Action of gastrointestinal hormones on the myoelectric activity of the sphincter of Oddi in living rabbit

The aim of this work was to compare the action of gastrointestinal (GI) hormones on the myoelectrical activity of the sphincter of Oddi. Using an experimental design previously described, we studied the electrical activity of the sphincter of Oddi and compared the percentage variation in the number of spikes before and after injection of hormones. Increasing doses of the following hormones were injected i.v. at random: CCK, OP-CCK, caerulein, bombesin, gastrin, secretin and glucagon. CCK and caerulein (as previously found), and also bombesin, OP-CCK and gastrin increased the spikes activity of the sphincter of Oddi. Secretin had no effect and glucagon decreased this activity. There was no tachyphylaxis, but a good dose-effect relationship for each hormone. Compared on a molar basis caerulein is 8 times more effective than CCK and OP-CCK which in turn are more potent than bombesin. Gastrin acts only at pharmacological doses.     

Differential sensitivities of the sphincter of Oddi and gallbladder to cholecystokinin in the guinea pig: their role in transsphincteric bile flow.

Cholecystokinin (CCK) is considered to simply contract the gallbladder and relax the sphincter of Oddi with meals. In this study, we examined this hypothesis by investigating the action of CCK on the sphincter of Oddi and gallbladder of the guinea pig. The experimental design used an in vitro preparation of the sphincter of Oddi to measure contraction of the circular muscle. CCK increased tone in both the gallbladder and the sphincter of Oddi in a concentration-dependent manner. The normalized concentration-response curves for CCK, however, revealed that the gallbladder had a greater sensitivity to CCK (ED50 7 nM) than the sphincter of Oddi (ED50 22 nM; p < 0.01). Conversely, the sphincter was more sensitive to bethanechol than was the gallbladder. When the sphincter of Oddi was stimulated maximally with CCK in the presence of atropine (10(-6) M) or tetrodotoxin (10(-6) M), the contractile response was significantly reduced (p < 0.05) although not abolished. Conversely, atropine completely abolished the responses to bethanechol (10(-3) M) and transmural field stimulation (70 V, 10 Hz, 1 ms, for 20 s). Transmural field stimulation of the sphincter that had been precontracted with CCK (26 nM) caused a transient, initial relaxation followed by contraction. Pretreatment with atropine augmented the duration of this relaxation, which could be completely abolished by tetrodotoxin. Thus, CCK contracts the sphincter of Oddi in the guinea pig by a direct (myogenic) and a neural (likely cholinergic) mechanism. Relaxation of the sphincter of Oddi also occurs in the guinea pig via noncholinergic inhibitory nerves.(ABSTRACT TRUNCATED AT 250 WORDS)     

兔迷走神经在协调消化间期胆囊与奥迪氏括约肌运动方面的作用

目的：探讨兔迷走神经在协调消化间期胆囊（ＧＢ）与奥迪氏括约肌（ＳＯ）运动方面的作用。方法：运动禁食但自由饮水１５￣１８ｈ，乌拉坦静脉麻醉。蛙膀胱置入ＧＢ内，测ＧＢ内压，双极康铜丝电极引ＳＯ肌电。结果：消化间期ＧＢ位相性收缩（ＧＢＰＣ）与ＳＯ锋电位簇（ＣＳＰＳＯ）间存在１：１对应关系，迷走复合区（ＤＶＣ）内微量注射谷氨酸钠（ＭＳＧ）或促甲状腺素释放激素（ＴＲＨ）后ＰＣＧＢ及ＳＯ锋电位活动增强，ＧＢＰ     

Do motilin and pancreatic polypeptide regulate duodenal bile acid delivery?

The plasma levels of the enteric hormones, motilin and pancreatic polypeptide, cycle in association with fasting intestinal motility and are altered by feeding. Intravenous administration of motilin causes gallbladder contraction and increased sphincter of Oddi phasic motor activity, whereas pancreatic polypeptide causes gallbladder relaxation. To determine if endogenous plasma levels of motilin and pancreatic polypeptide control sphincter of Oddi and gallbladder motility, and regulate duodenal bile acid delivery, we measured during fasting and after feeding the correlation between (a) changes in plasma motilin or pancreatic polypeptide, and (b) the duodenal delivery of a steady-state hepatic output of radiolabelled bile acid. Four dogs were prepared with duodenal cannulas. Duodenal motility was recorded manometrically. Plasma levels of pancreatic polypeptide and motilin were determined during a full cycle of the migrating myoelectric complex for 20 min before and 40 min after ingestion of a standard meal. To assess the effect of the sphincter of Oddi and the gallbladder together, or the gallbladder alone on duodenal bile acid delivery, the dogs received a continuous i.v. infusion of [14C]taurocholic acid (TCA); duodenal delivery of TCA was quantitated with the sphincter of Oddi intact using duodenal marker perfusion, or with the sphincter of Oddi cannulated and zero outflow resistance. In the interdigestive period with the sphincter of Oddi intact, only 0.1 (r2) of the variance of duodenal bile acid delivery can be predicted from the variance of motilin, and the correlation of plasma pancreatic polypeptide with duodenal TCA delivery is opposite that expected if pancreatic polypeptide caused gallbladder relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Central origin on the excito-motric action of morphine on intestine]

