Substance P MCQs With Answer

Substance P MCQs With Answer

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Substance P MCQs With Answer

Substance P is a key neuropeptide in the tachykinin family involved in nociception, neurogenic inflammation, and neurotransmission. B. Pharm students should understand its synthesis from the TAC1 gene, structure (an 11‑amino‑acid peptide), primary NK1 receptor signaling (Gq/PLC pathway), degradation by neprilysin, and clinical relevance such as NK1 antagonists (aprepitant) for chemotherapy‑induced nausea. Knowledge of distribution in sensory C‑fibers, co‑localization with CGRP, and roles in asthma, GI motility, and pain modulation informs pharmacological targeting and drug design. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which class of biomolecule is Substance P?

  • Neuropeptide
  • Monoamine neurotransmitter
  • Steroid hormone
  • Cytokine

Correct Answer: Neuropeptide

Q2. The primary receptor mediating Substance P effects is:

  • NK1 receptor
  • NK2 receptor
  • NK3 receptor
  • Mu‑opioid receptor

Correct Answer: NK1 receptor

Q3. Which gene encodes the precursor for Substance P?

  • TAC1
  • TAC3
  • POMC
  • TAC4

Correct Answer: TAC1

Q4. How many amino acids comprise the mature Substance P peptide?

  • 7 amino acids
  • 11 amino acids
  • 14 amino acids
  • 21 amino acids

Correct Answer: 11 amino acids

Q5. Substance P belongs to which peptide family?

  • Tachykinin family
  • Opioid family
  • Somatostatin family
  • Neuropeptide Y family

Correct Answer: Tachykinin family

Q6. In pain physiology Substance P is best described as:

  • An anti‑nociceptive mediator
  • A pronociceptive mediator
  • A local anesthetic
  • An opioid agonist

Correct Answer: A pronociceptive mediator

Q7. Which enzyme primarily contributes to extracellular degradation of Substance P?

  • Monoamine oxidase (MAO)
  • Catechol‑O‑methyltransferase (COMT)
  • Neprilysin (neutral endopeptidase)
  • Acetylcholinesterase

Correct Answer: Neprilysin (neutral endopeptidase)

Q8. Which NK1 receptor antagonist is widely used as an antiemetic in chemotherapy?

  • Aprepitant
  • Ondansetron
  • Metoclopramide
  • Domperidone

Correct Answer: Aprepitant

Q9. Substance P is frequently co‑localized with which neuropeptide in sensory neurons?

  • Calcitonin gene‑related peptide (CGRP)
  • Substance K
  • Somatostatin
  • Vasoactive intestinal peptide (VIP)

Correct Answer: Calcitonin gene‑related peptide (CGRP)

Q10. Activation of the NK1 receptor primarily couples to which G protein and signaling cascade?

  • Gs → adenylate cyclase → ↑cAMP
  • Gi → inhibition of adenylate cyclase
  • Gq → phospholipase C → IP3/DAG
  • Tyrosine kinase → MAPK directly

Correct Answer: Gq → phospholipase C → IP3/DAG

Q11. Which laboratory technique is commonly used for quantifying Substance P levels in biological samples?

  • ELISA (enzyme‑linked immunosorbent assay)
  • Genomic PCR
  • PECT (positron emission computed tomography)
  • Patch‑clamp electrophysiology

Correct Answer: ELISA (enzyme‑linked immunosorbent assay)

Q12. How many classical tachykinin receptor subtypes are recognized pharmacologically?

  • One
  • Two
  • Three
  • Four

Correct Answer: Three

Q13. A major clinical application of NK1 receptor antagonists is:

  • Antihypertensive therapy
  • Antiemetic therapy for chemotherapy‑induced nausea and vomiting
  • Bronchodilation in asthma
  • Diuretic therapy

Correct Answer: Antiemetic therapy for chemotherapy‑induced nausea and vomiting

Q14. Substance P contributes to inflammation primarily by:

  • Inhibiting blood flow to inflamed tissue
  • Promoting vasodilation and plasma extravasation
  • Inducing vasoconstriction of arterioles
  • Reducing vascular permeability

Correct Answer: Promoting vasodilation and plasma extravasation

Q15. Which region of Substance P is most critical for receptor binding and biological activity?

  • The N‑terminal region
  • The C‑terminal pentapeptide
  • The middle hydrophobic region
  • The signal peptide of preprotachykinin

Correct Answer: The C‑terminal pentapeptide

Q16. Tachykinins share a common C‑terminal sequence motif. Which motif is characteristic?

