Nervous system enteric

CGRP is widely distributed throughout the peripheral and central nervous systems and is found ia sensory neurons and ia the autonomic and enteric nervous systems. In many iastances CGRP is co-localized with other neuroregulators, eg, ACh ia motor neurons, substance P, somatostatin, vasoactive intestinal polypeptide (VIP), and galanin ia sensory neurons. It is also present ia the CNS, with ACh ia the parabigeminal nucleus and with cholecystokinin (CCK) ia the dorsal parabrachial area. CGRP functions as a neuromodulator or co-transmitter. 

As a neurotransmitter in the sensory nervous system, high levels of substance P are found in the dorsal horn of the spinal cord as well as in peripheral sensory nerve terminals. However, substance P also plays a significant role as a neuromodulator in the central, sympathetic, and enteric nervous system. NKA and NKB are also localized selectively in the CNS. 

NK3rs are preferentially expressed in the CNS. At the peripheral level, NK3rs have been localized in the enteric nervous system, nerve terminals, and autonomic ganglia, but also on other tissues. At the peripheral level, it remains to be explained the mismatch between NK3r expression and the apparent lack of expression of NKB there are, however, physiological conditions... 

Figure 3.1 A schematic representation of the control mechanism that stimulates gastric acid secretion, and the intervention points used to treat ulcers. The parietal cells and gastric cells form part of the epithelial cell lining of the stomach. Histamine release is usually triggered as part ofthe enteric nervous system response to distension of the stomach when food is eaten.

ELISA Enzyme-linked immunosorbent assay EMS Eosinophilia-myalgia syndrome ENS Enteric nervous system EO Eosinophil... 

Enteric nerves control intestinal smooth muscle action and are connected to the brain by the autonomic nervous system. IBS is thought to result from dysregulation of this brain-gut axis. The enteric nervous system is composed of two gan-glionated plexuses that control gut innervation the submucous plexus (Meissner s plexus) and the myenteric plexus (Auerbach s plexus). The enteric nervous system and the central nervous system (CNS) are interconnected and interdependent. A number of neurochemicals mediate their function, including serotonin (5-hydroxytryptamine or 5-HT), acetylcholine, substance P, and nitric oxide, among others. 

Loperamide stimulates enteric nervous system receptors, inhibiting peristalsis and fluid secretion. It improves stool consistency and reduces the number of stools.21 Consequently, it is most useful in patients who have diarrhea as a prominent symptom. However, it can occasionally aggravate abdominal pain. 

The mechanism of diarrhea has not been clearly elucidated, but theories include a reduction in the absorptive surface along with impaired absorption owing to cellular damage, enterotoxigenic effects of a rotavirus protein, and stimulation of the enteric nervous system.43... 

It has been known for some time that the enteric nervous system does not simply regulate smooth muscle contraction, but is intimately involved in the control of transport processes in enterocytes. Nerve fibres in the mucosa terminate subjacent to the basement membrane of epithelial and entero-endocrine cells, on which muscarinic acetylcholine receptors (mAChRs)... 

CNS, central nervous system PNS, peripheral nervous system ENS, enteric nervous system. 

Brownlee, D.J.A, Fairweather, I., Johnston, C.F. and Shaw, C. (1994) Immunocytochemical demonstration of peptidergic and serotoninergic components in the enteric nervous system of the roundworm, Ascaris suum (Nematoda, Ascaroidea). Parasitology 108, 89-103. 

HEREDITARY AND ACQUIRED DISEASES INVOLVING THE ENTERIC NERVOUS SYSTEM 626... 

This chapter provides a short review of peripheral nerve diseases. Diseases that involve motor neurons, the presyn-aptic compartment of neuromuscular junctions, or the enteric nervous system are also discussed. 

Diseases selectively targeting spinal cord and brainstem motor neurons (e.g. amyotrophic lateral sclerosis and the familial spinal muscular atrophies) or the presynaptic component of neuromuscular junctions (e.g. Lambert-Eaton syndrome, botulism and Ixodes tick paralysis) cause weakness without sensory impairment. Disorders involving the enteric nervous system (e.g. Chagas disease and Hirschsprung s disease) impair bowel motility. 

