This chapter reviews the contribution of avian studies towards our understanding of the constitutive provision of estrogens within the brain. The chapter first summarizes numerous studies describing the distribution of aromatase across diverse avian taxa. Then this chapter focuses on the novel finding, that of the expression, sexual dimorphism, and behavioral consequence of aromatization within presynaptic boutons of the brain. The compartmentalization of aromatase into presynaptic boutons appears to function as a highly precise form of cellular communication that may combine aspects of...

This chapter reviews the contribution of avian studies towards our understanding of the constitutive provision of estrogens within the brain. The chapter first summarizes numerous studies describing the distribution of aromatase across diverse avian taxa. Then this chapter focuses on the novel finding, that of the expression, sexual dimorphism, and behavioral consequence of aromatization within presynaptic boutons of the brain. The compartmentalization of aromatase into presynaptic boutons appears to function as a highly precise form of cellular communication that may combine aspects of chemical and electrical signaling. This synaptocrine aromatization establishes estrogen produced by neural aromatization as both a traditional hormonal signal as well as an acutely regulated neuromodulator, or even neurotransmitter. The distribution, regulation, and function of this novel form of neurohormonal communication is yet another example of the contribution of avian biology towards broadening our understanding of the interactions among hormones, brain, and behavior.