Suppressive effect of neonatal treatment with a phytoestrogen, coumestrol, on lordosis and estrous cycle in female rats

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• 作者：Kouki ; Tom ; Okamoto ; Miho ; Wada ; Shizuko ; Kishitake ; Miki ; Yamanouchi ; Korehito
• 关键词：Phytoestrogen ; Coumestrol ; Sex differentiation ; Brain ; Lordosis ; Estrous cycle ; Rat
• 刊名：Brain Research Bulletin
• 出版年：2005
• 期刊代码：9_03619230
• 类别：neu
• 出版时间：January 15, 2005
• 卷：64
• 期：5
• 页码：449-454
• 文件大小：179 K

摘要

The neural control systems for the ovulatory cycle and lordosis behavior are sexually differentiated by estrogen during the perinatal period in rats. In the present study, the effects of a single neonatal injection with the phytoestrogen, coumestrol, on female reproductive functions were investigated. Female rats were injected subcutaneously with 1 or 3mg coumestrol (CM1, CM3), 1mg genistein (GS1), 1mg estradiol (E₂), or oil at day 5 after birth (birth day=day 1) and an estrous cycle check and lordosis behavior test were performed. As a result, vaginal opening was advanced in CM1-, CM3- or E₂-treated females. A vaginal smear check indicated that oil- or GS1-treated females showed a constant 4- or 5-day estrous cycle, whereas CM1-, CM3- or E₂-treated rats showed a persistent or prolonged estrus. Ovariectomy was performed in all females at 60 days of age. The ovary weights in the CM1-, CM3- or E₂-treated groups were lower than those in the oil- and GS1-treated groups and no corpora lutea were found in any rats of these three groups, except for two E₂-treated rats. Behavioral tests were carried out after implantation of E₂-tubes. All rats in the CM1-, GS1-treated groups showed a high lordosis quotient (LQ), being comparable to that in the oil-treated females. On the other hand, LQs in the CM3, E₂ or male groups were lower than that in the control female group. These results suggest that a single neonatal injection of 3mg coumestrol was effective in suppressing the functions of ovulation-inducing mechanisms and the induction of lordosis, but 1mg coumestrol was effective in only the estrous cycle of female rats.