Role of tachykinin receptors in the modulation of colonic peristaltic activity in mice

Tachykinins are important mediators of neuroneuronal and neuromuscular transmission in the gastrointestinal tract, however their contribution to colonic peristalsis in mice remains unclear. Therefore, our aim was to characterise the functional role of tachykinins in mediating peristalsis by evaluating the effect of selective tachykinin NK(1), NK(2) and NK(3) receptor agonists and antagonists on in vitro colonic peristaltic activity in mice. Using a modified Trendelenburg set-up, gradual distension of proximal and distal colonic segments evoked rhythmic, aborally migrating contractions. Peristaltic activity was assessed by quantifying the amplitude and interval of the corresponding pressure waves. Stimulation of NK(1) receptors showed regional differences as both the pressure amplitude and interval were enhanced in the distal colon without affecting peristalsis proximally. Blockade of NK(1) receptors reduced the peristaltic pressure amplitude in the proximal and distal colon while the interval was not significantly altered. NK(2) receptor stimulation resulted in a modest enhancement of the amplitude in proximal and distal segments and a slightly prolonged interval distally. Blockade of NK(2) receptors reduced the peristaltic pressure amplitude and interval in the distal colon. NK(3) receptor stimulation significantly augmented the amplitude in both segments and prolonged the interval distally. However, NK(3) receptor blockade had no effect on peristaltic activity. In conclusion, tachykinins contribute to colonic peristalsis in mice by acting mainly on NK(1) and NK(2) receptors and their effects show a proximal-to-distal gradient. NK(3) receptors might play a role in conditions of excess tachykinin release but appear not to be involved under the conditions of the present study.

Therapeutic advances in functional gastrointestinal disease: irritable bowel syndrome

Reported prevalence rates of irritable bowel syndrome (IBS) are between 8% to 20% in the US general population with an average medical expenditure of US$1.35 billion direct and US$205 million indirect costs. Current pathophysiologic theories are based on abnormalities of both the brain and gut, thus setting a new stage for current and future therapeutic approaches. There are numerous treatment options in IBS acting centrally and peripherally by influencing motility and visceral sensitivity. Clinical evidence is variable; however, newer emerging treatments are being evaluated using better-designed clinical trials. Accurate assessment of IBS drug efficacy is still hampered by heterogeneity of the IBS population. Novel methods such as pharmacogenomics or brain imaging may be helpful in the future to better understand and characterize IBS patient subtypes, and this in turn will lead to more specific and efficient therapeutic options. Patient subpopulation measurement of side effects is also a clinical challenge and further understanding could improve treatment efficacy enhancing the patient compliance.

Differential role of tachykinin NK3 receptors on cholinergic excitatory neurotransmission in the mouse stomach and small intestine

BACKGROUND AND PURPOSE

Tachykinin NK(3) receptors are widely expressed in the mouse gastrointestinal tract but their functional role in enteric neuromuscular transmission remains unstudied in this species. We investigated the involvement of NK(3) receptors in cholinergic neurotransmission in the mouse stomach and small intestine.

EXPERIMENTAL APPROACH

Muscle strips of the mouse gastric fundus and ileum were mounted in organ baths for tension recordings. Effects of NK(3) agonists and antagonists were studied on contractions to EFS of enteric nerves and to carbachol.

KEY RESULTS

EFS induced frequency-dependent tetrodotoxin-sensitive contractions, which were abolished by atropine. The cholinergic contractions to EFS in the stomach were enhanced by the NK(3) antagonist SR142801, but not affected by the NK(3) agonist senktide or neurokinin B. The cholinergic contractions to EFS in the small intestine were not affected by SR142801, but dose-dependently inhibited by senktide and neurokinin B. This inhibitory effect was prevented by SR142801 but not by hexamethonium. SR142801, senktide or neurokinin B did not induce any response per se in the stomach and small intestine and did not affect contractions to carbachol.

CONCLUSIONS AND IMPLICATIONS

NK(3) receptors modulate cholinergic neurotransmission differently in the mouse stomach and small intestine. Blockade of NK(3) receptors enhanced cholinergic transmission in the stomach but not in the intestine. Activation of NK(3) receptors inhibited cholinergic transmission in the small intestine but not in the stomach. This indicates a physiological role for NK(3) receptors in mouse stomach contractility and a pathophysiological role in mouse intestinal contractility.

Immunomodulatory properties of substance P: the gastrointestinal system as a model. Ann N Y Acad Sci. 2006;1088:23-40. [PMID: 17192554 DOI: 10.1196/annals.1366.024] [Cited by in Crossref: 91] Communication between nerves and immune and inflammatory cells of the small and large intestine plays a major role in the modulation of several intestinal functions, including intestinal motility, ion transport, and mucosal permeability. Neuroimmune interactions at intestinal sites have been associated with the pathophysiology of infectious and enterotoxin-mediated diarrhea and intestinal inflammation, including inflammatory bowel disease (IBD). During the past 20 years the neuropeptide substance P (SP) has been identified as an important mediator in the development and progress of intestinal inflammation by binding to its high-affinity neurokinin-1 receptor (NK-1R). This peptide, released from enteric nerves, sensory neurons, and inflammatory cells of the lamina propria during intestinal inflammation, participates in gut inflammation by interacting, directly or indirectly, with NK-1R expressed on nerves, epithelial cells, and immune and inflammatory cells, such as mast cells, macrophages, and T cells. SP-dependent activation of these cells leads to the release of cytokines and chemokines as well as other neuropeptides that modulate diarrhea, inflammation, and motility associated with the pathophysiology of several intestinal disease states. The recent development of specific nonpeptide NK-1R antagonists and NK-1R-deficient mice helped us understand the functional importance of the SP-NK-1R system in mediating intestinal neuroimmune interactions and to identify the particular cells and signaling pathways involved in this response. This review summarizes our understanding on the immunomodulatory properties of SP and its receptor in the intestinal tract with particular focus on their involvement in intestinal physiology as well as in the pathophysiology of several intestinal disease states at the in vivo and cell signaling level

