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1.  Plasticity in Singing Effort and its Relationship with Monoamine Metabolism in the Songbird Telencephalon 
Developmental neurobiology  2010;70(1):41-57.
Factors intrinsic or extrinsic to individuals, such as their quality or the quality of competition in their social environment, can influence their communication signalling effort. We hypothesized that telencephalic monoamine secretion mediates the effects of a male’s own quality and quality of his social environment on his sexual signalling effort. The duration of a male European starling’s (Sturnus vulgaris) principal sexual signal, his song, positively correlates with several aspects of his quality, including his reproductive success, immunocompetence, and ability to attract mates. Therefore, the length of songs to which he is exposed reflects, in part, the quality of competition in his social environment. We manipulated the quality of the competitive environment by exposing male starlings to long or short songs for one week. We measured the length of songs produced by experimental males to gauge their quality, counted the number of songs they produced to gauge singing effort, and quantified telencephalic monoamine metabolism using HPLC. Singing effort increased with the length of the males’ own songs and with the length of songs to which we exposed them. Norepinephrine metabolism in Area X of the song control system was negatively correlated with the subjects’ mean song length and singing effort. Serotonin metabolism in the caudomedial mesopallium of the auditory telencephalon increased with the length of songs to which we exposed the subjects and with their singing effort. This raises the hypothesis that serotonin and norepinephrine secretion in the telencephalon help mediate the effects of extrinsic and intrinsic factors on signalling effort.
PMCID: PMC2905645  PMID: 19899137
bird song; monoamines; neuroplasticity; norepinephrine; serotonin
2.  Individual differences in the motivation to communicate relate to levels of midbrain and striatal catecholamine markers in male European starlings 
Hormones and behavior  2011;60(5):10.1016/j.yhbeh.2011.08.001.
Individuals display dramatic differences in social communication even within similar social contexts. Across vertebrates dopaminergic projections from the ventral tegmental area (VTA) and midbrain central gray (GCt) strongly influence motivated, reward-directed behaviors. Norepinephrine is also rich in these areas and may alter dopamine neuronal activity. The present study was designed to provide insight into the roles of dopamine and norepinephrine in VTA and GCt and their efferent striatal target, song control region area X, in the regulation of individual differences in the motivation to sing. We used high pressure liquid chromatography with electrochemical detection to measure dopamine, norepinephrine and their metabolites in micropunched samples from VTA, GCt, and area X in male European starlings (Sturnus vulgaris). We categorized males as sexually motivated or non-sexually motivated based on individual differences in song produced in response to a female. Dopamine markers and norepinephrine in VTA and dopamine in area X correlated positively with sexually-motivated song. Norepinephrine in area X correlated negatively with non-sexually-motivated song. Dopamine in GCt correlated negatively with sexually-motivated song, and the metabolite DOPAC correlated positively with non-sexually-motivated song. Results highlight a role for evolutionarily conserved dopaminergic projections from VTA to striatum in the motivation to communicate and highlight novel patterns of catecholamine activity in area X, VTA, and GCt associated with individual differences in sexually-motivated and non-sexually-motivated communication. Correlations between dopamine and norepinephrine markers also suggest that norepinephrine may contribute to individual differences in communication by modifying dopamine neuronal activity in VTA and GCt.
PMCID: PMC3827950  PMID: 21907203
dopamine; norepinephrine; communication; motivation; social context; courtship; song control system; social behavior; sexual behavior; songbird
3.  Estradiol-dependent Modulation of Serotonergic Markers in Auditory Areas of a Seasonally Breeding Songbird 
Behavioral Neuroscience  2011;126(1):110-122.
Because no organism lives in an unchanging environment, sensory processes must remain plastic so that in any context, they emphasize the most relevant signals. As the behavioral relevance of sociosexual signals changes along with reproductive state, the perception of those signals is altered by reproductive hormones such as estradiol (E2). We showed previously that in white-throated sparrows, immediate early gene responses in the auditory pathway of females are selective for conspecific male song only when plasma E2 is elevated to breeding-typical levels. In this study, we looked for evidence that E2-dependent modulation of auditory responses is mediated by serotonergic systems. In female nonbreeding white-throated sparrows treated with E2, the density of fibers immunoreactive for serotonin transporter innervating the auditory midbrain and rostral auditory forebrain increased compared with controls. E2 treatment also increased the concentration of the serotonin metabolite 5-HIAA in the caudomedial mesopallium of the auditory forebrain. In a second experiment, females exposed to 30 min of conspecific male song had higher levels of 5-HIAA in the caudomedial nidopallium of the auditory forebrain than birds not exposed to song. Overall, we show that in this seasonal breeder, (1) serotonergic fibers innervate auditory areas; (2) the density of those fibers is higher in females with breeding-typical levels of E2 than in nonbreeding, untreated females; and (3) serotonin is released in the auditory forebrain within minutes in response to conspecific vocalizations. Our results are consistent with the hypothesis that E2 acts via serotonin systems to alter auditory processing.
