August 11, 2013
Brain Dopamine Activity Could Be Risk Indicator For Alcoholism
redOrbit Staff & Wire Reports - Your Universe Online
Individuals who are vulnerable to alcoholism could experience an abnormally large response in the brain’s reward-seeking pathways when they drink, according a new study appearing in the January issue of Alcoholism: Clinical & Experimental Research.
Marco Leyton, a professor of psychiatry at McGill University in Montreal and corresponding author of the study, and his colleagues report when compared to those at low risk of developing alcohol use disorders (AUDs), high-risk men and women showed a greater dopamine response in a brain pathway that increases desire for rewards.
They believe their research could provide new insight into why some individuals are more at risk of suffering from alcoholism, and could be a tremendous step forward in the development of new treatment options.
“A large body of research has implicated a role for dopamine in reward-seeking behaviors in general,” Leyton said in a statement. “For example, in both laboratory animals and people, increased dopamine transmission seems to enhance the ability of reward-related stimuli to grab attention and attract you. This effect likely contributes to why having one drink increases the probability of getting a second one – the alcohol-induced dopamine response makes the second drink look all the more desirable.”
“Many studies have further established that brain dopamine (DA) systems in an area of the brain called the striatum – especially the ventral striatum – are engaged by most drugs of abuse, including alcohol,” added University of Michigan psychology and neuroscience professor Terry E. Robinson. “Of course, these brain systems did not evolve to mediate the effects of drugs, but are normally involved in mediating the motivational properties of 'natural' rewards such as food, water, and sex.”
Those DA systems, Robinson noted, apparently play an essential role in determining the degree to which people crave particular rewards. If they are activated to an unusually high degree, he said, it could lead to a pathological craving for the associated reward. Experts believe that this biological method is how drugs become addictive to people – increasing DA activity to an extreme level, and when they are taken repeatedly, their ability to activate the brain dopamine systems become increasingly effective or “sensitized.”
As part of their study, the McGill University-led research team recruited 26 healthy social drinkers between the ages of 18 and 30. Eight of the study participants were female and 18 were male, and all of them were from the Montreal area. Higher-risk subjects were identified using a combination of personality traits and a reduced intoxication response to alcohol consumption (i.e. feeling less inebriated despite drinking the same amount). Furthermore, each person underwent a pair of positron emission tomography (PET) brain scan exams after drinking either juice or alcohol (about 3 drinks in 15 minutes).
“Although preliminary, the results are compelling,” Leyton said, adding the unusually large brain dopamine response experienced by those most vulnerable to developing AUDs “might energize reward-seeking behaviors and counteract the sedative effects of alcohol. Conversely, people who experience minimal dopamine release when they drink might find the sedative effects of alcohol especially pronounced.”
“Everyone's brain is different and different brains are influenced in quite different ways by many sorts of experiences – not just drugs of abuse. Only a small proportion of those individuals who try drugs of abuse, including alcohol, go on to abuse them and to develop addiction… We need to understand these differences in both assessing risk and in the development of treatments, as it is becoming increasingly clear that one size does not fit all,” Robinson added.