Serotonin and cholecystokinin mediate nutrient-induced segmentation in guinea pig small intestine

Segmentation is an important process in nutrient mixing and absorption; however, the mechanisms underlying this motility pattern are poorly understood. Segmentation can be induced by luminal perfusion of fatty acid in guinea pig small intestine in vitro and mimicked by the serotonin (5-HT) reuptake inhibitor fluoxetine (300 nM) and by cholecystokinin (CCK). Serotonergic and CCK-related mechanisms underlying nutrient-induced segmentation were investigated using selective 5-HT and CCK receptor antagonists on isolated segments of small intestine luminally perfused with 1 mM decanoic acid. Motility patterns were analyzed using video imaging and spatiotemporal maps. Segmenting activity mediated by decanoic acid was depressed following luminal application of the 5-HT receptor antagonists granisetron (5-HT3, 1 μM) and SB-207266 (5-HT4, 10 nM) and the CCK receptor antagonists devazepide (CCK-1, 300 nM) and L-365260 (CCK-2, 300 nM), but these antagonists did not further depress segmentation when combined. The P2 receptor antagonist pyridoxal phosphate-6-azophenyl-2′,4′-disulfonate (10 μM) had no effect on activity. Serosal application of 5-HT antagonists had little effect on segmentation in the duodenum but reduced activity in the jejunum when granisetron and SB-207266 were applied together. These results reveal that 5-HT3 and 5-HT4 receptors, as well as CCK-1 and CCK-2 receptors, are critical in regulating decanoic acid-induced segmentation. Computational simulation indicated that these data are consistent with decanoic acid activating two pathways in the mucosa that converge within the enteric neural circuitry, while contraction-induced release of 5-HT from the mucosa provides feedback into the neural circuit to set the time course of the overall contractile activity.

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Mechanisms underlying nutrient-induced segmentation in isolated guinea pig small intestine

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00441.2006 ◽

2007 ◽

Vol 292 (4) ◽

pp. G1162-G1172 ◽

Cited By ~ 34

Author(s):

R. M. Gwynne ◽

J. C. Bornstein

Keyword(s):

Small Intestine ◽

Guinea Pig ◽

Motor Neurons ◽

Slow Wave ◽

Neural Circuit ◽

Circular Muscle ◽

Decanoic Acid ◽

Slow Waves ◽

Longitudinal Position

Mechanisms underlying nutrient-induced segmentation within the gut are not well understood. We have shown that decanoic acid and some amino acids induce neurally dependent segmentation in guinea pig small intestine in vitro. This study examined the neural mechanisms underlying segmentation in the circular muscle and whether the timing of segmentation contractions also depends on slow waves. Decanoic acid (1 mM) was infused into the lumen of guinea pig duodenum and jejunum. Video imaging was used to monitor intestinal diameter as a function of both longitudinal position and time. Circular muscle electrical activity was recorded by using suction electrodes. Recordings from sites of segmenting contractions showed they are always associated with excitatory junction potentials leading to action potentials. Recordings from sites oral and anal to segmenting contractions revealed inhibitory junction potentials that were time locked to those contractions. Slow waves were never observed underlying segmenting contractions. In paralyzed preparations, intracellular recording revealed that slow-wave frequency was highly consistent at 19.5 (SD 1.4) cycles per minute (c/min) in duodenum and 16.6 (SD 1.1) c/min in jejunum. By contrast, the frequencies of segmenting contractions varied widely (duodenum: 3.6–28.8 c/min, median 10.8 c/min; jejunum: 3.0–27.0 c/min, median 7.8 c/min) and sometimes exceeded slow-wave frequencies for that region. Thus nutrient-induced segmentation contractions in guinea pig small intestine do not depend on slow-wave activity. Rather they result from a neural circuit producing rhythmic localized activity in excitatory motor neurons, while simultaneously activating surrounding inhibitory motor neurons.

