522. TARGETING OPIOID NEUROTRANSMISSION IN BORDERLINE PERSONALITY DISORDER WITH SELF-HARMING BEHAVIOR: PRELIMINARY FINDINGS OF A [11C]NOP-1A POSITRON EMISSION TOMOGRAPHY STUDY

Abstract Background Non-suicidal self-injury (NSSI) is a core symptom of borderline personality disorder (BPD). Reduced pain sensitivity and increased pain threshold were reported in BPD pointing to an altered pain perception. Though, research investigating biomarkers contributing to attenuated pain sensation in mental disorders is limited. The nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor is involved in pain transmission. Supraspinal administration of N/OFQ in animal studies demonstrated an elevated pain sensation. Aims & Objectives Our study focuses on measuring NOP receptor in BPD with NSSI using positron emission tomography (PET) imaging and the novel radiotracer [11C]NOP-1A. We hypothesize BPD+NSSI would have lower levels of NOP compared to healthy controls (HC) in brain regions altered in BPD and emotional pain processing including anterior cingulate cortex, amygdala, and thalamus. Method 13 BPD+NSSI participants were compared with 16 age and sex-matched HCs. Participants were between 18 to 50 years of age. BPD+NSSI participants were not actively taking psychotropic medication or recreational substances. BPD+NSSI participants met the diagnostic criteria for BPD and at least 7 NSSI episodes in the past 4 months before their enrollment in the study. All participants completed a structural magnetic resonance imaging scan. Using the high resolution research tomograph (HRRT) scanner and arterial blood sampling, NOP binding was recorded following an intravenous injection of the radiotracer [11C]NOP-1A. PMOD (v4.203) and PELI (v2019) were used to calculate the total tissue volume of distribution of NOP (NOP VT) reflected via the Logan graphical analysis method. A linear mixed effects model was used for statistical analysis. Results NOP VT levels were 4.9% lower in amygdala (p-value = 0.048) and Brodmann Area 25 (p-value = 0.046) in BPD+NSSI participants compared to HCs. Moreover, there was a 4.8% and 4.4% mean difference in thalamus (p-value = 0.054) and ventral striatum (p-value = 0.073), respectively. Discussion & Conclusions Although these results are preliminary, attenuated NOP signaling in limbic areas indicates that an endogenous imbalance may be present, which could be a contributing factor to dampened pain sensation in BPD+NSSI. The limbic regions investigated in our study are known to be involved in processing affective aspects of pain, while emotional instability is a cardinal feature of BPD. We aim to enroll more participants in the study to strengthen our findings.