Distribution of nitric oxide synthase and vasoactive intestinal polypeptide immunoreactivity in the sphincter of Oddi and duodenum of the possum

Expression and alteration of BKCa channels in the sphincter of Oddi's from rabbits with hypercholesterolemia

This study aimed to investigate the expression and function of BK_Ca channels in the Sphincter of Oddi (SO) in a rabbit model of hypercholesterolemia (HC). New Zealand white rabbits were randomly divided into 2 groups: the control group was fed standard chow (n = 18) whereas the high-cholesterol group was fed cholesterol-enriched chow containing 1.5% cholesterol (n = 18). The serum cholesterol level was significantly greater in the HC groups than in the control group, but there was no significant difference in body weight between the control and HC groups. Although the total protein expression of BK_Ca α- and β₁-subunit was not significantly different between the control and HC groups, the Tyr-phosphorylation of BK_Ca α-subunit was significantly decreased in the HC group than in the control group. In addition, hypercholesterolemia significantly increased Acetylcholine (ACh)-induced contraction of the SO rings. Pretreatment with 30 μM NS1619, a BK_Ca channel agonist, significantly reduced ACh-induced contraction of the SO rings in HC rabbits. Moreover, pretreatment with 100 μM Na₃OV₄, a protein tyrosine phosphatase inhibitor, significantly reduced ACh-induced contraction of the SO rings in HC rabbits, whereas it significantly increased upon pretreating with 10 μM Genistein, a tyrosine kinase inhibitor. Whole-cell patch clamp recordings showed that BK_Ca current density was significantly lower in SOSMCs from HC group than that from control group. Our findings suggest that hypercholesterolemia-induced downregulation of BK_Ca channel, and Tyr-phosphorylation of BK_Ca α-subunit may contribute to the hyperresponsiveness of the SO ring in HC rabbits.

Biliary tract pressure before and after endoscopic papillary balloon dilation treatment for common bile duct stones

AIM: To determine the biliary tract pressure before and after endoscopic papillary balloon dilation (EPBD) treatment for common bile duct stones.

METHODS: Clinical data for 96 patients with common bile duct stones who successfully underwent EPBD and biliary manometry from September 2011 to January 2014 were retrospectively analyzed.

RESULTS: Biliary tract pressure was significantly higher in patients with common bile duct stones than in healthy controls, which could be relieved by EPBD. Biliary tract pressure in patients who underwent cholecystectomy was higher than in patients with gallbladder stones. After operation, there were 2 cases of hyperamylasemia, 2 cases of acute pancreatitis and 2 cases of mild cholangitis, all of which resolved after non-operative treatment. The incidence of complications was 6.3% (6/96). No serious complications occurred.

CONCLUSION: EPBD treatment can effectively solve biliary obstruction and reduce biliary pressure.

Effects of cholecystectomy on the changes of motility of Beagle dogs' sphincter of Oddi

PURPOSE

To observe the effect of cholecystectomy on the changes of motion pattern of Beagle dogs' sphincter of Oddi (SO), and investigate the modulatory role of nitric oxide (NO) and cholecystokinin (CCK) in the regulation of SO.

METHODS

Pressure of common bile duct, SO motility, response to bolus injections of cholecystokinin (CCK, 20 ng/kg and 100 ng/kg), basal pressure (BP) and phasic contraction amplitude (PCA) were measured respectively by manometry in six Beagle dogs before and after cholecystectomy.

RESULTS

After cholecystectomy, the pressure and diameter of common bile ducts (CBD) was significantly increased (p<0.01); BP and phasic contraction frequency (PCF) were also increased, however, no significant differences were found between the two groups; the SO motilities was not significantly changed. The relaxation responded to physiological dose of CCK (20ng/kg) was decreased, while bolus-dose of CCK (100ng/kg) induced rapid contractions and decreased PCA after cholecystectomy. The regulation pattern of SO pressure modulated by NO and its inhibitor had changed after cholecystectomy.

CONCLUSION

After cholecystectomy in Beagle dogs, no obviously change of motion pattern of SO was observed through self-compensation, but these compensations may lead to some changes of regulation pattern of CCK and NO on SO.

