Acetylcholine
Overview
 
The chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 acetylcholine (often abbreviated ACh) is a neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...

 in both the peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

 (PNS) and central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 (CNS) in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...

 (ANS) and the only neurotransmitter used in the motor division of the somatic nervous system
Somatic nervous system
The somatic nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles...

 (sensory neurons use glutamate and various peptides at their synapses). Acetylcholine is also the principal neurotransmitter in all autonomic ganglia.

Acetylcholine slows the heart rate when functioning as an inhibitory neurotransmitter.
Encyclopedia
The chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 acetylcholine (often abbreviated ACh) is a neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...

 in both the peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

 (PNS) and central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 (CNS) in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...

 (ANS) and the only neurotransmitter used in the motor division of the somatic nervous system
Somatic nervous system
The somatic nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles...

 (sensory neurons use glutamate and various peptides at their synapses). Acetylcholine is also the principal neurotransmitter in all autonomic ganglia.

Acetylcholine slows the heart rate when functioning as an inhibitory neurotransmitter. However, acetylcholine also behaves as an excitatory neurotransmitter at neuromuscular junctions.

History

Acetylcholine (ACh) was first identified in 1914 by Henry Hallett Dale
Henry Hallett Dale
Sir Henry Hallett Dale, OM, GBE, PRS was an English pharmacologist and physiologist. For his study of acetylcholine as agent in the chemical transmission of nerve impulses he shared the 1936 Nobel Prize in Physiology or Medicine with Otto Loewi.-Biography:Henry Hallett Dale was born in Islington,...

 for its actions on heart tissue. It was confirmed as a neurotransmitter by Otto Loewi
Otto Loewi
Otto Loewi was a German born pharmacologist whose discovery of acetylcholine helped enhance medical therapy. The discovery earned for him the Nobel Prize in Physiology or Medicine in 1936 which he shared with Sir Henry Dale, whom he met in 1902 when spending some months in Ernest Starling's...

, who initially gave it the name Vagusstoff
Vagusstoff
Vagusstoff refers to the substance released by stimulation of the vagus nerve which causes a reduction in the heart rate. Discovered in 1921 by physiologist Otto Loewi, vagusstoff was the first confirmation of chemical synaptic transmission and the first neurotransmitter ever discovered...

 because it was released from the vagus nerve
Vagus nerve
The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...

. Both received the 1936 Nobel Prize in Physiology or Medicine
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine administered by the Nobel Foundation, is awarded once a year for outstanding discoveries in the field of life science and medicine. It is one of five Nobel Prizes established in 1895 by Swedish chemist Alfred Nobel, the inventor of dynamite, in his will...

 for their work. Acetylcholine was also the first neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...

 to be identified.

Chemistry

Acetylcholine is an ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

 of acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

 and choline
Choline
Choline is a water-soluble essential nutrient. It is usually grouped within the B-complex vitamins. Choline generally refers to the various quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation....

 with chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 CH3CO
Acetyl
In organic chemistry, acetyl is a functional group, the acyl with chemical formula COCH3. It is sometimes represented by the symbol Ac . The acetyl group contains a methyl group single-bonded to a carbonyl...

O
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

CH2CH2N
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

+(CH3)3. This structure is reflected in the systematic name, 2-acetoxy-N,N,N-trimethylethanaminium. Its receptors have very high binding constants.

Function

Acetylcholine has functions both in the peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

 (PNS) and in the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 (CNS) as a neuromodulator.

In the peripheral nervous system, acetylcholine activates muscles, and is a major neurotransmitter in the autonomic nervous system.

In the central nervous system, acetylcholine and the associated neurons form a neurotransmitter system, the cholinergic system, which tends to cause anti-excitatory actions.

In the peripheral nervous system

In the peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

, acetylcholine activates muscles, and is a major neurotransmitter in the autonomic nervous system.
When acetylcholine binds to acetylcholine receptor
Acetylcholine receptor
An acetylcholine receptor is an integral membrane protein that responds to the binding of acetylcholine, a neurotransmitter.-Classification:...

s on skeletal muscle
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...

 fibers, it opens ligand-gated sodium channels in the cell membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...

. Sodium ions then enter the muscle cell, initiating a sequence of steps that finally produce muscle contraction. Although acetylcholine induces contraction of skeletal muscle, it acts via a different type of receptor (muscarinic) to inhibit contraction of cardiac muscle
Cardiac muscle
Cardiac muscle is a type of involuntary striated muscle found in the walls and histologic foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle...

 fibers.

In the autonomic nervous system
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...

