Model of rapid gastrointestinal transit in dogs: effects of muscarinic antagonists and a nitric oxide synthase inhibitor

Possible Regulation of P-Glycoprotein Function by Adrenergic Agonists II: Study with Isolated Rat Jejunal Sheets and Caco-2 Cell monolayers

To clarify the regulation of drug absorption by the enteric nervous system, we investigated how adrenergic agonists (adrenaline (ADR), clonidine (CLO), dobutamine (DOB)) and dibutyryl cAMP (DBcAMP) affected P-glycoprotein (P-gp) function by utilizing isolated rat jejunal sheets and Caco-2 cell monolayers. ADR and CLO significantly decreased the secretory transport (Papptotal) of rhodamine-123 and tended to decrease the transport via P-gp (PappP-gp) and passive transport (Papppassive). In contrast, DBcAMP significantly increased and DOB tended to increase Papptotal and both tended to increase PappP-gpand Papppassive. Changes in P-gp expression on brush border membrane by adrenergic agonists and DBcAMP were significantly correlated with PappP-gp, while P-gp expression was not changed in whole cell homogenates, suggesting that the trafficking of P-gp would be responsible for its functional changes. Papppassive was inversely correlated with transmucosal or transepithelial electrical resistance, indicating that adrenergic agonists affected the paracellular permeability. Adrenergic agonists also changed cAMP levels, which were significantly correlated with PappP-gp. Furthermore, protein kinase A (PKA) or PKC inhibitor significantly decreased PappP-gp in Caco-2 cell monolayers, suggesting that they would partly contribute to the changes in P-gp activity. In conclusion, adrenergic agonists regulated P-gp function and paracellular permeability, which would be caused via adrenoceptor stimulation.

Effect of Excessive Serotonin on Pharmacokinetics of Cephalexin after Oral Administration: Studies with Serotonin-Excessive Model Rats

PURPOSE

Serotonin (5-HT) is important for gastrointestinal functions, but its role in drug absorption remains to be clarified. Therefore, the pharmacokinetics and oral absorption of cephalexin (CEX) were examined under 5-HT-excessive condition to understand the role of 5-HT.

METHODS

5-HT-excessive rats were prepared by multiple intraperitoneal dosing of 5-HT and clorgyline, an inhibitor for 5-HT metabolism, and utilized to examine the pharmacokinetics, absorption behavior and the intestinal permeability for CEX.

RESULTS

Higher levels of 5-HT in brain, plasma and small intestines were recognized in 5-HT-excessive rats, where the oral bioavailability of CEX was significantly enhanced. The intestinal mucosal transport via passive diffusion of CEX was significantly increased, while its transport via PEPT1 was markedly decreased specifically in the jejunal segment, which was supported by the decrease in PEPT1 expression on brush border membrane (BBM) of intestinal epithelial cells. Since no change in antipyrine permeability and significant increase in FITC dextran-4 permeability were observed in 5-HT-excessive rats, the enhanced permeability for CEX would be attributed to the opening of tight junction, which was supported by the significant decrease in transmucosal electrical resistance. In 5-HT-excessive rats, furthermore, total body clearance of CEX tended to be larger and the decrease in PEPT2 expression on BBM in kidneys was suggested to be one of the reasons for it.

CONCLUSIONS

5-HT-excessive condition enhanced the oral bioavailability of CEX in rats, which would be attributed to the enhanced permeability across the intestinal mucosa via passive diffusion through the paracellular route even though the transport via PEPT1 was decreased.

Differential Actions of Muscarinic Receptor Subtypes in Gastric, Pancreatic, and Colon Cancer

Cancers arising from gastrointestinal epithelial cells are common, aggressive, and difficult to treat. Progress in this area resulted from recognizing that the biological behavior of these cancers is highly dependent on bioactive molecules released by neurocrine, paracrine, and autocrine mechanisms within the tumor microenvironment. For many decades after its discovery as a neurotransmitter, acetylcholine was thought to be synthesized and released uniquely from neurons and considered the sole physiological ligand for muscarinic receptor subtypes, which were believed to have similar or redundant actions. In the intervening years, we learned this former dogma is not tenable. (1) Acetylcholine is not produced and released only by neurons. The cellular machinery required to synthesize and release acetylcholine is present in immune, cancer, and other cells, as well as in lower organisms (e.g., bacteria) that inhabit the gut. (2) Acetylcholine is not the sole physiological activator of muscarinic receptors. For example, selected bile acids can modulate muscarinic receptor function. (3) Muscarinic receptor subtypes anticipated to have overlapping functions based on similar G protein coupling and downstream signaling may have unexpectedly diverse actions. Here, we review the relevant research findings supporting these conclusions and discuss how the complexity of muscarinic receptor biology impacts health and disease, focusing on their role in the initiation and progression of gastric, pancreatic, and colon cancers.

Overcoming Obstacles to Targeting Muscarinic Receptor Signaling in Colorectal Cancer

Despite great advances in our understanding of the pathobiology of colorectal cancer and the genetic and environmental factors that mitigate its onset and progression, a paucity of effective treatments persists. The five-year survival for advanced, stage IV disease remains substantially less than 20%. This review examines a relatively untapped reservoir of potential therapies to target muscarinic receptor expression, activation, and signaling in colorectal cancer. Most colorectal cancers overexpress M₃ muscarinic receptors (M₃R), and both in vitro and in vivo studies have shown that activating these receptors stimulates cellular programs that result in colon cancer growth, survival, and spread. In vivo studies using mouse models of intestinal neoplasia have shown that using either genetic or pharmacological approaches to block M₃R expression and activation, respectively, attenuates the development and progression of colon cancer. Moreover, both in vitro and in vivo studies have shown that blocking the activity of matrix metalloproteinases (MMPs) that are induced selectively by M₃R activation, i.e., MMP1 and MMP7, also impedes colon cancer growth and progression. Nonetheless, the widespread expression of muscarinic receptors and MMPs and their importance for many cellular functions raises important concerns about off-target effects and the safety of employing similar strategies in humans. As we highlight in this review, highly selective approaches can overcome these obstacles and permit clinicians to exploit the reliance of colon cancer cells on muscarinic receptors and their downstream signal transduction pathways for therapeutic purposes.

