Rapid actions of estradiol on cyclic amp response-element binding protein phosphorylation in dorsal root ganglion neurons

Abstract

Actions of gonadal steroids have not been widely investigated in the peripheral nervous system, although many dorsal root ganglion (DRG) and autonomic pelvic ganglion (PG) neurons express estrogen receptors (ERs). We have studied the effects of 17β-estradiol exposure on cultured DRG and PG neurons from adult rats. Western blotting analysis of DRG extracts detected phosphorylation of ERK1 and ERK2 (extracellular signal-regulated kinases) that peaked 10 min after exposure to 17β-estradiol. These extracts contain both neurons and glia; therefore, to determine if this response occurred in DRG neurons, we developed an immunocytochemical method to specifically measure activation in individual neurons. These measurements showed that estradiol increased phosphorylation of CREB (cyclic AMP response-element binding protein), which was consistently blocked by the ERK pathway inhibitor PD98059 but not by the inhibitors of phosphatidylinositol 3-kinase, wortmannin and LY294002. 17β-Estradiol activation of CREB in DRG neurons was reduced by the ER antagonist, ICI182780. In contrast, in PG neurons estradiol did not affect CREB phosphorylation, highlighting a difference in E2 responses in different populations of peripheral neurons. This study has shown that estrogens can rapidly activate signaling pathways associated with CREB-mediated transcriptional regulation in sensory neurons. As these pathways also mediate many effects of neurotrophic factors, changes in estrogen levels (e.g. during puberty, pregnancy or menopause) could have broad-ranging genomic and non-genomic actions on urogenital pain sensation and reflex pathways.