Roles of sphincter of Oddi motility and serum vasoactive intestinal peptide, gastrin and cholecystokinin octapeptide

AIM: To investigate roles of sphincter of Oddi (SO) motility played in pigment gallbladder stone formation in model of guinea pigs.

METHODS: Thirty-four adult male Hartley guinea pigs were divided randomly into two groups: the control group and pigment stone group. The pigment stone group was divided into 4 subgroups with 6 guinea pigs each according to time of sacrifice, and were fed a pigment lithogenic diet and sacrificed after 3, 6, 9 and 12 wk. SO manometry and recording of myoelectric activity of the guinea pigs were obtained by multifunctional physiograph at each stage. Serum vasoactive intestinal peptide (VIP), gastrin and cholecystokinin octapeptide (CCK-8) were detected at each stage in the process of pigment gallbladder stone formation by enzyme-linked immunosorbent assay.

RESULTS: The incidence of pigment gallstone formation was 0%, 0%, 16.7% and 66.7% in the 3-, 6-, 9- and 12-wk group, respectively. The frequency of myoelectric activity decreased in the 3-wk group. The amplitude of myoelectric activity had a tendency to decrease but not significantly. The frequency of the SO decreased significantly in the 9-wk group. The SO basal pressure and common bile duct pressure increased in the 12-wk group (25.19 ± 7.77 mmHg vs 40.56 ± 11.81 mmHg, 22.35 ± 7.60 mmHg vs 38.51 ± 11.57 mmHg, P < 0.05). Serum VIP was significantly elevated in the 6- and 12-wk groups and serum CCK-8 was decreased significantly in the 12-wk group.

CONCLUSION: Pigment gallstone-causing diet may induce SO dysfunction. The tension of the SO increased. The disturbance in SO motility may play a role in pigment gallstone formation, and changes in serum VIP and CCK-8 may be important causes of SO dysfunction.

Effect of somatostatin on human sphincter of Oddi motility

Native somatostatin is a gut hormone and neuropeptide, widely distributed in the nervous and gastrointestinal system, and has a broad range of biological actions. In gastrointestinal tract (GIT), somatostatin is mainly produced by the delta cells of the pancreas and gastrointestinal mucosal. The inhibitory effects of somatostatin on gastrointestinal motility and hormone secretion are mediated by a family of G protein-coupled receptors: the somatostatin receptors (SSTR1-5). The sphincter of Oddi (SO) located near the duodenum papillae is an anatomically and functionally distinct organ, SO motility is controlled and regulated by nerve, hormone and interstitial cells of Cajal. The effect of somatostatin on SO motility is still controversial. This article reviewed effect of somatostatin on human sphincter of oddi motility.

Sphincter of Oddi function in the Australian brush-tailed possum is inhibited by intragastric ethanol

The role of sphincter of Oddi (SO) function in alcoholic acute pancreatitis (AP) is unclear. We aimed to compare the effect of i.v. and intragastric (IG) ethanol on SO function (i.e. trans-sphincteric flow; TSF) and investigate possible neural mechanisms. The involvement of gastric mucosal damage was also investigated by pretreatment with pantoprazole. In anaesthetized Australian possums, blood pressure (BP), TSF and blood ethanol concentrations were measured after i.v. or IG ethanol. Possums were subjected to acute vagotomy, atropine, L-nitro arginine methyl ester (L-NAME) or pantoprazole pretreatment prior to IG ethanol. BP was not significantly altered by ethanol. Ethanol decreased TSF in a dose and route-dependent manner. The lowest dose of IG ethanol reduced TSF but this response was not duplicated by i.v. ethanol producing the same blood ethanol concentrations. Acute vagotomy, atropine or L-NAME pretreatment blocked the ethanol-induced decrease in TSF and simultaneously suppressed the blood ethanol concentration. Pantoprazole pretreatment reduced the TSF response and blood ethanol concentrations implicating mechanisms induced by gastric mucosal damage. We conclude that ethanol (and/or its metabolites) reduces TSF via humoral and neural mechanisms involving vagal pathways, muscarinic receptors and nitric oxide. Reduced TSF could contribute to the onset of AP.