Anti-muscarinic drugs increase rectal compliance and exacerbate constipation in chronic spinal cord injury : Anti-muscarinic drug effect on neurogenic bowel

STUDY DESIGN

Prospective cohort study OBJECTIVES: We hypothesized that anti-muscarinic agents alter rectal compliance in SCI patients and that altered rectal compliance relates to bowel symptomatology. Our primary aim was to compare rectal compliance before and after the institution of anti-muscarinics (solifenacin and tolterodine) and an adrenoceptor agonist (mirabegron) in these patients. Additionally, we wanted to evaluate if anorectal manometry differed before and after use of anti-muscarinic agents.

SETTING

Tertiary neurogastroenterology clinic, London METHODS: Thirty-five patients with supraconal spinal cord injury (SCI) underwent anal manometry, assessment of rectoanal inhibitory reflex (RAIR) and rectal compliance before and after anti-muscarinic treatment (for overactive bladder) was started (mean follow-up 12 weeks). Patients were assessed identically, pre-and post-treatment (solifenacin n = 17, tolterodine n = 10, mirabegron n = 8). Doses used were as for non-SCI patients.

RESULTS

Resting, squeeze and cough pressures were unchanged after anti-muscarinic treatment. Rectal compliance was significantly raised after anti-muscarinic treatment (p = 0.001). The percent amplitude of maximal sphincter relaxation of the RAIR was decreased (p < 0.001) and excitation latency was increased (p = 0.006). There was no significant change in the duration of recovery of the RAIR. There was a significant increase of the Wexner Constipation Score (p = 0.001) but no change in the Wexner Incontinence Score. There was a significant correlation between change in rectal compliance and change in Wexner Constipation Score (p = 0.001). Thus, increasing compliance of the rectum is associated with worsening of constipation after anti-muscarinic therapy. However, there were no changes in anorectal manometry or rectal compliance in those who received mirabegron.

CONCLUSION

Anti-muscarinic therapy for overactive bladder increases compliance of the neurogenic rectum and alters anorectal reflex activity, with worsening of constipation.

Effect of retrograde colonic electrical stimulation on colonic transit and stress-induced visceral hypersensitivity in rats with irritable bowel syndrome

OBJECTIVE

To evaluate the effects of retrograde colonic electrical stimulation (RCES) with trains of short pulses and RCES with long pulses on colonic transit in irritable bowel syndrome (IBS) rats and to investigate whether stress-induced visceral hypersensitivity could be alleviated by RCES so as to find a valuable new approach for IBS treatment.

METHODS

A total of 48 male rats were randomly divided into model group and control group. Visceral hypersensitivity model was induced by a 6-day HIS protocol composed of two stressors, restraint stress for 40 min and forced swimming stress for 20 min. The extent of visceral hypersensitivity was quantified by electromyography and abdominal withdrawal reflex scores (AWRs) of colorectal distension (use a balloon) at different pressures. After the modeling, all rats were equipped with electrodes in descending colon for retrograde electrical stimulation and a PE tube for perfusing phenol red saline solution in the ileocecus. After recovering from surgery, RCES with long pulses, RCES with trains of short pulses, and sham RCES were performed in colonic serosa of rats for 40 min in six groups of 8 each, including three groups of visceral hypersensitivity rats and three groups of health rats. Colonic transit was assessed by calculating the output of phenol red from the anus every 10 min for 90 min. Finally, the extent of visceral hypersensitivity will be quantified again in model group.

RESULTS

After the 6-day HIS protocol, the HIS rats displayed an increased sensitivity to colorectal distention, compared to control group at different distention pressures (P < 0.01). CRES with trains of short pulses and long pulses significantly attenuated the hypersensitive responses to colorectal distention in the HIS rats compared with sham RCES group (P < 0.01). The effects of RCES on rats colon transmission: In the IBS rats, the colonic emptying were (77.4 ± 3.4)%, (74.8 ± 2.4)% and (64.2 ± 1.6)% in the sham RCES group, long pulses group and trains of short pulses group at 90 min; In healthy rats, The colonic emptying was (65.2 ± 3.5)%, (63.5 ± 4.0)% and (54.0 ± 2.5)% in the sham RCES group, long pulses group and trains of short pulses group at 90 min.

CONCLUSION

RCES with long pulses and RCES with trains of short pulses can significantly alleviate stress-induced visceral hypersensitivity. RCES with trains of short pulses has an inhibitory effect of colonic transit, both in visceral hypersensitivity rats and healthy rats.

Antinociceptive Activity of Ent-Dihydrotucumanoic Acid Isolated from Gymnosperma glutinosum Spreng Less

Preclinical Research The diterpene ent-dihydrotumanoic acid (DTA) was among the compounds isolated from Gymnosperma glutinosum (Spreng) Less (Asteraceae). There are no reports regarding the pharmacological effects of DTA. Cytotoxicity against cancer cells (1-250 µM), and the antibacterial (50-1400 µM) activity of DTA were evaluated using the MTT assay, and the minimum inhibitory concentration test, respectively. The antidiarrheal (1-100 mg/kg p.o.) and anti-inflammatory (2 mg/ear) effects of DTA were evaluated using castor oil and 12-O-tetradecanoylphorbol-13-acetate, respectively. The antinociceptive and sedative effects of DTA (1-100 mg/kg p.o.) were evaluated using two models of chemically-induced nociception, and the pentobarbital-induced sleeping time test, respectively. The antinociceptive mechanism of DTA was evaluated using the acetic acid writhing test with inhibitors related to pain processing pathways. The effects of DTA (10-100 mg/kg p.o.) on locomotor activity were evaluated using the rotarod test. DTA lacked cytotoxic activity (IC₅₀  > 100 µM) on cancer cells, possessed moderate antibacterial effects against B. subtillis (MIC= 175 µM), moderate antidiarrheal and anti-inflammatory effects, and minimal vasorelaxant effects. In the formalin test, DTA showed antinociceptive effects in both phases. In the acetic acid test, DTA showed antinociceptive activity (ED₅₀ = 50.2 ± 5.6 mg/kg) with potency similar to that of naproxen (NPX; ED₅₀ =33.7 ± 4.5 mg/kg) an effect blocked by naloxone implicating an opioid mechanism. DTA also exerted antidiarrheal activity and showed no sedative effects or changes in locomotor activity in mice. Drug Dev Res 78 : 340-348, 2017. © 2017 Wiley Periodicals, Inc.

