Modulation by estrogen-receptor directed drugs of 5-hydroxytryptamine-2A receptors in rat brain.

Hormonal specificity of modulation of brain 5-HT(2A) receptors was investigated by comparing activity of compounds with varying effects on estrogen response in breast, bone, and uterus. A two-week estradiol treatment stimulated the decreased uterine weight of ovariectomized rats to intact rat values whereas an increase of 29% with tamoxifen and 16% with raloxifene was observed compared to vehicle-treated ovariectomized rats. In 18 assayed brain regions, ovariectomy decreased 5-HT(2A) receptor binding and mRNA levels in anterior cingulate and frontal cortices, striatum, and nucleus accumbens; estradiol restored this decrease to intact rat values. Dehydroepiandrosterone (DHEA) increased ovariectomized rats 5-HT(2A) receptor expression only in striatum and cortical amygdala. Tamoxifen increased 5-HT(2A) receptor density only in striatum. Raloxifene, an uterine estrogen receptor (ER) antagonist, increased, like estradiol, 5-HT(2A) receptor density and expression in cingulate and frontal cortices, striatum, and nucleus accumbens. Brain regional specificity of estradiol, DHEA, tamoxifen, and raloxifene on 5-HT(2A) receptors was observed which can be dissociated from peripheral activity.