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See detailTestosterone recruits new aromatase-imunoreactive cells in neonatal quail brain.
Bardet, Sylvia M; Cornil, Charlotte ULg; Balthazart, Jacques ULg

in Neuroreport (2010), 21(5), 376-80

It was shown earlier that, in Japanese quail the mechanism controlling the induction by testosterone of aromatase activity develops between embryonic days 10 and 14. The cellular processes underlying this ... [more ▼]

It was shown earlier that, in Japanese quail the mechanism controlling the induction by testosterone of aromatase activity develops between embryonic days 10 and 14. The cellular processes underlying this activation have, however, not been investigated in detail. Here, we demonstrate that the increase in aromatase activity observed in neonates treated with testosterone propionate between postnatal days 1 and 3 results from the recruitment of additional populations of aromatase-immunoreactive cells that were not expressing the enzyme at detectable levels before. This recruitment concerns all brain nuclei normally expressing the enzyme even if it is more prominent in the ventromedial hypothalamus than in other nuclei. [less ▲]

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See detailBehavioral effects of brain-derived estrogens in birds.
Balthazart, Jacques ULg; Taziaux, Mélanie ULg; Holloway, Kevin et al

in Annals of the New York Academy of Sciences (2009), 1163

In birds as in other vertebrates, estrogens produced in the brain by aromatization of testosterone have widespread effects on behavior. Research conducted with male Japanese quail demonstrates that ... [more ▼]

In birds as in other vertebrates, estrogens produced in the brain by aromatization of testosterone have widespread effects on behavior. Research conducted with male Japanese quail demonstrates that effects of brain estrogens on all aspects of sexual behavior, including appetitive and consummatory components as well as learned aspects, can be divided into two main classes based on their time course. First, estrogens via binding to estrogen receptors regulate the transcription of a variety of genes involved primarily in neurotransmission. These neurochemical effects ultimately result in the activation of male copulatory behavior after a latency of a few days. Correlatively, testosterone and its aromatized metabolites increase the transcription of the aromatase mRNA, resulting in an increased concentration and activity of the enzyme that actually precedes behavioral activation. Second, recent studies with quail demonstrate that brain aromatase activity can also be modulated within minutes by phosphorylation processes regulated by changes in intracellular calcium concentration, such as those associated with glutamatergic neurotransmission. The rapid upregulations or downregulations of brain estrogen concentration (presumably resulting from these changes in aromatase activity) affect, by nongenomic mechanisms with relatively short latencies (frequency increases or decreases respectively within 10-15 min), the expression of male sexual behavior in quail and also in rodents. Brain estrogens thus affect behavior on different time scales by genomic and nongenomic mechanisms similar to those of a hormone or a neurotransmitter. [less ▲]

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See detailEstradiol, a key endocrine signal in the sexual differentiation and activation of reproductive behavior in quail.
Balthazart, Jacques ULg; Cornil, Charlotte ULg; Charlier, Thierry ULg et al

in Journal of Experimental Zoology. Part A, Ecological Genetics and Physiology (2009), 311(5), 323-45

In Japanese quail, estrogen's effects on sexual behavior can be divided into three classes based on the underlying mechanisms and time-course of action and release. During embryonic life, the embryonic ... [more ▼]

