Modulation of hypothalamic neuronal activity through a novel G-protein-coupled estrogen membrane receptor

Estrogens are involved in the hypothalamic control of multiple homeostatic functions including reproduction, stress responses, energy metabolism, sleep cycles, temperature regulation and motivated behaviors. The actions of 17β-estradiol (E₂) in the brain have been attributed to the activation of estrogen receptors α and β, as well as G-protein-coupled or other membrane-associated estrogen receptors. Recently, we have identified a putative membrane-associated estrogen receptor that is coupled to desensitization of GABA_B receptors in guinea pig and mouse hypothalamic neurons including proopiomelanocortin (POMC) neurons. We have synthesized a new nonsteroidal compound, STX, which selectively targets the Gαq-coupled phospholipase C-protein kinase C-protein kinase A pathway, and have established that STX is more potent than E₂ in mediating this desensitization in an ICI 182,780-sensitive manner in both guinea pig and mouse neurons. Both E₂ and STX are fully efficacious in estrogen receptor α, β knock-out mice. Finally, we observed that the putative membrane-associated estrogen receptor is different from GPR30 in arcuate neurons using whole-cell patch recording in hypothalamic slices from GPR30 knock-out mice. Collectively, these findings suggest that the mER is distinct from ERα, ERβ or GPR30.