Publications of Jacques Balthazart
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See detailSite-specific effects of aromatase inhibition on the activation of male sexual behavior in male Japanese quail (Coturnix japonica)
de Bournonville, Marie-Pierre ULiege; Vandries, Laura ULiege; Ball, Gregory et al

in Hormones and Behavior (2019), 108

Aromatization within the medial preoptic nucleus (POM) is essential for the expression of male copulatory behavior in Japanese quail. However, several nuclei within the social behavior network (SBN) also ... [more ▼]

Aromatization within the medial preoptic nucleus (POM) is essential for the expression of male copulatory behavior in Japanese quail. However, several nuclei within the social behavior network (SBN) also express aromatase. Whether aromatase in these loci participates in the behavioral activation is not known. Castrated male Japanese quail were implanted with 2 subcutaneous Silastic capsules filled with crystalline testosterone and with bilateral stereotaxic implants filled with the aromatase inhibitor Vorozole targeting the POM, the bed nucleus of the stria terminalis (BST) or the ventromedial nucleus of the hypothalamus (VMN). Control animals were implanted with testosterone and empty bilateral stereotaxic implants. Starting 2 days after the surgery, subjects were tested for the expression of consummatory sexual behavior (CSB) every other day for a total of 10 tests. They were also tested once for appetitive sexual behavior (ASB) as measured by the rhythmic cloacal sphincter movements displayed in response to the visual presentation of a female. CSB was drastically reduced when the Vorozole implants were localized in the POM, but not in the BST nor in the VMN. Birds with implants in the BST showed a longer latency to show CSB in the first 6 tests than controls, suggesting a role of the BST in the acquisition of the full copulatory ability. ASB was not significantly affected by aromatase blockade in any region. These data confirm the key role played by the POM in the control of male sexual behavior and suggest a minor role for aromatization in the BST or VMN. [less ▲]

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See detailExpérimentation animale: la recette d'une polémique scientifique
Muraille, Eric; de kerchove, Alban; Muylkens, Benoit et al

Article for general public (2018)

La majorité du grand public accepte l’expérimentation animale à condition que celle-ci contribue à l’amélioration de la santé humaine et qu’aucune autre alternative n’existe. En face, les opposants ... [more ▼]

La majorité du grand public accepte l’expérimentation animale à condition que celle-ci contribue à l’amélioration de la santé humaine et qu’aucune autre alternative n’existe. En face, les opposants décrédibilisent la recherche et stigmatise une profession à des fins idéologiques. Relevé de leurs arguments. [less ▲]

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See detailLa souris, le patient, et le faux expert. Décryptage d'une mystification.
Bakker, Julie ULiege; Balthazart, Jacques ULiege; Baron, Frédéric ULiege et al

Article for general public (2018)

La recherche sur animaux est actuellement encadrée de façon stricte en Wallonie comme dans toute l'Union Européenne (voir l'article de Marc Vandenheede publié dans le Vif). Cette législation et les ... [more ▼]

La recherche sur animaux est actuellement encadrée de façon stricte en Wallonie comme dans toute l'Union Européenne (voir l'article de Marc Vandenheede publié dans le Vif). Cette législation et les contrôles qui y sont associés induisent de nombreuses contraintes pratiques, des charges administratives et des coûts financiers importants que les chercheurs seraient certainement heureux d'éviter s'il existait une alternative à l'expérimentation animale. [less ▲]

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See detailAnalyse détaillée de la seconde version de l’avant-projet de Code du bien-être animal wallon. Lecture commentée au 21/03/2018 du Chapitre 8 (Expérimentation animale)
Drion, Pierre ULiege; Corhay, Albert ULiege; Haubruge, Eric ULiege et al

Report (2018)

La compétence « bien-être animal », auparavant fédérale, a été régionalisée en juillet 2014. Ce projet de code vise à remplacer les dispositions légales en vigueur (la Loi de 1984 telle que modifiée par ... [more ▼]

