Effects of smoking on D₂/D₃ striatal receptor availability in alcoholics and social drinkers

Studies have reported lower striatal D₂/D₃ receptor availability in both alcoholics and cigarette smokers relative to healthy controls. These substances are commonly co-abused, yet the relationship between comorbid alcohol/tobacco abuse and striatal D₂/D₃ receptor availability has not been examined. We sought to determine the degree to which dual abuse of alcohol and tobacco is associated with lower D₂/D₃ receptor availability. Eighty-one subjects (34 nontreatment-seeking alcoholic smokers [NTS-S], 21 social-drinking smokers [SD-S], and 26 social-drinking non-smokers [SD-NS]) received baseline [(11)C]raclopride scans. D₂/D₃ binding potential (BPND ≡ Bavail/KD) was estimated for ten anatomically defined striatal regions of interest (ROIs). Significant group effects were detected in bilateral pre-commissural dorsal putamen, bilateral pre-commissural dorsal caudate; and bilateral post-commissural dorsal putamen. Post-hoc testing revealed that, regardless of drinking status, smokers had lower D₂/D₃ receptor availability than non-smoking controls. Chronic tobacco smokers have lower striatal D₂/D₃ receptor availability than non-smokers, independent of alcohol use. Additional studies are needed to identify the mechanisms by which chronic tobacco smoking is associated with striatal dopamine receptor availability.