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Background: Inhibitory neuromuscular transmission in the gastrointestinal tract is mediated by intrinsic nitrergic and purinergic neurons. Purines activate G protein-coupled receptor P2Y 1 receptors, increasing intracellular Ca 2+ that activates small conductance calcium-activated potassium (SK Ca ) channels. Little is known about the effect of adrenergic receptor activation on intestinal smooth muscle. In vascular tissue, stimulation of α-adrenoceptors causes smooth muscle contraction, while their effect on intestinal tissue is poorly understood. This study aimed to pharmacologically characterize the effect of α-adrenoceptor activation in the rat colon, which shares similar inhibitory pathways to the human colon., Methods: Muscle bath experiments were performed with the rat proximal, mid, and distal colon oriented both circularly and longitudinally., Results: The α 1 -adrenoceptor agonist phenylephrine (PE) (10 -8 -10 -5  M) evoked concentration-dependent relaxations of the intestinal smooth muscle from all regions and orientations. However, in the mid-circular colon at low PE concentrations, a contraction sensitive to 10 -5  M phentolamine (non-selective α-adrenoceptor blocker), the neural blocker tetrodotoxin (TTX; 10 -6  M), and atropine (10 -6  M) was recorded. PE-induced relaxations were insensitive to TTX (10 -6  M) and the nonselective β-adrenoceptor blocker propranolol (10 -6  M). In contrast, PE-induced relaxations were blocked by phentolamine (10 -5  M), prazosin (10 -6  M) (α 1 -adrenoceptor blocker), and RS17053 (10 -6  M) (α 1A -blocker), but not by yohimbine (10 -6  M) (α 2 -adrenoceptor blocker). Apamin (10 -6  M), a SK Ca channel blocker, abolished PE-induced relaxations., Conclusions: Contractile responses in the circular muscle of the mid colon could be attributed to α-adrenoceptors located on enteric cholinergic neurons. Stimulation of α 1A -adrenoreceptors activates SK Ca channels to cause smooth muscle relaxation, which constitutes a signaling pathway that shares similarities with P2Y 1 receptors., (© 2024 The Author(s). Neurogastroenterology & Motility published by John Wiley & Sons Ltd.)

P2Y 1 receptors play an essential role in inhibitory neuromuscular transmission in the gastrointestinal tract. The signalling pathway involves the opening of small conductance calcium activated potassium-channels (K ca 2 family) that results in smooth muscle hyperpolarization and relaxation. Inorganic polyphosphates and dinucleotidic polyphosphates are putative neurotransmitters that potentially act on P2Y 1 receptors. A pharmacological approach using both orthosteric (MRS2500) and allosteric (BPTU) blockers of the P2Y 1 receptor and openers (CyPPA) and blockers (apamin) of K ca 2 channels was used to pharmacologically characterise the effect of these neurotransmitters. Organ bath and microelectrodes were used to evaluate the effect of P1,P4-Di (adenosine-5') tetraphosphate ammonium salt (Ap 4 A), inorganic polyphosphates (PolyP) and CyPPA on spontaneous contractions and membrane potential of mouse colonic smooth muscle cells. PolyP neither modified contractions nor membrane potential. In contrast, Ap 4 A caused a concentration-dependent inhibition of spontaneous contractions reaching a maximum effect at 100 μM Ap 4 A response was antagonised by MRS2500 (1 μM), BPTU (3 μM) and apamin (1 μM). CyPPA (10 μM) inhibited spontaneous contractions and this response was antagonised by apamin but it was not affected by MRS2500 or BPTU. Both CyPPA and Ap 4 A caused smooth muscle hyperpolarization that was blocked by apamin and MRS2500 respectively. We conclude that Ap 4 A but not PolyP activates P2Y 1 receptors causing smooth muscle hyperpolarization and relaxation. Ap 4 A signalling causes activation of K ca 2 channels through activation of P2Y 1 receptors. In contrast, CyPPA acts directly on K ca 2 channels. Further studies are needed to evaluate if dinucleotidic polyphosphates are released from inhibitory motor neurons., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background The pharmacological properties of otilonium bromide ( OB) have been investigated using different experimental models, techniques, and conditions, and consequently, the results are not always easy to compare. The aim of the present work was to investigate the pharmacological properties of OB in human cultured colonic smooth muscle cells ( HCSMCs), which is the main target of the drug ' in vivo'. Rat colonic strips were used to confirm the pharmacological properties. Methods Human cultured colonic smooth muscle cells were studied using the calcium imaging technique. Microelectrodes and muscle bath experiments were performed in rat colonic strips. Key Results Otilonium bromide ( OB) concentration dependently inhibited nifedipine-sensitive calcium transients induced by KCl ( EC50 = 3.6 μM) and BayK8644 ( EC50 = 4.0 μM). All the following experiments were performed in the presence of nifedipine. In HCSMC, carbachol-induced calcium transients were inhibited by OB ( EC50 = 8.4 μM). Carbachol evoked 1-a smooth muscle depolarization (10 mV) that was antagonized by 100 μM OB; and 2-a contraction that was inhibited by OB ( EC50 = 13.0 μM). 'Non-nitrergic (L- NNA 1 mM) non-purinergic ( MRS2500 1 μM)' conditions were used to elicit endogenous excitatory responses. Electrical field stimulation caused 1-an atropine-sensitive excitatory junction potential that was inhibited by OB ( EC50 = 8.9 μM) and 2-an atropine-sensitive contraction that was inhibited by OB ( EC50 = 7.3 μM). In HCSMC, neurokinin A ( NKA) and CaCl2 induced calcium transients that were inhibited by OB ( NKA: EC50 = 11.7 μM; CaCl2: EC50 = 17.5 μM). Conclusions & Inferences Otilonium bromide causes inhibition of L-/T-type calcium channels, muscarinic, and tachykininergic responses that acting together explain the pharmacological properties of the compound. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is a significant physiologic inhibitory neurotransmitter. The main goal of this research was to examine the contribution of diverse potassium (K + ) channels and nitric oxide (NO) in mediating the H 2 S effect on electrical field stimulation (EFS)-induced neurogenic contractile responses in the lower esophageal sphincter (LES). EFS-induced contractile responses of rabbit isolated LES strips were recorded using force transducers in organ baths that contain Krebs-Henseleit solutions (20 ml). Cumulative doses of NaHS, L-cysteine, PAG, and AOAA were evaluated in NO-dependent and NO-independent groups. The experiments were conducted again in the presence of K + channel blockers. In both NO-dependent and NO-independent groups, NaHS, L-cysteine, PAG, and AOAA significantly reduced EFS-induced contractile responses. In the NO-dependent group, the effect of NaHS and L-cysteine decreased in the presence of 4-AP, and also the effect of NaHS decreased in the NO-dependent and independent group in the presence of TEA. In the NO-independent group, K + channel blockers didn't change L-cysteine-induced relaxations. K + channel blockers had no impact on the effects of PAG and AOAA. In addition, NaHS significantly relaxed 80-mM KCl-induced contractions, whereas L-cysteine, PAG, and AOAA did not. In the present study, H 2 S decreased the amplitudes of EFS-induced contraction responses. These results suggest that Kv channels and NO significantly contribute to exogenous H 2 S and endogenous H 2 S precursor L-cysteine inhibitory effect on lower esophageal sphincter smooth muscle., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The enteric nervous system (ENS) is responsible for the genesis of motor patterns ensuring an appropriate intestinal transit. Enteric neurons are classified into afferent, interneuron, and motoneuron types, with the latter two being further categorized as excitatory or inhibitory, which cause smooth muscle contraction or inhibition, respectively. Muscle relaxation mechanisms are key for the understanding of physiological processes such as sphincter relaxation, gastric accommodation, or descending peristaltic reflex. Nitric oxide (NO) and ATP or a related purine represent the primary inhibitory neurotransmitters. Nitrergic neurons synthesize NO through nNOS enzyme activity. NO diffuses across the cell membrane to bind its receptor, namely, guanylyl cyclase, and then activates a number of intracellular mechanisms that ultimately result in muscle relaxation. ATP acts as an inhibitory neurotransmitter together with NO, and the purinergic P2Y1 membrane receptor has been identified as a key item in order to understand how ATP may relax intestinal smooth muscle. Although, probably, no clinician doubts the significance of NO in the pathophysiology of digestive motility, the relevance of purinergic neurotransmission is apparently much lower, as ATP has not been associated with any specific motor dysfunction yet. The goal of this review is to discuss the function of both relaxation mechanisms in order to establish the physiological grounds of potential motor dysfunctions arising from impaired intestinal relaxation.

