Stimulation of mouse GnRH receptor promoter by a GnRH agonist (Buserelin), or by a cAMP analogue, significantly increased reporter (luciferase) activity. Overexpression of Raf-1, ERK1, or ERK2 partially blocked Buserelin-stimulated luciferase activity. In contrast, treatment with a mitogen-activated protein kinase (MAPK) kinase inhibitor (PD 98059) activated basal and Buserelin-stimulated luciferase activity in a dose-dependent manner. Transient transfection of the deleted cAMP response element expression vector followed by pretreatment with PD98059 prior to Buserelin stimulation showed that the transcriptional response was decreased compared to wild-type promoter. A gel-mobility shift assay using a probe containing the cAMP response element showed the presence of two specific protein-DNA complexes that contain one or more members of the cAMP responsive element-binding (CREB) protein family. These results suggest that cAMP and CREB participate in the GnRH activation of GnRH receptor promoter activity and that the MAPK cascade is involved in the negative regulation of basal and GnRH-stimulated GnRH receptor transcriptional activity.