La compétence « bien-être animal », auparavant fédérale, a été régionalisée en juillet 2014. Ce projet de code vise à remplacer les dispositions légales en vigueur (la Loi de 1984 telle que modifiée par les décrets du Gouvernement wallon). Certains éléments sont repris tels quels de la Directive 2010/63. Cela est nécessaire car la Directive européenne en tant que telle n’a pas de force obligatoire en Belgique. Elle doit être transcrite par un instrument législatif (avant, la Loi de 1984 et ses modifications, aujourd’hui, le projet de code pour la Région wallonne). Certains aspects semblent flous, mais renvoient à des dispositions que le Gouvernement doit encore prendre (au travers d’arrêtés du Gouvernement wallon, comme le faisaient avant les nombreux arrêtés royaux et du gouvernement qui réglementent la matière). Les arrêtés d’exécution devront obligatoirement tenir compte de la Directive européenne et s’inspirer de dispositions actuellement en vigueur. [less ▲]

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See detailRapid changes in auditory processing in songbirds following acute aromatase inhibition as assessed by fMRI
Van der Linden, A.; Balthazart, Jacques ULiege

in Hormones and Behavior (2018), 104

Contribution to Special Issue on Fast effects of steroids. This review introduces functional MRI (fMRI) as an outstanding tool to assess rapid effects of sex steroids on auditory processing in seasonal ... [more ▼]

Contribution to Special Issue on Fast effects of steroids. This review introduces functional MRI (fMRI) as an outstanding tool to assess rapid effects of sex steroids on auditory processing in seasonal songbirds. We emphasize specific advantages of this method as compared to other more conventional and invasive methods used for this purpose and summarize an exemplary auditory fMRI study performed on male starlings exposed to different types of starling song before and immediately after the inhibition of aromatase activity by an i.p. injection of Vorozole™. We describe how most challenges that relate to the necessity to anesthetize subjects and minimize image- and sound-artifacts can be overcome in order to obtain a voxel-based 3D-representation of changes in auditory brain activity to various sound stimuli before and immediately after a pharmacologically-induced depletion of endogenous estrogens. Analysis of the fMRI data by assumption-free statistical methods identified fast specific changes in activity in the auditory brain regions that were stimulus-specific, varying over different seasons, and in several instances lateralized to the left side of the brain. This set of results illustrates the unique features of fMRI that provides opportunities to localize and quantify the brain responses to rapid changes in hormonal status. fMRI offers a new image-guided research strategy in which the spatio-temporal profile of fast neuromodulations can be identified and linked to specific behavioral inputs or outputs. This approach can also be combined with more localized invasive methods to investigate the mechanisms underlying the observed neural changes. © 2018 Elsevier Inc. [less ▲]

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See detailDifferential control of appetitive and consummatory sexual behavior by neuroestrogens in male quail
Cornil, Charlotte ULiege; Ball, Gregory; Balthazart, Jacques ULiege

in Hormones and Behavior (2018), 104

Estrogens exert pleiotropic effects on multiple physiological and behavioral traits including sexual behavior. These effects are classically mediated via binding to nuclear receptors and subsequent ... [more ▼]

Estrogens exert pleiotropic effects on multiple physiological and behavioral traits including sexual behavior. These effects are classically mediated via binding to nuclear receptors and subsequent regulation of target gene transcription. Estrogens also affect neuronal activity and cell-signaling pathways via faster, membrane-initiated events. Although the distinction between appetitive and consummatory aspects of sexual behavior has been criticized, this distinction remains valuable in that it facilitates the causal analysis of certain behavioral systems. Effects of neuroestrogens produced by neuronal aromatization of testosterone on copulatory performance (consummatory aspect) and on sexual motivation (appetitive aspect) are described in male quail. The central administration of estradiol rapidly increases expression of sexual motivation, as assessed by two measures of sexual motivation produced in response to the visual presentation of a female but not sexual performance in male Japanese quail. This effect is mimicked by membrane-impermeable analogs of estradiol, indicating that it is initiated at the cell membrane. Conversely, blocking the action of estrogens or their synthesis by a single in- tracerebroventricular injection of estrogen receptor antagonists or aromatase inhibitors, respectively, decreases sexual motivation within minutes without affecting performance. The same steroid has thus evolved com- plementary mechanisms to regulate different behavioral components (motivation vs. performance) in distinct temporal domains (long- vs. short-term) so that diverse reproductive activities can be properly coordinated. Changes in preoptic aromatase activity and estradiol as well as glutamate concentrations are observed during or immediately after copulation. The interaction between these neuroendocrine/neurochemical changes and their functional significance is discussed. [less ▲]

