Raynaud's phenomenon, which is characterized by intense cold-induced constriction of cutaneous arteries, is more common in females compared to males. Cold-induced constriction is mediated in part by enhanced activity of _2C-adrenoceptors (_2C-ARs) located on vascular smooth muscle cells (VSMs). Experiments were therefore performed to determine whether 17-estradiol regulates _2C-AR expression and function in cutaneous VSMs. 17-estradiol (0.01 to 10 nmol/L) increased expression of the _2C-AR protein and the activity of the _2C-AR gene promoter in human cultured dermal VSMs, which was assessed following transient transfection of the cells with a promoter-reporter construct. The effect of 17-estradiol was associated with increased accumulation of cyclic AMP and activation of the cyclic AMP-responsive Rap2 GTP binding protein. Transient transfection of VSMs with a dominant-negative mutant of Rap2 (Rap2-DN) inhibited the 17-estradiol-induced activation of the _2C-AR gene promoter, whereas a constitutively-active mutant of Rap2 (Rap2-CA) increased _2C-AR promoter activity. The effects of 17-estradiol were inhibited by the estrogen receptor antagonist, ICI 182,780 (1µmol/L), and were mimicked by a cell-impermeable form of the hormone (estrogen:BSA) or by the selective ER receptor agonist PPT (10nmol/L) or the selective ER receptor agonist DPN (10nmol/L). Therefore, 17-estradiol increased expression of _2C-ARs by interacting with cell surface receptors to cause a cyclic AMP/Rap2-dependent increase in _2C-AR transcription. In mouse tail arteries, 17-estradiol (10nmol/L) increased _2C-AR expression and selectively increased the cold-induced amplification of 2-AR constriction, which is mediated by _2C-ARs. An estrogen-dependent increase in expression of cold-sensitive _2C-ARs may contribute to the increased activity of cold-induced vasoconstriction under estrogen-replete conditions.