Potential functional and pathological side effects related to off-target pharmacological activity

Most pharmaceutical companies test their discovery-stage proprietary molecules in a battery of in vitro pharmacology assays to try to determine off-target interactions. During all phases of drug discovery and development, various questions arise regarding potential side effects associated with such off-target pharmacological activity. Here we present a scientific literature curation effort undertaken to determine and summarize the most likely functional and pathological outcomes associated with interactions at 70 receptors, enzymes, ion channels and transporters with established links to adverse effects. To that end, the scientific literature was reviewed using an on-line database, and the most commonly reported effects were summarized in tabular format. The resultant table should serve as a practical guide for research scientists and clinical investigators for the prediction and interpretation of adverse side effects associated with molecules interacting with components of this screening battery.

β1/2 or M2/3 Receptors Are Required for Different Gastrointestinal Motility Responses Induced by Acupuncture at Heterotopic or Homotopic Acupoints

Acupuncture at homotopic acupoints or heterotopic acupoints is known to either inhibit or facilitate gastrointestinal motility, depending on the acupoint location. However, little effort has been made to investigate the roles of specific receptors (such as adrenergic and muscarinic acetylcholine receptors) in mediating the effects of acupuncture at heterotopic and homotopic acupoints. Different adrenergic receptor subtypes or cholinergic receptor subtypes are predominantly expressed in various sections of the gut, resulting in variations between the effects of acupuncture at heterotopic or homotopic acupoints on gastrointestinal motility. Here, we investigated the role of β₁/β₂ receptors and M₂/M₃ receptors in gastrointestinal motility regulated by acupuncture at ST37, a heterotopic acupoint, and ST25, a homotopic acupoint, by simultaneously recording intraluminal pressures in the distal colon and stomach or jejunum and examining fecal phenol red excretion in β_1/2 receptor-knockout mice and M_2/3 receptor-knockout mice. We found that knockout of the M_2/3 receptor significantly inhibited ST37 acupuncture-induced enhancement of gastric motility, jejunal motility, and colonic motility. Additionally, knocking out of the β_1/2 receptor significantly diminished the ST25 acupuncture-induced inhibition of gastric motility and jejunal motility without significantly altering the enhancement of colonic motility induced by acupuncture at ST25. Acupuncture at ST37 significantly accelerated gastrointestinal transition in β_1/2 receptor-knockout mice and their wild-type littermates. However, this acceleration of gastrointestinal transition was markedly diminished in M_2/3 receptor-knockout mice relative to their wild-type littermates. Acupuncture at ST25 significantly increased gastrointestinal transition in β_1/2 receptor-knockout mice and significantly decreased gastrointestinal transition in M_2/3 receptor-knockout mice without altering gastrointestinal transition in wild-type littermates of either. Our study revealed that M_2/3 receptors are required for the gastrointestinal motility associated with whole gastrointestinal transition enhanced by acupuncture at heterotopic acupoints, whereas β_1/2 receptors are required for the same gastrointestinal motility processes inhibited by acupuncture at homotopic acupoints. Therefore, our findings reveal important biological mechanisms underlying acupuncture treatment of disorders involving gastrointestinal motility dysfunction.

Gastrointestinal Safety Pharmacology in Drug Discovery and Development

Although the basic structure of the gastrointestinal tract (GIT) is similar across species, there are significant differences in the anatomy, physiology, and biochemistry between humans and laboratory animals, which should be taken into account when conducting a gastrointestinal (GI) assessment. Historically, the percentage of cases of drug attrition associated with GI-related adverse effects is small; however, this incidence has increased over the last few years. Drug-related GI effects are very diverse, usually functional in nature, and not limited to a single pharmacological class. The most common GI signs are nausea and vomiting, diarrhea, constipation, and gastric ulceration. Despite being generally not life-threatening, they can greatly affect patient compliance and quality of life. There is therefore a real need for improved and/or more extensive GI screening of candidate drugs in preclinical development, which may help to better predict clinical effects. Models to identify drug effects on GI function cover GI motility, nausea and emesis liability, secretory function (mainly gastric secretion), and absorption aspects. Both in vitro and in vivo assessments are described in this chapter. Drug-induced effects on GI function can be assessed in stand-alone safety pharmacology studies or as endpoints integrated into toxicology studies. In silico approaches are also being developed, such as the gut-on-a-chip model, but await further optimization and validation before routine use in drug development. GI injuries are still in their infancy with regard to biomarkers, probably due to their greater diversity. Nevertheless, several potential blood, stool, and breath biomarkers have been investigated. However, additional validation studies are necessary to assess the relevance of these biomarkers and their predictive value for GI injuries.

Evaluation of Acid Tolerance of Drugs Using Rats and Dogs Controlled for Gastric Acid Secretion

We attempted to establish animal models to evaluate the effects of drug degradation in the stomach on oral bioavailability. In addition, we assessed the utilization of animal studies in determining the need for enteric-coated formulations. In order to control the gastric pH in rats and dogs, appropriate dosing conditions were investigated using pentagastrin and rabeprazole, which stimulate and inhibit gastric acid secretion. Using animals controlled for gastric acid secretion, the area under curve (AUC) ratios (AUC with rabeprazole/AUC with pentagastrin) of all compounds unstable under acidic conditions were evaluated. The AUC ratios of omeprazole and erythromycin, which are administered orally to humans, as enteric-coated tablets, were greater than 1.9 in the rats and dogs controlled for gastric acid secretion. On the contrary, the AUC ratios of clarithromycin, azithromycin, and etoposide (commercially available as a standard immediate-release form) were less than 1.3 each. In conclusion, in vivo models using rats and dogs were optimized to evaluate the effects of gastric acid on the oral bioavailability of drugs, and demonstrated that in vivo models can lead to a better understanding of the oral bioavailability, with respect to the formulation development.

Colonic electrical stimulation: potential use for treatment of delayed colonic transit

AIM

Recently there has been an increased interest in using electrical stimulation to regulate gut motility generally and particularly for the treatment of slow-transit constipation. In this preliminary canine study, we aimed to study the effects of colonic electrical stimulation (CES) on colonic motility and transit.

METHOD

Nine dogs, each equipped with a pair of serosal colon electrodes and a proximal colon cannula were randomized to receive: (i) sham-CES, (ii) long pulse CES (20 cpm, 300 ms, 6 mA) or (iii) pulse train CES (40 Hz, 6 ms, 6 mA). Animals underwent assessment of colonic contractions via manometry, and of colonic transit by inserting 24 radiopaque markers via the colonic cannula and radiographically monitoring the markers at 2, 4 and 6 h following their insertion. The colonic transit was assessed by the geometric centre.