In Japanese quail, estrogen's effects on sexual behavior can be divided into three classes based on the underlying mechanisms and time-course of action and release. During embryonic life, the embryonic ovary secretes large amounts of estrogens. In contrast to what is observed in mammals where sexual differentiation essentially proceeds via masculinization of the males, in quail, females are demasculinized by their endogenous ovarian estrogens, an effect that can be blocked by injection of an aromatase inhibitor and mimicked in male embryos by an injection of estradiol. In adulthood, testosterone secreted by the testes is converted into estrogens by the preoptic aromatase. Locally produced estrogens activate male sexual behavior largely through the activation of estrogen receptors resulting in the transcription of a variety of genes, including brain aromatase (genomic effect). Both changes in estrogen production and action are observed within latencies ranging from a few hours to a few days, and are completely reversible. Additionally, brain aromatase activity can be modulated within minutes by calcium-dependent phosphorylations, triggered by variations in glutamatergic neurotransmission. These rapid changes in aromatase activity affect with relatively short latencies (10-15 min) the expression of male sexual behavior in quail and also in mice. Overall, the effects of estrogens on sexual behavior can thus be categorized into three classes: organizational (irreversible genomic action during ontogeny), activational (reversible genomic action during adulthood) and rapid nongenomic effects. Rapid and slower changes in brain aromatase activity match well with the two modes of estrogen action on behavior and provide temporal variations in the estrogens' bioavailability that should be able to support the entire range of established effects for this steroid. [less ▲]

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See detailPresence of aromatase and estrogen receptor alpha in the inner ear of zebra finches.
Noirot, Isabelle ULg; Adler, Henry J; Cornil, Charlotte ULg et al

in Hearing Research (2009)

Sex differences in song behavior and in the neural system controlling song in songbirds are well documented but relatively little is known about sex differences in hearing. We recently demonstrated the ... [more ▼]

Sex differences in song behavior and in the neural system controlling song in songbirds are well documented but relatively little is known about sex differences in hearing. We recently demonstrated the existence of sex differences in auditory brainstem responses in a songbird species, the zebra finch (Taeniopygia guttata). Many sex differences are regulated by sex steroid hormone action either during ontogeny or in adulthood. As a first step to test the possible implication of sex steroids in the control of sex differences in the zebra finch auditory system, we evaluated via immunocytochemistry whether estrogens are produced and act in the zebra finch inner ear. Specifically we examined the distribution of aromatase, the enzyme converting testosterone into an estrogen, and of estrogen receptors of the alpha subtype (ERalpha) in adult zebra finch inner ears. The anatomy of the basilar papillae was visualized by fluorescein-phalloidin, which delineated the actin structure of hair cells and supporting cells at their apical surface. Whole mount preparations of basilar papillae stained by immunocytochemistry revealed in both males and females an abundant aromatase distribution in the cytoplasm of hair cells, while ERalpha was identified in the nuclei of hair cells and of underlying supporting cells. Double labeled preparations confirmed the extensive co-localization of aromatase and ERalpha in the vast majority of the hair cells. These results are consistent with studies on non-avian species, suggesting a role for estrogens in auditory function. These findings are also consistent with the notion that estrogens may contribute to a sex difference in hearing. To our knowledge, this is the first demonstration of the presence of aromatase and of the co-localization of aromatase and ERalpha in the sensory epithelium of the inner ear in any animal model. [less ▲]

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See detailRapid regulation of brain oestrogen synthesis: the behavioural roles of oestrogens and their fates.
Cornil, Charlotte ULg

in Journal of Neuroendocrinology (2009), 21(3), 217-26

Besides their well-known genomic actions, oestrogens also exert effects through the activation of receptors associated with the plasma membrane that are too fast to be mediated by transcriptional ... [more ▼]

Besides their well-known genomic actions, oestrogens also exert effects through the activation of receptors associated with the plasma membrane that are too fast to be mediated by transcriptional activation (nongenomic effects). Although the existence of such rapid effects of oestrogens and their involvement in various biological processes are not in doubt, questions remain about the mechanisms responsible for the rapid modulations of oestrogen production that are required to sustain their nongenomic effects. Recent data indicate that the conversion of androgens into oestrogens in the brain by the enzyme aromatase can be rapidly modulated by conformational changes of the enzyme, thus providing a possible mechanism for rapid controls of the effects of oestrogens on male sexual behaviour. In this review, the data supporting this hypothesis are described. Subsequently, a few unanswered questions are discussed, such as the mechanism of oestrogen inactivation or the potential cellular sites of action of brain-derived oestrogens on male sexual behaviour. [less ▲]

