Summary

Both the estrogen-synthesizing enzyme and estrogen receptors are present in the brain. The distribution of estrogen-sensitive cells in the brain corresponds to regions that control sexual differentiation, masculine and feminine sexual behaviors, and aggressive behaviors as well as grooming. All these are indicative that estrogens play diverse roles in several neural circuits. From observing animal models and psychiatric patients, it is evident that estrogens have modulatory effects on grooming and related behaviors.

Introduction

Traditionally viewed as female reproductive hormones, estrogens have in the past decade been shown to have widespread biological actions in both males and females. Estrogens are C-18 steroids derived from cholesterol and occur naturally in the human body in three different forms: 17β-estradiol (E2), estrone (E1), and estriol (E3) (Young et al. 1964). The last step in estrogen biosynthesis is the aromatization of androgens, including testosterone and androstenedione, to estradiol and estrone respectively. In addition to the reproductive organs, estrogens are expressed in many tissues including: breast, fat, muscle, bone, and brain (Carreau et al. 1999; Jenkins et al. 1993; Sasano and Ozaki 1997; Sasano et al. 1997, 1998; Simpson et al. 1997a). Investigations on the mechanism of action of estrogens have escalated greatly over the past decade due to the discovery of three types of estrogen receptors: estrogen receptor α (ERα; Green et al. 1986) estrogen receptor β (ERβ; Kuiper et al. 1996), and membrane ER (ERX; Watson et al. 1999). However, the last is probably ERα in most cases.