Nociceptin/orphanin FQ peptide receptor antagonist JTC-801 reverses pain and anxiety symptoms in a rat model of post-traumatic stress disorder.

Background and Purpose Single-prolonged stress ( SPS), a rat model of post-traumatic stress disorder ( PTSD), also induces long-lasting hyperalgesia associated with hypocortisolism and elevated nociceptin/orphanin FQ ( N/ OFQ) levels in serum and CSF. Here, we determined the effect of JTC-801 (N-(4-amino-2-methylquinolin-6-yl)-2-(4-ethylphenoxymethyl) benzamide monohydrochloride), a nociceptin/orphanin FQ peptide ( NOP) receptor antagonist, on symptoms of pain and anxiety in rats after SPS exposure, and examined N/ OFQ- NOP receptor system changes. Experimental Approach Male Sprague Dawley rats received JTC-801 (6 mg kg−1 i.p., once daily) during days 7-21 of SPS. The ability of JTC-801 to inhibit N/ OFQ-stimulated [35 S]- GTPγS binding was confirmed in rat brain membranes. Anxiety-like behaviour and pain sensitivity were monitored by changes in elevated plus maze performance and withdrawal responses to thermal and mechanical stimuli. Serum corticosterone and N/ OFQ content in CSF, serum and brain tissues were determined by radioimmunoassay; NOP receptor protein and gene expression in amygdala, hippocampus and periaqueductal grey ( PAG) were examined by immunoblotting and real-time PCR respectively. Key Results JTC-801 treatment reversed SPS-induced mechanical allodynia, thermal hyperalgesia, anxiety-like behaviour and hypocortisolism. Elevated N/ OFQ levels in serum, CSF, PAG and hippocampus at day 21 of SPS were blocked by JTC-801; daily JTC-801 treatment also reversed NOP receptor protein and mRNA up-regulation in amygdala and PAG. Conclusion and Implications JTC-801 reversed SPS-induced anxiety- and pain-like behaviours, and NOP receptor system up-regulation. These findings suggest that N/ OFQ plays an important role in hyperalgesia and allodynia maintenance after SPS. NOP receptor antagonists may provide effective treatment for co-morbid PTSD and pain. Linked Articles This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit [ABSTRACT FROM AUTHOR]