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See detailTestosterone-induced neuroendocrine changes in the medial preoptic area precede song activation and plasticity in song control nuclei of female canaries
Shevchouk, Olesya ULg; Ghorbanpoor, Samar; Ball, Gregory F et al

in European Journal of Neuroscience (in press)

Testosterone plays a key role in the control of seasonal changes in singing behavior and its underlying neural circuitry. After administration of exogenous testosterone, song quality and song control ... [more ▼]

Testosterone plays a key role in the control of seasonal changes in singing behavior and its underlying neural circuitry. After administration of exogenous testosterone, song quality and song control nuclei volumes change over the course of weeks, but song rate increases within days. The medial preoptic nucleus (POM) controls sexual motivation and testosterone action in POM increases sexually motivated singing. Here, we investigated the time course of testosterone action in the song control nuclei and POM, at the gross anatomical and cellular level. Photosensitive female canaries were injected with BrdU to label newborn neurons. One day later they were transferred to a long day photoperiod and implanted with testosterone-filled or empty implants. Brains and blood were collected 1, 2, 9 or 21 days later. Testosterone increased POM volume within one day, whereas the volume of song control nuclei increased significantly only on day 21 even if a trend was already observed for HVC on day 9. The density of newborn neurons in HVC, labeled by Bromodeoxyuridine (BrdU) and doublecortin, was increased by testosterone on days 9 and 21 although a trend was already detectable on day 2. In POM testosterone increased the number and size of aromatase-immunoreactive neurons already after one day. This rapid action of testosterone in POM supports its proposed role in controlling singing motivation. Although testosterone increased the number of newborn neurons in HVC rapidly (9, possibly 2 days), it is unlikely that these new neurons affect singing behavior before they mature and integrate into functional circuits. [less ▲]

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See detailMultiple markers of HVC neurogenesis in the canary
Shevchouk, Olesya ULg; Ball, G.F.; Cornil, Charlotte ULg et al

in PLoS ONE (in press)

In songbirds, neurogenesis in the song control nucleus HVC is sensitive to the hormonal and social environment but the dynamics of this process is difficult to assess with a single exogenous marker of new ... [more ▼]

In songbirds, neurogenesis in the song control nucleus HVC is sensitive to the hormonal and social environment but the dynamics of this process is difficult to assess with a single exogenous marker of new neurons. We simultaneously used three independent markers to investigate HVC neurogenesis in male and female canaries. Males were castrated, implanted with testosterone and housed either alone (M), with a female (M-F) or with another male (M-M) while females were implanted with 17β- estradiol and housed with a male (F-M). All subjects received injections of the two thymidine analogues, BrdU and of EdU, respectively 21 and 10 days before brain collection. Cells containing BrdU or EdU or expressing doublecortin (DCX), which labels newborn neurons, were quantified. Social context and sex differentially affected total BrdU+, EdU+, BrdU+EdU- and DCX+ populations. M-M males had a higher density of BrdU+ cells in the ventricular zone adjacent to HVC and of EdU+ in HVC than M-F males. M birds had a higher ratio of BrdU+EdU- to EdU+ cells than M-F subjects suggesting higher survival of newer neurons in the former group. Total number of HVC DCX+ cells was lower in M-F than in M-M males. Sex differences were also dependent of the type of marker used. Several technical limitations associated with the use of these multiple markers were also identified. These results indicate that proliferation, recruitment and survival of new neurons can be independently affected by environmental conditions and effects can only be fully discerned through the use of multiple neurogenesis markers. [less ▲]

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See detailPerineuronal nets and vocal plasticity in songbirds: a proposed mechanism to explain the difference between closed-ended and open-ended learning
Cornez, Gilles ULg; Madison, F.N.; Van der Linden, A. et al

in Developmental Neurobiology (2017)

