Reliability of striatal [¹¹C]raclopride binding in smokers wearing transdermal nicotine patches

Abstract

Purpose: In studies where [(11)C]raclopride (RAC) positron emission tomography (PET) is used to assess changes in striatal dopamine, it is important to control for cognitive states, such as drug craving, that could alter dopamine levels. In cigarette smokers, transdermal nicotine patches (TNP) can control nicotine craving, but the effects of nicotine patches on RAC binding are unknown. Thus, we sought to determine the test-retest reliability of RAC binding in the presence of nicotine patches.

Methods: Eleven male smokers were scanned twice with RAC on separate days while wearing TNP.

Results: Across the striatum, test-retest variability was 7.63 ± 5.88; percent change in binding potential was 1.11 ± 9.83; and the intraclass correlation coefficient was 0.91 (p < 0.0001).

Conclusion: Baseline RAC binding is highly reproducible in smokers wearing nicotine patches. This suggests that TNP are an acceptable method for controlling cigarette craving during studies that utilize RAC to examine changes in dopamine.

Fig. 1

General outline of study day, starting with subject arrival at ~ 8:00 a.m. All times are approximate. CWS: Cigarette Withdrawal Scale; EtOH: alcohol; MRI: magnetic resonance imaging; RAC: [¹¹C]raclopride. Additional details are given in the text.

Fig. 2

Mean ± s.d. cigarette craving ratings from Day 1 (filled circles) and Day 2 (open triangles), and Times 1, 2, and 3 (please see Figure 1 for approximate timing of ratings). The x-axis crosses the y-axis at the value of 4 to denote that 4 is the lowest possible score on the index; for reference, 20 is the highest possible score. Craving ratings did not vary within subjects across either day or time point (see text for details).