References of "Balthazart, Jacques"
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See detailAnatomically discrete sex differences and enhancement by testosterone of cell proliferation in the telencephalic ventricle zone of the adult canary brain.
Barker, Jennifer M.; Ball, Gregory F.; Balthazart, Jacques ULg

in Journal of chemical neuroanatomy (2013)

Previous work in songbirds has suggested that testosterone increases neuronal recruitment and survival in HVC but does not affect neuronal proliferation in the ventricular zone and that males and females ... [more ▼]

Previous work in songbirds has suggested that testosterone increases neuronal recruitment and survival in HVC but does not affect neuronal proliferation in the ventricular zone and that males and females have similar rates of proliferation except at discrete locations. Many of these conclusions are however based on limited data or were inferred indirectly. Here we specifically tested the effects of testosterone on cellular proliferation in the ventricular zone of both male and female adult canaries. We implanted adult birds of both sexes with testosterone or empty implants for 1 week and injected them with BrdU. One day later, we collected their brains and quantified BrdU-positive cells in the ventricular zone (VZ) at different rostro-caudal levels of the brain, ranging from the level where the song nucleus Area X occurs through the caudal extent of HVC. Proliferation in the dorsal part of the VZ was low and unaffected by sex or testosterone treatment. In the ventral part of the VZ, females had more proliferating cells than males, but only at rostral levels, near Area X. Also in the ventral part of the VZ, testosterone increased proliferation in birds of both sexes, but only in the mid- to caudal-VZ, caudal to the level of Area X, around the septum and HVC. We thus demonstrate here that there is both an effect of testosterone and possibly a more subtle effect of sex on cellular proliferation in the adult songbird brain, and that these effects are specific to different levels of the brain. [less ▲]

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See detailDifferential effects of global versus local testosterone on singing behavior and its underlying neural substrate.
Alward, Beau A.; Balthazart, Jacques ULg; Ball, Gregory F.

in Proceedings of the National Academy of Sciences of the United States of America (2013), 110(48), 19573-8

Steroid hormones regulate multiple but distinct aspects of social behaviors. Testosterone (T) has multiple effects on learned courtship song in that it regulates both the motivation to sing in a ... [more ▼]

Steroid hormones regulate multiple but distinct aspects of social behaviors. Testosterone (T) has multiple effects on learned courtship song in that it regulates both the motivation to sing in a particular social context as well as the quality of song produced. The neural substrate(s) where T acts to regulate the motivation to sing as opposed to other aspects of song has not been definitively characterized. We show here that T implants in the medial preoptic nucleus (POM) of castrated male canaries (Serinus canaria) increase song rate but do not enhance acoustic features such as song stereotypy compared with birds receiving peripheral T that can act globally throughout the brain. Strikingly, T action in the POM increased song control nuclei volume, consistent with the hypothesis that singing activity induces neuroplasticity in the song control system independent of T acting in these nuclei. When presented with a female canary, POM-T birds copulated at a rate comparable to birds receiving systemic T but produced fewer calls and songs in her presence. Thus, POM is a key site where T acts to activate copulation and increase song rate, an appetitive sexual behavior in songbirds, but T action in other areas of the brain or periphery (e.g., HVC, dopaminergic cell groups, or the syrinx) is required to enhance the quality of song (i.e., stereotypy) as well as regulate context-specific vocalizations. These results have broad implications for research concerning how steroids act at multiple brain loci to regulate distinct sociosexual behaviors and the associated neuroplasticity. [less ▲]

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See detailDistinct Neuroendocrine mechanisms control neural activity underlying sex differences in sexual motivation and performance
Balthazart, Jacques ULg; Corbisier de Méaultsart, Céline; Ball, Gregory et al

in European Journal of Neuroscience (2013), 37(5), 735-42

Sexual behavior can be usefully parsed into an appetitive and a consummatory component. Both appetitive and consummatory male-typical sexual behaviors (respectively, ASB and CSB) are activated in male ... [more ▼]

