Estradiol also remodels the connectivity of the nuclei of the lordosis regulating circuitry. In the arcuate nucleus, estradiol induces dendritic spines, which are critical for estradiol-induced lordosis behavior. The initial spinogenesis is mediated by the stimulation of membrane estrogen receptors that deactivate (phosphorylate) an actin depolymerizing agent, cofilin. After estradiol stimulation, it takes approximately 20 hrs for the newly formed spines to become functional. We are examining the cellular and nuclear signaling pathways that underlie this estradiol induced maturation.