Dopamine pathways in the limbic system are very old in evolutionary terms.
They play an important role in our biological drives for survival and reproduction.
The ability to elevate dopamine levels in the brain is common to all mood-altering drugs (Nash, M. 1997).
Addicts do not crave heroin, cocaine, or alcohol per se but the rush of dopamine these drugs produce (Nash, M. 1997).
Floods of dopamine in the limbic system produce feelings of pleasure and euphoria, loss of control, and compulsive responses to drug-related cues (Fowler, J. S., et al. 2007; Nestler, E. J. 2005).
The amount of dopamine connecting to receptors in this area after a dose of cocaine exceeds the amount caused by naturally pleasurable activities, such as sex, causing the addict to seek this reward over naturally rewarding activities (Fowler, J. S., et al. 2007; Nestler, E. J. 2005).
The limbic system also records memories of intense emotional responses and associates them with the activity that produced those responses. This helps us focus on seeking out activities that will produce pleasure and promote survival, and avoid activities associated with pain, fear, or trauma (Nestler, E. J. 2005).
Drugs are more addictive when they enter the brain rapidly and cause a large dopamine spike that falls off quickly (Fowler, J. S., et.et al. 2007).
Cravings occur when the euphoria subsides and persist as long as this area of the brain remains activated (Fowler, J. S., et al. 2007).
Chronic exposure to the drug reduces the availability of dopamine transporters, indicating a loss of dopamine cells (Fowler, J. S., et. al. 2007).
Fewer dopamine transporters are associated with poor memory, low moods and slower motor function (Fowler, J. S., et al. 2007).