, acetylcholine is released in the following sites:
  • all pre- and post-ganglionic parasympathetic
    Parasympathetic nervous system
    The parasympathetic nervous system is one of the two main divisions of the autonomic nervous system . The ANS is responsible for regulation of internal organs and glands, which occurs unconsciously...

     neurons
  • all preganglionic sympathetic
    Sympathetic nervous system
    The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response...

     neurons
    • preganglionic sympathetic fibers to suprarenal medulla, the modified sympathetic ganglion; on stimulation by acetylcholine, the suprarenal medulla releases epinephrine
      Epinephrine
      Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...

       and norepinephrine
      Norepinephrine
      Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...

  • some postganglionic sympathetic fibers
    • pseudomotor neurons to sweat gland
      Sweat gland
      Sweat glands, or sudoriferous glands, are small tubular structures of the skin that produce sweat. There are two kinds of sweat glands:...

      s.

In the central nervous system

In the central nervous system, ACh has a variety of effects as a neuromodulator upon plasticity, arousal and reward
Reward system
In neuroscience, the reward system is a collection of brain structures which attempts to regulate and control behavior by inducing pleasurable effects...

. ACh has an important role in the enhancement of sensory perceptions when we wake up and in sustaining attention.

Damage to the cholinergic (acetylcholine-producing) system in the brain has been shown to be plausibly associated with the memory deficits associated with Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...

.
ACh has also been shown to promote REM sleep

Pathways

There are three ACh pathways in the CNS.
  • Pons to thalamus and cortex
  • Magnocellular forebrain nucleus to cortex
  • Septohippocampal

Structure

Acetylcholine and the associated neurons form a neurotransmitter system, the cholinergic system from the brainstem and basal forebrain
Basal forebrain
The basal forebrain is a collection of structures located ventrally to the striatum. It is considered to be the major cholinergic output of the central nervous system . It includes a group of structures that lie near the bottom of the front of the brain, including the nucleus basalis, diagonal band...

 that projects axons to many areas of the brain. In the brainstem it originates from the Pedunculopontine nucleus
Pedunculopontine nucleus
The pedunculopontine nucleus is located in the brainstem, caudal to the substantia nigra and adjacent to the superior cerebellar peduncle. It has two divisions, one containing cholinergic neurons, the pars compacta, and one containing mostly glutamatergic neurons, the pars dissipata...

 and dorsolateral tegmental nuclei collectively known as the mesopontine tegmentum
Pontine tegmentum
The pontine tegmentum is a part of the pons of the brain involved in the initiation of REM sleep. It includes the pedunculopontine nucleus and the laterodorsal tegmental nucleus, among others, and is located near the raphe nucleus and the locus ceruleus....

 area or pontomesencephalotegmental complex. In the basal forebrain, it originates from the basal optic nucleus of Meynert and medial septal nucleus:
  • The pontomesencephalotegmental complex acts mainly on M1 receptors in the brainstem, deep cerebellar nuclei, pontine nuclei
    Pontine nuclei
    The pontine nuclei are a part of the pons involved in motor activity. Corticopontine fibres carry information from the primary motor cortex to the ipsilateral pontine nucleus in the ventral pons, and the pontocerebellar projection then carries that information to the contralateral cerebellum via...

    , locus ceruleus
    Locus ceruleus
    The locus coeruleus , is a nucleus in the brainstem involved with physiological responses to stress and panic. It was discovered in the 18th century by Félix Vicq-d'Azyr....

    , raphe nucleus, lateral reticular nucleus
    Lateral reticular nucleus
    The lateral reticular nucleus, of the funiculus, can be divided into three subnuclei, the parvocellular, magnocellular and the subtrigeminal. As is typical of the reticular formation, none of these are very distinct subnuclei, but rather blurred distinctions between cell types and location...

     and inferior olive. It also projects to the thalamus
    Thalamus
    The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...

    , tectum, basal ganglia
    Basal ganglia
    The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...

     and basal forebrain
    Basal forebrain
    The basal forebrain is a collection of structures located ventrally to the striatum. It is considered to be the major cholinergic output of the central nervous system . It includes a group of structures that lie near the bottom of the front of the brain, including the nucleus basalis, diagonal band...

    .
  • Basal optic nucleus of Meynert acts mainly on M1 receptors in the neocortex
    Neocortex
    The neocortex , also called the neopallium and isocortex , is a part of the brain of mammals. It is the outer layer of the cerebral hemispheres, and made up of six layers, labelled I to VI...

    .
  • Medial septal nucleus acts mainly on M1 receptors in the hippocampus
    Hippocampus
    The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...

     and neocortex
    Neocortex
    The neocortex , also called the neopallium and isocortex , is a part of the brain of mammals. It is the outer layer of the cerebral hemispheres, and made up of six layers, labelled I to VI...

    .


In addition, ACh acts as an important "internal" transmitter in the striatum
Striatum
The striatum, also known as the neostriatum or striate nucleus, is a subcortical part of the forebrain. It is the major input station of the basal ganglia system. The striatum, in turn, gets input from the cerebral cortex...

, which is part of the basal ganglia
Basal ganglia
The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...

