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 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.
The Neuroscience Center and Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84602, USA. neuroscience@byu.edu
Edwin D
ED
Lephart
Edwardo
E
Galindo
Li Hong
LH
Bu
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D015153:Blotting, Western; D001835:Body Weight / Q000187:drug effects*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D003345:Corticosterone / Q000097:blood; D004968:Estrogens, Non-Steroidal / Q000008:administration & dosage / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D007529:Isoflavones; D008297:Male; D019006:Neural Cell Adhesion Molecules / Q000187:drug effects / Q000378:metabolism; D017288:Pain Threshold / Q000187:drug effects*; D048789:Phytoestrogens; D028321:Plant Preparations; D051381:Rats; D020318:Rats, Long-Evans; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000378:metabolism; D030262:Soybean Proteins / Q000494:pharmacology; D013312:Stress, Physiological / Q000097:blood / Q000378:metabolism*; D016708:Synaptophysin / Q000187:drug effects / Q000378:metabolism
D004968:Estrogens, Non-Steroidal; D007529:Isoflavones; D019006:Neural Cell Adhesion Molecules; D048789:Phytoestrogens; D028321:Plant Preparations; D011965:Receptors, Glucocorticoid; D030262:Soybean Proteins; D016708:Synaptophysin; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone