Selective estrogen receptor‐α but not ‐β agonist treatment modulates brain α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptors

Abstract

Estradiol was previously reported to decrease brain alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA)-receptor-specific binding. The contributions of estrogen receptor subtypes in the estradiol modulation of AMPA receptors and its predominant subunit GluR2 are unknown. These experiments investigated whether an estrogenic receptor subtype is involved in the estradiol effect on AMPA-receptor-specific binding and GluR2 mRNA levels. Ovariectomized Sprague-Dawley rats were treated 2 days after ovariectomy for 2 weeks with 17beta-estradiol, an agonist for ERalpha 4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT), or an agonist for ERbeta 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN) and compared with intact control rats. Uterus weights, used as aperipheral measure of estrogenic activity, were decreased after ovariectomy and increased by estradiol and PPT but not DPN treatments. In prefrontal and cingulate cortices, the striatum, and the nucleus accumbens, ovariectomy increased [3H]AMPA-specific binding compared with intact controls, which was corrected by estradiol treatment. In all these brain regions, PPT, but not DPN, mimicked the estradiol decrease of AMPA-receptor-specific binding; in the cingulate cortex, the effect of PPT did not reach statistical significance. GluR2 mRNA levels of vehicle-treated ovariectomized rats remained unchanged compared with intact rats in the brain regions investigated. Estradiol and PPT treatment but not DPN decreased GluR2 subunit mRNA levels in the prefrontal cortex and the striatum of ovariectomized rats, whereas no significant change was observed in the cingulate cortex or the nucleus accumbens. The present results suggest that an ERalpha is involved in the estradiol modulation of AMPA receptors in the cortex, striatum, and nucleus accumbens.