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See detailAnatomical relationships between aromatase-immunoreactive neurons and nitric oxide synthase as evidenced by NOS immunohistochemistry or NADPH diaphorase histochemistry in the quail forebrain
Balthazart, Jacques ULg; Panzica, G. C.; Krohmer, R. W.

in Journal of Chemical Neuroanatomy (2003), 25(1), 39-51

In Japanese quail (Coturnix japonica), previous studies indicated that the distribution of reduced nicotinamide dinucleotide phosphate (NADPH) diaphorase overlaps with steroid-sensitive areas that contain ... [more ▼]

In Japanese quail (Coturnix japonica), previous studies indicated that the distribution of reduced nicotinamide dinucleotide phosphate (NADPH) diaphorase overlaps with steroid-sensitive areas that contain dense populations of aromatase-immunoreactive (ARO-ir) cells. We investigated here the anatomical relationships between aromatase (ARO) and nitric oxide synthase (NOS)containing cells that were visualized both by NOS-immunohistochemistry and NADPH-histochemistry. The distribution of ARO-ir and of NADPH-positive cells in the forebrain observed here matched exactly the distribution previously reported. The distribution of NOS-immunoreactive material in the vicinity of ARO-ir cell groups appeared similar to the distribution of NADPH-positive structures previously identified by histochemistry. The number of NOS-immunoreactive cells was similar to the number of NADPH-positive cells and them were found in the same brain regions. In contrast. few NOS-immunoreactive fibers were observed whereas numerous NADPH-positive fibers and Punctuate structures were present in many areas. Major groups of NOS-immunoreactive/ NADPH-positive neurons were adjacent to the main ARO-ir cell groups, such as the medial preoptic nucleus. the bed nucleus of the stria terminalis and the nucleus ventromedialis hypothalamic. Hove ever. examination of adjacent sections indicated that there is very little overlap between the NOS-immunoreactive and ARO-ir cell populations. This notion got further support by double-labeled sections where no double-labeled cells could be identified. In sections stained simultaneously by histochemistry for NADPH and immunohistochemistry for ARO, many NADPH-positive fibers and punctate structures were closely associated with ARO-ir perikarya. Taken together, the present data indicate that NOS is not or very rarely colocalized with ARO but that NOS inputs are closely associated with ARO-ir cells. Based on previous work in a variety of model systems. it can be hypothesized that these inputs modulate the expression or activity of ARO in the quail brain. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailModulation of steroid activity by transcription coactivators in songbirds
Charlier, Thierry ULg; Auger, Catherine J; Balthazart, Jacques ULg et al

in Hormones & Behavior (2003), 44

Songbirds have developed a specialized, steroid-dependent telencephalic vocal control system for the production of learned vocalization. Recent progress in the study of the mechanisms by which steroid ... [more ▼]

Songbirds have developed a specialized, steroid-dependent telencephalic vocal control system for the production of learned vocalization. Recent progress in the study of the mechanisms by which steroid receptors act on the eukaryotic genome has highlighted the role of a newly discovered protein family, the Nuclear Receptor Coactivators. More specifically, the CREB-binding protein (CBP) and the Steroid Receptor Coactivator-1 (SRC-1) have been shown to be actively involved in mediating steroid hormone action in the developing rat brain. The distribution of the coactivator SRC-1 was analyzed in canaries by in situ hybridization. A very broad but heterogeneous distribution of the transcript was observed, mainly in steroid-sensitive areas of the hypothalamus, the song control system and several catecholaminergic areas. The presence of SRC-1 in these regions was also confirmed by immunocytochemistry. A similar very high concentration of the coactivator CBP protein was also found in steroid-sensitive areas of the hypothalamus and in the song system. Sex differences in SRC-1 mRNA concentration were detected in HVC and in area X. Moreover, preliminary data obtained independently in starlings (CBP) and in quail (SRC-1) suggest that the expression of coactivators is regulated by steroids as well as by photoperiod. The presence of these steroid receptor coactivators in the telencephalic song control nuclei and in catecholaminergic cell groups that innervate the song system and their possible regulation by photoperiod and/or steroids support the idea that SRC-1 and CBP could play an important role in the control of singing behavior by modulating estrogen and androgen receptor action. [less ▲]