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See detailAre rapid changes in gonadal testosterone release involved in the fast modulation of brain estrogen effects?
Cornil, Charlotte ULg; Stevenson, Tyler J; Ball, Gregory F

in General and Comparative Endocrinology (2009)

Estradiol facilitates the expression of male sexual behavior in Japanese quail within a few minutes. These rapid behavioral effects of estradiol could result from rapid changes in its local production in ... [more ▼]

Estradiol facilitates the expression of male sexual behavior in Japanese quail within a few minutes. These rapid behavioral effects of estradiol could result from rapid changes in its local production in the preoptic area by aromatase, the enzyme converting testosterone into estradiol. Alternatively, aromatase activity may remain constant but fluctuations of local estradiol production could arise from rapid changes in the concentration of the enzymatic substrate, namely testosterone. Rapid increases of circulating testosterone levels have been observed in males of various species following social encounters. Surprisingly, in quail, the interaction with a female seems to result in a decrease in circulating testosterone levels. However, in that study conducted in quail, the samples were collected at intervals longer than the recently observed rapid effects of estradiol on sexual behavior. In the present study we investigated whether plasma testosterone concentrations fluctuate on a shorter time-frame. Eleven male were tested 5 min before and 5, 15 or 30 min after being allowed to have visual access to a female or to copulate with a female for 5 min. Both types of interactions resulted in a significant decline in circulating testosterone levels at latencies as short as 5 min. These data demonstrate that the decrease in testosterone levels is initiated shortly after sexual encounters. Because visual interactions with a female did not result in a rapid increase in testosterone concentrations, these findings rule out the possibility that a rapid rise in circulating testosterone levels participates in the rapid increase in brain estrogen synthesis and its facilitatory effects on copulatory behavior. [less ▲]

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See detailD1-like dopamine receptor density in nuclei involved in social behavior correlates with song in a context-dependent fashion in male European starlings.
Heimovics, Sarah A.; Cornil, Charlotte ULg; Ball, Gregory F. et al

in Neuroscience (2009), 159(3), 962-73

Research in songbirds shows that singing behavior is regulated by both brain areas involved in vocal behavior as well as those involved in social behavior. Interestingly, the precise role of these regions ... [more ▼]

Research in songbirds shows that singing behavior is regulated by both brain areas involved in vocal behavior as well as those involved in social behavior. Interestingly, the precise role of these regions in song can vary as a function of the social, environmental and breeding context. To date, little is known about the neurotransmitters underlying such context-dependent regulation of song. Dopamine (DA) modulates highly motivated, goal-directed behaviors (including sexually motivated song) and emerging data implicate DA in the context-dependent regulation of singing behavior. This study was performed to begin to examine whether differences in DA receptors may underlie, in part, context-dependent differences in song production. We used autoradiographic procedures to label D1-like and D2-like DA receptors to examine the relationship between DA receptor density and singing behavior in multiple contexts in male European starlings (Sturnus vulgaris). Within a breeding context (when testosterone (T) was high), D1-like receptor density in the medial preoptic nucleus (POM) and midbrain central gray (GCt) negatively correlated with song used to attract a female. Additionally in this context, D1-like receptor density in POM, GCt, medial bed nucleus of the stria terminalis (BSTm), and lateral septum (LS) negatively correlated with song likely used to defend a nest box. In contrast, in a non-breeding context (when T was low), D1-like receptor density in POM and LS positively correlated with song used to maintain social flocks. No relationships were identified between song in any context and D2-like receptor densities. Differences in the brain regions and directional relationships between D1-like receptor binding and song suggest that dopaminergic systems play a region and context-specific role in song. These data also suggest that individual variation in singing behavior may, in part, be explained by individual differences in D1-like receptor density in brain regions implicated in social behavior. [less ▲]

