Stress (hypothalamic–pituitary–adrenal axis) and pain response in male rats exposed lifelong to high vs. low phytoestrogen diets

Estrogens exhibit complex but beneficial effects on brain structure, function and behavior. Soy-derived dietary phytoestrogens protect against hormone-dependent and age-related diseases, due to their estrogen-like hormonal actions. However, the effects of phytoestrogens on brain and behavior are rel...

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Bibliographic Details
Published in:Neuroscience letters 2003-05, Vol.342 (1), p.65-68
Main Authors: Lephart, Edwin D., Galindo, Edwardo, Bu, Li Hong
Format: Article
Language:English
Subjects:
Adrenocorticotrophin
Adrenocorticotropic Hormone - blood
Animals
Biological and medical sciences
Blotting, Western
Body Weight - drug effects
Brain
Brain - drug effects
Brain - metabolism
Corticosterone - blood
Estrogens, Non-Steroidal - administration & dosage
Estrogens, Non-Steroidal - pharmacology
Feeding. Feeding behavior
Fundamental and applied biological sciences. Psychology
Hippocampus - drug effects
Hippocampus - metabolism
Isoflavones
Male
Neural cell adhesion molecules
Neural Cell Adhesion Molecules - drug effects
Neural Cell Adhesion Molecules - metabolism
Pain
Pain Threshold - drug effects
Phytoestrogens
Plant Preparations
Rat
Rats
Rats, Long-Evans
Receptors, Glucocorticoid - drug effects
Receptors, Glucocorticoid - metabolism
Soy
Soybean Proteins - pharmacology
Stress
Stress, Physiological - blood
Stress, Physiological - metabolism
Synaptophysin
Synaptophysin - drug effects
Synaptophysin - metabolism
Vertebrates: anatomy and physiology, studies on body, several organs or systems
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Summary:Estrogens exhibit complex but beneficial effects on brain structure, function and behavior. Soy-derived dietary phytoestrogens protect against hormone-dependent and age-related diseases, due to their estrogen-like hormonal actions. However, the effects of phytoestrogens on brain and behavior are relatively unknown. This study examined the influence of exposing male Long–Evans rats (lifelong) to either a phytoestrogen-rich (Phyto-600) or a phytoestrogen-free (Phyto-free) diet on body weights, behavioral pain thresholds, the hypothalamic–pituitary–adrenal (HPA) hormonal stress response, hippocampal glucocorticoid receptor and brain neural cell adhesion molecules (NCAM) and synaptophysin levels using standard behavioral and biochemical techniques. Body weights were significantly decreased in Phyto-600 fed animals compared to Phyto-free values. There were no significant changes in behavioral pain thresholds, circulating corticosterone concentrations (after acute immobilization stress) or NCAM and synaptophysin levels in various brain regions by the diet treatments. However, Phyto-600 fed males displayed significantly higher plasma adrenocorticotrophin (ACTH) (post-stress) and hippocampal glucocorticoid receptor levels vs. Phyto-free values. These data suggest that (1) body weights are significantly reduced by soy-derived phytoestrogens, (2) behavioral pain thresholds (via heat stimuli) are not influenced by dietary phytoestrogens, but (3) these estrogenic molecules in the hippocampus enhance glucocorticoid receptor abundance and alter the negative feedback of stress hormones towards a female-like pattern of higher ACTH release after activation of the HPA stress axis. This study is the first to show that lifelong consumption of dietary phytoestrogens alters the HPA stress response in male rats.
ISSN:0304-3940
1872-7972
DOI:10.1016/S0304-3940(03)00262-3