Longitudinal Muscle Of Distal Colon Research Articles

Arginine vasopressin, via activation of post-junctional V1 receptors, induces contractile effects in mouse distal colon

The aim of this study was to analyze whether arginine vasopressin (AVP) may be considered a modulator of intestinal motility. In this view, we evaluated, in vitro, the effects induced by exogenous administration of AVP on the contractility of mouse distal colon, the subtype(s) of receptor(s) activated and the action mechanism. Isometric recordings were performed on longitudinal and circular muscle strips of mouse distal colon. AVP (0.001nM–100nM) caused concentration-dependent contractile effects only on the longitudinal muscle, antagonized by the V1 receptor antagonist, V-1880. AVP-induced effect was not modified by tetrodotoxin, atropine and indomethacin. Contractile response to AVP was reduced in Ca2+-free solution or in the presence of nifedipine, and it was abolished by depletion of calcium intracellular stores after repetitive addition of carbachol in calcium-free medium with addition of cyclopiazonic acid. U-73122, an inhibitor of the phospholipase C, effectively antagonized AVP effects, whilst it was not affected by an adenylyl cyclase inhibitor. Oxytocin induced an excitatory effect in the longitudinal muscle of distal colon at very high concentrations, effect antagonized by V-1880. The results of this study shown that AVP, via activation of V1 receptors, is able to modulate positively contractile activity of longitudinal muscle of mouse distal colon, independently by enteric nerve activation and prostaglandin synthesis. Contractile response is achieved by increase in cytoplasmatic Ca2+ concentration via extracellular Ca2+ influx from L-type Ca2+ channels and via Ca2+ release from intracellular stores through phospholipase C pathway. No modulation has been observed on the contractility of the circular muscle.

Acetylene compound isolated from Atractylodes japonica stimulates the contractility of rat distal colon via inhibiting the nitrergic–purinergic relaxation

Our previous research has showed that rhizome of Atractylodes japonica Koidz (Compositae) exhibits an increase in the spontaneous contractility of distal colon in rats. The aims of this study are to identify the phytochemical(s), which stimulate(s) the colonic contractility, contained in Atractylodes japonica and to evaluate the pharmacological mechanism responsible for the colonic muscle contraction. Based on the stimulatory activity-guided fractionation on the isometric contraction of rat distal colonic strips, atractylodiol (ATD) and diacetyl-atractylodiol (DATD) were isolated from the CHCl(3) fractions of Atractylodes japonica. ATD and DATD dose-dependently increased both tension and amplitude of distal colon longitudinal muscle (DCLM), but they stimulated only amplitude in the distal colon circular muscle. The ED(50) values of ATD and DATD to stimulate the amplitude of DCLM were revealed as 9.1×10(-9)M and 1.8×10(-8)M, respectively. l-NAME (0.1mM) significantly increased the ADT (1μM)-induced contraction of DCLM, whereas SNAP (0.1mM) markedly reduced the stimulatory effects of ATD on DCLM contractility. The combined effects of SNAP and atropine (0.5μM) on the ATD-induced contraction of DCLM were similar to the inhibitory effects of SNAP alone. Suramin (0.1mM) significantly enhanced the increase of ATD-induced DCLM contraction, whereas ADPβS (0.1mM) markedly abolished the stimulatory effects of ATD on the spontaneous contractility of DCLM. The present results demonstrate that acetylene compounds, ATD and DATD, are the effective phytochemical of Atractylodes japonica to stimulate the motility of distal colon in rats, and ATD possibly enhances the spontaneous contractility of distal colon through inhibiting the mechanism of nitrergic-purinergic relaxation.

