Contractile effects of 5-hydroxytryptamine (5-HT) in the equine jejunum circular muscle: functional and immunohistochemical identification of a 5-HT1A-like receptor

Cannabinoid and Cannabinoid-Related Receptors in the Myenteric Plexus of the Porcine Ileum

An important piece of evidence has shown that molecules acting on cannabinoid receptors influence gastrointestinal motility and induce beneficial effects on gastrointestinal inflammation and visceral pain. The aim of this investigation was to immunohistochemically localize the distribution of canonical cannabinoid receptor type 1 (CB1R) and type 2 (CB2R) and the cannabinoid-related receptors transient potential vanilloid receptor 1 (TRPV1), transient potential ankyrin receptor 1 (TRPA1), and serotonin receptor 5-HT1a (5-HT1aR) in the myenteric plexus (MP) of pig ileum. CB1R, TRPV1, TRPA1, and 5-HT1aR were expressed, with different intensities in the cytoplasm of MP neurons. For each receptor, the proportions of the immunoreactive neurons were evaluated using the anti-HuC/HuD antibody. These receptors were also localized on nerve fibers (CB1R, TRPA1), smooth muscle cells of tunica muscularis (CB1R, 5-HT1aR), and endothelial cells of blood vessels (TRPV1, TRPA1, 5-HT1aR). The nerve varicosities were also found to be immunoreactive for both TRPV1 and 5-HT1aR. No immunoreactivity was documented for CB2R. Cannabinoid and cannabinoid-related receptors herein investigated showed a wide distribution in the enteric neurons and nerve fibers of the pig MP. These results could provide an anatomical basis for additional research, supporting the therapeutic use of cannabinoid receptor agonists in relieving motility disorders in porcine enteropathies.

Advances in understanding relationship between 5-hydroxytryptamine and its receptors and intestinal dysmotility in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common clinical functional gastrointestinal disease, which seriously affects the quality of life of patients. The pathogenesis of this disorder is unclear and may be related to the changes of visceral sensitivity, gastrointestinal motility, and the function of the brain-gut axis. 5-hydroxytryptamine (5-HT) is an important neurotransmitter, which exhibits a variety of biological effects including gastrointestinal secretion and motility regulation by binding to its receptors. The changes in the synthesis and release of 5-HT and in the expression and function of corresponding receptors are all involved in the pathophysiological process of IBS. In this paper, we will review the role of 5-HT and its receptors in intestinal dysmotility in IBS.

Effect of Da-Huang on intestinal motility failure in rats with severe acute pancreatitis

AIM: To investigate the effect of Da-Huang on intestinal motility failure in rats with severe acute pancreatitis (SAP) and the potential mechanism involved．

METHODS: Fifty-four SD rats were randomly divided into s sham operation (SO) group, a SAP group and a Da-Huang treatment group, with 18 rats in each group. Gastrointestinal motility disturbance in rats with SAP was induced by retrograde injection of sodium taurocholate (0.1 mL/100 g) into the bitiopancreatic duct. Before modeling, the rats in the treatment group received 10% Da-Huang solution (2 mL/100 g), and the rats in other two groups received 0.9% NaCl solution. The rats were sacrificed at 3, 6 and 12 h (6 rats at each time), and blood samples were taken for detecting the levels of amylase, lipase and the contents of 5-hydroxytryptamine (5-HT) by enzyme-linked immunosorbent assay. The jejunum, terminal ileum and sigmoid colon tissues 10 cm apart from the trans-ligament were collected at 6 h for examining the expressions of 5-HT₁ receptor (5-HT₁R) and 5-HT₂ receptor (5-HT₂R).