Exogenous purines induce differential responses in the proximal and distal regions of the possum sphincter of Oddi

1. The aim of this study was to compare the effect of exogenous ATP and adenosine on spontaneous motility of the proximal and distal regions of the possum sphincter of Oddi (SO). 2. ATP or adenosine (1 microm-1 mm) was applied to distal-SO or proximal-SO muscle rings in organ baths in the absence or presence of tetrodotoxin (TTX) or P1/P2 antagonists. 3. Both ATP and adenosine altered spontaneous activity, predominantly in proximal-SO rings. 4. Exogenous ATP induced a bi-phasic response consisting of a brief TTX-sensitive excitatory component, and a longer-lasting TTX-insensitive inhibitory component. 5. The excitatory ATP response likely involves P2X receptors, whereas the late inhibitory response likely involves P2Y receptors. 6. Exogenous adenosine decreased spontaneous SO activity, via a TTX-insensitive mechanism. 7. Exogenous purines modulate SO motility, acting primarily in the proximal region of the SO, via neural and non-neural mechanisms and multiple purine receptor subtypes.

Exogenous adenosine triphosphate and adenosine stimulate proximal sphincter of oddi motility via neural mechanisms in the anesthetized Australian possum

We aimed to determine if exogenous adenosine triphosphate or adenosine modulated sphincter of Oddi motility and involved neural mechanisms. Sphincter of Oddi motility was recorded in anesthetized possums by manometry. Adenosine triphosphate or adenosine (1 microM-10 mM) was applied topically to the sphincter before and after pretreatment with tetrodotoxin, hexamethonium, atropine, or Nomega-nitro-L-arginine methyl ester. Sphincter contraction amplitude and frequency were quantified. Adenosine triphosphate induced a concentration-dependent increase in proximal sphincter contraction amplitude and frequency (P < 0.05). This response was reduced by tetrodotoxin and atropine but enhanced by hexamethonium and Nomega-nitro-L-arginine methyl ester. Adenosine concentration dependently increased proximal sphincter contraction amplitude (P < 0.05) only. This response was reduced by tetrodotoxin, atropine, and Nomega-nitro-L-arginine methyl ester, whereas hexamethonium had no effect. We conclude that exogenous adenosine triphosphate and adenosine stimulate proximal sphincter of Oddi motility via neural mechanisms, involving cholinergic motor neurons. Adenosine triphosphate may further modulate sphincter motility via nicotinic and nitrergic pathways.

Decreased distribution of nitric oxide synthase and vasoactive intestinal polypeptide positive nerve cells in the sphincter of Oddi in humans with pancreatobiliary diseases

To better understand the relationship between innervation in the sphincter of Oddi and pancreatobiliary diseases, nerve cells which possess nitric oxide synthase (NOS) and/or vasoactive intestinal polypeptide (VIP) were studied immunohistochemically in the sphincter of Oddi and duodenum of humans. Specimens from autopsies included 11 cases with pancreatobiliary diseases and 7 cases without such diseases. An elaborate nerve network was revealed with an anti-S-100 antibody in the sphincter of Oddi and duodenum of all specimens. In the sphincter of Oddi of the control group, approximately 47% of the myenteric nerve cells were NOS positive, whereas 54% were VIP positive. Of the NOS positive nerve cells, 21% were also VIP positive. In contrast, 11% of the nerve cells in the sphincter of Oddi of the disease group were NOS positive while 32% were VIP positive. Within the duodenal myenteric plexus of the control group, 35% of all nerve cells were NOS positive while 40% was VIP positive; among them, 23% of the NOS positive cells were VIP positive. Similar results were observed in the duodenum of the disease group. These data indicate that abundant NOS and VIP positive innervation is present in the sphincter of Oddi and duodenum in humans. The lower proportion of NOS positive or VIP positive nerve cells of the disease group may suggest an inadequacy of the sphincter of Oddi to relax.

