11 research outputs found
Individual differences in the motivation to communicate relate to levels of midbrain and striatal catecholamine markers in male European starlings
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
Measurement of Steroid Concentrations in Brain Tissue: Methodological Considerations
It is well recognized that steroids are synthesized de novo in the brain (neurosteroids). In addition, steroids circulating in the blood enter the brain. Steroids play numerous roles in the brain, such as influencing neural development, adult neuroplasticity, behavior, neuroinflammation, and neurodegenerative diseases such as Alzheimer’s disease. In order to understand the regulation and functions of steroids in the brain, it is important to directly measure steroid concentrations in brain tissue. In this brief review, we discuss methods for the detection and quantification of steroids in the brain. We concisely present the major advantages and disadvantages of different technical approaches at various experimental stages: euthanasia, tissue collection, steroid extraction, steroid separation, and steroid measurement. We discuss, among other topics, the potential effects of anesthesia and saline perfusion prior to tissue collection; microdissection via Palkovits punch; solid phase extraction; chromatographic separation of steroids; and immunoassays and mass spectrometry for steroid quantification, particularly the use of mass spectrometry for “steroid profiling.” Finally, we discuss the interpretation of local steroid concentrations, such as comparing steroid levels in brain tissue with those in the circulation (plasma vs. whole blood samples; total vs. free steroid levels). We also present reference values for a variety of steroids in different brain regions of adult rats. This brief review highlights some of the major methodological considerations at multiple experimental stages and provides a broad framework for designing studies that examine local steroid levels in the brain as well as other steroidogenic tissues, such as thymus, breast, and prostate
Rapid and Widespread Effects of 17?-Estradiol on Intracellular Signaling in the Male Songbird Brain: a Seasonal Comparison
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Rapid Effects of Estradiol on Aggression in Birds and Mice: The Fast and the Furious
Across invertebrates and vertebrates, steroids are potent signaling molecules that affect nearly every cell in the organism, including cells of the nervous system. Historically, researchers have focused on the genomic (or "nuclear-initiated") effects of steroids. However, all classes of steroids also have rapid non-genomic (or "membrane-initiated") effects, although there is far less basic knowledge of these non-genomic effects. In particular, steroids synthesized in the brain ("neurosteroids") have genomic and non-genomic effects on behavior. Here, we review evidence that estradiol has rapid effects on aggression, an important social behavior, and on intracellular signaling cascades in relevant regions of the brain. In particular, we focus on studies of song sparrows (Melospiza melodia) and Peromyscus mice, in which estradiol has rapid behavioral effects under short photoperiods only. Furthermore, in captive Peromyscus, estrogenic compounds (THF-diols) in corncob bedding profoundly alter the rapid effects of estradiol. Environmental factors in the laboratory, such as photoperiod, diet, and bedding, are critical variables to consider in experimental design. These studies are consistent with the hypothesis that locally-produced steroids are more likely than systemic steroids to act via non-genomic mechanisms. Furthermore, these studies illustrate the dynamic balance between genomic and non-genomic signaling for estradiol, which is likely to be relevant for other steroids, behaviors, and species
SEASONAL AND INDIVIDUAL VARIATION IN SINGING BEHAVIOR CORRELATES WITH ALPHA 2-NORADRENERGIC RECEPTOR DENSITY IN BRAIN REGIONS IMPLICATED IN SONG, SEXUAL, AND SOCIAL BEHAVIOR
peer reviewedIn seasonally breeding male songbirds, both the
function of song and the stimuli that elicit singing behavior
change seasonally. The catecholamine norepinephrine (NE)
modulates attention and arousal across behavioral states,
yet the role of NE in seasonally-appropriate vocal communication
has not been well-studied. The present study explored
the possibility that seasonal changes in alpha 2-noradrenergic
receptors (alpha2-R) within song control regions and brain
regions implicated in sexual arousal and social behavior contribute
to seasonal changes in song behavior in male European
starlings (Sturnus vulgaris). We quantified singing behavior
in aviary housed males under spring breeding season
conditions and fall conditions. alpha2-R were identified with the
selective ligand [3H]RX821002 using autoradiographic methods.
The densities of alpha2-R in song control regions (HVC and
the robust nucleus of the arcopallium [RA]) and the lateral
septum (LS) were lower in Spring Condition males. alpha2-R
densities in the caudal portion of the medial preoptic nucleus
(POM) related negatively to singing behavior. Testosterone
concentrations were highest in Spring Condition males and
correlated with alpha2-R in LS and POM. Results link persistent
seasonal alterations in the structure or function of male song
to seasonal changes in NE alpha2-Rs in HVC, RA, and LS. Individual
differences in alpha2-R in the POM may in part explain
individual differences in song production irrespective of the
context in which a male is singing, perhaps through NE
modification of male sexual arousal