What is the net effect of opioid receptor activation on pain signaling?

What is the net effect of opioid receptor activation on pain signaling?

• A. Pain signals are suppressed
• B. Pain signals are amplified
• C. Pain signals remain unchanged
• D. Pain signals are redirected

Answer: (A)

Opioid receptor activation suppresses pain signaling. These receptors are Gi/o-coupled, so they dampen the neural transmission of pain in multiple ways. Presynaptically, activation closes voltage-gated calcium channels on nociceptive terminals, reducing release of pain neurotransmitters such as substance P and glutamate. Postsynaptically, opening potassium channels hyperpolarizes the neuron, making it harder to reach threshold and fire in response to nociceptive input. In the brain, opioid receptors also engage descending inhibitory pathways, enhancing analgesia. The combined effect is a net decrease in the propagation and perception of pain signals.

Opioid receptor activation suppresses pain signaling. These receptors are Gi/o-coupled, so they dampen the neural transmission of pain in multiple ways. Presynaptically, activation closes voltage-gated calcium channels on nociceptive terminals, reducing release of pain neurotransmitters such as substance P and glutamate. Postsynaptically, opening potassium channels hyperpolarizes the neuron, making it harder to reach threshold and fire in response to nociceptive input. In the brain, opioid receptors also engage descending inhibitory pathways, enhancing analgesia. The combined effect is a net decrease in the propagation and perception of pain signals.