80 Questions
Which enzyme hydrolyzes acetylcholine?
AChE
Where are cholinergic terminals found?
All of the above
Which receptor subtype is responsible for bronchoconstriction?
M3
What is the effect of M2 receptors on the cardiovascular system?
Decrease heart rate
Which receptor subtype is responsible for vasodilation?
M3
Which type of receptors do cholinergic neurons have?
Both mAChRs and nAChRs
What are the subunits of mAChRs?
a, B, y
What are the subunits of nAChRs?
a, B, y, E
Which muscarinic agonist is used for the treatment of glaucoma and ocular surgery?
Miostat (carbachol chloride)
Which muscarinic agonist is used for bronchial challenge test?
Provocholine (methacholine chloride)
Which receptor does Methacholine primarily act on?
Muscarinic receptors
What is the main therapeutic application of Methacholine?
Treatment of asthma and COPD
Which of the following is a contraindication for Methacholine use?
Coronary insufficiency
What is the effect of Methacholine on the cardiovascular system?
It causes bradycardia and hypotension
What is the primary diagnostic use of Methacholine?
Diagnosis of asthma and COPD
Which isomer of ACh hydrolyzes slower than acetylcholine by AChE?
S-(+)-P-ACh
What is the SAR of Urecholine (bethanechol chloride)?
It has a metilo group and a carbamate group
Which amine in pilocarpene reacts to form HCl salt?
Tertiary amine
What metabolic/physicochemical vulnerabilities do you expect pilocarpene to have?
Epimerization
What kind of relationship do the highlighted functional groups in Arecoline and Xanomeline have?
Bioisosteric (nonclassical)
Which enzyme is responsible for breaking down Acetylcholine (ACh)?
Acetylcholinesterase (AChE)
What is the role of autoreceptors in the cholinergic system?
To regulate the release of ACh
Which neurotransmitter is released by the sympathetic system to decrease the release of ACh?
Norepinephrine (NE)
What is the role of M4 receptors in the cholinergic system?
To regulate the release of ACh
What happens when there is an excess of ACh in the synapse?
ACh escapes the synapse
Which of the following is a reversible acetylcholinesterase inhibitor that forms a more stable inactive site of AChE or has a higher affinity for the active site than ACh but does not react as a substrate?
Antilirium
Which of the following drugs is a synthetic compound that resembles physostigmine and is used for prophylaxis of abdominal distension and urinary retention, myasthenia gravis, and reversal of neuromuscular blockade?
Prostigmin
Which of the following drugs is a synthetic compound closely related to neostigmine, has a longer duration of action, and a lower incidence of side effects?
Mestinon
Which of the following drugs is a centrally-acting reversible and non-competitive inhibitor with a long elimination half-life of 70+ hours?
Aricept
Which of the following drugs is a pseudo-irreversible inhibitor that inhibits plasma choline-E and crosses the blood-brain barrier?
Exelon
What is the primary diagnostic use of Methacholine?
Bronchial challenge test
Which muscarinic agonist is used for the treatment of glaucoma and ocular surgery?
Pilocarpine
Which receptor does Methacholine primarily act on?
M3
Which type of receptors are coupled to G-proteins and produce effectors in cholinergic neurons?
mAChRs
What is the main therapeutic application of Miostat (carbachol chloride)?
Treatment of glaucoma and ocular surgery
Which muscarinic agonist is preferentially selective for mAChRs over nAChRs?
Xanomeline
What is the main diagnostic use of Provocholine (methacholine chloride)?
Bronchial challenge test
What makes carbachol chloride more stable to hydrolysis compared to ACh?
Carbamate ester
Which of the following drugs is a reversible acetylcholinesterase inhibitor that forms a more stable inactive site of AChE or has a higher affinity for the active site than ACh but does not react as a substrate?
Antilirium
What is the elimination half-life of Cognex (tacrine HCl)?
1.5-4 hrs
Which of the following drugs is a centrally-acting reversible and non-competitive inhibitor with a long elimination half-life of 70+ hours?
Aricept
Which of the following drugs crosses the blood-brain barrier and is not associated with hepatotoxicity?
Exelon
Which of the following is an irreversible acetylcholinesterase inhibitor that generates an extremely stable phosphorylated-Serine residue in AChE?
Phospholine Iodide
Which of the following statements about acetylcholine (ACh) is correct?
ACh is hydrolyzed by Acetylcholinesterase (AChE)
Which receptor subtype is responsible for bronchoconstriction?
M3
Which of the following is a therapeutic application of Bethanechol?
Retaining urine in non-obstructive cases
Which of the following statements about Muscarinic receptors is correct?
M2 and M4 receptors are acutely inhibited by Gi proteins
Which of the following drugs is used for the treatment of open-angle glaucoma and xerostomia (dry-mouth)?
Salogen or Isopto Carpine (pilocarpene HCl)
Which of the following drugs is a partial direct M1 agonist in the CNS and an M3 agonist in the epithelial tissue of lacrimal and salivary glands?
Evoxac (Cevimeline Hydrochloride)
What is the main therapeutic application of Acetylcholinesterase (AChE) inhibitors?
All of the above
What is the catalytic triad involved in the esteratic site of AChE?
Glutamate, histidine, serine
If the AChE enzyme is acylated by an agent with a more stable functional group, what happens?
It becomes inactive for a longer period of time
What is the main diagnostic use of Methacholine?
