Objective: To investigate the plasma levels of nociceptin/orphanin FQ (OGQ) in patients with bipolar depression and bipolar mania and to analyze the relationship of plasma OFQ to bipolar disorders.
Methods: Peripheral blood samples were collected from 21 patients with bipolar II depression (BD group), 26 patients with bipolar I mania (BM group), and 31 health adults (control group). The concentrations of plasma OFQ were measured by radioimmunoassay (RIA). The psychological status was examined by Hamilton Depression Scale (HAMD), Bech-Rafaelsen Mania Rating Scale (BRMS), and Montgomery and Asberg Depression Rating Scale (MADRS).
Results: The plasma OFQ level of the BD group was (20+/-4) ng/L, significantly higher than that of the control group [(14+/-5) ng/L, t=5.28, P<0.01], and the OFQ level of the BM group was (11+/-3) ng/L, significantly lower than that of the control group (t=-2.47, P<0.05). There were not significant differences in the plasma OFQ between the males and females in all groups (all P>0.05). In the BD group the plasma OFQ level was significantly positively correlated with HAMD and MADRS scores (r=0.607, P<0.01; r=0.541, P<0.05). In the BM group the plasma OFQ level was significantly negatively correlated with the BRM score (r=-0.750, P<0.01).
Conclusion: The changes of plasma OFQ level may play a role in the pathogenesis of bipolar disorder and indicate the severity of disease. Plasma OFQ may be a new biological parameter of bipolar disorder.