  • Phe‑X‑Gly‑Leu‑Met (F‑X‑G‑L‑M)
  • Ala‑Pro‑Gly‑Ser‑Thr
  • Lys‑Arg‑Pro‑Gly‑Gly
  • Met‑Leu‑Val‑Ile‑Phe

Correct Answer: Phe‑X‑Gly‑Leu‑Met (F‑X‑G‑L‑M)

Q17. NK1 receptor desensitization and internalization after agonist binding typically involves which mechanism?

  • Clathrin‑mediated endocytosis involving β‑arrestin
  • Direct proteasomal degradation at the membrane
  • Translocation of receptor to the nucleus
  • No internalization occurs; receptors remain permanently active

Correct Answer: Clathrin‑mediated endocytosis involving β‑arrestin

Q18. In chemotherapy‑induced nausea and vomiting (CINV), Substance P is considered:

  • A primary mediator acting via NK1 receptors in central emetic circuits
  • Irrelevant to the emetic response
  • Only a peripheral mediator with no central action
  • Responsible solely for delayed diarrhea

Correct Answer: A primary mediator acting via NK1 receptors in central emetic circuits

Q19. Which cell type is the predominant source of Substance P in the nervous system?

  • Neurons (sensory afferents)
  • Hepatocytes
  • Erythrocytes
  • Fibroblasts

Correct Answer: Neurons (sensory afferents)

Q20. Substance P is characteristically released from which class of peripheral sensory fibers?

  • Large myelinated A‑beta fibers
  • Thinly myelinated A‑delta fibers
  • Unmyelinated C fibers
  • Motor efferent fibers

Correct Answer: Unmyelinated C fibers

Q21. Radiolabeled NK1 ligands used in PET imaging are useful mainly for mapping:

  • NK1 receptor distribution in the brain and peripheral tissues
  • Blood glucose utilization
  • Bone mineral density
  • Cardiac ejection fraction

Correct Answer: NK1 receptor distribution in the brain and peripheral tissues

Q22. Neurokinin A shows highest affinity for which receptor subtype?

  • NK1 receptor
  • NK2 receptor
  • NK3 receptor
  • Delta opioid receptor

Correct Answer: NK2 receptor

Q23. In the respiratory system Substance P typically causes:

  • Bronchodilation and mucus reduction
  • Bronchoconstriction and increased mucus secretion
  • No effect on airway tone
  • Permanent airway remodeling only

Correct Answer: Bronchoconstriction and increased mucus secretion

Q24. The primary effects of Substance P on gastrointestinal function include:

  • Reduced motility and secretion
  • Increased motility and secretion
  • Complete inhibition of peristalsis
  • Induction of intestinal ischemia

Correct Answer: Increased motility and secretion

Q25. The NK1 receptor belongs to which GPCR family/class?

  • Class A (rhodopsin‑like) GPCRs
  • Class B (secretin‑like) GPCRs
  • Class C (metabotropic glutamate) GPCRs
  • Ligand‑gated ion channel family

Correct Answer: Class A (rhodopsin‑like) GPCRs

Q26. Substance P can modulate the release of which excitatory neurotransmitter in the dorsal horn?

  • Glutamate
  • GABA
  • Acetylcholine
  • Dopamine

Correct Answer: Glutamate

Q27. Elevated Substance P levels have been associated with which inflammatory disorder?

  • Rheumatoid arthritis
  • Hypothyroidism
  • Iron deficiency anemia
  • Hyperlipidemia

Correct Answer: Rheumatoid arthritis

Q28. Aprepitant prevents Substance P effects by:

  • Blocking the NK1 receptor to inhibit Substance P binding
  • Increasing Substance P synthesis
  • Enhancing Substance P release from terminals
  • Activating NK1 receptor signaling

Correct Answer: Blocking the NK1 receptor to inhibit Substance P binding

Q29. Preprotachykinin A (TAC1) processing can produce multiple peptides including Substance P and Neurokinin A via:

  • Alternative splicing and post‑translational proteolytic processing
  • Translation of separate genes only
  • Direct secretion without processing
  • Splicing of mitochondrial RNA

Correct Answer: Alternative splicing and post‑translational proteolytic processing

Q30. Which molecular approach is commonly used in research to transiently reduce Substance P expression in neurons?

  • Small interfering RNA (siRNA) targeting TAC1 mRNA
  • Administration of protease inhibitors
  • Beta‑adrenergic blockade
  • Statin therapy

Correct Answer: Small interfering RNA (siRNA) targeting TAC1 mRNA

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