Gastrointestinal Function Regulation by Nitrergic Efferent Nerves

Gastrointestinal (GI) smooth muscle responses to stimulation of the nonadrenergic noncholinergic inhibitory nerves have been suggested to be mediated by polypeptides, ATP, or another unidentified neurotransmitter. The discovery of nitric-oxide (NO) synthase inhibitors greatly contributed to our understanding of mechanisms involved in these responses, leading to the novel hypothesis that NO, an inorganic, gaseous molecule, acts as an inhibitory neurotransmitter. The nerves whose transmitter function depends on the NO release are called "nitrergic", and such nerves are recognized to play major roles in the control of smooth muscle tone and motility and of fluid secretion in the GI tract. Endothelium-derived relaxing factor, discovered by Furchgott and Zawadzki, has been identified to be NO that is biosynthesized from l-arginine by the constitutive NO synthase in endothelial cells and neurons. NO as a mediator or transmitter activates soluble guanylyl cyclase and produces cyclic GMP in smooth muscle cells, resulting in relaxation of the vasculature. On the other hand, NO-induced GI smooth muscle relaxation is mediated, not only by cyclic GMP directly or indirectly via hyperpolarization, but also by cyclic GMP-independent mechanisms. Numerous cotransmitters and cross talk of autonomic efferent nerves make the neural control of GI functions complicated. However, the findingsrelated to the nitrergic innervation may provide us a new way of understanding GI tract physiology and pathophysiology and might result in the development of new therapies of GI diseases. This review article covers the discovery of nitrergic nerves, their functional roles, and pathological implications in the GI tract.

The sphincter of Oddi: understanding its control and function

The most common functional disorders of the biliary tract and pancreas are associated with disordered motility of the sphincter of Oddi (SO). The SO is a neuromuscular structure located at the junction of the bile and pancreatic ducts with the duodenum. The primary functions of the SO are to regulate the delivery of bile and pancreatic juice into the duodenum, and to prevent the reflux of duodenal contents into the biliary and pancreatic systems. Disordered motility of the SO leads to the common and painful clinical conditions of SO dysfunction and acute pancreatitis. In order to understand normal SO motility, studies have been performed addressing SO function, control of spontaneous SO activity, responses to bioactive agents, SO innervation, and reflexes with other gastrointestinal organs. These studies have led to the current understanding of how the SO functions and may permit the development of targeted therapy for SO dysfunction and acute pancreatitis. This review summarizes the current knowledge regarding the control and regulation of SO motility, highlighting laboratory based and clinical research performed over the last 5 years.

Innervation of the extrahepatic biliary tract

The extrahepatic biliary tract is innervated by dense networks of extrinsic and intrinsic nerves that regulates smooth muscle tone and epithelial cell function of extrahepatic biliary tree. Although these ganglia are derived from the same set of precursor neural crest cells that colonize the gut, they exhibit structural, neurochemical, and physiological characteristics that are distinct from the neurons of the enteric nervous system. Gallbladder neurons are relatively inexcitable, and their output is driven by vagal inputs and modulated by hormones, peptides released from sensory fibers, and inflammatory mediators. Gallbladder neurons are cholinergic and they can express a number of other neural active compounds, including substance P, galanin, nitric oxide, and vasoactive intestinal peptide. Sphincter of Oddi (SO) ganglia, which are connected to ganglia of the duodenum, appear to be comprised of distinct populations of excitatory and inhibitory neurons, based on their expression of choline acetyltransferase and substance P or nitric oxide synthase, respectively. While SO neurons likely receive vagal input and their activity is modulated by release of neuropeptides from sensory fibers, a significant source of excitatory synaptic input to these cells arise from the duodenum. This duodenum-SO circuit is likely to play an important role in the coordination of SO tone with gallbladder motility in the process of gallbladder emptying. Now that we have gained a relatively thorough understanding of the innervation of the biliary tree under healthy conditions, the way is paved for future studies of altered neural function in biliary disease.

Electrical activation of common bile duct nerves modulates sphincter of Oddi motility in the Australian possum

BACKGROUND

Sphincter of Oddi (SO) motility is regulated by extrinsic and intrinsic nerves. The existence of neural circuits between the SO and the proximal extrahepatic biliary tree has been reported, but they are poorly understood. Using electrical field stimulation (EFS), we determined if a neural circuit exists between the common bile duct (CBD) and the SO in anaesthetized Australian brush-tailed possums.

