Cholinergic receptors – Nicotinic MCQs With Answer

Cholinergic receptors – Nicotinic MCQs With Answer

Understanding cholinergic nicotinic receptors is essential for B.Pharm students studying pharmacology, physiology, and therapeutics. These ligand-gated ion channels mediate fast synaptic transmission at the neuromuscular junction and autonomic ganglia, and include neuronal subtypes (α4β2, α7) with diverse clinical roles. Key concepts include subunit composition, ion selectivity, agonists (nicotine, succinylcholine), antagonists (curare, hexamethonium, mecamylamine), desensitization, depolarizing vs non-depolarizing blockade, and interactions with acetylcholinesterase inhibitors. Mastery helps predict drug effects, adverse reactions, and therapeutic applications like smoking cessation. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which ionic permeability change primarily occurs when a nicotinic acetylcholine receptor (nAChR) opens?

• Increase in Na+ and K+ conductance with net depolarizing current
• Selective increase in Ca2+ conductance only
• Decrease in Cl- conductance causing hyperpolarization
• Activation of G-protein leading to second messenger cascade

Correct Answer: Increase in Na+ and K+ conductance with net depolarizing current

Q2. Which subunit composition is typical of the adult muscle-type nAChR at the neuromuscular junction?

• α1, α1, β1, δ, ε
• α4, β2, β2
• α7 homopentamer
• α3, β4, γ

Correct Answer: α1, α1, β1, δ, ε

Q3. Which drug acts as a competitive (non-depolarizing) antagonist at skeletal muscle nAChRs?

• Pancuronium
• Succinylcholine
• Nicotine
• AChE inhibitor physostigmine

Correct Answer: Pancuronium

Q4. Succinylcholine produces neuromuscular blockade by which primary mechanism?

• Persistent depolarization of the motor end plate (depolarizing block)
• Competitive inhibition of ACh binding without channel opening
• Inhibition of acetylcholinesterase increasing ACh concentration
• Irreversible alkylation of the receptor site

Correct Answer: Persistent depolarization of the motor end plate (depolarizing block)

Q5. Which neuronal nAChR subtype is a homomeric receptor notable for high Ca2+ permeability and expression in the brain?

• α7
• α4β2
• α1β1δε
• β2β2 homomer

Correct Answer: α7

Q6. Mecamylamine is best described pharmacologically as:

• Nonselective neuronal nicotinic receptor antagonist (ganglionic blocker)
• Muscle-type nAChR agonist used for paralysis
• Acetylcholinesterase inhibitor used in myasthenia gravis
• Selective α7 agonist used for cognitive enhancement

Correct Answer: Nonselective neuronal nicotinic receptor antagonist (ganglionic blocker)

Q7. Which statement about desensitization of nAChRs is correct?

• Prolonged agonist exposure leads to a non-conducting desensitized state despite agonist presence
• Desensitization results from rapid receptor internalization only
• Desensitization converts receptors into metabotropic receptors
• Desensitization increases single-channel open probability permanently

Correct Answer: Prolonged agonist exposure leads to a non-conducting desensitized state despite agonist presence

Q8. Which agent would reverse a non-depolarizing neuromuscular blockade clinically?

• Neostigmine (acetylcholinesterase inhibitor)
• Succinylcholine bolus
• Hexamethonium
• Bungarotoxin

Correct Answer: Neostigmine (acetylcholinesterase inhibitor)

Q9. Which of the following is a partial agonist at α4β2 nicotinic receptors used for smoking cessation?

• Varenicline
• Hexamethonium
• Pancuronium
• Bungarotoxin

Correct Answer: Varenicline

Q10. Hexamethonium primarily blocks which physiological site?

• Autonomic ganglionic nAChRs
• Neuromuscular junction muscle nAChRs
• Central α7 receptors selectively
• Postsynaptic muscarinic receptors

Correct Answer: Autonomic ganglionic nAChRs

Q11. Which neurotoxin binds irreversibly to the neuromuscular nAChR α-subunit and blocks ACh binding?

• α-Bungarotoxin
• Mecamylamine
• Physostigmine
• Nicotine

Correct Answer: α-Bungarotoxin

Q12. Which feature distinguishes depolarizing blockade (succinylcholine) from non-depolarizing blockade?

• Phase I block shows fasciculations followed by flaccid paralysis
• Phase I block is rapidly reversed by neostigmine
• Depolarizing blockers are competitive antagonists
• Non-depolarizing blockers cause persistent depolarization

Correct Answer: Phase I block shows fasciculations followed by flaccid paralysis

Q13. Which measurement best reflects the potency (EC50) of a nicotinic agonist in vitro?

