Duodenal neurons provide nicotinic fast synaptic input to sphincter of Oddi neurons in guinea pig

The enteric nervous system

Of all the organ systems in the body, the gastrointestinal tract is the most complicated in terms of the numbers of structures involved, each with different functions, and the numbers and types of signaling molecules utilized. The digestion of food and absorption of nutrients, electrolytes, and water occurs in a hostile luminal environment that contains a large and diverse microbiota. At the core of regulatory control of the digestive and defensive functions of the gastrointestinal tract is the enteric nervous system (ENS), a complex system of neurons and glia in the gut wall. In this review, we discuss 1) the intrinsic neural control of gut functions involved in digestion and 2) how the ENS interacts with the immune system, gut microbiota, and epithelium to maintain mucosal defense and barrier function. We highlight developments that have revolutionized our understanding of the physiology and pathophysiology of enteric neural control. These include a new understanding of the molecular architecture of the ENS, the organization and function of enteric motor circuits, and the roles of enteric glia. We explore the transduction of luminal stimuli by enteroendocrine cells, the regulation of intestinal barrier function by enteric neurons and glia, local immune control by the ENS, and the role of the gut microbiota in regulating the structure and function of the ENS. Multifunctional enteric neurons work together with enteric glial cells, macrophages, interstitial cells, and enteroendocrine cells integrating an array of signals to initiate outputs that are precisely regulated in space and time to control digestion and intestinal homeostasis.

Using a Whole-mount Immunohistochemical Method to Study the Innervation of the Biliary Tract in Suncus murinus

This work describes the whole-mount immunohistochemistry staining method in detail, using neurofilament protein antibody to label the innervation of the biliary tract in Suncus murinus (S. murinus ). First, the specimen was dissected from S. murinus and fixed in 4% paraformaldehyde (PFA). Second, an enzymatic treatment and potential endogenous peroxidase inactivation were performed. The specimen was then exposed to the primary antibody, anti-neurofilament protein antibody, for 3-6 days. It was then incubated with the secondary antibody conjugated with horseradish peroxidase. The color reaction was revealed by reacting the specimen with a 3,3'-diaminobenzidine (DAB) substrate. This method can be applied to analyze the innervation of all visceral organs. Furthermore, this protocol can also be adapted to test other neuronal antibodies, but optimization of the antibodies should be done first. This method was originally introduced by Kuratani and Tanaka^1,2,3.

Intestinal dysmotility and its relationship to sphincter of Oddi dysfunction

Sphincter of Oddi dysfunction (SOD) is a clinical entity that presents with pain as the predominant symptom, and patients may require invasive procedures for its proper diagnosis. Those with abnormal sphincter of Oddi manometry (SOM) are commonly treated with endoscopic ablation of the sphincter. The results of such therapy vary and depend on the type of SOD. In the past several years, evidence has emerged of an association between SOD, intestinal dysmotility, and visceral hyperalgesia. This article reviews the evidence supporting such an association.

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.

Effect of cholesterol liposomes on calcium mobilization in muscle cells from the rabbit sphincter of Oddi

AIM: To analyze the influence of cholesterol liposome on the Ca²⁺ mobilization of cultured muscle cells in rabbit sphincter of Oddi’s.

METHODS: New Zealand rabbit was sacrificed and the sphincter of Oddi (SO) segement was obtained aseptically. The SO segment was cut into pieces and cultured in DMEM solution. Then the smooth muscle cells were subcultured, and the 4th-7th passage cells were used for further investigation. The intracellular Ca²⁺ increase was measured under confocal microscope after the addition of 20 mmol·L^-1 KCl, 10^-7 mol·L^-1 acetylcholine and 10^-7 mol·L^-1 cholecystokinin, and different antagonists were added to analyze the Ca²⁺ mobilization pathway. After the cells were incubated with 1 g·L^-1 cholesterol liposome (CL)(molar ratio was-2:1), the intracellular Ca²⁺ increase was measured again to determine the effect of CL on cellular Ca²⁺ mobilization.

RESULTS: The resting cellular calcium concentration of cultured SO cell was 108 nmol·L^-1± 21 nmol·L^-1. The intracellular Ca²⁺ increases induced by 20 mmol·L^-1 KCl, 10^-7 mol·L^-1 ACh and 10^-7 mol·L^-1 CCK were 183% ± 56%, 161% ± 52% and 130% ± 43%, respectively. When the extracellular Ca²⁺ was eliminated by 2 mmol·L^-1 EGTA and 5 μmol·L^-1 verapamil, the intracellular Ca²⁺ increases induced by KCl, ACh and CCK were 20% ± 14%, 82% ± 21% and 104% ± 23%, respectively. After the preincubation with heparin, the Ca²⁺ increases were 62% ± 23% and 23% ± 19% induced by ACh and CCK, as for preincubation with procaine they were 72% ± 28% and 85% ± 37% induced by ACh and CCK, respectively. Pretreatment with CL for 18 h, the resting cellular Ca²⁺ concentration elevated to 152 nmol·L^-1± 26 nmol·L^-1, however, the cellular Ca²⁺ increase percentages in response to these agonists were 67% ± 32%, 56% ± 33% and 34% ± 15%.

CONCLUSION: KCl elicite the SO cellular Ca²⁺ increase depends on influx of extracellular Ca²⁺, ACh evoked the SO celllular Ca²⁺ increase is through the mobilization of intracellular Ca²⁺ pool and influx of extracellular Ca²⁺ as well, CCK excites the SO cells mainly through mobilization of intracellular IP3-sensitive Ca²⁺ store. After the incorporation with cholesterol liposome, KCl,ACh and CCK induced cellular Ca²⁺ increase percentages decreased.

Tachykinins mediate slow excitatory postsynaptic transmission in guinea pig sphincter of Oddi ganglia

Intracellular recording techniques were used to test whether tachykinins could be mediators of slow excitatory postsynaptic potentials (EPSPs) in guinea pig sphincter of Oddi (SO) ganglia. Application of the tachykinin substance P (SP) onto SO neurons caused a prolonged membrane depolarization that was reminiscent of the slow EPSP in these cells. Pressure ejection of the neurokinin 3 (NK3) receptor-specific agonist senktide caused a similar depolarization; however, no responses were detected on application of NK1 or NK2 receptor agonists. The NK3 receptor antagonist SR-142801 (100 nM) significantly inhibited both SP-induced depolarization and the stimulation-evoked slow EPSP, as did NK3 receptor desensitization with senktide. Capsaicin, which causes the release of SP from small-diameter afferent fibers, induced a depolarization that was similar to the evoked slow EPSP in both amplitude and duration. The capsaicin-induced depolarization was significantly attenuated in the presence of SR-142801. These data indicate that tachykinins, released from extrinsic afferent fibers, act via NK3 receptors to provide slow excitatory synaptic input to SO neurons.