Results could lead to new treatments for abuse, addiction

By William J. Cromie

Gazette Staff

Researchers have looked into the heads of cocaine addicts and found how different areas of their brains react to the drug. The scientists discovered that a much broader range of brain structures is responsible for feelings of euphoria and craving than previously thought.

"This study gives us a detailed picture of cocaine's effects on brain circuits involved in an immediate, pleasurable reaction and in the motivation to repeat the activity," says Hans Breiter, an instructor in psychiatry at Massachusetts General Hospital (MGH). The experiments were carried out at MGH, using a technique that detects cerebral activity by measuring blood flow to various parts of the brain.

Such research "suggests specific brain areas that might be targeted in developing new medications to either block individual effects like the 'rush' and craving, or to find broader treatments for cocaine abuse and addiction," notes Alan Leshner, director of the National Institute on Drug Abuse.

Brain scans were done on 10 volunteer addicts, as they received injections of cocaine and then for 13 minutes afterward. Starting before the injection and at 15-second intervals during the testing, the subjects reported their feelings of rush, "high," "low," or craving. The combined reports and scans provided the greatest detail to date about reactions of specific parts of the brain and how they relate to the feelings of cocaine users.

Results indicate that more than 90 brain areas showed increased activity in response to the drug. Many structures associated with thought and emotion showed an immediate, although brief, burst of animation associated with reports of rush and euphoria.

Other brain structures stayed active longer, extending into periods when subjects reported feelings of craving to repeat the experience. One of the most significant is an area deep in the brain called the nucleus accumbens, which was thought to be associated with positive and pleasurable feelings.

"Our observations regarding the nucleus accumbens were probably the most unexpected," says Brieter. "We expected it to be activated as part of the rush/high experience. But its continuing high level of activation into the craving phase suggests it also plays a role in the motivation leading to a change in behavior. The latter is key to development of addiction."

"Understanding how different brain circuits are activated during different stages of drug use and withdrawal can help us design and monitor novel treatments [for abuse and addiction]," says Steven Hyman '80, director of the National Institute of Mental Health and former head of the Medical School's Division on Addiction.