. It is released by a large set of interneurons with smooth dendrites, known as tonically active neurons or TANs.

Plasticity

ACh is involved with synaptic plasticity
Synaptic plasticity
In neuroscience, synaptic plasticity is the ability of the connection, or synapse, between two neurons to change in strength in response to either use or disuse of transmission over synaptic pathways. Plastic change also results from the alteration of the number of receptors located on a synapse...

, specifically in learning
Learning
Learning is acquiring new or modifying existing knowledge, behaviors, skills, values, or preferences and may involve synthesizing different types of information. The ability to learn is possessed by humans, animals and some machines. Progress over time tends to follow learning curves.Human learning...

 and short-term memory.

Acetylcholine has been shown to enhance the amplitude of synaptic potentials following long-term potentiation
Long-term potentiation
In neuroscience, long-term potentiation is a long-lasting enhancement in signal transmission between two neurons that results from stimulating them synchronously. It is one of several phenomena underlying synaptic plasticity, the ability of chemical synapses to change their strength...

 in many regions, including the dentate gyrus
Dentate gyrus
The dentate gyrus is part of the hippocampal formation. It is thought to contribute to new memories as well as other functional roles. It is notable as being one of a select few brain structures currently known to have high rates of neurogenesis in adult rats, .The dentate gyrus cells receive...

, CA1, piriform cortex
Piriform cortex
In anatomy of animals, the piriform cortex, or pyriform cortex is a region in the brain.-Anatomy and function:The piriform cortex is part of the rhinencephalon situated in the telencephalon....

, and neocortex
Neocortex
The neocortex , also called the neopallium and isocortex , is a part of the brain of mammals. It is the outer layer of the cerebral hemispheres, and made up of six layers, labelled I to VI...

. This effect most likely occurs either through enhancing currents through NMDA
NMDA
N-Methyl-D-aspartic acid or N-Methyl-D-aspartate is an amino acid derivative which acts as a specific agonist at the NMDA receptor mimicking the action of glutamate, the neurotransmitter which normally acts at that receptor...

 receptors or indirectly by suppressing adaptation
Neural adaptation
Neural adaptation or sensory adaptation is a change over time in the responsiveness of the sensory system to a constant stimulus. It is usually experienced as a change in the stimulus. For example, if one rests one's hand on a table, one immediately feels the table's surface on one's skin. Within a...

. The suppression of adaptation has been shown in brain slices of regions CA1, cingulate cortex
Cingulate cortex
The cingulate cortex is a part of the brain situated in the medial aspect of the cortex. It includes the cortex of the cingulate gyrus, which lies immediately above the corpus callosum, and the continuation of this in the cingulate sulcus...

, and piriform cortex, as well as in vivo
In vivo
In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...

 in cat somatosensory and motor cortex
Motor cortex
Motor cortex is a term that describes regions of the cerebral cortex involved in the planning, control, and execution of voluntary motor functions.-Anatomy of the motor cortex :The motor cortex can be divided into four main parts:...

 by decreasing the conductance of voltage-dependent M currents and Ca2+
Calcium in biology
Calcium plays a pivotal role in the physiology and biochemistry of organisms and the cell. It plays an important role in signal transduction pathways, where it acts as a second messenger, in neurotransmitter release from neurons, contraction of all muscle cell types, and fertilization...

-dependent K+
Potassium in biology
Potassium is an essential mineral macronutrient and is the main intracellular ion for all types of cells.It is important in maintaining fluid and electrolyte balance in the bodies of humans and animals....

 currents.

Excitability and inhibition

Acetylcholine also has other effects on neurons. One effect is to cause a slow depolarization
Depolarization
In biology, depolarization is a change in a cell's membrane potential, making it more positive, or less negative. In neurons and some other cells, a large enough depolarization may result in an action potential...

by blocking a tonically-active K+ current, which increases neuronal excitability. Alternatively, acetylcholine can activate non-specific cation conductances to directly excite neurons. An effect upon postsynaptic M4-muscarinic ACh receptor
Muscarinic acetylcholine receptor M4
The muscarinic acetylcholine receptor M4, also known as the cholinergic receptor, muscarinic 4 , is a protein that, in humans, is encoded by the CHRM4 gene.-Function:...

s is to open inward-rectifier potassium ion channel
Inward-rectifier potassium ion channel
Inwardly rectifying potassium channels are a specific subset of potassium selective ion channels. To date, seven subfamilies have been identified in various mammalian cell types...

 (Kir) and cause inhibition. The influence of acetylcholine on specific neuron types can be dependent upon the duration of cholinergic stimulation. For instance, transient exposure to acetylcholine (up to several seconds) can inhibit cortical pyramidal neurons via M1 type muscarinic receptors that are linked to Gq-type G-protein alpha subunits. M1 receptor activation can induce calcium-release from intracellular stores, which then activate a calcium-activated potassium conductance which inhibits pyramidal neuron firing. On the other hand, tonic M1 receptor activation is strongly excitatory. Thus, ACh acting at one type of receptor can have multiple effects on the same postsynaptic neuron, depending on the duration of receptor activation. Recent experiments in behaving animals have demonstrated that cortical neurons indeed experience both transient and persistent changes in local acetylcholine levels during cue-detection behaviors.

