ESTRADIOL REDUCTION OF ALPHA(2)-ADRENOCEPTOR BINDING IN FEMALE RAT CORTEX IS CORRELATED WITH DECREASES IN ALPHA(2A D)-ADRENOCEPTOR MESSENGER-RNA/

We developed a quantitative RNAse protection assay for alpha(2A/D)-adr enoceptor messenger RNA in rats to test the hypothesis that decreases in cortical alpha(2)-adrenoceptor binding observed following estrogen treatment of ovariectomized rats correlate with reduced levels of mess enger RNA encoding the predominant alpha(2)-adrenoceptor subtype expre ssed in cortex. Estradiol treatment for 48 h reduced cortical alpha(2A /D)-adrenoceptor messenger RNA by approximately 50% when compared to o variectomized, oil-treated control animals. Estradiol down-regulation of alpha(2A/D)-adrenoceptor messenger RNA was accompanied by a signifi cant decrease in cortical alpha(2)-adrenoceptor density, as measured b y H-3-RX821002 binding. Estrogen treatment did not alter alpha(2A/D)-a drenoceptor messenger RNA or alpha(2)-adrenoceptor binding in female r at hypothalamus-preoptic area. This study provides the first evidence that estradiol regulates expression of postsynaptic alpha(2)-adrenocep tors in female rat frontal cortex, suggesting a possible molecular sub strate for hormonal modulation of cognitive function. (C) 1997 IBRO. P ublished by Elsevier Science Ltd.