Sexual behavior can be usefully parsed into an appetitive and a consummatory component. Both appetitive and consummatory male-typical sexual behaviors (respectively, ASB and CSB) are activated in male Japanese quail by testosterone (T) acting in the medial preoptic nucleus (POM), but never observed in females. This sex difference is based on a demasculinization (= organizational effect) by estradiol during embryonic life for CSB, but a differential activation by T in adulthood for ASB. Males expressing rhythmic cloacal sphincter movements (RCSMs; a form of ASB) or allowed to copulate display increased Fos expression in POM. We investigated Fos brain responses in females exposed to behavioral tests after various endocrine treat- ments. T-treated females displayed RCSM, but never copulated when exposed to another female. Accordingly they showed an increased Fos expression in POM after ASB but not CSB tests. Females treated with the aromatase inhibitor Vorozole in ovo and T in adulthood displayed both male-typical ASB and CSB, and Fos expression in POM was increased after both types of tests. Thus, the neural circuit mediating ASB is present or can develop in both sexes, but is inactive in females unless they are exposed to exogenous T. In contrast, the neural mechanism mediating CSB is not normally present in females, but can be pre- served by blocking the embryonic production of estrogens. Overall these data confirm the difference in endocrine controls and probably neural mechanisms supporting ASB and CSB in quail, and highlight the complexity of mechanisms underlying sexual differentiation of behavior. [less ▲]

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See detailRAPID MODULATION OF AROMATASE ACTIVITY IN THE VERTEBRATE BRAIN
Charlier, Thierry; Cornil, Charlotte ULg; Balthazart, Jacques ULg

in Journal of Experimental Neuroscience (2013)

Numerous steroid hormones, including 17-estradiol (E2), activate rapid and transient cellular, physiological, and behavioral changes in addition to their well-described genomic effects. Aromatase is the ... [more ▼]

Numerous steroid hormones, including 17-estradiol (E2), activate rapid and transient cellular, physiological, and behavioral changes in addition to their well-described genomic effects. Aromatase is the key-limiting enzyme in the production of estrogens, and the rapid modulation of this enzymatic activity could produce rapid changes in local E2 concentrations. The mechanisms that might mediate such rapid enzymatic changes are not fully understood but are currently under intense scrutiny. Recent studies in our laboratory indicate that brain aromatase activity is rapidly inhibited by an increase in intracellular calcium concentration resulting from potassium- induced depolarization or from the activation of glutamatergic receptors. Phosphorylating conditions also reduce aromatase activity within minutes, and this inhibition is blocked by the addition of multiple protein kinase inhibitors. This rapid modulation of aromatase activity by phosphorylating conditions is a general mechanism observed in different cell types and tissues derived from a variety of spe- cies, including human aromatase expressed in various cell lines. Phosphorylation processes affect aromatase itself and do not involve changes in aromatase protein concentration. The control of aromatase activity by multiple kinases suggests that several amino acids must be concomitantly phosphorylated to modify enzymatic activity but site-directed mutagenesis of several amino acids alone or in combination has not to date revealed the identity of the targeted residue(s). Altogether, the phosphorylation processes affecting aro- matase activity provide a new general mechanism by which the concentration of estrogens can be rapidly altered in the brain. [less ▲]

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See detailNeurochemical control of rapid stress-induced changes in brain aromatase activity
Dickens, Molly; Cornil, Charlotte ULg; Balthazart, Jacques ULg

in Journal of Neuroendocrinology (2013), 25(4), 329-39

In the male brain, the medial preoptic nucleus (POM) is known to be a critical relay for the activation of sexual behaviour, with the aromatisation of testosterone into 17b-oestradiol (E2) playing a key ... [more ▼]