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See detailSpecies Differences in the Relative Densities of D1- and D2-Like Dopamine Receptor Subtypes in the Japanese Quail and Rats: An in vitro Quantitative Receptor Autoradiography Study.
Kleitz, H. K.; Cornil, Charlotte ULg; Balthazart, Jacques ULg et al

in Brain, Behavior & Evolution (2009), 73(2), 81-90

Evidence has accumulated that the regulation of male sexual behavior by dopamine might not be the same in Japanese quail (and perhaps all birds) as it is in mammals. For example, the non-selective ... [more ▼]

Evidence has accumulated that the regulation of male sexual behavior by dopamine might not be the same in Japanese quail (and perhaps all birds) as it is in mammals. For example, the non-selective dopamine receptor agonist, apomorphine (APO), facilitates male sexual behavior in rats but inhibits it in quail. Although the general organization of the dopamine system is similar in birds and mammals, it is possible that the relative distribution and/or density of binding sites are different. We therefore compared the relative densities of D1-like and D2-like receptor subtypes in Japanese quail and rats, with the use of in vitro quantitative receptor autoradiography. Brain sections from 8 male rats and 8 male quail were labeled with [(3)H]SCH-23390 and [(3)H]Spiperone. In general we found a systematic species difference in the relative density of D1- vs. D2-like receptors such that the D2/D1 ratio is higher in quail than in rats in areas, known to be important target sites for dopamine action such as striatal regions or the preoptic area, which is also associated with activation of sexual behavior. This difference might explain the variation in the behavioral effectiveness of APO in rats as compared to quail; with a higher relative density of D2-like receptors in quail, a similar dose of APO would be more likely to activate inhibitory processes in quail than in rats. [less ▲]

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See detailDopamine binds to alpha(2)-adrenergic receptors in the song control system of zebra finches (Taeniopygia guttata).
Cornil, Charlotte ULg; Castelino, Christina B; Ball, Gregory F

in Journal of Chemical Neuroanatomy (2008), 35(2), 202-15

A commonly held view is that dopamine exerts its effects via binding to D1- and D2-dopaminergic receptors. However, recent data have emerged supporting the existence of a direct interaction of dopamine ... [more ▼]

A commonly held view is that dopamine exerts its effects via binding to D1- and D2-dopaminergic receptors. However, recent data have emerged supporting the existence of a direct interaction of dopamine with adrenergic but this interaction has been poorly investigated. In this study, the pharmacological basis of possible in vivo interactions between dopamine and alpha(2)-adrenergic receptors was investigated in zebra finches. A binding competition study showed that dopamine displaces the binding of the alpha(2)-adrenergic ligand, [(3)H]RX821002, in the brain. The affinity of dopamine for the adrenergic sites does not differ between the sexes and is 10- to 28-fold lower than that for norepinephrine. To assess the anatomical distribution of this interaction, binding competitions were performed on brain slices incubated in 5nM [(3)H]RX821002 in the absence of any competitor or in the presence of norepinephrine [0.1microM] or dopamine [1microM]. Both norepinephrine and dopamine displaced the binding of the radioligand though to a different extent in most of the regions studied (e.g., area X, the lateral part of the magnocellular nucleus of anterior nidopallium, HVC, arcopallium dorsale, ventral tegmental area and substantia grisea centralis) but not in the robust nucleus of the arcopallium. Together these data provide evidence for a direct interaction between dopamine and adrenergic receptors in songbird brains albeit with regional variation. [less ▲]

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See detailInterplay among catecholamine systems: dopamine binds to alpha2-adrenergic receptors in birds and mammals.
Cornil, Charlotte ULg; Ball, Gregory F

in Journal of Comparative Neurology (The) (2008), 511(5), 610-27

Dopaminergic and adrenergic receptors are G-protein-coupled receptors considered to be different based on their pharmacology and signaling pathways. Some receptor subtypes that are members of one family ... [more ▼]

