The brain’s mesolimbic dopamine system, its reward pathway, is stimulated by all types of reinforcing stimuli, such as food, sex, and many drugs of abuse, including cocaine.8 This pathway originates in a region of the midbrain called the ventral tegmental area and extends to the nucleus accumbens, one of the brain’s key reward areas.8 Besides reward, this circuit also regulates emotions and motivation.
In the normal communication process, dopamine is released by a neuron into the synapse (the small gap between two neurons), where it binds to specialized proteins called dopamine receptors on the neighboring neuron. By this process, dopamine acts as a chemical messenger, carrying a signal from neuron to neuron. Another specialized protein called a transporter removes dopamine from the synapse to be recycled for further use.8
Drugs of abuse can interfere with this normal communication process. For example, cocaine acts by binding to the dopamine transporter, blocking the removal of dopamine from the synapse. Dopamine then accumulates in the synapse to produce an amplified signal to the receiving neurons. This is what causes the euphoria commonly experienced immediately after taking the drug (see the video "Brain Reward: Understanding How the Brain Responds to Natural Rewards and Drugs of Abuse").