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See detailCloning and identification of functional domains in quail Brain aromatase
Charlier, Thierry ULg; Baillien, Michelle; Ball, Gregory F. et al

Poster (2003)

Recent evidence indicates that aromatase activity (AA) in the hypothalamus is not only modulated by slow (hours to days) genomic actions but also through fast (seconds to minutes) non-genomic mechanisms ... [more ▼]

Recent evidence indicates that aromatase activity (AA) in the hypothalamus is not only modulated by slow (hours to days) genomic actions but also through fast (seconds to minutes) non-genomic mechanisms. We recently showed that Calcium (Ca2+)-dependent phosphorylations catalyzed by multiple protein kinases including PKC, and possibly PKA and CAMK, rapidly down-regulate AA in quail hypothalamic homogenates. Western blotting experiments also indicated that phosphorylations affect the aromatase molecule itself but it was impossible to fully characterize the putative phosphorylation sites on the quail enzyme because its sequence was unknown. We therefore cloned and sequenced the quail brain aromatase. We identified a 1541-bp open reading frame that encodes a predicted 490-amino acid protein containing all functional domains previously described in mammalian and other avian aromatases. Multiple motifs match consensus sequences corresponding to several protein kinases including those that were shown to affect AA during pharmacological experiments with specific kinase inhibitors (e.g., PKC, PKA, MAPK, Myosine light chain kinase, Tyr. kinase). Another potential control pathway of AA, independent from phosphorylations, could involve a direct control by Ca2+-dependent calmodulin (CAM), as suggested by the identification in Western blots of CAM on purified aromatase from quail hypothalamic homogenates. Accordingly, two Ca2+-dependent calmodulin binding motifs (1-8-14b) as defined by Rhoads and Friedberg (FASEB, 1997, 11:331-340) are present and conserved in most vertebrates including quail aromatase. These results suggest that the phosphorylation of some residues as well as the direct binding of calmodulin on the aromatase protein represent part of the mechanism(s) underlying the rapid changes in AA. [less ▲]

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See detailThe activation of birdsong by testosterone - Multiple sites of action and role of ascending catecholamine projections
Ball, G. F.; Castelino, C. B.; Maney, D. L. et al

in Annals of the New York Academy of Sciences (2003), 1007

Birdsong is a species-typical stereotypic vocalization produced in the context of reproduction and aggression. Among temperate-zone songbirds, it is produced primarily by males, and its frequency and ... [more ▼]

Birdsong is a species-typical stereotypic vocalization produced in the context of reproduction and aggression. Among temperate-zone songbirds, it is produced primarily by males, and its frequency and quality are enhanced by the presence of the gonadal steroid hormone testosterone in the plasma. In the brain, the effects of testosterone on song behavior involve both estrogenic and androgenic metabolites of testosterone that are locally produced and act via their cognate receptors. Androgen, and in some cases estrogen, receptors are present in many specialized forebrain song control nuclei. Testosterone can regulate catecholamine steady-state levels and turnover in these song control regions. Tracing studies combined with immunocytochemistry for tyrosine hydroxylase (a marker of catecholamine synthesis) reveal several catecholamine cell groups that project to forebrain song control nuclei. These brain areas also express the mRNA for either androgen receptors or estrogen receptor alpha, and androgens enhance the expression of tyrosine hydroxylase. Dopaminergic cell groups that project to song nuclei express the protein product of the immediate early gene fos in association with the production of territorial song. Thus, testosterone may be acting on song behavior via these ascending catecholamine cell groups. Chemical lesioning studies suggest that noradrenergic projections to the song system are involved in the latency to produce song and the ability to discriminate conspecific from heterospecific song. The song control circuit may thus be modulated in significant ways via the androgen regulation of forebrain catecholamine systems. [less ▲]

