Introduction: This concise guide on Neurotransmitters MCQs With Answer is designed for B. Pharm students preparing for exams and clinical pharmacy practice. It covers neurotransmitter synthesis, storage, release, receptor pharmacology, reuptake, metabolism, and drug interactions with emphasis on acetylcholine, monoamines, amino acid transmitters and neuropeptides. The questions focus on mechanism of action, key enzymes (e.g., MAO, COMT, ChAT), transporters, receptor subtypes, relevant drugs and toxicology to strengthen mechanistic understanding and application. Use these targeted MCQs to reinforce synaptic physiology and therapeutics crucial for pharmacology and clinical dosing decisions. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which enzyme catalyzes the rate-limiting step in catecholamine synthesis?
- Tyrosine hydroxylase
- Dopamine β-hydroxylase
- Phenylethanolamine N-methyltransferase
- Aromatic L-amino acid decarboxylase
Correct Answer: Tyrosine hydroxylase
Q2. The primary mechanism by which reserpine depletes monoamines is:
- Inhibition of monoamine oxidase
- Blockade of vesicular monoamine transporter (VMAT)
- Inhibition of catechol-O-methyltransferase
- Blocking dopamine receptors
Correct Answer: Blockade of vesicular monoamine transporter (VMAT)
Q3. Which transporter is responsible for reuptake of serotonin into the presynaptic terminal?
- SERT
- DAT
- NET
- VMAT
Correct Answer: SERT
Q4. Acetylcholine is synthesized from choline and acetyl-CoA by which enzyme?
- Acetylcholinesterase
- Choline acetyltransferase (ChAT)
- Butyrylcholinesterase
- Choline oxidase
Correct Answer: Choline acetyltransferase (ChAT)
Q5. Which receptor type is a ligand-gated ion channel mediated by acetylcholine at the neuromuscular junction?
- Muscarinic M2 receptor
- Nicotinic N1 (muscle-type) receptor
- Nicotinic N2 (neuronal) receptor
- Alpha-adrenergic receptor
Correct Answer: Nicotinic N1 (muscle-type) receptor
Q6. Monoamine oxidase inhibitors (MAOIs) primarily increase synaptic levels of monoamines by:
- Blocking reuptake transporters
- Inhibiting presynaptic vesicular release
- Inhibiting intracellular degradation of monoamines
- Enhancing enzymatic synthesis of neurotransmitters
Correct Answer: Inhibiting intracellular degradation of monoamines
Q7. Which neurotransmitter is the major inhibitory transmitter in the adult mammalian CNS?
- Glutamate
- Serotonin
- GABA
- Acetylcholine
Correct Answer: GABA
Q8. The enzyme responsible for degrading acetylcholine in the synaptic cleft is:
- Choline acetyltransferase
- Acetylcholinesterase
- Monoamine oxidase
- Catechol-O-methyltransferase
Correct Answer: Acetylcholinesterase
Q9. Which class of drugs increases synaptic dopamine by blocking the dopamine transporter?
- SSRIs
- DAT inhibitors (e.g., cocaine)
- MAO inhibitors
- COMT inhibitors
Correct Answer: DAT inhibitors (e.g., cocaine)
Q10. L-DOPA is effective in Parkinson’s disease because it:
- Directly stimulates dopamine receptors
- Is a catechol-O-methyltransferase inhibitor
- Crosses the blood-brain barrier and is converted to dopamine
- Blocks dopamine reuptake
Correct Answer: Crosses the blood-brain barrier and is converted to dopamine
Q11. Which receptor subtype is Gs-coupled and typically stimulates adenylate cyclase when activated?
- M2 muscarinic receptor
- D2 dopamine receptor
- B1 beta-adrenergic receptor
- GABAA receptor
Correct Answer: B1 beta-adrenergic receptor
Q12. Which neurotransmitter is primarily excitatory and mediates most fast synaptic transmission in the CNS?
- GABA
- Glutamate
- Glycine
- Serotonin
Correct Answer: Glutamate
Q13. Which enzyme converts dopamine to norepinephrine inside synaptic vesicles?
- Aromatic L-amino acid decarboxylase
- Dopamine β-hydroxylase
- Monoamine oxidase
- Catechol-O-methyltransferase
Correct Answer: Dopamine β-hydroxylase
Q14. Which anticholinesterase drug is commonly used in Alzheimer’s disease to increase cortical acetylcholine?
- Neostigmine
- Rivastigmine
- Edrophonium
- Pyridostigmine
Correct Answer: Rivastigmine
Q15. NMDA receptor activation requires which of the following in addition to glutamate binding?
- GABA co-agonist binding
- Membrane depolarization to relieve Mg2+ block
- ATP binding to receptor
- Phosphorylation by tyrosine kinase
Correct Answer: Membrane depolarization to relieve Mg2+ block
Q16. Which drug mechanism best describes the action of selective serotonin reuptake inhibitors (SSRIs)?