In the cerebral cortex, tonic ACh inhibits layer 4 medium spiny neuron
Medium spiny neuron
The medium spiny neurons are a special type of inhibitory cells representing approximately 90% of the neurons within the corpus striatum of the basal ganglia. They play a key role in initiating and controlling movements of the body, limbs, and eyes....

s, the main targets of thalamocortical inputs while exciting pyramidal cell
Pyramidal cell
Pyramidal neurons are a type of neuron found in areas of the brain including cerebral cortex, the hippocampus, and in the amygdala. Pyramidal neurons are the primary excitation units of the mammalian prefrontal cortex and the corticospinal tract. Pyramidal neurons were first discovered and...

s in layers 2/3 and layer 5. This filters out weak sensory inputs in layer 4 and amplifies inputs that reach the layers 2/3 and layer L5 excitatory microcircuits. As a result, these layer-specific effects of ACh might function to improve the signal noise ratio of cortical processing. At the same time, acetylcholine acts through nicotinic receptors to excite certain groups of inhibitory interneurons in the cortex, which further dampen down cortical activity.

Another theory interprets acetylcholine neuromodulation in the neocortex as modulating the estimate of expected uncertainty, acting counter to norepinephrine
Norepinephrine
Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...

 (NE) signals for unexpected uncertainty. Both modulations would then decrease synaptic transition strength, but ACh would then be needed to counter the effects of NE in learning, a signal understood to be 'noisy'.

Synthesis and degradation

Acetylcholine is synthesized in certain neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

s by the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 choline acetyltransferase
Choline acetyltransferase
Choline acetyltransferase is an enzyme that is synthesized within the body of a neuron. It is then transferred to the nerve terminal via axoplasmic flow. The role of choline acetyltransferase is to join Acetyl-CoA to choline, resulting in the formation of the neurotransmitter acetylcholine...

 from the compounds choline
Choline
Choline is a water-soluble essential nutrient. It is usually grouped within the B-complex vitamins. Choline generally refers to the various quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation....

 and acetyl-CoA
Acetyl-CoA
Acetyl coenzyme A or acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main function is to convey the carbon atoms within the acetyl group to the citric acid cycle to be oxidized for energy production. In chemical structure, acetyl-CoA is the thioester...

.

The enzyme acetylcholinesterase
Acetylcholinesterase
"Acetylcholinesterase, also known as AChE or acetylcholine acetylhydrolase, is an enzyme that degrades the neurotransmitter acetylcholine, producing choline and an acetate group. It is mainly found at neuromuscular junctions and cholinergic nervous system, where its activity serves to terminate...

 converts acetylcholine into the inactive metabolites choline
Choline
Choline is a water-soluble essential nutrient. It is usually grouped within the B-complex vitamins. Choline generally refers to the various quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation....

 and acetate
Acetate
An acetate is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. Most of the approximately 5 billion kilograms of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of polymers. In...

. This enzyme is abundant in the synaptic cleft, and its role in rapidly clearing free acetylcholine from the synapse is essential for proper muscle function. Certain neurotoxins work by inhibiting acetylcholinesterase, thus leading to excess acetylcholine at the neuromuscular junction
Neuromuscular junction
A neuromuscular junction is the synapse or junction of the axon terminal of a motor neuron with the motor end plate, the highly-excitable region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscle's surface, ultimately causing the muscle to contract...

, thus causing paralysis of the muscles needed for breathing and stopping the beating of the heart.

Receptors

There are two main classes of acetylcholine receptor (AChR), nicotinic acetylcholine receptor
Nicotinic acetylcholine receptor
Nicotinic acetylcholine receptors, or nAChRs, are cholinergic receptors that form ligand-gated ion channels in the plasma membranes of certain neurons and on the postsynaptic side of the neuromuscular junction...

s (nAChR) and muscarinic acetylcholine receptor
Muscarinic acetylcholine receptor
Muscarinic receptors, or mAChRs, are acetylcholine receptors that form G protein-coupled in the plasma membranes of certain neurons and other cells...

s (mAChR). They are named for the ligands
Ligand (biochemistry)
In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. In a narrower sense, it is a signal triggering molecule, binding to a site on a target protein.The binding occurs by intermolecular forces, such as ionic bonds, hydrogen...

 used to activate the receptors.

