoscopy with sedation: a randomized control trial

PURPOSE

To investigate the impacts of remimazolam tosilate on gastrointestinal hormones and motility in patients undergoing gastrointestinal endoscopy with sedation.

METHODS

A total of 262 American Society of Anesthesiologists Physical Status I or II patients, aged 18-65 years, scheduled for gastrointestinal endoscopy with sedation, were randomly allocated into two groups (n = 131 each): the remimazolam tosilate group (Group R) and the propofol group (Group P). Patients in Group R received 0.2-0.25 mg/Kg remimazolam tosilate intravenously, while those in Group P received 1.5-2.0 mg/kg propofol intravenously. The gastrointestinal endoscopy was performed when the Modified Observer's Assessment of Alertness/Sedation scores were ≤3. The primary endpoints included the endoscopic intestinal peristalsis rating by the endoscopist; serum motilin and gastrin levels at fasting without gastrointestinal preparation (T0), before gastrointestinal endoscopy (T1), and before leaving the Post Anesthesia Care Unit (T2); and the incidences of abdominal distension during Post Anesthesia Care Unit.

RESULTS

Compared with Group P, intestinal peristalsis rating was higher in Group R (P < .001); Group R showed increased motilin and gastrin levels at T2 compared with Group P (P < .01). There was a rise in motilin and gastrin levels at T1 and T2 compared with T0 and at T2 compared with T1 in both groups (P < .01). The incidence of abdominal distension was lower in Group R (P < .05).

CONCLUSION

Compared with propofol used during gastrointestinal endoscopy with sedation, remimazolam tosilate mildly inhibits the serum motilin and gastrin levels, potentially facilitating the recovery of gastrointestinal motility.

Why is motilin active in some studies with mice, rats, and guinea pigs, but not in others? Implications for functional variability among rodents

The gastrointestinal (GI) hormone motilin helps control human stomach movements during hunger and promotes hunger. Although widely present among mammals, it is generally accepted that in rodents the genes for motilin and/or its receptor have undergone pseudonymization, so exogenous motilin cannot function. However, several publications describe functions of low concentrations of motilin, usually within the GI tract and CNS of mice, rats, and guinea pigs. These animals were from institute-held stocks, simply described with stock names (e.g., "Sprague-Dawley") or were inbred strains. It is speculated that variation in source/type of animal introduces genetic variations to promote motilin-sensitive pathways. Perhaps, in some populations, motilin receptors exist, or a different functionally-active receptor has a good affinity for motilin (indicating evolutionary pressures to retain motilin functions). The ghrelin receptor has the closest sequence homology, yet in non-rodents the receptors have a poor affinity for each other's cognate ligand. In rodents, ghrelin may substitute for certain GI functions of motilin, but no good evidence suggests rodent ghrelin receptors are highly responsive to motilin. It remains unknown if motilin has functional relationships with additional bioactive molecules formed from the ghrelin and motilin genes, or if a 5-TM motilin receptor has influence in rodents (e.g., to dimerize with GPCRs and create different pharmacological profiles). Is the absence/presence of responses to motilin in rodents' characteristic for systems undergoing gene pseudonymization? What are the consequences of rodent supplier-dependent variations in motilin sensitivity (or other ligands for receptors undergoing pseudonymization) on gross physiological functions? These are important questions for understanding animal variation.

Study on the Effect of Antiplatelet and Gastric Mucosal Protection of Traditional Chinese Medicine Invigorating Qi and Hemostasis

Background

To investigate the effects of Chinese herbal medicine in tonifying qi and attaining hemostasis caused by the metabolism of the drug clopidogrel and as a result of platelet and gastric mucosa injury in an ischemia-reperfusion rat model.

Methods

A pharmacokinetic model was established to record the drug metabolism parameters of clopidogrel metabolites. Then, absorption of the drug was compared with approaches using the traditional Chinese medicine (TCM) approach of tonifying qi and establishing hemostasis, to using the drug pantoprazole and applying these approaches in combination with clopidogrel. Intragastric administration was performed, and all indicators were tested.