RESULTS

We found that, compared with sham-CES, pulse train CES, but not long pulse CES, significantly increased the overall colonic motility index twofold and accelerated the colonic transit by 104% at 2 h, by 60% at 4 h and by 31% at 6 h (P = 0.01, P = 0.02 and P = 0.03 vs sham-CES at 2, 4 and 6 h, respectively). The accelerating effect of pulse train CES was found to be mediated via both cholinergic and nitrergic pathways.

CONCLUSION

CES with pulse trains has prokinetic effects on colonic contractions and transit in healthy dogs, mediated via the cholinergic and nitrergic pathways. Further clinical studies are warranted to explore the therapeutic potential of CES for slow colonic transit constipation.

Heme deficiency of soluble guanylate cyclase induces gastroparesis

BACKGROUND

Soluble guanylate cyclase (sGC) is the principal target of nitric oxide (NO) to control gastrointestinal motility. The consequence on nitrergic signaling and gut motility of inducing a heme-free status of sGC, as induced by oxidative stress, was investigated.

METHODS

sGCβ1 (H105F) knock-in (apo-sGC) mice, which express heme-free sGC that has basal activity, but cannot be stimulated by NO, were generated.

KEY RESULTS

Diethylenetriamine NONOate did not increase sGC activity in gastrointestinal tissue of apo-sGC mice. Exogenous NO did not induce relaxation in fundic, jejunal and colonic strips, and pyloric rings of apo-sGC mice. The stomach was enlarged in apo-sGC mice with hypertrophy of the muscularis externa of the fundus and pylorus. In addition, gastric emptying and intestinal transit were delayed and whole-gut transit time was increased in the apo-sGC mice, while distal colonic transit time was maintained. The nitrergic relaxant responses to electrical field stimulation at 1-4 Hz were abolished in fundic and jejunal strips from apo-sGC mice, but in pyloric rings and colonic strips, only the response at 1 Hz was abolished, indicating the contribution of other transmitters than NO.

CONCLUSIONS & INFERENCES

The results indicate that the gastrointestinal consequences of switching from a native sGC to a heme-free sGC, which cannot be stimulated by NO, are most pronounced at the level of the stomach establishing a pivotal role of the activation of sGC by NO in normal gastric functioning. In addition, delayed intestinal transit was observed, indicating that nitrergic activation of sGC also plays a role in the lower gastrointestinal tract.

A review and additional post-hoc analyses of the incidence and impact of constipation observed in darifenacin clinical trials

Background

Constipation is a common side effect of antimuscarinic treatment for overactive bladder (OAB). This review evaluates the incidence and impact of constipation on the lives of patients with OAB being treated with darifenacin.

Methods

Constipation data from published Phase III and Phase IIIb/IV darifenacin studies were reviewed and analyzed. Over 4000 patients with OAB (aged 18–89 years; ≥80% female) enrolled in nine studies (three Phase III [data from these fixed-dose studies were pooled and provide the primary focus for this review], three Phase IIIb, and three Phase IV). The impact of constipation was assessed by discontinuations, use of concomitant laxatives, patient-reported perception of treatment, and a bowel habit questionnaire.

Results

In the pooled Phase III trials, 14.8% (50/337) of patients on darifenacin 7.5 mg/day and 21.3% (71/334) on 15 mg/day experienced constipation compared with 12.6% (28/223) and 6.2% (24/388) with tolterodine and placebo, respectively. In addition, a few patients discontinued treatment due to constipation (0.6% [2/337], 1.2% [4/334], 1.8% [4/223], and 0.3% [1/388] in the darifenacin 7.5 mg/day or 15 mg/day, tolterodine, and placebo groups, respectively), or required concomitant laxatives (3.3% [11/337], 6.6% [22/334], 7.2% [16/223], and 1.5% [6/388] in the darifenacin 7.5 mg/day or 15 mg/day, tolterodine, and placebo groups, respectively). Patient-reported perception of treatment quality was observed to be similar between patients who experienced constipation and those who did not. During the long-term extension study, a bowel habit questionnaire showed only small numerical changes over time in frequency of bowel movements, straining to empty bowels, or number of days with hard stools.

Conclusion

While constipation associated with darifenacin was reported in ≤21% of the patient population, it only led to concomitant laxative use in approximately one-third of these patients and a low incidence of treatment discontinuation. These data suggest that constipation did not impact patient perception of treatment quality.

Muscular vs. Neural Activation in Propulsion Induced by Electrical Stimulation in the Descending Colon of Rats

The present experiments were performed on rat colon to study neurogenic and myogenic elicited propulsion induced by 0.3 and 30 msec long current pulses. The colon segments were stimulated sequentially and randomly. The obtained contractions displaced the intraluminal content in individual propulsion steps. The propulsion steps differed in displacement onset latency, distance, and velocity; the latency decreased while the distance and velocity increased from the proximal to the distal colon segments when performing sequential stimulation; the propulsion steps differed in latency when stimulation was performed randomly; the latency in the first propulsion step was three times longer when using 0.3 vs. 30 msec long pulses. When inhibiting cholinergic transmission by atropine, the propulsion induced by 0.3 msec pulses was blocked, while partially inhibited when using 30 msec pulses. Inhibiting nitric oxide synthesis by N(G) -nitro-L-arginine methyl ester (L-NAME) blocked propulsion induced by both of the pulse durations. In conclusion, electrical stimulation induces propulsion when using both 0.3 and 30 msec long pulses; stimulation using 0.3 msec pulses activates neurons, whereas 30 msec pulses depolarize muscles; in the absence of nitrergic transmission, propulsion cannot be induced by electrical stimulation.

Antiulcerogenic activity of the essential oil of Hyptis martiusii Benth. (Lamiaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Hyptis martiusii (Lamiaceae), popularly known as "cidreira-do-mato" or "cidreira-brava", grows in abundance in the Northeast region of Brazil, where its leaves are traditionally used in folk medicine in the treatment of intestinal and stomach diseases. The aim of this study was to characterize the chemical constituents and to evaluate the anti-ulcerogenic activity of the essential oil of the leaves of Hyptis martiusii (EOHM) in in vivo models of experimental ulcers in rodents.