Nicotinic

Nicotinic AChRs
Nicotinic acetylcholine receptor
Nicotinic acetylcholine receptors, or nAChRs, are cholinergic receptors that form ligand-gated ion channels in the plasma membranes of certain neurons and on the postsynaptic side of the neuromuscular junction...

 are ionotropic receptors
Ligand-gated ion channel
Ligand-gated ion channels are one type of ionotropic receptor or channel-linked receptor. They are a group of transmembrane ion channels that are opened or closed in response to the binding of a chemical messenger , such as a neurotransmitter.The binding site of endogenous ligands on LGICs...

 permeable to sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

, potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

, and chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

 ions. They are stimulated by nicotine
Nicotine
Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of the dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves...

 and acetylcholine. They are of two main types, muscle type and neuronal type. The former can be selectively blocked by curare
Curare
Curare is a common name for various arrow poisons originating from South America. The three main types of curare are:* tubocurare...

 and the latter by hexamethonium
Hexamethonium
Hexamethonium is a ganglionic blocker, a nicotinic nACh receptor antagonist that acts in autonomic ganglia by binding mostly in or on the NN receptor, and not the acetylcholine binding site itself...

. The main location of nicotinic AChRs is on muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 end plates, autonomic ganglia (both sympathetic and parasympathetic), and in the CNS.

Myasthenia gravis

The disease myasthenia gravis
Myasthenia gravis
Myasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability...

, characterized by muscle weakness and fatigue, occurs when the body inappropriately produces antibodies
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...

 against acetylcholine nicotinic receptors, and thus inhibits proper acetylcholine signal transmission. Over time, the motor end plate is destroyed. Drugs that competitively inhibit acetylcholinesterase (e.g., neostigmine, physostigmine, or primarily pyridostigmine) are effective in treating this disorder. They allow endogenously-released acetylcholine more time to interact with its respective receptor before being inactivated by acetylcholinesterase in the gap junction
Gap junction
A gap junction or nexus is a specialized intercellular connection between a multitude of animal cell-types. It directly connects the cytoplasm of two cells, which allows various molecules and ions to pass freely between cells....

.

Muscarinic

Muscarinic receptors are metabotropic, and affect neurons over a longer time frame. They are stimulated by muscarine
Muscarine
Muscarine, L--muscarine, or muscarin is a natural product found in certain mushrooms, particularly in Inocybe and Clitocybe species, such as the deadly C. dealbata. Mushrooms in the genera Entoloma and Mycena have also been found to contain levels of muscarine which can be dangerous if ingested...

 and acetylcholine, and blocked by atropine
Atropine
Atropine is a naturally occurring tropane alkaloid extracted from deadly nightshade , Jimson weed , mandrake and other plants of the family Solanaceae. It is a secondary metabolite of these plants and serves as a drug with a wide variety of effects...

. Muscarinic receptors are found in both the central nervous system and the peripheral nervous system, in heart, lungs, upper GI tract and sweat glands. Extracts from the plant Deadly nightshade
Deadly nightshade
Atropa belladonna or Atropa bella-donna, commonly known as Belladonna, Devil's Berries, Death Cherries or Deadly Nightshade, is a perennial herbaceous plant in the family Solanaceae, native to Europe, North Africa, and Western Asia. The foliage and berries are extremely toxic, containing tropane...

 included this compound (atropine), and the blocking of the muscarinic AChRs increases pupil size as used for attractiveness in many European cultures in the past. Now, ACh is sometimes used during cataract
Cataract
A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light...

 surgery to produce rapid constriction of the pupil. It must be administered intraocularly because cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...

l cholinesterase
Cholinesterase
In biochemistry, cholinesterase is a family of enzymes that catalyze the hydrolysis of the neurotransmitter acetylcholine into choline and acetic acid, a reaction necessary to allow a cholinergic neuron to return to its resting state after activation.-Types:...

 metabolizes topically-administered ACh before it can diffuse into the eye. It is sold by the trade name Miochol-E (CIBA Vision). Similar drugs are used to induce mydriasis
Mydriasis
Mydriasis is a dilation of the pupil due to disease, trauma or the use of drugs. Normally, the pupil dilates in the dark and constricts in the light to respectively improve vividity at night and to protect the retina from sunlight damage during the day...

 (dilation of the pupil), in cardiopulmonary resuscitation
Cardiopulmonary resuscitation
Cardiopulmonary resuscitation is an emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest. It is indicated in those who are unresponsive...

 and many other situations.

Drugs acting on the acetylcholine system

Blocking, hindering or mimicking the action of acetylcholine has many uses in medicine. Drugs acting on the acetylcholine system are either agonists to the receptors, stimulating the system, or antagonists, inhibiting it.

ACh receptor agonists/antagonists

Acetylcholine receptor agonists and antagonists can either have an effect directly on the receptors or exert their effects indirectly, e.g., by affecting the enzyme acetylcholinesterase
Acetylcholinesterase
"Acetylcholinesterase, also known as AChE or acetylcholine acetylhydrolase, is an enzyme that degrades the neurotransmitter acetylcholine, producing choline and an acetate group. It is mainly found at neuromuscular junctions and cholinergic nervous system, where its activity serves to terminate...

