5 Questions
Methacholine is primarily used for the treatment of urinary bladder disorders
False
Methacholine is given by inhalation for the diagnosis of bronchial hyper-reactivity
True
Muscarinic receptor agonists can be classified into two classes: synthetic choline esters and cholinomimetic alkaloids
True
Bethanechol is contraindicated for the treatment of urine retention in the presence of organic obstruction
True
M1 and M4 receptor stimulation is of therapeutic interest for Alzheimer’s dementia and schizophrenia
True
Study Notes
Cholinergic Transmission in the Autonomic Nervous System
- Acetylcholine (ACh) mediates neurotransmission at two distinct sites: ganglia and parasympathetic nerve endings.
- In ganglia, ACh acts on neuronal nicotinic receptors (N).
- In parasympathetic nerve endings, ACh acts on muscarinic receptors (M).
Nicotinic ACh Receptors
- Nicotinic ACh receptors are ligand-gated cation channels, permeable to sodium and calcium ions.
- Activation of these receptors causes rapid depolarization.
- There are two categories of nicotinic ACh receptors:
- Neuronal nicotinic receptors (N)
- Muscular nicotinic receptors (N)
Muscarinic ACh Receptors
- Five distinct subtypes of muscarinic ACh receptors exist.
- Different subtypes exist in the same organ.
- M3 is predominantly present in peripheral tissues.
- Muscarinic receptors may be present in locations without parasympathetic innervation, such as blood vessels.
- All muscarinic receptors are G-protein coupled.
- There are no highly selective agonists or antagonists for muscarinic receptors.
- Note: In contrast to muscarinic receptors, different subtypes of nicotinic receptors have selective agonists and antagonists.
Test your knowledge of cholinergic transmission in the autonomic nervous system and the role of acetylcholine in neurotransmission at different sites. This quiz covers topics such as cholinergic agonists, nicotinic and muscarinic receptors, and the classification of neuronal nicotinic receptors.
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