Dopaminergic and adrenergic receptors are G-protein-coupled receptors considered to be different based on their pharmacology and signaling pathways. Some receptor subtypes that are members of one family are actually closer in phylogenetic terms to some subtypes belonging to the other family, suggesting that the pharmacological specificity among these receptors from different families is not perfect. Indeed, evidence is accumulating that one amine can cross-talk with receptors belonging to the other system. However, most of these observations were collected in vitro using artificial cell models transfected with cloned receptors, so that the occurrence of this phenomenon in vivo as well as its distribution in the central nervous system is not known. In this study the pharmacological basis of possible in vivo interactions between dopamine and alpha(2)-adrenergic receptors was investigated in quail, zebra finches, and rats. Binding competitions showed that dopamine displaces the binding of the selective alpha(2)-adrenergic ligand, [(3)H]RX821002, in the brain of the three species with an affinity approximately 10-28-fold lower than that of norepinephrine. Dopamine also displaces with an affinity 3-fold lower than norepinephrine the binding of [(3)H]RX821002 to human alpha(h2A)-adrenergic receptors expressed in Sf9 cells. The anatomical distribution of this interaction was assessed in brain slices of quail and rat based on autoradiographic methods. Both norepinephrine and dopamine significantly displace [(3)H]RX821002 binding in all brain nuclei considered. Together, these data provide evidence for an interaction between the dopaminergic and noradrenergic systems in the vertebrate brain, albeit with species variations. [less ▲]

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See detailDifferential c-fos expression in the brain of male Japanese quail following exposure to stimuli that predict or do not predict the arrival of a female
Taziaux, Mélanie ULg; Lopez, J.; Cornil, Charlotte ULg et al

in European Journal of Neuroscience (2007), 25(9), 2835-2846

We investigated the effects of presenting a sexual conditioned stimulus on the expression of c-fos in male Japanese quail. Eight brain sites were selected for analysis based on previous reports of c-fos ... [more ▼]

We investigated the effects of presenting a sexual conditioned stimulus on the expression of c-fos in male Japanese quail. Eight brain sites were selected for analysis based on previous reports of c-fos expression in these areas correlated with sexual behaviour or learning. Males received either paired or explicitly unpaired presentations of an arbitrary stimulus and visual access to a female. Nine conditioning trials were conducted, one per day, for each subject. On the day following the ninth trial, subjects were exposed to the conditional stimulus (CS) for 5 min. Conditioning was confirmed by analysis of rhythmic cloacal sphincter movements (RCSM), an appetitive sexual behaviour, made in response to the CS presentation. Subjects in the paired condition performed significantly more RCSM than subjects in the unpaired group. Brains were collected 90 min following the stimulus exposure and stained by immunolhistochemistry for the FOS protein. Significant group differences in the number of FOS-immunoreactive (FOS-ir) cells were found in two brain regions, the nucleus taeniae of the amygdala (TnA) and the hippocampus (Hp). Subjects in the paired condition had fewer FOS-ir cells in both areas than subjects in the unpaired condition. These data provide additional support to the hypothesis that TnA is implicated in the expression of appetitive sexual behaviours in male quail and corroborate numerous previous reports of the involvement of the hippocampus in conditioning. Further, these data suggest that conditioned and unconditioned sexual stimuli activate different brain regions but have similar behavioural consequences. [less ▲]

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See detailFunctional significance of the rapid regulation of brain estrogen action: Where do the estrogens come from?
Cornil, Charlotte ULg; Ball, G. F.; Balthazart, Jacques ULg

in Brain Research (2006), 1126

Estrogens exert a wide variety of actions on reproductive and non-reproductive functions. These effects are mediated by slow and long lasting genomic as well as rapid and transient non-genomic mechanisms ... [more ▼]

