| [ Summary ] |
Acetylcholine receptors are divided into two types, nicotinic receptor and muscarinic receptor. The latter is covered in this manuscript since it exists in those organs under the control of the parasympathetic nerve. It also exists in the central nervous system and the ganglions. Its molecular structure is a single-chain shaped glycoprotein, with a molecular weight of about 50,000, passing through the cell-membrane 7 times. Its response is transmitted to the inside of the cell, using GTP proteins as transducers. It is classified into three subtypes ; M1, M2 and M3. M1 exists in the central nervous system and ganglions. M2 exists in the heart, and M3 exists in the organs, except for the heart, under the control of parasympathetic nerves. As for the clinical application of drugs acting on muscarinic receptors in the area of the alimentary tract, agonists are used as a therapy for paralytic ileus, or acute gastrectasia and as one of the diagnostic tests of achalasia. Antagonists are used as a therapy for abdominal pain, due to spasms of the alimentary tract, peptic ulcers and irritable bowel syndrome. In using these drugs it must be keep in mind that they act not only on the alimentary tract, but also on other organs under the control of the parasympathetic nerves. |