Objective: Substantial evidence from animal models demonstrates that dopamine release in the ventral striatum underlies the reinforcing properties of nicotine. The authors used [(11)C]raclopride bolus-plus-continuous-infusion positron emission tomography (PET) to determine smoking-induced ventral striatum dopamine release in humans.
Method: Twenty nicotine-dependent smokers (who smoked > or =15 cigarettes/day) underwent a [(11)C]raclopride bolus-plus-continuous-infusion PET session. During the session, subjects had a 10-minute break outside the PET apparatus during which 10 subjects smoked a cigarette and 10 did not smoke (as a control condition).
Results: The group that smoked had greater reductions in [(11)C]raclopride binding potential in ventral striatum regions of interest than the group that did not smoke, particularly in the left ventral caudate/nucleus accumbens and left ventral putamen (range for smoking group=-25.9% to -36.6% reduction). Significant correlations were found between change from before to after the smoking break in craving ratings and change from before to after the break in binding potential for these two regions.
Conclusions: Nicotine-dependent subjects who smoked during a break in PET scanning had greater reductions in [(11)C]raclopride binding potential (an indirect measure of dopamine release) than nicotine-dependent subjects who did not smoke. The magnitude of binding potential changes was comparable to that found in studies that used similar methods to examine the effects of other addictive drugs.