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See detailRapid effects of steroids in the brain: Introduction to special issue
Remage-Healey, L.; Choleris, E.; Balthazart, Jacques ULiege

in Hormones and Behavior (2018), 104

[No abstract available]

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See detailThe regulation of birdsong by testosterone: Multiple time-scales and multiple sites of action
Alward, Beau; Cornil, Charlotte ULiege; Balthazart, Jacques ULiege et al

in Hormones and Behavior (2018), 104

Sex steroid hormones act during early development to shape the circuitry upon which these same hormones act in adulthood to control behavioral responses to various stimuli. The “organizational” vs ... [more ▼]

Sex steroid hormones act during early development to shape the circuitry upon which these same hormones act in adulthood to control behavioral responses to various stimuli. The “organizational” vs. “activational” dis- tinction was proposed to explain this temporal difference in hormone action. In both of these cases steroids were thought to act genomically over a time-scale of days to weeks. However, sex steroids can affect behavior over short (e.g., seconds or minutes) time-scales. Here, we discuss how testosterone controls birdsong via actions at different sites and over different time-scales, with an emphasis on this process in canaries (Serinus canaria). Our work shows that testosterone in the medial preoptic nucleus regulates the motivation to sing, but not aspects of song performance. Instead, different aspects of song performance are regulated by long-term actions of testos- terone in steroid-sensitive cortical-like brain regions and the syrinx, the avian vocal production organ. On the other hand, acute aromatase inhibition rapidly reduces the availability of estrogens and this reduction is cor- related with reductions in the motivation to sing and song performance. Thus, testosterone and its estrogenic metabolites regulate distinct features of birdsong depending on the site and temporal window of action. The number of brain areas expressing androgen receptors is higher in species producing learned vocalization as compared to species that produce unlearned calls. An appealing scenario is that rapid effects of steroids in specific brain regions is a derived trait secondary to the widespread genomic effects of steroids in systems where steroids coordinate morphological, physiological, and behavioral traits. [less ▲]

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See detailSteroids and the brain: 50 years of research, conceptual shifts and the ascent of non-classical and membrane-initiated actions
Balthazart, Jacques ULiege; Choleris, E.; Remage-Healey, L.

in Hormones and Behavior (2018), 99

This brief commentary reviews key steps in the history of steroid endocrinology that have resulted in important conceptual shifts. Our understanding of the “Fast Effects of Steroids” now reflect ... [more ▼]

This brief commentary reviews key steps in the history of steroid endocrinology that have resulted in important conceptual shifts. Our understanding of the “Fast Effects of Steroids” now reflect substantial progress, including the major concept that steroids act rapidly on a variety of physiological and behavioral responses, via mechanisms that are too fast to be fully accounted for by classical receptor-dependent regulation of gene transcription. Several so-called ‘non-classical’ mechanisms have been identified and include binding to membrane receptors and regulating non genomic signaling cascades. We survey the discovery of steroids, the initial characterization of their intracellular receptors, key progress in the understanding of the genomic effects of steroids and then the progressive discovery of the rapid non-classical and membrane-initiated actions of steroids. Foundational discoveries about brain steroid synthesis in neural processes and terminals has converged with emerging evidence for the rapid actions of steroids on brain and behavior. Had the rapid effects of steroids in the central nervous system been discovered first, these molecules would likely now be considered as a class of neurotransmitter. © 2018 Elsevier Inc. [less ▲]

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See detailTiming of perineuronal nets development in the zebra finch song control system correlates with developmental song learning
Cornez, Gilles ULiege; Jonckers, Elisabeth; ter Haar, Sita et al

in Proceedings of the Royal Society. Biological Sciences (2018)

The appearance of perineuronal nets (PNN) represents one of the mechanisms that contribute to the closing of sensitive periods for neural plasticity. This relationship has mostly been studied in the ... [more ▼]

