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Cholinergic agents are compounds which mimic the action of acetylcholine and/or butyrylcholine. [1] In general, the word " choline " describes the various quaternary ammonium salts containing the N , N , N -trimethylethanolammonium cation .
A parasympathomimetic drug, sometimes called a cholinomimetic drug [1] or cholinergic receptor stimulating agent, [2] is a substance that stimulates the parasympathetic nervous system (PSNS). [ 3 ] [ 2 ] These chemicals are also called cholinergic drugs because acetylcholine (ACh) is the neurotransmitter used by the PSNS.
According to their site of actions, cholinergic blocking drugs can be classified into two general types — antimuscarinic and antinicotinic agents. [1] Antimuscarinic agents (also known as muscarinic antagonists), including atropine and hyoscine, block acetylcholine at the muscarinic acetylcholine receptors.
The most serious and troublesome side effects of these classical antipsychotics are movement disorders that resemble the symptoms of Parkinson's disease, because the neuroleptics antagonize dopamine receptors broadly, also reducing the normal dopamine-mediated inhibition of cholinergic cells in the striatum.
The muscarine cholinergic receptor activates a G-protein when bound to extracellular ACh. The alpha subunit of the G-protein activates guanylate cyclase (inhibiting the effects of intracellular cAMP) while the beta-gamma subunit activates the K-channels and therefore hyperpolarize the cell. This causes a decrease in cardiac activity.
The muscarinic acetylcholine receptor M 2, also known as the cholinergic receptor, muscarinic 2, is a muscarinic acetylcholine receptor that in humans is encoded by the CHRM2 gene. [5] Multiple alternatively spliced transcript variants have been described for this gene. [5] It is G i-coupled, reducing intracellular levels of cAMP.
Several different terms are used to refer to the molecules that bind receptors, such as ligand, agonist, or transmitter. As well as the endogenous agonist acetylcholine, agonists of the nAChR include nicotine, epibatidine, and choline. Nicotinic antagonists that block the receptor include mecamylamine, dihydro-β-erythroidine, and hexamethonium ...
Withdrawal effects may also occur when switching a person from one antipsychotic to another, (it is presumed due to variations of potency and receptor activity). Such withdrawal effects can include cholinergic rebound, an activation syndrome, and motor syndromes including dyskinesias.