Objective: To study the effect of needling method for regulating mental activity and tonifying the kidney on expression of aroma-tizase cytochrome P450 （P450 arom） in climacteric rats. Methods: Hybridization in situ and computer-aided image analysis were adopted. Results: Expression of P450 arom mRNA in cells of sinusoidal follicles and the mature corpu luteum of the ovary decreased and in the interstitial adenocytes basically kept normal in climacteric rats. After acupuncture

expression of P450 arom mRNA in these parts particularly in the sinusoidal follicle and the mature corpus luteum were significantly strengthened. Conclusion: Promotion of expression of P450 arom mRNA in the ovary is beneficial to increase of the content of rate-limiting enzyme for synthesis of estrin. which is possibly one of molecular mechanisms of the needling method for regulating mental activity and tonifying the kidney increasing estrin level in the body.