[Effects of trimebutine on colonic propulsion in mice]

Mechanisms that underlie μ-opioid receptor agonist-induced constipation: differential involvement of μ-opioid receptor sites and responsible regions

Reducing the side effects of pain treatment is one of the most important strategies for improving the quality of life of cancer patients. However, little is known about the mechanisms that underlie these side effects, especially constipation induced by opioid receptor agonists; i.e., do they involve naloxonazine-sensitive versus -insensitive sites or central-versus-peripheral μ-opioid receptors? The present study was designed to investigate the mechanisms of μ-opioid receptor agonist-induced constipation (i.e., the inhibition of gastrointestinal transit and colonic expulsion) that are antagonized by the peripherally restricted opioid receptor antagonist naloxone methiodide and naloxonazine in mice. Naloxonazine attenuated the fentanyl-induced inhibition of gastrointestinal transit more potently than the inhibition induced by morphine or oxycodone. Naloxone methiodide suppressed the oxycodone-induced inhibition of gastrointestinal transit more potently than the inhibition induced by morphine, indicating that μ-opioid receptor agonists induce the inhibition of gastrointestinal transit through different mechanisms. Furthermore, we found that the route of administration (intracerebroventricular, intrathecally, and/or intraperitoneally) of naloxone methiodide differentially influenced the suppressive effect on the inhibition of colorectal transit induced by morphine, oxycodone, and fentanyl. These results suggest that morphine, oxycodone, and fentanyl induce constipation through different mechanisms (naloxonazine-sensitive versus naloxonazine-insensitive sites and central versus peripheral opioid receptors), and these findings may help us to understand the characteristics of the constipation induced by each μ-opioid receptor agonist and improve the quality of life by reducing constipation in patients being treated for pain.

Prokineticin-2, motilin, ghrelin and metoclopramide: prokinetic utility in mouse stomach and colon

The ability of agents described as gastrointestinal prokinetics (prokineticin-2, [Nle(13)]-motilin, ghrelin), to modulate nerve-mediated contractions of mouse isolated stomach and colon was determined and compared with the prokinetic and 5-HT(4) receptor agonist, metoclopramide. Circular muscle preparations were electrically field-stimulated (EFS) to evoke cholinergically mediated contractions. Metoclopramide 10-100 microM facilitated EFS-evoked contractions in forestomach (n = 5-11, P < 0.05); 1 mM inhibited. Metoclopramide had no effects in colon, apart from 100 microM which reduced contractions. Prokineticin-2 0.001 nM-0.1 microM (n = 3-7) or [Nle(13)]-motilin 0.1 nM-1 microM (n = 4-8) had no effects in forestomach or colon. Ghrelin 0.01-1 microM facilitated EFS-evoked contractions in forestomach (n = 5-7, P < 0.05) but not in colon (n = 5-8). We conclude that ghrelin and metoclopramide facilitate excitatory nerve activity because neither affected inhibitory responses to EFS in the presence of atropine, or contractions to carbachol. Further, prokineticin-2 and [Nle(13)]-motilin are unlikely to exert gastric prokinetic activity in this species, the inactivity of the latter being consistent with an absence of the motilin receptor in rodents.

Effect of Dai-kenchu-to (Da-Jian-Zhong-Tang) on the delayed intestinal propulsion induced by chlorpromazine in mice

This study was conducted to evaluate the effect of Dai-kenchu-to on chlorpromazine-induced hypoperistalsis in mice. Oral administration of Dai-kenchu-to (30-300 mg/kg) dose-dependently improved small intestinal and distal colonic propulsion decreased by chlorpromazine (3 mg/kg, p.o.). Although the improvement of small intestinal propulsion due to Dai-kenchu-to was partially inhibited by atropine (1 mg/kg, s.c.), this action was completely inhibited by the concomitant administration of lorglumide (10 mg/kg, i.p.), a CCKA receptor antagonist. The distal colonic propulsion-improving effect of Dai-kenchu-to was abolished by atropine (1 mg/kg, s.c.). When the effects of the respective components of Dai-kenchu-to were evaluated, oral administration of Zanthoxylum Fruit improved both delayed small intestinal and distal colonic propulsion caused by chlorpromazine. On the other hand, Malt Sugar was effective against only delayed small intestinal propulsion. The action of Zanthoxylum Fruit was completely inhibited by atropine (1 mg/kg, s.c.), and the effect of Malt Sugar was inhibited by lorglumide (10 mg/kg, i.p.). These results demonstrated that Dai-kenchu-to improves chlorpromazine-induced hypoperistalsis via cholinergic systems and that Zanthoxylum Fruit is the main contributor to this action of Dai-kenchu-to. In addition, endogenous CCK due to Malt Sugar may also contribute to this effect of Dai-kenchu-to.

