The Neurobiology of Drug Addiction

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As you have just explained, different parts of the brain are responsible for the addiction and dependence to heroin and opiates. Review the areas in the brain underlying the addiction to morphine (reward pathway) and those underlying the dependence to morphine (thalamus and brainstem). Thus, it is possible to be dependent on morphine, without being addicted to morphine. (Although, if one is addicted, they are most likely dependent as well.) This is especially true for people being treated chronically with morphine, for example, pain associated with terminal cancer. They may be dependent - if the drug is stopped, they suffer a withdrawal syndrome. But, they are not compulsive users of the morphine, and they are not addicted. Finally, people treated with morphine in the hospital for pain control after surgery are unlikely to become addicted; although they may feel some of the euphoria, the analgesic and sedating effects predominate. There is no compulsive use and the prescribed use is short-lived.

addiction-vs-dependence.gif (52.53 KiB) Viewed 172 times

SOURCE;
https://www.drugabuse.gov/publications/ ... dependence

Brain regions mediating the development of morphine dependence

• The development of dependence to morphine also involves specific areas of the brain, separate from the reward pathway. In this case, point to the thalamus and the brainstem (green dots). The parts of the reward pathway involved in heroin or morphine addiction are shown for comparison. Many of the withdrawal symptoms from heroin or morphine are generated when the opiate receptors in the thalamus and brainstem are deprived of morphine.

SOURCE:
https://www.drugabuse.gov/publications/ ... ing-develo


Definition of Dependence

• With repeated use of heroin, dependence also occurs. Dependence develops when the neurons adapt to the repeated drug exposure and only function normally in the presence of the drug. When the drug is withdrawn, several physiologic reactions occur. These can be mild (e.g., for caffeine) or even life threatening (e.g., for alcohol). This is known as the withdrawal syndrome. In the case of heroin, withdrawal can be very serious and the abuser will use the drug again to avoid the withdrawal syndrome.

dependence.gif (48.16 KiB) Viewed 164 times

SOURCE:
https://www.drugabuse.gov/publications/ ... dependence