Which statement describes the mechanism of action of capsaicin?

Which statement describes the mechanism of action of capsaicin?

• A. Causes skin vasodilation to increase blood flow
• B. Capsaicin reduces TRPV1 receptor on pain fibers in the skin
• C. Blocks histamine H1 receptors
• D. Stimulates growth of nociceptive nerves

Answer: (B)

Capsaicin exerts its analgesic effect by acting on TRPV1 receptors on nociceptive nerve fibers. It first activates these receptors, causing Ca2+ influx and the release of neuropeptides like substance P, which explains the initial burning sensation. With repeated exposure, the nociceptors become desensitized, and TRPV1 function and receptor availability decrease (downregulation), along with depletion of substance P. This desensitization reduces pain signaling from the area, which is captured by the idea that capsaicin lowers TRPV1 receptor activity on pain fibers in the skin. The other statements don’t describe this mechanism: capsaicin is not primarily about vasodilation, it does not block histamine H1 receptors, and it does not promote growth of nociceptive nerves.

Capsaicin exerts its analgesic effect by acting on TRPV1 receptors on nociceptive nerve fibers. It first activates these receptors, causing Ca2+ influx and the release of neuropeptides like substance P, which explains the initial burning sensation. With repeated exposure, the nociceptors become desensitized, and TRPV1 function and receptor availability decrease (downregulation), along with depletion of substance P. This desensitization reduces pain signaling from the area, which is captured by the idea that capsaicin lowers TRPV1 receptor activity on pain fibers in the skin. The other statements don’t describe this mechanism: capsaicin is not primarily about vasodilation, it does not block histamine H1 receptors, and it does not promote growth of nociceptive nerves.