Auto-regulation of estrogen receptor subtypes and gene expression profiling of 17β-estradiol action in the neuroendocrine axis of male goldfish

Auto-regulation of the three goldfish estrogen receptor (ER) subtypes was examined simultaneously in multiple tissues, in relation to mRNA levels of liver vitellogenin (VTG) and brain transcripts. Male goldfish were implanted with a silastic implant containing either no steroid or 17β-estradiol (E2) (100 μg/g body mass) for one and seven days. Liver transcript levels of ERα were the most highly up-regulated of the ERs, and a parallel induction of liver VTG was observed. In the testes (7 d) and telencephalon (7 d), E2 induced ERα. In the liver (1 d) and hypothalamus (7 d) ERβ1 was down-regulated, while ERβ2 remained unchanged under all conditions. Although aromatase B levels increased in the brain, the majority of candidate genes identified by microarray in the hypothalamus (1 d) decreased. These results demonstrate that ER subtypes are differentially regulated by E2, and several brain transcripts decrease upon short-term elevation of circulating E2 levels.