Moreover, RYGB surgery in HF diet-fed rats has been demonstrated to reduce brain MOR availability in the hypothalamus, amygdala, and striatum as measured by [11C]carfentanil PET imaging, and reduce MOR protein expression in the striatum and prefrontal cortex, compared to those receiving sham surgery [33] These changes in opioid signaling were accompanied by decreased HF diet intake and preference in the RYGB group. Here, OPRM1 is linked to hydrops fetalis.