In ewew fitted with a cerebro-ventricular cannula and equipped with extra-cellular bipolar electrodes on the antrum and proximal small intestine, an intraventricular injection of morphine at a dose (40 micrograms/kg) ineffective peripherally was followed within 1 min by an increased spike activity of the duodenum without disruption of the occurrence of migrating myoelectric complexes. This effect was paralleled by a reduction of antral motility and abolished by small intraventricular doses of nalorphine. After an intravenous injection of large doses of the drug drug (0.8 mg/kg), spike activity was increased at both jejunal and duodenal level without changes in the antrum and followed by a long-lasting disorganization of the motor profile. The results suggested a centrally mediated gastro-duodenal effect of morphine.     

Stimulus-dependent pacemaker activity in the distal canine lower esophageal sphincter

Electrical and mechanical properties of the distal canine lower esophageal sphincter were studied in vitro to investigate possible means of inducing pacemaker activity. Both direct excitation and block of potassium conductance were investigated. The acetylcholine analog, carbachol, induced tissue depolarization and increase in tone but no electrical slow waves. Tetraethylammonium (TEA) chloride induced depolarization and evoked continuous spiking activity and increase in tone. BaCl did not depolarize the tissue but low amplitude spiking activity developed and increased tone. The putative potassium channel blocker, aminacrine at 2 X 10(-4) M, induced electrical slow wave activity in the distal lower esophageal sphincter, with or without superimposed spikes, accompanied by phasic contractile activity. This activity closely resembled the spontaneous pacemaker activity observed previously in the proximal lower esophageal sphincter. The aminacrine-induced activity was abolished by calcium influx blockers. Aminacrine, but not TEA or BaCl, abolished the nonadrenergic nerve-mediated inhibitory junction potentials. In conclusion, block of inhibitory innervation, and induction of electrical slow waves as a control mechanism for phasic contractile activity, seems to require blockade of an aminacrine- but not TEA-sensitive potassium conductance.     

Histamine release as the basis for morphine action on bile duct and sphincter of Oddi

We have investigated the mechanism by which morphine contracts hog bile duct and sphincter of Oddi. Morphine contraction is antagonized by naloxone, competitively on the sphincter, noncompetitively on the bile duct. Diphenhydramine at low concentration (3.4 X 10(-6)M) also antagonizes both actions of morphine. Histamine has a very potent contracting action on the sphincter and bile duct and this is antagonized by diphenhydramine. Burimamide only weakly antagonizes the actions of morphine or histamine. Compound 48/80 causes a pronounced contraction of sphincter and bile duct following which morphine effects are greatly attenuated. These results suggest that morphine-induced contraction of the sphincter of Oddi and bile duct is mediated by a two step reaction involving interaction with a specific opiate receptor leading to the release of histamine which combines with an H1 receptor to produce the effect.     

Investigation of the mechanism of nicotine-induced relaxation on the sheep sphincter of Oddi