P2Y1 receptors mediate nerve mediated purinergic inhibitory junction potentials (IJP) and relaxations in the gastrointestinal (GI) tract in a wide range of species including rodents and humans. A new P2Y1 antagonist, with a non-nucleotide structure, BPTU, has recently been described using X-ray crystallography as the first allosteric G-protein-coupled receptor antagonist located entirely outside of the helical bundle. In this study, we tested its effect on purinergic responses in the gastrointestinal tract of rodents using electrophysiological and myographic techniques. BPTU concentration dependently inhibited purinergic inhibitory junction potentials and inhibition of spontaneous motility induced by electrical field stimulation in the colon of rats (EC50 = 0.3 μM) and mice (EC50 = 0.06 μM). Mechanical inhibitory responses were also concentration-dependently blocked in the stomach of both species. Compared to MRS2500, BPTU displays a lower potency. In the rat colon nicotine induced relaxation was also blocked by BPTU. BPTU also blocked the cessation of spontaneous contractility elicited by ADPβS and the P2Y1 agonist MRS2365. We conclude that BPTU is a novel antagonist with different structural and functional properties than nucleotidic antagonists that is able to block the P2Y1 receptor located at the neuromuscular junction of the GI tract., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background Pharmacological studies using selective P2Y1 antagonists, such as MRS2500, and studies with P2Y1−/− knockout mice have demonstrated that purinergic neuromuscular transmission is mediated by P2Y1 receptors in the colon. The aim of the present study was to test whether P2Y1 receptors are involved in purinergic neurotransmission in the antrum and cecum. Methods Microelectrode recordings were performed on strips from the antrum and cecum of wild type animals (WT) and P2Y1−/− mice. Key Results In the antrum, no differences in resting membrane potential and slow wave activity were observed between groups. In WT animals, electrical field stimulation elicited a MRS2500-sensitive inhibitory junction potential (IJP). In P2Y1−/− mice, a nitrergic IJP ( Nω-nitro- l-arginine-sensitive), but not a purinergic IJP was recorded. This IJP was equivalent to the response obtained in strips from WT animals previously incubated with MRS2500. Similar results were obtained in the cecum: 1- the purinergic IJP (MRS2500-sensitive) recorded in WT animals was absent in P2Y1−/− mice 2- nitrergic neurotransmission was preserved in both groups. Moreover, 1- spontaneous IJP (MRS2500-sensitive) could be recorded in WT, but not in P2Y1−/− mice 2- MRS2365 a P2Y1 agonist caused smooth muscle hyperpolarization in WT, but not in P2Y1−/− animals, and 3- β-NAD caused smooth muscle hyperpolarization both in WT and P2Y1−/− animals. Conclusions & Inferences 1- P2Y1 receptor is the general mechanism of purinergic inhibition in the gastrointestinal tract, 2- P2Y1−/− mouse is a useful animal model to study selective impairment of purinergic neurotransmission and 3- P2Y1−/− mouse might help in the identification of purinergic neurotransmitter(s). [ABSTRACT FROM AUTHOR]