, which degrades the receptor ligand. Agonists increase the level of receptor activation, antagonists reduce it.

Associated disorders

ACh Receptor Agonists are used to treat myasthenia gravis
Myasthenia gravis
Myasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability...

 and Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...

.
Alzheimer's disease

Since α4β2 AchRs are reduced in Alzheimer's disease, drugs that inhibit acetylcholinesterase
Acetylcholinesterase inhibitor
An acetylcholinesterase inhibitor or anti-cholinesterase is a chemical that inhibits the cholinesterase enzyme from breaking down acetylcholine, increasing both the level and duration of action of the neurotransmitter acetylcholine.- Uses :Acetylcholinesterase inhibitors:* Occur naturally as...

, e.g. galantamine hydrobromide (a competitive and reversible cholinesterase inhibitor), are commonly used in the treatment of that disease.

Direct acting

These are drugs that mimic acetylcholine on the receptor. In low doses, they stimulate the receptors, in high they numb them due to depolarisation block.
  • Acetyl l-carnitine
    Acetylcarnitine
    Acetyl-L-carnitine or ALCAR, is an acetylated form of L-carnitine. It is a dietary supplement and naturally occurs in plants and animals.- Biochemical Production and Action :ALCAR is an acetylated derivative of L-carnitine...

  • Acetylcholine itself
  • Bethanechol
    Bethanechol
    Bethanechol is a parasympathomimetic choline carbamate that selectively stimulates muscarinic receptors without any effect on nicotinic receptors. Unlike acetylcholine, bethanechol is not hydrolyzed by cholinesterase and will therefore have a long duration of action. Bethanechol does not involve...

  • Carbachol
    Carbachol
    Carbachol , also known as carbamylcholine, is a drug that binds and activates the acetylcholine receptor. Thus it is classified as a cholinergic agonist. It is primarily used for various ophthalmic purposes, such as for treating glaucoma, or for use during ophthalmic surgery...

  • Cevimeline
  • Muscarine
    Muscarine
    Muscarine, L--muscarine, or muscarin is a natural product found in certain mushrooms, particularly in Inocybe and Clitocybe species, such as the deadly C. dealbata. Mushrooms in the genera Entoloma and Mycena have also been found to contain levels of muscarine which can be dangerous if ingested...

  • Nicotine
    Nicotine
    Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of the dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves...

  • Pilocarpine
    Pilocarpine
    Pilocarpine is a parasympathomimetic alkaloid obtained from the leaves of tropical American shrubs from the genus Pilocarpus. It is a non-selective muscarinic receptor agonist in the parasympathetic nervous system, which acts therapeutically at the muscarinic acetylcholine receptor M3 due to its...

  • Suberylcholine
  • Suxamethonium

Cholinesterase inhibitors

Most indirect acting ACh receptor agonists work by inhibiting the enzyme acetylcholinesterase
Acetylcholinesterase
"Acetylcholinesterase, also known as AChE or acetylcholine acetylhydrolase, is an enzyme that degrades the neurotransmitter acetylcholine, producing choline and an acetate group. It is mainly found at neuromuscular junctions and cholinergic nervous system, where its activity serves to terminate...

. The resulting accumulation of acetylcholine causes continuous stimulation of the muscles, glands, and central nervous system.

They are examples of enzyme inhibitors, and increase the action of acetylcholine by delaying its degradation; some have been used as nerve agent
Nerve agent
Nerve agents are a class of phosphorus-containing organic chemicals that disrupt the mechanism by which nerves transfer messages to organs...

s (Sarin
Sarin
Sarin, or GB, is an organophosphorus compound with the formula [2CHO]CH3PF. It is a colorless, odorless liquid, which is used as a chemical weapon. It has been classified as a weapon of mass destruction in UN Resolution 687...

 and VX
VX (nerve agent)
VX, IUPAC name O-ethyl S-[2-ethyl] methylphosphonothioate, is an extremely toxic substance whose only application is in chemical warfare as a nerve agent. As a chemical weapon, it is classified as a weapon of mass destruction by the United Nations in UN Resolution 687...

 nerve gas) or pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

s (organophosphates and the carbamates). In clinical use, they are administered to reverse the action of muscle relaxant
Muscle relaxant
A muscle relaxant is a drug which affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasms, pain, and hyperreflexia. The term "muscle relaxant" is used to refer to two major therapeutic groups: neuromuscular blockers and spasmolytics...

s, to treat myasthenia gravis
Myasthenia gravis
Myasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability...

, and to treat symptoms of Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...

 (rivastigmine
Rivastigmine
Rivastigmine is a parasympathomimetic or cholinergic agent for the treatment of mild to moderate dementia of the Alzheimer’s type and dementia due to Parkinson's disease. The drug can be administered orally or via a transdermal patch; the latter form reduces the prevalence of side effects, which...

