parasympathetic nervous system
The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system.
The autonomic nervous system is responsible for regulat ...
(PSNS). These chemicals are also called cholinergic drugs because
acetylcholine
Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Par ...
(ACh) is the
neurotransmitter
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell.
Neurotra ...
used by the PSNS. Chemicals in this family can act either directly by stimulating the nicotinic or muscarinic receptors (thus mimicking acetylcholine), or indirectly by inhibiting cholinesterase, promoting acetylcholine release, or other mechanisms. Common uses of parasympathomimetics include
glaucoma
Glaucoma is a group of eye diseases that can lead to damage of the optic nerve. The optic nerve transmits visual information from the eye to the brain. Glaucoma may cause vision loss if left untreated. It has been called the "silent thief of ...
tear gas
Tear gas, also known as a lachrymatory agent or lachrymator (), sometimes colloquially known as "mace" after the Mace (spray), early commercial self-defense spray, is a chemical weapon that stimulates the nerves of the lacrimal gland in the ey ...
, and
insecticide
Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...
Structure activity relationships for parasympathomimetic drugs
For a cholinergic agent, the following criteria describe the structure activity relationship:
# Ing's Rule of 5: there should be no more than five atoms between the nitrogen and the terminal hydrogen for muscarinic (or cholinergic) activity;
# the molecule must possess a nitrogen atom capable of bearing a positive charge, preferably a quaternary ammonium salt;
# for maximum potency, the size of the alkyl groups substituted on the nitrogen should not exceed the size of a methyl group;
# the molecule should have an oxygen atom, preferably an ester-like oxygen capable of participating in a hydrogen bond;
# there should be a two-carbon unit between the oxygen atom and the nitrogen atom.
Pharmaceuticals/Supplements
Direct-acting
These act by stimulating the nicotinic or muscarinic receptors.
* Choline esters
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Acetylcholine
Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Par ...
Carbachol
Carbachol, also known as carbamylcholine and sold under the brand name Miostat among others, is a cholinomimetic drug that binds and activates acetylcholine receptors. Thus it is classified as a cholinergic agonist. It is primarily used for v ...
Arecoline
Arecoline is a cholinergic agent, stimulant, and natural product, naturally occurring alkaloid found in areca nut, areca (betel) nuts of the areca palm (''Areca catechu'') found in South Asia, South and Southeast Asia. Its effects, depending on ...
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Nicotine
Nicotine is a natural product, naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and ''Duboisia hopwoodii'') and is widely used recreational drug use, recreationally as a stimulant and anxiolytic. As ...
Indirect acting parasympathomimetic substances may be either reversible cholinesterase inhibitors, irreversible cholinesterase inhibitors or substances that promote ACh release or anti-adrenergics. The latter inhibits the antagonistic system, the
sympathetic nervous system
The sympathetic nervous system (SNS or SANS, sympathetic autonomic nervous system, to differentiate it from the somatic nervous system) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous sy ...
Caffeine
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class and is the most commonly consumed Psychoactive drug, psychoactive substance globally. It is mainly used for its eugeroic (wakefulness pr ...
(non-competitive)
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Huperzine A
Huperzine A, a Lycopodium alkaloid, was first isolated in 1983 from ''Huperzia serrata'', a plant used in Chinese folk medicine. Huperzine A also exists in other Huperzia species, including ''H. elmeri'', ''H. carinat'', and ''H. aqualupian'' ...
Domperidone
Domperidone, sold under the brand name Motilium among others, is a dopamine antagonist medication which is used to treat nausea and vomiting and certain gastrointestinal problems like gastroparesis (delayed gastric emptying). It raises the ...
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Metoclopramide
Metoclopramide is a medication used to treat nausea, vomiting, gastroparesis, and gastroesophageal reflux disease. It is also used to treat migraine headaches.
Common side effects include feeling tired, diarrhea, akathisia, and tardive dyski ...
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Risperidone
Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder, as well as aggressive and self-injurious behaviors associated with autism spectrum disorder. It is t ...
beta blocker
Beta blockers, also spelled β-blockers, are a class of medications that are predominantly used to manage abnormal heart rhythms ( arrhythmia), and to protect the heart from a second heart attack after a first heart attack ( secondary prevention ...
agonist
An agonist is a chemical that activates a Receptor (biochemistry), receptor to produce a biological response. Receptors are Cell (biology), cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an R ...
negative feedback
Negative feedback (or balancing feedback) occurs when some function (Mathematics), function of the output of a system, process, or mechanism is feedback, fed back in a manner that tends to reduce the fluctuations in the output, whether caused ...
negative feedback
Negative feedback (or balancing feedback) occurs when some function (Mathematics), function of the output of a system, process, or mechanism is feedback, fed back in a manner that tends to reduce the fluctuations in the output, whether caused ...
)
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Propranolol
Propranolol is a medication of the beta blocker class. It is used to treat hypertension, high blood pressure, some types of cardiac dysrhythmia, irregular heart rate, thyrotoxicosis, capillary hemangiomas, akathisia, performance anxiety, and ...
antagonist
An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain.Metoprolol ( β-receptor
antagonist
An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain.Atenolol
Atenolol is a beta blocker medication primarily used to treat high blood pressure and angina, heart-associated chest pain. Although used to treat high blood pressure, it does not seem to improve mortality rate, mortality in those with the condi ...