Interaction of different neuromyogenic mechanisms determines colonic motility. In rats, cyclic depolarizations and slow waves generate myogenic contractions of low frequency (LF) and high frequency (HF), respectively. Interstitial cells of Cajal (ICC) located near the submuscular plexus (SMP) generate slow waves. Inhibitory junction potential (IJP) consists on a purinergic fast (IJPf) followed by a nitrergic slow (IJPs) component leading to relaxation. In the present study, we characterized (1) the dynamics of purinergic-nitrergic inhibitory co-transmission and (2) its contribution on prolonged inhibition of myogenic activity. Different protocols of electrical field stimulation (EFS) under different pharmacological conditions were performed to characterize electrophysiological and mechanical responses. Smooth muscle cells (SMCs) in tissue devoid of ICC-SMP had a resting membrane potential (RMP) of -40.7 ± 0.7 mV. Single pulse protocols increased purinergic and nitrergic IJP amplitude in a voltage-dependent manner (IJPfMAX = -26.4 ± 0.6 mV, IJPsMAX = -6.7 ± 0.3 mV). Trains at increasing frequencies enhanced nitrergic (k = 0.8 ± 0.2 s, IJPs∞ = -15 ± 0.5 mV) whereas they attenuated purinergic responses (k = 3.4 ± 0.6 s,IJPf∞ = -8.9 ± 0.6 mV). In tissues with intact ICC-SMP, the RMP was -50.0 ± 0.9 mV and nifedipine insensitive slow waves (10.1 ± 2.0 mV, 10.3 ± 0.5 cpm) were recorded. In these cells, (1) nitrergic and purinergic responses were reduced and (2) slow waves maintained their intrinsic frequency and increased their amplitude under nerve-mediated hyperpolarization. Based on the co-transmission process and consistent with the expected results on RMP, prolonged EFS caused a progressive reduction of LF contractions whereas HF contractions were partially insensitive. In conclusion, inhibitory neurons modulate colonic spontaneous motility and the principles determining post-junctional responses are (1) the frequency of firing that determines the neurotransmitter/receptor involved, (2) the transwall gradient and (3) the origin and nature of each myogenic activity

The internal anal sphincter (IAS) functions to maintain continence. Previous studies utilizing mice with cell-specific expression of GCaMP6f revealed two distinct subtypes of intramuscular interstitial cells of Cajal (ICC-IM) with differing Ca2+ activities in the IAS. The present study further examined Ca2+ activity in ICC-IM and its modulation by inhibitory neurotransmission. The spatiotemporal properties of Ca2+ transients in Type II ICC-IM mimicked those of smooth muscle cells (SMCs), indicating their joint participation in the "SIP" syncytium. Electrical field stimulation (EFS; atropine present) abolished localized and whole cell Ca2+ transients in Type I and II ICC-IM. The purinergic antagonist MRS2500 did not abolish EFS responses in either cell type, whereas the nitric oxide synthase (NOS) inhibitor NG-nitro- l -arginine (l -NNA) abolished responses in Type I but not Type II ICC-IM. Combined antagonists abolished EFS responses in Type II ICC-IM. In both ICC-IM subtypes, the ability of EFS to inhibit Ca2+ release was abolished by l -NNA but not MRS2500, suggesting that the nitrergic pathway directly inhibits ICC-IM by blocking Ca2+ release from intracellular stores. Since inositol (1,4,5)-trisphosphate receptor-associated cGMP kinase substrate I (IRAG1) is expressed in ICC-IM, it is possible that it participates in the inhibition of Ca2+ release by nitric oxide. Platelet-derived growth factor receptor α (PDGFRα)+ cells but not ICC-IM expressed P2Y1 receptors (P2Y1R) and small-conductance Ca2+-activated K+ channels (SK3), suggesting that the purinergic pathway indirectly blocks whole cell Ca2+ transients in Type II ICC-IM via PDGFRα+ cells. This study provides the first direct evidence for functional coupling between inhibitory motor neurons and ICC-IM subtypes in the IAS, with contractile inhibition ultimately dependent upon electrical coupling between SMCs, ICC, and PDGFRα+ cells via the SIP syncytium. NEW & NOTEWORTHY: Two intramuscular interstitial cells of Cajal (ICC-IM) subtypes exist within the internal anal sphincter (IAS). This study provides the first evidence for direct coupling between nitrergic motor neurons and both ICC-IM subtypes as well as indirect coupling between purinergic inputs and Type II ICC-IM. The spatiotemporal properties of whole cell Ca2+ transients in Type II ICC-IM mimic those of smooth muscle cells (SMCs), suggesting that ICC-IM modulate the activity of SMCs via their joint participation in a SIP syncytium (SMCs, ICC, and PDGFRα+ cells). Listen to this article's corresponding podcast at https://ajpgi.podbean.com/e/got-guts-the-micro-version-inhibitory-neurotransmission-in-the-internal-anal-sphincter/. [ABSTRACT FROM AUTHOR]

