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Visual spatial memory is enhanced in female rats (but inhibited in males) by dietary soy phytoestrogens.

Lund TD, West TW, Tian LY, Bu LH, Simmons DL, Setchell KD, Adlercreutz H, Lephart ED - BMC Neurosci (2001)

Bottom Line: In learning and memory tasks, requiring visual spatial memory (VSM), males exhibit superior performance to females (a difference attributed to the hormonal influence of estrogen).Results suggest that dietary phytoestrogens significantly sex-reversed the normal sexually dimorphic expression of VSM.These findings suggest that dietary soy derived phytoestrogens can influence learning and memory and alter the expression of proteins involved in neural protection and inflammation in rats.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Neuroscience Center Brigham Young University, Provo, Utah 84602, USA. Neuroscience@byu.edu

ABSTRACT

Background: In learning and memory tasks, requiring visual spatial memory (VSM), males exhibit superior performance to females (a difference attributed to the hormonal influence of estrogen). This study examined the influence of phytoestrogens (estrogen-like plant compounds) on VSM, utilizing radial arm-maze methods to examine varying aspects of memory. Additionally, brain phytoestrogen, calbindin (CALB), and cyclooxygenase-2 (COX-2) levels were determined.

Results: Female rats receiving lifelong exposure to a high-phytoestrogen containing diet (Phyto-600) acquired the maze faster than females fed a phytoestrogen-free diet (Phyto-free); in males the opposite diet effect was identified. In a separate experiment, at 80 days-of-age, animals fed the Phyto-600 diet lifelong either remained on the Phyto-600 or were changed to the Phyto-free diet until 120 days-of-age. Following the diet change Phyto-600 females outperformed females switched to the Phyto-free diet, while in males the opposite diet effect was identified.Furthermore, males fed the Phyto-600 diet had significantly higher phytoestrogen concentrations in a number of brain regions (frontal cortex, amygdala & cerebellum); in frontal cortex, expression of CALB (a neuroprotective calcium-binding protein) decreased while COX-2 (an inducible inflammatory factor prevalent in Alzheimer's disease) increased.

Conclusions: Results suggest that dietary phytoestrogens significantly sex-reversed the normal sexually dimorphic expression of VSM. Specifically, in tasks requiring the use of reference, but not working, memory, VSM was enhanced in females fed the Phyto-600 diet, whereas, in males VSM was inhibited by the same diet. These findings suggest that dietary soy derived phytoestrogens can influence learning and memory and alter the expression of proteins involved in neural protection and inflammation in rats.

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Dietary soy phytoestrogen's influence on a 4-arm (working and reference memory) task (baited/unbaited) in the radial arm maze. Long-Evans rats (males and females) received a life-long exposure to a high-phytoestrogen containing diet (Phyto-600, from conception to adulthood). In adulthood, one-half of the total number of male or female (random cycling) rats were either: 1) kept on the original high phytoestrogen diet (Phyto-600) or 2) changed to a phytoestrogen-free (Phyto-free) diet. Number of correct arm choices, made in the first four arm entries (Mean ± SEM; average of 3 trials). A correct choice was defined as an entry into a baited arm not yet visited in the trial. a. Phytoestrogen-600 females made significantly more correct choices than Phytoestrogen-free females a' and Phytoestrogen-600 males a" (p < 0.05) on trials 1–12. b. Phytoestrogen-600 females made significantly more correct choices than Phytoestrogen-600 males b' (p < 0.05) on trials 10–12. c. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-free females c' (p < 0.05) on trials 7–9. d. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-600 males d' (p < 0.05) on trials 10–12. e. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-600 males e" and Phytoestrogen-free females e' (p < 0.05) on trials 13–15.
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Figure 4: Dietary soy phytoestrogen's influence on a 4-arm (working and reference memory) task (baited/unbaited) in the radial arm maze. Long-Evans rats (males and females) received a life-long exposure to a high-phytoestrogen containing diet (Phyto-600, from conception to adulthood). In adulthood, one-half of the total number of male or female (random cycling) rats were either: 1) kept on the original high phytoestrogen diet (Phyto-600) or 2) changed to a phytoestrogen-free (Phyto-free) diet. Number of correct arm choices, made in the first four arm entries (Mean ± SEM; average of 3 trials). A correct choice was defined as an entry into a baited arm not yet visited in the trial. a. Phytoestrogen-600 females made significantly more correct choices than Phytoestrogen-free females a' and Phytoestrogen-600 males a" (p < 0.05) on trials 1–12. b. Phytoestrogen-600 females made significantly more correct choices than Phytoestrogen-600 males b' (p < 0.05) on trials 10–12. c. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-free females c' (p < 0.05) on trials 7–9. d. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-600 males d' (p < 0.05) on trials 10–12. e. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-600 males e" and Phytoestrogen-free females e' (p < 0.05) on trials 13–15.

