Gastrointestinal smooth muscle

Meiss, R.A. (1989). Mechanics of gastrointestinal smooth muscle. In Handbook of Physiology, Section VI. The Gastrointestinal System, Volume 1, Part 1 (Wood, J.D. ed.), pp. 273-329, American, Physiological Society, Bethesda, MD. 

There may be substantial variation both within and among species (e.g., in mice vs. humans) in the expression of various proteins, receptors and/or ligands that influence the activation of mast cells (or basophils or other potential effector cell types), or that can regulate the responsiveness of end organ target cells (e.g., bronchial or gastrointestinal smooth muscle cells, vascular endothelial cells) to potential mediators of anaphylaxis derived from mast cells. 

Peppermint oil is widely advocated it acts as an antispas-modic agent due to its ability to relax gastrointestinal smooth muscle. However, it also relaxes the lower esophageal sphincter, which could allow reflux of gastric contents into the esophagus. The usual dose is 1 to 2 enteric-coated capsules containing 0.2 mL of peppermint oil two to three times daily. 

McCarron In a knockout mouse lacking the type 1 InsP3 receptor, the excitatory junction potentials are reduced in gastrointestinal smooth muscle. 

SK channels are not activated by Ca2+ release through RyRs (Herrera et al 2001, this study), however SK channels are activated by InsP3R-mediated Ca2+ release in gastrointestinal smooth muscle (Bayguinov et al 2000). In UBSM, SK channels are activated by Ca2+ entry through VDCCs, and this likely contributes to the action potential after-hyperpolarization (Fig. IE). 

Their actions on smooth muscle, in particular, can be complex. For example, both PGEs and PGFs induce contraction of uterine and gastrointestinal smooth muscle. On the other hand, PGEs stimulate dilation of vascular and bronchial smooth muscle, whereas PGFs induce constriction of these muscle types. 

Substance P An eleven-amino add neurotransmitter that appears in both the central and peripheral nervous systems. It is involved in transmission of pain, causes rapid contractions of the gastrointestinal smooth muscle, and modulates inflammatory and immune responses. [NIH]... 

Histamine is able to cause uterine contraction. Although the magnitude of this effect in humans is normally small, the large amounts of histamine released during anaphylactic reactions can initiate abortion in pregnant women. Histamine can also stimulate contraction of gastrointestinal smooth muscle, with large doses able to produce diarrhea. 

PGEi Bronchodilatation Inhibitor of fat breakdown Inhibitor of platelet aggregation Stimulates contraction of gastrointestinal smooth muscle Vasodilation... 

Gerthoffer WT Signal-transduction pathways that regulate visceral smooth muscle function. III. Coupling of muscarinic receptors to signaling kinases and effector proteins in gastrointestinal smooth muscles. Am J Physiol 2005 288 G849. 

Macrolide antibiotics such as erythromycin directly stimulate motilin receptors on gastrointestinal smooth muscle and promote the onset of a migrating motor complex. Intravenous erythromycin (3 mg/kg) is beneficial in some patients with gastroparesis however, tolerance rapidly develops. It may be used in patients with acute upper gastrointestinal hemorrhage to promote gastric emptying of blood before endoscopy. 

Class PGAs Vascular Smooth Muscle Vasodilation Airway Smooth Muscle Gastrointestinal Smooth Muscle Gastrointestinal Secretions Decrease Uterine Muscle (Nonpregnant) Relaxation Platelet Aggregation... 

Beta-2 Bronchiole smooth muscle Some arterioles (skeletal muscle, liver] Gastrointestinal smooth muscle Skeletal muscle and liver cells Uterus Gallbladder Relaxation (bronchodilation] Vasodilation Decreased motility Increased cellular metabolism Relaxation Relaxation... 

Gastrointestinal smooth muscles Prostaglandin E2 contracts longitudinal but relaxes circular smooth muscles, whereas prostaglandin F2 contracts both. 

Gastrointestinal smooth muscle motility is affected from the stomach to the colon. In general, the walls of the viscera are relaxed, and both tone and propulsive movements are diminished. 

Relaxation of gastrointestinal smooth muscle can be brought about by both a- and 13-stimulant agents. Beta receptors appear to be located directly on the smooth muscle cells and mediate relaxation via hyperpolarization and decreased spike activity in these cells. Alpha stimulants, especially -selective agonists, decrease muscle activity indirectly by presynaptically reducing the release of acetylcholine and possibly other stimulants within the enteric nervous system (see... 

Hi receptor antagonists block the actions of histamine by reversible competitive antagonism at the Hi receptor. They have negligible potency at the H2 receptor and little at the H3 receptor. For example, histamine-induced contraction of bronchiolar or gastrointestinal smooth muscle can be completely blocked by these agents, but the effects on gastric acid secretion and the heart are unmodified. 

The peripheral effects concern the motility and tonus of gastrointestinal smooth muscle segmentation is enhanced but propulsive peristalsis is inhibited. The tonus of sphincter muscles is markedly raised (spastic constipation). The antidiarrhetic effect is used therapeutically (loperamide, p.180). Gastric emptying is delayed (pyloric spasm) and drainage of bile and pancreatic juice is impeded because the sphincter of Oddi contracts. Likewise, bladder function is affected specifically bladder emptying is impaired owing to an increased tone of the vesicular sphincter. 

Occasionally, gastrointestinal disorders have been related to the use of hemoglobin-based oxygen carriers, possibly through binding of nitrous oxide, causing gastrointestinal smooth muscle spasm (9,20). 

Motilin is a neuropeptide expressed predominantly in the gastrointestinal tract that stimulates the contraction of gastrointestinal smooth muscle throughout the gut (Tonini 1996). Physiologically, its most characteristic role seems to be the induction of coordinated interdigestive antral and duodenal contractions (phase III of the migrating motor complex). The effects of motilin are both species and dose dependent. Motilin appears to have at least two receptors, one muscular and the other neuronal. Recent studies in vivo have emphasized the importance of the latter pathway and it is currently hypothesized that motilin acts on neurons in the myenteric plexus to release acetylcholine and other excitatory neurotransmitters. 

Bethanechol is a synthetic cholinergic agonist (P-methyl analog of carbachol) that has parasympathomimetic effects in gastrointestinal smooth muscle and in the detrusor muscle. It has... 

GI (enterochromaffin cells) Hormonal (paracrine) Gastrointestinal smooth muscle... 

It has little or no central action but acts selectively on gastrointestinal smooth muscle. It takes longer to act than loperamide. 

Dicycloverine and atropine are antimuscarinic drugs included in some indigestion medicines to relieve colic. They exert a relaxant effect on gastrointestinal smooth muscle and inhibit gastric secretion. 

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