Arecoline excites the contraction of distal colonic smooth muscle strips in rats via the M3 receptor – extracellular Ca2+ influx – Ca2+ store release pathway

Areca is a Chinese herbal medicine that is widely used for constipation. However the mechanisms of its action are not clear. We investigated the effects of arecoline, the most active component of areca, on the motility of rat distal colonic smooth muscle strips. In longitudinal muscle of distal colon (LMDC) and circular muscle of distal colon (CMDC), arecoline increased the contraction in a dose-dependent manner. Tetrodotoxin (TTX) did not inhibit the effects of arecoline. The contractile response to arecoline was completely antagonized by atropine. 4-Diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) strongly depressed the response to arecoline, but gallamine and methoctramine did not. Nifedipine, 2-aminoethoxydiphenyl borate (2-APB), and Ca2+-free Krebs solution with EGTA partly inhibited the effects of arecoline. The sum of Ca2+-free Krebs solution, EGTA, and 2-APB completely inhibited the effects of arecoline. The results show that arecoline stimulates distal colonic contraction in rats via the muscarinic (M3) receptor - extracellular Ca2+ influx - Ca2+ store release pathway. It is likely that the action of areca in relieving constipation is due to its stimulation of muscle contraction.

Hexane extract of Poncirus trifoliata (L.) Raf. stimulates the motility of rat distal colon

Aim of the study Poncirus trifoliata (L.) Raf. (Rutaceae, PT) has been commonly used for treating gastrointestinal (GI) disorders in Korean traditional medicine, but its pharmacological roles in the regulation of colonic motility have not been clarified. This study investigated the regulatory effects of PT on the colonic motility. Materials and methods Immature fruits of PT were sequentially partitioned with MeOH, n-hexane, CHCl 3, EtOAc, n-BuOH and H 2O, and the effects of PT extracts on the contractility of colonic strips and colonic luminal transit in rats were measured in vitro and in vivo, respectively. Results Among six different extracts, only hexane extract of PT (PTHE) dose-dependently increased the low frequency contraction of longitudinal muscle in distal colonic strips, and the ED 50 value was revealed to be 0.71 μg/ml. The contractile patterns induced by PTHE were remarkably different from those caused by acetylcholine (ACh) and serotonin (5-HT). The stimulatory effects of PTHE on the whole distal colonic strips were more prominent than on the mucosa/submucosa-denuded segments. The M 2 receptor-preferring, methoctramine (0.5 μM), and M 3 receptor-preferring antagonist, 4-DAMP (0.5 μM) significantly blocked the PTHE (1 μg/ml)-induced contraction of distal colon longitudinal muscles, whereas the 5-HT receptor antagonists (1.0 μM, alone or in combination) selective for 5-HT 3 (ondansetron), 5-HT 4 (GR113808) and 5-HT 1, 2, 5–7 (methysergide) receptors did not change the PTHE (1 μg/ml)-induced contractility of distal colon longitudinal muscles. SNAP (0.1 mM), a NO donor, enhanced the stimulatory effects of PTHE on the longitudinal muscle of distal colon, but l-NAME (0.1 mM), a NO synthesis inhibitor, had no effects. PTHE (10–100 mg/kg) caused a dose-dependent increase of colonic luminal transit. Conclusions Collectively, these findings suggest that PTHE specifically acts on the longitudinal muscle of distal colon in rats, and these stimulatory effects are likely mediated, at least, by activation of acetylcholinergic M 2 and M 3 receptors.

In vitro and in vivo characterization of opioid activities of C-terminal esterified endomorphin-2 analogs

Previously, we have synthesized a series of endomorphin-2 (EM-2) analogs by the substitution of C-terminal amide group. In the present study, to further our knowledge of the influence of C-terminal esterified modification on the pharmacological activities, we investigated the in vitro and in vivo opioid activities of C-terminal esterified EM-2 analogs 1– 3. Our results showed that the ED 50 values on contractions of the longitudinal muscle of distal colon induced by analogs 1– 3 were about 1.5-fold higher, 2- and 8-fold lower than EM-2, respectively. In addition, intravenous (i.v.) injections of analogs 1 and 2 dose-dependently decreased the system arterial pressure (SAP) and heart rate (HR) in anesthetized rats, but the degree of the hypotension and bradycardia was significantly smaller relative to the parent. Moreover, analog 3 was almost ineffective. Nevertheless, all these analogs produced potent antinociception in the tail-flick test after intracerebroventricular (i.c.v.) injection, and this antinociception was inhibited by naloxone, indicating an opioid mechanism. In summary, these results gave the evidence that the conversion of C-terminal amide to esterified modification may play an important role in the regulation of opioid affinities and pharmacological activities.

