Effect of oleuropein on cognitive deficits and changes in hippocampal brain-derived neurotrophic factor and cytokine expression in a rat model of post-traumatic stress disorder

Abstract

Post-traumatic stress disorder (PTSD) is a condition that develops after an individual has experienced a major trauma. This psychopathological response to traumatic stressors induces learning and memory deficits in rats. Oleuropein (OLE), a major compound in olive leaves, has been reported to possess several pharmacological properties, including anti-cancer, anti-diabetic, anti-atherosclerotic and neuroprotective activities. However, the cognitive effects of OLE and its mechanism of action have remained unclear in PTSD. In this study, we examined whether OLE improved spatial cognitive impairment induced in rats following single prolonged stress (SPS), an animal model of PTSD. Male rats were treated intraperitoneally (i.p.) with vehicle or various doses of OLE for 14 consecutive days after the SPS procedure. The SPS procedure resulted in cognitive impairment in the object recognition task and the Morris water maze test, which was reversed by OLE (100 mg/kg, i.p). Additionally, as assessed by immunohistochemistry and reverse transcription-polymerase chain reaction analysis, the administration of OLE significantly alleviated memory-associated decreases in the levels of brain-derived neurotrophic factor and cAMP response element-binding protein and mRNA in the hippocampus. Together, these findings suggest that OLE attenuated SPS-induced cognitive impairment significantly by inhibiting the expression of pro-inflammatory mediators in the rat brain. Thus, OLE reversed several behavioral impairments triggered by the traumatic stress of SPS and might be a potential useful therapeutic intervention for PTSD.