Estrogen exerts long-term effects in almost every cell through regulation of gene transcription. However, it has been known for some time that estrogen can rapidly alter neuronal firing within seconds, indicating that some cellular effects of estrogen could occur via non-genomic mechanisms. G-protein-coupled receptors (GPCRs) are the largest class of membrane-bound receptors, and it appears that many of the rapid effects mediated by estrogen could involve changes in GPCR-effector system coupling in excitable cells within the reproductive axis.