Properties of acetylcholine-induced relaxation of smooth muscle isolated from the proximal colon of the guinea-pig

Interaction between the Renin-Angiotensin System and Enteric Neurotransmission Contributes to Colonic Dysmotility in the TNBS-Induced Model of Colitis

Angiotensin II (Ang II) regulates colon contraction, acting not only directly on smooth muscle but also indirectly, interfering with myenteric neuromodulation mediated by the activation of AT₁ /AT₂ receptors. In this article, we aimed to explore which mediators and cells were involved in Ang II-mediated colonic contraction in the TNBS-induced rat model of colitis. The contractile responses to Ang II were evaluated in distinct regions of the colon of control animals or animals with colitis in the absence and presence of different antagonists/inhibitors. Endogenous levels of Ang II in the colon were assessed by ELISA and the number of AT₁/AT₂ receptors by qPCR. Ang II caused AT₁ receptor-mediated colonic contraction that was markedly decreased along the colons of TNBS-induced rats, consistent with reduced AT₁ mRNA expression. However, the effect mediated by Ang II is much more intricate, involving (in addition to smooth muscle cells and nerve terminals) ICC and EGC, which communicate by releasing ACh and NO in a complex mechanism that changes colitis, unveiling new therapeutic targets.

Acotiamide improves stress-induced impaired gastric accommodation

BACKGROUND

Gastric accommodation is a reflex reaction related to gastric reservoir function. Psychological stress, such as anxiety, inhibits gastric accommodation in humans. Acotiamide enhances the effect of acetylcholine in the enteric nervous system, enhances gastric contractility, and accelerates delayed gastric emptying. However, the effect of acotiamide on stress-induced impaired gastric accommodation remains unclear. Therefore, we examined the effect of acotiamide on gastric accommodation and stress-induced impaired gastric accommodation using a conscious guinea pig model.

METHODS

A polyethylene bag was inserted through the distal region of the gastric body into the proximal stomach of 5-week-old male Hartley guinea pigs. Gastric accommodation was evaluated by measuring the intrabag pressure in the proximal stomach after oral administration of a liquid meal. In the stress model, animals were subjected to water-avoidance stress. Acotiamide (Z-338) or nizatidine was administered subcutaneously. Fecal output was determined as the number of fecal pellets.

KEY RESULTS

Administration of the liquid meal significantly decreased intrabag pressure, indicating induction of gastric accommodation. Acotiamide treatment prolonged liquid meal-induced gastric accommodation and significantly increased the number of fecal pellets compared to controls. Water-avoidance stress significantly inhibited liquid meal-induced gastric accommodation. Pretreatment with acotiamide significantly improved stress-induced impaired gastric accommodation. The number of fecal pellets in the acotiamide group increased significantly compared to controls. Acotiamide, but not nizatidine, significantly decreased gastric emptying.

CONCLUSIONS & INFERENCES

Acotiamide prolongs gastric accommodation and improves stress-induced impaired gastric accommodation, indicating a potential role for acotiamide in the treatment of functional dyspepsia through its effects on gastric accommodation reactions.

Acute colonic pseudoobstruction

Acute colonic pseudoobstruction (ACPO), often referred to as Ogilvie syndrome, is a clinical entity characterized by severe colonic distension (adult acute megacolon) in the absence of mechanical obstruction. It can result in abdominal ischemia and perforation if left untreated. This article discusses the epidemiology and current pathophysiologic theories of ACPO as well as the clinical presentation and diagnostic modalities utilized to identify the disease. In addition, this article describes the current treatment options for ACPO, which range from conservative medical therapy, therapeutic endoscopy, to subtotal colectomy.

Further evidence of endogenous hydrogen sulphide as a mediator of relaxation in human and rat bladder

We investigated the expression of hydrogen sulphide (H2S) in human and rat lower urinary tract (including bladder, prostate and urethra) tissues, and we sought to determine whether H2S induces relaxation of human and Sprague-Dawley (SD) rat bladder strips. Human normal lower urinary tract tissue was obtained for the evaluation of endogenous H2S productivity using a sulphide-sensitive electrode and for the analysis of the expression levels of all three synthases of endogenous H2S, cystathionine β-synthase (CBS), cystathionine γ lyase (CSE) and 3-mercaptopyruvate sulphur transferase (MPST, as known as 3-MST) by Western blot assay. CBS, CSE and MPST were located in human sample slides by immunohistochemistry. Human and male adult SD rat bladder strips were tested for H2S function with a transducer and recorded. All experiments were repeated six times. The endogenous H2S productivity and the H2S synthases had various distributions in the human and rat lower urinary tract tissues and were located in both epithelial and stromal sections. L-cysteine (L-Cys, a substrate of CBS, CSE and MPST) elicited relaxation in a dose-dependent manner on human bladder strips pre-contracted by acetylcholine chloride. This effect could be diminished by the ATP-sensitive potassium ion (KATP) channel blocker glibenclamide (GLB), the CSE inhibitor DL-propargylglycine (PPG) and the CBS inhibitor hydroxylamine (HA). H2S and its three synthases were present in the human and rat lower urinary tract tissues and relaxed human and rat bladder strips, which implied that endogenous H2S might play a role in physiological function and pathological disorders of the lower urinary tract symptoms (LUTS) or overactive bladder (OAB).

Ultrastructural characterization of interstitial cells of Cajal associated with the submucosal plexus in the proximal colon of the guinea pig

Interstitial cells of Cajal (ICC) associated with the submucosal (submucous) plexus (ICC-SP) in the proximal colon of the guinea pig were studied by immunohistochemistry and electron microscopy. Whole-mount stretch preparations with c-Kit immunohistochemistry revealed that a number of ICC-SP constituted a dense cellular network around the submucosal plexus. Some of these ICC-SP were observed in the vicinity of the muscularis mucosae in sections immunostained for c-Kit and α-smooth muscle actin. Ultrastructural observation demonstrated, for the first time, that ICC-SP of the proximal colon of the guinea pig retained typical ultrastructural characteristics of ICC repeatedly reported in association with the tunica muscularis of the gastrointestinal tract: a basal lamina, caveolae, many mitochondria, abundant intermediate filaments and the formation of gap junctions with the same type of cells. The most remarkable ultrastructural finding was the presence of thick bundles composed of the processes of ICC-SP connected to each other via large gap junctions. These ICC-SP might be involved in the main mucosal functions of the proximal colon of the guinea pig, namely the transportation of water and electrolytes, possibly via their involvement in the spontaneous contractions of the muscularis mucosae.