2: Localization of opiate binding sites within the brain and spinal cord
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 image #25). Abusers 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 opiate receptors in certain areas of the brain. Point to the areas where opiates 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 opiate 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 (loss of pain).
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National Institute on Drug Abuse (2007). 2: Localization of opiate binding sites within the brain and spinal cord. In The Neurobiology of Drug Addiction. Retrieved from http://www.drugabuse.gov/publications/teaching-packets/neurobiology-drug-addiction/section-iii-action-heroin-morphine/2-localization-opiate-binding-si
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