| With the increased life expectancy, women spend now more than one third of their life in menopause. The mean age at which women begin the peri-menopausal transition shifted to an earlier age since the life pace accelerating and greater work pressure. Furthermore, women with surgical menopause increased significantly. Therefore, health condition of menopausal women attracted more attention. Although hormone replacement therapy is still as the main stream of the menopausal clinic, the acupuncture, as a safe and effective therapy, has been established as a therapy in reproductive medicine in the West. An understanding of the underlying mechanisms of acupuncture is necessary for a more extensive use.Our previous study indicated that ovariectomy in rats mimic the hormonal changes that occur in women after menopause and thus resulted in the dysfunction of hypothalamus-pituitary-ovary in ovariectomized rats. EA enhanced extragonadal aromatization in both subcutaneous abdominal adipose and the liver tissues to promote the blood concentrations of estrogen in the ovariectomized rats. Additionally, electroacupuncture (EA) stimulated hypothalamic aromatization and thus increase the production of estrogen in local hypothalamus. So EA enhanced the body estrogen level by stimulating the extragonadal aromatization in ovariectomized rats and normalized the dysfunction of HPOA. Since the estrogen action requires that estrogen bind to estrogen receptors, the estrogen receptor should be considered in EA treatment. In present study, we first examined whether the ovariectomy model can mimic the symptoms and signs of the menopausal women including the hormone changes. Then we detected the mechanisms of EA in uterus and in hypothalamus.Methods:(1) Female SD rats were randomly divided into Sham, Sham+EA, OVX and OVX+EA. Guanyuan, Zhongji, Zigong and Sanyinjiao were selected to stimulate. The effects of ovariectomy and EA on body weight, tissue wet weight and behaviors were observed. (2) Female SD rats were randomly divided into Sham, OVX and OVX+EA. Vaginal epithelia, blood estrogen level, uterine morphology and estrogen receptors were examined in this experiment. (3) Rats were divided and treated as above. Effects of EA on estrogen receptor alpha (ERa) and beta (ER?) mRNA and protein expression in the hypothalamus of ovariectomized (OVX) rats were detected. Gonadotropin-releasing hormone (GnRH) release and GnRH mRNA level in hypothalamic medial preoptic area were evaluated. The GnRH receptor in hypothalamus was also observed. (4) Experiment 1:ovariectomized rats were divided into two groups randomly as follows:Group 1 for push-pull perfusion, and Group 2 for microinjection. The push-pull perfusate collected from the hypothalamic medial preoptic area (MPO) of rats in the OVX+EA group was called EA-push-pull perfusate (EA-Perfusate, EA-P), and that collected from the MPO of rats in the OVX group was named OVX-push-pull perfusate (OVX-Perfusate, OVX-P). The contents of neuronal active substances were examined in push-pull perfusate. Ovariectomized rats in Group 2 received a continuous microinjection of 1?l of EA-P (IEAP, n=9), OVX-P (IOVXP, n=9) and aCSF (IaCSF, n=9) respectively. Vaginal epithelia, blood estrogen level and uterine morphology were examined. Experiment 2:Ovariectomized rats underwent electrical lesion of the MPO and sham lesion. Half MPO-lesioned ovariectomized rats and sham MPO-lesioned ovariectomized rats received EA treatment. Another half MPO-lesioned ovariectomized rats and sham MPO-lesioned ovariectomized rats were as EA control. Vaginal epithelia, blood estrogen level and uterine morphology were observed.Results:(1) Ovariectomized rats mimic most of symptoms and signs of menopausal women, such as hot flash, weight gain fat, the body-fat distribution and a loss of memory and learning ability.EA treatment can effectively relieve those signs. Those results indicated that ovariectomized rats is acceptable animal model to explore the mechanisms of EA on menopausal syndromes.(2) The ratio of uterine weight, the total number of endometrial glands in per section, the thickness of endometrium and the myometrium increased significantly after EA treatment in ovariectomized rats. EA may achieve those effects by modulating the expression of estrogen receptors?,?and enhancing the level of blood E2. (3) Elevated mRNA and protein expression of ERa and ERP in the preoptic area-anterior hypothalamus (POA-AH) were restrained following EA treatment in OVX rats while no changes of ERs were detected in the medial basal hypothalamus-median eminence (MBH-ME). The elevated expression of GnRH receptor in POA-AH was decreased after EA treatment in ovariectomized rats. EA treatment also inhibited GnRH release and GnRH mRNA levels in OVX rats. These results provide novel evidence that EA treatment down regulates the expression of ERs and GnRHR in POA-AH. thus enhancing the stability of GnRH neurons and restoring the response of GnRH neurons to estrogen depression, and partially resetting the negative feedback of estrogen to hypothalamus-pituitary-ovary axis (HPOA) in OVX rats, and may be a critical mechanism for EA on female reproductive disorders.(4) In this experiment, vaginal smears, circulating estrogen concentration and uterine morphological evaluation together, are used to be reliable indices of the effects of EA on HPOA dysfunction. EA might influence the collaboration of inhibitory and stimulating factors on GnRH neurons in the MPO to normalize the increased release of GnRH, thereby normalizing female reproductive dysfunction due to ovariectomy. A transfer of the MPO-perfusate from a donor ovariectomized rat that received EA treatment to the MPO of a recipient ovariectomized rat, similar EA effects could be induced in the recipient. EA treatment was applied to MPO-lesioned ovariectomized rats and the MPO lesion mostly blocked the effects of EA treatment. Those are the first to identify the MPO as a crucial site for EA treatment in normalizing reproductive dysfunction from ovariectomy.Conclusion:Ovariectomized rats can mostly mimic the signs and sypotoms of menopausal women including the hormone changes. It is a reliable animal model for female reproductive disorder. (2) EA improved the uterine morphology by modulating the expression of uterine ERs and increasing the blood level of E2. (3) ERs and GnRH in POA-AH may involve the mechanism for EA on GnRH neurons in ovariectomized rats. (4) The neuronal active substances in the MPO involved the effects of EA. The MPO might be a crucial site for EA treatment in normalizing reproductive dysfunction from ovariectomy. |
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