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 3 mg coumestrol (CM1, CM3), 1 mg genistein (GS1), 1 mg estradiol (E 2), 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 E 2-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 E 2-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 E 2-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 E 2-treated rats. Behavioral tests were carried out after implantation of E 2-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, E 2 or male groups were lower than that in the control female group. These results suggest that a single neonatal injection of 3 mg coumestrol was effective in suppressing the functions of ovulation-inducing mechanisms and the induction of lordosis, but 1 mg coumestrol was effective in only the estrous cycle of female rats.
|Number of pages||6|
|Journal||Brain Research Bulletin|
|Publication status||Published - 2005 Jan 15|
- Estrous cycle
- Sex differentiation
ASJC Scopus subject areas