Extrastriatal Dopamine D2/3 Receptor Availability in Alcohol Use Disorder and Individuals at High Risk

INTRODUCTION

Reduced striatal dopamine D2/3 receptor availability in alcohol use disorder (AUD) has been demonstrated in recent clinical studies and meta-analyses. However, only a limited number of studies investigated extrastriatal D2/3 availability in AUD or in at-risk populations. In line with a dimensional understanding of addiction, extrastriatal dopaminergic neuroadaptations have been suggested to be relevant from a pathobiological perspective.

METHODS

We investigated D2/3 receptor availability via 18F-fallypride positron emission tomography applying a region of interest (ROI) approach. We selected ROIs for the prefrontal cortex (PFC) and the anterior cingulate cortex (ACC). Our sample included 19 healthy controls (low risk [LR]), 19 individuals at high risk (HR) to develop addiction, and 20 recently detoxified AUD patients.

RESULTS

We found significantly higher D2/3 receptor availability of HR compared to AUD in the left and right rostral ACC (rACC), as well as in the left ventrolateral PFC (vlPFC). We did not observe a significant difference between AUD and LR. After corrections for multiple comparisons none of the ROIs reached significance throughout the group comparison. The D2/3 receptor availability in the left rACC was inversely correlated with symptom severity assessed with the Alcohol Dependency Scale.

DISCUSSION

To our knowledge, the present work is the first study investigating extrastriatal D2/3 receptor availabilities in individuals at HR and patients with AUD. The observation that D2/3 receptor availabilities are highest in HR might suggest that their pathobiology differs from subjects with AUD. Future studies are necessary to clarify the intraindividual course of this biomarker over different disease stages and its possible role as a risk or protective factor.

Lack of consistent sex differences in D-amphetamine-induced dopamine release measured with [18F]fallypride PET

RATIONALE

Sex differences in the dopaminergic response to psychostimulants could have implications for drug abuse risk and other psychopathology involving the dopamine system, but human data are limited and mixed.

OBJECTIVES

Here, we sought to investigate sex differences in dopamine release after oral D-amphetamine administration.

METHODS

We used [¹⁸F]fallypride positron emission tomography (PET) to measure the change in dopamine D2/3 receptor availability (%ΔBP_ND, an index of dopamine release) between placebo and D-amphetamine sessions in two independent datasets containing a total of 39 females (on either hormonal birth control n = 18, postmenopausal n = 10, or studied in the first 10 days of their menstrual cycle n = 11) and 37 males.

RESULTS

Using both a priori anatomical regions of interest based on previous findings and voxelwise analyses, we failed to consistently detect broad sex differences in D-amphetamine-induced dopamine release. Nevertheless, there was limited evidence for greater right ventral striatal dopamine release in young adult males relative to similarly aged females, but this was not consistently observed across samples. Plasma estradiol did not correlate with dopamine release and this measure did not differ in females on and off hormonal birth control.

CONCLUSIONS

While our finding in young adults from one dataset of greater %ΔBP_ND in males is partially consistent with a previously published study on sex differences in D-amphetamine-induced dopamine release, our data do not support the presence of consistent widespread sex differences in this measure of dopamine release.