Mentions: In contrast, on the 4-arm task, male VSM dominance appeared to be dependant upon diet (or after the diet switch). Multivariate analysis of variance resulted in a significant interaction of sex and diet (p < 0.05), see figure 4. The Phyto-600 diet improved performance in females while hampering performance in males. Further analysis via post hoc comparisons revealed that Phyto-600 females made significantly more correct arm choices than females switched to the Phyto-free diet during trial 10–12 (p < 0.05) and Phyto-600 males (on trials 10–12 and 13–15; p < 0.05). Males switched to the Phyto-free diet displayed significantly more correct arm choices than females switched to the Phyto-free diet (trials 7–9 and 13–15; p < 0.05) and lifelong fed Phyto-600 males (trials 10–12 and 13–15; p < 0.05). These results are shown in figure 4. Further multivariate statistical analysis and post hoc comparisons were used to identify differences in errors committed in the radial-arm maze. These data revealed a significant interaction of sex and diet on the incidence of reference errors during trials 10–12 and 13–15 (p < 0.05) but no significant differences in working or working/reference errors (p > 0.05). Pairwise comparisons revealed that lifelong fed Phyto-600 males committed significantly more reference memory errors than males switched to the Phyto-free diet and lifelong fed Phyto-600 females (p < 0.05) data presented in figure 5a. Additionally, in analyzing the amount of time required for subjects to enter the first 4 arms in a given trial it was found that a significant diet effect (independent of sex) was apparent where animals fed the Phyto-600 diet traveled through the maze significantly faster than animals fed the Phyto-free diet (trials 10–12; p < 0.05) figure 5b.


Visual spatial memory is enhanced in female rats (but inhibited in males) by dietary soy phytoestrogens.

Lund TD, West TW, Tian LY, Bu LH, Simmons DL, Setchell KD, Adlercreutz H, Lephart ED - BMC Neurosci (2001)

Dietary soy phytoestrogen's influence on a 4-arm (working and reference memory) task (baited/unbaited) in the radial arm maze. Long-Evans rats (males and females) received a life-long exposure to a high-phytoestrogen containing diet (Phyto-600, from conception to adulthood). In adulthood, one-half of the total number of male or female (random cycling) rats were either: 1) kept on the original high phytoestrogen diet (Phyto-600) or 2) changed to a phytoestrogen-free (Phyto-free) diet. Number of correct arm choices, made in the first four arm entries (Mean ± SEM; average of 3 trials). A correct choice was defined as an entry into a baited arm not yet visited in the trial. a. Phytoestrogen-600 females made significantly more correct choices than Phytoestrogen-free females a' and Phytoestrogen-600 males a" (p < 0.05) on trials 1–12. b. Phytoestrogen-600 females made significantly more correct choices than Phytoestrogen-600 males b' (p < 0.05) on trials 10–12. c. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-free females c' (p < 0.05) on trials 7–9. d. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-600 males d' (p < 0.05) on trials 10–12. e. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-600 males e" and Phytoestrogen-free females e' (p < 0.05) on trials 13–15.
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Related In: Results  -  Collection

