title: Endocrine and behavioral modifications in aging male rats.
abstract: Endocrine and behavioral effects of age and aging have been studied in 4 groups of Sprague-Dawley male rats (2, 6, 12, 24 months old). Plasma testosterone decreases after 6 months of age, plasma estradiol decreases from 2 to 6 months, then it increases with age and decreases again with aging (from 12 to 24 months). Aromatization of testosterone in brain tissue is similar in 2-, 12- and 24-month-old rats, but at 6 months a significant increase is observed. Testosterone biosynthesized in the gonad from dehydroepiandrosterone increases from 2 to 6 months, then it decreases, while the other metabolites of dehydroepiandrosterone show an increment with age. Corticosterone and 17 alpha-hydroxyprogesterone biosynthesized in the adrenal decrease with aging. Explorative and locomotor activity decreases with age and aging, while emotionality decreases from 2 to 12 months, but it increases with aging. These results indicate that endocrine equilibrium is remarkably altered by aging process showing a decrease of plasma sexual hormones and of gonadal activity. The decrement of aromatization of testosterone in the brain, which occurs between 6 and 12 months, is correlated with the decrement of plasma testosterone. It could be hypothesized that the hormones of the brain-pituitary-gonad axis are involved in the control of explorative behavior or that both hormonal and behavioral parameters are controlled by a common factor.
mesh_terms: D000311:Adrenal Glands / Q000378:metabolism; D000375:Aging; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001921:Brain / Q000378:metabolism; D003345:Corticosterone / Q000097:blood; D003687:Dehydroepiandrosterone / Q000378:metabolism; D004958:Estradiol / Q000097:blood; D012739:Gonadal Steroid Hormones / Q000502:physiology*; D008297:Male; D011374:Progesterone / Q000378:metabolism; D051381:Rats; D013737:Testis / Q000378:metabolism; D013739:Testosterone / Q000097:blood / Q000378:metabolism
chemical_list: D012739:Gonadal Steroid Hormones; D013739:Testosterone; D003687:Dehydroepiandrosterone; D011374:Progesterone; D004958:Estradiol; D003345:Corticosterone