METHODS

The gallbladder, cystic duct or CBD were subjected to EFS with a stimulating electrode. Spontaneous SO phasic waves were measured by manometry.

RESULTS

EFS at sites on the distal CBD (12-20 mm proximal to the SO), but less commonly at more proximal CBD, evoked a variety of responses consisting of an excitatory and/or inhibitory phase. Bi-phasic responses consisting of an excitation followed by inhibition were the most common. Tri-phasic responses were also observed as well as excitation or inhibition only. These evoked responses were blocked by topical application of local anaesthetic to the distal CBD or transection of the CBD. EFS at sites on the gallbladder body, neck or cystic duct did not consistently evoke an SO response. Pretreatment with atropine or guanethidine reduced the magnitude of the evoked response by about 50% (p<0.05), pretreatment with hexamethonium had no consistent effect and pretreatment with a nitric oxide synthase inhibitor increased the response.

DISCUSSION

A neural circuit(s) between the SO and the distal CBD modulates SO motility. Damage to this area of the CBD during bile duct exploration surgery could adversely affect SO motility.

Highly selective iNOS inhibition and sphincter of Oddi motility in the Australian possum

AIM

Inducible nitric oxide synthase (iNOS) plays a major role in acute pancreatitis. Selective inhibitors of iNOS are being developed as therapeutic agents. Sphincter of Oddi (SO) dysfunction may cause pancreatitis and nitric oxide is necessary for SO relaxation. A new highly selective iNOS inhibitor, AR-C102222AA (AR-C), is evaluated together with the established iNOS inhibitor, L-N(6)-(1-iminoethyl)lysine (L-NIL), and the selective neuronal nitric oxide synthase (nNOS) blocker S-methyl-l-thiocitrulline (SMTC).

METHODS

In anaesthetized Australian Brush-tailed possums, the effect of topical, i.v. or i.a. administration of these drugs was evaluated on spontaneous SO motility, blood pressure (BP) and pancreatic vascular perfusion. SO motility was recorded by manometry and pancreatic vascular perfusion by laser Doppler fluxmetry. Also, the effect of SMTC and AR-C on electrical field stimulation (EFS)-induced non-cholinergic non-adrenergic (NANC) SO relaxation in vitro was evaluated.

RESULTS

Infusion of AR-C (0.1-30 micromol kg(-1)) increased SO contraction frequency (P = 0.026) only at the two highest doses. L-NIL infusion (0.15 to 14.7 micromol kg(-1)) also increased SO contraction frequency at 8.8 micromol kg(-1) (P < 0.05) and reduced SO contraction amplitude at the two highest doses (P < 0.05). SMTC injections (0.5 nmol-2.4 micromol) produced a dose-dependent increase in SO contraction frequency (P = 0.009), but no effect was seen on the other parameters. In vitro SMTC (40-400 microm) inhibited EFS-induced NANC relaxation in a dose-dependent manner (P < 0.0005). In contrast AR-C (10-500 microm) had no effect on EFS-induced NANC relaxation (P > 0.05).

CONCLUSIONS

At low doses, AR-C does not effect SO motility or EFS-induced NO mediated relaxation. However, high doses of AR-C and L-NIL in vivo influenced SO motility by inhibiting nNOS activity and these effects need be considered in relation to therapeutic doses of this agent.

The possum sphincter of Oddi pumps or resists flow depending on common bile duct pressure: a multilumen manometry study