• Concentration producing 50% of maximal receptor-mediated current
• Concentration required to inhibit 50% of acetylcholinesterase
• Plasma concentration that causes 50% paralysis in vivo
• IC50 for blocking muscarinic receptors

Correct Answer: Concentration producing 50% of maximal receptor-mediated current

Q14. Which clinical condition involves antibodies against postsynaptic muscle nAChRs leading to weakness?

• Myasthenia gravis
• Lambert-Eaton myasthenic syndrome
• Amyotrophic lateral sclerosis
• Guillain-Barré syndrome

Correct Answer: Myasthenia gravis

Q15. Which effect is expected when a ganglionic blocker like hexamethonium is administered?

• Orthostatic hypotension due to loss of sympathetic tone
• Bradycardia due to increased vagal activity
• Bronchoconstriction from enhanced parasympathetic tone
• Miosis due to increased pupillary constriction

Correct Answer: Orthostatic hypotension due to loss of sympathetic tone

Q16. Which statement about α4β2 receptors is TRUE?

• They are high-affinity neuronal receptors implicated in nicotine addiction
• They form the adult muscle endplate receptor
• They are exclusively homomeric α7 receptors
• They have no role in cognitive processes

Correct Answer: They are high-affinity neuronal receptors implicated in nicotine addiction

Q17. Which agent would most likely potentiate succinylcholine-induced hyperkalemia?

• Burn injury (extensive muscle denervation)
• Administration of a non-depolarizing blocker
• Use of central α7 agonist
• Concurrent acetylcholinesterase inhibition reversing succinylcholine

Correct Answer: Burn injury (extensive muscle denervation)

Q18. Single-channel recordings of neuronal nAChRs show which property?

• Short open times and variable conductance depending on subtype
• G-protein mediated current with long latency
• Only inward chloride currents
• Irreversible opening once activated

Correct Answer: Short open times and variable conductance depending on subtype

Q19. Which drug is used clinically to reverse organophosphate-induced muscarinic toxicity but does not reverse nicotinic paralysis at NMJ?

• Atropine
• Pralidoxime (2-PAM)
• Neostigmine
• Succinylcholine

Correct Answer: Atropine

Q20. Which genetic change in muscle-type nAChR subunits can explain congenital myasthenic syndromes?

• Mutations altering channel gating or expression leading to impaired synaptic transmission
• Mutations increasing acetylcholinesterase activity in plasma
• Mutations causing overproduction of acetylcholine
• Mutations converting nAChR into muscarinic receptors

Correct Answer: Mutations altering channel gating or expression leading to impaired synaptic transmission

Q21. Which best describes use-dependence in the context of nicotinic receptor blockade?

• Blockers preferentially inhibit receptors that are frequently activated or open
• Block increases with receptor inactivity
• Use-dependence refers to increased receptor synthesis with drug use
• It indicates blockers that are only effective after protein synthesis

Correct Answer: Blockers preferentially inhibit receptors that are frequently activated or open

Q22. Which clinical feature suggests a ganglionic blockade rather than isolated muscarinic blockade?

• Both orthostatic hypotension and impaired pupillary light reflex
• Excessive salivation alone
• Bronchodilation only
• Profuse sweating with normal blood pressure

Correct Answer: Both orthostatic hypotension and impaired pupillary light reflex

Q23. Which pharmacological property allows nicotine to cross the blood-brain barrier efficiently?

• Small, lipophilic tertiary amine structure enabling CNS penetration
• Large polar quaternary ammonium structure
• Irreversible protein binding in plasma
• Active uptake via nicotinic transporters

Correct Answer: Small, lipophilic tertiary amine structure enabling CNS penetration

Q24. Which effect is commonly seen with systemic nicotine administration?

• Initial ganglionic stimulation followed by depression with high doses
• Pure selective muscarinic activation with no sympathetic effects
• Complete blockade of neuromuscular transmission at low doses
• Selective blockade of α7 receptors only

Correct Answer: Initial ganglionic stimulation followed by depression with high doses

Q25. Which experimental technique is most useful to determine nAChR subunit composition?

• Immunoprecipitation with subunit-specific antibodies and mass spectrometry
• Measuring blood acetylcholine concentration
• Standard light microscopy of the synapse
• Recording muscle contraction force without molecular tools

Correct Answer: Immunoprecipitation with subunit-specific antibodies and mass spectrometry

Q26. Which is the primary clinical risk of using non-depolarizing neuromuscular blockers without appropriate ventilation?

• Respiratory muscle paralysis and hypoventilation
• Excessive bronchial secretions causing cough
• Hypertension due to sympathetic overactivity
• Seizures from central α7 activation

Correct Answer: Respiratory muscle paralysis and hypoventilation

Q27. Which statement about acetylcholinesterase inhibitors and succinylcholine is correct?

