Recent Evidence for Rapid Synthesis and Action of Oestrogens During Auditory Processing in a Songbird

Abstract

It is now clear that estrogens are not just circulating reproductive hormones, but that they also have neurotransmitter-like properties in a wide range of brain circuits. The view of estrogens as intrinsic neuromodulators that shape behavior has been bolstered by a series of recent developments from multiple vertebrate model systems. Here, we review several recent findings from studies of songbirds showing how the identified neural circuits that govern auditory processing and sensorimotor integration are modulated by the local and acute production of estrogens. First, studies using in vivo microdialysis demonstrate that estrogens fluctuate in auditory cortex (30-min time bin resolution) when songbirds are hearing song and interacting with conspecifics. Second, estrogens rapidly boost the auditory-evoked activity of neurons in the same auditory cortical region, enhancing auditory processing. Third, local pharmacological blockade of estrogen signaling in this region impairs auditory neuronal responsiveness as well as behavioral song preferences. Fourth, the rapid estrogen actions that occur within the auditory cortex can propagate upstream (transsynaptically) to sensorimotor circuits to enhance the neural representation of song. Lastly, we present new evidence that the receptor for the rapid actions of estradiol is likely in neuronal membranes, and that traditional nuclear estrogen receptor agonists do not mimic these rapid actions. Broadly speaking, many of these findings are observed in both males and females, emphasizing the fundamental importance of estrogens in neural circuit function. Together, these and other emergent studies provide support for rapid, brain-derived estrogen signaling in regulating sensorimotor integration, learning and perception.

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