Muscarinic receptor
Muscarinic receptors are a type of G protein-coupled receptor that are responsive to the molecule acetylcholine. They are named for their activation by the substance muscarine. Muscarinic receptors are found in various locations of the body, including the central nervous system, the peripheral nervous system, and various smooth muscle tissues.
Structure[edit | edit source]
Muscarinic receptors are G protein-coupled receptors with seven transmembrane domains. The binding site for acetylcholine is located in the extracellular portion of the receptor.
Function[edit | edit source]
Muscarinic receptors play several roles in the body. They are involved in various physiological functions, such as heart rate, smooth muscle contraction, and glandular secretion. The activation of muscarinic receptors by acetylcholine can lead to either an excitatory or inhibitory response, depending on the type of receptor and its location in the body.
Types[edit | edit source]
There are five known types of muscarinic receptors, labeled M1 through M5. Each type has a different distribution in the body and plays a different role in the body's physiological functions.
- M1 receptors are found in the brain and gastric parietal cells. They are involved in gastric acid secretion and cognitive functions.
- M2 receptors are found in the heart and smooth muscle. They are involved in heart rate regulation and smooth muscle relaxation.
- M3 receptors are found in smooth muscle, glands, and the endothelium. They are involved in smooth muscle contraction and glandular secretion.
- M4 receptors are found in the brain. They are involved in the regulation of dopamine activity.
- M5 receptors are found in the brain and peripheral blood vessels. They are involved in vasodilation and increase of dopamine activity.
Clinical significance[edit | edit source]
Muscarinic receptors are targets for a number of drugs used to treat various conditions, such as Alzheimer's disease, Parkinson's disease, and asthma. Drugs that block muscarinic receptors are known as antimuscarinic drugs, while drugs that activate muscarinic receptors are known as muscarinic agonists.
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