Perineuronal nets (PNN) are aggregations of chondroitin sulfate proteoglycans surrounding the soma and proximal processes of neurons, mostly GABAergic interneurons expressing parvalbumin. They limit the ... [more ▼]

Perineuronal nets (PNN) are aggregations of chondroitin sulfate proteoglycans surrounding the soma and proximal processes of neurons, mostly GABAergic interneurons expressing parvalbumin. They limit the plasticity of their afferent synaptic connections. In zebra finches PNN develop in an experience-dependent manner in the song control nuclei HVC and RA (nucleus robustus arcopallialis) when young birds crystallize their song. Because songbird species that are open-ended learners tend to recapitulate each year the different phases of song learning until their song crystallizes at the beginning of the breeding season, we tested whether seasonal changes in PNN expression would be found in the song control nuclei of a seasonally breeding species such as the European starling. Only minimal changes in PNN densities and total number of cells surrounded by PNN were detected. However, comparison of the density of PNN and of PNN surrounding parvalbumin-positive cells revealed that these structures are far less numerous in starlings that show extensive adult vocal plasticity, including learning of new songs throughout the year, than in the closed-ended learner zebra finches. Canaries that also display some vocal plasticity across season but were never formally shown to learn new songs in adulthood were intermediate in this respect. Together these data suggest that establishment of PNN around parvalbumin-positive neurons in song control nuclei has diverged during evolution to control the different learning capacities observed in songbird species. This differential expression of PNN in different songbird species could represent a key cellular mechanism mediating species variation between closed-ended and open-ended learning strategies. [less ▲]

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See detailA dynamic, sex-specific expression pattern of genes regulating thyroid hormone action in the developing zebra finch song control system
Raymaekers, S.R.; Verbeure, W.; Ter Haar, S.M. et al

in General and Comparative Endocrinology (2017), 240

The zebra finch (Taeniopygia guttata) song control system consists of several series of interconnected brain nuclei that undergo marked changes during ontogeny and sexual development, making it an excel ... [more ▼]

The zebra finch (Taeniopygia guttata) song control system consists of several series of interconnected brain nuclei that undergo marked changes during ontogeny and sexual development, making it an excel- lent model to study developmental neuroplasticity. Despite the demonstrated influence of hormones such as sex steroids on this phenomenon, thyroid hormones (THs) – an important factor in neural devel- opment and maturation – have not been studied in this regard. We used in situ hybridization to compare the expression of TH transporters, deiodinases and receptors between both sexes during all phases of song development in male zebra finch. Comparisons were made in four song control nuclei: Area X, the lateral magnocellular nucleus of the anterior nidopallium (LMAN), HVC (used as proper name) and the robust nucleus of the arcopallium (RA). Most genes regulating TH action are expressed in these four nuclei at early stages of development. However, while general expression levels decrease with age, the activating enzyme deiodinase type 2 remains highly expressed in Area X, HVC and RA in males, but not in females, until 90days post-hatch (dph), which marks the end of sensorimotor learning. Furthermore, the L-type amino acid transporter 1 and TH receptor beta show elevated expression in male HVC and RA respectively compared to surrounding tissue until adulthood. Differences compared to sur- rounding tissue and between sexes for the other TH regulators were minor. These developmental changes are accompanied by a strong local increase in vascularization in the male RA between 20 and 30 dph but not in Area X or HVC. Our results suggest that local regulation of TH signaling is an important factor in the development of the song control nuclei during the song learning phase and that TH activation by DIO2 is a key player in this process. [less ▲]

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See detailPreoptic glutamate and estradiol release during male sexual behavior
de Bournonville, Catherine ULg; de Bournonville, Marie-Pierre ULg; Aourz, Najat et al

Poster (2016, November)

Beside its long-term control by steroids, male sexual behavior is also modulated by neuroestrogens in a dynamic way (within minutes) in a number of species ranging from fishes to mammals. Studies in male ... [more ▼]

