Sphincteric function

Papasova, M

doi:10.1002/cphy.cp060126

Cited by 7 publications

(5 citation statements)

References 252 publications

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“…Preganglionic neurons are cholinergic and activate ACh nicotinic receptors located in the noradrenergic postganglionic neurons. These adrenergic fibres can innervate the LOS smooth muscle directly or via the enteric motor neurons ( Papasova, 1989 ). The sympathetic response of the LOS may vary according to species.…”

Section: Motor Neuronal Anatomy Of the Losmentioning

confidence: 99%

Regulation of basal tone, relaxation and contraction of the lower oesophageal sphincter. Relevance to drug discovery for oesophageal disorders

Farré¹,

Sifrim²

2008

British J Pharmacology

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The lower oesophageal sphincter (LOS) is a specialized region of the oesophageal circular smooth muscle that allows the passage of a swallowed bolus to the stomach and prevents the reflux of gastric contents into the oesophagus. The anatomical arrangement of the LOS includes semicircular clasp fibres adjacent to the lesser gastric curvature and sling fibres following the greater gastric curvature. Such anatomical arrangement together with an asymmetric intrinsic innervation and distinct proportion of neurotransmitters in both regions produces an asymmetric pressure profile. The LOS tone is myogenic in origin and depends on smooth muscle properties that lead to opening of L-type Ca 2 þ channels; however it can be modulated by enteric motor neurons, the parasympathetic and sympathetic extrinsic nervous system and several neurohumoral substances. Nitric oxide synthesized by neuronal NOS is the main inhibitory neurotransmitter involved in LOS relaxation. Different putative neurotransmitters have been proposed to play a role together with NO. So far, only ATP or related purines have shown to be co-transmitters with NO. Acetylcholine and tachykinins are involved in the LOS contraction acting through acetylcholine M 3 and tachykinin NK 2 receptors. Nitric oxide can also be involved in the regulation of LOS contraction. The understanding of the mechanisms that originate and modulate LOS tone, relaxation and contraction and the characterization of neurotransmitters and receptors involved in LOS function are important to develop new pharmacological tools to treat primary oesophageal motor disorders and gastro-oesophageal reflux disease.

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Section: Motor Neuronal Anatomy Of the Losmentioning

confidence: 99%

Regulation of basal tone, relaxation and contraction of the lower oesophageal sphincter. Relevance to drug discovery for oesophageal disorders

Farré¹,

Sifrim²

2008

British J Pharmacology

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“…The relatively positive resting membrane potentials of the smooth muscle cell of the PS (−41.7 mV), compared with more negative membrane potentials of smooth muscle in the stomach (about −50 mV in the gastric corpus) 16 may contribute to the high resting tone observed in the sphincteric region 5 . The underlying mechanisms are currently not clear.…”

Section: Discussionmentioning

confidence: 99%

“…Compared to neighbouring regions, the pylorus is supplied with a relatively high density of nerve fibres 2 . It receives excitatory and inhibitory inputs from enteric motor neurones, which are influenced by both extrinsic nerves and hormonal factors 3–6 . The pylorus can be either excited or inhibited by stimulation of vagus nerves 7,8 and is also inhibited by sympathetic stimulation 7 .…”

Section: Introductionmentioning

confidence: 99%

Neuronal control of the pyloric sphincter of the guinea‐pig

Shi

Costa

Brookes

2001

Neurogastroenterology Motil

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The pyloric sphincter (PS) controls gastric emptying and prevents the reflux of duodenal content into the stomach. Neuronal pathways and reflexes controlling the guinea-pig PS were physiologically investigated in isolated preparations. Simultaneous intracellular or extracellular and tension recordings from PS circular muscle with electrical and stretch stimulation were used. Electrical stimulation evoked an initial small contraction followed by a relaxation with a corresponding inhibitory junction potential (IJP) then a second large contraction with a corresponding excitatory junction potential (EJP). Hyoscine (1 micromol L-1) blocked the first contraction, and reduced the second contraction and EJP by 52.5% and 61%, respectively. These responses were further reduced by the NK2 antagonist, MEN10627 (1 micromol L-1), and the NK1 antagonist, SR140333 (1 micromol L-1). N-nitro-L-arginine (100 micro;mol L-1) and apamin (0.5 micromol L-1) blocked the relaxation and the IJP. Duodenal electrical stimulation evoked an EJP, whereas antral stimulation evoked an IJP followed by a small EJP. All were blocked by hexamethonium (100 micromol L-1). Duodenal stretch evoked tetrodotoxin-sensitive reflex contractions and membrane depolarization with action potentials in the PS. Thus, PS enteric motor neurones receive inputs from the duodenum and the stomach. There are stretch-sensitive ascending excitatory reflex pathways from the duodenum to the PS.

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“…The pylorus (gastroduodenal junction) and its sphincteric function have been an area of considerable controversy [3], It has not been regarded as a true sphincter as no region of raised intraluminal pressure could be detected with the methods used, and py loric activity could not be separated from antral activity. After the discovery of a highpressure zone in the region of the gastroduo denal junction, another group of researchers suggested that it was a true sphincter, pre venting duodenogastric reflux.…”

Section: Discussionmentioning

confidence: 99%

Diameter and Wall Thickness Recording of Canine Pylorus with Implantable Miniature Ultrasonic Transducers

Mandrek

1991

Dig Dis

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Outer diameter and thickness of the muscular wall of canine pylorus were measured simultaneously by determining the distance between pairs of implanted ultrasonic transducers, evaluating the sonic transit time with a digital sonometer. For the study of the motility in the gastroduodenal transit zone, the ultrasonically determined pyloric responses were compared with signals from conventional strain-gauge transducers sutured to the neighboring duodenum and gastric antrum. After stimulation of the gastrointestinal motility by an intravenous bolus injection of cholecystokinin octapeptide, pyloric contractions with a frequency of 5.2 min-¹ could be recorded for some minutes; those contractions were independent of the more rapid antral and duodenal motility. Together with the observed tonic constriction of the pyloric ring, which could be inhibited by intravenous injection of adrenaline, an autonomous role of the gastroduodenal junction as a true sphincter is supported.

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Sphincteric function

Cited by 7 publications

References 252 publications

Regulation of basal tone, relaxation and contraction of the lower oesophageal sphincter. Relevance to drug discovery for oesophageal disorders

Regulation of basal tone, relaxation and contraction of the lower oesophageal sphincter. Relevance to drug discovery for oesophageal disorders

Neuronal control of the pyloric sphincter of the guinea‐pig

Diameter and Wall Thickness Recording of Canine Pylorus with Implantable Miniature Ultrasonic Transducers

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