Ovariectomy impairs spatial memory: prevention and reversal by a soy isoflavone diet

Abstract

Since a previous study has shown that ovariectomy impairs spatial memory, we, herein, investigate the influence of pre- and post-treatment with a soy diet on the effects elicited by ovariectomy on spatial memory. In the pre-treatment, 20-day-old female Wistar rats were first fed for 60 days on a standard diet with casein (control) or a soy diet. At 80 days of age, the animals were assigned to one of the following groups: sham (submitted to surgery without removal of ovaries) and ovariectomized. One week after surgery, the rats were submitted to behavioral testing. In the post-treatment, 80-day-old female rats were assigned to one of the following groups: sham and ovariectomized. One week after surgery, animals were fed for 30 days with the same diet described above. Then, rats were submitted to water maze testing. Pre-treatment for two months before ovariectomy with the soy diet effectively prevented the increase in latency in finding the platform on the fifth day of training in the ovariectomized group. Ovariectomized rats subjected to soy diet post-treatment reversed the increase in latency to find the platform in the ovariectomized group on the fifth day of training and, the decrease in the time spent in target quadrant, the increase in the time spent in opposite quadrant and the latency to cross the platform location. Results show that both pre- and post-treatment protected against the impairment of memory, caused by ovariectomy. Post-treatment reversed various parameters of memory reference, indicating that post-treatment was more efficient than pre-treatment. Based on these findings, we suggest that soy diet (rich in isoflavones) may represent a novel therapeutic strategy to prevent or to treat cognitive symptoms found in some menopausal women.

Acute genistein treatment mimics the effects of estradiol by enhancing place learning and impairing response learning in young adult female rats

“…A single high dose of genistein (40 mg/kg) enhances memory in the swim task (Alonso et al, 2010), as does chronic genistein treatment (Xu et al, 2007, Huang and Zhang, 2010). The mnemonic effects of extended exposure to mixed soy isoflavones have been more frequently described, with enhancements reported in the radial arm maze (Pan et al, 2000, Lund et al, 2001), object placement (Luine et al, 2006), and swim task (Monteiro et al, 2008, Lee et al, 2009, Pan et al, 2010). While the current study used only a single genistein dosage, other findings (Huang and Zhang, 2010) suggest that genistein may demonstrate a similar inverted-U pattern of spatial memory modulation, as rats chronically treated with low (15 mg/kg) but not high (30 mg/kg) doses of genistein showed memory enhancements in the swim task.…”

“…Studies examining the effects of isoflavones on cognition are particularly sparse and document mixed results in humans (Lee et al, 2005, Zhao and Brinton, 2007). In experiments using laboratory rodents, isoflavones act like estradiol, enhancing performance for some memory tasks but impairing performance on others (Pan et al, 2000, Lund et al 2001, Luine et al 2006, Monteiro et al 2008, Neese et al, 2010, Neese et al 2012). Most research has focused on chronic isoflavone exposure, with few experiments examining the acute actions of isolated soy compounds commonly found in botanical supplements.…”

Sex steroid hormones matter for learning and memory: estrogenic regulation of hippocampal function in male and female rodents

“…This approach eliminates the primary source of circulating estrogens and progestins, so it is important to realize that levels of several hormones will drop as a result. Ovariectomy itself impairs some forms of memory including spatial working memory in the radial arm maze, spatial reference memory in the Morris water maze, object recognition memory, and memory in a two-way active avoidance task (Singh et al 1994;Daniel et al 1999;Wallace et al 2006;Gibbs and Johnson 2008;Monteiro et al 2008). However, other studies report no effect or a memory-enhancing effect of ovariectomy in these tasks (Singh et al 1994;Daniel et al 1999;Bimonte-Nelson et al 2003).…”

The effects of dietary treatment with S-equol on learning and memory processes in middle-aged ovariectomized rats

“…In addition to isoflavone composition, methodological differences in age at the time of treatment, previous HRT use, cognitive domain tested, and length of treatment likely contribute to the conflicting findings among published reports (see also Sumien et al, 2013). In contrast, treatments with mixed isoflavone content to young and aging ovariectomized (OVX) rats enhance performance on a variety of spatial learning and memory tasks (Lee et al, 2009; Monteiro et al, 2008; Pan et al, 2000, Pan et al, 2010; Sarkaki et al, 2008, 2009; Zhao et al, 2011). These limited results corroborate the oft-reported findings that estrogen-based treatments to OVX rats improve performance on tasks that tap the hippocampal memory system in aging rodents (see Acosta et al, 2013; Frick, 2009; Hammond and Gibbs, 2011, but see also Chisholm and Juraska, 2013).…”