Results

The area under the curve (AUC; 0–T, 300.342 ± 35.832 mg/L* h; AUC 0–∞, 320.462 ± 40.213 mg/L* h), the plasma peak concentration (30.622 ± 9.917 mg/L*), and the peak time and half-life (7.954 ± 1.121 h) in the clopidogrel and the TCM groups were higher than those in the clopidogrel and pantoprazole groups. In terms of antiplatelet aggregation, compared with model group, the platelet aggregation rate induced by arachidonic acid (AA) and adenosine diphosphate (ADP) was significantly decreased by the TCM approach of tonifying qi and stopping bleeding (p < 0.05). The ADP, thromboxane A2, GPII B/Pa-A, CD62P and platelet factor 4 content in the TCM yiqi decoction and hemostasis approach were significantly decreased (p < 0.01). Compared with the clopidogrel group, the gastrin and motilin in the serum, the cyclooxygenase (COX)-1 and prostaglandin E2 in gastric tissue, and expression of vascular endothelial growth factor messenger ribonucleic acid in the serum were all significantly increased using TCM approach to protect against gastric mucosal injury (p < 0.05).

Conclusion

TCM invigorating qi and hemostasis has an inhibitory effect on platelet activation. It can reduce the local inflammatory reaction at the same time as protecting gastric mucosa.

Exogenous Orexin-A Microinjected Into Central Nucleus of the Amygdala Modulates Feeding and Gastric Motility in Rats

Orexin-A is a circulating neuropeptide and neurotransmitter that regulates food intake and gastric motility. The central nucleus of the amygdala (CeA), which regulates feeding behavior and gastric function, expresses the orexin-1 receptor. The aim of this study was to evaluate the effects of microinjection of exogenous orexin-A into the CeA, on food intake and gastric motility, and to explore the mechanisms of these effects. Normal chow and high fat food (HFF) intake were measured, gastric motility and gastric emptying were evaluated, extracellular single unit firing was recorded, and c-fos expression was determined. The results showed that microinjection of orexin-A into the CeA resulted in increased HFF intake but did not affect normal chow intake. This effect was blocked by an orexin-1 receptor antagonist-SB-334867 and was partially blocked by a dopamine D1 receptor antagonist-SCH-23390. Gastric motility and gastric emptying were enhanced by orexin-A, and the former effect was abolished by subdiaphragmatic vagotomy. The firing frequency of gastric distention-related neurons was regulated by orexin-A via the orexin-1 receptor. Furthermore, c-fos expression was increased in the ventral tegmental area (VTA) and the nucleus accumbens (NAc), the lateral hypothalamus (LHA), and the dorsal motor nucleus of the vagus (DMV) in response to microinjection of orexin-A into the CeA. These findings showed that orexin-A regulated palatable food intake and gastric motility via the CeA. The LHA, the VTA, and the NAc may participate in palatable food intake and the CeA-DMV-vagus-stomach pathway may be involved in regulating gastric motility through the regulation of neuronal activity in the CeA.

Using the "target constituent removal combined with bioactivity assay" strategy to investigate the optimum arecoline content in charred areca nut

Charred areca nut (CAN) is used to treat dyspepsia and abdominal distension in children. However, reports revealed that arecoline, the most important active constituent of CAN, possesses potential toxicities. This study was designed to investigate the optimum arecoline content in CAN, using the "target constituent removal combined with bioactivity assay" strategy. Based on PTLC method, we prepared CAN lacking all arecoline (WAC-100R) and a series of different ratios of arecoline-removed CAN samples (WAC-Rx). MTT and acute toxicity assays indicated that decreasing content by 50% decreased CAN toxicity significantly. Animal results revealed arecoline contents over 50% could guarantee the beneficial effects of CAN on gastrointestinal tract. Additionally, decreasing arecoline content in CAN by 50% decreased its pro-apoptotic effects significantly. Furthermore, decreasing 50% arecoline content in CAN down-regulated the expressions of Cleaved-Caspase-3, c-jun, c-fos, COX-2, PGE2, and IL-1α. Thus, our results revealed that CAN with 50% arecoline content (WAC-50R) has similar beneficial effects on the gastrointestinal tract to CAN, whereas its toxicity was decreased significantly. Collectively, our study suggested that the strategy of "target constituent removal combined with bioactivity assay" is a promising method to identify the optimum arecoline content in CAN, which is approximately 0.12%.

Neural mechanism of gastric motility regulation by electroacupuncture at RN12 and BL21: A paraventricular hypothalamic nucleus-dorsal vagal complex-vagus nerve-gastric channel pathway

AIM: To study the neural mechanism by which electroacupuncture (EA) at RN12 (Zhongwan) and BL21 (Weishu) regulates gastric motility.

