Hormonal Mechanisms Underlying Auditory Forebrain Selectivity inFemale Songbirds Público

Sanford, Sara Elizabeth (2009)

Permanent URL: https://etd.library.emory.edu/concern/etds/02870v94c?locale=es
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Abstract

Abstract Hormonal Mechanisms Underlying Auditory Forebrain Selectivity in Female Songbirds By Sara E. Sanford Sex steroids facilitate dramatic behavioral changes related to reproduction in seasonally breeding vertebrates and are increasingly implicated in the modulation of sensory processing related to sociosexual cues. Female white-throated sparrows ( Zonotrichia albicollis), for example, perform a copulation solicitation display in response to conspecific male song only during their mating season when plasma levels of estradiol (E2) are high. Using immediate early gene (IEG) transcription as a marker of cellular responses, Maney et al. (2006) demonstrated in female white-throated sparrows that (E2) affects the selectivity of the IEG response to hearing male song in the caudomedial nidopallium (NCM) of the auditory forebrain. Because NCM is a large heterogeneous area, we hypothesized that the effects of E2 on the expression of the IEG zenk are not uniform throughout NCM and sought to map the distribution of these effects. Non- breeding females with low endogenous levels of E2 were treated with E2 or a placebo and exposed to conspecific song, frequency-matched tones, or silence. We found that the effects of E2 on zenk induction in NCM are not uniform. In two rostral regions (NCMd and NCMv) the zenk response was selective for song over tones only in the E2-treated birds, whereas in the caudal region (NCMc) zenk expression was selective for song over tones regardless of hormone treatment. We also found that E2 treatment upregulated zenk expression independent of sound stimulus, which suggests that hormone treatment alone induces new gene transcription in the auditory forebrain. Our results suggest that specific regions of NCM are seasonally regulated and that basal levels of neuronal activity may be heightened in these regions during the reproductive season.

Table of Contents

Table of Contents

Introduction............................................................................................1 Methods.................................................................................................6 Animals............................................................................................6 Hormonal manipulation.........................................................................6 Sound stimuli.....................................................................................7 Stimulus presentation............................................................................8 Tissue collection..................................................................................8 Histology...........................................................................................9 Quantification of immunoreactive cells.......................................................9 Analysis of behavior............................................................................11 Results.................................................................................................12 Plasma estradiol levels.........................................................................12 ZENK induction within regions of interest..................................................12 Behavioral responses...........................................................................14 Discussion............................................................................................15 E2 and selectivity within subregions of NCM..............................................15 E2 and basal levels of ZENK expression....................................................19 Conclusion.......................................................................................21 References............................................................................................23 Figure Captions......................................................................................32 Tables and Figures Table 1. Dimensions for regions of interest......................................................30 Figure 1. Sagittal views of our regions of interest within NCM...............................33 Figure 2. The number of ZENK-ir cells within regions of NCM in blank implanted and E2-treated females listening to song, tones or silence..........................................34

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