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Effects of certain metabolites on the contractile activity and acetylcholine formation of the small intestine of the guinea pig

Folia Pharmacologica Japonica ◽

10.1254/fpj.54.464 ◽

1958 ◽

Vol 54 (3) ◽

pp. 464-479

Author(s):

Fumiya OGATA

Keyword(s):

Small Intestine ◽

Guinea Pig ◽

Contractile Activity

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Synergism between ouabain and monensin in neurogenic responses of guinea-pig vas deferens

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y88-100 ◽

1988 ◽

Vol 66 (5) ◽

pp. 643-647 ◽

Cited By ~ 5

Author(s):

Takeshi Katsuragi ◽

Lulu Kuratomi ◽

Koji Miyamoto ◽

Tatsuo Furukawa

Keyword(s):

Guinea Pig ◽

Time Course ◽

Vas Deferens ◽

Contractile Activity ◽

Atpase Inhibitor ◽

Exchange System ◽

Deficient Medium ◽

Small Contraction ◽

Monensin A ◽

Stimulation Of

Interrelations between ouabain, a Na+–K+ ATPase inhibitor, and monensin, a Na+ ionophore, on noradrenaline liberation and contractile activity were evaluated in the guinea-pig vas deferens. Monensin (1 μM) per se elicited a small contraction of the tissue. However, amplitude and time to the peak of large and sustained contractions evoked by 10 μM ouabain were potentiated and markedly shortened, respectively, by monensin. Contractions elicited by ouabain with or without monensin were prevented by 3 μM phentolamine or by pretreatment with reserpine. Contractions evoked by K+-free solution were augmented by monensin. In an HPLC study, noradrenaline outflow from the vas deferens was moderately and considerably increased by monensin (10 μM) and ouabain (100 μM), respectively. The ouabain-evoked output of noradrenaline was enhanced in the presence of monensin and the time course for maximum noradrenaline release was shortened, as was the contractile activity. This enhanced outflow after ouabain plus monensin was reserpine sensitive but not tetrodotoxin sensitive. Furthermore, this noradrenaline outflow was roughly halved in Na+-deficient medium, but was unaltered in Ca2+-free medium. These findings suggest that the synergistic effect of ouabain and monensin on noradrenaline liberation from the guinea-pig vas deferens may be due to an elevation of cytoplasmic Ca2+ concentrations, presumably resulting from a stimulation of intracellular Na+–Ca2+ exchange system, but not enhanced Ca2+ entry.

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Benzodiazepine analogues L365,260 and L364,718 as gastrin and pancreatic CCK receptor antagonists

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1989.257.1.g169 ◽

1989 ◽

Vol 257 (1) ◽

pp. G169-G174 ◽

Cited By ~ 2

Author(s):

S. C. Huang ◽

L. Zhang ◽

H. C. Chiang ◽

S. A. Wank ◽

P. N. Maton ◽

...

Keyword(s):