Beside its long-term control by steroids, male sexual behavior is also modulated by neuroestrogens in a dynamic way (within minutes) in a number of species ranging from fishes to mammals. Studies in male Japanese quail have also identified following exposure to a receptive female a rapid decrease in the activity of brain aromatase (AA) the enzyme responsible for the conversion of androgens into estrogens. These effects occur mainly within the medial preoptic nucleus (POM), a sexually dimorphic structure of the preoptic area that plays a key role in the activation of male sexual behavior and contains the highest AA in the brain. In vitro studies demonstrated that AA can be rapidly inhibited by calcium-dependent phosphorylations of the enzyme triggered by the activation of AMPA and kainate receptors. We confirmed here this rapid effect of glutamate on AA by injecting kainate in the POM of anesthetized males and measuring AA in the tissue after brain collection. AA in POM was inhibited in the kainate-injected hemisphere compared to the control hemisphere injected with vehicle. In a second experiment, we showed by in vivo microdialysis that glutamate is released in POM during copulation. These results thus suggest that glutamate controls dynamic changes of AA that occur in the brain during sexual interactions. To confirm that the decrease in AA leads to an actual reduction of local estradiol concentration, we quantified via microdialysis and radioimmunoassay changes in estradiol concentration in the male POM during sexual interactions with a female. Surprisingly, a dramatic elevation of estradiol was observed during copulation. Estradiol has been shown to enhance acutely male sexual motivation, therefore the function of its increase in the POM could be to maintain motivation during the entire sexual encounter. The decrease of AA observed ex vivo after copulation would then reflect a compensatory mechanism to restore baseline pre-copulatory conditions. Importantly, these results highlight that although long-term changes in AA are often used as a proxy for local estradiol concentrations, these two measures can show major short-term discrepancies possibly reflecting variations in estrogen turnover. [less ▲]

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See detailSeasonal changes and steroid control of perineuronal nets in the song control system
Cornez, Gilles ULg; Shevchouk, Olesya ULg; Madison, Farrah et al

Conference (2016, October 14)

Perineuronal nets (PNNs) are aggregations of extracellular matrix components surrounding the soma of some neurons, mainly GABAergic interneurons expressing the calcium binding protein parvalbumin (PV ... [more ▼]

Perineuronal nets (PNNs) are aggregations of extracellular matrix components surrounding the soma of some neurons, mainly GABAergic interneurons expressing the calcium binding protein parvalbumin (PV+). In mammals, the development of PNNs limits synaptogenesis around PV+ neurons and PNNs have been validated as a marker characterizing the end of critical periods for some types of learning. In oscines, song learning is limited to critical periods either during ontogeny in close-ended learners such as zebra finches or during specific phases of the annual cycle in open-ended learners such as canaries or starlings. In zebra finches, PNN expression increases when the song crystalizes and this increase is markedly inhibited if juveniles are deprived from a tutor, which is known to delay the closure of the critical period for song learning. Nothing is known however about a possible role of PNNs in adult seasonal plasticity of open-ended learners. We compared PNNs expression and their colocalization with PV+ neurons in photosensitive, photostimulated, and photorefractory starlings. Although this treatment affected as expected the testes volumes, testosterone concentrations and volumes of song control nuclei, it did not markedly change the expression of PNNs or PV+ neurons in song control or auditory nuclei. In a second experiment, brains of female canaries implanted with testosterone for 1, 2, 9, or 21 days displayed an increase of the total numbers of PV+ neurons and PNNs in HVC, the total number of PNNs in nucleus robustusarcopallialis (RA), the density of PNNs in Area X and the %PV+ neurons surrounded by PNNs in RA and Area X. Interestingly the density of PNNs in song control nuclei progressively decreases from zebra finches to canaries to starlings in parallel with the increased song plasticity in these species supporting the notion that PNNs may limit brain and thus song plasticity in a species-typical manner. [less ▲]

