Cholinergic Receptors Overview

A type of cholinergic receptor found in the neuromuscular junction, responsible for muscle contraction. It's composed of five subunits: two α1, one β, one δ, and one ε or γ.

A type of nicotinic acetylcholine receptor found in autonomic ganglia, responsible for signaling between neurons. It's composed of five subunits: two α3, three β4.

A type of nicotinic acetylcholine receptor found in the brain. It's composed of five subunits: two α4, three β2.

A type of nicotinic acetylcholine receptor found in the brain. It's composed of five subunits: two α3, three β4.

A type of nicotinic acetylcholine receptor found in the brain. It's composed of five α7 subunits.

Enzymes that break down acetylcholine (ACh), the neurotransmitter used at neuromuscular junctions and in the brain.

One type of cholinesterase responsible for breaking down ACh quickly. Found in high concentrations at the synapse.

They inhibit the enzyme acetylcholinesterase (AChE), leading to a buildup of acetylcholine in the synapse.

A group of AChE inhibitors that have a long-lasting effect. Can be found in insecticides and nerve agents.

A group of AChE inhibitors that have a shorter-lasting effect. Used in treating conditions like myasthenia gravis.

These receptors are activated by the neurotransmitter acetylcholine (ACh).

A type of cholinergic receptor that is ionotropic. They open ion channels directly when ACh binds.

A type of cholinergic receptor that is metabotropic. They activate G-proteins and trigger a cascade of intracellular signaling events.

A type of cholinergic receptor that binds acetylcholine and is coupled to G proteins. It has 5 subtypes (M1-M5) with diverse functions in the body.

A type of muscarinic receptor that is primarily found in the central nervous system (CNS). It is involved in various functions like attention, analgesia (pain relief), and arousal. Its activation leads to increased levels of IP3 (inositol triphosphate) and DAG (diacylglycerol) via the Gq protein signaling pathway.

A type of muscarinic receptor located in the heart, specifically at the sinoatrial (SA) and atrioventricular (AV) nodes, as well as the ventricles. Its activation by acetylcholine slows down the heart rate. The mechanism involves activation of the G protein, specifically its beta-gamma (βγ) subunit, which then increases potassium (K+) conductance through GIRK channels.

A type of muscarinic receptor found in smooth muscles and glandular tissues. It mediates smooth muscle contraction and glandular secretions. Its signaling pathway is similar to that of the M1 receptor, leading to increased IP3 and DAG levels through the Gq protein.

A type of cholinergic receptor that is a ligand-gated ion channel. It opens upon the binding of two acetylcholine molecules, allowing the flow of sodium ions (Na+) into the cell, leading to depolarization (excitation).

Type of neurotransmitter that binds to cholinergic receptors, responsible for signaling in both the central and peripheral nervous systems, including muscle activation.

These receptors are linked to G-proteins, which are molecular messengers that activate a cascade of events inside the cell.

These receptors are directly linked to ion channels, allowing the flow of ions into or out of the cell when acetylcholine binds.

This refers to the junction between a motor neuron and a muscle fiber, where acetylcholine is released to trigger muscle contraction.

A specialized area on a muscle cell where the nerve signal is received, leading to muscle contraction.

The part of the nervous system responsible for controlling our bodily functions that happen automatically, without conscious control, such as heart rate, digestion, and breathing.

This branch of the ANS is responsible for 'rest and digest' responses, slowing heart rate, promoting digestion, and constricting pupils.

A type of acetylcholine receptor found in both sympathetic and parasympathetic ganglia, mediating signal transmission between neurons.

Drugs that bind to and activate muscarinic acetylcholine receptors, mimicking the effects of acetylcholine.

The activation of muscarinic receptors in the eye leads to contraction of the ciliary muscle, causing the lens to become more spherical and improving near vision.

A type of acetylcholine receptor primarily located in the neuromuscular junction, responsible for muscle contraction.

Drugs that bind to and block muscarinic acetylcholine receptors, preventing the action of acetylcholine.

Muscarinic antagonists are often used to reduce saliva and mucus secretion during surgery, acting on the cholinergic receptors in the salivary glands.

Drugs that bind to and activate nicotinic acetylcholine receptors, mimicking the effects of acetylcholine.

Drugs that block the action of acetylcholine by preventing it from binding to its receptors. They have little clinical use due to various adverse effects.

Succinylcholine is a muscle relaxant used in surgery. It acts as a depolarizing neuromuscular blocker, meaning it causes continuous activation of the nicotinic acetylcholine receptors (nAChRs) at the neuromuscular junction. This continuous activation prevents the muscle from responding to nerve signals, resulting in muscle paralysis. Succinylcholine is resistant to breakdown by acetylcholinesterase (AChE), which prolongs its action at the synapse. The prolonged activation of nAChRs by succinylcholine reduces the chance of post-synaptic neuronal depolarization, leading to muscle relaxation.

nAChR antagonists are drugs or toxins that block the action of acetylcholine at nicotinic acetylcholine receptors. This blockage prevents the normal signaling process that involves acetylcholine binding to the receptor and triggering depolarization, leading to various effects depending on the receptor subtype and location. For example, blocking nAChRs at the neuromuscular junction can cause muscle paralysis, while blocking nAChRs in the brain can disrupt cognitive function.

α-bungarotoxin is a neurotoxin found in the venom of certain snakes. It acts as a potent antagonist of nicotinic acetylcholine receptors at the neuromuscular junction. It binds irreversibly to the nAChRs, blocking acetylcholine from binding and causing paralysis. This paralysis can lead to respiratory failure and death if not treated promptly.

Tubocurarine and pancuronium are non-depolarizing neuromuscular blockers. They block the action of acetylcholine at the nicotinic acetylcholine receptors (nAChRs) at the neuromuscular junction, but unlike succinylcholine, they do not cause continuous activation. Instead, they competitively inhibit acetylcholine from binding, leading to muscle relaxation.

Trimethaphan is a ganglionic blocker that is used to treat hypertension in patients with acute aortic dissection. It works by blocking nicotinic acetylcholine receptors at the autonomic ganglia. This blockade disrupts the transmission of nerve impulses through the autonomic nervous system, leading to a decrease in blood pressure.