Where are opioid receptors located?

Where are opioid receptors located?

• A. Brain, spinal cord, and peripheral nerves
• B. Heart and arteries
• C. Lungs and liver
• D. Muscles and bones

Answer: (A)

Opioid receptors are distributed in the brain, spinal cord, and peripheral nerves. They are G-protein–coupled receptors that, when activated, inhibit neurotransmitter release and decrease neuronal excitability, producing analgesia through both central and peripheral mechanisms. This CNS and PNS localization explains why opioids relieve pain by acting on the nervous system itself. They are not primarily located in the heart, arteries, lungs, liver, muscles, or bones, so those tissues are not the main sites for opioid receptor–mediated effects.

Opioid receptors are distributed in the brain, spinal cord, and peripheral nerves. They are G-protein–coupled receptors that, when activated, inhibit neurotransmitter release and decrease neuronal excitability, producing analgesia through both central and peripheral mechanisms. This CNS and PNS localization explains why opioids relieve pain by acting on the nervous system itself. They are not primarily located in the heart, arteries, lungs, liver, muscles, or bones, so those tissues are not the main sites for opioid receptor–mediated effects.