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See detailAromatase inhibition rapidly affects in a reversible manner distinct features of birdsong
Alward, Beau A.; de Bournonville, Catherine; Chan, Trevor T. et al

in Scientific Reports (2016)

Recent evidence has implicated steroid hormones, specifically estrogens, in the rapid modulation of cognitive processes. Songbirds have been a useful model system in the study of complex cognitive ... [more ▼]

Recent evidence has implicated steroid hormones, specifically estrogens, in the rapid modulation of cognitive processes. Songbirds have been a useful model system in the study of complex cognitive processes including birdsong, a naturally learned vocal behavior regulated by a discrete steroid-sensitive telencephalic circuitry. Singing behavior is known to be regulated by long-term actions of estrogens but rapid steroid modulation of this behavior has never been examined. We investigated if acute actions of estrogens regulate birdsong in canaries (Serinus canaria). In the morning, male canaries sing within minutes after light onset. Birds were injected with fadrozole, a potent aromatase inhibitor, or vehicle within 2-5 minutes after lights on to implement a within-subjects experimental design. This single injection of fadrozole reduced the motivation to sing as well as song acoustic stereotypy, a measure of consistency over song renditions, on the same day. By the next day, however, all song measures that were affected had returned to baseline. This study indicates that estrogens also act in a rapid fashion to regulate two distinct features of song, a learned vocal behavior. [less ▲]

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See detailEndocrine and social regulation of adult neurogenesis in songbirds.
Balthazart, Jacques ULg; Ball, Gregory F.

in Frontiers in neuroendocrinology (2016)

The identification of pronounced seasonal changes in the volume of avian song control nuclei stimulated the discovery of adult neurogenesis in songbirds as well as renewed studies in mammals including ... [more ▼]

The identification of pronounced seasonal changes in the volume of avian song control nuclei stimulated the discovery of adult neurogenesis in songbirds as well as renewed studies in mammals including humans. Neurogenesis in songbirds is modulated by testosterone and other factors such as photoperiod, singing activity and social environment. Adult neurogenesis has been widely studied by labeling, with tritiated thymidine or its analog BrdU, cells duplicating their DNA in anticipation of their last mitotic division and following their fate as new neurons. New methods based on endogenous markers of cell cycling or of various stages of neuronal life have allowed for additional progress. In particular immunocytochemical visualization of the microtubule-associated protein doublecortin has provided an integrated view of neuronal replacement in the song control nucleus HVC. Multiple questions remain however concerning the specific steps in the neuronal life cycle that are modulated by various factors and the underlying cellular mechanisms. [less ▲]

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See detailNon-ovarian aromatization is required to activate female sexual motivation in testosterone-treated ovariectomized quail
de Bournonville, Catherine; Balthazart, Jacques ULg; Ball, Gregory et al

in Hormones and Behavior (2016), 83

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See detailPleiotropic Control by Testosterone of a Learned Vocal Behavior and Its Underlying Neuroplasticity(1,2,3).
Alward, Beau A.; Madison, Farrah N.; Parker, Shannon E. et al

in eNeuro (2016), 3(1),

Steroid hormones coordinate multiple aspects of behavior and physiology. The same hormone often regulates different aspects of a single behavior and its underlying neuroplasticity. This pleiotropic ... [more ▼]

Steroid hormones coordinate multiple aspects of behavior and physiology. The same hormone often regulates different aspects of a single behavior and its underlying neuroplasticity. This pleiotropic regulation of behavior and physiology is not well understood. Here, we investigated the orchestration by testosterone (T) of birdsong and its neural substrate, the song control system. Male canaries were castrated and received stereotaxic implants filled with T in select brain areas. Implanting T solely in the medial preoptic nucleus (POM) increased the motivation to sing, but did not enhance aspects of song quality such as acoustic structure and stereotypy. In birds implanted with T solely in HVC (proper name), a key sensorimotor region of the song control system, little or no song was observed, similar to castrates that received no T implants of any sort. However, implanting T in HVC and POM simultaneously rescued all measures of song quality. Song amplitude, though, was still lower than what was observed in birds receiving peripheral T treatment. T in POM enhanced HVC volume bilaterally, likely due to activity-dependent changes resulting from an enhanced song rate. T directly in HVC, without increasing song rate, enhanced HVC volume on the ipsilateral side only. T in HVC enhanced the incorporation and recruitment of new neurons into this nucleus, while singing activity can independently influence the incorporation of new neurons into HVC. These results have broad implications for how steroid hormones integrate across different brain regions to coordinate complex social behaviors. [less ▲]