Smooth Muscle ◽

Guinea Pig ◽

Muscle Contraction ◽

Smooth Muscle Contraction ◽

Receptor Antagonists ◽

Amylase Release ◽

Pancreatic Acini ◽

Cck Receptors ◽

Guinea Pig Stomach ◽

Cck Receptor Antagonists

We examined the ability of the recently described 3-(benzoylamino)benzodiazepine analogue L365,260 and the 3-(acylamino)benzodiazepine analogue L364,718 to distinguish gastrin from pancreatic cholecystokinin (CCK) receptors. Neither L365,260 nor L364,718 when present alone (1 microM) caused stimulation of amylase release from guinea pig pancreatic acini or caused contraction of smooth muscle cells from guinea pig stomach. Each analogue inhibited CCK-stimulated amylase release, gastrin-17-I-stimulated smooth muscle contraction, binding of 125I-Bolton-Hunter-cholecystokinin octapeptide (125I-BH-CCK-8) to pancreatic CCK receptors, and binding of 125I-gastrin-17-I to gastrin receptors on pancreatic acini. L365,260, (Ki, 7.3 +/- 0.8 nM) was 50-70 times more potent than L364,718 at inhibiting binding of 125I-gastrin to pancreatic acini or gastrin-stimulated smooth muscle contraction. In contrast, L364,718 (Ki, 4 +/- 1 nM) was 145-200 times more potent than L365,260 at inhibiting binding of 125I-BH-CCK-8 to pancreatic acini or CCK-stimulated amylase release. Neither L364,718 nor L365,260 distinguished between high- and low-affinity CCK binding sites. L365,260 and L364,718 did not inhibit binding of radiolabeled vasoactive intestinal peptide, secretin, bombesin, substance P, or N-methylscopolamine to pancreatic acini. These results demonstrate that, in contrast to other gastrin-CCK receptor antagonists described, L365,260 is a selective gastrin receptor antagonist having an 80-fold higher affinity for gastrin than pancreatic CCK receptor, whereas L364,718 has a 125-fold higher affinity for pancreatic CCK receptors. Because of the selectivity of these two antagonists the involvement of CCK and gastrin in various physiological processes can be differentiated even when both receptors occur on the same cell.

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Stimulation of adenosine A1 and A2A receptors by AMP in the submucosal plexus of guinea pig small intestine

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00257.2006 ◽

2007 ◽

Vol 292 (2) ◽

pp. G492-G500 ◽

Cited By ~ 16

Author(s):

Na Gao ◽

Hong-Zhen Hu ◽

Sumei Liu ◽

Chuanyun Gao ◽

Yun Xia ◽

...

Keyword(s):

Small Intestine ◽

Guinea Pig ◽

Receptor Antagonist ◽

Pyridoxal Phosphate ◽

Disulfonic Acid ◽

Receptor Subtype ◽

Excitatory Postsynaptic Potentials ◽

Submucosal Plexus ◽

Postsynaptic Potentials ◽

Stimulation Of

Actions of adenosine 5′-monophosphate (AMP) on electrical and synaptic behavior of submucosal neurons in guinea pig small intestine were studied with “sharp” intracellular microelectrodes. Application of AMP (0.3–100 μM) evoked slowly activating depolarizing responses associated with increased excitability in 80.5% of the neurons. The responses were concentration dependent with an EC50 of 3.5 ± 0.5 μM. They were abolished by the adenosine A2A receptor antagonist ZM-241385 but not by pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid, trinitrophenyl-ATP, 8-cyclopentyl-1,3-dimethylxanthine, suramin, or MRS-12201220. The AMP-evoked responses were insensitive to AACOCF3 or ryanodine. They were reduced significantly by 1) U-73122, which is a phospholipase C inhibitor; 2) cyclopiazonic acid, which blocks the Ca2+ pump in intraneuronal membranes; and 3) 2-aminoethoxy-diphenylborane, which is an inositol ( 1 , 4 , 5 )-trisphosphate receptor antagonist. Inhibitors of PKC or calmodulin-dependent protein kinase also suppressed the AMP-evoked excitatory responses. Exposure to AMP suppressed fast nicotinic ionotropic postsynaptic potentials, slow metabotropic excitatory postsynaptic potentials, and slow noradrenergic inhibitory postsynaptic potentials in the submucosal plexus. Inhibition of each form of synaptic transmission reflected action at presynaptic inhibitory adenosine A1 receptors. Slow excitatory postsynaptic potentials, which were mediated by the release of ATP and stimulation of P2Y1 purinergic receptors in the submucosal plexus, were not suppressed by AMP. The results suggest an excitatory action of AMP at adenosine A2A receptors on neuronal cell bodies and presynaptic inhibitory actions mediated by adenosine A1 receptors for most forms of neurotransmission in the submucosal plexus, with the exception of slow excitatory purinergic transmission mediated by the P2Y1 receptor subtype.