- Inhibit serotonin synthesis
- Block serotonin reuptake via SERT
- Enhance monoamine oxidase activity
- Act as serotonin receptor agonists
Correct Answer: Block serotonin reuptake via SERT
Q17. Glycine acts as an inhibitory neurotransmitter predominantly in which region?
- Hippocampus
- Cerebellum and spinal cord
- Basal ganglia
- Prefrontal cortex
Correct Answer: Cerebellum and spinal cord
Q18. Which co-agonist site on NMDA receptors is required for full receptor activation along with glutamate?
- Dopamine binding site
- GABA binding site
- Glycine (or D-serine) binding site
- Acetylcholine binding site
Correct Answer: Glycine (or D-serine) binding site
Q19. Which drug is a reversible acetylcholinesterase inhibitor used for myasthenia gravis diagnosis?
- Physostigmine
- Neostigmine
- Edrophonium
- Organophosphate (parathion)
Correct Answer: Edrophonium
Q20. Beta-arrestin recruitment following GPCR activation primarily leads to:
- Increased neurotransmitter synthesis
- Receptor desensitization and internalization
- Immediate channel opening
- Inhibition of G-protein receptor kinases
Correct Answer: Receptor desensitization and internalization
Q21. Which compound is the immediate precursor to serotonin (5-HT)?
- Tryptophan
- 5-Hydroxytryptophan (5-HTP)
- Tyrosine
- Melatonin
Correct Answer: 5-Hydroxytryptophan (5-HTP)
Q22. Which enzyme methylates catecholamines and contributes to their inactivation extracellularly?
- Monoamine oxidase (MAO)
- Catechol-O-methyltransferase (COMT)
- Dopamine β-hydroxylase
- Tyrosine hydroxylase
Correct Answer: Catechol-O-methyltransferase (COMT)
Q23. Which receptor subtype mediates bronchodilation when activated by epinephrine?
- Alpha-1 adrenergic receptor
- Beta-2 adrenergic receptor
- M3 muscarinic receptor
- D2 dopamine receptor
Correct Answer: Beta-2 adrenergic receptor
Q24. Benzodiazepines enhance GABAergic transmission primarily by:
- Increasing GABA synthesis
- Directly opening chloride channels independent of GABA
- Increasing frequency of GABAA channel opening
- Inhibiting GABA reuptake transporters
Correct Answer: Increasing frequency of GABAA channel opening
Q25. Which peptide neurotransmitter is involved in pain transmission and acts via GPCRs?
- Substance P
- Dopamine
- Acetylcholine
- Glycine
Correct Answer: Substance P
Q26. The vesicular acetylcholine transporter (VAChT) performs which function?
- Pumps acetylcholine out of the synaptic cleft
- Transports choline into the presynaptic terminal
- Packages acetylcholine into synaptic vesicles
- Degrades acetylcholine in vesicles
Correct Answer: Packages acetylcholine into synaptic vesicles
Q27. Which drug class increases synaptic norepinephrine and serotonin by preventing vesicular storage?
- Reserpine
- SSRIs
- MAOIs
- COMT inhibitors
Correct Answer: Reserpine
Q28. Which of the following is a function of presynaptic autoreceptors?
- Facilitate vesicle docking
- Inhibit further neurotransmitter release through negative feedback
- Increase neurotransmitter synthesis indefinitely
- Transport neurotransmitter into glia
Correct Answer: Inhibit further neurotransmitter release through negative feedback
Q29. Chronic SSRI treatment often leads to which adaptive receptor change?
- Immediate upregulation of postsynaptic serotonin receptors
- Desensitization/downregulation of certain 5-HT receptor subtypes
- Permanent loss of serotonin neurons
- Increased expression of monoamine oxidase
Correct Answer: Desensitization/downregulation of certain 5-HT receptor subtypes
Q30. Which neurotransmitter’s receptors include ionotropic AMPA, NMDA and kainate subtypes?
- GABA
- Glutamate
- Acetylcholine
- Serotonin
Correct Answer: Glutamate
Q31. Which transport process is energy-dependent and uses a proton gradient to load monoamines into vesicles?
- Plasma membrane SERT activity
- VMAT-mediated vesicular uptake
- Reverse DAT transport
- Passive diffusion across vesicle membrane
Correct Answer: VMAT-mediated vesicular uptake
Q32. Which drug is a COMT inhibitor used adjunctively with L-DOPA in Parkinson’s disease?
- Entacapone
- Selegiline
- Carbidopa
- Pramipexole
Correct Answer: Entacapone
Q33. Which receptor subtype mediates fast inhibitory neurotransmission via chloride influx in spinal cord interneurons?