MATERIALS AND METHODS

EOHM was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS). Acute gastric ulcer was induced using absolute ethanol, HCl/ethanol and indomethacin. The volume, pH and total acidity of gastric secretion were determined by the pyloric ligature method and gastrointestinal motility using gastric emptying and intestinal transit.

RESULTS

Chemical analysis revealed the presence of 24 components that account for 92.13% of the essential oil of dried leaves, indicating the occurrence of mono and sesquiterpenes. Oral administration of EOHM (100, 200 and 400mg/kg) inhibited ethanol-, HCl/ethanol- and indomethacin-induced ulcers. In the case of pylorus ligature, the oil reduced the volume of gastric juices and total acidity, and increased gastric pH. The EOHM reduced the rate of gastric emptying with only the highest doses, but did not show any effect on intestinal transit at any of the three doses.

CONCLUSIONS

The results indicate that the essential oil of leaves of Hyptis martiusii has an antiulcerogenic activity, as evidenced by its significant inhibition of the formation of ulcers in various models. This effect could be related to an increase of gastric mucosal defensive factors. Further pharmacological studies are being undertaken in order to provide more precise elucidation of the action mechanism involved in this activity.

Comparison of selective M3 and nonselective muscarinic receptor antagonists on gastrointestinal transit and bowel habits in humans

Although in vitro studies show that muscarinic M(3) receptors primarily mediate the effects of acetylcholine on gastrointestinal contractility, the muscarinic receptor subtypes regulating gastrointestinal motor activity and transit in humans in vivo are unclear. We hypothesized that muscarinic M(3)-specific but not nonspecific receptor antagonists would delay gastrointestinal and colonic transit in humans. In this parallel-group study, gastric emptying, small intestinal transit, and colonic transit were assessed by scintigraphy on days 4-6 in 72 healthy subjects (49 women) who received placebo (n = 16), the M(3) antagonist darifenacin ER [7.5 mg (n = 20) or 15 mg daily (n = 17)], or the nonspecific antagonist tolterodine [4 mg daily (n = 19)] for 6 days. Bowel habits were recorded by daily diaries. Both doses of darifenacin substantially delayed [P < 0.01 vs. placebo (for both doses), P < 0.01 vs. tolterodine (for 15 mg)] small intestinal transit, i.e., colonic filling at 6 h (placebo [59.6 +/- 6.4%, mean +/- SE], 7.5 mg ER [34.4 +/- 6.1%], 15 mg ER [20.4 +/- 6.3%)]. Darifenacin (15 mg) also delayed (P < 0.01 vs. placebo and tolterodine) half-time for ascending colonic emptying [placebo (12.0 +/- 1.5 h), 7.5 mg (18.6 +/- 1.9 h), 15 mg (22.9 +/- 2.6 h)] and colonic transit (geometric center) at 24 [placebo (2.8 +/- 0.2), 7.5 mg (2.4 +/- 0.2), 15 mg (1.9 +/- 0.2)] but not 48 h. Darifenacin did not affect gastric emptying and tolterodine did not affect bowel habits or gastrointestinal transit. With muscarinic antagonists used at clinically approved doses, these findings demonstrate that muscarinic M(3) receptors regulate small intestinal and colonic transit in humans; colonic effects are more pronounced in the right than left colon. At doses that affect small and large intestinal transit, M(3) antagonists do not affect gastric emptying in humans. The efficacy of darifenacin in diarrhea-predominant irritable bowel syndrome should be evaluated.

Gastric emptying, small intestinal transit and fecal output in dystrophic (mdx) mice

Duchenne muscular dystrophy (DMD), which results from deficiency in dystrophin, a sarcolemma protein of skeletal, cardiac and smooth muscle, is characterized by progressive striated muscle degeneration, but various gastrointestinal clinical manifestations have been observed. The aim was to evaluate the possible impact of the dystrophin loss on the gastrointestinal propulsion in mdx mice (animal model for DMD). The gastric emptying of a carboxymethyl cellulose/phenol red dye non-nutrient meal was not significantly different at 20 min from gavaging between wild-type and mdx mice. The intestinal transit and the fecal output were significantly decreased in mdx versus normal animals, although the length of the intestine was similar in both animals. The present results provide evidence for motor intestinal alterations in mdx mice in in vivo conditions.

Small intestinal motility in soluble guanylate cyclase alpha1 knockout mice: (Jejunal phenotyping of sGCalpha1 knockout mice)

Nitric oxide (NO) activates soluble guanylate cyclase (sGC) to produce guanosine-3',5'-cyclic-monophosphate (cGMP). The aim of this study was to investigate the nitrergic regulation of jejunal motility in sGCalpha(1) knockout (KO) mice. Functional responses to nitrergic stimuli and cGMP levels in response to nitrergic stimuli were determined in circular muscle strips. Intestinal transit was determined. Nitrergic relaxations induced by electrical field stimulation and exogenous NO were almost abolished in male KO strips, but only minimally reduced and sensitive to ODQ in female KO strips. Basal cGMP levels were decreased in KO strips, but NO still induced an increase in cGMP levels. Transit was not attenuated in male nor female KO mice. In vitro, sGCalpha(1)beta(1) is the most important isoform in nitrergic relaxation of jejunum, but nitrergic relaxation can also occur via sGCalpha(2)beta(1) activation. The latter mechanism is more pronounced in female than in male KO mice. In vivo, no important implications on intestinal motility were observed in male and female KO mice.

Muscarinic receptors and ligands in cancer

Emerging evidence indicates that muscarinic receptors and ligands play key roles in regulating cellular proliferation and cancer progression. Both neuronal and nonneuronal acetylcholine production results in neurocrine, paracrine, and autocrine promotion of cell proliferation, apoptosis, migration, and other features critical for cancer cell survival and spread. The present review comprises a focused critical analysis of evidence supporting the role of muscarinic receptors and ligands in cancer. Criteria are proposed to validate the biological importance of muscarinic receptor expression, activation, and postreceptor signaling. Likewise, criteria are proposed to validate the role of nonneuronal acetylcholine production in cancer. Dissecting cellular mechanisms necessary for muscarinic receptor activation as well as those needed for acetylcholine production and release will identify multiple novel targets for cancer therapy.