The purine receptor involved in inhibitory responses in the gastrointestinal tract has been recently identified. P2Y1 receptor activation mediates the fast component of the inhibitory junction potential (IJPf) and the non-nitrergic relaxation. The aim of the present work has been to investigate which purinergic agonist better mimics endogenous responses. We used different agonist and antagonist of P2 receptors. Contractility and microelectrode experiments were used to compare the effects of exogenously added purines and electrical field stimulation (EFS)-induced nerve mediated effects in rat and human colonic strips. In rat colon, the IJPf and EFS-induced inhibition of contractions were concentration-dependently inhibited by the P2Y1 antagonist MRS2500 but not by iso-PPADS or NF023 (P2X antagonists) up to 1 μM. In samples from human colon, EFS-induced inhibition of contractions was inhibited by either MRS2500 or apamin (1 μM) but not by iso-PPADS. In both species, α,β-meATP, a stable analog of ATP, caused inhibition of spontaneous contractions. α,β-meATP effect was concentration-dependent (EC50: 2.7 μM rat, 4.4 μM human) and was antagonized by either MRS2500 or apamin but unaffected by P2X antagonists. ATP, ADP, β-NAD and ADP-ribose inhibited spontaneous contractions but did not show the same sensitivity profile to purine receptor antagonists as EFS-induced inhibition of contractions. The effect of α,β-meATP is due to P2Y1 receptor activation leading the opening of sKca channels. Accordingly, α,β-meATP mimics the endogenous purinergic mediator. In contrast, exogenously added putative neurotransmitters do not exactly mimic the endogenous mediator. Quick degradation by ecto-nuclease or different distribution of receptors (junctionally vs extrajunctionally) might explain these results., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Purinergic signaling is a crucial determinant in the regulation of pulmonary vascular physiology and presents a promising avenue for addressing lung diseases. This intricate signaling system encompasses two primary receptor classes: P1 and P2 receptors. P1 receptors selectively bind adenosine, while P2 receptors exhibit an affinity for ATP, ADP, UTP, and UDP. Functionally, P1 receptors are associated with vasodilation, while P2 receptors mediate vasoconstriction, particularly in basally relaxed vessels, through modulation of intracellular Ca2+ levels. The P2X subtype receptors facilitate extracellular Ca2+ influx, while the P2Y subtype receptors are linked to endoplasmic reticulum Ca2+ release. Notably, the primary receptor responsible for ATP-induced vasoconstriction is P2X1, with α,β-meATP and UDP being identified as potent vasoconstrictor agonists. Interestingly, ATP has been shown to induce endothelium-dependent vasodilation in pre-constricted vessels, associated with nitric oxide (NO) release. In the context of P1 receptors, adenosine stimulation of pulmonary vessels has been unequivocally demonstrated to induce vasodilation, with a clear dependency on the A2B receptor, as evidenced in studies involving guinea pigs and rats. Importantly, evidence strongly suggests that this vasodilation occurs independently of endothelium-mediated mechanisms. Furthermore, studies have revealed variations in the expression of purinergic receptors across different vessel sizes, with reports indicating notably higher expression of P2Y1, P2Y2, and P2Y4 receptors in small pulmonary arteries. While the existing evidence in this area is still emerging, it underscores the urgent need for a comprehensive examination of the specific characteristics of purinergic signaling in the regulation of pulmonary vascular tone, particularly focusing on the disparities observed across different intrapulmonary vessel sizes. Consequently, this review aims to meticulously explore the current evidence regarding the role of purinergic signaling in pulmonary vascular tone regulation, with a specific emphasis on the variations observed in intrapulmonary vessel sizes. This endeavor is critical, as purinergic signaling holds substantial promise in the modulation of vascular tone and in the proactive prevention and treatment of pulmonary vascular diseases. [ABSTRACT FROM AUTHOR]

Purinergic and nitrergic co-transmission is the dominant mechanism responsible for neural-mediated smooth muscle relaxation in the gastrointestinal tract. The aim of the present paper was to test whether or not P2Y(1) receptors are involved in purinergic neurotransmission using P2Y(1)(−/−) knock-out mice. Tension and microelectrode recordings were performed on colonic strips. In wild type (WT) animals, electrical field stimulation (EFS) caused an inhibitory junction potential (IJP) that consisted of a fast IJP (MRS2500 sensitive, 1 μm) followed by a sustained IJP (N(ω)-nitro-L-arginine (L-NNA) sensitive, 1 mm). The fast component of the IJP was absent in P2Y(1)(−/−) mice whereas the sustained IJP (L-NNA sensitive) was recorded. In WT animals, EFS-induced inhibition of spontaneous motility was blocked by the consecutive addition of L-NNA and MRS2500. In P2Y(1)(−/−) mice, EFS responses were completely blocked by L-NNA. In WT and P2Y(1)(−/−) animals, L-NNA induced a smooth muscle depolarization but ‘spontaneous' IJP (MRS2500 sensitive) could be recorded in WT but not in P2Y(1)(−/−) animals. Finally, in WT animals, 1 μm MRS2365 caused a smooth muscle hyperpolarization that was blocked by 1 μm MRS2500. In contrast, 1 μm MRS2365 did not modify smooth muscle resting membrane potential in P2Y(1)(−/−) mice. β-Nicotinamide adenine dinucleotide (β-NAD, 1 mm) partially mimicked the effect of MRS2365. We conclude that P2Y(1) receptors mediate purinergic neurotransmission in the gastrointestinal tract and β-NAD partially fulfils the criteria to participate in rodent purinergic neurotransmission. The P2Y(1)(−/−) mouse is a useful animal model to study the selective loss of purinergic neurotransmission.

According to previous reviews, hemoperitoneum episodes appear in 6.1-8.4% of the peritoneal dialysis patients, and they are severe in a 20% of them. Due to the absence of severe hemoperitoneum in our peritoneal dialysis program, we retrospectively reviewed hemoperitoneum non-related with abdominal surgery or catheter placing. We analyzed its incidence, etiology, prognostic and clinical outcome, as well as the possible effect of recurrent hemoperitoneum on peritoneal function. A total of 132 patients were treated in our centre during a period of 173 months. Mean age at the beginning of peritoneal dialysis was 59+/-17.1 years, 43.2% were females, and 22.8% of them were menstruating women. Twenty-two patients had at least one hemoperitoneum episode during follow-up, with an incidence of 17%. The mean time interval between the start of peritoneal dialysis and the first hemoperitoneum episode was 0.66+/-0.94 years (range: 0.01-3.20 years). 73% were women. Most cases (59%) were due to menstruation. Remarkably, all the menstruating women presented hemoperitoneum at least once with a high incidence of recurrent episodes. The other hemoperitoneum episodes were mainly of unknown etiology (32% of patients), being this one the main cause in males. We only observed two more cases: a male who presented hemoperitoneum related to dicumarinic overdose and a female who presented hemoperitoneum due to mesenteric ischemia. All the 22 patients had a favourable outcome, except for the woman with mesenteric ischemia, what represented an incidence of 4.5% of severe hemoperitoneum. No significant association was found between episodes of hemoperitoneum and aspirin treatment, dicumarinic treatment or the presence of coagulopathy. There was no association either between recurrent hemoperitoneum and the number of peritonitis episodes, peritoneal function or technique survival. In conclusion, hemoperitoneum is a common and usually benign problem in peritoneal dialysis patients, frequently due to retrograde menstruation, and no deleterious long-term effects were found in patients with recurrent hemoperitoneum.

