Differential relationships between D1 and D2 dopamine receptor expression in the medial preoptic nucleus and sexually-motivated song in male European starlings (Sturnus vulgaris)

Abstract

Converging data in songbirds support a central role for the medial preoptic nucleus (POM) in motivational aspects of vocal production. Recent data suggest that dopamine in the POM plays a complex modulatory role in the production of sexually-motivated song and that an optimal level of dopamine D1 receptor stimulation is required to facilitate singing behavior. To further explore this possibility, we used quantitative real time PCR to examine relationships between mRNA expression of D1 as well as D2 receptors in the POM (and also the lateral septum and Area X) and sexually-motivated singing behavior in male European starlings. Results showed that both males with the highest and lowest D1 expression in the POM sang significantly less than males with intermediate levels of expression. Furthermore, singing behavior rose linearly in association with increasing levels of D1 expression in POM but dropped abruptly, such that individuals with D1 expression values higher than the mean sang very little. Analysis of birds with low and intermediate levels of D1 expression in POM revealed strong positive correlations between D1 expression and song but negative relationships between D2 receptor expression and song. These findings support prior work suggesting an optimal level of POM D1 receptor stimulation best facilitates sexually-motivated singing behavior. Results also suggest that D2 receptors may work in opposition to D1 receptors in POM to modify vocal production.

Prodynorphin and kappa opioid receptor mRNA expression in the brain relates to social status and behavior in male European starlings

“…Measures of plasma testosterone for these males were reported previously as part of another study, and testosterone concentrations were all in the range typical of male starlings in the breeding season [66]. We previously reported [27] that although testosterone tended to be higher in the males used in this study with nest boxes compared to those without nest boxes, this was not significant (p = 0.22 in the subset of birds from [27] reported here).…”

Contributions of testosterone and territory ownership to sexually-motivated behaviors and mRNA expression in the medial preoptic area of male European starlings

“…Correlations between courtship singing behavior, and D1 and D2 dopamine receptor expression in the mPOA also indicate that an optimal level of dopamine receptor expression in the mPOA is needed to stimulate courtship song (DeVries et al, 2015). Given that T and its metabolites can modify both opioid- and dopamine-related protein concentrations in the mPOA (Chu and Wilczynski, 2002; Eckersell et al, 1998; Watson Jr. et al, 1986), T may alter gene expression in the mPOA to prepare the brain to produce courtship behaviors.…”

Catecholaminergic Fiber Innervation of the Vocal Motor System Is Intrasexually Dimorphic in a Teleost with Alternative Reproductive Tactics

“…Since our measurements included only TH-ir somata and fibers and not specific CA receptor subtypes (which are known to generate diverse effects on physiology) [e.g., Ericsson et al 2013; Devries et al 2015], we purposefully did not predict directional differences between morphs a priori. Our results provide evidence that intrasexual differences in numbers of specific CA neurons and CA fiber innervation within the vocal motor system may provide neural substrates underlying alternative reproductive tactics in midshipman males within the summer reproductive season.…”