The involvement of BDNF-CREB signaling pathways in the pharmacological mechanism of combined SSRI- antipsychotic treatment in schizophrenia.

Previous studies into the mechanism of SSRI-antipsychotic synergism in our laboratory identified unique changes in the brain, particularly in the γ-aminobutyric acid (GABA)-A receptor and its modulators. This study examined the role of brain derived neurotrophic factor (BDNF)-cAMP response element binding (CREB) protein signaling pathways, including protein kinase B (AKT), glycogen synthase kinase (GSK)-3β and related molecules in the molecular response to haloperidol, fluvoxamine, combined haloperidol+fluvoxamine and clozapine treatments in rat frontal cortex, hippocampus and primary cortical neuronal cultures. The effect of fluvoxamine augmentation on BDNF-CREB pathways in peripheral mononuclear cells (PMC׳s) of medicated schizophrenia patients was also studied. Chronic haloperidol (1mg/kg) +fluvoxamine (10mg/kg) treatment increased TrkB receptor and BDNF expression levels, and the phosphorylation of AKT/CREB/GSK-3β, compared to the individual drugs in rat brain. In addition, haloperidol+fluvoxamine treatment improved cognitive functions in rats, indicating that the molecular changes may have a role in behavioral improvement. In primary neuronal cell cultures, pretreatment with a selective PI3K inhibitor abolished the haloperidol+fluvoxamine-induced phosphorylation of AKT and GSK-3β, but did not affect the upregulation of CREB phosphorylation. In the clinic, PMC׳s of treated patients showed upregulation of mRNA expression and protein levels of BDNF, CREB and AKT after addition of fluvoxamine. Analyses of PMC genes and proteins showed significant inter-correlations and some gene changes correlated with improvement in negative and cognitive symptoms. Our study provides new knowledge of the molecular mechanisms of symptom amelioration in schizophrenia and may advance development of new drugs for this disease and other neuropsychiatric disorders.