Traits of the gastrointestinal (GI) tract are phenotypically flexible and seem to reflect the ecological features of animals. The Daurian ground squirrel (Spermophilus dauricus) is a typical fat-storing, hibernating animal. However, information on seasonal GI plasticity in this species is limited. The aim of the present study was to characterize the morphology, histology, and genetic regulation involved in GI motility in the ground squirrel during non-hibernating and hibernating seasons. The morphological and histological results showed that the body weight, total fresh weight, and total net fresh weight of the GI tract in summer and autumn were higher than those in spring and the winter hibernation season, although the total length of the gut did not change seasonally. The fresh weight and net fresh weight of the small intestine, cecum, and large intestine were significantly greater in autumn and summer than in winter, but the lengths of these segments showed no significant seasonal differences. The mucosal and muscular layer thicknesses of the stomach, illum, cecum, and colon were greater in autumn or summer than in winter, and the small intestine diameter and villus height were decreased in winter compared to those in the spring or summer. Moreover, the expression of nNOS and NPY genes in the small intestine in autumn and winter was higher than that in spring or summer. VIP expression in winter was the highest across seasons; in contrast, CHRM2 expression in autumn was the highest across seasons. These results indicate that morphological and histological traits of the gut, as well motility adjustments, exhibit seasonal plasticity in the ground squirrel, and these are especially affected by the hibernating cycle. This work will expand our knowledge of GI phenotypic plasticity in hibernating rodent species. [ABSTRACT FROM AUTHOR]

Vascular access through a venous catheter for haemodialysis is associated with increased risk of thrombosis, central venous stenosis, short access survival and inadequate dialysis. The most important catheter-related complications, which determine method survival, are infection and dysfunction. In particular, infectious episodes are in some studies the leading cause for untimely catheter removal and for catheter-related morbidity but also for morbidity in dialysis patients. Double-lumen central venous catheters used for haemodialysis, are common causes of septicaemia. Most cases are caused by staphylococci. Episodes of gram-negative bacteriemia have been traced to bacterial contamination of water and/or dialysate, errors in dialyzer reprocessing, and improper setup procedures. In this paper, we describe and outbreak of gram-negative bacteremia, firstly E. cloacae, in an outpatients haemodialysis unit, in the patients with long-term tunnelled haemodialysis catheters. We describe the epidemic investigation that we achieved to identify the source of contaminating bacteria and the route by which bacteria gained access to the bloodstream. We prove the contamination by gram-negative bacterium of the water-distribution lines and haemodialysis machines. Moreover, E. cloacae strains isolated from the lines and machines are genotypically identical to the isolated from the patients. Also, we prove that the hands of health care personnel are unintentional carriers. The outbreak was finished when decontamination of dialysis machines was enhanced and dialyzer-priming fluid was modified.

This study looked at the incidence of infection complications, in relation to central vein catheterisation as a provisional HD access, by means of the establishment of a nursing protocol for the handling of these catheters. Central vein catheterisation is a classical technique in Nephrology.

This study was designed to explore the expression changes of P2Y1 receptors in the distal colonic myenteric layer of rats. An opioid induced constipation(OIC) rat model was generated by intraperitoneal (i.p) injection of loperamide. At 7 days post-treatment, the model rats were assessed by calculating the fecal water content and the gastrointestinal transit ratio. The immunofluorescence (IF)-based histochemical study was used to observe the distribution of P2Y1 receptors in the distal colonic myenteric plexus. Western blotting (WB) was performed to evaluate the expression changes of P2Y1 proteins in the myenteric layer, and the electrophysiological approaches were carried out to determine the regulatory roles of P2Y1 receptors on distal colonic motor function. IF showed that P2Y1 receptors are co-expressed MOR in the enteric nerve cells of the distal colonic myenteric plexus. Moreover, the WB revealed that the protein levels of P2Y1 were significantly decreased in the distal colonic myenteric layer of OIC rats. In vitro tension experiments exhibited that the P2Y1 receptor antagonist MRS2500 enhanced the spontaneous contraction amplitude, adding EM2 and β-FNA did not have any effect on MRS2500. Therefore, P2Y1 receptor expression could be associated with the occurrence of OIC in this rat model and the regulation of colonic motility by MOR may be related to the release of purine neurotransmitters such as ATP in the colonic nervous system. [ABSTRACT FROM AUTHOR]

The interplay of the enteric nervous system (ENS) and SIP syncytium (smooth muscle cells–interstitial cells of Cajal–PDGFRα+ cells) plays an important role in the regulation of gastrointestinal (GI) motility. This study aimed to investigate the dynamic regulatory mechanisms of the ENS-SIP system on colon motility during postnatal development. Colonic samples of postnatal 1-week-old (PW1), 3-week-old (PW3), and 5-week-old (PW5) mice were characterized by RNA sequencing, qPCR, Western blotting, isometric force recordings (IFR), and colonic motor complex (CMC) force measurements. Our study showed that the transcriptional expression of Pdgfrα, c-Kit, P2ry1, Nos1, and Slc18a3, and the protein expression of nNOS, c-Kit, and ANO1 significantly increased with age from PW1 to PW5. In PW1 and PW3 mice, colonic migrating movement was not fully developed. In PW5 mice, rhythmic CMCs were recorded, similar to the CMC pattern described previously in adult mice. The inhibition of nNOS revealed excitatory and non-propulsive responses which are normally suppressed due to ongoing nitrergic inhibition. During postnatal development, molecular data demonstrated the establishment and expansion of ICC and PDGFRα+ cells, along with nitrergic and cholinergic nerves and purinergic receptors. Our findings are important for understanding the role of the SIP syncytium in generating and establishing CMCs in postnatal, developing murine colons. [ABSTRACT FROM AUTHOR]

