Dopaminergic Activity in Depressed Smokers: A Positron Emission Tomography Study

摘要

Tobacco dependence is highly prevalent in depressed patients. We assessed changes in [¹¹C]-raclopride binding potential using positron emission tomography before and after the oral administration of d-amphetamine in healthy controls and unmedicated patients with current depression with and without current tobacco dependence. Over a single study day two [¹¹C]-raclopride positron emission tomography scans were taken in thirty-eight subjects: at baseline and 2 hours following oral d-amphetamine 30mg. Twenty controls (9 smokers, 11 non-smokers) and 18 subjects with current major depressive episode (8 smokers, 10 non-smokers). Striatal [¹¹C]-raclopride binding potential was measured before and after d-amphetamine. Depressed smokers had a lower baseline [¹¹C]-raclopride binding potential compared to both control non-smokers (p < 0.007) and depressed non-smokers (p < 0.001). There was a main effect of smoking status on amphetamine-induced change in [¹¹C]-raclopride binding potential (p <0.02), but no main effect of depression. This may be due to a floor effect because of the low BP (binding potential) at baseline. Depressed subjects reported significant increase of positive mood after d-amphetamine administration compared with controls (depressed smokers vs. control smokers: p < 0.05; depressed non-smokers vs. controls: p < 0.055). Tobacco dependence appears to decrease d-amphetamine-induced changes in [¹¹C]-raclopride binding potential as measured by positron emission tomography. Comorbid major depression and tobacco dependence exacerbates this effect, suggesting an altered dopamine system in comorbid patients.