To test the hypothesis that rejection sensitivity (RS) is negatively associated with mu opioid receptor (MOR) activation during rejection and acceptance tasks. In an exploratory analysis, we assessed the relationships between MOR activation and changes in mood and self-esteem before and after the task.

Endogenous opioid pathways have been shown to play a role in the neurological response to social rejection and acceptance. The MOR related biological underpinnings of RS, a common feature of borderline personality disorder and major depressive disorder, have not yet been examined.

RS was assessed with the Adult Rejection Sensitivity Questionnaire. Healthy participants, n = 75 (52% female), completed rejection and acceptance tasks during [¹¹C]carfentanil positron emission tomography (PET) scans, with self-reported levels of self-esteem and mood collected during and after each task. Nondisplaceable binding potential (BP_ND) was calculated and MOR activation (BP_ND neutral - BP_ND social task) in the regions of interest (amygdala, midline thalamus, anterior insula, and nucleus accumbens) were evaluated.

RS was not related to regional MOR activation during acceptance or rejection tasks. MOR activation in the nucleus accumbens was positively correlated with increase in ratings of self-esteem (r=0.35, uncorrected p=0.0064) and also with the feelings “happy and accepted” (r=0.31, uncorrected p=0.0094) during the period between acceptance task administration and 5 minutes after the task completion. MOR activation was not associated with rejection task related self-esteem and negative mood.

Our previous publication (Hsu et al. 2013) demonstrates that this social rejection task induces MOR activation. We presently demonstrate that regional MOR activation during social rejection is not dependent on RS in healthy individuals, suggesting regional endogenous opioid response to social rejection is independent of this trait. MOR activation in the nucleus accumbens was associated with increased self-esteem and positive mood after experiencing social acceptance, warranting further investigation.