, which increases cholinergic activity in the brain).
Reversible

The following substances reversibly inhibit the enzyme acetylcholinesterase
Acetylcholinesterase
"Acetylcholinesterase, also known as AChE or acetylcholine acetylhydrolase, is an enzyme that degrades the neurotransmitter acetylcholine, producing choline and an acetate group. It is mainly found at neuromuscular junctions and cholinergic nervous system, where its activity serves to terminate...

 (which breaks down acetylcholine), thereby increasing acetylcholine levels.
  • Many medications in Alzheimer's disease
    Alzheimer's disease
    Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...

    • Donepezil
      Donepezil
      Donepezil, marketed under the trade name Aricept by its developer Eisai and partner Pfizer, is a centrally acting reversible acetylcholinesterase inhibitor. Its main therapeutic use is in the palliative treatment of mild to moderate Alzheimer's disease. Common side effects include...

    • Galantamine
      Galantamine
      Galantamine is used for the treatment of mild to moderate Alzheimer’s disease and various other memory impairments, in particular those of vascular origin...

    • Rivastigmine
      Rivastigmine
      Rivastigmine is a parasympathomimetic or cholinergic agent for the treatment of mild to moderate dementia of the Alzheimer’s type and dementia due to Parkinson's disease. The drug can be administered orally or via a transdermal patch; the latter form reduces the prevalence of side effects, which...

    • Tacrine
      Tacrine
      Tacrine is a centrally acting anticholinesterase and indirect cholinergic agonist . It was the first centrally-acting cholinesterase inhibitor approved for the treatment of Alzheimer's disease, and was marketed under the trade name Cognex. Tacrine was first synthesised by Adrien Albert at the...

  • Edrophonium
    Edrophonium
    Edrophonium is a readily reversible acetylcholinesterase inhibitor. It prevents breakdown of the neurotransmitter acetylcholine and acts by competitively inhibiting the enzyme acetylcholinesterase, mainly at the neuromuscular junction...

     (differs myasthenic and cholinergic crisis
    Cholinergic crisis
    A cholinergic crisis is an over-stimulation at a neuromuscular junction due to an excess of acetylcholine , as of a result of the inactivity of the AChE enzyme, which normally breaks down acetylcholine. This is a consequence of some types of nerve gas,...

    )
  • Neostigmine
    Neostigmine
    Neostigmine is a parasympathomimetic that acts as a reversible acetylcholinesterase inhibitor.- Synthesis :Neostigmine was first synthesized by Aeschlimann and Reinert in 1931....

     (commonly used to reverse the effect of neuromuscular blockers used in anaesthesia, or less often in myasthenia gravis
    Myasthenia gravis
    Myasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability...

    )
  • Physostigmine
    Physostigmine
    Physostigmine is a parasympathomimetic alkaloid, specifically, a reversible cholinesterase inhibitor. It occurs naturally in the Calabar bean....

     (in glaucoma
    Glaucoma
    Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...

     and anticholinergic
    Anticholinergic
    An anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. An example of an anticholinergic is dicycloverine, and the classic example is atropine....

     drug overdoses)
  • Pyridostigmine
    Pyridostigmine
    Pyridostigmine is a parasympathomimetic and a reversible cholinesterase inhibitor. Since it is a quaternary amine, it is poorly absorbed in the gut and does not cross the blood-brain barrier, except possibly in stressful conditions.-Mode of action:...

     (in myasthenia gravis
    Myasthenia gravis
    Myasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability...

  • Carbamate
    Carbamate
    Carbamates are organic compounds derived from carbamic acid . A carbamate group, carbamate ester, and carbamic acids are functional groups that are inter-related structurally and often are interconverted chemically. Carbamate esters are also called urethanes.-Synthesis:Carbamic acids are derived...

     insecticides (e.g., Aldicarb
    Aldicarb
    Aldicarb is a carbamate insecticide which is the active substance in the pesticide Temik. It is effective against thrips, aphids, spider mites, lygus, fleahoppers, and leafminers, but is primarily used as a nematicide. Aldicarb is a cholinesterase inhibitor which prevents the breakdown of...

    )
  • Huperzine A
    Huperzine A
    Huperzine A is a naturally occurring sesquiterpene alkaloid compound found in the plant firmoss Huperzia serrata. and in varying quantities in other Husperzia spp.including H. elmeri, H. carinat, H. aqualupian,...


Irreversible

Semi-permanently inhibit the enzyme acetylcholinesterase.
  • Echothiophate
    Echothiophate
    Echothiophate is a parasympathomimetic and a phosphorothioate. It is an acetylcholinesterase inhibitor.- Uses :It is used as an ocular antihypertensive in the treatment of chronic glaucoma and, in some cases, accommodative esotropia...

  • Isofluorophate
  • Organophosphate
    Organophosphate
    An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...

