During inflammation, two classes of mediators evoke pain. One is prostaglandin E2 acting on nociceptors. The other is a nonapeptide generated by kallikrein cleavage of high molecular weight kininogen. What is this second pain-mediating substance?
- A Substance P
- B Bradykinin ✓
- C Serotonin
- D Histamine
Correct answer: B. Bradykinin
Explanation
Bradykinin, a nine amino acid peptide split from high molecular weight kininogen by kallikrein in the factor XII activated contact system, causes pain when injected intradermally, increases vascular permeability, and contracts smooth muscle. Substance P is a neuropeptide transmitter of pain fibers rather than a kinin, and histamine and serotonin cause vascular dilation and permeability changes but are not established direct algogenic mediators, which eliminates those distractors.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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