title: Estradiol selectively enhances auditory function in avian forebrain neurons.
abstract: Sex steroids modulate vertebrate sensory processing, but the impact of circulating hormone levels on forebrain function remains unclear. We tested the hypothesis that circulating sex steroids modulate single-unit responses in the avian telencephalic auditory nucleus, field L. We mimicked breeding or nonbreeding conditions by manipulating plasma 17β-estradiol levels in wild-caught female Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii). Extracellular responses of single neurons to tones and conspecific songs presented over a range of intensities revealed that estradiol selectively enhanced auditory function in cells that exhibited monotonic rate level functions to pure tones. In these cells, estradiol treatment increased spontaneous and maximum evoked firing rates, increased pure tone response strengths and sensitivity, and expanded the range of intensities over which conspecific song stimuli elicited significant responses. Estradiol did not significantly alter the sensitivity or dynamic ranges of cells that exhibited non-monotonic rate level functions. Notably, there was a robust correlation between plasma estradiol concentrations in individual birds and physiological response properties in monotonic, but not non-monotonic neurons. These findings demonstrate that functionally distinct classes of anatomically overlapping forebrain neurons are differentially regulated by sex steroid hormones in a dose-dependent manner.
authors.affiliation: Neurobiology and Behavior Graduate Program, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Caras
authors.forename: Matthew
authors.initials: M
authors.lastname: O'Brien
authors.forename: Eliot A
authors.initials: EA
authors.lastname: Brenowitz
authors.forename: Edwin W
authors.initials: EW
authors.lastname: Rubel
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods / Q000523:psychology; D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001307:Auditory Perception / Q000502:physiology*; D004343:Drug Implants / Q000494:pharmacology; D004958:Estradiol / Q000008:administration & dosage / Q000097:blood / Q000502:physiology*; D005260:Female; D009474:Neurons / Q000502:physiology; D017440:Photoperiod; D016548:Prosencephalon / Q000187:drug effects / Q000502:physiology*; D046370:Sparrows / Q000502:physiology; D014828:Vocalization, Animal / Q000187:drug effects / Q000502:physiology*
chemical_list: D004343:Drug Implants; D004958:Estradiol