Possible mechanisms for nicotine-induced relaxation were investigated in the isolated sheep's sphincter of Oddi. Sheep's sphincter of Oddi rings were mounted in tissue bath with modified Krebs-Henseleit solution and aerated with 95% oxygen and 5% carbon dioxide. Tension was measured with isometric force transducers, and muscle relaxation was expressed as percent decrease of precontraction induced by carbachol. Nicotine (1 x 10(-5) to 3 x 10(-3) mol/L) produced concentration-dependent relaxation on sphincter of Oddi precontracted by carbachol (10(-6) mol/L). Nicotine-induced relaxation was 72.8 +/- 4.2% of precontraction with carbachol (10(-6) mol/L) (mean pD2 value, 3.76 +/- 0.05 mol/L). Nicotine-induced relaxation was not affected by N(w)-nitro L-arginine methyl ester (L-NAME) (3 x 10(-5) mol/L), methylene blue (10(-5) mol/L), indomethacin (10(-5) mol/L), hexamethonium (10(-5) mol/L), glibenclamide (10(-5) mol/L), 4-aminopyridine (10(-3) mol/L), tetraethylammonium (3 x 10(-4) mol/L), clotrimazole (10(-6) mol/L), 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) (10(-6) mol/L), and anthracene-9-carboxylate (9-AC) (10(-6) mol/L), but potentiated by bupivacain (10(-5) mol/L). A calcium-antagonizing effect of nicotine was not observed. The results suggest that nicotine-induced relaxation of the sheep's sphincter of Oddi is not mediated by the release of prostaglandins, nitric oxide (NO), or a related substance; by the activation of potassium channels or chloride channels; or by the stimulation of nicotinic cholinoceptors. Potentiation of the nicotine-induced relaxation by bupivacain indicates that blockade of sodium channels may play a role in this relaxation.     

Distribution of opioidergic,sympathetic and neuropeptide Y-positive nerves in the sphincter of Oddi and biliary tree of the monkey,Macaca fascicularis

Summary The opioidergic, sympathetic and neuropeptide Y-positive innervation of the sphincter of Oddi (common bile duct sphincter and pancreatic duct sphincter), as well as other segments of the extrahepatic biliary tree was studied in the monkey by use of immunohistochemistry. Methionine-enkephalin-positive nerves were seen to innervate the smooth muscle of all portions of the sphincter of Oddi and also local ganglion cells. No methionine-enkephalin-positive nerves could be detected in the common bile duct, pancreatic duct or gallbladder. Tyrosine hydroxylase-positive nerves occurred between smooth muscle bundles and also ran to local ganglion cells as well as along the common bile duct. Neuropeptide Y-positive nerves were observed within smooth muscle of the sphincter of Oddi (all portions), common bile duct, pancreatic duct and gallbladder. No evidence of any differential innervation of the pancreatic duct and common bile duct sphincters could be detected with these markers.     

Partial characterization of a tapeworm-secreted signal factor inducing sustained spike potentials in the smooth muscle of the rat small intestine

The rat tapeworm Hymenolepis diminuta alters the myoelectric activity of the small intestine. To determine if secreted factors from the tapeworm are responsible for these alterations of intestinal smooth muscle activity, tapeworm-conditioned medium (TCM) obtained from in vitro culture was infused via an indwelling cannula into the duodenum of an uninfected rat. Myoelectric recordings were analyzed for sustained spike potentials (SSP) and repetitive bursts of action potentials (RBAP), the previously characterized tapeworm modifications of the normal interdigestive myoelectric pattern. Results indicated that TCM initiated SSP, but not RBAP in the intestine of the uninfected rat. The SSP-inducing signal factor activity, present in TCM, was retained after boiling, prolonged freezing, proteinase treatment, and passage through a 10-kDa exclusion filter. The signal factor was soluble in the aqueous phase on lipid extraction. It was concluded that the SSP-inducing signal factor is a nonproteinaceous, heat-resistant, low-molecular weight, water soluble molecule.     

中缝隐核对兔奥迪氏括约肌肌电活动的影响

实验用电生理学和微量注射法观察了兔中缝隐核（NRO）对奥迪氏括约肌肌电活动的影响,动物禁食但自由饭水,18－24h手用乌拉坦（1.0g/kg)静脉麻醉,用双极康铜丝电极引导奥迪氏括约肌肌电,发现NRO内微注射谷氨酸（340mmol/L,0.4ul)可使奥迪氏括约肌肌电活动加强,与在NRO内微量注射生理盐水或者将谷氨酸（340mmol/L,0.4ul)注射到NRO以外的地方相比,具有显著差异（P＜0．01）,NRO 微量注射N-methy-D-aspartate(NM-DA)受体阻断剂氯胺酮（180mmol/L,0.1ul),可消除谷氨酸的效应,而将微量非NMDA受体阻断剂CNQX（2mmol/L,0.1ul)注入NRO,可使奥迪氏括约肌肌电加强,外周应用M－受体阻断剂阿托品（0.2mg/kg)或双侧颈部迷走神经切断,可阻断微量谷氨酸注射到NRO内所引起的效应,静脉注射α－受体阻断剂酚妥拉明（1.5mg/kg),心得安（1.5mg/kg)或自T3－4处切断脊髓,对NRO内微量注射谷氨酸的效应没有影响,结果提示,NRO对奥迪氏括约肌运行有调节作用,其中谷氨酸主要通过NMDA受体兴雷奥迪氏括约肌肌电活动,其传出途径是迷走神经和外周M受体。     