In this study we investigated the role of voltage dependent (KV), Ca2+-activated (KCa), and inward rectifier (Kir) potassium channels in the effects of hydrogen sulfide donor (H2S) sodium hydrosulfide (NaHS) on spontaneous contractile activity of rat jejunum. It was shown that NaHS dose-dependently (10–500 μM) reduced the tonus of the preparation, as well as the amplitude and frequency of spontaneous contractions of jejunum preparations under isometric conditions; the half-maximal effective concentration (EC50) of the inhibitory effect of NaHS on the amplitude of contractions was 165 μM. The blocker of KV channels 4-AP (200 μM) caused an increase in the amplitude of spontaneous contractions. NaHS (200 μM) decreased the amplitude and frequency of spontaneous activity of the preparation in the presence of 4-AP as well as in the control, and the effect on basal tonus was less pronounced. Blockers of large conductance KCa channels (BK), non-specific TEA (3 mM) and specific paxillin (1 μM), increased the amplitude of spontaneous contractions, while the depressing effect of NaHS was completely preserved. The selective blocker of small conductance KCa channels (SK) NS8593 (4 μM) did not affect the tonus of the preparation and the parameters of spontaneous contractions; it did not prevent the effect of NaHS. The activator of KATP channels diazoxide (100 μM) caused a decrease in the basal tonus of the preparation, as well as the amplitude and frequency of spontaneous contractions. Diazoxide and the KATP channel blocker glibenclamide (50 μM) prevented the effect of NaHS on the tonus of the preparation. BaCl2, the Kir channel blocker (30 μM), caused an increase in the amplitude of spontaneous contractions and prevented the development of the NaHS inhibitory effects on the frequency and amplitude of spontaneous contractions; the decrease in tonus was less pronounced than in the control. Thus, a decrease in the basal tonus of the rat jejunum preparation under the action of the H2S donor was associated with activation of Kir channels, including KATP channels, whereas the effect of H2S on amplitude and frequency was mediated by an increase in Ba2+-sensitive conductivity. [ABSTRACT FROM AUTHOR]

Lycium barbarum polysaccharides (LBPs) have been shown to exert an antiglycemic effect. Emerging evidence suggests that patients with hyperglycemia have a hypercontractility of duodenum, and targeting duodenal contraction of duodenum can be beneficial to glucose metabolism. However, it is unknown whether LBPs can improve glucose metabolism by regulating the hypercontractility of the duodenum. Our aim was to explore the effect of LBPs on duodenal contraction in prediabetic mice and also preliminarily investigate the mechanism. The results showed that LBPs improved glucose homeostasis by decreasing the duodenal amplitude of contraction rather than frequency. Moreover, LBPs ameliorated the gut microbiota composition and the levels of short-chain fatty acids, especially acetic acid, which might bind to the receptor on neurons to regulate the contraction of the duodenum. Acetic acid was hypothesized to play a key role in the above process. Then, acetic acid was determined to exert an antiglycemic effect as expected. In conclusion, LBPs may rely on acetic acid to regulate duodenal contraction to ameliorate glucose metabolism in prediabetic mice, which provides a new therapeutic strategy to treat dysglycemia. [ABSTRACT FROM AUTHOR]

Objectives: Reactive oxygen and nitrogen species may be produced during inflammation leading to the formation of NO, H 2 S or HNO. Enzymes such as iNOS, CSE and CBS might also be responsible for polysulfide production. Since these signalling molecules might have an impact on colonic motility, the aim of this study was to compare their effect on rat colonic slow phasic contractions (SPC)., Methods: Organ bath measurements with strips obtained from rat proximal colon were performed using the polysulfide Na 2 S 3 , sodium nitroprusside (NaNP), sodium hydrogen sulfide (NaHS), Angeli's salt as NO, H 2 S, and HNO donors, respectively. TTX (1 µM) was used to block neuronal activity., Results: All four molecules, concentration-dependently, inhibited the amplitude and frequency of SPC both in the circular and longitudinal muscle layer. The relative potency was NaNP>Angeli's salt>NaHS>Na 2 S 3 . The inhibitory response induced by NaNP (1 µM) and Angeli's salt (50 µM) was reversed by ODQ (10 µM) whereas the inhibitory effect of NaHS (1 mM) was reversed by apamin (1 µM) and glibenclamide (10 µM). Na 2 S 3 (1 mM) response was partially reversed by apamin (1 µM) and glibenclamide (10 µM). High concentrations of Na 2 S 3 caused an increase in tone. Low concentrations of NaHS or Na 2 S 3 did not potentiate NaNP responses., Conclusions: All signalling molecules inhibit SPC in both muscle layers. The effect is independent of neural activity and involves guanylyl cyclase (NO and HNO) and SKCa and KATP channels (NaHS or Na 2 S 3 ). Other pathways might also be involved in Na 2 S 3 responses. Accordingly, complementary mechanisms of inhibition might be attributable to these signalling molecules., (© 2021 Walter de Gruyter GmbH, Berlin/Boston.)