Effect of tolterodine on gastrointestinal transit and bowel habits in healthy subjects

Clinical trials and observations suggest that constipation is an uncommon side effect of treating overactive bladder with the muscarinic receptor antagonist tolterodine. Because muscarinic antagonism inhibits gastrointestinal motor activity, we evaluated the effects of tolterodine on bowel habits, gastrointestinal and colonic transit in healthy subjects. In this double-blind study, 36 healthy subjects were randomized to tolterodine extended release (ER, 4 mg daily) or placebo for 6 days. Gastric emptying (GE), small bowel and colonic transit were assessed on days 4-6 by scintigraphy. Bowel habits were recorded by diaries. Tolterodine did not significantly affect half-time for GE (GE t(half)) [116 +/- 6 min (mean +/- SEM) for placebo vs 126 +/- 7 min for tolterodine], small bowel transit measured by colonic filling at 6 h (45 +/- 6% for placebo vs 36 +/- 6% for tolterodine) or the geometric center of colonic transit at 24 h (2.9 +/- 0.2 for placebo vs 2.6 +/- 0.3 for tolterodine). Subjects who received tolterodine had slightly fewer bowel movements (i.e. 1.34 +/- 0.1 stools per day for placebo vs 1.0 +/- 0.1 for tolterodine; P = 0.02 for treatment effect). Tolterodine did not significantly affect stool consistency or ease of defecation. At the therapeutic dose used to treat overactive bladder, tolterodine did not significantly affect gastrointestinal or colonic transit and had minor effects on bowel habits in healthy subjects. Further studies are necessary to elucidate whether these observations are explained by tolterodine effects at muscarinic receptors which stimulate and inhibit gastrointestinal motility.

Effect of a muscarinic M3 receptor agonist on gastric motility

Muscarinic M3 receptors exist in the gastrointestinal wall in humans and the muscarinic M3 agonist cevimeline hydrochloride (Evoxac) is a candidate therapeutic agent for the treatment of xerostomia in Sjögren's syndrome. However, M3 receptor agonists are not known to show efficacy for diseases associated with abnormal gastrointestinal motility. Herein the effects are reported of cevimeline on gastric motility in two patients with non-ulcer dyspepsia. The patients both received long-term proton pump inhibitor therapy for 6 months, but their symptoms persisted. Then cevimeline was administered orally for 8 weeks at 30 mg three times daily (90 mg/day) and their dyspepsia symptoms improved. Electrogastrography was performed to examine gastric motility before and after administration of the M3 agonist. The fasting or nocturnal wave rate was significantly increased after administration compared with before administration, but no significant postprandial changes were seen. No adverse effects of cevimeline were observed. This drug might be a candidate therapeutic agent for non-ulcer dyspepsia. Because its postprandial effects on gastrointestinal motility are unclear, a dose-finding clinical study should be performed in the future.

Muscarinic receptors: their distribution and function in body systems, and the implications for treating overactive bladder

1. The effectiveness of antimuscarinic agents in the treatment of the overactive bladder (OAB) syndrome is thought to arise through blockade of bladder muscarinic receptors located on detrusor smooth muscle cells, as well as on nondetrusor structures. 2. Muscarinic M3 receptors are primarily responsible for detrusor contraction. Limited evidence exists to suggest that M2 receptors may have a role in mediating indirect contractions and/or inhibition of detrusor relaxation. In addition, there is evidence that muscarinic receptors located in the urothelium/suburothelium and on afferent nerves may contribute to the pathophysiology of OAB. Blockade of these receptors may also contribute to the clinical efficacy of antimuscarinic agents. 3. Although the role of muscarinic receptors in the bladder, other than M3 receptors, remains unclear, their role in other body systems is becoming increasingly well established, with emerging evidence supporting a wide range of diverse functions. Blockade of these functions by muscarinic receptor antagonists can lead to similarly diverse adverse effects associated with antimuscarinic treatment, with the range of effects observed varying according to the different receptor subtypes affected. 4. This review explores the evolving understanding of muscarinic receptor functions throughout the body, with particular focus on the bladder, gastrointestinal tract, eye, heart, brain and salivary glands, and the implications for drugs used to treat OAB. The key factors that might determine the ideal antimuscarinic drug for treatment of OAB are also discussed. Further research is needed to show whether the M3 selective receptor antagonists have any advantage over less selective drugs, in leading to fewer adverse events.

Anal electrical stimulation with long pulses increases anal sphincter pressure in conscious dogs

PURPOSE

This study was designed to investigate the effects and mechanisms of anal electric stimulation with long pulses on anal sphincter pressure in conscious dogs.

METHODS

The study was performed after enema in nine healthy female hound dogs and composed of four randomized sessions ("dose"-response, anal electric stimulation only, or with atropine or phentolamine). The anal sphincter pressure was measured by using manometry and quantified by using the area under the contractile curve (mmHg/sec). Anal electric stimulation was performed via a pair of ring electrodes attached to a manometric catheter. The stimulation parameters in all but dose-response sessions included a frequency of 20 ppm, pulse width of 200 ms, and amplitude of 3 mA.

RESULTS

The anal sphincter pressure was 55.7 +/- 6 at baseline and increased by 37 percent to 76.4 +/- 6.5 during electric stimulation (P = 0.009). The increase of anal pressure during stimulation was positively correlated with the stimulation energy (r = 0.395; P < 0.01). The excitatory effect of electric stimulation was sustained for at least 20 minutes. Atropine did not alter anal pressure and did not abolish the excitatory effect of anal electric stimulation on the sphincter. Phentolamine reduced anal pressure from the baseline value of 50.5 +/- 4.7 to 33.1 +/- 5.4 (P = 0.019). The electric stimulation induced increase in anal pressure was dropped from 19 +/- 2.6 to 9.9 +/- 2.8 (P = 0.029) at the presence of phentolamine.

CONCLUSIONS

Anal electric stimulation with long pulses increases anal sphincter pressure in an energy-dependent manner. The alpha-adrenergic but not the cholinergic pathway at least partially mediates the excitatory effect of anal electric stimulation.