Action of tetanus toxin on cholinergic neuroblastoma X glioma hybrid cells: selective blockade of Ca spikes

We examined the effect of tetanus toxin on clonal neuroblastoma X glioma hybrid cells, NG108-15, by intracellular microelectrode studies of passive membrane electrical properties and action potentials generated under various conditions. Binding of tetanus toxin to the surface of the cells was demonstrated by indirect immunofluorescent staining but no morphological alteration was observed in tetanus toxin-treated cells under a phase contrast microscope. These is no significant difference between the tetanus toxin-treated and untreated cells in their passive electrical membrane properties, i.e. resting membrane potentials, input resistances, time constants and input capacities. Cells in 120 mM Na+, 2 mM Ca2+ salt solution showed Na spikes, and cells in high Ca2+ (30 mM), Na+-free salt solution showed Ca spikes in response to depolarizing current pulses. While the Na spike was not affected by tetanus toxin, the Ca spike was blocked by the toxin. The minimum dose of tetanus toxin for maximum suppression of the peak potential level of the Ca spike was 250 ng/ml. Addition of tetraethyl ammonium (TEA) to extracellular fluid enhanced the Ca spike in untreated cells. In toxin-treated cells, TEA did not alter the effect of tetanus toxin on the Ca spike. Blockade of the Ca spike by tetanus toxin could be detected even at low extracellular Ca2+ concentration (10 mM) by adding TEA to the extracellular fluid and adjusting the membrane potential to a steady hyperpolarized level (-80 mV) to ensure optimal and uniform electrical responses. The usefulness of NG108-15 hybrid cells for in vitro investigations on the mechanism of action of tetanus toxin was discussed.     

4-Aminopyridine-induced changes in the electrical and contractile activities of the gastric smooth muscle

Effects of 4-aminopyridine (4-AP) on the electrical and contractile activities of the fundus and antrum of the cat stomach were studied using the sucrose-gap technique. In the fundus, low concentrations of 4-AP (up to 1 mmol/l) induced membrane depolarization and appearance of spike potentials and phasic contractions. After preliminary administration of atropine, 4-AP produced an opposite effect: hyperpolarization and relaxation. On the background of tetrodotoxin (TTX) plus antagonists of cholinergic and adrenergic receptors, high concentrations of 4-AP (greater than 5 mmol/l) caused membrane depolarization and appearance of spike potentials and phasic contractions. In the antrum, 4-AP in low concentrations (up to 1 mmol/l) decreased both the amplitude and the duration of the second component of the plateau-action potential, as well as those of the phasic contractions. This effect decreased in the presence of adrenergic receptor antagonists and was abolished by TTX. On this background, high concentrations of 4-AP (greater than 5 mmol/l) led to the appearance of spike potentials superimposed on the second component of the plateau-action potentials, and to a further increase in the phasic contraction amplitudes. The present data suggest that 4-AP exerts its effects via an increase in neurotransmitter release (low concentrations) and/or directly on the smooth muscle cell membrane (high concentrations).     

NO对家兔Oddi括约肌肌电活动和血压的影响

应用３２只家兔观察一氧氮对Ｏｄｄｉ括约肌肌电和血压的影响。静脉注射ＮＯ合酶抑制剂Ｎ＾Ｇ－硝基－Ｌ－精氨酸,可见ＳＯ肌电振幅增大和血压升高,Ｌ－ＮＮＡ所致的肌电活动增强可Ｌ－精氨酸反转。     

Analysis of the modulating effect of catecholamines on electrogenesis in an isolated mechanoreceptor

Perfusion of isolated Pacinian corpuslces in the cat mesentery with solutions of dibutyryl-cAMP or theophylline caused an increase in spike activity against the background of a reduction in amplitude of receptor potentials and lowering of the threshold for spike generation. The opposite effect on mechanoreceptor electrical responses was found when catecholamines were used. It was postulated on the basis of these findings that the action of catecholamines on Pacinian corpuscles is accompanied by a fall in the cAMP level in the sensory nerve terminal. Noradrenalin caused a decrease in adenylate cyclase activity in receptor homogenates. The activating effect of noradrenalin on Na⁺, K⁺-ATPase, abolished by phentolamine but unchanged by propranolol, was demonstrated. The possible role of -adrenoreceptors in the modulating effect of catecholamines on electrical activity of Pacinian corpuscles is discussed.S. V. Kurashov Medical Institute, Ministry of Health of the RSFSR, Kazan'. Translated from Neirofiziologiya, Vol. 14, No. 2, pp. 158–163, March–April, 1982.     

