Estrogenic actions in the brain: Estrogen, phytoestrogens, and rapid intracellular signaling mechanisms

The endogenous gonadal steroid 17 beta -estradiol (E-2) plays an important role in the development, maturation, and function of a wide variety of repr oductive and nonreproductive tissues, including those of the nervous system . The actions of E-2 at target tissues can be divided into 1) long-term "ge nomic" actions that are mediated by intracellular estrogen receptor-induced changes in gene expression and 2) rapid actions that modulate a diverse ar ray of intracellular signal transduction cascades. Environmental estrogens are compounds present in the environment that can mimic, and in some cases antagonize, the effects of endogenous estrogens. As a result of these actio ns, there is currently much interest within the scientific community regard ing the relative benefits or threats associated with exposure to different environmental estrogens. Within the general public there is considerable ac ceptance of the benefits associated with increased use of "natural" estroge ns as a component of a healthy diet and in postmenopausal women as an alter native to estrogen replacement therapies. First, this review will focus att ention on the role of estrogens in the central nervous system by briefly di scussing some of the known mechanisms through which estrogen's effects are mediated, focusing on rapid intracellular signaling mechanisms during neuro development. Second, with the hope of bringing attention to an area of stud y that until recently has received little consideration, we will briefly di scuss phytoestrogens and suggest that these compounds have the potential to influence rapid E-2-induced mechanisms in the nervous system in ways that may result in modified brain functions.