availability than women in multiple brain regions, including the anterior cingulate cortex (ACC), frontal cortex, and insula (Aishwarya Vijay et al., 2016), suggesting that differences in KOR are related to sex differences and not simply a question of sample size. In contrast to the KOR system, studies on the mu opioid receptor (MOR) system demonstrated higher MOR availability in the ventral striatum, amygdala, caudate, and putamen in adults with AUD compared to healthy controls using the radiotracer [11C]carfentanil (Weerts et al., 2011). While a group by sex effect was not significant, women overall had lower MOR availability in ventral striatum (BPND=1.76 ± 0.06 vs. 1.47 ± 0.08) and cingulate (BPND=0.74 ± 0.02 vs. 0.65 ± 0.3) compared to men (Weerts et al., 2011). Findings in the opioid system suggest that there may be underlying SG differences in KOR and MOR availability related to chronic alcohol consumption, albeit the pattern of findings suggests that the KOR and MOR systems may work in opposite directions.