METHODS: One hundred and forty-four adult Sprague Dawley rats were studied in four separate experiments. Intragastric pressure was measured using custom-made rubber balloons, and extracellular neuron firing activity, which is sensitive to gastric distention in the dorsal vagal complex (DVC), was recorded by an electrophysiological technique. The expression levels of c-fos, motilin (MTL) and gastrin (GAS) in the paraventricular hypothalamic nucleus (PVN) were assayed by immunohistochemistry, and the expression levels of motilin receptor (MTL-R) and gastrin receptor (GAS-R) in both the PVN and the gastric antrum were assayed by western blotting.

RESULTS: EA at RN12 + BL21 (gastric Shu and Mu points), BL21 (gastric Back-Shu point), RN12 (gastric Front-Mu point), resulted in increased neuron-activating frequency in the DVC (2.08 ± 0.050, 1.17 ± 0.023, 1.55 ± 0.079 vs 0.75 ± 0.046, P < 0.001) compared with a model group. The expression of c-fos (36.24 ± 1.67, 29.41 ± 2.55, 31.79 ± 3.00 vs 5.73 ± 2.18, P < 0.001), MTL (22.48 ± 2.66, 20.76 ± 2.41, 19.17 ± 1.71 vs 11.68 ± 2.52, P < 0.001), GAS (24.99 ± 2.95, 21.69 ± 3.24, 23.03 ± 3.09 vs 12.53 ± 2.15, P < 0.001), MTL-R (1.39 ± 0.05, 1.22 ± 0.05, 1.17 ± 0.12 vs 0.84 ± 0.06, P < 0.001), and GAS-R (1.07 ± 0.07, 0.91 ± 0.06, 0.78 ± 0.05 vs 0.45 ± 0.04, P < 0.001) increased in the PVN after EA compared with the model group. The expression of MTL-R (1.46 ± 0.14, 1.26 ± 0.11, 0.99 ± 0.07 vs 0.65 ± 0.03, P < 0.001), and GAS-R (1.63 ± 0.11, 1.26 ± 0.16, 1.13 ± 0.02 vs 0.80 ± 0.11, P < 0.001) increased in the gastric antrum after EA compared with the model group. Damaging the PVN resulted in reduced intragastric pressure (13.67 ± 3.72 vs 4.27 ± 1.48, P < 0.001). These data demonstrate that the signals induced by EA stimulation of acupoints RN12 and BL21 are detectable in the DVC and the PVN, and increase the levels of gastrointestinal hormones and their receptors in the PVN and gastric antrum to regulate gastric motility.

CONCLUSION: EA at RN12 and BL21 regulates gastric motility, which may be achieved through the PVN-DVC-vagus-gastric neural pathway.

Extrinsic ghrelin in the paraventricular nucleus increases small intestinal motility in rats by activating central growth hormone secretagogue and enteric cholinergic receptors

BACKGROUND/OBJECTIVES

Ghrelin is a brain-gut peptide that regulates gastrointestinal (GI) motility. We hypothesized that the excitatory effect of ghrelin on the paraventricular nucleus (PVN) increases GI motility by activating the central growth hormone secretagogue receptor (GHSR) and central neuropeptide Y (NPY) signaling pathways, leading to increased enteric cholinergic activity.

METHODS

Thirty-six male Sprague Dawley rats were maintained on duodenal catheterization and PVN cannulation. Small intestinal transit (SIT) was observed and rats were divided as follows: experimental animals received ghrelin injections in the PVN (0.03, 0.08, or 0.24 nM); 1 nM GHSR antagonist D-Lys3-GHRP6 alone; 1nM D-Lys3-GHRP6 before ghrelin injection in the PVN, respectively. Electrophysiologic parameters of the interdigestive myoelectric complex (IMC) were examined by administration of 0.24 nM ghrelin in the PVN after small intestinal electrode implantation and PVN cannulation. GI cholinergic pathway activation was analyzed after intravenous atropine administration. The involvement of central NPY signaling was evaluated by injecting an anti-NPY immunoglobulin (IgG) in the PVN. Neuronal expression of c-Fos in the brain and GI tract was examined using immunohistochemistry.

