Estradiol-dependent Catecholaminergic Innervation of Auditory Areas in a Seasonally Breeding Songbird

• Authors: Lisa L. Matragrano, Emory University; Sara E. Sanford, Emory University; Katrina G. Salvante, University of North Carolina Chapel Hill; Keith W. Sockman, University of North Carolina Chapel Hill; Donna Maney, Emory University
• Journal Title: European Journal of Neuroscience
• Volume: Volume 34, Number 3
• Publisher: Wiley: 12 months | 2011-08, Pages 416-425
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1111/j.1460-9568.2011.07751.x
• Subjects: Biology, Neuroscience
• Keywords: dopamine; dopamine beta-hydroxylase; norepinephrine; tyrosine hydroxylase; white-throated sparrow

Abstract

A growing body of evidence suggests that gonadal steroids such as estradiol (E2) alter neural responses not only in brain regions associated with reproductive behavior, but also in sensory areas. Because catecholamine systems are involved in sensory processing and selective attention, and because they are sensitive to E2 in many species, they may mediate the neural effects of E2 in sensory areas. Here, we tested the effects of E2 on catecholaminergic innervation, synthesis, and activity in the auditory system of white-throated sparrows, a seasonally breeding songbird in which E2 promotes selective auditory responses to song. Non-breeding females with regressed ovaries were held on a winter-like photoperiod and implanted with silastic capsules containing either no hormone or E2. In one hemisphere of the brain, we used immunohistochemistry to quantify fibers immunoreactive for tyrosine hydroxylase or dopamine beta-hydroxylase in the auditory forebrain, thalamus, and midbrain. E2 treatment increased catecholaminergic innervation in the same areas of the auditory system in which E2 promotes selectivity for song. In the contralateral hemisphere, we quantified dopamine, norepinephrine and their metabolites in tissue punches using HPLC. Norepinephrine increased in the auditory forebrain, but not the midbrain, after E2 treatment. We found evidence of interhemispheric differences, both in immunoreactivity and catecholamine content did not depend on E2 treatment. Overall, our results show that increases in plasma E2 typical of the breeding season enhance catecholaminergic innervation and synthesis in some parts of the auditory system, raising the possibility that catecholamines play a role in E2-dependent auditory plasticity in songbirds.