New evidence for estrogen receptors in gonadotropin-releasing hormone neurons

Estrogen exerts a critical regulatory influence upon the biosynthetic and s ecretory activity of the gonadotropin-releasing hormone (GnRH) neurons. It seems likely that estrogen regulates the behavior of the GnRH neuron throug h multiple transsynaptic, neuronal-glial, and direct membrane modes of acti on. Advances in our understanding of these mechanisms over the last 3 years are highlighted. In addition, very recent studies have begun to provide ev idence for the expression of estrogen receptors (ERs) in GnRH neurons in th e rodent. Although not yet firmly established, the current consensus suppor ts the hypothesis that GnRH neurons express ER beta. Evidence exists for ER beta mRNA expression by GnRH neurons throughout development and ER beta im munoreactivity has now also been detected in these cells. Murine GnRH neuro ns have further been shown to express estrogen receptor-related receptor-al pha, an orphan receptor thought to constitutively activate estrogen respons e elements. Together, these findings provide a cornerstone for the reassess ment of the role of ERs and related receptors in the direct genomic and pot ential nontranscriptional actions of estrogen upon the GnRH neuron. (C) 200 1 Academic Press.