Small-molecule TrkB agonist 7,8-dihydroxyflavone reverses cognitive and synaptic plasticity deficits in a rat model of schizophrenia

Cognitive deficits are the core symptoms of schizophrenia and major contributors to disability in schizophrenic patients, but effective treatments are still lacking. Previous studies have demonstrated that impaired BDNF/TrkB signaling is associated with the cognitive impairments of schizophrenia. 7,8-Dihydroxyflavone (7,8-DHF) has recently been identified as a specific TrkB agonist that crosses the blood brain barrier after oral or intraperitoneal administration. The present study aimed to assess the effect of 7,8-DHF on the cognitive and synaptic impairments of schizophrenia. A brief disruption of NMDA receptors with MK-801 during early development serves as an animal model for cognitive deficits of schizophrenia. We found that MK-801-treated rats showed significant deficits in working learning ability and hippocampal synaptic plasticity, as well as reduction of BDNF, TrkB, and phosphorylated TrkB in the hippocampus. After intraperitoneal administration with 7,8-DHF (5 mg/kg) once daily for a consecutive 14 days, we found that chronic 7,8-DHF treatment significantly enhanced the activation of phosphorylated TrkB at the Y515 and Y816 sites, increased the phosphorylation levels of TrkB downstream signal cascades including ERK1/2, CaMKII, CREB and GluR1, and promoted hippocampal synaptic plasticity, which in turn rescued performance in spatial working learning. Our results thus demonstrate that activation of TrkB signaling can reverse the cognitive deficits of schizophrenia and strongly suggest a potential usefulness for 7,8-DHF or a TrkB agonist in treating schizophrenia-related cognitive impairments. (C) 2014 Elsevier Inc All rights reserved.