Source: Hypertension  |  Posted 10 years ago

The postsynaptic mesolimbic dopamine system may be chronically underactive in smokers, either as an antecedent or consequence of addiction to cigarettes.

This possibility is implied by a reduction in dopamine D1 receptor density in the ventral striatum of cigarette smokers versus nonsmokers, suggests this study.

Such a hypodopaminergic state may play a critical role in sustaining nicotine-seeking behavior. Or, alternatively, an inherited reduction in dopamine receptors in the striatum may be linked with an increased risk of addiction behavior.

These are the views of A Dagher and colleagues from the McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Canada.

Several drugs of abuse, including nicotine, are believed to exert their reinforcing effects through actions on the mesolimbic dopamine system.

Furthermore, both animal and human studies suggest that chronic administration of addictive drugs may lead to impaired dopamine neurotransmission in the nucleus accumbens.

Thus, these researchers measured D1 receptor density in both smokers and nonsmokers using positron emission tomography and the D1 receptor ligand [(11)C]SCH 23390.

Study participants were 11 smokers and 18 nonsmokers. Of the 11 smokers, 10 were scanned twice, once after overnight abstinence from cigarettes, and once while smoking at their usual rate; this was to account for possible acute effects of cigarette smoking on D1 receptor binding. In addition, eight control subjects were scanned twice to assess the reproducibility of the method.

Researchers used compartmental modeling to measure [(11)C]SCH 23390 binding potential, a measure of D1 receptor density.

No differences were found in binding between abstinent and nonabstinent scans in smokers or in the two scans in controls.

However, there was a significant reduction in [(11)C]SCH 23390 binding potential in smokers compared to nonsmokers in the striatum, most prominently in the ventral striatum.