RESULTS

Injection of ghrelin in the PVN dose-dependently accelerated SIT, and this excitatory effect was competitively inhibited by a GHSR antagonist. The excitatory effect of ghrelin on IMC activity was diminished by GHSR antagonism and NPY neutralization, as well as by blockade of peripheral muscarinic acetylcholine receptors. Extrinsic ghrelin significantly upregulated c-Fos expression in the PVN and other central nuclei, as well as in the enteric nervous plexuses of the stomach, duodenum, and proximal colon. The ghrelin-induced upregulation of central and enteric c-Fos expression was also dependent on central GHSR activation.

CONCLUSIONS

Ghrelin positively regulates GI motility by exciting both central and enteric neurons, including those of the PVN, by activating GHSR and NPY pathways, and peripheral muscarinic acetylcholine receptors.

The stimulating effect of ghrelin on gastric motility and firing activity of gastric-distension-sensitive hippocampal neurons and its underlying regulation by the hypothalamus

Ghrelin is an acylated peptide originally identified in the rat stomach as the endogenous ligand for growth hormone secretagogue receptor (GHSR) that promotes gastric motility. Our aims were to explore the effects of ghrelin on gastric-distension-sensitive neurons in the hippocampus and the potential for ghrelin to regulate gastric motility through the arcuate nucleus (Arc). Single-unit discharges in the hippocampus were recorded extracellularly, and gastric motility in conscious rats was monitored. The expression of GHSR-1a in the hippocampus was determined by PCR, Western blot and fluo-immunohistochemistry staining. Retrograde tracing and fluo-immunohistochemistry staining were used to determine ghrelin neuron projection. Ghrelin-Fluoro-Gold double-labelled neurons and GHSR-1a expression were observed in the Arc and hippocampus, respectively. There were gastric-distension-sensitive neurons in the hippocampus that could be excited by ghrelin or by electrical stimulation of the Arc. The excitatory effects could be blocked completely or partly by pretreatment with the ghrelin receptor antagonist [d-Lys-3]-GHRP-6. Gastric motility was significantly promoted by the administration of ghrelin into the hippocampus in a dose-dependent manner that could be completely abolished by [d-Lys-3]-GHRP-6. Electrical stimulation of the Arc could promote gastric motility as well. Nevertheless, these effects could be mitigated by pretreatment with [d-Lys-3]-GHRP-6. Electrical lesioning of the hippocampus diminished the excitatory effects on gastric motility that were induced by electrical stimulation the Arc. Our findings suggest that ghrelin plays an important role in promoting gastric motility via the hippocampus. The Arc may be involved in regulation of the influence of the hippocampus on gastric motility.

Motilin receptor neuropharmacology: revised understanding

Although motilin was identified >40 years ago as a gastrointestinal hormone capable of stimulating gastric emptying, the relatively recent availability of molecular tools and focus on its neuronal activities are now clarifying mechanisms of action. In rodents, only motilin receptor pseudogenes are identified. In human stomach, facilitation of enteric cholinergic activity is identified as the main mechanism by which gastric emptying is increased; some motilin agonists act in a prolonged manner, contrasting with motilin itself and with studies using recombinant receptors. As such, assays using recombinant receptors seem poor predictors of in vivo activity. High-throughput screening enabled selective motilin agonists to be identified, which together with enhanced understanding into neuromuscular actions of motilin, promises to deliver rational treatments of disorders with delayed gastric emptying.

The translational value of rodent gastrointestinal functions: a cautionary tale

Understanding relationships between gene complements and physiology is important, especially where major species-dependent differences are apparent. Molecular and functional differences between rodents (rats, mice, guinea pigs) and humans are increasingly reported. Recently, the motilin gene, which encodes a gastrointestinal hormone widely detected in mammals, was found to be absent in rodents where the receptors are pseudogenes; however, actions of motilin in rodents are sometimes observed. Although ghrelin shares common ancestry with motilin, major species-dependent abberations are not reported. The apparently specific absence of functional motilin in rodents is associated with specialised digestive physiology, including loss of ability to vomit; motilin is functional in mammals capable of vomiting. The exception is rabbit, the only other mammal unable to vomit, in which motilin might be conserved to regulate caecotrophy, another specialised digestive process. Motilin illustrates a need for caution when translating animal functions to humans. Nevertheless, motilin receptor agonists are under development as gastroprokinetic drugs.