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The Neurobiology of Drug Addiction

2: Localization of opioid binding sites within the brain and spinal cord

Localization of opiate binding sites

When a person injects heroin (or morphine), the drug travels quickly to the brain through the bloodstream.  Actually, heroin can reach the brain just as quickly if it is smoked (see description of slide #25).  Users also snort heroin to avoid problems with needles.  In this case, the heroin doesn't reach the brain as quickly as if it were injected or smoked, but its effects can last longer.  Once in the brain, the heroin is converted to morphine by enzymes; the morphine binds to opioid receptors in certain areas of the brain.  Point to the areas where opioids bind (green dots). Part of the cerebral cortex, the VTA, nucleus accumbens, thalamus, brainstem and spinal cord are highlighted.  Show that the morphine binds to opioid receptors that are concentrated in areas within the reward pathway (including the VTA, nucleus accumbens and cortex).  Morphine also binds to areas involved in the pain pathway (including the thalamus, brainstem and spinal cord). Binding of morphine to areas in the pain pathway leads to analgesia.

This page was last updated November 2019

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NIDA. (2019, November 19). The Neurobiology of Drug Addiction. Retrieved from https://www.drugabuse.gov/neurobiology-drug-addiction

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