In the male brain, the medial preoptic nucleus (POM) is known to be a critical relay for the activation of sexual behaviour, with the aromatisation of testosterone into 17b-oestradiol (E2) playing a key role. Acute stress has been shown to differentially modulate the aromatase enzyme in this and other brain nuclei in a sex-specific manner. In POM specifically, stress induces increases in aromatase activity (AA) that are both rapid and reversible. How the physiological processes initiated during an acute stress response mediate sex- and nuclei- specific changes in AA and which stress response hormones are involved remains to be determined. By examining the relative effects of corticosterone (CORT), arginine vasotocin (AVT, the avian homologue to arginine vasopressin) and corticotrophin-releasing factor (CRF), the present study aimed to define the hormone profile regulating stress-induced increases in AA in the POM. We found that CORT, AVT and CRF all appear to play some role in these changes in the male brain. In addition, these effects occur in a targeted manner, such that modulation of the enzyme by these hormones only occurs in the POM rather than in all aromatase-expressing nuclei. Similarly, in the female brain, the experimental effects were restricted to the POM but only CRF was capable of inducing the stress-like increases in AA. These data further demonstrate the high degree of specificity (nuclei-, sex- and hormone-specific effects) in this system, highlighting the complexity of the stress–aromatase link and suggesting modes through which the nongenomic modulation of this enzyme can result in targeted, rapid changes in local oestrogen concentrations. [less ▲]

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See detailDynamic changes in brain aromatase activity following sexual interactions in males: Where, when and why?
de Bournonville, Catherine ULg; Dickens, Molly J.; Ball, Gregory F. et al

in Psychoneuroendocrinology (2013), 38(6), 789-99

It is increasingly recognized that estrogens produce rapid and transient effects at many neural sites ultimately impacting physiological and behavioral endpoints. The ability of estrogens to acutely ... [more ▼]

It is increasingly recognized that estrogens produce rapid and transient effects at many neural sites ultimately impacting physiological and behavioral endpoints. The ability of estrogens to acutely regulate cellular processes implies that their concentration should also be rapidly fine-tuned. Accordingly, rapid changes in the catalytic activity of aromatase, the limiting enzyme for estrogen synthesis, have been identified that could serve as a regulatory mechanism of local estrogen concentrations. However, the precise anatomical localization, time-course, triggering stimuli and functional significance of these enzymatic changes in vivo are not well understood. To address these issues as to where, when and why aromatase activity (AA) rapidly changes after sexual interactions, AA was assayed in six populations of aromatase-expressing cells microdissected from the brain of male quail that experienced varying durations of visual exposure to or copulation with a female. Sexual interactions resulted in a rapid AA inhibition. This inhibition occurred in specific brain regions (including the medial preoptic nucleus), in a context-dependent fashion and time-scale suggestive of post-translational modifications of the enzyme. Interestingly, the enzymatic fluctuations occurring in the preoptic area followed rather than preceded copulation and were tied specifically to the female's presence. This pattern of enzymatic changes suggests that rapid estrogen effects are important during the motivational phase of the behavior to trigger physiological events essential to activate mate search and copulation. [less ▲]

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See detailDynamic and region specific changes in estrogen production induced by reproductive stimuli.
de Bournonville, Catherine ULg; Dickens, Molly J; Ball, Gregory F et al

Poster (2012, May 04)

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See detailRegion- and context-specific rapid changes in brain aromatase activity following social interactions
de Bournonville, Catherine ULg; Dickens, Molly J; Ball, Gregory F et al

Poster (2012)

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See detailCellular mechanisms controlling rapid changes in brain aromatase activity
Charlier, Thierry; Cornil, Charlotte ULg; Ball, Gregory et al

in Balthazart, Jacques; Ball, Gregory (Eds.) Brain aromatase, estrogens and behavior (2012)

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See detailRapid modulation of aromatase activity by social and environmental stimuli in quail
Cornil, Charlotte ULg; Dickens, Molly; BAll, Gregory et al

in Balthazart, Jacques; Ball, Gregory (Eds.) Brain aromatase, estrogens and behavior (2012)

