Anxiolytic-like effect of phytoestrogen genistein in rats with long-term absence of ovarian hormones in the black and white model

Postmenopause is mainly characterized by a reduction of ovarian hormones, which is accompanied by a major incidence of physical disorders and mood swings. Clinical and experimental evidence suggest that phytoestrogens could be used to ameliorate these alterations associated with menopause. However, the phytoestrogen effects on anxiety in rats with long-term absence of ovarian hormones, is unknown. Consequently, in the present study the authors compared the anxiolytic-like effect of phytoestrogen genistein (0.25, 0.5 y 1.0 mg/kg, i.p.) in Wistar rats with 12-weeks postovariectomy in the black and white model and in the open field test, and it was compared with diazepam (1.0 mg/kg, i.p.). In the black and white model, genistein (0.5 y 1.0 mg/kg) and diazepam reduced the latency to enter and increased the time spent into the white compartment; also, significantly increased frequency and time spent in exploration toward white compartment was seen, as compared with the control group (p < 0.05). In the open field test, genistein and diazepam increased grooming and rearing, without significant changes in locomotor activity, as compared with the control group. In conclusion, phytoestrogen genistein produces an anxiolytic-like effect in Wistar rats with long-term absence of ovarian hormones in the black and white model, supporting the hypotheses that phytoestrogens could be used to ameliorate anxiety associated with menopause. (c) 2009 Elsevier Inc. All rights reserved.