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Acetylcholine: Difference between revisions
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[[File:Acetylcholine. | {{stub}}[[File:Acetylcholine.svg|239px|thumb|right|Skeletal structure of an acetylcholine molecule.]] | ||
'''Acetylcholine''' is an organic cation that acts as a [[neurotransmitter]] in many organisms, including humans. | '''Acetylcholine''' is an organic cation that acts as a [[neurotransmitter]] in many organisms, including humans. | ||
Acetylcholine is also the principal neurotransmitter in all autonomic ganglia. | Acetylcholine is also the principal neurotransmitter in all autonomic ganglia. | ||
In cardiac tissue acetylcholine neurotransmission has an inhibitory effect, which lowers heart rate. However, acetylcholine also behaves as an excitatory neurotransmitter at neuromuscular junctions in skeletal muscle. | In cardiac tissue, acetylcholine neurotransmission has an inhibitory effect, which lowers heart rate. However, acetylcholine also behaves as an excitatory neurotransmitter at neuromuscular junctions in skeletal muscle. | ||
==Chemistry== | ==Chemistry== | ||
It is an ester of acetic acid and choline. The molecule is a polyatomic cation, meaning that it is a positive ion comprising of more than one atom. | It is an ester of acetic acid and [[choline]]. The molecule is a polyatomic cation, meaning that it is a positive ion comprising of more than one atom. It contains the quaternary ammonium cation. Acetylcholine does not penetrate lipid membranes, this is because of the charged ammonium group which gives the substance a highly polar molecule. As a consequence of this, if the substance is introduced externally it won't penetrate the blood-brain barrier (BBB), it will then remain in the extracellular space waiting to get broken down in the body and excreted. | ||
==The cholinergic system== | ==The cholinergic system== | ||
Acetylcholine acts as a neurotransmitter in both the peripheral nervous system (PNS) and central nervous system (CNS). Acetylcholine is also one of many neurotransmitters in the autonomic nervous system (ANS) and is the only neurotransmitter used in the motor division of the somatic nervous system (sensory neurons use glutamate and various peptides at their synapses). | Acetylcholine acts as a neurotransmitter in both the peripheral nervous system (PNS) and central nervous system (CNS). Acetylcholine is also one of many neurotransmitters in the autonomic nervous system (ANS) and is the only neurotransmitter used in the motor division of the somatic nervous system (sensory neurons use glutamate and various peptides at their synapses). It functions as both a neurotransmitter and a neuromodulator. The cholinergic areas of the brain have distinct critical functions which some of them are; attention, memory (long- and short term), motivation, and arousal.<ref>{{cite book | vauthors=((Kapalka, G. M.)) | date= 2010 | chapter=Nutritional and Herbal Therapies for Children and Adolescents | title=Substances Involved in Neurotransmission | publisher=Elsevier | pages=71–99 | url=https://linkinghub.elsevier.com/retrieve/pii/B9780123749277000042 | doi=10.1016/B978-0-12-374927-7.00004-2 | isbn=9780123749277}}</ref> | ||
===Drugs targeting the cholinergic system=== | ===Drugs targeting the cholinergic system=== | ||
====[[Agonists]]==== | |||
An acetylcholine receptor [[agonist]] works by increasing the level of receptor activation, either directly or indirectly. Direct agonists work by imitating the neurotransmitter. [[Muscarine]], an alkaloid found in a variety of mushrooms including [[Amanita muscaria|''Amanita muscaria'']], acts as a direct agonist of muscarinic acetylcholine receptors. [[Nicotine]], an alkaloid found in [[Nicotiana tabacum|''Nicotiana tabacum'']], acts as a direct agonist of nicotinic acetylcholine receptors. Indirect agonists most often work by inhibiting the enzyme acetylcholinesterase; this enzyme breaks down acetylcholine, and therefore inhibition of it increases