Dopamine D2/3 receptor availability and amphetamine-induced dopamine release in obesity.

INTRODUCTION: The neurotransmitter dopamine is important in the regulation of food intake. It is hypothesised that obese people experience less reward from food due to lower striatal dopamine release, which consequently leads to overeating. This study is the first to assess whether obese subjects have blunted striatal dopamine release.

METHOD: We measured striatal dopamine D2/3 receptor (DRD2/3) availability and amphetamine-induced striatal dopamine release in 15 obese and 15 age-matched, normal-weight women using [(123)I]iodobenzamide single photon emission computed tomography (SPECT) imaging. In addition, correlations with food craving were examined.

RESULTS: Baseline striatal DRD2/3 availability was lower in obese subjects (0.91 ± 0.16) compared to controls (1.09 ± 0.16; p = 0.006). Amphetamine-induced dopamine release was significant in controls (7.5% ± 9.2; p = 0.007) and not in obese subjects (1.2% ± 17.7; p = 0.802), although the difference in release between groups (d=0.45) was not significant. Dopamine release positively correlated with the trait food craving in obese subjects.

CONCLUSION: This study replicates previous findings of lower striatal DRD2/3 availability in obesity and provides preliminary data that obesity is associated with blunted dopamine release. The positive correlation between dopamine release and food craving in obesity may seem contradictory with the latter finding but is presumably related to heterogeneity within the obese subjects.