Nongenomic effects of estradiol on aggression under short day photoperiods

Abstract

In several vertebrate species, the effects of estrogens on male aggressive behavior can be modulated by environmental cues. In song sparrows and rodents, estrogens modulate aggression in the nonbreeding season or winter-like short days, respectively. The behavioral effects of estrogens are rapid, which generally is considered indicative of nongenomic processes. The current study further examined the hypothesis that estradiol acts nongenomically under short days by utilizing a protein synthesis inhibitor, cycloheximide (CX). Mice were housed in either short or long day photoperiods, and treated with an aromatase inhibitor. One hour before resident-intruder testing mice were injected with either CX or saline vehicle, and 30 minutes later were treated orally with either cyclodextrin conjugated estradiol or vehicle. Under short days, mice treated with estradiol showed a rapid decrease in aggressive behavior, independent of CX administration. CX alone had no effect on aggression. These results show that protein synthesis is not required for the rapid effects of estradiol on aggression, strongly suggesting that these effects are mediated by nongenomic processes. We also showed that estradiol suppressed c-fosimmunoreactivity in the caudal bed nucleus of the stria terminalis under short days. No effects of estradiol on behavior or c-fos expression were observed in mice housed under long days. Previously we had also demonstrated that cage beddinginfluenced the directional effects of estrogens on aggression. Here, we show that the phenomenon of rapid action of estradiol on aggression under short days is a robust result that generalizes to different bedding conditions.

Hypothalamic vasopressin systems are more sensitive to the long term effects of social defeat in males versus females

“…In control males, we observed that the number of AVP -ir cells in the BNSTmp was positively correlated with the number of bites, consistent with a previous study (Laredo et al, 2013). Male California mice that are cross fostered by the less aggressive white-footed mouse ( Peromyscus leucopus ) are less aggressive and have reduced AVP -ir staining in the BNSTmp (Bester-Meredith and Marler, 2001).…”

Rapid Effects of an Aggressive Interaction on Dehydroepiandrosterone, Testosterone and Oestradiol Levels in the Male Song Sparrow Brain: a Seasonal Comparison

“…Previous research shows that oestrogens increase aggressive behaviour in the nonbreeding season (4,7,(51)(52)(53)(54) and androgens and oestrogens are strongly implicated in dominance and aggression that occurs in the context of breeding. Several factors may explain this pattern of results.…”

Rapid effects of estrogens on behavior: Environmental modulation and molecular mechanisms

“…Still, the impact of these compounds is generally under appreciated. As discussed above estrogens were found to increase aggression in Peromyscus when corncob bedding was used [45, 48], whereas estrogens decreased aggression when Carefresh was used [53, 56] (Fig 4). Previous work had determined that corncob bedding disrupts male and female sexual behavior in rats, and that this effect was mediated by THF-diols.…”

“…California mice were housed under short days or long days and then castrated and treated with fadrozole. After recovery each mouse was injected with either saline or CX 1 hour before resident-intruder tests [53]. Thirty minutes before testing, mice were given an oral dose of cyclodextrin-encapsulated estradiol, cyclodextrin alone, or saline vehicle.…”

“…In the first two studies [45, 48], corncob was used as cage bedding, whereas the CX study [53] used a cardboard-based bedding (Carefresh). Corncob bedding is attractive for animal facility managers because it is absorbent and has lower dust levels.…”