The appearance of perineuronal nets (PNN) represents one of the mechanisms that contribute to the closing of sensitive periods for neural plasticity. This relationship has mostly been studied in the ocular dominance model in rodents. Previous studies also indicated that PNN might control neural plasticity in the song control system (SCS) of songbirds. To further elucidate this relationship, we quantified PNN expression and their localization around parvalbumin interneurons at key time-points during ontogeny in both male and female zebra finches and correlated these data with the well-described development of song in this species. We also extended these analyses to the auditory system. The development of PNN during ontogeny correlated with song crystallization although the timing of PNN appearance in the four main telencephalic song control nuclei slightly varied between nuclei in agreement with the established role these nuclei play during song learning. Our data also indicate that very few PNN develop in the secondary auditory forebrain areas even in adult birds, which may allow constant adaptation to a changing acoustic environment by allowing synaptic reorganization during adulthood. [less ▲]

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See detailBehavioral evidence for sex steroids hypersensitivity in castrated male canaries
Shevchouk, Olesya ULiege; Ghorbanpoor, Samar; Smith, Ed et al

in Hormones and Behavior (2018)

In seasonally breeding songbirds such as canaries, singing behavior is predominantly under the control of tes- tosterone and its metabolites. Short daylengths in the fall that break photorefractoriness ... [more ▼]

In seasonally breeding songbirds such as canaries, singing behavior is predominantly under the control of tes- tosterone and its metabolites. Short daylengths in the fall that break photorefractoriness are followed by in- creasing daylengths in spring that activate singing via both photoperiodic and hormonal mechanisms. However, we observed in a group of castrated male Fife fancy canaries maintained for a long duration under a short day photoperiod a large proportion of subjects that sang at high rates. This singing rate was not correlated with variation in the low circulating concentrations of testosterone. Treatment of these actively singing castrated male canaries with a combination of an aromatase inhibitor (ATD) and an androgen receptor blocker (flutamide) only marginally decreased this singing activity as compared to control untreated birds and did not affect various measures of song quality. The volumes of HVC and of the medial preoptic nucleus (POM) were also unaffected by these treatments but were relatively large and similar to volumes in testosterone-treated males. In contrast, peripheral androgen-sensitive structures such as the cloacal protuberance and syrinx mass were small, similar to what is observed in castrates. Together these data suggest that after a long-term steroid deprivation singing behavior can be activated by very low concentrations of testosterone. Singing normally depends on the acti- vation by testosterone and its metabolites of multiple downstream neurochemical systems such as catechola- mines, nonapeptides or opioids. These transmitter systems might become hypersensitive to steroid action after long term castration as they probably are at the end of winter during the annual cycle in seasonally breeding temperate zone species. [less ▲]

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See detailL’expérimentation animale reste indispensable (OPINION)
Amorim, Christiani; Andris, Fabienne; Arckens, Lut et al

Article for general public (2017)

Trop fréquemment, l’expérimentation animale est présentée comme une pratique archaïque. Elle a bien changé. Et 100 % des patients traités le sont grâce aux concepts et techniques développés grâce à elle.

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See detailRapid changes in preoptic estradiol concentration during male sexual behavior
de Bournonville, Marie-Pierre ULiege; de Bournonville, Catherine; Ball, Gregory et al

Poster (2017, November 11)

Estrogens such as estradiol (E2) exert pleiotropic effects on physiological and behavioral responses such as neuroprotection, aggression or reproduction. Estrogens derived from local brain synthesis ... [more ▼]