Colon emptying induced by sequential electrical stimulation in rats

Electrical stimulation could be used to induce colon emptying. The present experiments were performed to establish a stimulation pattern to optimize the stimulation parameters and to test neural involvement in propulsion induced by electrical stimulation. Colon segments were sequentially stimulated using rectangular pulses. The resulting propulsive activity displaced intraluminal content in consecutive propulsion steps. The propulsion steps differed in displacement latency, distance, and velocity along the stimulated colon. Increasing the pulse duration or amplitude resulted in a decrease of the latency. Increasing the stimulation amplitude doubled the displacement distance. The frequencies tested in the present study did not affect propulsion. Inhibition of cholinergic and nitrergic pathways inhibited propulsion. Electrical stimulation can induce colonic propulsion. Motor differences are present along the descending colon. The most suitable combination of pulse parameters regarding colon stimulation is 0.3 ms, 5 mA, 10 Hz. Neural circuits are involved in propulsion when using these values.

Modulatory role of lotus-seed milk fermented product on gastrointestinal motility and absorption in mice

AIM: To explore the modulatory role of lotus-seed milk fermented product (LMFP) on gastrointestinal motility and absorption function in mice.

METHODS: Mice were divided into groups by the ran-domized complete weight-block design and treated with distilled water, different drugs and different conc-entrations of LMFP accordingly. L-arginine was intrape-ritoneally injected into the mice to observe the state of gastric emptying, small intestinal propelling, and the nitric oxide (NO) concentration in gastric homogenate; Compound Diphenoxylate was used to establish the mouse model of constipation, and the time, weight, quantity and the water content of black feces were measured; Reserpine was subcutaneously injected into the mice to calculate the small intestinal propellant rate and the content of uric xylose.

RESULTS: The delay of gastric emptying was positive-ly correlated with the NO concentration (r = 0.475, P = 0.001). As compared with those in the l-arginine model group, the volumns of phenol red leaving in the stomach of 250, 500 mL/L LMFP groups and Dom-peridone group were significantly decreased (22.78±6.95%, 27.12±5.73%, 22.82±5.63% vs 34.76±9.15%, P<0.05) and the NO concentration of gastric homogenate in 250 mL/L LMFP group and Domperido-ne group were lower (26.13±4.95 µmol/g pro, 26.33±4.06 µmol/g pro vs 38.33±9.82 µmol/g pro, P<0.05). The volumns of phenol red leaving in the distal 3 small intestinal segments of 500 mL/L, 750 mL/L LMFP group and Domperidone group were markedly higher, and the volumns leaving in the distal 4 small intestinal segments in 750 mL/L LMFP group and Domperidone group were also notably increased (P<0.05), in comparison with those in the model group. The time of black feces excreted was reduced and the water content of the feces were significantly increased in 250, 500, 750 mL/L LMFP groups than those in the model group (133.63±18.28, 113.25±26.25, 141.75±25.95 min vs 175.50±24.04 min, P<0.05). The weights of black feces in 250 and 500 mL/L LMFP groups were increased than those in the model group (0.68±0.16, 0.82±0.23 g vs 0.37±0.13 g, P<0.05). As compared with that in the reserpine model group, the propellant rate of powdered charcoal in pure LMFP (1 000 mL/L) group was lower (79.93±14.52% vs 97.64±5.68%, P = 0.002), while the uric xylose level in 500 mL/L, pure LMFP group were higher (10.54±2.48, 12.24±2.15 mg vs 7.86±1.71 mg, P<0.05).

CONCLUSION: LMFP regulate can regulate the gastr-ointestinal motility in a bidirectional way, and it can ease the constipation and improve the absorption function of small intestine.

Endogenous nitric oxide modulates small intestinal nutrient transit and activity in healthy adult humans

OBJECTIVE

Nitric oxide (NO) mechanisms have been shown to modulate fasting small intestinal motility in humans, but a role in the regulation of human postprandial small intestinal motility has not been assessed. The aim of this study was to evaluate the effect of the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) on the regulation of small intestinal nutrient transit and postprandial small intestinal motility in healthy humans.

MATERIAL AND METHODS

Seven healthy male volunteers (18-27 years) underwent antroduodenal manometry recordings for 4 h on 2 occasions after intraduodenal instillation of a 500 KJ [120 Kcal] test meal. The meal was administered 15 min after the commencement of a 60-min intravenous infusion of L-NMMA (4 mg kg-1 h-1) or saline (0.9%). Studies were separated, performed in randomized order and >3 days apart. The frequency and amplitude of duodenal pressure waves together with time to return of fasting motility (phase III) was determined. On each day, small intestinal transit was measured using a lactulose breath test.

RESULTS

The test meal interrupted fasting small intestinal motility in all subjects. The time to recurrence of fasting motility following its postprandial disruption was similar (L-NMMA versus saline 1.6+/-0.2 h versus 1.9+/-0.1 h; p>0.05). Duodenocaecal transit was delayed by infusion of L-NMMA compared with saline (L-NMMA versus saline 92.1+/-3.9 min versus 66.4+/-6.4 min; p<0.005). Infusion of L-NMMA significantly increased the frequency (L-NMMA versus saline 50.4+/-6.6 versus 34.8+/-5.5 waves per 30 min; p<0.05) and amplitude (L-NMMA versus saline 20.4+/-1.5 versus 15.5+/-1.1 mmHg; p<0.01) of duodenal pressure waves.

CONCLUSIONS

These data suggest that endogenous NO may play a role in the regulation of small intestinal nutrient transit by regulating small intestinal motility in healthy individuals.

Effect of sodium fluoride on gastric emptying and intestinal transit in mice

Fluoride, a well-recognised harmful substance, is easily absorbed by the gastrointestinal mucosa. It is therefore conceivable that any alteration of the gastrointestinal motility can affect the rate of absorption of fluoride and leads to aggravation of its toxic effects. The effects of fluoride on gastric emptying and intestinal transit were studied in the mouse using a carboxymethyl cellulose (CMC) solution as a non-nutrient meal. The participation of the cholinergic and nitrergic systems in these effects was also evaluated. Oral gavage of 5 mM NaF had no significant effect on gastric emptying and intestinal transit of the CMC meal, whereas a decrease of gastric emptying (-33%, P<0.05) and an increase in intestinal transit (+20.7%, P<0.05) were observed with 20 mM NaF. Atropine injection induced a significant decrease of gastric emptying. Combined treatment of atropine with 20 mM NaF brought about a further, but not significant decrease in gastric emptying. N-G-nitro-L-arginine-methyl ester (L-NAME) treatment with or without oral administration of NaF decreased gastric emptying. Atropine treatment significantly depressed intestinal transit from 56.5% to 37.7% in the absence of NaF and from 70.1% to 42.8% in its presence. In contrast, L-NAME administration either alone or with fluoride increased intestinal transit (P<0.05). The present results suggest that fluoride alter gastrointestinal motility, an effect that may partly involve the cholinergic pathway.