• AChE inhibitors prolong action of succinylcholine by inhibiting its hydrolysis at synapse minimally because succinylcholine is mainly hydrolyzed by plasma butyrylcholinesterase
• AChE inhibitors completely prevent succinylcholine action
• AChE inhibitors convert succinylcholine into a non-depolarizing blocker
• AChE inhibitors have no interaction with succinylcholine metabolism

Correct Answer: AChE inhibitors prolong action of succinylcholine by inhibiting its hydrolysis at synapse minimally because succinylcholine is mainly hydrolyzed by plasma butyrylcholinesterase

Q28. Which property is characteristic of α-bungarotoxin binding to nAChRs?

• Irreversible high-affinity binding to muscle and some neuronal α7 receptors
• Reversible low-affinity blockade of ganglionic receptors
• Allosteric potentiation of receptor currents
• Selective agonism at α4β2 receptors

Correct Answer: Irreversible high-affinity binding to muscle and some neuronal α7 receptors

Q29. Which clinical use exploits blockade of neuronal nAChRs to reduce blood pressure historically?

• Antihypertensive effect of ganglionic blockers like hexamethonium (historical)
• Neuromuscular blockade to produce muscle relaxation in hypertension
• α7 agonists used to dilate blood vessels
• Varenicline used to treat hypertension

Correct Answer: Antihypertensive effect of ganglionic blockers like hexamethonium (historical)

Q30. Which pharmacokinetic feature affects the duration of action of a neuromuscular blocker?

• Extent of hepatic metabolism and renal elimination
• Ability to cross the blood-brain barrier
• Binding to muscarinic receptors in heart
• Activation of intracellular second messengers

Correct Answer: Extent of hepatic metabolism and renal elimination

Q31. Which receptor alteration contributes to chronic nicotine tolerance and dependence?

• Upregulation and altered function of certain neuronal nAChR subtypes
• Complete loss of muscle nAChRs at the NMJ
• Permanent blockade of acetylcholinesterase
• Conversion of nicotinic receptors into muscarinic receptors

Correct Answer: Upregulation and altered function of certain neuronal nAChR subtypes

Q32. Which ion contributes to the excitatory postsynaptic potential mediated by nAChRs most directly?

• Sodium influx leading to membrane depolarization
• Chloride influx causing hyperpolarization
• Potassium efflux causing hyperpolarization
• Magnesium blockade of the channel pore

Correct Answer: Sodium influx leading to membrane depolarization

Q33. Which experimental blockade pattern indicates a non-competitive antagonist at nAChRs?

• Reduced maximal response (Emax) without parallel rightward shift of the dose–response curve
• Parallel rightward shift with preserved Emax
• No change in dose–response curve
• Increased receptor expression on chronic exposure

Correct Answer: Reduced maximal response (Emax) without parallel rightward shift of the dose–response curve

Q34. Which pharmacological agent preferentially blocks neuronal α7 homomeric receptors in research studies?

• Methyllycaconitine (MLA)
• Pancuronium
• Hexamethonium
• Atropine

Correct Answer: Methyllycaconitine (MLA)

Q35. In myasthenia gravis, which diagnostic test uses nAChR physiology to confirm the disease?

• Repetitive nerve stimulation showing decremental response
• Electroencephalogram showing seizure activity
• Single-fiber EMG showing increased jitter in postsynaptic blockade
• Both 1 and 3

Correct Answer: Both 1 and 3

Q36. Which adverse effect is most associated with mecamylamine therapy historically?

• Postural hypotension and constipation due to ganglionic blockade
• Bronchospasm due to muscarinic stimulation
• Central respiratory depression via α7 activation
• Inhibition of acetylcholinesterase causing cholinergic crisis

Correct Answer: Postural hypotension and constipation due to ganglionic blockade

Q37. Which describes the fetal vs adult muscle nAChR difference?

• Fetal receptors contain γ subunit; adult contain ε subunit, affecting channel kinetics
• Fetal receptors are α7 homomers while adults are heteromers
• Adult receptors are exclusively neuronal α4β2 subtypes
• There is no subunit composition change between fetal and adult forms

Correct Answer: Fetal receptors contain γ subunit; adult contain ε subunit, affecting channel kinetics

Q38. Which statement about single-channel conductance of nAChRs is correct?

• Conductance varies by subtype; muscle nAChRs typically have higher conductance than some neuronal subtypes
• All nAChRs have identical conductance values
• nAChR conductance is irrelevant to synaptic current amplitude
• Only muscarinic receptors exhibit single-channel conductance

Correct Answer: Conductance varies by subtype; muscle nAChRs typically have higher conductance than some neuronal subtypes

Q39. Which therapeutic strategy targets neuronal nAChRs to improve cognitive function in research?