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See detailSex differences in partner preferences in humans and animals.
Balthazart, Jacques ULg

in Philosophical transactions of the Royal Society of London. Series B, Biological sciences (2016), 371(1688),

A large number of morphological, physiological and behavioural traits are differentially expressed by males and females in all vertebrates including humans. These sex differences, sometimes, reflect the ... [more ▼]

A large number of morphological, physiological and behavioural traits are differentially expressed by males and females in all vertebrates including humans. These sex differences, sometimes, reflect the different hormonal environment of the adults, but they often remain present after subjects of both sexes are placed in the same endocrine conditions following gonadectomy associated or not with hormonal replacement therapy. They are then the result of combined influences of organizational actions of sex steroids acting early during development, or genetic differences between the sexes, or epigenetic mechanisms differentially affecting males and females. Sexual partner preference is a sexually differentiated behavioural trait that is clearly controlled in animals by the same type of mechanisms. This is also probably true in humans, even if critical experiments that would be needed to obtain scientific proof of this assertion are often impossible for pragmatic or ethical reasons. Clinical, epidemiological and correlative studies provide, however, converging evidence strongly suggesting, if not demonstrating, that endocrine, genetic and epigenetic mechanisms acting during the pre- or perinatal life control human sexual orientation, i.e. homosexuality versus heterosexuality. Whether they interact with postnatal psychosexual influences remains, however, unclear at present. [less ▲]

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See detailEstrogen Receptor β Activation Rapidly Modulates Male Sexual Motivation through the Transactivation of Metabotropic Glutamate Receptor 1a
Seredynski, Aurore L; Balthazart, Jacques ULg; Ball, Gregory F et al

in Journal of Neuroscience (2015), 35(38), 13110-23

In addition to the transcriptional activity of their liganded nuclear receptors, estrogens, such as estradiol (E2), modulate cell functions, and consequently physiology and behavior, within minutes ... [more ▼]

In addition to the transcriptional activity of their liganded nuclear receptors, estrogens, such as estradiol (E2), modulate cell functions, and consequently physiology and behavior, within minutes through membrane-initiated events. The membrane-associated receptors (mERs) underlying the acute effects of estrogens on behavior have mostly been documented in females where active estrogens are thought to be of ovarian origin. We determined here, by acute intracerebroventricular injections of specific agonists and antagonists, the type(s) of mERs that modulate rapid effects of brain-derived estrogens on sexual motivation in male Japanese quail. Brain aromatase blockade acutely inhibited sexual motivation. Diarylpropionitrile (DPN), an estrogen receptor β (ERβ)-specific agonist, and to a lesser extent 17α-estradiol, possibly acting through ER-X, prevented this effect. In contrast, drugs targeting ERα (PPT and MPP), GPR30 (G1 and G15), and the Gq-mER (STX) did not affect sexual motivation. The mGluR1a antagonist LY367385 significantly inhibited sexual motivation but mGluR2/3 and mGluR5 antagonists were ineffective. LY367385 also blocked the behavioral restoration induced by E2 or DPN, providing functional evidence that ERβ interacts with metabotropic glutamate receptor 1a (mGluR1a) signaling to acutely regulate male sexual motivation. Together these results show that ERβ plays a key role in sexual behavior regulation and the recently uncovered cooperation between mERs and mGluRs is functional in males where it mediates the acute effects of estrogens produced centrally in response to social stimuli. The presence of an ER-mGluR interaction in birds suggests that this mechanism emerged relatively early in vertebrate history and is well conserved. Significance statement: The membrane-associated receptors underlying the acute effects of estrogens on behavior have mostly been documented in females, where active estrogens are thought to be of ovarian origin. Using acute intracerebroventricular injections of specific agonists and antagonists following blockade of brain aromatase, we show here that brain-derived estrogens acutely facilitate male sexual motivation through the activation of estrogen receptor β interacting with the metabotropic glutamate receptor 1a. This behavioral effect occurring within minutes provides a mechanistic explanation of how an estrogen receptor not intrinsically coupled to intracellular effectors can signal from the membrane to govern behavior in a very rapid fashion. It suggests that different subtypes of estrogen receptors could regulate the motivation versus performance aspects of behavior. [less ▲]

