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Gastroenterology
Published in Paul Bentley, Ben Lovell, Memorizing Medicine, 2019
Muscular/myenteric plexus MyopathyGanglion/peristalsis dysfunction: Scleroderma/CRESTOesophageal spasmAchalasia
Radiation Injury
Published in Han C. Kuijpers, Colorectal Physiology: Fecal Incontinence, 2019
The marked damage to the myenteric plexus seen histologically may be responsible for the abnormalities of distensibility or nonrelaxation, as suggested by the absence or reduction in amplitude of the rectal distension reflex in such patients.14 The hypertrophy of the smooth muscle seen in the histological preparations is further evidence of damage to the myenteric plexus as there is some evidence that denervated smooth muscle hypertrophies.25
Non-adrenergic Non-cholinergic Autonomic Transmission
Published in Kenneth J. Broadley, Autonomic Pharmacology, 2017
Other materials may be found stored in autonomic nerve endings which have not been synthesized by the neurone, but which have been taken up from the circulation. Such agents may then be co-released along with the principal neurotransmitters and the co-transmitters. Examples of this type of co-released material include 5-hydroxytryptamine (5-HT) and adrenaline. Adrenaline is carried in the circulation from the adrenal medullae and co-released with noradrenaline; its role has been discussed in Chapter 6. 5-HT may also be taken up by the neuronal uptake pathway of sympathetic neurones (see Chapter 2) after being released from circulating platelets. It may then be released from the neurone as a transmitter, to produce effects on postjunctional 5-HT2 receptors and cause the primary vascular response of vasoconstriction (Kupfermann 1991). Neurones that synthesize and release 5-HT are located in the myenteric plexus of the guinea-pig and human intestine. Most of the 5-HT of the gastrointestinal tract is found in the enterochromaffin cells, and it is difficult to assess whether 5-HT that is released and assigned to a neuronal location originates from these cells. The 5-HT-containing neurones have their cell bodies in the myenteric plexus (Figure 1.5). The axons travel in an anal direction and project through the circular muscle to innervate submucosal ganglia. This is consistent with an interneuronal function within the myenteric plexus and a function on modulating intestinal secretion in the submucous plexus (Hills & Jessen 1992).
Segmental Dilatation of Ileum Involving Bronchogenic Cyst in a Newborn
Published in Fetal and Pediatric Pathology, 2023
Özkan Okur, Malik Ergin, Akgun Oral, Munevver Hosgor
Miroscopically, the cystic structure was lined with pseudostratified respiratory ciliated epithelium. Seromucinous glands and cartilage islands were present in the lamina propria and submucosa. The cyst epithelium had a respiratory type appearance and contained dense cilia on its surface. This appearance was consistent with a bronchogenic cyst (Fig. 4). The intestinal muscle layer was thinner around the cystic structure, where the usual circular and longitudinal muscularis propria with normal myenteric plexus were present. Immunohistochemical staining revealed myenteric ganglion cells showing Ret-oncoprotein positivity and interstitial Cajal cells showing CD117 positivity (Fig. 4). Ganglion cells with usual distribution were observed in the myenteric nerve plexus. The calretinin staining shows that lack of mucosal punctate positivity in the ganglionic SID segment, (Fig. 5), suggesting defective innervation. It would suggest that the innervation is defective. In the sections from the dilated segment normal ganglion cells could be demonstrated histologically, no hypertrophy of the muscles layers was seen in other areas there were no any other findings in mucosa and intestinal wall.
Communication between the gut microbiota and peripheral nervous system in health and chronic disease
Published in Gut Microbes, 2022
Tyler M. Cook, Virginie Mansuy-Aubert
The enteric nervous system is comprised of sensory, motor, and interneurons organized into networks or plexuses located within the gut, which are capable of operating independently of the CNS. The submucosal plexus lies between the mucosa and circular muscle, and it regulates secretion and blood flow.39 Enteric neurons between the circular and longitudinal muscle make up the myenteric plexus (Auerbach plexus), which controls gut motility by action on smooth muscle. Enteric sensory neurons known as IPANs (intrinsic primary afferent neurons) detect various chemicals or distension caused by a food bolus, and then coordinate the electrical activity of submucosal and myenteric neurons. Finally, interneurons link the activity of ascending and descending motor networks to allow the “little brain” of the gut to function autonomously (Figure 3).39,51 The enteric nervous system is also supported by local glial cells, which also respond to changes in gut microbiota signaling,52 but we will focus on enteric neurons in this review.
How can we develop better antispasmodics for irritable bowel syndrome?
Published in Expert Opinion on Drug Discovery, 2019
Sheyda Ranjbar, Seyed Afshin Seyednejad, Shekoufeh Nikfar, Roja Rahimi, Mohammad Abdollahi
Myenteric plexus innervates GI tract and regulates its motility under direct effect of the autonomic nervous system. Acetylcholine (ACh) is the major excitatory neurotransmitter (NT) in GI and exerts its effects via nicotinic and muscarinic receptors [24]. Therefore, anti-muscarinic drugs are widely used to decrease gut motility. Current anticholinergic drugs mostly act in a non-selective manner and due to the presence of muscarinic and nicotinic receptors in different body organs, there are several adverse effects associated with this group. As a result, in order to obtain better anticholinergic drugs, we should focus on designing anticholinergics that selectively target muscarinic receptor isoforms present in the GI. Muscarinic receptors type 1–3 (M1-3) exist in the myenteric plexus as well as the myo-neural junction, but investigations have shown that anticholinergics with the ability to selectively target M3 receptor tend to have less adverse effects [25]. Therefore, much attention has been attracted to the evaluation of available or design of new M3 selective antagonists. Darifenacin and zamifenacin are M3 selective antagonists and both have the ability to reduce colonic motility. Solifenacin, a newer M3 selective antagonist, is as efficacious as ramosetron in the alleviation of IBS-D patients symptoms [26]. Although these drugs cause less adverse effects compared to the non-selective anticholinergics, due to the wide presence of M3 receptors in various tissues, further progress in the design of more safe spasmolytics may be obtained through the development of tissue-specific M3 antagonists [27].