Estrogen receptor-α mediates estradiol attenuation of ATP-induced Ca2+ signaling in mouse dorsal root ganglion neurons

A mechanism underlying gender-related differences in pain perception may be estrogen modulation of nociceptive signaling in the peripheral nervous system. In rat, dorsal root ganglion (DRG) neurons express estrogen receptors (ERs) and estrogen rapidly attenuates ATP-induced Ca2+ signaling. To determine which estrogen receptor mediates rapid actions of estrogen, we showed ER alpha and ER beta expression in DRG neurons from wild-type (WT) female mice by RT-PCR. To study whether ER alpha or ER beta mediates this response, we compared estradiol action mediating Ca2+ signaling in DRG neurons from WT, ERa knockout (ER alpha KO) and ER beta KO mice in vitro. ATP, an algesic agent, induced [Ca2+](i) transients in 48% of small DRG neurons from WT mice. 17 beta-Estradiol (E-2) inhibited ATP-induced intracellular Ca2+ concentration ([Ca2+](i)) with an IC50 of 27 nM. The effect of E-2 was rapid (5-min exposure) and stereo specific; 17 alpha-estradiol had no effect. E-2 action was blocked by the ER antagonist ICI 182,780 (1 mu M) in WT mouse. Estradiol coupled to bovine serum albumin (E-6-BSA), which does not penetrate the plasma membrane, had the same effect as E-2 did, suggesting that a membrane-associated ER mediated the response. In DRG neurons from ER beta KO mice, E-2 attenuated the ATP-induced [Ca2+](i) flux as it did in WT mice, but in DRG neurons from ERaKO mice, E-2 failed to inhibit the ATP-induced [Ca2+](i) increase. These results show that mouse DRG neurons express ERs and the rapid attenuation of ATP-induced [Ca2+](i) signaling is mediated by membrane-associated ER alpha. (c) 2005 Wiley-Liss, Inc.