Understanding classification of neurotransmitters is essential for B. Pharm students studying neuropharmacology and therapeutics. This concise introduction explains chemical and functional classifications — amino acid neurotransmitters, monoamines (catecholamines and indolamines), cholinergic systems, neuropeptides, purines, gases and endocannabinoids — and covers synthesis, vesicular storage, receptors (ionotropic vs metabotropic), transporters, metabolism (MAO, COMT, AChE) and clinical drug targets (SSRIs, MAO inhibitors, cholinesterase inhibitors). Emphasis on excitatory/inhibitory roles, mechanisms of termination, and disease relevance will deepen conceptual understanding for exams and pharmacy practice. Focus on classification frameworks, neurotransmitter examples, pharmacokinetics, and clinical correlations. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which set best describes the classical criteria for a substance to be considered a neurotransmitter?
- Synthesized in neuron, stored in vesicles, released on stimulation, has specific postsynaptic receptors and a mechanism for termination
- Only synthesized in glial cells and acts diffusely
- Present in blood and acts on distant organs through circulation
- Only produced outside the nervous system and transported into synapses
Correct Answer: Synthesized in neuron, stored in vesicles, released on stimulation, has specific postsynaptic receptors and a mechanism for termination
Q2. Acetylcholine is classified primarily as which type of neurotransmitter?
- Monoamine
- Amino acid
- Cholinergic small-molecule neurotransmitter derived from choline
- Neuropeptide
Correct Answer: Cholinergic small-molecule neurotransmitter derived from choline
Q3. What is the rate-limiting enzyme in catecholamine (dopamine, norepinephrine) biosynthesis?
- Aromatic L-amino acid decarboxylase (AAAD)
- Tyrosine hydroxylase
- Monoamine oxidase (MAO)
- Choline acetyltransferase (ChAT)
Correct Answer: Tyrosine hydroxylase
Q4. Monoamine oxidase (MAO) primarily performs which function in neurotransmitter metabolism?
- Vesicular uptake of monoamines
- Oxidative deamination of monoamines in mitochondria
- Conversion of acetylcholine to choline
- Synthesis of catecholamines from tyrosine
Correct Answer: Oxidative deamination of monoamines in mitochondria
Q5. Which GABA receptor subtype is metabotropic (G-protein coupled)?
- GABA-A
- GABA-C
- GABA-B
- GABA-D
Correct Answer: GABA-B
Q6. Which neurotransmitter is the principal excitatory amino acid in the central nervous system?
- GABA
- Glycine
- Glutamate
- Dopamine
Correct Answer: Glutamate
Q7. Which class of neurotransmitters is typically synthesized in the neuronal cell body and packaged in large dense-core vesicles?
- Small-molecule neurotransmitters
- Neuropeptides
- Monoamines
- Purines (ATP)
Correct Answer: Neuropeptides
Q8. Which transporter is responsible for loading monoamines into synaptic vesicles?
- DAT (dopamine transporter)
- NET (norepinephrine transporter)
- SERT (serotonin transporter)
- VMAT (vesicular monoamine transporter)
Correct Answer: VMAT (vesicular monoamine transporter)
Q9. Which enzyme rapidly hydrolyzes acetylcholine in the synaptic cleft?
- Butyrylcholinesterase
- Acetylcholinesterase (AChE)
- Monoamine oxidase (MAO)
- Catechol-O-methyltransferase (COMT)
Correct Answer: Acetylcholinesterase (AChE)
Q10. Which neurotransmitter acts as a gaseous retrograde messenger in the brain?
- Nitric oxide (NO)
- Acetylcholine
- Serotonin
- Glutamate
Correct Answer: Nitric oxide (NO)
Q11. Endocannabinoids are best described as which type of signalling molecules?
- Peptide neurotransmitters stored in dense-core vesicles
- Lipid-derived retrograde messengers acting on CB1 receptors
- Classical small-molecule excitatory amino acids
- Vesicle-stored purinergic transmitters
Correct Answer: Lipid-derived retrograde messengers acting on CB1 receptors
Q12. Which purine acts as a neurotransmitter/modulator in both peripheral and central synapses?
- ATP
- Uric acid
- Guanosine
- Adenosine deaminase
Correct Answer: ATP
Q13. Which neuropeptide is prominently involved in pain transmission and is found in primary afferent neurons?
- Substance P
- Oxytocin
- Insulin
- Vasopressin
Correct Answer: Substance P
Q14. Which neurotransmitter is the major inhibitory neurotransmitter in the adult mammalian brain?
