Neurotransmission: general aspects and steps MCQs With Answer

Introduction: Neurotransmission: general aspects and steps MCQs With Answer is designed for M.Pharm students preparing for advanced pharmacology examinations. This concise question set focuses on the molecular and cellular sequence of events at synapses — from neurotransmitter synthesis and vesicular storage to release, receptor interaction, and termination mechanisms. Emphasis is placed on presynaptic machinery (SNAREs, calcium sensors, vesicular transporters), types of synaptic signaling (ionotropic vs metabotropic, electrical vs chemical), quantal release, and pharmacological modulation (reuptake inhibitors, enzymatic inhibitors, toxins). These MCQs reinforce core concepts, link mechanisms to drug actions, and promote deeper understanding needed for therapeutics and research in neuropharmacology.

Q1. Which type of synapse allows direct cytoplasmic continuity between neurons enabling bidirectional fast transmission?

• Chemical synapse
• Electrical synapse
• Ephaptic transmission
• Volume transmission

Correct Answer: Electrical synapse

Q2. What is the rate-limiting enzyme in the biosynthesis of catecholamines (dopamine, norepinephrine, epinephrine)?

• Dopamine β-hydroxylase
• Tyrosine hydroxylase
• Monoamine oxidase
• Aromatic L-amino acid decarboxylase

Correct Answer: Tyrosine hydroxylase

Q3. Which set of presynaptic proteins constitutes the core SNARE complex essential for synaptic vesicle fusion?

• Synaptobrevin, Syntaxin and SNAP-25
• Clathrin, Dynamin and Synapsin
• Synaptotagmin, Calmodulin and Rab3
• Sodium channel, Potassium channel and Calcium channel

Correct Answer: Synaptobrevin, Syntaxin and SNAP-25

Q4. Which protein acts as the principal Ca2+ sensor that triggers rapid synaptic vesicle exocytosis?

• Calmodulin
• Synaptotagmin
• Synapsin
• Dynamin

Correct Answer: Synaptotagmin

Q5. Which drug irreversibly inhibits the vesicular monoamine transporter (VMAT), depleting monoamine stores?

• Reserpine
• Cocaine
• Fluoxetine
• Amphetamine

Correct Answer: Reserpine

Q6. Which enzyme rapidly hydrolyzes acetylcholine in the synaptic cleft to terminate cholinergic transmission?

• Butyrylcholinesterase
• Acetylcholinesterase
• Choline acetyltransferase
• Monoamine oxidase

Correct Answer: Acetylcholinesterase

Q7. Which membrane transporter is primarily responsible for reuptake of serotonin from the synaptic cleft?

• DAT (Dopamine transporter)
• NET (Norepinephrine transporter)
• SERT (Serotonin transporter)
• VMAT (Vesicular monoamine transporter)

Correct Answer: SERT (Serotonin transporter)

Q8. Botulinum toxin produces flaccid paralysis by which presynaptic mechanism?

• Blocking voltage-gated calcium channels
• Cleaving SNARE proteins and preventing vesicle fusion
• Inhibiting acetylcholinesterase
• Antagonizing post-synaptic nicotinic receptors

Correct Answer: Cleaving SNARE proteins and preventing vesicle fusion

Q9. The term “quantal release” of neurotransmitter refers to which concept?

• Release of neurotransmitter only in proportion to action potential amplitude
• Release occurs in fixed packets corresponding to single synaptic vesicles
• Continuous graded leakage of neurotransmitter across membrane
• Release dependent solely on extracellular sodium concentration

Correct Answer: Release occurs in fixed packets corresponding to single synaptic vesicles

Q10. Which of the following is an example of an ionotropic receptor?

• Muscarinic acetylcholine receptor (mAChR)
• α2-Adrenergic receptor
• NMDA receptor
• D2 dopamine receptor

Correct Answer: NMDA receptor

Q11. Activation of Gq-coupled receptors leads to stimulation of which second messenger pathway?

• Adenylyl cyclase → cAMP
• Guanylyl cyclase → cGMP
• Phospholipase C → IP3 and DAG
• Tyrosine kinase → MAPK only

Correct Answer: Phospholipase C → IP3 and DAG

Q12. Which enzyme located in mitochondria of monoaminergic neurons metabolizes cytosolic dopamine and norepinephrine?

• Catechol-O-methyltransferase (COMT)
• Monoamine oxidase (MAO)
• Acetylcholinesterase (AChE)
• Tyrosine hydroxylase

Correct Answer: Monoamine oxidase (MAO)

Q13. The major contributor to the synaptic delay observed at chemical synapses is which step?

• Axonal conduction of the action potential
• Diffusion of neurotransmitter across the cleft only
• Calcium entry and triggering of vesicle fusion
• Postsynaptic receptor gating kinetics exclusively

Correct Answer: Calcium entry and triggering of vesicle fusion

Q14. Long-term potentiation (LTP) in hippocampal synapses commonly requires which process?

• GABAB receptor activation leading to hyperpolarization
• NMDA receptor-mediated Ca2+ influx and insertion of AMPA receptors
• Immediate proteolysis of presynaptic SNARE proteins
• Inhibition of protein kinases and removal of AMPA receptors

Correct Answer: NMDA receptor-mediated Ca2+ influx and insertion of AMPA receptors

Q15. Which drug increases cholinergic signaling in Alzheimer’s disease by inhibiting acetylcholinesterase?

• Botulinum toxin
• Donepezil
• Haloperidol
• Reserpine

Correct Answer: Donepezil

Q16. Which neurotransmitter is the principal inhibitory amino acid in the mammalian central nervous system?

• Glutamate
• GABA (gamma-aminobutyric acid)
• Acetylcholine
• Dopamine

Correct Answer: GABA (gamma-aminobutyric acid)

Q17. During synaptic vesicle endocytosis, which GTPase mediates scission of the budding vesicle from the plasma membrane?

• Clathrin
• Dynamin
• Synapsin
• Synaptotagmin

Correct Answer: Dynamin

Q18. Which vesicular transporter is responsible for packaging glutamate into synaptic vesicles?

• VMAT (vesicular monoamine transporter)
• VAChT (vesicular acetylcholine transporter)
• VGLUT (vesicular glutamate transporter)
• SERT (serotonin transporter)

Correct Answer: VGLUT (vesicular glutamate transporter)

Q19. Presynaptic autoreceptors typically mediate which effect on neurotransmitter release?

• Positive feedback to increase synthesis and release
• Negative feedback to inhibit further release
• Permanent blockade of release machinery
• Activation of postsynaptic gene transcription only

Correct Answer: Negative feedback to inhibit further release

Q20. What best describes ‘volume transmission’ in the nervous system?

• Highly localized synaptic cleft-limited signaling
• Electrical coupling through gap junctions
• Diffuse extracellular signaling affecting multiple cells at a distance
• Direct axon-to-axon inhibitory synapses only

Correct Answer: Diffuse extracellular signaling affecting multiple cells at a distance

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