30 Questions
Which step in cholinergic transmission is the rate-limiting step?
ACh Synthesis
Where are the subtypes of nicotinic receptors found?
Brain, ganglia, adrenal medulla, and neuromuscular junction
What type of receptors are found on the endothelium of many blood vessels?
Muscarinic receptors
What is the general pharmacological effect of muscarinic agonists?
They activate muscarinic receptors
Which ion permeability is increased by the activation of the nicotinic ACh ion channel system?
Na+
What is the role of presynaptic autoreceptors in cholinergic transmission?
They inhibit release of ACh
Which step in cholinergic transmission is driven by exchange with H+?
ACh Storage
Where do the subtypes of muscarinic receptors occur?
CNS, parasympathetic postganglionic endings, endothelium of blood vessels, and sweat glands
What is the general pharmacological effect of muscarinic antagonists?
They reduce the effects of ACh
What controls the nicotinic ACh ion channel system?
Ligand gating
Which type of cholinesterase inhibitor interacts with the anionic site of the phosphorylated enzyme and regenerates the enzyme by displacing the dialkylphosphate residue?
Pralidoxime
What is the primary enzyme responsible for acetylcholine metabolism at cholinergic synapses?
Acetylcholinesterase
Which type of cholinesterase inhibitor is found in plasma, liver, and glia and can also hydrolyze acetylcholine?
Pseudocholinesterase
Which type of cholinesterase inhibitor forms a carbamylated enzyme complex with a lifetime of approximately 20 minutes?
Slowly reversible inhibitors
Which type of cholinesterase inhibitor interacts with Gq and leads to an increase in intracellular Ca2+ stores and smooth muscle contraction?
Muscarinic Receptors M1, 3, 5
Which type of cholinesterase inhibitor regulates ion channels, specifically increasing K+ permeability and resulting in hyperpolarization and a decrease in heart rate?
Muscarinic Receptors M2, 4
Which type of cholinesterase inhibitor is irreversible and interacts only with the esteratic site of the enzyme, leading to permanent inactivation?
Organophosphate inhibitors
Which type of cholinesterase inhibitor is a peripheral and CNS inhibitor of AChE?
Physostigmine
Which type of cholinesterase inhibitor is a peripheral inhibitor of AChE?
Pyridostigmine
Which type of cholinesterase inhibitor is used to treat organophosphate toxicity and interacts with the anionic site of the phosphorylated enzyme?
Pralidoxime
Which autoimmune disorder involves a loss of voltage-sensitive calcium channels on the presynaptic motor nerve terminal?
Lambert-Eaton
Which autoimmune disease affects the postsynaptic neuromuscular junction and is characterized by fatigable weakness of skeletal muscles?
Myasthenia Gravis
Which type of muscles tend to be affected first in Myasthenia Gravis?
Smaller muscles
What are the major pharmacodynamic properties of competitive NMJ blockers?
Highly polar, quaternary compounds with poor oral bioavailability
How are nondepolarizing and depolarizing NMJ blockers different in terms of pharmacokinetics?
Nondepolarizing blockers are rapidly metabolized at the synapse, while depolarizing blockers are not
What drug class is used to reverse the effects of NMJ blockers by increasing the concentration of ACh at NMJ synapses?
AChE inhibitors
What is the mechanism of action of sugammadex in reversing the effects of NMJ blockers?
It sequesters NMJ blockers in the blood
How does genetic variation affect the metabolism of succinylcholine?
It increases the duration of action
What is the duration of paralysis following administration of succinylcholine in individuals with partial deficiency in plasma cholinesterase enzyme activity?
Between 5 minutes and 1 hour
What percentage of the general population carries two pseudocholinesterase gene allele mutations that can produce clinically significant effects from succinylcholine?
Less than 0.1%
Test your knowledge of the major processes in cholinergic transmission, including ACh synthesis, storage, release, and elimination. Learn about the rate-limiting step in ACh synthesis, the concentration of ACh in vesicles, and the role of presynaptic autoreceptors.
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