- GABA
- Glutamate
- Acetylcholine
- Dopamine
Correct Answer: GABA
Q15. Which acetylcholine receptor subtype is a ligand-gated ion channel?
- Muscarinic receptor
- Nicotinic receptor
- M1 muscarinic receptor only
- All muscarinic subtypes
Correct Answer: Nicotinic receptor
Q16. The rate-limiting enzyme in serotonin biosynthesis from tryptophan is:
- Aromatic L-amino acid decarboxylase (AAAD)
- Tryptophan hydroxylase
- Monoamine oxidase (MAO)
- Serotonin N-acetyltransferase
Correct Answer: Tryptophan hydroxylase
Q17. Dopamine, norepinephrine and epinephrine are collectively classified as:
- Indolamines
- Catecholamines
- Peptide neurotransmitters
- Amino acid neurotransmitters
Correct Answer: Catecholamines
Q18. Which drug class increases synaptic serotonin primarily by blocking its reuptake?
- Monoamine oxidase inhibitors (MAOIs)
- Tricyclic antidepressants (TCAs)
- Selective serotonin reuptake inhibitors (SSRIs)
- Benzodiazepines
Correct Answer: Selective serotonin reuptake inhibitors (SSRIs)
Q19. NMDA and AMPA receptors are ionotropic receptors activated by which neurotransmitter?
- GABA
- Glutamate
- Dopamine
- Acetylcholine
Correct Answer: Glutamate
Q20. Which mechanism(s) terminate neurotransmitter action at synapses?
- Only enzymatic degradation
- Only diffusion away from the synapse
- Reuptake into the presynaptic terminal and enzymatic degradation
- Only postsynaptic receptor internalization
Correct Answer: Reuptake into the presynaptic terminal and enzymatic degradation
Q21. Where is monoamine oxidase (MAO) primarily located within neurons?
- Synaptic vesicle membrane
- Mitochondrial outer membrane
- Golgi apparatus
- Plasma membrane ion channels
Correct Answer: Mitochondrial outer membrane
Q22. A deficiency of which neurotransmitter in the nigrostriatal pathway is central to Parkinson’s disease?
- Serotonin
- Dopamine
- Acetylcholine
- GABA
Correct Answer: Dopamine
Q23. Serotonin (5-HT) is classified chemically as which subgroup of monoamines?
- Catecholamine
- Indolamine
- Peptide
- Purine
Correct Answer: Indolamine
Q24. Metabotropic neurotransmitter receptors are typically coupled to which intracellular signaling mechanism?
- Ligand-gated ion flux only
- G-protein coupled second-messenger systems
- Direct tyrosine kinase activity only
- Extracellular matrix remodeling
Correct Answer: G-protein coupled second-messenger systems
Q25. Which transporters on astrocytes and neurons are primarily responsible for clearing synaptic glutamate?
- EAAT (excitatory amino acid transporters) such as GLT-1/EAAT2
- VMAT (vesicular monoamine transporter)
- SERT (serotonin transporter)
- GAT (GABA transporter)
Correct Answer: EAAT (excitatory amino acid transporters) such as GLT-1/EAAT2
Q26. What does the term “co-transmission” refer to in synaptic physiology?
- Release of electrical current instead of chemical transmitter
- Release of more than one type of neurotransmitter from the same neuron
- Transmission exclusively between glial cells
- Only retrograde signaling from postsynaptic to presynaptic cell
Correct Answer: Release of more than one type of neurotransmitter from the same neuron
Q27. Which neurotransmitter is centrally involved in wakefulness and allergic responses?
- Histamine
- GABA
- Serotonin
- Glycine
Correct Answer: Histamine
Q28. Which of the following is considered a non-classical neurotransmitter because it diffuses freely and is not stored in vesicles?
- Glutamate
- Nitric oxide (NO)
- Acetylcholine
- Dopamine
Correct Answer: Nitric oxide (NO)
Q29. Mu (μ) opioid receptors, which mediate most opioid analgesia, belong to which receptor family?
- Ligand-gated ion channels
- Receptor tyrosine kinases
- G-protein coupled receptors (GPCRs)
- Nuclear hormone receptors
Correct Answer: G-protein coupled receptors (GPCRs)
Q30. Which drug is a reversible acetylcholinesterase inhibitor commonly used to treat symptoms of Alzheimer’s disease?
- Haloperidol
- Donepezil
- Fluoxetine
- Levodopa
Correct Answer: Donepezil
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.
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