Objective To observe the effect of electroacupuncture (EA) on the expression of glucocorticoid (GC) mRNA and GC in the hippocampus

hypothalamus and pituitary in depression rats so as to study its mechanism underlying EA-resisting depression. Methods Seventy SD rats were randomized into normal control

model

Fluoxetine (Flu)

constraint-stress

EA

RU 486 (an antagonist of GC) and EA+RU 486 groups (n=10/group).Chronic depression model was established by lonely raising and chronic unpredictable mild stress for 21 days.EA (2 Hz

0.6 mA) was applied to "Baihui" (GV 20) and "Yintang" (EX-HN 3) for 20 min

once daily for 21 days.Subcutaneous injection of RU 486 (20 mg/kg) was given to the rats from the 14 th day on and continuously for 7 days in order to block the negative feedback reflex of hypothalamus-pituitary-adrenal (HPA) axis.Cortisol (CORT) content of the adrenal gland tissue was detected by radioimmunassay.The expression of GC receptor (GR)mRNA in the hippocampus

hypothalamus and pituitary tissues was determined by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). Results Compared with the normal control group

adrenal CORT content of model group was increased significantly ( P<0.05 )

and in comparison with model group

adrenal CORT level of EA group decreased evidently ( P<0.05 ).Comparison between the RU 486 and EA+RU 486 groups showed that the adrenal CORT content

and hippocampal GR mRNA expression level of the latter were remarkably lower than those of the former ( P<0.05 ). Compared with the normal control group

the expression level of GR mRNA of the hipppocampal and pituitary tissues in the model

constraint-stress

and RU 486 groups

and those of the hypothalamus in the constraint-stress and RU 486 groups were down-regulated significantly ( P<0.05 ).In comparison with the constraint-stress group

hippocampal

hypothalamic and pituitary GR mRNA expression level in the EA group were upregulated considerably ( P<0.05 ).No significant differences were found among model

Flu

constraint-stress

RU 486 and EA+RU 486 groups in the ardenal CORT contents

and hippocampal

hypothalamic and pituitary GR mRNA expression levels ( P>0.05 ). Conclusion EA can effectively down-regulate adrenal CORT content and hippocampal GR mRNA expression and normalize the function of HPA axis negative feed reflex in the depression rats

which may contribute to its effect in relieving depression.