Objective    To explore the effect of depression on the expression of brain-derived neurotrophic factor (BDNF) in the cerebral cortex

hippocampus and cerebrospinal fluid in order to investigate the relationship between BDNF and the occurrence of depression.     Methods    The depression model in rats was established with chronic unpredictable stress. The behaviors in Open-Field testing were observed through forced swimming. The expression of BDNF   in above-mentioned tissues was examined by immunohistochemical method and ELISA.     Results    Compa

red with normal control

the number of BDNF positive cells in the hippocampus and cerebral cortex in depressed rats was decreased markedly. The level of BDNF in the cerebral-spinal fluid

hippocampus and cerebral cortex in normal mice was (6.87±2.44)ng/ml

(11.75±3.60)ng/g and (4.31±1.37)ng/g respectively; and they were markedly higher than those of depressed rats [(4.23±1.54)ng/ml

(8.56±2.45)ng/g and (3.06±0.67)ng/g

P

<

0.01

]

.     Conclusion    BDNF levels are obviously decreased in the depressed rats

indicating it may be involved in the occurrence of depression.