Type 1 Diabetes attenuates the modulatory effects of endomorphins on mouse colonic motility

Our previous studies have shown that endomorphins (EMs), endogenous ligands for mu-opioid receptor, display a significant potentiation effect on mouse colonic motility. In the present study, to assess whether diabetes alters these modulatory effects of EMs on colonic motility, we investigated the effects of EMs in type 1 diabetic mouse colon in vitro. At 4 weeks after the onset of diabetes, carbachol-induced contractions in the longitudinal muscle of distal colon were significantly reduced compared to those of non-diabetic mice. Furthermore, the contractile effects induced by EMs in the longitudinal muscle of distal colon and in the circular muscle of proximal colon were also significantly reduced by type 1 diabetes. It is noteworthy that EMs-induced longitudinal muscle contractions were not significantly affected by atropine, Nomega-nitro-l-arginine methylester (l-NAME), phentolamine, propranolol, hexamethonium, methysergide and naltrindole. On the other hand, tetrodotoxin, indomethacin, naloxone, beta-funaltrexamine, naloxonazine and nor-binaltorphimine completely abolished these effects. These mechanisms responsible for EMs-induced modulatory effects in type 1 diabetes were in good agreement with those of non-diabetes, indicating similar mechanisms in both diabetes and non-diabetes. At 8 weeks after the onset of diabetes, both carbachol- and EMs-induced longitudinal muscle contractions were similar to those of short-time (4 weeks) diabetic mice. In summary, all the results indicated that type 1 diabetes significantly attenuated the modulatory effects of EMs on the mouse colonic motility, but the mechanisms responsible for these effects were not significantly altered.

Acetylcholine-related bowel dysmotility in homozygous mutant NCX/HOX11L.1-deficient (NCX−/−) mice—evidence that acetylcholine is implicated in causing intestinal neuronal dysplasia

Background/purpose Homozygous mutant Ncx/Hox11L.1-deficient (Ncx−/−) mice develop mega-ileo-ceco-colon (mega-ICC) with a caliber change in the proximal colon. The authors investigated the mechanism of intestinal dysmotility in these mice. Methods Five-week-old Ncx−/− mice with mega ICC were compared with age-matched BDF1 control mice. Jejunum, ileum, and colon were excised from all mice and 1.0-cm-long strips of each organ, each with a resting tension of 0.5 g, were suspended in an organ bath filled with Tyrode’s solution at 37°C and bubbled with a mixture of 95% oxygen and 5% carbon dioxide. Contractile responses to acetylcholine chloride (ACh), histamine, serotonin, and barium chloride (BaCl 2 ) were recorded isometrically. Results For ACh, Ncx−/− mice had decreased distal colon circular muscle contraction only at lower doses and decreased distal colon longitudinal muscle contraction for all doses compared with controls ( P < .05 or P < .01). In the proximal colon, Ncx−/− mice had increased circular muscle contraction only at higher doses and decreased longitudinal muscle contraction only at lower doses compared with controls ( P < .01 or P < .05). ACh did not affect jejunum, and there were no significant effects on ileum. There was no response to histamine and serotonin by any part of the bowel, and the response to BaCl 2 was the same for both Ncx−/− mice and controls. Conclusions Only ACh differentially affected muscle contraction in Ncx−/− mice in the proximal and distal colon. Thus, ACh is implicated in causing the bowel dysmotility seen in Ncx−/− mice and human IND.

Changes in mechanism of PACAP-induced relaxation in longitudinal muscle of the distal colon of Wistar rats with age