Estrogens exert a wide variety of actions on reproductive and non-reproductive functions. These effects are mediated by slow and long lasting genomic as well as rapid and transient non-genomic mechanisms. Besides the host of studies demonstrating the role of genomic actions at the physiological and behavioral level, mounting evidence highlights the functional significance of non-genomic effects. However, the source of the rapid changes in estrogen availability that are necessary to sustain their fast actions is rarely questioned. For example, the rise of plasma estrogens at pro-estrus that represents one of the fastest documented changes in plasma estrogen concentration appears too slow to explain these actions. Alternatively, estrogen can be synthesized in the brain by the enzyme aromatase providing a source of locally high concentrations of the steroid. Furthermore, recent studies demonstrate that brain aromatase can be rapidly modulated by afferent inputs, including glutamatergic afferents. A role for rapid changes in estrogen production in the central nervous system is supported by experiments showing that acute aromatase inhibition affects nociception as well as male sexual behavior and that preoptic aromatase activity is rapidly (within min) modulated following mating. Such mechanisms thus fulfill the gap existing between the fast actions of estrogen and their mode of production and open new avenues for the understanding of estrogenic effects on the brain. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailNeuroanatomical specificity in the expression of the immediate early gene c-fos following expression of appetitive and consummatory male sexual behaviour in Japanese quail
Taziaux, Mélanie ULg; Cornil, Charlotte ULg; Dejace, C. et al

in European Journal of Neuroscience (2006), 23(7), 1869-1887

We investigated the neural sites related to the occurrence of appetitive (ASB) and consummatory (CSB) aspects of male sexual behaviour in Japanese quail. Castrated males treated with testosterone were ... [more ▼]

We investigated the neural sites related to the occurrence of appetitive (ASB) and consummatory (CSB) aspects of male sexual behaviour in Japanese quail. Castrated males treated with testosterone were exposed for 5 min to one of four experimental conditions: (i) free interaction with a female (CSB group); (ii) expression of rhythmic cloacal sphincter movements in response to the visual presentation of a female (ASB-F group); (iii) or a male (ASB-M group), and (iv) handling as a control manipulation. Brains were collected 90 min after the start of behavioural tests and stained by immunocytochemistry for the FOS protein. An increase in FOS expression was observed throughout the rostro-caudal extent of the medial preoptic nucleus (POM) in CSB males, whereas the view of a female (ASB-F) induced an increased FOS expression in the rostral POM only. In the CSB group, there was also an increase in FOS expression in the bed nucleus striae terminalis, and both the CSB and ASB-F groups exhibited increased FOS expression in aspects of the ventro-lateral thalamus (VLT) related to visual processing. Moreover, both the CSB and ASB-M groups showed increased FOS expression in the lateral septum. These data provide additional support to the idea that there is a partial anatomical dissociation between structures involved in the control of both aspects of male sexual behaviour and independently provide data consistent with a previous lesion study that indicated that the rostral and caudal POM differentially control the expression of ASB and CSB in quail. [less ▲]

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See detailEstradiol rapidly activates male sexual behavior and affects brain monoamine levels in the quail brain
Cornil, Charlotte ULg; Dalla, C.; Papadopoulou-Daifoti, Z. et al

in Behavioural Brain Research (2006), 166(1), 110-123

Steroids are generally viewed as transcription factors binding to intracellular receptors and activating gene transcription. Rapid cellular effects mediated via non-genomic mechanisms have however been ... [more ▼]

Steroids are generally viewed as transcription factors binding to intracellular receptors and activating gene transcription. Rapid cellular effects mediated via non-genomic mechanisms have however been identified and one report showed that injections of estradiol rapidly stimulate chemoinvestigation and mounting behavior in castrated male rats. It is not known whether such effects take place in other species and what are the cellular underlying mechanisms. We show here that a single injection of estradiol (500 wg/kg) rapidly and transiently activates copulatory behavior in castrated male quail pre-treated with a dose of testosterone behaviorally ineffective by itself. The maximal behavioral effect was observed after 15 min. In a second experiment, the brain of all subjects was immediately collected after behavioral tests performed 15 min after injection. The preoptic area-hypothalamus (HPOA), hindbrain, telencephalon and cerebellum were isolated and monoamines measured by HPLC-ED. Estradiol increased levels of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) and 5-HIAA/serotonin ratios in the telencephalon and hindbrain independently of whether animals had mated or not. Estradiol also affected these measures in HPOA and cerebellum but this effect was correlated with the level of sexual activity so that significant effects of the treatment only appeared when sexual activity was used as a covariate. Interactions between estradiol effects and sexual activity were also observed for dopamine in the HPOA and for serotonin in the hindbrain and cerebellum. Together, these data demonstrate that a single estradiol injection rapidly activates male sexual behavior in quail and that this behavioral effect is correlated with changes in monoaminergic activity. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailRapid effects of aromatase inhibition on male reproductive behaviors in Japanese quail
Cornil, Charlotte ULg; Taziaux, Mélanie ULg; Baillien, M. et al

