Implants of Estradiol Conjugated to Bovine Serum Albumin in the Male Rat Medial Preoptic Area Promote Copulatory Behavior

Abstract

The expression of mating behavior in male rats is dependent on estrogen-responsive neurons in the medial preoptic area (MPO). Previous reports showed that mating is attenuated if the aromatization of testosterone to estradiol (E₂) is blocked in the MPO and that mating is maintained by MPO E₂ implants. However, the mechanisms by which E₂ exerts its action are not fully understood. It had been thought that E₂ acted exclusively by binding to nuclear estrogen receptors to exert it effects; however, recent reports suggest that E₂ also binds to membrane-associated receptors activating downstream intracellular cascade responses. In this study, we aimed to determine if an action of E₂ at the cell surface is sufficient to support mating behavior. Therefore, either vehicle, E₂, or E₂ conjugated to bovine serum albumin (BSA-E₂: a complex of E₂ and a large protein that will not cross the plasma membrane, thereby restricting the action of E₂ to cell surface signaling) was chronically administered bilaterally to the MPO of castrated, dihydrotestosterone-treated male rats. Mating behavior was supported by MPO BSA-E₂ implants, suggesting that E₂ operates in the MPO via a cell surface mechanism to facilitate male rat mating behavior.

siRNA silencing of estrogen receptor-α expression specifically in medial preoptic area neurons abolishes maternal care in female mice

“…In contrast, stimulation of the POA increases copulation in male mice (44), and the expression of c-Fos in the POA is increased in male mice (43,45,46). Within the POA, implants of estradiol promote sexual behaviors in male mice (22,47,48). In female mice, lesions of the POA decrease proceptivity and increase receptivity in female mice, whereas electrical stimulation of the MPA led to persistent decreases in lordosis (49,50) without interfering with proceptivity (50).…”

Rapid control of male typical behaviors by brain-derived estrogens

“…Combined with the idea that some genomic priming is required to observe rapid effects of estrogens on male sexual behavior [56; 264], these results suggest that the acute control of male sexual behavior by estrogens likely involves an integration of non-genomic and genomic processes depending on ERα, at least in part. Interestingly, copulatory behavior was facilitated within 48h after the bilateral implantation of E 2 -BSA in the medial preoptic area (MPOA) of castrated male rats chronically treated with the androgenic metabolite of testosterone, dihydrotestosterone (DHT; [119]). This observation first suggested that estrogen membrane signaling was involved in the control of male sexual behavior.…”

Androgen Receptors, Sex Behavior, and Aggression

“…Inhibition of testosterone conversion to oestrogen by infusion of the aromatase inhibitor, fadrozole, into the MPOA of gonadally intact male rats decreased sex behaviours (49), and sex behaviours were restored with MPOA implants of oestrogen and oestrogen-BSA conjugate, suggesting that non-genomic mechanisms mediated oestrogen action (50). Thus, both AR and ER in the MPOA are critical for the expression of male sexual behaviour.…”