RESULTS: The levels of serum amylase, lipase and 5-HT at three time points in the SAP group (amylase: 9807 IU/L ± 698 IU/L, 15442 IU/L ± 952 IU/L, 18231 IU/L ± 869 IU/L; lipase: 94 IU/L ± 23 IU/L, 257 IU/L ± 99 IU/L, 306 IU/L ± 107 IU/L; 5-HT: 1192 ng/mL ± 142 ng/mL, 1437 ng/mL ± 114 ng/mL, 1646 ng/mL ± 163 ng/mL) and treatment group (amylase: 2238 IU/L ± 298 IU/L, 2313 IU/L ± 302 IU/L, 2289 IU/L ± 323 IU/L; lipase: 62 IU/L ± 16 IU/L, 71 IU/L ± 17 IU/L, 69 IU/L ± 15 IU/L; 5-HT: 794 ng/mL ± 86 ng/mL, 814 ng/mL ± 83 ng/mL, 798 ng/mL ± 81 ng/mL) were significantly higher than those in the SO group (amylase: 1853 IU/L ± 272 IU/L, 1959 IU/L ± 269 IU/L, 1897 IU/L ± 293 IU/L; lipase: 46 IU/L ± 9 IU/L, 54 IU/L ± 11, 52 IU/L ± 14 IU/L; 5-HT: 699 ng/mL ± 64 ng/mL, 721 ng/mL ± 76 ng/mL, 705 ng/mL ± 72 ng/mL)(all P < 0.01), but they were lower in the treatment group than in the SAP group at each time point (all P < 0.01). The expression of 5-HT1R and 5-HT₂R proteins was significantly decreased in the jejunum, terminal ileum and sigmoid colon in the SAP group compared with the SO group (all P < 0.05). The areas of 5-HT₁R and 5-HT₂R positive cells in the jejunum, terminal ileum and sigmoid colon in the SAP group (5-HT₁R positive cells: 4.58 × 10⁴ μm² ± 0.56 × 10⁴ μm²、4.64 × 10⁴ μm² ± 0.63 × 10⁴ μm²、4.79 × 10⁴ μm² ± 0.56 × 10⁴ μm², 5-HT₂R positive cells: 4.89 × 10⁴ μm² ± 0.61 × 10⁴ μm², 4.76 × 10⁴ μm² ± 0.51 × 10⁴ μm², 5.03 × 10⁴ μm² ± 0.73 × 10⁴ μm²) were significantly decreased compared with the SO group (5-HT₁R positive cells: 5.63 × 10⁴ μm² ± 0.82 × 10⁴ μm², 5.94 × 10⁴ μm² ± 0.91 × 10⁴ μm², 6.37 × 10⁴ μm² ± 0.87 × 10⁴ μm², 5-HT₂R positive cells: 6.02 × 10⁴ μm² ± 0.78 × 10⁴ μm², 5.98 × 10⁴ μm² ± 0.66 ×10⁴ μm², 6.49× 10⁴ μm² ± 0.85 × 10⁴ μm²). The expression of 5-HT₁R protein and the areas of 5-HT₁ positive cells in the jejunum, terminal ileum and sigmoid colon in the treatment group (5.57 × 10⁴ μm² ± 0.83 × 10⁴ μm², 5.82 × 10⁴ μm² ± 0.74 × 10⁴ μm², 6.02 × 10⁴ μm² ± 0.81 × 10⁴ μm²), but not the areas of 5-HT₂ positive cells (4.94 × 10⁴ μm² ± 0.59 × 10⁴ μm², 4.81 × 10⁴ μm² ± 0.63 × 10⁴ μm², 5.16 × 10⁴ μm² ± 0.79 × 10⁴ μm²), were increased in comparison with SAP group (all P < 0.05)．

CONCLUSION: The level of 5-HT is significantly increased in SAP, but its receptors (5-HT₁R and 5-HT₂R) are decreased, which may induce intestinal motility failure. Da-Huang may improve enteric dynamic failure by activating 5-HT₁R or increasing the expression of 5-HT₁R, and may be a choice for treatment of SAP with intestinal motility failure．

Serotonin receptors in rat jugular vein: presence and involvement in the contraction

Serotonin (5-hydroxytryptamine; 5-HT) is released during platelet aggregation, a phenomenon commonly observed in blood clot formation and venous diseases. Once released, 5-HT can interact with its receptors in the peripheral vasculature to modify vascular tone. The goal of this study was to perform a detailed pharmacological characterization of the 5-HT receptors involved in the contractile response of the rat jugular vein (RJV) using recently developed drugs with greater selectivity toward 5-HT receptor subtypes. We hypothesized that, as for other blood vessels, the 5-HT(1B/1D) and 5-HT(2B) receptor subtypes mediate contraction in RJV alongside the 5-HT(2A) receptor subtype. Endothelium-intact RJV rings were set up in an isolated organ bath for isometric tension recordings, and contractile concentration-effect curves were obtained for 13 distinct serotonergic receptor agonists. Surprisingly, the 5-HT(1A) and the mixed 5-HT(1A/1B) receptor agonists (+/-)-2-dipropyl-amino-8-hydroxyl-1,2,3,4-tetrahydronapthalene (8-OH-DPAT) and 5-methoxy-3 (1,2,3,6-tetrahydropyridin-4-yl) (1H indole) (RU24969) caused contractions that were antagonized by the 5-HT(1A) receptor antagonist [O-methyl-3H]-N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide (WAY100135). The contractile curve to 5-HT was shifted to the right by WAY100135, 3-[2-[4-(4-fluoro benzoyl)-piperidin-1-yl]ethyl]-1H-quinazoline-2,4-dione (ketanserin; 5-HT(2A/C) receptor antagonist), and 1-(2-chloro-3,4-dimethoxybenzyl)-6-methyl-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole hydrochloride (LY266097; 5-HT(2B) receptor antagonist). Ketanserin also caused rightward shifts of the contractile curves to 8-OH-DPAT, RU24969, and the 5-HT(2B) receptor agonist (alpha-methyl-5-(2-thienylmethoxy)-1H-indole-3-ethanamine) (BW723C86). Agonists for 5-HT(1B/1D/1F), 5-HT(3), 5-HT(6), and 5-HT(7) receptors were inactive. In real-time polymerase chain reaction experiments that have never been performed in this tissue previously, we observed mRNA expression for the 5-HT(2A), 5-HT(2B), and 5-HT(7) receptors, whereas no significant mRNA expression was found for 5-HT(1A), 5-HT(1B), and 5-HT(1D) receptors. These results support the 5-HT(2A) receptor as the main subtype targeted by 5-HT to contract the RJV.