     Insecticides (Malathion
    Malathion
    Malathion is an organophosphate parasympathomimetic which binds irreversibly to cholinesterase. Malathion is an insecticide of relatively low human toxicity, however one recent study has shown that children with higher levels of organophosphate pesticide metabolites in their urine are more likely...

    , Parathion
    Parathion
    Parathion, also called parathion-ethyl or diethyl parathion, is an organophosphate compound. It is a potent insecticide and acaricide. It was originally developed by IG Farben in the 1940s. It is highly toxic to non-target organisms, including humans. Its use is banned or restricted in many...

    , Azinphos methyl, Chlorpyrifos
    Chlorpyrifos
    Chlorpyrifos is a crystalline organophosphate insecticide that inhibits acetylcholinesterase and is used to control insect pests. It is known by many trade names...

    , among others)
  • Organophosphate-containing nerve agents (e.g., Sarin
    Sarin
    Sarin, or GB, is an organophosphorus compound with the formula [2CHO]CH3PF. It is a colorless, odorless liquid, which is used as a chemical weapon. It has been classified as a weapon of mass destruction in UN Resolution 687...

    , VX
    VX (nerve agent)
    VX, IUPAC name O-ethyl S-[2-ethyl] methylphosphonothioate, is an extremely toxic substance whose only application is in chemical warfare as a nerve agent. As a chemical weapon, it is classified as a weapon of mass destruction by the United Nations in UN Resolution 687...

    )


Victims of organophosphate-containing nerve agents commonly die of suffocation as they cannot relax their diaphragm
Thoracic diaphragm
In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm , is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...

.

Ganglionic blockers

  • Mecamylamine
    Mecamylamine
    Mecamylamine is a nonselective and noncompetitive antagonist of the nicotinic acetylcholine receptors that was introduced in the 1950s as an antihypertensive agent.- Uses :...

  • Hexamethonium
    Hexamethonium
    Hexamethonium is a ganglionic blocker, a nicotinic nACh receptor antagonist that acts in autonomic ganglia by binding mostly in or on the NN receptor, and not the acetylcholine binding site itself...

  • Nicotine
    Nicotine
    Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of the dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves...

     (in high doses)
  • Trimethaphan
    Trimethaphan
    Trimetaphan camsilate or trimethaphan camsylate , trade name Arfonad, is a drug that counteracts cholinergic transmission at the ganglion type of nicotinic receptors of the autonomic ganglia and therefore blocks both the sympathetic nervous system and the parasympathetic nervous system...


Neuromuscular blockers

  • Atracurium
    Atracurium
    Atracurium besylate is a neuromuscular-blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical...

  • Cisatracurium
    Cisatracurium
    Cisatracurium is a neuromuscular-blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation...

  • Doxacurium
  • Metocurine
    Metocurine
    Metocurine is a muscle relaxant through neuromuscular blockade.It is excreted entirely through the kidneys and therefore should not be used in patients with renal failure....

  • Mivacurium
    Mivacurium
    Mivacurium chloride is a short-duration non-depolarizing neuromuscular-blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during...

  • Pancuronium
    Pancuronium
    Pancuronium is a muscle relaxant with various purposes. It is the second of three drugs administered during most lethal injections in the United States.- Mode of action :...

  • Rocuronium
    Rocuronium
    Rocuronium is an aminosteroid non-depolarizing neuromuscular blocker or muscle relaxant used in modern anaesthesia, to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation.Introduced in 1994, rocuronium has...

  • Succinylcholine
  • Tubocurarine
    Tubocurarine
    Tubocurarine is a neuromuscular-blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in anesthesia to provide skeletal muscle relaxation during surgery or mechanical ventilation...

  • Vecuronium
    Vecuronium
    Vecuronium is a muscle relaxant in the category of non-depolarizing blocking agents. Vecuronium bromide is indicated as an adjunct to general anesthesia, to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation...

  • Hemicholine

Synthesis inhibitors

  • Organic mercurial
    Mercury (element)
    Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

     compounds, such as methylmercury
    Methylmercury
    Methylmercury is an organometallic cation with the formula . It is a bioaccumulative environmental toxicant.-Structure:...

    , have a high affinity for sulfhydryl groups
    Thiol
    In organic chemistry, a thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl group...

    , which causes dysfunction of the enzyme choline acetyltransferase. This inhibition may lead to acetylcholine deficiency, and can have consequences on motor function.

Release inhibitors

  • Botulin acts by suppressing the release of acetylcholine; where the venom from a black widow spider (alpha-latrotoxin
    Alpha-latrotoxin
    α-Latrotoxin can naturally be found in widow spiders of the genus Latrodectus. The most famous of those spiders are the black widows, Latrodectus mactans. The venom of widow spiders contains several protein toxins, called latrotoxins, which selectively target against either vertebrates, insects...

    ) has the reverse effect.

External links

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