Estradiol plays a critical role in the feedback regulation of reproduction, in part by modulating the neurosecretory activity of gonadotropin-releasing hormone (GnRH) neurons. While indirect effects of estradiol on GnRH neurons have been clearly demonstrated, direct actions are still controversial. In the current study, we examined direct effects of 17β-estradiol upon the expression of receptors for afferent signals at the level of the GnRH neuron, using immortalized GT1-7 cells. Using RT-PCR, we confirmed the expression of mRNA for the adrenergic receptors (AR) α 1 A-, α 1 B-, α 1 D-, α 2 A-, α 2 C-, and β 1-AR, and showed for the first time that mRNAs for α 2 B-, β 2-and β 3-AR, for kisspeptin and its receptor GPR54 and for the novel estrogenic receptor GPR30 are expressed in GT1-7 cells. After treatment with 10 nM 17β-estradiol, α 1 B-AR mRNA was significantly increased (14-fold) after 6 h as determined by real-time PCR, while α 1 B-and α 1 D-AR mRNA were significantly increased (19-and 23-fold, respectively) after 24 h. The expression of KiSS-1 and GPR54 mRNAs were also significantly increased (8-and 6-fold, respectively) after 24 h treatment of GT1-7 cells with estradiol. GPR30 mRNA expression was not affected by estradiol. Our data also showed that kisspeptin-10 (1–10 nM) can significantly stimulate GnRH release and GnRH mRNA expression in GT1-7 cells. These results suggest that the complex physiologic effects of estradiol on the function of the reproductive axis could be mediated partly through direct modulation of the expression of receptors for afferent signals in GnRH neurons.