in Hormones & Behavior (2006), 49(1), 45-67

Non-genomic effects of steroid hormones on cell physiology have been reported in the brain. However, relatively little is known about the behavioral significance of these actions. Male sexual behavior is ... [more ▼]

Non-genomic effects of steroid hormones on cell physiology have been reported in the brain. However, relatively little is known about the behavioral significance of these actions. Male sexual behavior is activated by testosterone partly through its conversion to estradiol via the enzyme aromatase in the preoptic area (POA). Brain aromatase activity (AA) changes rapidly which might in turn be important for the rapid regulation of behavior. Here, acute effects of Vorozole (TM), an aromatase inhibitor, injected IP at different doses and times before testing (between 15 and 60 min), were assessed on male sexual behavior in quail. To limit the risk of committing both types of statistical errors (I and II), data of all experiments were entered into a meta-analysis. Vorozole (TM) significantly inhibited mount attempts (P < 0.05, size effect [g] = 0.527) and increased the latency to first copulation (P < 0.05, g = 0.251). The treatment had no effect on the other measures of copulatory behavior. Vorozole (TM) also inhibited appetitive sexual behavior measured by the social proximity response (P < 0.05, g = 0.534) or rhythmic cloacal sphincter movements (P < 0.001, g = 0.408). Behavioral inhibitions always reached a maximum at 30 min. Another aromatase inhibitor, androstatrienedione, induced a similar rapid inhibition of sphincter movements. Radioenzyme assays demonstrated that within 30 min Vorozole (TM) had reached the POA and completely blocked AA measured in homogenates. When added to the extracellular milieu, Vorozole (TM) also blocked within 5 min the AA in POA explants maintained in vitro. Together, these data demonstrate that aromatase inhibition rapidly decreases both consummatory and appetitive aspects of male sexual behavior. (c) 2005 Elsevier Inc. All rights reserved. [less ▲]

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See detailRapid changes in production and behavioral action of estrogens.
Balthazart, Jacques ULg; Cornil, Charlotte ULg; Taziaux, Mélanie ULg et al

in Neuroscience (2006), 138(3), 783-91

It is well established that sex steroid hormones bind to nuclear receptors, which then act as transcription factors to control brain sexual differentiation and the activation of sexual behaviors ... [more ▼]

It is well established that sex steroid hormones bind to nuclear receptors, which then act as transcription factors to control brain sexual differentiation and the activation of sexual behaviors. Estrogens locally produced in the brain exert their behavioral effects in this way but mounting evidence indicates that estrogens also can influence brain functioning more rapidly via non-genomic mechanisms. We recently reported that, in Japanese quail, the activity of preoptic estrogen synthase (aromatase) can be modulated quite rapidly (within minutes) by non-genomic mechanisms, including calcium-dependent phosphorylations. Behavioral studies further demonstrated that rapid changes in estrogen bioavailability, resulting either from a single injection of a high dose of estradiol or from the acute inhibition of aromatase activity, significantly affect the expression of both appetitive and consummatory aspects of male sexual behavior with latencies ranging between 15 and 30 min. Together these data indicate that the bioavailability of estrogens in the brain can change on different time-scales (long- and short-term) that match well with the genomic and non-genomic actions of this steroid and underlie two complementary mechanisms through which estrogens modulate behavior. Estrogens produced locally in the brain should therefore be considered not only as neuroactive steroids but they also display many (if not all) functional characteristics of neuromodulators and perhaps neurotransmitters. [less ▲]

