Estrogenic regulation of dopaminergic neurons in the opportunistically breeding zebra finch

Abstract

Steroid-induced changes in dopaminergic activity underlie many correlations between gonadal hormones and social behaviors. However, the effects of steroid hormones on the various behaviorally relevant dopamine cell groups remain unclear, and ecologically relevant species differences remain virtually unexplored. We examined the effects of estradiol (E2) manipulations on dopamine (DA) neurons of male and female zebra finches (Taeniopygia guttata), focusing on numbers of tyrosine hydroxylase-immunoreactive (TH-ir) cells in the A8–A15 cell groups, and on TH colocalization with Fos, conducted in the early A.M., in order to quantify basal transcriptional activity. TH is the rate-limiting enzyme for catecholamine synthesis, and specifically DA in the A8–A15 cell groups. In contrast to other examined birds and mammals, reducing E2 levels with the aromatase-inhibitor Letrozole failed to alter TH-ir neuron numbers within the ventral tegmental area (VTA; A10), while increasing neuron numbers in the central gray (CG; A11) and caudal midbrain A8 populations. Consistent with findings in other birds, but not mammals, we also found no effects of E2 manipulations (Letrozole or Letrozole plus E2 replacement) on TH-Fos colocalization in any location. In accordance with previous observations in both mammals and birds, E2 treatment decreased the number of TH-ir neurons in the A12 population of the tuberal hypothalamus, a cell group that inhibits the release of prolactin. In general, males and females exhibited similar TH-ir neuron numbers, although males exhibited significantly more TH-ir neurons in the A11 CG population than did females. These results suggest partial variability in E2 regulation of DA across species.

Testosterone alters genomic responses to song and monoaminergic innervation of auditory areas in a seasonally breeding songbird

“…E2 has been reported to enhance monoaminergic activity (Sumner and Fink, ; McQueen et al, ; Cornil et al, ; Matragrano et al, ; cf. Kabelik et al, ). In contrast, androgens seem to have an inhibitory effect.…”

A Role for Nonapeptides and Dopamine in Nest‐Building Behaviour

“…Sections were then moved into the primary Fos antibody (rabbit polyclonal anti-Fos K-25, sc-253, Santa Cruz Biotechnology, Santa Cruz, CA, USA, dilution 1 : 10 000) in 10% normal goat serum in PBT and incubated for 21 h at 4 °C. The K-25 Fos antibody has been extensively used in zebra finches (29) and validated in songbirds (30). Sections were then rinsed three times in PBT and incubated in biotinylated goat anti-rabbit secondary antibody (diluted 1 : 250 in PBT; Vector Laboratories) for 1 h at room temperature.…”

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

“…However, relationships between TH-ir and circuitry underlying alternative male reproductive behavior are unexplored. Brain CA nuclei and fiber densities are known to be regulated by steroid hormones [Wilczynski et al, 2003; LeBlanc et al, 2007; Kabelik et al, 2011; Matragrano et al, 2013; Barth et al, 2015], and forebrain dopaminergic neurons in midshipman are located in areas replete with androgen and estrogen receptors and aromatase (estrogen synthase) [Forlano et al, 2001, 2005, 2010, 2014]. Importantly, steroid hormone profiles, estrogen receptor expression, as well as aromatase activity and expression are different between male morphs [Brantley et al, 1993; Schlinger et al, 1999; Forlano and Bass, 2005; Fergus and Bass 2013], which may regulate morph differences in CA neuron number and/or their innervation patterns.…”