Background: The incidence of constipation increases among the elderly (>65 years), while abdominal pain decreases. Causes include changes in lifestyle (e.g., diet and reduced exercise), disease and medications affecting gastrointestinal functions. Degenerative changes may also occur within the colo-rectum. However, most evidence is from rodents, animals with relatively high rates of metabolism and accelerated aging, with considerable variation in time course. In humans, cellular and non-cellular changes in the aging intestine are poorly investigated., Purpose: To examine all available studies which reported the effects of aging on cellular and tissue functions of human isolated colon, noting the region studied, sex and age of tissue donors and study size. The focus on human colon reflects the ability to access full-thickness tissue over a wide age range, compared with other gastrointestinal regions. Details are important because of natural human variability. We found age-related changes within the muscle, in the enteric and nociceptor innervation, and in the submucosa. Some involve all regions of colon, but the ascending colon appears more vulnerable. Changes can be cell- and sublayer-dependent. Mechanisms are unclear but may include development of "senescent-like" and associated inflammaging, perhaps associated with increased mucosal permeability to harmful luminal contents. In summary, reduced nociceptor innervation can explain diminished abdominal pain among the elderly. Degenerative changes within the colon wall may have little impact on symptoms and colonic functions, because of high "functional reserve," but are likely to facilitate the development of constipation during age-related challenges (e.g., lifestyle, disease, and medications), now operating against a reduced functional reserve., (© 2024 The Author(s). Neurogastroenterology & Motility published by John Wiley & Sons Ltd.)

Background: Gastrointestinal smooth muscle relaxation is accomplished by activation of P2Y 1 receptors, therefore this receptor plays an important role in regulation of gut motility. Recently, BPTU was developed as a negative allosteric modulator of the P2Y 1 receptor. Accordingly, the aim of this study was to assess the effect of BPTU on purinergic neurotransmission in pig and human gastrointestinal tissues., Methods: Ca 2+ imaging in tSA201 cells that express the human P2Y 1 receptor, organ bath and microelectrodes in tissues were used to evaluate the effects of BPTU on purinergic responses., Key Results: BPTU concentration dependently (0.1 and 1 µmol L -1 ) inhibited the rise in intracellular Ca 2+ evoked by ADP in tSA201 cells. In the pig small intestine, 30 µmol L -1 BPTU reduced the fast inhibitory junction potential by 80%. Smooth muscle relaxations induced by electrical field stimulation were reduced both in pig ileum (EC 50  = 6 µmol L -1 ) and colon (EC 50  = 35 µmol L -1 ), but high concentrations of BPTU (up to 100 µmol L -1 ) had no effect on human colonic muscle. MRS2500 (1 µmol L -1 ) abolished all responses. Finally, 10 µmol L -1 ADPβS inhibited spontaneous motility and this was partially reversed by 30 µmol L -1 BPTU in pig, but not human colonic tissue and abolished by MRS2500 (1 µmol L -1 )., Conclusions & Inferences: BPTU blocks purinergic responses elicited via P2Y 1 receptors in cell cultures and in pig gastrointestinal tissue. However, the concentrations needed are higher in pig tissue compared to cell cultures and BPTU was ineffective in human colonic tissue., (© 2021 John Wiley & Sons Ltd.)

The synaptic event called the inhibitory junction potential (IJP) was arguably one of the more important discoveries made by Burnstock and arguably one of his finer legacies. The discovery of the IJP fundamentally changed how electromechanical coupling was visualised in gastrointestinal smooth muscle. Its discovery also set in motion the search for novel inhibitory neurotransmitters in the enteric nervous system, eventually leading to proposal that ATP or a related nucleotide was a major inhibitory transmitter. The subsequent development of purinergic signalling gave impetus to expanding the classification of surface receptors for extracellular ATP, not only in the GI tract but beyond, and then led to successive phases of medicinal chemistry as the P2 receptor field developed. Ultimately, the discovery of the IJP led to the successful cloning of the first P2Y receptor (chick P2Y1) and expansion of mammalian ATP receptors into two classes: metabotropic P2Y receptors (encompassing P2Y1, P2Y2, P2Y4, P2Y6, P2Y11-14 receptors) and ionotropic P2X receptors (encompassing homomeric P2X1-P2X7 receptors). Here, the causal relationship between the IJP and P2Y1 is explored, setting out the milestones reached and achievements made by Burnstock and his colleagues.

Reactive oxygen and nitrogen species may be produced during inflammation leading to the formation of NO, H2S or HNO. Enzymes such as iNOS, CSE and CBS might also be responsible for polysulfide production. Since these signalling molecules might have an impact on colonic motility, the aim of this study was to compare their effect on rat colonic slow phasic contractions (SPC). Organ bath measurements with strips obtained from rat proximal colon were performed using the polysulfide Na2S3, sodium nitroprusside (NaNP), sodium hydrogen sulfide (NaHS), Angeli's salt as NO, H2S, and HNO donors, respectively. TTX (1 µM) was used to block neuronal activity. All four molecules, concentration-dependently, inhibited the amplitude and frequency of SPC both in the circular and longitudinal muscle layer. The relative potency was NaNP>Angeli's salt>NaHS>Na2S3. The inhibitory response induced by NaNP (1 µM) and Angeli's salt (50 µM) was reversed by ODQ (10 µM) whereas the inhibitory effect of NaHS (1 mM) was reversed by apamin (1 µM) and glibenclamide (10 µM). Na2S3 (1 mM) response was partially reversed by apamin (1 µM) and glibenclamide (10 µM). High concentrations of Na2S3 caused an increase in tone. Low concentrations of NaHS or Na2S3 did not potentiate NaNP responses. All signalling molecules inhibit SPC in both muscle layers. The effect is independent of neural activity and involves guanylyl cyclase (NO and HNO) and SKCa and KATP channels (NaHS or Na2S3). Other pathways might also be involved in Na2S3 responses. Accordingly, complementary mechanisms of inhibition might be attributable to these signalling molecules. [ABSTRACT FROM AUTHOR]

