The syndrome is defined by abnormalities in brain-reward processes involving specific neural pathways. It is suspected in some cases to have a genetic component that may predispose some individuals to addiction-not only to strong stimulants like opiates but to weaker stimulants like alcohol, nicotine, gambling, sex, violence, cannabis and food.

Michael Bozarth, associate professor of psychology, was among a small number of scientists whose research originally suggested an empirical relationship between the neurotransmitter dopamine, which is associated with feelings of pleasure, and certain addictions.

Bozarth, director of the Addiction Research Unit in the Department of Psychology in the College of Arts and Letters, will present an invited lecture on this subject to the First Conference on Reward Deficiency Syndrome: Genetic Antecedents and Clinical Pathways, to be held Nov. 12-13 in San Francisco.

He will address the relationship between neural-reward mechanisms and normal and pathological behavior, and specifically, the dopamine link as a target for therapeutic intervention in addictive behavior.

Bozarth explains that those participating in the meeting will include many scientists whose studies suggest a relationship between addiction, dopamine production and the dopamine D2 receptor, and scientists whose pioneering research suggests the possibility of a genetic disorder that predisposes tens of millions to addiction.

Although Bozarth's research does not involve the study of genetics, it indicates that dopamine plays a role in addiction to opiates, such as heroin and morphine. His work contributed significantly to the current view that different addictions, as well as psycho-pathological behaviors like problem gambling, may involve a common neural substrate. Prior to this finding, scientists had assumed that different mechanisms were responsible for various substance-abuse disorders.

Bozarth points out that in healthy individuals, normal life activities provoke the release of dopamine, which evokes feelings of pleasure. It is presumed that in some individuals, however, this reward system in brain is not working properly.

"Their brains appear to release less dopamine than might be expected under normal circumstances or the released dopamine has less effect because its receptors in the brain are not functioning properly," Bozarth says. "This may be because of depression or other underlying pathology, some of which are genetically based."

Under most circumstances, he says, such people may be relatively anhedonic-that is, unable to feel pleasure to the same extent as most people.

Even people with normal, healthy brains can be easily addicted to drugs like cocaine and heroin, Bozarth says, because such drugs provoke the release of a flood of dopamine, producing pleasure so intense that it often results in a craving that can, in turn, can lead to addiction.

"Some scientists postulate that individuals whose brains do not release dopamine in normal quantities, or do not have properly functioning receptors for dopamine, would be particularly susceptible to addiction," he says.

"This is because when they are introduced to an external stimulant, the feelings of pleasure produced are extremely intense compared to what they normally experience. They are overwhelmed by a craving so profound that the pursuit of the stimulant begins to take over their lives. They seem to lose control over their own behavior. The brain actually changes.

"It is further postulated," he says, "that such individuals are vulnerable not just to extremely addictive drugs like heroin or cocaine, which as I said, can addict even normal brains, but to weaker stimulants as well—alcohol, nicotine, gambling, sex, food. In this case, too, the pleasure they receive from exposure to these stimulants so far exceeds what they normally feel that a craving is set up even to the lesser stimulants."

Bozarth emphasizes, however, that while some such addictions may indeed be produced by dopamine deprivation, "it is certainly the case that not all substance-abuse disorders are caused by a common action on a single brain system.

"What has spawned a new way of looking at addiction," he says, "is the fact that many of the potent motivational, and hence addictive, properties of different substances seem to involve a common neurochemical action. The (San Francisco) conference will address new findings about the relationship between neurotransmitters, their receptors in the brain and addictive action."