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Related Concept Videos

Cholinergic Antagonists: Pharmacological Actions01:28

Cholinergic Antagonists: Pharmacological Actions

Antimuscarinic drugs block muscarinic receptors in multiple systems, including the gut, eye, smooth muscles, respiratory tract, cardiovascular, and central nervous systems. They produce similar effects with varying selectivity depending on the specific agent and tissue. Here are the key pharmacological actions of antimuscarinics:
Gastrointestinal Effects: Antimuscarinics reduce gut contractions, increase gastric emptying, and slow intestinal transit. They partly inhibit gastric acid secretion...
Cholinergic Receptors: Muscarinic01:25

Cholinergic Receptors: Muscarinic

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...
Cholinergic Antagonists: Chemistry and Structure-Activity Relationship01:29

Cholinergic Antagonists: Chemistry and Structure-Activity Relationship

Cholinergic antagonists bind to cholinergic receptors and limit the effects of acetylcholine and other cholinergic agonists. Based on the specific cholinergic receptor affinity, these antagonists are classified as muscarinic or nicotinic. Anticholinergics interrupt parasympathetic innervations while sympathetic innervations remain uninterrupted. Muscarinic antagonists are also called 'muscarinic antagonists', 'antimuscarinics', or 'parasympatholytics'. Nicotinic antagonists are called...
Direct-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship01:22

Direct-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship

Cholinergic agonists or cholinomimetics mimic the action of acetylcholine to stimulate the parasympathetic nervous system. They are categorized into direct-acting and indirect-acting agents. The direct-acting cholinergic drugs induce the parasympathetic response by directly binding to the muscarinic or nicotine receptors. In comparison, the indirect-acting cholinergic drugs prevent acetylcholine hydrolysis, indirectly contributing to the extended parasympathetic response.
The direct-acting...
Direct-Acting Cholinergic Agonists: Pharmacological Actions00:59

Direct-Acting Cholinergic Agonists: Pharmacological Actions

Direct-acting cholinergic agonists exert their pharmacological actions by mimicking the effects of acetylcholine on postsynaptic muscarinic receptors to generate parasympathetic responses. These agents elicit a range of physiological responses, including cardiovascular effects. For example, activation of muscarinic receptors induces bradycardia, decreased cardiac output, reduced peripheral resistance, and consequent hypotension. In the eye, stimulation of M3 receptors leads to smooth muscle...
Cholinergic Antagonists: Pharmacokinetics01:24

Cholinergic Antagonists: Pharmacokinetics

Cholinergic antagonists—such as antimuscarinics—are available in oral, topical, ocular, parenteral, and inhalational formulations. Most antimuscarinics are oral formulations,  while scopolamine is available as a topical patch, and ipratropium and tiotropium are available as inhalation aerosols or powders. Atropine, tropicamide, and cyclopentolate are topically instilled in the eye. Most antimuscarinics are lipid-soluble and readily absorbed from the gastrointestinal tract and the conjunctiva.

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Subcutaneous Administration of Muscarinic Antagonists and Triple-Immunostaining of the Levator Auris Longus Muscle in Mice
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Published on: September 8, 2011

Muscarinic toxins.

Denis Servent1, Guillaume Blanchet, Gilles Mourier

  • 1CEA, Institute of Biology and Technology, Service d'Ingénierie Moléculaire des Protéines, Gif-sur-Yvette 91191, France. denis.servent@cea.fr

Toxicon : Official Journal of the International Society on Toxinology
|September 13, 2011
PubMed
Summary

Muscarinic toxins from Dendroaspis snakes are key tools for understanding muscarinic receptors. This review covers their isolation, function, and application in studying these important G-Protein Coupled Receptors.

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Area of Science:

  • Biochemistry and Pharmacology
  • Neuroscience
  • Venom Research

Background:

  • Muscarinic receptors are crucial G-Protein Coupled Receptors involved in numerous physiological processes.
  • Dendroaspis snake venom contains unique toxins that selectively target muscarinic receptors.
  • Understanding these toxins aids in elucidating receptor function and developing pharmacological tools.

Purpose of the Study:

  • To review the isolation, identification, and characterization of muscarinic toxins.
  • To explore the mode of action, structure-function relationships, and applications of these toxins.
  • To highlight current challenges and future directions in the pharmacological study of muscarinic toxins.

Main Methods:

  • Literature review of published research on muscarinic toxins.
  • Analysis of data on toxin isolation, purification, and structural determination.
  • Compilation of information on the functional effects and selectivity of toxins on muscarinic receptor subtypes.

Main Results:

  • Muscarinic toxins exhibit high affinity and selectivity for specific muscarinic receptor subtypes.
  • These toxins have been instrumental in dissecting the roles of different muscarinic receptors.
  • Structure-function studies reveal key interactions between toxins and receptor binding sites.

Conclusions:

  • Muscarinic toxins are essential pharmacological probes for muscarinic receptor research.
  • Further studies are needed to fully exploit their potential in understanding receptor subtypes and developing therapeutics.
  • Unresolved issues in pharmacological studies present opportunities for future research.