Hormonal influences on the estradiol-induced and age-related increases of pituitary dopamine in C57BL/6J mice. Effects of gonadal steroids, gender, and prolactin.
Estradiol (E2) produces many-fold increases in the dopamine (DA) content of the anterior pituitary and also plays a role in the age-related increase in pituitary DA in female C57BL/6J mice. These studies address the following questions: (1) What are the time and dose characteristics of the E2-induced increase in pituitary DA and can other gonadal steroids - such as progesterone (P) and 5 alpha-dihydrotestosterone - also influence pituitary DA? (2) Is the age-related increase in pituitary DA due entirely to an increase in the E2:P ratio seen in aging female mice, or can extra-ovarian factors also play a role? (3) Is the E2-induced (and therefore possibly the age-related) increase in pituitary DA secondary to an E2-induced increase in serum prolactin? In ovariectomized (OVX) mice, E2 implants increased pituitary DA in a time- and dose-dependent fashion. P implants administered to OVX mice simultaneously with E2 antagonized the E2-induced increase in pituitary DA. Daily injections of 5 alpha-dihydrotestosterone given in conjunction with E2 implants had no effect on basal or E2-increased pituitary DA in OVX mice. Thus, E2 is the only gonadal steroid examined which increases anterior pituitary DA. In intact aging mice, P attenuates the age-related increase in pituitary DA, supporting the hypothesis that the increased ratio of E2:P secreted by the ovaries of aging female mice is responsible for the age-related increase in pituitary DA. However, at advanced ages, intact male mice also showed modest increases in anterior pituitary DA.(ABSTRACT TRUNCATED AT 250 WORDS)
Ethel Percy Andrus Gerontology Center, University of Southern California, Los Angeles.
N
N
Telford
Y N
YN
Sinha
C E
CE
Finch
D000367:Age Factors; D000818:Animals; D013196:Dihydrotestosterone / Q000494:pharmacology*; D004298:Dopamine / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology*; D011388:Prolactin / Q000097:blood*; D012737:Sex Factors
D013196:Dihydrotestosterone; D011374:Progesterone; D004958:Estradiol; D011388:Prolactin; D004298:Dopamine