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See detailBirth of neural progenitors during the embryonic period of sexual differentiation in the Japanese quail brain.
Bardet, Sylvia M.; Mouriec, Karen; Balthazart, Jacques ULg

in The Journal of comparative neurology (2012), 520(18), 4226-53

Several brain areas in the diencephalon are involved in the activation and expression of sexual behavior, including in quail the medial preoptic nucleus (POM). However, the ontogeny of these diencephalic ... [more ▼]

Several brain areas in the diencephalon are involved in the activation and expression of sexual behavior, including in quail the medial preoptic nucleus (POM). However, the ontogeny of these diencephalic brain nuclei has not to this date been examined in detail. We investigated the ontogeny of POM and other steroid-sensitive brain regions by injecting quail eggs with 5-bromo-2-deoxyuridine (BrdU) at various stages between embryonic day (E)3 and E16 and killing animals at postnatal (PN) days 3 or 56. In the POM, large numbers of BrdU-positive cells were observed in subjects injected from E3-E10, the numbers of these cells was intermediate in birds injected on E12, and most cells were postmitotic in both sexes on E14-E16. Injections on E3-E4 labeled large numbers of Hu-positive cells in POM. In contrast, injections performed at a later stage labeled cells that do not express aromatase nor neuronal markers such as Hu or NeuN in the POM and other steroid-sensitive nuclei and thus do not have a neuronal phenotype in these locations, contrary to what is observed in the telencephalon and cerebellum. No evidence could also be collected to demonstrate that these cells have a glial nature. Converging data, including the facts that these cells divide in the brain mantle and express proliferating cell nuclear antigen (PCNA), a cell cycling marker, indicate that cells labeled by BrdU during the second half of embryonic life are slow-cycling progenitors born and residing in the brain mantle. Future research should now identify their functional significance. [less ▲]

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See detailRapid control of male typical behaviors by brain-derived estrogens
Cornil, Charlotte ULg; Ball, Gregory F; Balthazart, Jacques ULg

in Frontiers in Neuroendocrinology (2012)

Beside their genomic mode of action, estrogens also activate a variety of cellular signaling pathways through non-genomic mechanisms. Until recently, little was known regarding the functional significance ... [more ▼]

Beside their genomic mode of action, estrogens also activate a variety of cellular signaling pathways through non-genomic mechanisms. Until recently, little was known regarding the functional significance of such actions in males and the mechanism that control local estrogen concentration with a spatial and time resolution compatible with these non-genomic actions had rarely been examined. Here, we review evidence that estrogens rapidly modulate a variety of behaviors in male vertebrates. Then, we present in vitro work supporting the existence of a control mechanism of local brain estrogen synthesis by aromatase along with in vivo evidence that rapid changes in aromatase activity also occur in a region-specific manner in response to changes in the social or environmental context. Finally, we suggest that the brain estrogen provision may also play a significant role in females. Together these data bolster the hypothesis that brain-derived estrogens should be considered as neuromodulators. [less ▲]

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See detailBrain aromatase and circulating corticosterone are rapidly regulated by combined acute stress and sexual interaction in a sex specific manner.
Dickens, Molly J.; Balthazart, Jacques ULg; Cornil, Charlotte ULg

in Journal of Neuroendocrinology (2012), 24(10), 1322-34

Neural production of 17β-oestradiol via aromatisation of testosterone may play a critical role in rapid, non-genomic regulation of physiological and behavioural processes. In brain nuclei implicated in ... [more ▼]

