Estrogen receptors α and β in the central amygdala and the ventromedial nucleus of the hypothalamus: Sociosexual behaviors, fear and arousal in female rats during emotionally challenging events

Estrogens receptors (ER) are involved in several sociosexual behaviors and fear responses. In particular, the ER alpha is important for sexual behaviors, whereas ER beta modulates anxiolytic responses. Using shRNA directed either against the ER alpha or the ER beta RNAs (or containing luciferase control) encoded within an adeno-associated viral vector, we silenced these receptors in the ventromedial nucleus of the hypothalamus (VMN) and the central amygdala (CeA). We exposed ovariectomized female rats, sequentially treated with estradiol benzoate and progesterone, to five stimuli, previously reported to elicit positive and negative affect. The subjects were housed in groups of 4 females and 3 males in a seminatural environment for several days before hormone treatment. We analyzed the frequency of a large number of behavior patterns. In addition, we performed analyses of co-occurrence in order to detect changes in the structure of behavior after infusion of the vectors. Silencing the ER alpha in the VMN disrupted lordosis and showed some anxiolytic properties in aversive situations, whereas silencing of the ER beta in this structure had no effect. This was also the case after silencing the ER alpha in the CeA. Silencing of the ER beta in this structure increased risk assessment, an expression of anxiety, and increased olfactory exploration of the environment. We hypothesize that the ER beta in the CeA has an important role in the well-established anxiolytic effects of estrogens, and that it may modulate arousal level. Furthermore, it seems that the ER alpha in the VMN is anxiogenic in aversive or threatening situations, in agreement with other studies.