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See detailAnatomically discrete sex differences in neuroplasticity in zebra finches as reflected by perineuronal nets.
Cornez, Gilles ULg; Ter Haar, Sita M.; Cornil, Charlotte ULg et al

in PloS one (2015), 10(4), 0123199

Large morphological sex differences in the vertebrate brain were initially identified in song control nuclei of oscines. Besides gross differences between volumes of nuclei in males and females, sex ... [more ▼]

Large morphological sex differences in the vertebrate brain were initially identified in song control nuclei of oscines. Besides gross differences between volumes of nuclei in males and females, sex differences also concern the size and dendritic arborization of neurons and various neurochemical markers, such as the calcium-binding protein parvalbumin (PV). Perineuronal nets (PNN) of the extracellular matrix are aggregates of different compounds, mainly chondroitin sulfate proteoglycans, that surround subsets of neurons, often expressing PV. PNN develop in zebra finches song control nuclei around the end of the sensitive period for song learning and tutor deprivation, known to delay the end of the song learning sensitive period, decreases the numbers of PNN in HVC. We demonstrate here the existence in zebra finches of a major sex difference (males > females) affecting the number of PNN (especially those surrounding PV-positive cells) in HVC and to a smaller extent the robust nucleus of the arcopallium, RA, the two main nuclei controlling song production. These differences were not present in Area X and LMAN, the lateral magnocellular nucleus of the anterior nidopallium. A dense expression of material immunoreactive for chondroitin sulfate was also detected in several nuclei of the auditory and visual pathways. This material was often organized in perineuronal rings but quantification of these PNN did not reveal any sex difference with the exception that the percentage of PNN surrounding PV-ir cells in the dorsal lateral mesencephalic nucleus, MLd, was larger in females than in males, a sex difference in the opposite direction compared to what is seen in HVC and RA. These data confirm and extend previous studies demonstrating the sex difference affecting PNN in HVC-RA by showing that this sex difference is anatomically specific and does not concern visual or auditory pathways. [less ▲]

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See detailThe dual action of estrogen hypothesis
Cornil, Charlotte ULg; Ball, Gregory F.; Balthazart, Jacques ULg

in Trends in Neurosciences (2015), 38(7), 408-16

Estradiol (E2) can act in the brain in a relatively fast manner (i.e., seconds to minutes) usually through signaling initiated at the cell membrane. Brain-derived E2 has thus been considered as another ... [more ▼]

Estradiol (E2) can act in the brain in a relatively fast manner (i.e., seconds to minutes) usually through signaling initiated at the cell membrane. Brain-derived E2 has thus been considered as another type of neurotransmitter. Recent work found that behaviors indicative of male sexual motivation are activated by estrogenic metabolites of testosterone (T) in a fast manner, while sexual performance (copulatory behavior per se) is regulated by brain E2 in a slower manner via nucleus-initiated actions. This functional division between these two types of action appears to generalize to other behavioral systems regulated by E2. We propose the dual action of estrogen hypothesis to explain this functional distinction between these two different modes of action. [less ▲]