Neural production of 17β-oestradiol via aromatisation of testosterone may play a critical role in rapid, non-genomic regulation of physiological and behavioural processes. In brain nuclei implicated in the control of sexual behaviour, sexual or stressfull stimuli induce respectively a rapid inhibition or increase in preoptic aromatase activity (AA). Here, we tested quail that were either non-stressed or acutely stressed (15 min restraint) immediately prior to sexual interaction (5 min) with stressed or non-stressed partners. We measured nuclei-specific AA changes, corresponding behavioural output, fertilisation rates and corticosterone (CORT) concentrations. In males, sexual interaction rapidly reversed stress-induced increases of AA in the medial preoptic nucleus (POM). This time scale (<5min) highlights the dynamic potential of the aromatase system to integrate input from stimuli that drive AA in opposing directions. Moreover, acute stress had minimal effects on male behaviour suggesting that the input from the sexual stimuli on POM AA may actively preserve sexual behaviour despite stress exposure. We also found distinct sex differences in contextual physiological responses: while males did not show any effect of partner status, females responded to both their stress exposure and the male partner's stress exposure at the level of circulating CORT and AA. In addition, fertilisation rates and female CORT correlated with the male partner's exhibition of sexually aggressive behaviour suggesting that female perception of the male can affect their physiology as much as direct stress. Overall, male reproduction appears relatively simple - sexual stimuli, irrespective of stress, drives major neural changes including rapid reversal of stress-induced changes of AA. In contrast, female reproduction appears more nuanced and context specific, with subjects responding physiologically and behaviourally to stress, the male partner's stress exposure, and female-directed male behaviour. [less ▲]

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See detailMilestones on Steroids and the Nervous System: 10 Years of Basic and Translational Research.
Panzica, G. C.; Balthazart, Jacques ULg; Frye, C. A. et al

in Journal of Neuroendocrinology (2012), 24(1), 1-15

During the last 10 years, the conference on 'Steroids and Nervous System' held in Torino (Italy) has been an important international point of discussion for scientists involved in this exciting and ... [more ▼]

During the last 10 years, the conference on 'Steroids and Nervous System' held in Torino (Italy) has been an important international point of discussion for scientists involved in this exciting and expanding research field. The present review aims to recapitulate the main topics that have been presented through the various meetings. Two broad areas have been explored: the impact of gonadal hormones on brain circuits and behaviour, as well as the mechanism of action of neuroactive steroids. Relationships among steroids, brain and behaviour, the sexual differentiation of the brain and the impact of gonadal hormones, the interactions of exogenous steroidal molecules (endocrine disrupters) with neural circuits and behaviour, and how gonadal steroids modulate the behaviour of gonadotrophin-releasing hormone neurones, have been the topics of several lectures and symposia during this series of meetings. At the same time, many contributions have been dedicated to the biosynthetic pathways, the physiopathological relevance of neurosteroids, the demonstration of the cellular localisation of different enzymes involved in neurosteroidogenesis, the mechanisms by which steroids may exert some of their effects, both the classical and nonclassical actions of different steroids, the role of neuroactive steroids on neurodegeneration, neuroprotection, and the response of the neural tissue to injury. In these 10 years, this field has significantly advanced and neuroactive steroids have emerged as new potential therapeutic tools to counteract neurodegenerative events. [less ▲]

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See detailSex differences in brain aromatase activity: genomic and non-genomic controls
Balthazart, Jacques ULg; Charlier, Thierry ULg; Cornil, Charlotte ULg et al

in Frontiers in Endocrinology (2011), 2

Aromatization of testosterone into estradiol in the preoptic area plays a critical role in the activation of male copulation in quail and in many other vertebrate species. Aromatase expression in quail ... [more ▼]