PMCID: PMC3266998  PMID: 21942431
5-HT; 5-HIAA; estradiol; serotonin transporter (SERT); songbird
4.  Validation of a new multiplex assay against individual immunoassays for the quantification of reproductive, stress and energetic metabolism biomarkers in urine specimens 
Measuring multiple hormones simultaneously in a single assay saves sample volume, labor, time, reagents, money and consumables. Thus, multiplex arrays represent a faster, more economically and ecologically sound alternative to singleton assays.
To validate a new, commercially-available multiplex female array produced by Quansys Biosciences against individual immunoassays for the quantification of six hormones in urine samples from women in different reproductive stages.
Urine samples were analyzed using the new Quansys multiplex female hormone array and compared with well-established individual immunoassays for adiponectin, free cortisol, c-peptide, estrone-3-glucuronide (E1G), follicle stimulating hormone beta-subunit (FSH-beta), and human chorionic gonadotropin beta-subunit (hCG-beta). Correlations between assays were assessed using Pearson correlation, linear regression and Bland-Altman analysis. The temporal profiles of free cortisol, E1G, FSH-beta and hCG-beta were also compared.
The multiplex array was highly correlated with the individual immunoassays for five of the tested hormones (Pearson’s correlation coefficient ≥ 0.75), and yielded temporal patterns of hormone profiles consistent with the individual immunoassays for free cortisol, E1G, FSH-beta and hCG-beta.
The Quansys multiplex female hormone array is a valid alternative method to individual immunoassays for the quantification of stress, reproductive and energetic hormones and metabolites in human urine samples and can be used to examine the dynamic interactions between these hormones.
PMCID: PMC3237917  PMID: 22121074
multiplex assay validation; cortisol; reproductive hormones; urine; repetitive measurements
5.  Estradiol-dependent Catecholaminergic Innervation of Auditory Areas in a Seasonally Breeding Songbird 
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.
PMCID: PMC3148281  PMID: 21714815
dopamine; dopamine beta-hydroxylase; norepinephrine; tyrosine hydroxylase; white-throated sparrow
6.  Female Lincoln's sparrows modulate their behavior in response to variation in male song quality 
Behavioral Ecology  2010;21(3):562-569.
Sexually reproducing organisms should mate with the highest quality individuals that they can. When female songbirds choose a mate, they are thought to use several aspects of male song that reflect his quality. Under resource-limited environmental conditions, male Lincoln's sparrows (Melospiza lincolnii) vary among one another in several aspects of song quality, including song length, song complexity, and trill performance. In a 2-pronged approach, we tested whether variation in song quality of male Lincoln's sparrows influences the behavior of females that are in a reproductive-like state. Over two trials, we exposed females to songs from the high and low ends of the distribution of naturally occurring song quality variation and found a higher level of behavioral activity in females exposed to high-quality songs, especially when they had first been exposed to low-quality songs. We also examined female phonotaxis toward antiphonally played songs with experimentally elevated and reduced trill performance and found that females moved preferentially toward the songs with elevated trill performance. Contrary to most studies investigating the behavioral responses of wild, female songbirds to variation in male song, we obtained our results without administering exogenous estradiol, which can artificially perturb the female's physiology. Our results demonstrate that the behavior of female Lincoln's sparrows is modulated by the quality of male songs to which they are exposed and that trill performance plays a significant role in this behavioral modulation. Furthermore, as the order of song quality presentation matters, it appears that recent song experience also influences female behavior.
PMCID: PMC2854529  PMID: 22476505
bird song; mate choice; Melospiza lincolnii; phonotaxis; sexual selection; song playback; trill performance; vocal performance

Results 1-6 (6)