Relationships between rapid changes in local aromatase activity and estradiol concentrations in male and female quail brain

Estradiol-17β (E₂) synthesized in the brain plays a critical role in the activation of sexual behavior in many vertebrate species. Because E₂ concentrations depend on aromatization of testosterone, changes in aromatase enzymatic activity (AA) are often utilized as a proxy to describe E₂ concentrations. Utilizing two types of stimuli (sexual interactions and acute restraint stress) that have been demonstrated to reliably alter AA within minutes in opposite directions (sexual interactions = decrease, stress = increase), we tested in Japanese quail whether rapid changes in AA are paralleled by changes in E₂ concentrations in discrete brain areas. In males, E₂ in the pooled medial preoptic nucleus/medial portion of the bed nucleus of the stria terminalis (POM/BST) positively correlated with AA following sexual interactions. However, following acute stress, E₂ decreased significantly (approximately 2-fold) in the male POM/BST despite a significant increase in AA. In females, AA positively correlated with E₂ in both the POM/BST and mediobasal hypothalamus supporting a role for local, as opposed to ovarian, production regulating brain E₂ concentrations. In addition, correlations of individual E₂ in POM/BST and measurements of female sexual behavior suggested a role for local E₂ synthesis in female receptivity. These data demonstrate that local E₂ in the male brain changes in response to stimuli on a time course suggestive of potential non-genomic effects on brain and behavior. Overall, this study highlights the complex mechanisms regulating local E₂ concentrations including rapid stimulus-driven changes in production and stress-induced changes in catabolism.