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Functionally distinct receptors for cholecystokinin and gastrin on dispersed chief cells from guinea pig stomach

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1988.254.2.g151 ◽

1988 ◽

Vol 254 (2) ◽

pp. G151-G155 ◽

Cited By ~ 2

Author(s):

J. A. Cherner ◽

V. E. Sutliff ◽

D. M. Grybowski ◽

R. T. Jensen ◽

J. D. Gardner

Keyword(s):

Amino Acids ◽

Guinea Pig ◽

Receptor Antagonists ◽

Chief Cells ◽

Pepsinogen Secretion ◽

Guinea Pig Stomach ◽

Cck Receptor Antagonists ◽

Stimulation Of

Caerulein, gastrin, and C-terminal fragments of cholecystokinin (CCK) varying in length from eight (CCK-8) to four (CCK-4) amino acids stimulate pepsinogen secretion from dispersed chief cells prepared from guinea pig stomach. C-terminal fragments of CCK containing fewer than four amino acids, even when tested at concentrations as high as 3 mM, do not stimulate pepsinogen secretion. The efficacies of gastrin and the various CCK-related peptides, coupled with the pattern of action of CCK receptor antagonists, indicate that chief cells from guinea pig stomach possess two functionally distinct classes of receptors, C-receptors and G-receptors. The C-receptors can be occupied by caerulein, CCK-8, CCK-7, des(SO3)CCK-8, or des(SO3)CCK-7, and occupation of C-receptors causes full stimulation of pepsinogen secretion. G-receptors can be occupied by gastrin I, gastrin II, CCK-6, CCK-5, or CCK-4, and occupation of G-receptors causes stimulation of pepsinogen secretion that is 60% of maximal.

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Cholecystokinin receptors on gallbladder muscle and pancreatic acinar cells: a comparative study

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1988.255.4.g512 ◽

1988 ◽

Vol 255 (4) ◽

pp. G512-G521 ◽

Cited By ~ 5

Author(s):

T. von Schrenck ◽

T. H. Moran ◽

P. Heinz-Erian ◽

J. D. Gardner ◽

R. T. Jensen

Keyword(s):

Guinea Pig ◽

Ph Dependence ◽

Muscle Layer ◽

Pancreatic Acinar Cells ◽

Receptor Antagonists ◽

Similar Time ◽

Amylase Release ◽

Cck Receptors ◽

Tissue Sections ◽

Cck Receptor Antagonists

To compare receptors for cholecystokinin (CCK) in pancreas and gallbladder, we measured binding of 125I-Bolton-Hunter-labeled CCK-8 (125I-BH-CCK-8) to tissue sections from guinea pig gallbladder and pancreas under identical conditions. In both tissues, binding had similar time-, temperature-, and pH dependence, was reversible, saturable and inhibited only by CCK related peptides or CCK receptor antagonists. Autoradiography localized 125I-BH-CCK-8 binding to the smooth muscle layer in the gallbladder. Binding of 125I-BH-CCK-8 to gallbladder sections was inhibited by various agonists with the following potencies (IC50):CCK-8 (0.4 nM) greater than des(SO3)CCK-8 (0.07 microM) greater than gastrin-17-I (1.7 +/- 0.3 microM) and by various receptor antagonists with the following potencies: L364,718 (1.5 nM) greater than CR 1409 (0.19 microM) greater than asperlicin = CBZ-CCK-(27-32)-NH2 (1 microM) greater than Bt2cGMP (120 microM). Similar potencies were found for the agonists and antagonists for pancreas sections. Inhibition of binding of 125I-BH-CCK-8 by 11 different analogues of proglumide gave similar potencies for both pancreas and gallbladder. The potencies of agonists in stimulating and antagonists in inhibiting CCK-stimulated contraction or amylase release correlated closely with their abilities to inhibit 125I-BH-CCK-8 binding to gallbladder or pancreas sections or acini, respectively. The present results demonstrate and characterize a method that can be used to compare the CCK receptors in guinea pig gallbladder and pancreas under identical conditions. Moreover, this study demonstrates that gallbladder and pancreatic CCK receptors have similar affinities for the various agonists and antagonists tested and, therefore, provides no evidence that they represent different subtypes of CCK receptors that can be distinguished pharmacologically.

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