Propulsive activity induced by sequential electrical stimulation in the descending colon of the pig

This work was performed to study electrically induced contractions in the descending colon of pigs. Contractions were monitored using impedance planimetry and manometry. The luminal pressure, cross-sectional area (CSA), latency and velocity of CSA decrease were compared when using 3 ms, 9, 12, 15 or 30 mA pulses at 10 Hz for 10 s, and 15 mA, 0.03, 0.3 or 3 ms pulses at 10 Hz for 10 s. Stimulation was performed prior and after the application of N(G)-nitro-L-arginine methyl ester (L-NAME) and atropine. In the untreated colon, contraction was always of an 'off' type. A current increase from 9 to 30 mA increased the pressure. An increase of pulse duration from 0.03 to 3 ms shortened the latency, accelerated contraction and increased pressure. By sequential stimulation, contractions were coordinated to propel semi-fluid and solid luminal contents. L-NAME increased the magnitude of CSA decrease. Atropine induced inhibitory effects on contractions elicited by 3 ms pulses and abolished contractions induced by 0.03 and 0.3 ms pulses.

IN CONCLUSION

(i) electrical stimulation evokes'off' colon contractions, which can be coordinated to result in propulsion; (ii) the best combination for current and pulse duration to induce propulsive contractions is 15 mA and 3 ms; (iii) nitrergic and cholinergic pathways mediate responses to electrical stimulation.

A pilot study of the effects of sildenafil on stool characteristics, colon transit, anal sphincter function, and rectal sensation in healthy men

Nitric oxide is an important mediator of gut smooth muscle relaxation and visceral sensation. Sildenafil results in stimulation of the nitric oxide-cyclic GMP pathway. We sought to determine the effects of daily sildenafil administration on colorectal function. Over a 4-week period, sildenafil was administered during weeks 2 and 3. Stool frequency and consistency were assessed daily. Anorectal manometry, rectal sensation, and colon transit testing were performed at the end of weeks 1 and 3. Ten healthy men were studied. No significant differences in segmental or total colon transit time were noted; however, significant changes in stool frequency and trends toward decreased stool consistency were noted during sildenafil use. A trend toward reduced resting anal sphincter pressure was seen after sildenafil. Rectal volumes to first sensation and desire to defecate were significantly increased after sildenafil on test day 2 only. Additionally, volumes to desire to defecate and maximal tolerable volume were significantly increased before sildenafil on test day 2 compared to before sildenafil on test day 1. We conclude that daily administration of sildenafil is well tolerated and results in alterations in colorectal function.

Regulation of Drug Absorption from Small Intestine by Enteric Nervous System I: a Poorly Absorbable Drug Via Passive Diffusion

To investigate the regulation of drug absorption from the small intestine by the enteric nervous system (ENS), the vascular-luminal perfusion study and the in-vitro transport study were performed by employing phenol red as a poorly absorbable model compound. The effect of ENS on the intestinal absorption of phenol red was examined by adding epinephrine, an adrenergic agonist, or bethanechol, a cholinergic agonist into the vascular perfusate in the vascular-luminal perfused rat small-intestine preparation. The viability of the perfused intestine was checked by the recovery of the vascular perfusate, net water flux and absorbability of antipyrine, a well absorbable drug, and it was confirmed that the function of the perfused small-intestine preparation was maintained for at least 1 hr. The effect of epinephrine or bethanechol on the function of the small intestine was recognized as the increase in net water absorption, or the promotion of the water secretion, respectively. These phenomena are ones that are typically observed when adrenergic or cholinergic neuron is stimulated. Then, we investigated the small-intestinal absorption of phenol red in the vascular-luminal perfused preparation. Absorption clearance (CL(abs)) of phenol red was gradually increasing during the perfusion for 1 hr, but the 20-min vascular perfusion with the perfusate containing epinephrine made CL(abs) of phenol red constant and significantly lower than those for control study. Furthermore, after the perfusate was changed with the one without any agonist, again, CL(abs) of phenol red started to increase. These results clearly indicate that the stimulation of adrenergic neuron by epinephrine leads to the decrease in the small-intestinal absorption of phenol red. On the other hand, the vascular perfusion of bethanechol resulted in the increase in CL(abs) of phenol red comparing to the control study. Removing bethanechol from the vascular perfusate decreased CL(abs) of phenol red, again. The in-vitro transport study using the isolated jejunum sheet also showed that epinephrine in the serosal solution significantly decreased the transport of phenol red, which can be ascribed to the paracellular pathway tightened by the action of epinephrine because of the increase in transmucosal electrical resistance (TER). On the other hand, although the effect of bethanechol on both the transport of phenol red and TER was not statistically significant, the transport of phenol red tended to increase and the values of TER are smaller than those of control study.

Effect of extrinsic denervation on muscarinic neurotransmission in the canine ileocolonic region

To explore the hypothesis that denervation hypersensitivity increases ileocolonic motor activity after extrinsic denervation, we compared muscarinic neurotransmission in canine ileocolonic loops that were isolated and either extrinsically innervated or extrinsically denervated. We recorded ileal, ileocolonic sphincter (ICS) and colonic pressures, and colonic tone, compliance and relaxation during ileal distention. Muscarinic effects were probed by neostigmine, and minimally effective doses of muscarinic receptor antagonists. Denervation augmented ileal, ICS and colonic contractile activity; colonic high-amplitude propagating contractions (HAPCs) were also augmented; colonic relaxation during ileal distention was abolished. Neostigmine induced HAPCs in both loop preparations. Pirenzipine (M1 antagonist) reduced ileal contractile activity in all loops and reduced colonic relaxation during ileal distention in innervated loops. Pirenzipine also reduced colonic tone and colonic HAPCs, more in denervated loops. Darifenacin (M3 antagonist) reduced ileocolonic contractile activity and tone more than did AF-DX 116 (M2 antagonist) in all loops. Cholinergic receptor subtypes modulate different facets of ileocolonic motor activity in the canine ileocolonic region. Increased sensitivity at M1 muscarinic receptors may partly account for the effects of extrinsic denervation.