To diagnose asthma and COPD
Which of the following is true about Methacholine's effect on the cardiovascular system?
Methacholine causes bradycardia and hypotension
Which of the following is a therapeutic application of Methacholine?
Treatment of asthma and COPD
Which receptor subtype is responsible for vasodilation?
M3
What is the effect of M2 receptors on the cardiovascular system?
Negative chronotropic effect
What is the main therapeutic application of Acetylcholinesterase (AChE) inhibitors?
Treatment of myasthenia gravis
True or false: Acetylcholine is a neurotransmitter for both the sympathetic and parasympathetic nervous systems.
False
True or false: Muscarinic cholinergic agents interact with nicotinic receptors.
False
True or false: Muscarinic acetylcholinergic receptors are metabotropic receptors.
True
True or false: Pirenzepine acts as a muscarinic agonist without blocking the effect of muscarinic antagonists?
False
True or false: Anticholinergic agents are used to treat glaucoma?
False
True or false: Odd numbered mAChRs are coupled to Gq proteins?
True
True or false: Nicotinic receptors are found in the neuromuscular junctions, adrenal medulla, and autonomic ganglia?
True
True or false: ACh cannot be administered orally due to its physicochemical properties and inability to penetrate the Blood-Brain Barrier?
True
True or false: Acetylcholine (ACh) is a poor therapeutic agent due to its promiscuity towards both muscarinic (mAChRs) and nicotinic (nAChRs) receptors?
True
Which of the following drugs is a non-specific muscarinic agonist that acts as an agonist to both mAChRs and nAChRs?
Miostat (carbachol chloride)
True or false: Muscarinic agonists with a longer chain length between the ethylene group and the N atom have increased activity?
False
True or false: Muscarinic agonists with quaternary ammonium groups substituted with heteroatoms like S, Se, Ar, Ph are more active than those with nitrogen?
False
Which of the following drugs is a specific muscarinic agonist that has a preference to act as an agonist to mAChRs over nAChRs?
Pilocarpine
Which of the following drugs is a synthetic compound closely related to neostigmine, has a longer duration of action, and a lower incidence of side effects?
Neostigmine
Which of the following drugs is used for the treatment of post-surgical and post-partum urinary retention?
Urecholine (bethanechol chloride)
Which muscarinic agonist is used to treat open-angle glaucoma and xerostomia (dry-mouth)?
Salogen or Isopto Carpine (pilocarpene HCl)
Which muscarinic agonist is a partial direct M1 agonist in the CNS and an M3 agonist in epithelial tissue of lacrimal and salivary glands?
Evoxac (Cevimeline Hydrochloride)
Which muscarinic agonist has affinity for M3 subtype and is used as an ocular and oral treatment for open-angle glaucoma and xerostomia (dry-mouth)?
Salogen or Isopto Carpine (pilocarpene HCl)
Which of the following drugs is an irreversible acetylcholinesterase inhibitor that generates an extremely stable phosphorylated-Serine residue in AChE?
Antilirium (Physostigmine)
Which of the following drugs is a synthetic compound closely related to neostigmine, has a longer duration of action, and a lower incidence of side effects?
Mestinon (Pyridostigmine)
Which of the following drugs is a reversible acetylcholinesterase inhibitor that forms a more stable inactive site of AChE or has a higher affinity for the active site than ACh but does not react as a substrate?
Antilirium (Physostigmine)
Which of the following drugs is an alkaloid isolated from the calabar bean (Physostigma venenosum), carbamylates AChE at a slow rate but has high affinity, and can diffuse across the blood-brain barrier?
Antilirium (Physostigmine)
Study Notes
Cholinergic System
- Acetylcholine (ACh) is broken down by the enzyme acetylcholinesterase (AChE)
- Cholinergic terminals are found in the neuromuscular junction, autonomic ganglia, and central nervous system
Receptors and Agonists
- Muscarinic receptors are responsible for various physiological responses, including bronchoconstriction and vasodilation
- M2 receptors are responsible for bronchoconstriction
- M3 receptors are responsible for vasodilation
- Methacholine is a muscarinic agonist used for bronchial challenge tests and has a primary diagnostic use for bronchial hyperreactivity
- Methacholine primarily acts on M3 receptors
- Pilocarpine is a muscarinic agonist used to treat glaucoma and ocular surgery
Enzymes and Inhibitors
- Acetylcholinesterase (AChE) is the enzyme responsible for breaking down acetylcholine (ACh)
- Reversible acetylcholinesterase inhibitors, such as Neostigmine, form a more stable inactive site of AChE or have a higher affinity for the active site than ACh
- Physostigmine is a reversible acetylcholinesterase inhibitor that crosses the blood-brain barrier
- Tacrine is a centrally-acting reversible and non-competitive inhibitor with a long elimination half-life of 70+ hours
Autoreceptors and Neurotransmitters
- Autoreceptors in the cholinergic system decrease the release of ACh
- The sympathetic system releases norepinephrine to decrease the release of ACh
- M4 receptors play a role in the cholinergic system
Other
- Excess ACh in the synapse leads to increased transmission
- Arecoline and Xanomeline have a synergistic relationship between their functional groups
Test your knowledge on Agonistas Muscarínicos Directos and their role in the cholinergic system. This multiple-choice exam will assess your understanding of neurotransmission, the transformation of choline into acetylcholine, and the release of acetylcholine from vesicles. Put your knowledge to the test and see how well you know these structures.
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