Posttraumatic stress disorder (PTSD) is a trauma-induced mental disorder characterized by fear extinction abnormalities, which involve biological dysfunctions among fear circuit areas in the brain. Oxytocin (OXT) is a neuropeptide that regulates sexual reproduction and social interaction and has recently earned specific attention due to its role in adjusting neurobiological and behavioral correlates of PTSD; however, the mechanism by which this is achieved remains unclear. The present study aimed to examine whether the effects of OXT on traumatic stress-induced abnormalities of fear extinction (specifically induced by single prolonged stress (SPS), an animal model of PTSD) are associated with pro-inflammatory cytokines. Seven days after SPS, rats received intranasal OXT 40 min before a cue-dependent Pavlovian fear conditioning-extinction test in which rats’ freezing degree was used to reflect the outcome of fear extinction. We also measured mRNA expression of IL-1β, IFN-γ, and TNF-α in the medial prefrontal cortex (mPFC), hippocampus, and amygdala at the end of the study, together with plasma oxytocin, corticosterone, IL-1β, IFN-γ, and TNF-α, to reflect the central and peripheral changes of stress-related hormones and cytokines after SPS. Our results suggested that intranasal OXT effectively amends the SPS-impaired behavior of fear extinction retrieval. Moreover, it neurochemically reverses the SPS increase in pro-inflammatory cytokines; thus, IL-1β and IFN-γ can be further blocked by the OXT antagonist atosiban (ASB) in the hippocampus. Peripheral profiles revealed a similar response pattern to SPS of OXT and corticosterone (CORT), and the SPS-induced increase in plasma levels of IL-1β and TNF-α could be reduced by OXT. The present study suggests potential therapeutic effects of OXT in both behavioral and neuroinflammatory profiles of PTSD.

BackgroundTraumatic experience may lead to various psychological sequelae including the unforgettable trauma-associated memory as seen in posttraumatic stress disorder (PTSD), with a mechanism of impaired fear extinction due to biological imbalance among hypothalamic-pituitary-adrenal (HPA) axis and fear circuit areas such as medial prefrontal cortex (mPFC), hippocampus, and amygdala. Recently the impaired sociability seen in PTSD patients received great attention and the involvement of oxytocin (OXT) mediation is worth being investigated. This study examined whether the trauma-altered prosocial behavior can be modulated by OXT manipulation and its relationship with corticotropin-releasing hormone (CRH) signaling.MethodsMale rats previously exposed to a single prolonged stress (SPS) were evaluated for their performance in social choice test (SCT) and novel object recognition test (NORT) following the introduction of intranasal oxytocin (OXT) and OXT receptor antagonist atosiban (ASB). OXT receptors (OXTR) and CRH receptors (CRHR1, CRHR2) were quantified in both protein and mRNA levels in medial prefrontal cortex (mPFC), hippocampus, and amygdala.ResultsSPS reduced inclination of rats staying at the sociable place with performing less prosocial contacts. OXT can amend the deficit but this effect was blocked by ASB. Expression of OXTR became reduced following SPS in mPFC and amygdala, the latter exhibited higher therapeutic specificity to OXT. Expression of CRHR1 appeared more sensitive than CRHR2 to SPS, higher CRHR1 protein levels were found in mPFC and amygdala.ConclusionPsychological trauma-impaired sociability is highly associated with OXT signaling pathway. Intranasal OXT restored both the SPS-impaired prosocial contacts and the SPS-reduced OXTR expressions in mPFC and amygdala. OXT may have therapeutic potential to treat PTSD patients with impaired social behaviors.

Inflammation has been considered important in the pathogenesis of schizophrenia. Increasing evidence reveals that patients with schizophrenia have abnormal expression of cytokines, which are related to development of metabolic abnormalities. Metabolic abnormality has become a critical issue, though its longitudinal relationship with the disorder, such as the antipsychotics influence, is unclear. We aimed to investigate whether abnormalities of metabolic parameters and cytokine levels in acute exacerbated schizophrenic patients existed, and whether intervention of antipsychotic could help. The present study analyzed peripheral cytokines and metabolic/hemodynamic parameters in healthy controls and acute exacerbated schizophrenic patients hospitalized for three weeks under the unique treatment of quetiapine, a well-known second-generation antipsychotic. Our results showed that patients with schizophrenia were predisposed to metabolic abnormalities in acute exacerbation, including body mass index (BMI) and waist circumference (WC). The patients were also prone to dysglycemia, lower high-density lipoprotein cholesterol (HDL-c) levels, and higher blood pressure with concomitant of elevation of interleukin (IL)-2, IL-6 and IL-10 in which IL-6 was associated with BMI. After quetiapine treatment, IL-2, IL-6 and IL-10 remained higher than the controls, but IL-10 was significantly decreased in follow-up comparison. Glycemic-related indexes, HDL-c and IL-10 levels were significantly changed by variance analysis. Results of the present study imply that acute exacerbated schizophrenic patients with metabolism abnormalities may involve disruption of expression of cytokines, and that quetiapine may have therapeutic effects. Nonetheless, metabolism parameters of patients undergoing treatment with quetiapine should be closely monitored.