Estrogens such as estradiol (E2) exert pleiotropic effects on physiological and behavioral responses such as neuroprotection, aggression or reproduction. Estrogens derived from local brain synthesis (neuroestrogens) are critical for the regulation of different functions including the control of male sexual behavior. Classically, E2 acts through effects initiated in the nucleus to regulate male sexual function. Along with these long-term effects, E2 also acts rapidly (within minutes) via membrane-initiated events. These effects are thought to depend on short-term variations in the local production of estrogens, through rapid fluctuations of the enzymatic activity of brain aromatase. In Japanese quail, rapid modulations of brain aromatase activity (AA) have been reported after sexual interactions or exposure to an acute stress. These changes take place mainly in the medial preoptic nucleus (POM), a sexually differentiated structure that plays a key role in the control of male sexual behavior and where aromatase is densely expressed. Yet, it has recently been shown that, in the short term, AA does not always reflect local E2 concentration. This study was designed to determine by in vivo microdialysis whether local E2 concentrations fluctuate during sexual interactions and test whether these changes parallel the decrease in AA observed ex vivo after copulation. We first conducted a series of experiments to validate the microdialysis and E2 assay. When dialysis probes were placed in successive baths containing known increasing amounts of E2, proportional changes in E2 concentration were measured in the dialysate. Moreover, a rise in E2 concentration was detected after in vivo retrodialysis of testosterone only if the probe was located within the POM and, after a peripheral injection of E2, a sharp rise of E2 was detected regardless of the probe location. Together these results show that in vivo microdialysis is a valid method to assess endogenous fluctuations of brain E2 concentrations in behaving animals. Two independent experiments then identified a rise in E2 concentrations in POM during sexual interactions. This increase occurred within 10 min after the initiation of the sexual interaction and was specific to the POM as there was no increase in E2 concentrations in males that had their cannula outside of this area. Together these data confirm that rapid changes in AA measured ex vivo cannot be considered as a reliable proxy for E2 concentrations. The discrepancies could originate either from the different time resolution related to the two techniques or from differences in the microenvironment in which aromatase functions in vivo and during ex vivo assays. [less ▲]

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See detailAvant-projet de décret relatif au Code wallon du Bien-être des animaux Lecture commentée au 04 juillet 2017 des chap. 4, 8, 11
Drion, Pierre ULiege; Seutin, Vincent ULiege; Balthazart, Jacques ULiege et al

Report (2017)

La compétence « bien-être animal », auparavant fédérale, a été régionalisée en juillet 2014. Ce projet de code vise à remplacer les dispositions légales en vigueur (la Loi de 1984 telle que modifiée par ... [more ▼]

La compétence « bien-être animal », auparavant fédérale, a été régionalisée en juillet 2014. Ce projet de code vise à remplacer les dispositions légales en vigueur (la Loi de 1984 telle que modifiée par les décrets du Gouvernement wallon). Certains éléments sont repris tels quels de la Directive 2010/63. Cela est nécessaire car la Directive européenne en tant que telle n’a pas de force obligatoire en Belgique. Elle doit être transcrite par un instrument législatif (avant, la Loi de 1984, aujourd’hui, le projet de code). Certains aspects semblent flous, mais renvoient à des dispositions que le Gouvernement doit encore prendre (au travers d’arrêtés du Gouvernement wallon, comme le faisaient avant les nombreux arrêtés royaux et du gouvernement qui réglementent la matière). Les arrêtés d’exécution devront obligatoirement tenir compte de la directive européenne et s’inspirer de dispositions actuellement en vigueur. [less ▲]

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See detailChanges in preoptic estradiol concentrations during male sexual behavior
de Bournonville, Marie-Pierre ULiege; de Bournonville, Catherine; Ball, Gregory et al

in Frontiers in Neuroscience (2017, May 30)

Besides its long-term control by steroids, male sexual behavior is also modulated by membrane-initiated effects of neuroestrogens in the short-term (within minutes). These effects are thought to depend on ... [more ▼]

Besides its long-term control by steroids, male sexual behavior is also modulated by membrane-initiated effects of neuroestrogens in the short-term (within minutes). These effects are thought to depend on short-term variations in the local production of estrogens, through rapid fluctuations of the enzymatic activity of brain aromatase, the enzyme that synthesizes estradiol (E2) from testosterone. Studies in male Japanese quail have shown that a sexual interaction with a female leads to a decrease in the activity of brain aromatase within minutes. 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 aromatase activity (AA) in the brain. However recent studies showed that AA does not always reflect local E2 concentration. For example, while an acute stress decreases AA in the POM, E2 concentration increases in the same conditions. Here we used in vivo microdialysis to quantify changes in E2 concentration in the male POM during sexual interactions with a female. A series of experiments conducted to validate the in vivo dialysis and RIA methods showed that (1) E2 concentration in the dialysate change linearly with the concentration of a bath containing known amounts of E2 in which the probe was placed, (2) an increase in preoptic E2 concentration is observed after retrodialysis of testosterone and (3) preoptic E2 levels also increase after a peripheral injection of E2. Together these results suggest that in vivo dialysis is a suitable method to assay E2 in the range of brain concentrations suspected to be present in physiological conditions. With this approach, we showed during two independent experiments that E2 concentrations increase in the POM during sexual interactions with a female. Birds that had their cannula placed outside the POM did not show any increase in E2 levels. The E2 increase in the POM could serve 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. [less ▲]

