Involvement of nitrergic neurons in colonic motility in a rat model of ulcerative colitis

BACKGROUND The mechanisms underlying gastrointestinal(GI)dysmotility with ulcerative colitis(UC)have not been fully elucidated.The enteric nervous system(ENS)plays an essential role in the GI motility.As a vital neurotransmitter in the ENS,the gas neurotransmitter nitric oxide(NO)may impact the colonic motility.In this study,dextran sulfate sodium(DSS)-induced UC rat model was used for investigating the effects of NO by examining the effects of rate-limiting enzyme nitric oxide synthase(NOS)changes on the colonic motility as well as the role of the ENS in the colonic motility during UC.AIM To reveal the relationship between the effects of NOS expression changes in NOS-containing nitrergic neurons and the colonic motility in a rat UC model.METHODS Male rats(n=8/each group)were randomly divided into a control(CG),a UC group(EG1),a UC+thrombin derived polypeptide 508 trifluoroacetic acid(TP508TFA;an NOS agonist)group(EG2),and a UC+NG-monomethyl-L-arginine monoacetate(L-NMMA;an NOS inhibitor)group(EG3).UC was induced by administering 5.5%DSS in drinking water without any other treatment(EG1),while the EG2 and EG3 were gavaged with TP508 TFA and L-NMMA,respectively.The disease activity index(DAI)and histological assessment were recorded for each group,whereas the changes in the proportion of colonic nitrergic neurons were counted using immunofluorescence histochemical staining,Western blot,and enzyme linked immunosorbent assay,respectively.In addition,the contractile tension changes in the circular and longitudinal muscles of the rat colon were investigated in vitro using an organ bath system.RESULTS The proportion of NOS-positive neurons within the colonic myenteric plexus(MP),the relative expression of NOS,and the NOS concentration in serum and colonic tissues were significantly elevated in EG1,EG2,and EG3 compared with CG rats.In UC rats,stimulation with agonists and inhibitors led to variable degrees of increase or decrease for each indicator in the EG2 and EG3.When the rats in EGs developed UC,the mean contraction tension of the colonic smooth muscle detected in vitro was higher in the EG1,EG2,and EG3 than in the CG group.Compared with the EG1,the contraction amplitude and mean contraction tension of the circular and longitudinal muscles of the colon in the EG2 and EG3 were enhanced and attenuated,respectively.Thus,during UC,regulation of the expression of NOS within the MP improved the intestinal motility,thereby favoring the recovery of intestinal functions.CONCLUSION In UC rats,an increased number of nitrergic neurons in the colonic MP leads to the attenuation of colonic motor function.To intervene NOS activity might modulate the function of nitrergic neurons in the colonic MP and prevent colonic motor dysfunction.These results might provide clues for a novel approach to alleviate diarrhea symptoms of UC patients.

Extended Fasting Durations Delayed Gastric Emptying and Colonic Motility in Normal Male Rats

Background: Previous studies on fasting and gastrointestinal motility were reported with information lacking concerning prolonged continuous fasting and gastrointestinal motility. This study investigated the effect of prolonged fasting duration on gastrointestinal motility. Methods: Forty-five (45) male Wistar rats, with body weights between 180 - 200 g were used. They were randomly assigned into three (3) groups. Group1: control (rats fasted for 18 h—common duration of fasting for motility studies), groups 2 and 3 fasted for 48 and 72 h respectively. Five (5) rats per experiment and per group were considered. Blood glucose was determined by glucose oxidase method, gastric emptying was assessed by hydrated carbohydrate meal, intestinal motility by charcoal meal, and colonic motility was assessed using bead test. Data were reported in Mean ± SEM and analyzed with one-way ANOVA. Differences in results were considered significant at p ≤ 0.05. Results: There was no significant change in the blood glucose level (mmol/L) of rats in the 48 h group (2.94 ± 0.35) and 72 h group (3.20 ± 0.32) as compared with the control (3.62 ± 0.19). There was a significant decrease in the rate of gastric emptying (g) in the 72 h group (0.20 ± 0.08) compared with the control (0.64 ± 0.16). The intestinal transit (cm) in the 48 h group (67.54 ± 6.15) and 72 h group (72.10 ± 7.60) increased significantly when compared with the control (42.14 ± 3.14). There was a significant decrease in the colonic motility time (Sec.) in the 48 h group (2707 ± 864.1) and 72 h group (6363 ± 968.1) when compared with the control (263.8 ± 64.26). Conclusion: Extended fasting durations decrease the rate of gastric emptying and colonic motility. It suggests that extended fasting durations could be beneficial in intestinal spasms or where the gut is required to relax.

THE COLONIC TRANSIT TEST IN THE ASSESSMENT OF CHRONIC CONSTIPATION

In order to assess colonic motility of chronic constipation, colonic transit test was carried out in 34 patients with chronic constipation and in 20 healthy subjects. 20 radiopaque markers are ingested at 8 am before the day test, and plain abdominal films were obtained at 24 h, 48 h and 72 h. The normal value of colonic transit test was 16(80%), or more markers passed after 72 h. By means of transit time study, 34 constipated patients were classified into 2 groups: 12 normal transit patients and 22 slow transit patients. There was no difference in colonic transit time between normal transit patients and controls (P>005). Patients with slow transit had more markers left in right colon, left colon and rectosigmoid colon at 48 h (P<001, respectively) and 72 h (P<001, respectively). According to the transit index, 22 slow transit patients were divided into 3 types: 10 cases colonic stasis, 8 cases outlet obstruction and 4 cases colorectal stasis. The study suggests that chronic constipated patients have abnormalbilities of colonic transit.