Calcium dependence of electrical and mechanical activity in rat ileum examined by the sucrose-gap technique

1. Single sucrose gap recordings showed that spontaneous action potentials of rat ileal smooth muscle consisted of slow waves and superimposed spikes which generated rhythmic contractions. As external potassium was raised, the resting potential progressively depolarized.2. Calcium-free salines inhibited spontaneous mechanical activity and inhibited the plateau phase of the action potential, but spontaneous spike depolarizations persisted.3. Verapamil, nifedipine and diltiazem all inhibited spontaneous mechanical activity and the plateau phase of the action potential, while in addition diltiazem augmented spike amplitude.4. Mn ions also inhibited mechanical activity and the action potential plateau, without affecting spike activity while the calcium ionophore A23187 enhanced both mechanical and electrical activity with a pronounced effect on spike amplitude.5. These results are consistent with the view that the plateau phase of the ileal smooth muscle action potential is dependent upon an influx of extracellular calcium possibly through voltage dependent slow calcium channels.     

Excitatory beta-adrenoreceptors on enteral cholinergic interneurons of the large intestine and ileocecal sphincter]

Acute experiments were performed on the isolated intestinal loop, vascularly perfused with arterial blood by means of the constant flow perfusion pump. Contractile activity of the ileocecal sphincter and proximal parts of the large intestine was estimated by the maximal isometric tension and total (integrated) contractile activity. Isoprenaline (1-2 mg) induced contractile responses of the colonic segment and ileocecal sphincter. These responses were abolished or dramatically diminished by the blockade of beta-adrenoceptors, muscarinic, and nicotinic cholinergic receptors. Data obtained support the idea, that the large intestine and ileocecal sphincter have excitatory beta-adrenoceptors localized on cholinergic interneurones of the enteric nervous system.     

The motoricity cycle of the small intestine

The electrical spike activity of the small intestine at the gastroduodenal junction occurs as migrating myoelectric complexes (MMCs), initiated regularly at intervals of 90-100 min. in the adult sheep and of 20-30 min. in the neonate. This ultradian rhythm, generated by the enteric nervous system, may become identical in the adult and in the neonate, by the use of methysergide which interacts with 5-HT myenteric neurones. The results suggest a postnatal development of a serotoninergic inhibitory system, involved in the control of the basic rest-activity cycle of the small intestine.     

Integrative Synaptic Mechanisms in the Caudal Ganglion of the Crayfish

A study of activity recorded with intracellular micropipettes was undertaken in the caudal abdominal ganglion of the crayfish in order to gain information about central fiber to fiber synaptic mechanisms. This synaptic system has well developed integrative properties. Excitatory post-synaptic potentials can be graded, and synaptic potentials from different inputs can sum to initiate spike discharge. In most impaled units, the spike discharge fails to destroy the synaptic potential, thereby allowing sustained depolarization and multiple spike discharge following single pulse stimulation to an afferent input. Some units had characteristics which suggest a graded threshold for spike generation along the post-synaptic fiber membrane. Other impaled units responded to afferent stimulation with spike discharges of two distinct amplitudes. The smaller or "abortive" spikes in such units may represent non-invading activity in branches of the post-synaptic axon. On a few occasions one afferent input was shown to inhibit the spike discharge initiated by another presynaptic input.     

Inhibition of glucose-induced electrical activity by 4-hydroxytamoxifen in rat pancreatic beta-cells.

The antioestrogen 4-hydroxytamoxifen (10 or 2 microM) abolished the generation of action potentials and repolarized the membrane potential in rat pancreatic beta-cells stimulated by 16 mM glucose. This effect was slowly reversible upon withdrawal of the drug. In cells stimulated by tolbutamide (100 microM), application of 4-hydroxytamoxifen again inhibited action-potential generation but failed to repolarize the membrane potential. 4-Hydroxytamoxifen inhibited voltage-sensitive calcium currents and activity of the volume-sensitive anion channel. The drug had no effect on net K(+) conductance of the cell. Insulin release stimulated by either glucose or tolbutamide was inhibited by 4-hydroxytamoxifen. It is concluded that 4-hydroxytamoxifen impairs beta-cell electrical and secretory activity by inhibiting calcium and anion channel currents. This effect could contribute towards hyperglycaemia during therapy with tamoxifen, of which 4-hydroxytamoxifen is the major metabolite. This study also reveals differences between the depolarizing actions of glucose and tolbutamide in the beta-cell.