Abstract
The presentation of drug-associated cues has been shown to elicit craving and dopamine release in the striatum of drug-dependent individuals. Similarly, exposure to tobacco-associated cues induces craving and increases the propensity to relapse in tobacco- dependent smokers. However, whether exposure to tobacco-associated cues elicits dopamine release in the striatum of smokers remains to be investigated. We hypothesized that presentation of smoking-related cues compared to neutral cues would induce craving and elevation of intrasynaptic dopamine levels in subregions of the striatum and that the magnitude of dopamine release would be correlated with subjective levels of craving in briefly abstinent tobacco smokers. Eighteen participants underwent two [11C]-(+)-PHNO positron emission tomography (PET) scans after one-hour abstinence period: one during presentation of smoking-associated images and one during presentation of neutral images. Smoking cues significantly increased craving compared to neutral cues on one, but not all, craving measures; however, this increase in craving was not associated with overall significant differences in [11C]-(+)-PHNO binding potential (BPND) (an indirect measure of dopamine release) between the two experimental conditions in any of the brain regions of interest sampled. Our findings suggest that presentation of smoking cues does not elicit detectable (by PET) overall increases in dopamine in humans after one-hour nicotine abstinence. Future research should consider studying smoking cue-induced dopamine release at a longer abstinence period, since recent findings suggest the ability of smoking-related cues to induce craving is associated with a longer duration of smoking abstinence.
Highlights
Smoking is the leading preventable cause of morbidity and mortality in Western Society
Repeated measures analysis of variance (RM-ANOVA) of craving scores obtained with the Visual Analog Scale (VAS) question ‘‘I have a craving for a cigarette’’ indicated separate main effects of cue-type (F(1,17) = 6.935, p,0.05) and time (F(7,119) = 18.098, p,0.005) on self reported craving such that self-reported craving was greater during presentation of smoking vs. neutral cues and self reported craving increased with time
We found that presentation of smoking cues in our setting elicited craving on the VAS, but this finding was not supported by other measures of craving (QSU, Tobacco Craving Questionnaire (TCQ))
Summary
Smoking is the leading preventable cause of morbidity and mortality in Western Society. PET is versatile and a minimally invasive technique that can be used to assess dopaminergic response to a pharmacological or nonpharmacological challenge (such as conditioned stimuli presentation) in humans [24] In this regard, PET studies have shown DA release in sub-compartments of the striatum of both cocaine [6,22] and opiate [21] addicted individuals in response to drug-related imagery, which was related to addiction severity and drug craving [6,22]. Despite the evidence from animal models of addiction, and neuroimaging studies suggesting the importance of DA in cue-induced drug-seeking and craving, no research to date has investigated the dopaminergic response to presentation of smoking-related cues compared to neutral cues in tobacco smokers. Our choice of using [11C]-(+)-PHNO (vs. [11C]raclopride) was motivated by the finding that [11C]-(+)-PHNO has a higher displacement potential relative to [11C]raclopride and may be more sensitive to detect acute fluctuations in DA release induced by smoking-related conditioned cues [36,37,38]
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