This study aims to assess the barrier integrity and possible activation of enteric neural pathways associated with secretion and motility in the pig colon induced by an enterotoxigenic Escherichia coli (ETEC) challenge. 50 Danbred male piglets were used for this study. 16 were challenged with an oral dose of the ETEC strain F4+ 1.5 × 109 colony-forming unit. Colonic samples were studied 4- and 9-days post-challenge using both a muscle bath and Ussing chamber. Colonic mast cells were stained with methylene blue. In control animals, electrical field stimulation induced neurosecretory responses that were abolished by tetrodotoxin (10-6M) and reduced by the combination of atropine (10-4M) and α-chymotrypsin (10U/mL). Exogenous addition of carbachol, vasoactive intestinal peptide, forskolin, 5- HT, nicotine, and histamine produced epithelial Cl- secretion. At day 4 postchallenge, ETEC increased the colonic permeability. The basal electrogenic ion transport remained increased until day 9 post-challenge and was decreased by tetrodotoxin (10-6M), atropine (10-4M), hexamethonium (10-5M), and ondansetron (10-5M). In the muscle, electrical field stimulation produced frequency-dependent contractile responses that were abolished with tetrodotoxin (10-6M) and atropine (10-6M). Electrical field stimulation and carbachol responses were not altered in ETEC animals in comparison with control animals at day 9 post-challenge. An increase in mast cells, stained with methylene blue, was observed in the mucosa and submucosa but not in the muscle layer of ETEC-infected animals on day 9 post-challenge. ETEC increased the response of intrinsic secretory reflexes and produced an impairment of the colonic barrier that was restored on day 9 postchallenge but did not modify neuromuscular function. [ABSTRACT FROM AUTHOR]

Although gut seasonal plasticity has been extensively reported, studies on physiological flexibility, such as water-salt transportation and motility in reptiles, are limited. Therefore, this study investigated the intestinal histology and gene expression involved in water-salt transport (AQP1, AQP3, NCC, and NKCC2) and motility regulation (nNOS, CHRM2, and ADRB2) in desert-dwelling Eremias multiocellata during winter (hibernating period) and summer (active period). The results showed that mucosal thickness, the villus width and height, the enterocyte height of the small intestine, and the mucosal and submucosal thicknesses of the large intestine were greater in winter than in summer. However, submucosal thickness of the small intestine and muscularis thickness of the large intestine were lower in winter than in summer. Furthermore, AQP1, AQP3, NCC, nNOS, CHRM2, and ADRB2 expressions in the small intestine were higher in winter than in summer; AQP1, AQP3, and nNOS expressions in the large intestine were lower in winter than in summer, with the upregulation of NCC and CHRM2 expressions; no significant seasonal differences were found in intestinal NKCC2 expression. These results suggest that (i) intestinal water-salt transport activity is flexible during seasonal changes where AQP1, AQP3 and NCC play a vital role, (ii) the intestinal motilities are attenuated through the concerted regulation of nNOS, CHRM2, and ADRB2, and (iii) the physiological flexibility of the small and large intestine may be discrepant due to their functional differences. This study reveals the intestinal regulation and adaptation mechanisms in E. multiocellata in response to the hibernation season. [ABSTRACT FROM AUTHOR]

Introduction: Calcium-sensitive receptor (CaSR) is expressed in the enteric nervous system of gastrointestinal tract. However, its role in the regulation of gastrointestinal motility has not yet been fully elucidated. We aimed to investigate the effect of the CaSR agonist – R568 on gastric motility and its potential mechanism. Methods: In vivo, R568 was given by gavage to explore gastric emptying with or without capsaicin which specifically blocks the function of vagal afferents; neurotransmitters synthetized in the myenteric plexus of the gastric corpus and antrum were analysed by ELISA and immunofluorescence staining; gastric muscle strips contraction recording and intracellular single unit firing recording were used to study the effect of R568 on muscle strips and myenteric interstitial cells of Cajal (ICCs) ex vitro. Results: Gastric emptying was inhibited by R568 in Kunming male mice, and capsaicin weakened this effect. The expression of c-fos-positive neurons increased in the nucleus tractus solitarius when R568 was treated. R568 decreased the expression of cholinergic neurons and reduced the synthesis of acetylcholine. Conversely, R568 increased the expression of nitrogenic neurons and enhanced the synthesis of nitric oxide in the myenteric plexus. Ex vitro results showed that R568 inhibited the contraction of the gastric antral muscle strip and suppressed the spontaneous firing activity of pacemaker ICCs. Conclusion: Activation of the gastrointestinal CaSR inhibited gastric motility in vivo and ex vitro. Transmitting nutrient signals to the brain through the vagal afferent nerve, modulating the cholinergic and nitrergic system in the enteric nervous system, and inhibiting activity of pacemaker ICCs in the myenteric plexus are involved in the mechanism of CaSR in gastric motility suppression. [ABSTRACT FROM AUTHOR]

Muscle regeneration is indispensable for skeletal muscle health and daily life when injury, muscular disease, and aging occur. Among the muscle regeneration, muscle stem cells' (MuSCs) activation, proliferation, and differentiation play a key role in muscle regeneration. Purines bind to its specific receptors during muscle development, which transmit environmental stimuli and play a crucial role of modulator of muscle regeneration. Evidences proved P2R expression during development and regeneration of skeletal muscle, both in human and mouse. In contrast to P2XR, which have been extensively investigated in skeletal muscles, the knowledge of P2YR in this tissue is less comprehensive. This review summarized muscle regeneration via P2Y1R and P2Y2R and speculated that P2Y1R and P2Y2R might be potential molecular triggers for MuSCs' activation and proliferation via the p-ERK1/2 and PLC pathways, explored their cascade effects on skeletal muscle, and proposed P2Y1/2 receptors as potential pharmacological targets in muscle regeneration, to advance the purinergic signaling within muscle and provide promising strategies for alleviating muscular disease. [ABSTRACT FROM AUTHOR]