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See detailPerineuronal nets and song learning-related neuroplasticity in the songbird brain
Cornez, Gilles ULiege; Jonckers, Elisabeth; Schevchouk, Olesya et al

Conference (2017, May 22)

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

Perineuronal nets (PNN) 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 PNN limits synaptogenesis around PV+ neurons and PNN have been validated as a marker characterizing the end of critical periods for visual learning. In songbirds, song learning is limited to critical periods during ontogeny in close-ended learners such as zebra finches and to specific phases of the annual cycle in open-ended learners such as canaries that are able to modify their song seasonally. Sensitive periods for song learning are associated with neuroplasticity including morphological changes due to neurogenesis and synaptic reorganization in the song control nuclei during development and adult seasonal song modifications. The hormonal control of developmental and seasonal neuroplasticity is well documented in songbirds but little is known about the possible regulation of sensitive periods for vocal learning by PNN. First, to explore the expression of PNN throughout the development, we used zebra finches brains collected at different key ages in the song learning process (10, 20, 30, 40, 50, 60, 90, 120 days post-hatch, dph) and we quantified PNN expression and their colocalization around PV+ interneurons. The number of PNN and the % of PNN around PV+ interneurons increased progressively during developmental song learning in 3 of the main song control nuclei (HVC, RA and Area X). Moreover, we confirmed that females that never sing have fewer PNN than males in HVC and RA, two song nuclei involved in song production, at all ages after the peak in PNN numbers seen in males between 50 and 90 dph. Secondly we used adult male and female canaries (in 2 different experiments) treated with a subcutaneous implant filled with testosterone or left empty in control subjects to mimic what happens in the spring when the seasonal modification of the song ends and the song crystallizes. Testosterone significantly increased the number of PNN in the main song control nuclei in both sexes. Together these data suggest that increased expression of PNN in the songbird brain might limit neuroplasticity at the end of developmental and seasonal vocal learning [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 ULiege; Madison, F.N.; Van der Linden, A. et al

in Developmental Neurobiology (2017), 77(8), 975-994

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 detailSteroid metabolism in the brain: From bird watching to molecular biology, a personal journey
Balthazart, Jacques ULiege

in Hormones and Behavior (2017), 93

Since Arnold Adolph Berthold established in 1849 the critical role of the testes in the activation of male sexual behavior, intensive research has identified many sophisticated neurochemical and molecular ... [more ▼]

Since Arnold Adolph Berthold established in 1849 the critical role of the testes in the activation of male sexual behavior, intensive research has identified many sophisticated neurochemical and molecular mechanisms mediating this action. Studies in Japanese quail demonstrated the critical role of testosterone action and of testosterone aromatization in the sexually dimorphic medial preoptic nucleus in the activation of male copulatory behavior. The development of an immunohistochemical visualization of brain aromatase in quail then allowed further refinement in the localization of the sites of neuroestrogens production. Testosterone aromatization is required for the activation of both appetitive and consummatory aspects of male sexual behavior. Brain aromatase activity is modulated by steroid-induced changes in the transcription of the corresponding gene but also more rapidly by phosphorylation processes. Sexual interactions with a female also rapidly regulate brain aromatase activity in an anatomically specific manner presumably via the release and action of endogenous glutamate. These rapid changes in estrogen production modulate sexual behavior and in particular its motivational component with latencies ranging between 15 and 30 min. Brain estrogens seem to act in a manner akin to a neurotransmitter or at least a neuromodulator. More recently, assays of brain estradiol concentrations in micropunched samples or in dialysis samples obtained from behaviorally active males suggested that aromatase activity measured ex vivo might not be an accurate proxy to the rapid changes in local neuroestrogens production and concentrations. Studies of brain testosterone metabolism are thus not over and will keep scientists busy for a little longer. Elsevier SBN Keynote Address, Montreal. © 2017 Elsevier Inc. [less ▲]

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See detailFraternal birth order effect on sexual orientation explained
Balthazart, Jacques ULiege

in Proceedings of the National Academy of Sciences of the United States of America (2017), 115(2), 234-236

[No abstract available]

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