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1) In the body of the stomach, the vagal postganglionic muscarinic nerves release acetylcholine (ACh) which stimulates parietal cell H+ secretion. 2) In the lamina propria of the body of the stomach the ACh released from the vagal endings triggers histamine secretion from ECL cells. Histamine also stimulates H+ secretion from parietal cells.
Acetylcholine is a choline molecule that has been acetylated at the oxygen atom. Because of the charged ammonium group, acetylcholine does not penetrate lipid membranes. . Because of this, when the molecule is introduced externally, it remains in the extracellular space and at present it is considered that the molecule does not pass through the blood–brain
British physiologist Sir Henry Hallett Dale (1875-1968) observed acetylcholine for causing blood vessel dilation and slowing down heart rate. In 1914, Dale noted that the physiological effect of acetylcholine resembled the stimulation of parasympathetic nervous system and hypothesized acetylcholine as the neurotransmitter.
[1] [4] Chemicals in this family can act either directly by stimulating the nicotinic or muscarinic receptors (thus mimicking acetylcholine), or indirectly by inhibiting cholinesterase, promoting acetylcholine release, or other mechanisms. [5] Common uses of parasympathomimetics include glaucoma, Sjögren syndrome and underactive bladder. [6]
As a result of cholinergic crisis, the muscles stop responding to the high synaptic levels of acetylcholine, leading to flaccid paralysis, respiratory failure, and other signs and symptoms reminiscent of organophosphate poisoning. Other symptoms include increased sweating, salivation, bronchial secretions along with miosis (constricted pupils).
The muscarinic M 3 receptor regulates insulin secretion from the pancreas [7] and are an important target for understanding the mechanisms of type 2 diabetes mellitus.. Some antipsychotic drugs that are prescribed to treat schizophrenia and bipolar disorder (such as olanzapine and clozapine) have a high risk of diabetes side-effects.
Gastrin is a linear peptide hormone produced by G cells of the duodenum and in the pyloric antrum of the stomach.It is secreted into the bloodstream. The encoded polypeptide is preprogastrin, which is cleaved by enzymes in posttranslational modification to produce progastrin (an intermediate, inactive precursor) and then gastrin in various forms, primarily the following three:
In addition, release of CCK is stimulated by monitor peptide (released by pancreatic acinar cells), CCK-releasing protein (via paracrine signalling mediated by enterocytes in the gastric and intestinal mucosa), and acetylcholine (released by the parasympathetic nerve fibers of the vagus nerve).