Traditional physiology teaching states that estrogen causes long term responses through its action on nuclear receptors (Estrogen receptor alpha and estrogen receptor beta). Recently there is evidence that estrogen can also act through transmembrane G protein coupled receptors called GPR30. These receptors can mediate short term non-genomic and long term genomic effects of estrogen. This new membrane receptor for estrogen has been reviewed in the following article published in Annual Review of Physiology.
Estrogen Signaling through the Transmembrane G Protein-Coupled Receptor GPR30. Eric R. Prossnitz et.al. Annu. Rev. Physiol. 2008. 70:165–90