The effects of an herbal medicine Bu-Wang-San on learning and memory of ovariectomized female rat
Introduction
Menopause marks the end of reproductive capacity of women and results from the permanent cessation of ovarian function. Natural or surgical menopause is confirmed by absence of menstrual periods for 12 consecutive months, excluding other obvious pathologic or physiologic causes (Notelovitz, 1989). Some symptoms such as hot flashes, tiredness, irritability, insomnia, palpitations, memory or concentration difficulties, and mood swings or depression begin in the peri-menopause and increase as women progress through the menopause (Hardy and Kuh, 2002). Many studies have shown that learning and memory may be negatively affected altered by the loss of estrogen after menopause (Sherwin, 1988). These changes can be ameliorated by estrogen replacement therapy (ERT) (Ditkoff et al., 1991, Sherwin, 1994, Kimura, 1995). As a neuroprotective and neurotrophic factor, estrogen (E2) helps maintain memory and cognition (Sughrue and Merchenthaler, 2000, Wise et al., 2001), decreases the risk and delays the onset of neurological disorders, e.g. Alzheimer's disease (AD). Indeed, estrogen has been shown to increase cerebral blood flow, to act as an anti-inflammatory agent and enhance neural synapse activity (Toran-Allerand et al., 1999, Roof and Hall, 2000). Numerous studies indicate that estrogen is essential for optimal brain function (Toran-Allerand et al., 1999, Roof and Hall, 2000, Sughrue and Merchenthaler, 2000, Wise and Dubal, 2000, Wise et al., 2001). However, the above-mentioned health benefits of ERT were often overshadowed by the serious side-effects of estrogen use in menopaused women. Specifically, long-term use of estrogen in postmenopausal women may lead to the increased risk of endometrial and breast cancer (Hammond, 1994, Grady et al., 1995, Anonymous, 1997). Accordingly, there has been a growing interest in alternative therapies. One alternative employs phytoestrogens, the other alternative employs Chinese herbal medicine.
Phytoestrogens as nonsteroidal plant compounds that are structurally or functionally similar to estrogens and may have similar beneficial effects. These substances have a 2-phenylnaphthaline-type chemical structure and bind to estrogen receptors in vitro and in vivo (Welshons et al., 1987, Lephart et al., 1996, Pan et al., 1999a, Pan et al., 1999b, Patisaul et al., 1999, Jacob et al., 2001, Kim et al., 2001). Specifically, dietary supplementation with isoflavones or lignans had an estrogenic effect, as shown by the maturation of vaginal epithelium on cytology (Wilcox et al., 1990).
Chinese herbal medicine has been used for thousands of years in China and other Asian countries. In clinical practice of traditional Chinese medicine (TCM), it is common to modify original formula by adding or substituting herbs in accordance with a patient's condition to enhance the efficacy of the original formula. Most of the regular use of traditional Chinese medicine is not associated with serious side effects. Specific formula of traditional Chinese herbal medicines has been reported to be effective against cognitive disorder (Junping et al., 2005, Hai-Fa et al., 2006, Young-Ju et al., 2007). However, there was little information available in literature about whether herbal medicines with neuroprotective effect could affect postmenopausal cognitive disorder. Bu-Wang-San (, BWS), a classical Chinese herbal formula, has been used to treat the postmenopausal cognitive disorder for years in clinic. The mechanism as to how BWS protects learning and memory has not been studied. Pyramidal neurons in the hippocampal CA1 are particularly vulnerable from impairment. We have used ovariectomized rat as the estrogen-depleted, postmenopausal model (Kalu, 1991) to examine the effect of BWS on postmenopausal cognitive disorder. In addition, we have studied the effect of BWS, for the first time, on the change of ultrastructure of CA1 region and spinal synapse density with electron microscope.
Section snippets
Composition and preparation of Bu-Wang-San
BWS consists of four medicinal compositions as shown in Table 1. All of these herbs were purchased from Jian-lian Company of Traditional Crude Drugs (Jinan, China), and carefully authenticated by Dr. Li-Hong Zhong, Pharmaceutical Preparation Section, Qilu Hospital Affiliated to Shandong University, Jinan, China. Voucher specimens (numbers were listed in Table 1) were deposited at the Herbarium of Shandong University (Jinan, China). After drying, these herbs were mixed in proportion. Forty-eight
Spatial acquisition
In the spatial acquisition phase of testing, the effect of testing was significant for both swim time and swim distance, and there was a significant treatment by block interaction. On this trial, OVX groups had significantly longer swim time than Sham and BWS groups, which was confirmed by conducting a separated repeated measure ANOVA for each group. Animals in Sham and BWS groups did achieve the shorter swim time at the end of the whole trial. Comparison of the three groups at the end of the
Discussion
The present study clearly showed a neuroprotective role of BWS in ovariectomized rat in association with an increase of CA1 dendritic spinal synapse density. It has been recognized that OVX for 6 days in young animals results in synaptic loss between noradrenergic terminals and gonadotropin hormone releasing hormone (GnRH) neurons, long-term OVX, hypothesized to protect against neuroendocrine aging, failed to guard against any age-related changes (Miller et al., 1998). Interactions of the
Disclosure statement
All surgical procedures and protocols used were in accordance with the Guidelines for Ethical Care of Experimental Animals, which was approved by the Shandong University Animal Care and Use Committee. It is the first report about the effect of Bu-Wang-San on study and memory of menopause. Each author has read and approved the submitted manuscript.
Acknowledgment
This work was supported by the Health Department of Shandong Province, Jinan, China.
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