Friday, 23 June 2006

Heroin craving not like thirst for water

Image by gaetan lee When an addict craves another shot of their chosen drug, how similar is this urge to the basic human drives for sex, food and water? One way scientists have approached this question is to look at the neurocircuitry underlying craving for drugs and compare it with the neurocircuitry underlying these other drives. A previous study suggested there might be a great deal of overlap – 10 out of the 13 brain areas associated with craving for cocaine were also activated when addicts and control participants watched erotic films.

Now Zhuangwei Xiao and colleagues in China have compared the brain activation triggered when 14 heroin addicts looked either at pictures of people drinking water, people injecting heroin, or at neutral pictures, such as of furniture. The addicts were both thirsty and drug-deprived, having been denied water for 6 hours before scanning, and heroin for an average of 8.5 hours.

The researchers didn’t find the overlap they expected. Compared with looking at neutral pictures, looking at drug-related pictures triggered increased brain activation in frontal, occipital and cerebellar regions. By contrast, looking at water-related pictures didn’t increase activity in any of those regions, but triggered activity in the anterior cingulate.

The researchers concluded: “Our results show an important role of prefrontal cortex in heroin craving and suggest that heroin craving may involve different neural substrates than do desire from basic physiological drives”.

Xiao, Z., Lee, T., Zhang, J.X., Wu, Q., Wu, R., Weng, X. Hu, X. (2006). Thirsty heroin addicts show different fMRI activations when exposed to water-related and drug-related cues. Drug and Alcohol Dependence, 83, 157-162.

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