Intestinal tract, acetylcholine receptor

Pyrantel pamoate (Antiminth) is a agonist at the nicotinic acetylcholine receptor, and its actions result in depolarization and spastic paralysis of the helminth muscle. Its selective toxicity occurs primarily because the neuromuscular junction of helminth muscle is more sensitive to the drug than is mammalian muscle. This drug is administered orally, and because very little is absorbed, high levels are achieved in the intestinal tract. Less than 15% of the drug and its metabolites are excreted in urine. 

In addition to the more or less standard actions of anticholinergic compounds due to their ability to interfere with the actions of acetylcholine on muscarinic receptors (resulting in acceleration of the heart relaxation of smooth muscles in bronchi and bronchioles, intestinal tract, urinary tract, iris and ciliary body of the eye, bile ducts and gall bladder, and some cutaneous blood vessels and decrease or abolition of secretion by glands of the gascrolncesclnal tract and skin), these substances may have pronounced effects on the central nervous system, as has been mentioned earlier. A large amount of research with experimental animals has been directed toward elucidation of the basic mechanisms Involved in these actions. 

Metociopramide [ReglanJ. This drug is officially classified as a dopamine receptor antagonist but also appears to enhance the peripheral effects of acetylcholine. Primarily because of this latter effect, metociopramide stimulates motility in the upper GI tract (prokinetic effect), which may be useful in moving the stomach contents toward the small intestine, thus decreasing the risk of gastric acid moving backward... 

Subsequent to the molecular cloning and cDNA sequence analysis of the delta opioid receptor, antireceptor antibodies were raised against synthetic peptides based on the deduced amino acid sequence of this receptor. To date, there have been a limited number of studies using antibodies directed toward the amino terminus of the cloned murine receptor to assess the distribution of delta opioid receptorlike immunoreactivity in the gastrointestinal tract, and these have been confined so far to the porcine small intestine. They have shown the presence of delta opioid receptor-immuno-reactive neurons and fibers in both the myenteric and submucosal plexuses and as well as in myenteric neurons maintained in primary culture [22, 23]. Receptor-like immunoreactivity in neuronal cell bodies appears to be localized in the cytoplasm and is likely to be trafficked to nerve terminals. These neurons are coimmunoreactive for the acetylcholine-synthesizing... 

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