Differential actions of peripheral corticotropin-releasing factor (CRF), urocortin II, and urocortin III on gastric emptying and colonic transit in mice: role of CRF receptor subtypes 1 and 2

Peripheral CRF inhibits gastric emptying and stimulates colonic motor function in rats. We investigated the role of CRF(1) and CRF(2) receptors in i.p. CRF-induced alterations of gut transit in conscious mice using selective CRF(1) and CRF(2) ligands injected i.p. Gastric emptying 2 h after ingestion of a solid chow meal and colonic transit (time to expel a bead inserted into the distal colon) were determined simultaneously. Rat/human (r/h)CRF, which has CRF(1) > CRF(2) binding affinity, decreased distal colonic transit time at lower doses (6-12 microg/kg) than those inhibiting gastric emptying (20-60 microg/kg). Ovine CRF, a preferential CRF(1) receptor agonist (6-60 microg/kg), reduced significantly the colonic transit time without altering gastric emptying, whereas the selective CRF(2) receptor agonists mouse urocortin II (20-60 microg/kg) and urocortin III (120 microg/kg) inhibited significantly gastric emptying without modifying colonic transit. The CRF(1)/CRF(2) receptor antagonist, astressin (30-120 microg/kg), dose dependently prevented r/hCRF (20 microg/kg)-induced inhibition of gastric emptying and reduction of colonic transit time. The selective CRF(1) receptor antagonists, NBI-27914 (C(18)H(20)Cl(4)N(4)C(7)H(8)O(3)S) and CP-154,526 (butyl-[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo[2,3-d]pyrimidin-4-yl]ethylamine) (5-30 mg/kg), dose dependently blocked r/hCRF action on the colon without influencing the gastric response, whereas the CRF(2) receptor antagonist, antisauvagine-30 (30-100 microg/kg), dose dependently abolished r/hCRF-induced delayed gastric emptying and had no effect on colonic response. These data show that i.p. r/hCRF-induced opposite actions on upper and lower gut transit in conscious mice are mediated by different CRF receptor subtypes: the activation of CRF(1) receptors stimulates colonic propulsive activity, whereas activation of CRF(2) receptors inhibits gastric emptying.

Stimulating effects of KW-5092, a novel gastroprokinetic agent, on the gastric emptying, small intestinal propulsion and colonic propulsion in rats

KW-5092 ((1-[2-[[[5-(piperidinomethyl)-2-furanyl]methyl]amino]ethyl]- 2-imidazolidinylidene) propanedinitrile fumarate) is a novel gastroprokinetic agent with acetylcholinesterase (AChE) inhibitory activity and acetylcholine (ACh) release facilitatory activity. The present study examined the effects of KW-5092 on gastrointestinal (GI) propulsion in rats. KW-5092 at 1 to 30 mg/kg, p.o. dose-dependently enhanced the gastric emptying, small intestinal propulsion and the proximal and distal colonic propulsion. Metoclopramide, a dopamine D2-receptor antagonist with ACh release facilitatory activity, dose-dependently enhanced the gastric emptying at 0.03 to 1 mg/kg, p.o., whereas this drug did not affect the small intestinal propulsion, or the proximal and distal colonic propulsion. Neostigmine, an AChE inhibitor, dose-dependently enhanced the small intestinal propulsion and the proximal and the distal colonic propulsion at 0.3 to 10 mg/kg, p.o., whereas it delayed the gastric emptying at 10 mg/kg, p.o. The present results demonstrate that KW-5092 enhances the GI propulsion from the stomach to the colon and that metoclopramide or neostigmine enhances only the upper or the lower GI propulsion, respectively. Thus, KW-5092 may be a gastroprokinetic drug of a novel type for the treatment of GI motility dysfunctions in a wide range from the stomach to the colon.

Pharmacological properties of KF18259, a novel 5-HT3-receptor antagonist, in rats: inhibition of the distal colonic function

We investigated the effects of KF18259 (endo-(8-methyl-8-aza- bicyclo[3.2.1]oct-3-yl)-1-isobutyl-2-oxo-1,2-dihydro-4-quinolinecarboxyl ate hydrochloride), a novel 5-HT3-receptor antagonist, in a variety of rat models, which are assumed to be mediated via 5-HT3 receptors, in comparison with those of YM060 ((R)-5-[(1-methyl-3-indolyl)carbonyl]-4,5,6,7-tetrahydro-1H- benzimidazole hydrochloride), granisetron and ondansetron. KF18259 inhibited wrap-restraint stress-induced defecation. The doses of KF18259 to inhibit wrap-restraint stress-induced defecation were lower than those to inhibit the 5-HT-induced von Bezold-Jarisch reflex and the cisplatin-induced slowing of gastric emptying. In contrast, the doses of YM060, granisetron and ondansetron to inhibit these three responses were similar. Moreover, KF18259 inhibited the wrap-restraint stress-induced propulsive motility of the proximal and distal colon. The effect of KF18259 on the distal colon was as potent as that on defecation and was more potent than that on the proximal colon. These results indicate that KF18259 potently inhibits the distal colonic function. KF18259 may be a useful tool for the discrimination of the 5-HT3-receptors located on the distal colon and other tissues.