Insights from recent positron emission tomographic studies of drug abuse and dependence

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Abstract

Purpose of review

Recent positron emission tomographic studies demonstrate a variety of abnormalities in the brains of addicted individuals. This review aims to discuss and highlight these findings.

Recent findings

The recent findings are as follows: (a) the reward response to an addictive substance is associated with increased dopamine release in the striatum. (b) Activation of the orbitofrontal region is involved in the reinforcing properties of a drug. (c) Behavioral, cognitive and affective abnormalities are associated with alterations in specific brain networks and regions (e.g., prefrontal cortices) in drug abusers. (d) Personality traits may play a role in the susceptibility to addiction and the brain's responses to drugs. (e) Sex-differences exist for cue-induced craving. (f) Several studies have confirmed decreased D2 receptors in drug users, which is associated with increased salience to drug cues. (g) Serotonergic transporters are decreased in the current users of 3,4-methylene-deoxy-methamphetamine but found normal in the past users of 3,4-methylene-deoxy-methamphetamine.

Summary

Abnormalities in the dopaminergic, opioid, and serotonergic systems in drug abusers are seen in positron emission tomography scans. Decreased D2 receptor densities in drug users, whether premorbid or the consequence of substance misuse, imply a source of the susceptibility to relapse of this population. Insights from these studies could lead to better treatment approaches targeting specific neurotransmitter systems.

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