The sphincter of Oddi (SO) regulates trans-sphincteric flow (TSF) by acting primarily as a pump or as a resistor in specific species. We used the Australian possum SO, which functions similarly to the human SO, to characterize SO motility responses to different common bile duct (CBD) and duodenal pressures. Possum CBD, SO and attached duodenum (n= 18) was mounted in an organ bath. External reservoirs were used to impose CBD (0-17 mmHg) and duodenal (0, 4, 7 mmHg) pressure. Spontaneous SO activity was recorded using four-lumen pico-manometry and TSF was measured gravimetrically. Temporal analysis of manometric and TSF recordings identified three functionally distinct biliary-SO regions, the proximal-SO (juxta-CBD), body-SO and papilla-SO. At CBD pressures < 3 mmHg the motor activity of these regions was coordinated to pump fluid. Proximal-SO contractions isolated fluid within the body-SO. Peristaltic contraction through the body-SO pumped this fluid through the papilla-SO (17-27 microl contraction), which opened to facilitate flow. CBD pressure > 3.5 mmHg resulted in progressive changes in TSF to predominantly passive 'resistor'-type flow, occurring during proximal-SO-body-SO quiescence, when CBD pressure exceeded the pressure at the papilla-SO. Progression from pump to resistor function commenced when CBD pressure was 2-4 mmHg greater than duodenal pressure. These results imply that TSF is dependent on the CBD-duodenal pressure difference. The papilla-SO is pivotal to TSF, relaxing during proximal-SO-body-SO pumping and closing during proximal-SO-body-SO quiescence. The pump function promotes TSF at low CBD pressure and prevents bile stasis. At higher CBD pressure, the papilla-SO permits TSF along a pressure gradient, thereby maintaining a low pressure within the biliary tract.

Acalculous biliary pain: new concepts for an old entity

Biliary pain is commonly reported in household surveys with the presumed cause being gallstones. When gallstones are absent or other abnormalities as a potential cause of similar pain do not exist, a different approach is necessary. Although trans-abdominal ultrasound can detect stones down to 3-5 mm, the advent of endoscopic ultrasound provides an even better definition for microlithiasis of < 3 mm. Duodenal aspiration of bile can further detect cholesterol microlithiasis or bilirubin granules, another potential source of biliary-type pain and perhaps even pancreatitis. Only in this way can acalculous gallbladder disease be clearly defined. The percentage of cholecystokinin-stimulated gallbladder emptying has been reputed to be the most sensitive diagnostic test for 'biliary dyskinesia', but abnormality of gallbladder emptying can be due to a smooth muscle defect of the gallbladder itself or heightened tone in the sphincter of Oddi. The value of surgical intervention has not been clearly established. The advent of laparoscopic cholecystectomy, however, has increased the number of patients with acalculous biliary disease who undergo surgery. Surgery is best done using impaired gallbladder emptying as the criterion for operation with improved outcome. Often, following cholecystectomy, biliary pain does not resolve the so-called 'post cholecystectomy syndrome'. Absence of the gallbladder as a pressure reservoir leaves the sphincter of Oddi as the prime determinant of bile duct pressure. Sphincter of Oddi dysfunction also exists in patients with an intact biliary tract and may become evident following cholecystectomy. Biliary manometry has clarified who might benefit from sphincterotomy. Choledochoscintigraphy is a non-invasive preliminary test. Advent of visceral hypersensitivity and better definition of this entity has shown, that in some of these patients with type III sphincter of Oddi, dysfunction appears to reside in duodenal hyperalgesia. It is clear that improved criteria are required to perform gallbladder emptying and better techniques to detect visceral hypersensitivity. Nonetheless, functional biliary pain in the absence of gallstone disease is a definite entity and a challenge for clinicians.

Effects of bioactive agents on biliary motor function

Our understanding of biliary motility under normal and pathophysiologic conditions is still incomplete, but there have been recent advances. Of particular interest are the mechanisms involved in gallbladder filling and emptying, with a focus on understanding the processes underlying impaired gallbladder emptying leading to gallbladder dyskinesia and the formation of gallstones or cholecystitis. The sphincter of Oddi (SO) is a complex neuromuscular structure. Recent studies have attempted to unravel the specific neural or hormonal mechanisms operating under normal physiologic conditions and those that may lead to SO dysfunction. Furthermore, new research fronts are emerging, including the role of leptin in obese patients with impaired biliary motility and the action of electroacupuncture for possible treatment of SO dysfunction. This review illustrates the broad front of current research regarding the effects of bioactive agents on biliary motility, including enteric hormones, nitric oxide, opioids, inflammatory mediators, leptin, protease inhibitors, neurotransmitters, and electroacupuncture.

Distribution of constitutive nitric oxide synthase in the jejunum of adult rat

AIM: To study the distribution of the constitutive nitric oxide synthase (NOS) in the jejunum of adult rat.

