title: Hormones modulate the concentration of cytoplasmic progestin receptors in the brain of male ring doves (Streptopelia risoria).
abstract: A cytoplasmic progestin receptor has been characterized in the brain of castrated ring doves using an in-vitro assay that measures the binding of a synthetic progestin, [3H]17 alpha,21-dimethyl-19-nor-pregna-4,9-diene-3,20-dione(promegestone; R5020). The affinity of the receptor was similar in both the hyperstriatum and the hypothalamus (Kd approximately equal to 4 X 10(-10) mol/l). Its concentration was higher in the anterior hypothalamus-preoptic area (63 +/- 4 fmol/mg (S.E.M.) protein) than in other brain regions (posterior hypothalamus, 33 +/- 5; hyperstriatum, 28 +/- 3; midbrain, 17 +/- 4 fmol/mg protein; n = 7). Progesterone and R5020 competed well for binding but oestradiol and 5 beta-dihydrotestosterone did not. Corticosterone and, to a lesser extent, testosterone and 5 alpha-dihydrotestosterone completed for binding but much higher concentrations were required than for progestins. Injections of testosterone (200 micrograms testosterone propionate daily for 7 days) significantly increased the concentration of progestin receptors in the anterior and posterior hypothalamus without having any significant effect on other brain areas. Shorter treatment, lasting for 2 days, with testosterone propionate (200 micrograms daily), 5 alpha-dihydrotestosterone (200 micrograms daily) or oestradiol benzoate (50 micrograms daily) did not always cause this increase but seven injections of oestradiol benzoate (50 micrograms daily for 7 days) were even more effective than seven injections of testosterone propionate (200 micrograms daily for 7 days). These data suggested that the sensitivity to progesterone of the brain of the bird changes as a consequence of increases in the level of testosterone in the circulation.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002369:Castration; D010856:Columbidae / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D013196:Dihydrotestosterone / Q000494:pharmacology; D012739:Gonadal Steroid Hormones / Q000494:pharmacology; D008297:Male; D011372:Progestins; D011397:Promegestone / Q000378:metabolism; D011980:Receptors, Progesterone / Q000187:drug effects / Q000378:metabolism*
chemical_list: D012739:Gonadal Steroid Hormones; D011372:Progestins; D011980:Receptors, Progesterone; D013196:Dihydrotestosterone; D011397:Promegestone