• α7 agonists and positive allosteric modulators
• Non-depolarizing neuromuscular blockers
• Ganglionic blockers like hexamethonium
• Acetylcholinesterase inhibitors only for peripheral synapses

Correct Answer: α7 agonists and positive allosteric modulators

Q40. Which laboratory finding would indicate a presynaptic facilitation defect rather than a postsynaptic nAChR problem?

• Incremental response on high-frequency stimulation (seen in Lambert-Eaton syndrome)
• Decremental response on repetitive stimulation at low frequency (myasthenia gravis)
• Elevated serum creatine kinase levels only
• Isolated loss of AChE activity in synaptic cleft

Correct Answer: Incremental response on high-frequency stimulation (seen in Lambert-Eaton syndrome)

Q41. Which of the following describes competitive antagonism at nAChRs?

• Rightward parallel shift of agonist dose–response curve with no change in maximal response
• Decrease in maximal response without change in potency
• Irreversible blockade increasing spontaneously with time
• Agonist-induced receptor internalization

Correct Answer: Rightward parallel shift of agonist dose–response curve with no change in maximal response

Q42. Which clinical sign would suggest excessive nicotinic receptor stimulation systemically?

• Muscle fasciculations followed by weakness and respiratory compromise
• Dilated pupils and dry skin only
• Isolated bradycardia without skeletal muscle symptoms
• Increased gastrointestinal motility without muscle signs

Correct Answer: Muscle fasciculations followed by weakness and respiratory compromise

Q43. Which statement about varenicline’s mechanism is correct?

• Partial agonist at α4β2 receptors, reducing withdrawal and blocking nicotine effects
• Full agonist at muscle-type nAChRs used as muscle relaxant
• Nonselective ganglionic blocker used as an antihypertensive
• Irreversible antagonist at α7 receptors

Correct Answer: Partial agonist at α4β2 receptors, reducing withdrawal and blocking nicotine effects

Q44. Which biochemical assay helps quantify functional nAChR activity in cultured cells?

• Patch-clamp electrophysiology measuring macroscopic currents
• ELISA for acetylcholinesterase concentration
• Western blot for muscarinic receptor protein
• Assay for plasma butyrylcholinesterase only

Correct Answer: Patch-clamp electrophysiology measuring macroscopic currents

Q45. Which adverse effect is most commonly associated with succinylcholine in ICU/trauma patients?

• Hyperkalemia due to upregulated extrajunctional nAChRs
• Severe hypertension unrelated to neuromuscular effects
• Chronic myopathy from long-term use
• Increased acetylcholinesterase activity causing resistance

Correct Answer: Hyperkalemia due to upregulated extrajunctional nAChRs

Q46. Which therapeutic agent can be used to treat nicotine dependence by acting as a dopamine reuptake inhibitor and weak nAChR antagonist?

• Bupropion
• Hexamethonium
• Neostigmine
• Pancuronium

Correct Answer: Bupropion

Q47. Which factor increases sensitivity of the neuromuscular junction to non-depolarizing blockers?

• Hypothermia and certain antibiotics like aminoglycosides
• Hypercalcemia and increased plasma pH
• Chronic smoking increasing α4β2 expression
• Use of acetylcholinesterase inhibitors prior to blockade

Correct Answer: Hypothermia and certain antibiotics like aminoglycosides

Q48. Which experimental observation supports the conclusion that a nicotinic ligand is an allosteric modulator rather than an orthosteric agonist?

• It enhances responses to acetylcholine without competing for the same binding site
• It produces identical responses to maximal acetylcholine alone
• It is inhibited completely by high concentrations of acetylcholine
• It irreversibly binds to the orthosteric site preventing ACh binding

Correct Answer: It enhances responses to acetylcholine without competing for the same binding site

Q49. Which clinical precaution is important when administering succinylcholine to a patient with a history of severe burns?

• Avoid succinylcholine because of risk of life-threatening hyperkalemia
• Administer a higher dose to overcome resistance
• Combine with ganglionic blocker to prevent hyperkalemia
• No special precautions are required

Correct Answer: Avoid succinylcholine because of risk of life-threatening hyperkalemia

Q50. Which research finding would suggest that a drug is a selective antagonist of peripheral muscle nAChRs but spares neuronal subtypes?

• Block of neuromuscular transmission with preserved central cognitive function in animal models
• Reduction in nicotine-induced locomotor activity in mice without neuromuscular effects
• Inhibition of α7-mediated currents in hippocampal slices only
• Systemic ganglionic blockade causing orthostatic hypotension

Correct Answer: Block of neuromuscular transmission with preserved central cognitive function in animal models

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com