The finding, reported in the January issue of Biological Psychiatry, demonstrates that repeated exposure to different types of drugs of abuse, such as cocaine, nicotine, amphetamine and alcohol, lead to a persistent or long-term reduction in the electrical activity of dopamine neurons in the brain.
Dopamine neurons are the origin of the reward pathway responsible for the "feel good" experience that is such a strong component of drug use and abuse.
"A persistent reduction in dopamine neuron electrical activity after repeated exposure to different types of drugs appears to be the result of excessive excitation of dopamine neurons," according to Roh-Yu Shen (photo), a neuroscientist and the lead investigator on the study. "This represents a new and potentially critical neural mechanism for addiction and provides a working model that suggests how the reward pathway function is altered and how these changes can be responsible for triggering intense craving and compulsive drug-seeking." Source.