Which statement is true about nociceptor mediators?

Which statement is true about nociceptor mediators?

• A. They include Substance P, acetylcholine, histamine, adenosine, glutamate, H+, and prostaglandins
• B. They are not involved in pain signaling
• C. They originate only in the brain
• D. They do not affect nociception

Answer: (A)

Nociceptor mediators are chemical signals released at sites of tissue injury or inflammation that lower the threshold of pain-sensing neurons and help propagate pain signals. Substances like Substance P, histamine, prostaglandins, glutamate, adenosine, and protons (H+) are classic examples—they come from injured tissue, immune cells, or the nerve endings themselves and act on receptors to heighten nociceptor excitability or transmit signals to the spinal cord. While acetylcholine is present in many neural processes, it is not a primary nociceptor mediator in the same way these others are, whereas the other statements would imply no role for mediators, brain-only origin, or no effect on nociception, which contradicts what we know about how pain signaling works.

Nociceptor mediators are chemical signals released at sites of tissue injury or inflammation that lower the threshold of pain-sensing neurons and help propagate pain signals. Substances like Substance P, histamine, prostaglandins, glutamate, adenosine, and protons (H+) are classic examples—they come from injured tissue, immune cells, or the nerve endings themselves and act on receptors to heighten nociceptor excitability or transmit signals to the spinal cord. While acetylcholine is present in many neural processes, it is not a primary nociceptor mediator in the same way these others are, whereas the other statements would imply no role for mediators, brain-only origin, or no effect on nociception, which contradicts what we know about how pain signaling works.