Bondurand, N., Natarajan, D., Thapar, N., Atkins, C. and Pachnis, V. Neuron and glia generating progenitors of the mammalian enteric nervous system isolated from fetal and postnatal gut cultures. Development 130 6387-6400, 2003. 

The GI system is responsible at its most basic level for providing a continual supply of water, electrolytes, minerals, and nutrients. This is achieved by a myriad of specialized cells and coordinated interplay of motility, secretion, digestion, absorption, blood flow, and lymph flow. These components are under elaborate control of the central and enteric nervous systems, endocrine and paracrine regulation of hormones. The highly complex nature of GI function is clearly illustrated by the estimate that 80 to 100 million neurons exist within the enteric nervous system, a number comparable to that found within the spinal column, hence described as a "second brain."171... 

Gershon, M.D., The enteric nervous system a second brain, Hosp. Pract. (Office Edition), 34, 31-32, 1999. 

Atropine and scopolamine have antispasmodic effects on the gastrointestinal tract. It partly inhibits vagal influence in the gut, reducing motility. However, the enteric nervous system also employs serotonin and dopamine, so parasympathetic innervation plays a modulatory role. 

The control of gut function involves interplay between neurones and peptide hormones. Information from a variety of receptors along the digestive tract is processed by a network of nerves, the enteric nervous system, which also receives input from the brain. 

The gastrointestinal system of zebrafish presents clear differences from the human system. The zebrafish does not possess a stomach, the intestine is continuous with the pharynx through a short esophagus, and no sphincters are present [61]. However, zebrafish have most of the cell types observed in the small intestine -absorptive, endocrine, goblet, and interstitial cells of Cajal, although Paneth cells are absent. Gut contractions are under the control of the enteric nervous systems, which respond to different pharmaceuticals in similar way as the mammalian counterpart. For example, zebrafish embryos can be used as predictor of emetic response to pharmaceuticals, one of the most commonly reported clinical adverse effects to be considered in the development of new dmgs [61]. 

Furness JB and Costa M. The Enteric Nervous System. New York Churchill Livingstone, 1987. 

Drugs that affect the central nervous system may also have a major action in the gut. Thus, the constipating effects of opium alkaloids are exerted through this system and a number of the important withdrawal symptoms reflect the actions of the enteric nervous system. The nervous system is often regarded as a command (efferent) system that sends instructions to be executed. However, there is also a sensory (afferent) component, that receives information from innervated systems... 

A highly simplified diagram of the intestinal wall and some of the circuitry of the enteric nervous system (ENS). The ENS receives input from both the sympathetic and the parasympathetic systems and sends afferent impulses to sympathetic ganglia and to the central nervous system. Many transmitter or neuromodulator substances have been identified in the ENS see Table 6-1. ACh, acetylcholine AC, absorptive cell CM, circular muscle layer EC, enterochromaffin cell EN, excitatory neuron EPAN, extrinsic primary afferent neuron 5HT, serotonin IN, inhibitory neuron IPAN, intrinsic primary afferent neuron LM, longitudinal muscle layer MP, myenteric plexus NE, norepinephrine NP, neuropeptides SC, secretory cell SMP, submucosal plexus. 

Table 6-1 Some of the Transmitter Substances Found in Autonomic Nervous System (ANS), Enteric Nervous System (ENS), and Nonadrenergic, Noncholinergic Neurons.1...

Galligan JJ Ligand-gated ion channels in the enteric nervous system. Neurogastroenterol Motil 2002 14 611. [PMID 12464083]... 

Brain serotonergic neurons are involved in numerous diffuse functions such as mood, sleep, appetite, and temperature regulation, as well as the perception of pain, the regulation of blood pressure, and vomiting (see Chapter 21). Serotonin also appears to be involved in clinical conditions such as depression, anxiety, and migraine. Serotonergic neurons are also found in the enteric nervous system of the gastrointestinal tract and around blood vessels. In rodents (but not in humans), serotonin is found in mast cells. 

HT1P Enteric nervous system G0, slow EPSP 5-Hydroxyindalpine Renzapride... 

HT3 receptors in the gastrointestinal tract and in the vomiting center of the medulla participate in the vomiting reflex (see Chapter 62). They are particularly important in vomiting caused by chemical triggers such as cancer chemotherapy drugs. 5-HTip and 5-HT4 receptors also play important roles in enteric nervous system function. 

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