Communication between nerves and immune and inflammatory cells of the small and large intestine plays a major role in the modulation of several intestinal functions, including intestinal motility, ion transport, and mucosal permeability. Neuroimmune interactions at intestinal sites have been associated with the pathophysiology of infectious and enterotoxin-mediated diarrhea and intestinal inflammation, including inflammatory bowel disease (IBD). During the past 20 years the neuropeptide substance P (SP) has been identified as an important mediator in the development and progress of intestinal inflammation by binding to its high-affinity neurokinin-1 receptor (NK-1R). This peptide, released from enteric nerves, sensory neurons, and inflammatory cells of the lamina propria during intestinal inflammation, participates in gut inflammation by interacting, directly or indirectly, with NK-1R expressed on nerves, epithelial cells, and immune and inflammatory cells, such as mast cells, macrophages, and T cells. SP-dependent activation of these cells leads to the release of cytokines and chemokines as well as other neuropeptides that modulate diarrhea, inflammation, and motility associated with the pathophysiology of several intestinal disease states. The recent development of specific nonpeptide NK-1R antagonists and NK-1R-deficient mice helped us understand the functional importance of the SP-NK-1R system in mediating intestinal neuroimmune interactions and to identify the particular cells and signaling pathways involved in this response. This review summarizes our understanding on the immunomodulatory properties of SP and its receptor in the intestinal tract with particular focus on their involvement in intestinal physiology as well as in the pathophysiology of several intestinal disease states at the in vivo and cell signaling level.

Alterations of gastrin, somatostatin, G and D cells in rat gastric ulcer

AIM: To investigate the alterations of gastrin secretion of G cells, somatostatin secretion of D cells and the change of G (D) cells in rat gastric ulcer.

METHODS: An acetic-acid-induced rat gastric ulcer model was established. The histological structure of rat antral mucosa and the ultrastructure of mucosal cells were observed generally, through microscope and through electron microscope. The content of gastrin or somatostatin in serum or in antral tissue was measured via radioimmunoassay. The shape, number, size of G (D) cells, and the ratio of number and size of G/D cells were viewed and analyzed with immunohistochemical technique and image analysis system. G (D) cells and the secretive gastrin (somatostatin) granules in G (D) cells were observed through immunoel-ectron microscope and analyzed in image analysis system.

RESULTS: G (D) cells and the secretive gastrin (somatostatin) granules in G (D) cells were observed through immunoelectron microscope successfully. In gastric ulcer rat the secretive gastrin in G cells increased, the secretive somatostatin in D cells declined, the number of G cells increases and the size of G cells declined; both the number and the size of D cells declined, both the ratio of the number and size of G/D cells increased, both the content of gastrin in serum and in antral tissue increased, and both the content of somatostatin in serum and in antral tissue declined.

CONCLUSION: The rat gastric ulcer induces the changes of G cells and D cells, secretive gastrin in G cells and secretive somatostatin in D cells, as well as the contents of gastrin and somatostatin.

Effects of two methods of reconstruction of digestive tract after total gastrectomy on gastrointestinal motility in rats

AIM: To compare the effects of Roux-en-Y and jejunum interposition reconstruction procedures after total gastrectomy on intestinal motility.

METHODS: Fifty male Sprague-Dawley rats were randomly divided into 5 groups: the control group (C), the laparotomy group (L), the jejunal transection group (JT) where the jejunum was transected 10 cm distal from the Treitz ligament and anastomosed, the Roux-en-Y group (RY) and the jejunal interposition group (JI) after total gastrectomy. To evaluate intestinal transit, the animals were given 0.1 ml Evans Blue solution through an orogastric tube. The rats were executed by CO₂ inhalation 30 minutes later and the intestinal transmit was determined as the distance between the site of esophageojejunal anastomosis and the most distal site of small intestine colored with blue.

RESULTS: One month after operation, the body weight of rats among JI and RY were almost identical (274.6 ± 9.5 vs 270.4 ± 10.6, P > 0.05), but were significantly lighter than those of JT and L group. Four months after the operation, the body weight in the JI group increased compared to the preoperative level (345.2 ± 15.7 g vs 299.5 ± 8.3 g, P < 0.01). However, the body weight of RY group decreased compared to preoperative (255.1 ± 11.3 g vs 295.0 ± 12.0 g, P < 0.01). The difference was more significant at six months postoperative. Small bowel transmit time in RY was slower than that in JI group and C group (P < 0.01).

CONCLUSION: Changes of body weight and intestinal motility in JI group are less influenced than in RY group.