title: Vernal increases in prolactin levels of nonbreeding male and female canvasbacks (Aythya valisineria).
abstract: Serum levels of prolactin were determined in nonbreeding male and female canvasbacks (Aythya valisineria) from mid-April to late June to evaluate the temporal changes occurring during spring. During this time interval, serum prolactin levels increased 1.5- to 2-fold in both males and nonlaying females (P less than 0.01). Serum prolactin levels of males and females exposed to natural lighting and temperature at Delta, Manitoba (50 degrees 11'N, 98 degrees 19'W), steadily increased from mid-April when the daylength was 14 hr light and peaked in mid-June when daylength was 16.25 hr light. Administration of exogenous estradiol via slow-release subdermally implanted capsules in females with intact reproductive systems had a marginal effect on reducing the seasonal increase in prolactin. Exogenous testosterone in similar slow-release capsules implanted subdermally in males had no influence on circulating prolactin levels.
authors.affiliation: Department of Ecology, University of Minnesota, Minneapolis 55455.
authors.forename: C K
authors.initials: CK
authors.lastname: Bluhm
authors.forename: R E
authors.initials: RE
authors.lastname: Phillips
authors.forename: W H
authors.initials: WH
authors.lastname: Burke
mesh_terms: D000818:Animals; D004372:Ducks / Q000097:blood / Q000502:physiology*; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D008027:Light; D008297:Male; D011388:Prolactin / Q000097:blood*; D012621:Seasons; D013696:Temperature; D013739:Testosterone / Q000494:pharmacology
chemical_list: D013739:Testosterone; D004958:Estradiol; D011388:Prolactin