Estrogen "receptors" in brain: an unsolved problem.

Various investigators have postulated that estrogen-sensitive structures contain "receptors" which accumulate and bind estradiol. Further, it has been implied that brain receptors function in a similar way to uterine receptors, even though the evidence for this conclusion is not strong. The present study was designed to compare the accumulation of radioactivity by brain and uterus following (3)H-estradiol treatment in estrous, diestrous, and ovariectomized rats. Uterus exhibited high levels of radioactivity in diestrus, but not in estrus or the ovariectomized condition. The accumulation of hormone by brain did not fluctuate with the various levels of endogenous hormone stimulation, but rather showed a pattern of uptake similar to muscle, a nontarget tissue. It was concluded that if brain hormone receptors exist, they do not respond to estradiol as do uterine receptors.