Mechanisms of relaxation of longitudinal muscle of the distal colon induced by exogenously added pituitary adenylate cyclase activating peptide (PACAP) were studied in 2- to 30-week-old Wistar rats. Exogenous PACAP induced very significant relaxation of the longitudinal muscle in 2-week-old rats, but this effect decreased significantly with age. The cyclic AMP–cyclic AMP-dependent protein kinase (PKA) pathway and the tyrosine kinase–small conductance Ca 2+-activated K + channel (SK channel) pathway were found to be involved in the mechanism of PACAP-induced relaxation. In 2-week-old rats, PACAP-induced relaxation was significantly inhibited by tetrodotoxin (TTX). Since relaxation was also significantly inhibited by N G-nitro- l-arginine ( N 5-nitro-amidino- l-2,5-diamino-pentanoic acid: l-NOARG), the neurogenic effect of PACAP seems to be mediated mainly through nitric oxide neurons. In 8-week-old rats, l-NOARG and TTX had little effect on PACAP-induced relaxation, suggesting that the relaxant effect in 8-week-old rats is a direct action on longitudinal smooth muscle cells. Changes in the mechanisms of PACAP-induced relaxation with age were examined in the distal colon in relation to changes in the neurogenic and the direct effects of PACAP. The neurogenic effect in the exogenous PACAP-induced relaxation of the longitudinal muscle of the Wistar rat distal colon is dominant in tissue isolated from 2-week-old and lost in tissue isolated from 8-week-old rats.

Effect of areca on contraction of colonic muscle strips in rats.

To investigate the effects of areca on the contractile activity of isolated colonic muscle strips in rats and mechanism involved. Each strip (LMPC, longitudinal muscle of proximal colon; CMPC, circular muscle of proximal colon; LMDC, longitudinal muscle of distal colon; CMDC, circular muscle of distal colon.) was suspended in a tissue chamber containing 5 mL Krebs solution (37 degrees C), bubbled continuously with 950 mL.L(-1) O(2) and 50 mL.L(-1) CO(2). The mean contractile amplitude (A), the resting tension (T), and the contractile frequency (F) were simultaneously recorded on recorders. Areca dose dependently increased the mean contractile amplitude, the resting tension of proximal and distal colonic smooth muscle strips in rats (P<0.05). It also partly increased the contractile frequency of colonic smooth muscle strips in rats (P<0.05). The effects were partly inhibited by atropine (the resting tension of LMPC decreased from 0.44 +/- 0.12 to 0.17 +/- 0.03; the resting tension of LMDC decreased from 0.71 +/- 0.14 to 0.03 +/- 0.01; the mean contractile amplitude of LMPC increased from -45.8 +/- 7.2 to -30.5 +/- 2.9; the motility index of CMDC decreased from 86.6 +/- 17.3 to 32.8 +/- 9.3; P<0.05 vs areca), but the effects were not inhibited by hexamethonium (P>0.05). Areca stimulated the motility of isolated colonic smooth muscle strips in rats. The stimulation of areca might be relevant with M receptor partly.

Increase in participation of vasoactive intestinal peptide in relaxation of the distal colon of Wistar rats with age.

Changes in participation of vasoactive intestinal peptide (VIP) in nonadrenergic noncholinergic (NANC) relaxation of longitudinal muscle of the distal colon with age were studied in 2- to 50-week-old Wistar rats in vitro. The extent of the VIP-mediated component of the relaxation induced by electrical field stimulation (EFS) was determined by the effect of VIP(10 - 28), a VIP receptor antagonist. In 2-week-old rats, the extent of the VIP-mediated component of the relaxation was scarce, about 10%, whereas the component gradually increase with age and reached the maximum extent 66% at 50-week-old. Since our previous results suggest that VIP induces NANC relaxation via activation of charybdotoxin (ChTx, a blocker of large conductance Ca(2+)-activated K(+) channel)-sensitive K(+) channels with concomitant slow hyperpolarization in the muscle cells, we next studied whether ChTx-sensitive component and slow hyperpolarization changes with age. Extent of ChTx-sensitive component of the relaxation increased with age, showing a very similar pattern to VIP-mediated one. EFS induced monophasic inhibitory junction potentials (i.j.ps) in longitudinal muscle cells of the distal colon of 2- and 4-week-old. EFS also induced biphasic i.j.ps in many longitudinal muscle cells of 8- and 50-week-old: rapid and subsequent slow hyperpolarization. A VIP receptor antagonist selectively inhibited the slow hyperpolarization. Exogenously added VIP induced no appreciable change in the membrane potential of longitudinal muscle cells of 2-week-old, whereas it induced slight slow hyperpolarization of the cell membrane in 4-week-old and magnitude of the hyperpolarization increased with age. On the other hand, relaxant response of the longitudinal muscle to exogenously added VIP was high in younger rats. The present results suggest that the role of VIP in mediating NANC relaxation of longitudinal muscle of the Wistar rat distal colon is very little at neonatal stage, but it increases with age.

