G_q-mER is a G protein-coupled receptor present in the hypothalamus that has not yet been cloned. It is a membrane-associated receptor that is G_q-coupled to a phospholipase C–protein kinase C–protein kinase A (PLC–PKC–PKA) pathway. The receptor has been implicated in the control of energy homeostasis. G_q-mER is bound and activated by estradiol, and is a putative membrane estrogen receptor (mER). A non-steroidal diphenylacrylamide derivative, STX, which is structurally related to 4-hydroxytamoxifen (afimoxifene), is an agonist of the receptor with greater potency than estradiol (20-fold higher affinity) that has been discovered. Fulvestrant (ICI-182,780) has been identified as an antagonist of G_q-mER, but is not selective.