New Brain Studies Yield Insights Into Cocaine Binging and Addiction

Scientists supported by the National Institute on Drug Abuse (NIDA) have identified some of the unique properties of cocaine that account for the binging pattern of use exhibited by cocaine addicts. Their studies show that repeated and frequent activation of the dopaminergic system by cocaine results in an abnormal state in one of the brain's neural circuits. This altered brain circuit may be responsible for the dramatic difference in brain functioning which has been found to exist between the occasional drug user and the cocaine addict. This study is published in the winter 1996 issue, Vol. 15, No. 4, of the Journal of Addictive Diseases.

Cocaine use is uniquely characterized by binging. Cocaine produces a rapid, yet short-lived "high," which results in users consuming the drug frequently and repeatedly. This pattern of binging appears tied to the unique way cocaine affects the brain. Researchers compared cocaine to a chemically-similar stimulant drug, methylphenidate, and found that both drugs are taken up in the same regions of the brain very rapidly, but the rates of clearance from the brain are very different; cocaine clears from the brain much faster than methylphenidate.

The rapid uptake of both cocaine and methylphenidate account for their initial pleasurable experience, or the "high" that is experienced by users. However, unlike methylphenidate, the extremely fast clearance of cocaine from the brain sets the stage for frequent abuse, craving of the drug, and the binging pattern of use frequently exhibited by cocaine addicts. Then, following long-term binging, the continual stimulation of particular neural circuits is thought to lead to long-term changes in the brains of chronic cocaine users that in turn lead to further compulsive drug use.

"These findings have significant implications for the development of treatments for cocaine addiction," said Dr. Alan I. Leshner, Director of NIDA. "Using the knowledge from this study will enable us to develop both medications that target appropriate mechanisms in the brain as well as behavioral therapies to extinguish drug-seeking behavior," added Dr. Leshner.

Dr. Nora Volkow, principal investigator of the study, said "Our research has shown that cocaine binging and addiction must be understood both in terms of the pharmacokinetic properties of cocaine that make it so addictive, as well as the characteristics of the individuals who become addicted to it. Both biological as well as environmental factors must be considered."

These studies conducted by Dr. Volkow and her colleagues use a state-of-the-art neuroimaging technique, called positron emission tomography (PET), that allows researchers to view biological activity in the brains of awake subjects. "Now, for the first time, we can get a direct measure of how drugs affect the structure and functioning of the human brain," said Dr. Leshner. He added that, "With these neuroimaging techniques, we are witnessing extremely exciting times for substantial advances to be made in the area of drug addiction as well as other brain diseases."

NIDA, a component of the National Institutes of Health, supports over 85 percent of the world's research on drug abuse and addiction. Its mission is to conduct and support research to increase knowledge and to promote effective strategies to deal with the health problems and issues associated with drug abuse and addiction.

For more information about this study and other research support by NIDA, contact the NIDA Press Office at (301) 443-6245. NIDA Media Advisories and other information materials are available on the NIDA Home Page at http://www.nida.nih.gov.