Estradiol (E2) stimulates luteinizing hormone receptor (lhcgr) expression via nuclear estrogen receptors (nERs) in the zebrafish ovary. We have demonstrated that endocrine hormones such as gonadotropin (hCG) and paracrine factors such as epidermal growth factor (EGF) and pituitary adenylate cyclaseactivating peptide (PACAP) can modulate E2-induced lhcgr expression in vitro. These observations raised a question on whether these hormones and factors exert their effects via regulating the expression of nERs. In this study, we first characterized the spatiotemporal expression profiles of three nER subtypes win the zebrafish ovary, including esr1 (ER alpha), esr2a (ER beta 2) and esr2b (ER(beta 1). All three nERs increased their expression at the pre-vitellogenic stage and peaked at mid- (esrl and esr2a) or late vitellogenic (esr2b) stage, followed by a significant decline at the full-grown stage. RT-PCR analysis showed that esri and esr2b were exclusively expressed in the follicle layer while esr2a was expressed in both compartments. We then examined how E2, hCG, PACAP and EGF regulated the expression of nERs in cultured zebrafish follicle cells. E2 quickly increased esri but reduced esr2a and esr2b expression from 1.5 to 12 h of treatment. Similarly, EGF down-regulated esr2a significantly at 1.5 h and this effect was further intensified at 24 h. hCG decreased the expression of all three nER subtypes with similar potency throughout the 24-h time-course. Interestingly, PACAP exerted a biphasic regulation on esr2a. Our present study suggests that nERs, especially esr2a, provide potential target points for other hormones and factors to modulate E2 activity during folliculogenesis in the zebrafish. (C) 2016 Elsevier Inc. All rights reserved.