Correlations between cognitive impairment and brain-derived neurotrophic factor expression in the hippocampus of post-stroke depression rats

The aim of this study was to investigate the correlation between brain-derived neurotrophic factor (BDNF) expression and cognitive impairment in post-stroke depression (PSD) rats and to explore the mechanism(s) involved in the process of cognitive impairment. A rat model of focal cerebral ischemia was established by occluding the middle cerebral artery (MCA). Rats were subjected to isolation-housing combined with chronic unexpected mild stress (CUMS) to establish a PSD rat model. The learning and memory abilities of the PSD rat model were evaluated by passive avoidance tests. Real-time PCR and immunohistochemical methods were used to detect changes in BDNF mRNA and protein expression in the hippocampus. Passive avoidance defects were revealed in the PSD and depression groups. Passive avoidance defects were more evident in the PSD group compared with the depression group and the difference was statistically significant (P<0.05). BDNF expression in the hippocampus was significantly lower in the PSD and depression groups compared with that in the normal control group (P<0.01). No significant difference in BDNF expression was identified between the normal control and stroke groups (P>0.05) or between the PSD and the depression groups (P>0.05). The decrease in BDNF expression in the hippocampus of PSD rats may aggravate cognitive impairment, however, the degree of cognitive impairment cannot be reflected by the expression levels of BDNF in the hippocampus.