METHODS: The distribution of endothelial NOS (eNOS) was detected by immunohistochemistry. Immunofluorescence histochemical dual staining technique were used for studying the distribution of neuronal NOS (nNOS) and eNOS. The dual stained slides were observed under a confocal laser scanning microscope.

RESULTS: Positive neuronal NOS (nNOS) and endothelial NOS (eNOS) cells were found to be distributed in lamina propria of villi, and the epithelial cell was not stained. eNOS was mainly located in submucosal vascular endothelia, while nNOS was mainly situated in myenteric plexus. Some cells in the villi had both nNOS and eNOS. More than 80% of the cells were positive for both nNOS and eNOS, the rest cells were positive either for nNOS or for eNOS.

CONCLUSION: The two constitutive nitric oxide synthases are distributed differently in the jejunum of rat. nNOS distributed in myenteric plexus is a neurotransmitter in the non-adrenergic non-cholinergic (NANC) inhibitory nerves. eNOS distributed in endothelial and smooth muscle cells of blood vessels plays vasodilator role. eNOS and nNOS are coexpressed in some cells of lamina propria of villi. NO generated by those NOS is very important in the physiological and pathological process of small intestine.

Induction of duodenal motility activates the sphincter of Oddi (SO)-duodenal reflex in the Australian possum in vitro

1 The aim of this study was to determine if stimulation of duodenal motility by duodenal fluid distension or by administration of carbachol, activates the sphincter of Oddi-duodenal reflex, in an in vitro preparation from the Australian possum. 2 Duodenal distension was achieved by infusion of Krebs solution (0-8 cm H2O). In separate experiments, the sphincter of Oddi (SO) was partitioned from the duodenum and carbachol (10(-7) - 5 x 10(-6) M) added to the duodenal compartment. 3 Fluid distension increased duodenal motility to 120-600% of control activity. These treatments induced increased SO motility (to 120-390% of control) in six preparations, reduced activity (to 60% of control) in one and no response in another. 4 Addition of carbachol to the duodenal compartment resulted in increased duodenal motility. SO motility was increased in seven preparations, reduced in another two and no response were evoked in two others. All SO responses were blocked by tetrodotoxin pretreatment. 5 These data suggest that the SO receives inputs from duodenal mechano and/or stretch receptors resulting in excitatory or inhibitory responses, with the excitatory response dominating. These findings support the role for the SO-duodenal reflex in preventing duodenobiliary/pancreatic reflux during periods of elevated duodenal activity.

Characterization of circular muscle motor neurons of the duodenum and distal colon in the Australian brush-tailed possum

The motor innervation of the duodenum and distal colon remains uncharacterized within the same species. Our aim was to compare the projections and neurochemical properties of duodenal and distal colon circular muscle motor neurons. Circular muscle motor neurons were retrogradely traced by using a neural tracer in vitro, processed for choline acetyltransferase (ChAT) and nitric oxide synthase (NOS) immunoreactivity and then visualized by using indirect immunofluorescence. A mean of 372 +/- 64 and 156 +/- 23 neurons (mean +/- SEM) were tracer-labeled within the duodenum and colon, respectively. The ChAT+/NOS- neurons comprised 57.6 +/- 6.6% and 39.6 +/- 4.4% of all labeled cells in the duodenum and colon, respectively, and projected mainly in the oral direction. Of all labeled cells, the ChAT-/NOS+ neurons comprised 8.5 +/- 2.3% in the duodenum and 46.6 +/- 5.0% in the distal colon and projected mainly in the anal direction. Of the remainder, 20.6 +/- 5.0% and 8.2 +/- 2.4% were ChAT+/NOS+ and 13.2 +/- 0.9% and 5.6 +/- 1.4% were ChAT-/NOS- in the duodenum and distal colon, respectively. Within both regions, the distribution of the ChAT+/NOS- and ChAT-/NOS+ neurons are consistent with the ascending excitatory and descending inhibitory reflexes. The proportion of ChAT-/NOS+ neurons is greater within the colon in comparison with the duodenum. A considerable proportion of duodenal motor neurons were ChAT+/NOS+ and ChAT-/NOS-. These two classes may underlie nonperistaltic motor patterns, which predominate within the duodenum. These findings demonstrate regional differences in the innervation of intestinal circular muscle.