Which neurotransmitters are released by descending pain pathway neurons to reduce pain?

• A. Norepinephrine and serotonin
• B. Dopamine and GABA
• C. Acetylcholine and glutamate
• D. Histamine and norepinephrine

Answer: (A)

Descending pain modulation relies on brainstem neurons that project to the spinal cord to dampen nociceptive signals. The neurotransmitters released by these descending neurons are norepinephrine and serotonin. Norepinephrine acts on alpha-2 adrenergic receptors to decrease the release of excitatory transmitters and to boost inhibitory influence in the dorsal horn, while serotonin modulates pain through various 5-HT receptors, often inhibiting excitatory transmission and enhancing inhibition. Together, these monoamines produce a powerful analgesic effect and can interact with endogenous opioids to amplify relief. Other pairings don’t reflect the primary descending analgesic transmitters; dopamine and GABA, or acetylcholine and glutamate, aren’t the main descending pathway messengers for pain inhibition, and histamine isn’t a key player in this descending system.