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See detailRapid decreases in preoptic aromatase activity and brain monoamine concentrations after engaging in male sexual behavior
Cornil, Charlotte ULg; Dalla, C.; Papadopoulou-Daifoti, Z. et al

in Endocrinology (2005), 146(9), 3809-3820

In Japanese quail, as in rats, the expression of male sexual behavior over relatively long time periods (days to weeks) is dependent on the local production of estradiol in the preoptic area via the ... [more ▼]

In Japanese quail, as in rats, the expression of male sexual behavior over relatively long time periods (days to weeks) is dependent on the local production of estradiol in the preoptic area via the aromatization of testosterone. On a short-term basis (minutes to hours), central actions of dopamine as well as locally produced estrogens modulate behavioral expression. In rats, a view of and sexual interaction with a female increase dopamine release in the preoptic area. In quail, in vitro brain aromatase activity (AA) is rapidly modulated by calcium-dependent phosphorylations that are likely to occur in vivo as a result of changes in neurotransmitter activity. Furthermore, an acute estradiol injection rapidly stimulates copulation in quail, whereas a single injection of the aromatase inhibitor vorozole rapidly inhibits this behavior. We hypothesized that brain aromatase and dopaminergic activities are regulated in quail in association with the expression of male sexual behavior. Visual access as well as sexual interactions with a female produced a significant decrease in brain AA, which was maximal after 5 min. This expression of sexual behavior also resulted in a significant decrease in dopaminergic as well as serotonergic activity after 1 min, which returned to basal levels after 5 min. These results demonstrate for the first time that AA is rapidly modulated in vivo in parallel with changes in dopamine activity. Sexual interactions with the female decreased aromatase and dopamine activities. These data challenge established views about the causal relationships among dopamine, estrogen action, and male sexual behavior. [less ▲]

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See detailDopamine modulates male sexual behavior in Japanese quail in part via actions on noradrenergic receptors
Cornil, Charlotte ULg; Dejace, C.; Ball, G. F. et al

in Behavioural Brain Research (2005), 163(1), 42-57

In rats, dopamine (DA) facilitates male sexual behavior through its combined action on D1- and D2-like receptors, in the medial preoptic area (MPOA) as well as other brain areas. In Japanese quail ... [more ▼]

In rats, dopamine (DA) facilitates male sexual behavior through its combined action on D1- and D2-like receptors, in the medial preoptic area (MPOA) as well as other brain areas. In Japanese quail, systemic injections of dopaminergic drugs suggested a similar pharmacology but central injections have never been performed. Recent electrophysiological experiments demonstrated that DA effects in the MPOA of quail are mediated mainly through the activation of alpha(2)-noradrenergic receptors. Previous studies of DA action on behavior used specific dopaminergic agonists/antagonists and therefore unintentionally avoided the potential cross-reaction with a-receptors. The present study was thus designed to investigate directly the effects of DA on male sexual behavior and to test whether the interaction of DA with heterologous receptors affects this behavior. Intracerebroventricular (i.c.v.) injection of DA or NE inhibited copulation in a dose-dependent manner. Systemic injections of yohimbine, an alpha(2)-noradrenergic antagonist, modulated copulation in a bimodal manner depending on the dose injected. Interestingly, a behaviorally ineffective dose of yohimbine markedly reduced the inhibitory effects of DA when injected 15 min before. Together, these results show for the first time that i.c.v. injections of DA itself inhibit male sexual behavior in quail and suggest that the interaction of DA with alpha(2)-receptors has behavioral significance. (C) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailDifferences in neural activation following expression of appetitive and consummatory male sexual behavior in the quail brain
Taziaux, Mélanie ULg; Cornil, Charlotte ULg; Dejace, C. et al

in Hormones & Behavior (2005, June), 48(1), 130

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