PLASMA β - ENDORPHIN CONCENTRATION AND SCHIZOPHRENIA ACUTE TREATMENT OUTCOME
Małgorzata Urban-Kowalczyk, Magdalena Kotlicka –Antczak, Dominik Strzelecki, Ewa Rudecka, Janusz Śmigielski
Objectives: Some studies indicated the presence of possible excess of opioid in schizophrenia and its relationship with negative symptoms. Neurons containing endorphins modulate dopaminergic neuronal activity which suggests that pathogenesis of schizophrenia may be associated with an imbalance in the modulatory effect of opioids on the dopaminergic system. The specific role of endogenous opioids in ethiopathology of schizophrenia is still unclear.
Background and aims: The study assessed the relationship of BE concentration and schizophrenia treatment outcome.
Materials and methods: The study samples comprised of 49 patients hospitalized because of severe symptoms of schizophrenia and 47 healthy controls. Psychopathological symptoms were evaluated using PANSS at the onset of hospitalization, after 4, 6 and 10 weeks of treatment. Β-endorphin (BE) plasma concentrations were assessed in all participants; in patients at inclusion to the study (BE1) and after 6 weeks of treatment (BE2). Patients were classified into negative (NEG) and mixed (M) psychopathological subtypes using the PANSS composite index (CI) obtained by subtracting the PANSS negative symptoms subscale score from the positive subscale score. The difference score (ranges from −42 to +42) reflecting the degree of predominance of one positive or negative syndrome in relation to the other.
Results: BE concentration among all participants with schizophrenia was significantly higher than in controls at inclusion to the study (p=0.008) and increased after 6-week treatment (BE1mean 0.52ng/ml vs BE2 mean 0.59 ng/ml; p=0.002). Patients with NEG subtype achieved higher reduction in general psychopathology scale than M subtype (69.5% vs 32.44% ). BE  tended  to  be  higher in  patients  with lower percent amelioration in negative symptoms. Composite index increased significantly during treatment in NEG group (mean -11.36 vs mean -8.73; p=0.000) however, after 10 weeks of hospitalization patients achieved similar value like at onset of treatment (mean-11.36 vs mean -12.36; p=0.268) despite general reduction of psychopathological symptoms severity. Higher BE2 concentration correlated with predominance of negative symptoms after 10 weeks treatment in both patients samples (NEG: r = -0.557, p=0.071; M: r = - 0.585, p = 0.0013). 
Conclusions: BE is involved in ethiopathology of schizophrenia. It might determines specific pattern of psychopathological manifestation and might be related with persistence of negative symptoms of schizophrenia even after effective pharmacological treatment.