Selective and functional 5-hydroxytryptamine4 receptor antagonism by SB 207266.

1. The pharmacology of a novel 5-HT4 receptor antagonist, SB 207266 has been evaluated in vitro in the guinea-pig distal colon longitudinal muscle myenteric plexus (LMMP) and in vivo in the dog Heidenhain pouch. 2. SB 207266 is a highly potent antagonist of 5-HT-evoked, cholinergically-mediated contractions in the guinea-pig distal colon. Low concentrations (0.1-10 nM) produced a parallel shift to the right of the concentration-effect curve (apparent pA2 10.6 +/- 0.1) with no significant effect on the maximum response. With higher concentrations of SB 207266 (30 nM and above) the maximum response to 5-HT was reduced. 3. The antagonism seen with SB 207266 cannot be attributed to a non-selective effect since high concentrations (1 microM) had no effect on cholinergically-mediated contractions evoked by the nicotinic receptor agonist DMPP in the same preparation. 4. SB 207266 is not an irreversible antagonist since the effects of the compound were reversible upon washing of the tissue. 5. In the dog Heidenhain pouch, oral (0.1-100 micrograms kg-1) and intravenous (0.1-100 micrograms kg-1) administration of SB 207266 produced a dose-dependent antagonism of the contractions evoked by a bolus intravenous injection of 5-HT. An ID50 for SB 207266 of 1.3 micrograms kg-1 was obtained following i.v. administration and 9.6 micrograms kg-1 following oral administration. 6. The antagonistic effects of SB 207266 (0.1-100 micrograms kg-1) in the dog Heidenhain pouch were long lasting since, following oral administration, the response to 5-HT was reduced for at least 135 min. 7. SB 207266 is a highly potent, highly selective and orally active 5-HT4 receptor antagonist. This compound is the first orally active amide to be identified in this class of antagonists and as such is an important new tool in the evaluation of 5-HT4 receptor function both in vitro and in vivo.

Azabicyclic indole esters as potent 5-HT 4 receptor antagonists

The synthesis of a series of azabicyclic indole esters is described and their potency reported as 5-HT 4 receptor antagonists. Optimization of the most potent compound ( 19) by preparing the corresponding oxazino[3,2- a]indole ester afforded 34, which had a pIC 50 of 9.5 in the guinea pig distal colon longitudinal muscle myenteric plexus preparation.

A nitric oxide mediated component of nonadrenergic, noncholinergic responses of cat distal colon longitudinal muscle

A nitric oxide mediated component of nonadrenergic, noncholinergic responses of cat distal colon longitudinal muscle

Apamin distinguishes two types of relaxation mediated by enteric nerves in the guinea-pig gastrointestinal tract.

Eight smooth muscle preparations from the stomach, small intestine and large intestine of the guinea-pig were used to compare apamin's actions in reducing the effectiveness of transmission from enteric inhibitory nerves and in reducing responses to inhibitory agonists alpha, beta-methylene ATP, VIP and isoprenaline. The effects of apamin on inhibitory reflexes in the ileum and colon were also evaluated. Apamin had little or no effect on responses to VIP and isoprenaline in any region, but consistently and substantially reduced responses to alpha, beta-methylene ATP. Responses to stimulation of enteric inhibitory neurons were substantially reduced by apamin in the antrum circular muscle, ileum longitudinal and circular muscle, taenia coli and distal colon longitudinal muscle, but it was ineffective in the fundus circular muscle, proximal colon longitudinal muscle and distal colon circular muscle. It caused a small reduction of the relaxation of the ileal circular muscle caused reflexly by distension, but did not modify the similar descending inhibitory reflex in the circular muscle of the colon. It is concluded that apamin can be used to distinguish two types of non-noradrenergic transmission from enteric inhibitory nerves to gastrointestinal muscle. Furthermore, neither VIP nor ATP can be the sole transmitter chemical released from enteric inhibitory neurons throughout the gastrointestinal tract.