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See detailLocal modulation of steroid action: rapid control of enzymatic activity.
Charlier, Thierry D.; Cornil, Charlotte ULg; Patte-Mensah, Christine et al

in Frontiers in neuroscience (2015), 9

Estrogens can induce rapid, short-lived physiological and behavioral responses, in addition to their slow, but long-term, effects at the transcriptional level. To be functionally relevant, these effects ... [more ▼]

Estrogens can induce rapid, short-lived physiological and behavioral responses, in addition to their slow, but long-term, effects at the transcriptional level. To be functionally relevant, these effects should be associated with rapid modulations of estrogens concentrations. 17beta-estradiol is synthesized by the enzyme aromatase, using testosterone as a substrate, but can also be degraded into catechol-estrogens via hydroxylation by the same enzyme, leading to an increase or decrease in estrogens concentration, respectively. The first evidence that aromatase activity (AA) can be rapidly modulated came from experiments performed in Japanese quail hypothalamus homogenates. This rapid modulation is triggered by calcium-dependent phosphorylations and was confirmed in other tissues and species. The mechanisms controlling the phosphorylation status, the targeted amino acid residues and the reversibility seem to vary depending of the tissues and is discussed in this review. We currently do not know whether the phosphorylation of the same amino acid affects both aromatase and/or hydroxylase activities or whether these residues are different. These processes provide a new general mechanism by which local estrogen concentration can be rapidly altered in the brain and other tissues. [less ▲]

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See detailMate selection, Sexual orientation and Pair bonding
Balthazart, Jacques ULg; Young, Larry J.

in Plant, Tony M.; Zelenik, Anthony J. (Eds.) Knobil and Neill's Physiology of Reproduction (2015)

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See detailReversing song behavior phenotype: Testosterone driven induction of singing and measures of song quality in adult male and female canaries (Serinus canaria)
Madison, Farrah N.; Rouse, Melvin L. Jr; Balthazart, Jacques ULg et al

in General and comparative endocrinology (2015), 215

In songbirds, such as canaries (Serinus canaria), the song control circuit has been shown to undergo a remarkable change in morphology in response to exogenous testosterone (T). It is also well ... [more ▼]

In songbirds, such as canaries (Serinus canaria), the song control circuit has been shown to undergo a remarkable change in morphology in response to exogenous testosterone (T). It is also well established that HVC, a telencephalic nucleus involved in song production, is significantly larger in males than in females. T regulates seasonal changes in HVC volume in males, and exposure to exogenous T in adult females increases HVC volume and singing activity such that their song becomes more male-like in frequency and structure. However, whether there are sex differences in the ability of T to modulate changes in the song system and song behavior has not been investigated in canaries. In this study, we compared the effects of increasing doses of T on singing and song control nuclei volumes in adult male and female American Singer canaries exposed to identical environmental conditions. Males were castrated and all birds were placed on short days (8L:16D) for 8weeks. Males and females were implanted either with a 2, 6 or 12mm long Silastic implant filled with crystalline T or an empty 12mm implant as control. Birds were then housed individually in sound-attenuated chambers. Brains were collected from six birds from each group after 1week or 3weeks of treatment. Testosterone was not equally effective in increasing singing activity in both males and females. Changes in song quality and occurrence rate took place after a shorter latency in males than in females; however, females did undergo marked changes in a number of measures of song behavior if given sufficient time. Males responded with an increase in HVC volume at all three doses. In females, T-induced changes in HVC volume only had limited amplitude and these volumes never reached male-typical levels, suggesting that there are sex differences in the neural substrate that responds to T. [less ▲]

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See detailMale song quality modulates c-Fos expression in the auditory forebrain of the female canary.
Monbureau, Marie; Barker, Jennifer M.; Leboucher, Gerard et al

in Physiology & behavior (2015), 147

In canaries, specific phrases of male song (sexy songs, SS) that are difficult to produce are especially attractive for females. Females exposed to SS produce more copulation displays and deposit more ... [more ▼]

