Muscarinic Receptors
Muscarinic Receptors - Related Videos
01:25
Cholinergic Receptors: Muscarinic
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2023
The pharmacological actions of acetylcholine are elicited via its binding to two families of cholinergic receptors or cholinoceptors, namely, muscarinic and nicotinic receptors. Muscarinic receptors are G protein-coupled receptors and have five subtypes, M1–M5. All mAChR subtypes are activated by acetylcholine and blocked by the antagonist, atropine. The subtypes M1, M3, and M5 couple with the Gq subunit and activate the phospholipase C (PLC) activity, mobilizing intracellular Ca2+. Activation...
01:20
Antiasthma Drugs: Muscarinic Receptor Antagonists
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2024
Muscarinic receptor antagonists, also known as antimuscarinic agents, are a class of bronchodilators used to treat asthma, although they are more commonly used to treat COPD. They work by inhibiting the action of acetylcholine (ACh), a neurotransmitter, on muscarinic receptors found in the airways. Antimuscarinic agents compete with ACh for the same binding site on the muscarinic receptors. By binding to these receptors, they inhibit the downstream effects of ACh and block the parasympathetic...
07:09
Subcutaneous Administration of Muscarinic Antagonists and Triple-Immunostaining of the Levator Auris Longus Muscle in Mice
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Cited by 7 •
2011
We describe procedures for repeated administration of inhibitors of muscarinic signaling to the levator auris longus (LAL) muscle of young adult mice and for subsequent immunostaining of its neuromuscular junctions (NMJs) in wholemounts. The LAL muscle has unique advantages for revealing in vivo pharmacological effects on NMJs.
11:45
Quantifying Agonist Activity at G Protein-coupled Receptors
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Cited by 10 •
2011
A method for estimating the affinity constant of an agonist for the active state (Kb) of a G protein-coupled receptor is described. The analysis provides absolute or relative measures of Kb depending on whether constitutive receptor activation is measurable. Our method applies to various responses downstream from receptor activation.
12:03
Receptor Autoradiography Protocol for the Localized Visualization of Angiotensin II Receptors
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Cited by 14 •
2016
Here we present a protocol to describe the localization of angiotensin II Type 1 receptors in the rat brain by quantitative, densitometric, in vitro receptor autoradiography using an iodine-125 labeled analog of angiotensin II.
FAQs
M1, M3, and M5 typically couple to Gq, activating phospholipase C, whereas M2 and M4 couple to Gi, inhibiting adenylyl cyclase and regulating ion channels. This signaling split helps explain why different receptor subtypes can influence distinct processes, including smooth-muscle contraction, glandular secretion, heart-rate control, and neuronal activity.
The distinction links receptor subtype activation to different intracellular signaling mechanisms. Gq-associated subtypes primarily engage phospholipase C, while Gi-associated subtypes affect adenylyl cyclase and ion channels. Understanding these pathways helps pharmacologists relate a drug’s receptor preference to outcomes in the heart, smooth muscle, glands, or nervous system.
Subtype selectivity could allow a drug to influence a desired physiological pathway while limiting effects produced through other muscarinic subtypes. This is important because the receptor family participates in several systems at once, including cardiac, smooth-muscle, glandular, and neuronal functions. Greater selectivity is therefore pursued to reduce unwanted effects.
Drugs that activate muscarinic receptors can enhance signaling through these receptors, whereas blocking drugs prevents or reduces their effects. Pharmacologists use this opposing strategy to influence processes such as glandular secretion, smooth-muscle activity, heart rate, and neuronal function. The appropriate approach depends on whether receptor activity needs to be promoted or restrained.
Targeting these receptors can alter heart rate, smooth-muscle contraction, glandular secretion, and neuronal activity. Those effects provide a pharmacological basis for studying and treating disorders involving the eye, airways, gastrointestinal tract, cardiovascular system, and nervous system. The specific outcome depends on which receptor-linked pathway is activated or blocked.
Muscarinic receptor drugs have applications in glaucoma, asthma, gastrointestinal disorders, and bradycardia, and they are also relevant to cognitive or neurological disease. These uses reflect the broad physiological reach of acetylcholine signaling. Pharmacology research continues to examine how subtype-selective activation or blockade might improve therapeutic effects while limiting adverse consequences.