Acetylcholine receptor

Acetylcholine receptor

Structure of the nicotinic acetylcholine receptor

Chemical structure of acetylcholine

An acetylcholine receptor (AChR) is a protein that responds to the neurotransmitter acetylcholine. These receptors are integral membrane proteins that mediate the effects of acetylcholine in the nervous system. There are two main types of acetylcholine receptors: nicotinic and muscarinic.

Types

Nicotinic acetylcholine receptors

Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that are activated by the binding of acetylcholine. They are found in the neuromuscular junction, autonomic ganglia, and the central nervous system. These receptors are named "nicotinic" because they can also be activated by nicotine.

Muscarinic acetylcholine receptors

Muscarinic acetylcholine receptors (mAChRs) are G protein-coupled receptors that mediate slower responses to acetylcholine. They are found in various tissues, including the heart, smooth muscle, and glandular tissue. These receptors are named "muscarinic" because they can be activated by muscarine, a compound found in certain mushrooms.

Function

Acetylcholine receptors play a crucial role in the transmission of signals in the nervous system. When acetylcholine binds to these receptors, it causes a conformational change that leads to the opening of ion channels or activation of intracellular signaling pathways. This results in various physiological responses, such as muscle contraction, modulation of heart rate, and secretion of glandular products.

Structure

The structure of acetylcholine receptors varies between the nicotinic and muscarinic types. Nicotinic receptors are composed of five subunits that form a central pore, while muscarinic receptors have a single polypeptide chain that spans the membrane seven times.

Clinical significance

Acetylcholine receptors are targets for various drugs and toxins. For example, antagonists of nicotinic receptors, such as curare, are used as muscle relaxants during surgery. Muscarinic receptor antagonists, such as atropine, are used to treat bradycardia and reduce salivation during surgery.

Related pages

• Neurotransmitter
• Synapse
• Ion channel
• G protein-coupled receptor