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Figure 4: Dietary soy phytoestrogen's influence on a 4-arm (working and reference memory) task (baited/unbaited) in the radial arm maze. Long-Evans rats (males and females) received a life-long exposure to a high-phytoestrogen containing diet (Phyto-600, from conception to adulthood). In adulthood, one-half of the total number of male or female (random cycling) rats were either: 1) kept on the original high phytoestrogen diet (Phyto-600) or 2) changed to a phytoestrogen-free (Phyto-free) diet. Number of correct arm choices, made in the first four arm entries (Mean ± SEM; average of 3 trials). A correct choice was defined as an entry into a baited arm not yet visited in the trial. a. Phytoestrogen-600 females made significantly more correct choices than Phytoestrogen-free females a' and Phytoestrogen-600 males a" (p < 0.05) on trials 1–12. b. Phytoestrogen-600 females made significantly more correct choices than Phytoestrogen-600 males b' (p < 0.05) on trials 10–12. c. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-free females c' (p < 0.05) on trials 7–9. d. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-600 males d' (p < 0.05) on trials 10–12. e. Phytoestrogen-free males made significantly more correct choices than Phytoestrogen-600 males e" and Phytoestrogen-free females e' (p < 0.05) on trials 13–15.
Mentions: In contrast, on the 4-arm task, male VSM dominance appeared to be dependant upon diet (or after the diet switch). Multivariate analysis of variance resulted in a significant interaction of sex and diet (p < 0.05), see figure 4. The Phyto-600 diet improved performance in females while hampering performance in males. Further analysis via post hoc comparisons revealed that Phyto-600 females made significantly more correct arm choices than females switched to the Phyto-free diet during trial 10–12 (p < 0.05) and Phyto-600 males (on trials 10–12 and 13–15; p < 0.05). Males switched to the Phyto-free diet displayed significantly more correct arm choices than females switched to the Phyto-free diet (trials 7–9 and 13–15; p < 0.05) and lifelong fed Phyto-600 males (trials 10–12 and 13–15; p < 0.05). These results are shown in figure 4. Further multivariate statistical analysis and post hoc comparisons were used to identify differences in errors committed in the radial-arm maze. These data revealed a significant interaction of sex and diet on the incidence of reference errors during trials 10–12 and 13–15 (p < 0.05) but no significant differences in working or working/reference errors (p > 0.05). Pairwise comparisons revealed that lifelong fed Phyto-600 males committed significantly more reference memory errors than males switched to the Phyto-free diet and lifelong fed Phyto-600 females (p < 0.05) data presented in figure 5a. Additionally, in analyzing the amount of time required for subjects to enter the first 4 arms in a given trial it was found that a significant diet effect (independent of sex) was apparent where animals fed the Phyto-600 diet traveled through the maze significantly faster than animals fed the Phyto-free diet (trials 10–12; p < 0.05) figure 5b.

Bottom Line: In learning and memory tasks, requiring visual spatial memory (VSM), males exhibit superior performance to females (a difference attributed to the hormonal influence of estrogen).Results suggest that dietary phytoestrogens significantly sex-reversed the normal sexually dimorphic expression of VSM.These findings suggest that dietary soy derived phytoestrogens can influence learning and memory and alter the expression of proteins involved in neural protection and inflammation in rats.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Neuroscience Center Brigham Young University, Provo, Utah 84602, USA. Neuroscience@byu.edu

ABSTRACT

Background: In learning and memory tasks, requiring visual spatial memory (VSM), males exhibit superior performance to females (a difference attributed to the hormonal influence of estrogen). This study examined the influence of phytoestrogens (estrogen-like plant compounds) on VSM, utilizing radial arm-maze methods to examine varying aspects of memory. Additionally, brain phytoestrogen, calbindin (CALB), and cyclooxygenase-2 (COX-2) levels were determined.

Results: Female rats receiving lifelong exposure to a high-phytoestrogen containing diet (Phyto-600) acquired the maze faster than females fed a phytoestrogen-free diet (Phyto-free); in males the opposite diet effect was identified. In a separate experiment, at 80 days-of-age, animals fed the Phyto-600 diet lifelong either remained on the Phyto-600 or were changed to the Phyto-free diet until 120 days-of-age. Following the diet change Phyto-600 females outperformed females switched to the Phyto-free diet, while in males the opposite diet effect was identified.Furthermore, males fed the Phyto-600 diet had significantly higher phytoestrogen concentrations in a number of brain regions (frontal cortex, amygdala & cerebellum); in frontal cortex, expression of CALB (a neuroprotective calcium-binding protein) decreased while COX-2 (an inducible inflammatory factor prevalent in Alzheimer's disease) increased.

Conclusions: Results suggest that dietary phytoestrogens significantly sex-reversed the normal sexually dimorphic expression of VSM. Specifically, in tasks requiring the use of reference, but not working, memory, VSM was enhanced in females fed the Phyto-600 diet, whereas, in males VSM was inhibited by the same diet. These findings suggest that dietary soy derived phytoestrogens can influence learning and memory and alter the expression of proteins involved in neural protection and inflammation in rats.

Show MeSH
Related in: MedlinePlus