ESTROGEN-RECEPTOR FOUND IN THE FACIAL NUCLEUS OF THE NEWBORN RAT IS SUPPRESSED BY EXOGENOUS ESTROGEN - IMMUNO AND IN-SITU HYBRIDIZATION HISTOCHEMICAL-STUDIES

Expression of the messenger RNA coding estrogen receptor (ER-mRNA) was detected in the ventromedial subnucleus of the facial nucleus of the newborn rat by in situ hybridization histochemistry (ISHH). The hybrid ization signal in this subnucleus increased from 1 to 6 days of age, t hen decreased at 11 days. By immunohistochemistry (IHC) using an antis erum which detects estrogen receptor (ER) specifically, immunopositive signals were also detected in the same subnucleus of the adjacent sec tions. On the other hand, neither of these signals were encountered in the same subnucleus of the adult rat. Thus, the present result extend our previous work (Yokosuka and Hayashi, 1992) showing that the expre ssion of the ER in the facial nucleus is transient. A sex difference i n the expression of ER molecules was not apparent by ISHH and IHC. Mor eover,,daily injections of estradiol from the day of birth suppressed the expression of ER in the subnucleus at 6 and 11 days of age. Thus, as has been detected in the mediobasal hypothalamus, ER-mRNA was revea led to be down-regulated by estrogen.