Differential expression of estrogen receptor alpha and beta in rat dorsal root ganglion neurons

Estrogen receptor alpha (ER alpha) and estrogen receptor beta (ER beta) mRN As are both expressed in rat dorsal root ganglion (DRG) neurons, but the di stribution of these two mRNAs differs markedly. Radiolabeled probes highly specific to ER alpha or ER beta mRNAs were used for in situ hybridization s tudies; two antibodies specific to ER alpha protein were used for immunocyt ochemistry and specific primers were used for reverse transcription polymer ase chain reaction (RT-PCR) studies, These revealed that ER beta mRNA is wi dely expressed in the DRG of both male and female rats, with virtually all neurons showing positive signals. In contrast, ER alpha mRNA, as well as nu clear localized ER alpha protein, is more restricted in its localization an d is present in many, but not all, of the small-sized (< 600 mu m(2)) DRG n eurons, but is only rarely present in larger neurons, The L6-S1 DRG levels, which contain sensory neurons that innervate reproductive tissues, are rel atively enriched in ER alpha compared to L3-L5 DRG levels, which contain se nsory neurons that innervate hind limb regions, Long-term estrogen treatmen t of ovariectomized rats (21-28 days) dramatically reduces immunocytochemic ally detectable ER alpha protein in the DRG relative to that in ovariectomi zed controls, RT-PCR studies also showed that long-term estrogen treatment of ovariectomized rats downregulates the levels of ER alpha mRNA, but upreg ulates the levels of ER beta mRNA in the DRG, Interestingly, in intact cycl ing female rats, ER alpha and ER beta mRNA levels in the DRG were both high er during proestrus compared to metestrus, These findings suggest that the changes in expression of estrogen receptors which occur dynamically during the estrus cycle differ from those induced by long-term estrogen treatment of ovariectomized animals. J. Neurosci, Res, 57:603-615, 1999. (C) 1999 Wil ey-Liss, Inc.