| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 2800364 | General and Comparative Endocrinology | 2013 | 8 Pages |
The onset of puberty and reproduction are tightly controlled by extrinsic and intrinsic inputs combined with genetically determined biological blueprints. Environmental inputs are then mediated by the brain–pituitary–gonad endocrine axis resulting in a unified output. In fish, one of the primary factors controlling the timing of sexual maturation is light, although how these signals are mediated in the brain and pituitary is not well understood. We therefore aimed to elucidate the molecular basis of the control of reproduction during the first spawning season in two year old female Atlantic cod. To this end, we measured GnRH and GnRH-R variant gene expression in brains and pituitaries collected from cod kept under four different photoperiod regimes: natural light (NL), continuous light (LL) and combined treatment of NL–LL and LL–NL. LL inhibited sexual development and spawning and LL–NL delayed sexual development and spawning. LL inhibited the spawning-related increase in brain GnRH3 and pituitary GnRH-R2a gene expression found under NL conditions, and the expression of these genes were delayed in concert with spawning of LL–NL cod. This study indicates that regulation of brain GnRH3 and pituitary GnRH-R2a genes likely mediates photoperiod induced changes in cod gonadal maturation.
► Pituitary GnRH-R2a gene expression increases in late-vitellogenic and running cod, whereas GnRH-R1b does not. ► Brain GnRH3 gene expression is up-regulated in spawning fish, while GnRH2 and 4 GnRH-Rs are not regulated in concert with GSI. ► Additional continuous light affects gonadal growth in female cod. ► Continuous light inhibits the increased brain GnRH3 and pituitary GnRH-R2a expression seen during the normal spawning period. ► Transfer from continuous to normal photoperiod in December delays increase in brain GnRH3 and pituitary GnRH-R2a expression.
