Role of feedbacks on the brain-pituitary-gonadal axis in fish reproduction


Project leader


Funding source

Formas - The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning


Project Details

Start date: 01/01/2006
End date: 31/12/2008
Funding: 1980000 SEK


Description

Vertebrate gonads are stimulated by pituitary gonadotropic hormones (GTHs): FSH and LH, which in turn are controlled by the brain. This brain-pituitary-gonadal (BPG) axis is under feedback control. The aim of this project is to find out what role(s) feedbacks on the BPG-axis have in regulating reproduction in fish: 1) To what extent are circulating levels of gonadal hormones homeostatically regulated? Hemicastration effects indicate that the control is not close. We intend to treat salmon with a range of steroid doses and measure hormone levels using RIA. Under close control, testes steroidogenesis should decline with increasing administration and circulating steroid levels show a plateau over a range of doses. 2) To what extent/how is puberty regulated by the BPG axis? One possibility is that levels of GTH-receptors, rather than GTH-levels control maturation. Expression of GTH-receptors will be measured in salmon testes biopsies and be compared with subsequent maturation. 3) Is photoperiodic control of reproduction mediated via changes in mechanisms on the BPG axis? Positive feedbacks on FSH under stimulatory photoperiod and negative feedbacks under non-stimulatory photoperiod was found in sticklebacks. By comparing the frequencies of castrated fish displaying positive and negative feedback (studied as FSHb-expression) and the frequencies of controls maturing under a range of photoperiods we are to find out if differences in feedbacks control which fish will mature or not.

Last updated on 2017-24-03 at 12:58