title: GnRH mRNA levels in male three-spined sticklebacks, Gasterosteus aculeatus, under different reproductive conditions.
abstract: In vertebrates, reproduction is regulated by the brain-pituitary-gonad (BPG) axis, where the gonadotropin-releasing hormone (GnRH) is one of the key components. However, very little is known about the possible role of GnRH in the environmental and feedback control of fish reproduction. To investigate this, full-length gnrh2 (chicken GnRH II) and gnrh3 (salmon GnRH) sequences of male three-spined sticklebacks (Gasterosteus aculeatus), which are clustered with the taxa of the same GnRH type as other Euteleostei, were cloned and annotated. gnrh1 is absent in this species. The mRNA levels of gnrh2 and gnrh3 in the sticklebacks' brain were measured under breeding and post-breeding conditions as well as in castrated and sham-operated breeding fish and castrated/sham-operated fish kept under long-day (LD 16:8) and short-day (LD 8:16) conditions. Fully breeding males had considerably higher mRNA levels of gnrh2 and gnrh3 in the thalamus (Th) and in the telencephalon and preoptic area (T+POA), respectively, than post-breeding males. Sham-operated breeding males have higher gnrh3 mRNA levels than the corresponding castrated males. Moreover, higher gnrh2 mRNA levels in the Th and higher gnrh3 mRNA levels in the T+POA and hypothalamus (HypTh) were also found in long-day sham-operated males than in sham-operated fish kept under an inhibitory short day photoperiod. Nevertheless, gnrh2 and gnrh3 mRNA levels were not up-regulated in castrated males kept under long-day photoperiod, which suggests that positive feedbacks on the brain-pituitary-gonad axis are necessary for this response.
authors.affiliation: Department of Zoology, Stockholm University, Stockholm S-10691, Sweden; Marine Research Station, Academia Sinica, I-lan 262, Taiwan.
authors.forename: Yi Ta
authors.initials: YT
authors.lastname: Shao
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei 11676, Taiwan. Electronic address: yct@ntnu.edu.tw.
authors.forename: Yung Che
authors.initials: YC
authors.lastname: Tseng
authors.affiliation: Department of Biological Science and Technology, National Chiao Tung University, Taiwan.
authors.forename: Chia-Hao
authors.initials: CH
authors.lastname: Chang
authors.affiliation: Marine Research Station, Academia Sinica, I-lan 262, Taiwan.
authors.forename: Hong Young
authors.initials: HY
authors.lastname: Yan
authors.affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115 29, Taiwan.
authors.forename: Pung Pung
authors.initials: PP
authors.lastname: Hwang
authors.affiliation: Department of Zoology, Stockholm University, Stockholm S-10691, Sweden. Electronic address: bertil.borg@zoologi.su.se.
authors.forename: Bertil
authors.initials: B
authors.lastname: Borg
mesh_terms: D000818:Animals; D007987:Gonadotropin-Releasing Hormone / Q000096:biosynthesis* / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism* / Q000502:physiology; D008297:Male; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000378:metabolism; D012098:Reproduction; D023701:Smegmamorpha / Q000378:metabolism / Q000502:physiology
chemical_list: D012333:RNA, Messenger; C448022:gonadotropin-releasing hormone-III; D007987:Gonadotropin-Releasing Hormone; D011761:Pyrrolidonecarboxylic Acid
keywords: Feedback; GnRH2; GnRH3; Gonadectomy; Photoperiod; Stickleback; mRNA