activation of cholinergic receptors. The stimulant drug caffeine is an indirect agonist, as is [[THC]]. More potent agents include [[donepezil]] and [[galantamine]], both of which are used in the treatment of Alzheimer's disease. These work by blocking acetylcholinesterase, which is an enzyme that breaks down acetylcholine, leading to an increased build up over time. These medications are non-competitive, reversible inhibitors of acetylcholinesterase. [[Nerve agent|Nerve agents]] like [[sarin]] irreversibly inhibit the enzyme, allowing a potentially lethal accumulation of acetylcholine to occur. | An acetylcholine receptor [[agonist]] works by increasing the level of receptor activation, either directly or indirectly. Direct agonists work by imitating the neurotransmitter. [[Muscarine]], an alkaloid found in a variety of mushrooms including [[Amanita muscaria|''Amanita muscaria'']], acts as a direct agonist of muscarinic acetylcholine receptors. [[Nicotine]], an alkaloid found in [[Nicotiana tabacum|''Nicotiana tabacum'']], acts as a direct agonist of nicotinic acetylcholine receptors. Indirect agonists most often work by inhibiting the enzyme acetylcholinesterase; this enzyme breaks down acetylcholine, and therefore inhibition of it increases activation of cholinergic receptors. The stimulant drug caffeine is an indirect agonist, as is [[THC]]. More potent agents include [[donepezil]] and [[galantamine]], both of which are used in the treatment of Alzheimer's disease. These work by blocking acetylcholinesterase, which is an enzyme that breaks down acetylcholine, leading to an increased build up over time. These medications are non-competitive, reversible inhibitors of acetylcholinesterase. [[Nerve agent|Nerve agents]] like [[sarin]] irreversibly inhibit the enzyme, allowing a potentially lethal accumulation of acetylcholine to occur. | ||
An acetylcholine receptor [[antagonist]] works by attaching to acetylcholine receptors to prevent agonists binding. The [[deliriant]] drugs [[atropine]], [[scopolamine]] and [[ | Other substances like [[racetam|racetams]] can preserve acetylcholine regulation in instances of cognitive impairment such as [[deliriant]] intoxication or cognitive deficits associated with traumatic brain injury. | ||
====[[Precursors]]==== | |||
Supplements such as [[choline bitartrate]], [[citicoline]], [[alpha-GPC]], and [[phosphatidylcholine]] provide choline, the direct building block for acetylcholine. Supplementing them may allow ACh to accumulate at higher levels than that which it otherwise would. Choline is an essential dietary nutrient; for food sources and recommended intake levels, see {{Wikipedia|choline}}.<ref>{{cite journal | vauthors=((Zeisel, S. H.)), ((Costa, K.-A. da)) | journal=Nutrition Reviews | title=Choline: an essential nutrient for public health | volume=67 | issue=11 | pages=615–623 | date= November 2009 | url=https://academic.oup.com/nutritionreviews/article-lookup/doi/10.1111/j.1753-4887.2009.00246.x | issn=00296643 | doi=10.1111/j.1753-4887.2009.00246.x}}</ref> | |||
====[[Antagonists]]==== | |||
An acetylcholine receptor [[antagonist]] works by attaching to acetylcholine receptors to prevent agonists binding. The [[deliriant]] drugs [[atropine]], [[scopolamine]] (both found in Datura) and [[diphenhydramine]] all act as antagonists upon muscarinic acetylcholine receptors, as does the chemical incapacitating agent 3-Quinuclidinyl benzilate, better known as BZ. | |||
==See also== | ==See also== | ||
*[[Responsible use]] | |||
*[[Choline]] | |||
*[[Serotonin]] | *[[Serotonin]] | ||
*[[Dopamine]] | *[[Dopamine]] | ||
*[[Glutamate]] | *[[Glutamate]] | ||
*[[Adrenaline]] | *[[Adrenaline]] | ||
*[[GABA]] | *[[GABA]] | ||
*[[Neurotransmitter]] | *[[Neurotransmitter]] | ||
==External links== | |||
*[https://en.wikipedia.org/wiki/Acetylcholine Acetylcholine (Wikipedia)] | |||
==References== | ==References== | ||
{{references}} | {{references}} | ||
[[Category: | [[Category:Neurotransmitter]] | ||
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