Aromatization of testosterone into estradiol in the preoptic area plays a critical role in the activation of male copulation in quail and in many other vertebrate species. Aromatase expression in quail and in other birds is higher than in rodents and other mammals, which has facilitated the study of the controls and functions of this enzyme. Over relatively long time periods (days to months), brain aromatase activity (AA), and transcription are markedly (four- to sixfold) increased by genomic actions of sex steroids. Initial work indicated that the preoptic AA is higher in males than in females and it was hypothesized that this differential production of estrogen could be a critical factor responsible for the lack of behavioral activation in females. Subsequent studies revealed, however, that this enzymatic sex difference might contribute but is not sufficient to explain the sex difference in behavior. Studies of AA, immunoreactivity, and mRNA concentrations revealed that sex differences observed when measuring enzymatic activity are not necessarily observed when one measures mRNA concentrations. Discrepancies potentially reflect post-translational controls of the enzymatic activity. AA in quail brain homogenates is rapidly inhibited by phosphorylation processes. Similar rapid inhibitions occur in hypothalamic explants maintained in vitro and exposed to agents affecting intracellular calcium concentrations or to glutamate agonists. Rapid changes in AA have also been observed in vivo following sexual interactions or exposure to short-term restraint stress and these rapid changes in estrogen production modulate expression of male sexual behaviors. These data suggest that brain estrogens display most if not all characteristics of neuromodulators if not neurotransmitters. Many questions remain however concerning the mechanisms controlling these rapid changes in estrogen production and their behavioral significance. [less ▲]

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See detailRapid activation of phosphorylated mitogen-activated protein kinase after sexual stimulation in male mice.
Taziaux, Mélanie ULg; Keller, Matthieu; Balthazart, Jacques ULg et al

in Neuroreport (2011), 22(6), 294-8

We mapped cells immunoreactive for the phosphorylated form (p44/p42) of the mitogen-activated protein kinase (pMAPK--also known as ERK1/2) in the brain of male mice after exposure to female olfactory cues ... [more ▼]

We mapped cells immunoreactive for the phosphorylated form (p44/p42) of the mitogen-activated protein kinase (pMAPK--also known as ERK1/2) in the brain of male mice after exposure to female olfactory cues or after the display of male copulatory behaviors. Exposure to soiled bedding from estrous females or the display of coital behaviors rapidly (within 10 min) induced MAPK phosphorylation in most of the brain regions known to be involved in the processing of olfactory cues (main and accessory olfactory bulbs, amygdala, and medial preoptic area) and in the control of copulatory behavior (amygdala and medial preoptic area). MAPK phosphorylation thus seems to be a useful marker to study short-term neural activation associated with the expression of specific behaviors. [less ▲]

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See detailOrganizing effects of sex steroids on brain aromatase activity in quail
Cornil, Charlotte ULg; Ball, Gregory F; Balthazart, Jacques ULg et al

in PLoS ONE (2011), 6(4), 19196

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See detailHuman and Quail Aromatase Activity Is Rapidly and Reversibly Inhibited by Phosphorylating Conditions
Charlier, Thierry ULg; Harada, Nobuhiro; Balthazart, Jacques ULg et al

in Endocrinology (2011), 152(11), 4199-210

Besides their slow genomic actions, estrogens also induce rapid physiological responses. To be functionally relevant, these effects must be associated with rapid changes in local concentrations of ... [more ▼]

Besides their slow genomic actions, estrogens also induce rapid physiological responses. To be functionally relevant, these effects must be associated with rapid changes in local concentrations of estrogens. Rapid changes in aromatase activity (AA) controlled by calcium-dependent phosphorylations of the enzyme can alter in a rapid manner local estrogen concentrations, but so far this mechanism was identified only in the avian (quail) brain. We show here that AA is also rapidly down-regulated by phosphorylating conditions in quail ovary homogenates and in various cell lines transfected with human aromatase (HEK 293, Neuro2A, and C6). Enzymatic activity was also rapidly inhibited after depolarization of aromatase-expressing HEK 293 cells with 100 mm KCl, and activity was fully restored when cells returned to control conditions. Western blot analysis demonstrated that the reduction of enzymatic activity is not due to protein degradation. We next investigated by site-directed mutagenesis the potential implication in the control of AA of specific aromatase residues identified by bioinformatic analysis. Mutation of the amino acids S118, S247, S267, T462, T493, or S497 to alanine, alone or in combination, did not block the rapid inhibition of enzymatic activity induced by phosphorylating conditions, but basal AA was markedly decreased in the S118A mutant. Altogether, these results demonstrate that the rapid inhibition of AA is a widespread and fully reversible process and that phosphorylation of specific residues modulate AA. 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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