In canaries, specific phrases of male song (sexy songs, SS) that are difficult to produce are especially attractive for females. Females exposed to SS produce more copulation displays and deposit more testosterone into their eggs than females exposed to non-sexy songs (NS). Increased expression of the immediate early genes c-Fos or zenk (a.k.a. egr-1) has been observed in the auditory forebrain of female songbirds hearing attractive songs. C-Fos immunoreactive (Fos-ir) cell numbers were quantified here in the brain of female canaries that had been collected 30min after they had been exposed for 60min to the playback of SS or NS or control white noise. Fos-ir cell numbers increased in the caudomedial mesopallium (CMM) and caudomedial nidopallium (NCM) of SS birds as compared to controls. Song playback (pooled SS and NS) also tended to increase average Fos-ir cell numbers in the mediobasal hypothalamus (MBH) but this effect did not reach full statistical significance. At the individual level, Fos expression in CMM was correlated with its expression in NCM and in MBH but also with the frequency of calls that females produced in response to the playbacks. These data thus indicate that male songs of different qualities induce a differential metabolic activation of NCM and CMM. The correlation between activation of auditory regions and of the MBH might reflect the link between auditory stimulation and changes in behavior and reproductive physiology. [less ▲]

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See detailSeasonal changes in the neuroendocrine system: Introduction to the special issue.
Ball, Gregory F.; Balthazart, Jacques ULg

in Frontiers in neuroendocrinology (2015), 37

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See detailGlutamate controls brain estrogen synthesis during sexual interactions
de Bournonville, Catherine ULg; Aourz, Najat; Van Eeckhaut, Ann et al

Poster (2014, November 17)

Besides their long-lasting effects mediated by a modulation of gene transcription, brain-derived estrogens can rapidly regulate (within minutes) reproductive behaviors. In vitro, the activity of aromatase ... [more ▼]

Besides their long-lasting effects mediated by a modulation of gene transcription, brain-derived estrogens can rapidly regulate (within minutes) reproductive behaviors. In vitro, the activity of aromatase (AA), the enzyme responsible for the conversion of androgens into estrogens, is also regulated on a similar short time-scale, via phosphorylation of the enzyme resulting from changes in neuronal activity or glutamate release. Acute changes in AA have been documented ex vivo in specific brain regions following exposure to social or stressful stimuli but the mechanism underlying these regulations is not known. To investigate whether glutamate is implicated in these rapid changes in AA, male quail received a unilateral injection of kainate in the medial preoptic nucleus (POM). The left and right preoptic areas were collected 20 min later and assayed separately by the tritiated water technique for AA. As shown previously in preoptic explants maintained in vitro, AA was downregulated in the kainate-injected hemisphere as compared to the non-injected side. To determine whether the decline in AA detected in the POM after a sexual interaction could be mediated by an increased release of glutamate in this region, extracellular glutamate concentration was measured by in vivo microdialysis with a probe implanted in the POM of sexually mature males. Dialysate was collected every 3 minutes over three periods of 15 min when the male was (1) alone, (2) allowed to freely copulate with a female and (3) alone again. A transient rise in extracellular glutamate concentration was observed specifically and immediately after the expression of cloacal contact movements, when semen is transferred to the female. Glutamate returned to a basal level after the female was removed. Together, these results indicate that the mechanism of acute regulation of aromatase activity by glutamate identified in vitro is potentially responsible for the acute regulation of the enzyme observed in vivo following copulation. As rapid changes in brain estrogen synthesis and its actions are apparently related to the control of sexual motivation rather than sexual performance, follow up experiments should now determine whether the release of glutamate in the POM occurs in parallel with an increase in motivation or follows the termination of the copulatory sequence. [less ▲]

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