- GABAA receptor
- GABAB receptor
- NMDA receptor
- M1 muscarinic receptor
Correct Answer: GABAA receptor
Q34. Botulinum toxin causes flaccid paralysis by:
- Blocking acetylcholinesterase activity
- Preventing acetylcholine vesicle fusion and release
- Stimulating excessive acetylcholine release
- Antagonizing nicotinic receptors post-synaptically
Correct Answer: Preventing acetylcholine vesicle fusion and release
Q35. Which neurotransmitter’s synthesis requires vitamin B6 (pyridoxal phosphate) as a cofactor for decarboxylation?
- Glutamate to GABA by glutamate decarboxylase
- Tyrosine to L-DOPA by tyrosine hydroxylase
- Acetyl-CoA to acetylcholine
- Serotonin to melatonin
Correct Answer: Glutamate to GABA by glutamate decarboxylase
Q36. Which agent is used to reverse central anticholinesterase toxicity by crossing the blood-brain barrier?
- Neostigmine
- Pyridostigmine
- Atropine
- Pralidoxime (does not efficiently cross BBB)
Correct Answer: Atropine
Q37. Which receptor subtype activation is associated with increased intracellular Ca2+ via Gq signaling?
- M2 muscarinic
- M3 muscarinic
- B1 adrenergic
- D2 dopamine
Correct Answer: M3 muscarinic
Q38. Which neurotransmitter is synthesized from glutamate by glutamic acid decarboxylase?
- GABA
- Glycine
- Glutamine
- Aspartate
Correct Answer: GABA
Q39. Which pharmacological property best explains tolerance to opioid analgesics?
- Upregulation of opioid receptors
- Receptor desensitization and downstream adaptive changes
- Increased opioid synthesis in CNS
- Permanent neuronal loss
Correct Answer: Receptor desensitization and downstream adaptive changes
Q40. Which neurotransmitter’s release is classically associated with the locus coeruleus?
- Serotonin
- Norepinephrine
- Dopamine
- GABA
Correct Answer: Norepinephrine
Q41. Which drug acts as a partial agonist at nicotinic receptors and is used for smoking cessation?
- Bupropion
- Varenicline
- Nicotine patch
- Clonidine
Correct Answer: Varenicline
Q42. Which process describes heterosynaptic modulation?
- Regulation of synaptic strength by the same neuron’s autoreceptors
- Influence of one synapse on a different synapse on the same neuron
- Neurotransmitter release solely by glial cells
- Direct electrical coupling between neurons
Correct Answer: Influence of one synapse on a different synapse on the same neuron
Q43. Which ion is the primary trigger for vesicular neurotransmitter release following action potential arrival?
- Sodium (Na+)
- Potassium (K+)
- Calcium (Ca2+)
- Chloride (Cl-)
Correct Answer: Calcium (Ca2+)
Q44. Which drug is an NMDA receptor antagonist used clinically for anesthesia and also has antidepressant effects at subanesthetic doses?
- Ketamine
- Phencyclidine (PCP)
- Memantine
- Topiramate
Correct Answer: Ketamine
Q45. Which receptor class often mediates slow inhibitory neurotransmission through G-protein coupled K+ channel opening?
- GABAB receptors
- GABAA receptors
- NMDA receptors
- AMPA receptors
Correct Answer: GABAB receptors
Q46. Which biochemical test is used to measure cholinesterase activity in plasma for organophosphate exposure?
- ELISA for acetylcholine
- Plasma butyrylcholinesterase (pseudocholinesterase) assay
- Urinary catecholamine levels
- CSF glutamate assay
Correct Answer: Plasma butyrylcholinesterase (pseudocholinesterase) assay
Q47. Which of the following increases synaptic dopamine by inhibiting MAO-B selectively?
- Entacapone
- Selegiline
- Imipramine
- Fluoxetine
Correct Answer: Selegiline
Q48. Which neurotransmitter system is most directly implicated in the mechanism of many antipsychotic drugs?
- Serotonergic system exclusively
- Dopaminergic system (D2 receptor antagonism)
- GABAergic potentiation only
- Cholinergic enhancement
Correct Answer: Dopaminergic system (D2 receptor antagonism)
Q49. Which drug class would reduce synaptic glutamate excitotoxicity by blocking AMPA receptors?
- AMPA receptor antagonists (e.g., perampanel)
- Benzodiazepines
- SSRIs
- Beta-blockers
Correct Answer: AMPA receptor antagonists (e.g., perampanel)
Q50. In the synaptic cleft, neuropeptides differ from classical transmitters in that they are:
- Stored in small clear vesicles and released rapidly with single action potentials
- Synthesized in the cell body, stored in large dense-core vesicles and require high-frequency stimulation for release
- Recycled via high-affinity transporters directly into vesicles
- Degraded only by acetylcholinesterase
Correct Answer: Synthesized in the cell body, stored in large dense-core vesicles and require high-frequency stimulation for release
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