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See detailSong activation by testosterone is associated with an increased catecholaminergic innervation of the song control system in female canaries
Appeltants, D.; Ball, G. F.; Balthazart, Jacques ULg

in Neuroscience (2003), 121(3), 801-814

In canaries, singing and a large number of morphological features of the neural system that mediates the learning, perception and production of song exhibit marked sex differences. Although these ... [more ▼]

In canaries, singing and a large number of morphological features of the neural system that mediates the learning, perception and production of song exhibit marked sex differences. Although these differences have been mainly attributed to sex-specific patterns of the action of testosterone and its metabolites, the mechanisms by which sex steroids regulate brain and behavior are far from being completely understood. Given that the density of immunoreactive catecholaminergic fibers that innervate telencephalic song nuclei in canaries is higher in males, which sing, than in females, which usually do not sing, we hypothesized that some of the effects induced by testosterone on song behavior are mediated through the action of the steroid on the catecholaminergic neurons which innervate the song control nuclei. Therefore, we investigated in female canaries the effects of a treatment with exogenous testosterone on song production, on the volume of song control nuclei, and on the catecholaminergic innervation of these nuclei as assessed by immunocytochemical visualization of tyrosine hydroxylase. Testosterone induced male-like singing in all females and increased by about 80% the volume of two telencephalic song control nuclei, the high vocal center (HVC) and the nucleus robustus archistriatalis (RA). Testosterone also significantly increased the fractional area covered by tyrosine hydroxylase-immunoreactive structures (fibers and varicosities) in most telencephalic song control nuclei (HVC, the lateral and medial parts of the magnocellular nucleus of the anterior neostriatum, the nucleus interfacialis, and to a lesser extent RA). By contrast, testosterone did not affect the catecholaminergic innervation of the telencephalic areas adjacent to HVC and RA. Together these data demonstrate that, in parallel to its effects on song behavior and on the morphology of the song control system, testosterone also regulates the catecholaminergic innervation of most telencephalic song control nuclei in canaries. The endocrine regulation of singing may thus involve the neuromodulatory action of specialized dopaminergic and/or noradrenergic projections onto several key parts of the song control system. (C) 2003 IBRO. Published by Elsevier Ltd. All rights reserved. [less ▲]

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See detailMultiple mechanisms control brain aromatase activity at the genomic and non-genomic level
Balthazart, Jacques ULg; Baillien, Michelle; Charlier, Thierry ULg et al

in Journal of Steroid Biochemistry & Molecular Biology (2003), 86

Evidence has recently accumulated indicating that aromatase activity in the preoptic area is modulated in parallel by both slow (hours to days) genomic and rapid (minutes to hours) non-genomic mechanisms ... [more ▼]

Evidence has recently accumulated indicating that aromatase activity in the preoptic area is modulated in parallel by both slow (hours to days) genomic and rapid (minutes to hours) non-genomic mechanisms. We review here these two types of control mechanisms and their potential contribution to various aspects of brain physiology in quail. High levels of aromatase mRNA, protein and activity (AA) are present in the preoptic area of this species where the transcription of aromatase is controlled mainly by steroids. Estrogens acting in synergy with androgens play a key role in this control and both androgen and estrogen receptors (ER; alpha and beta subtypes) are present in the preoptic area even if they are not necessarily co-localized in the same cells as aromatase. Steroids have more pronounced effects on aromatase transcription in males than in females and this sex difference could be caused, in part, by a sexually differentiated expression of the steroid receptor coactivator 1 in this area. The changes in aromatase concentration presumably control seasonal variations as well as sex differences in brain estrogen production. Aromatase activity in hypothalamic homogenates is also rapidly (within minutes) down-regulated by exposure to conditions that enhance protein phosphorylation such as the presence of high concentrations of calcium, magnesium and ATP. Similarly, pharmacological manipulations such as treatment with thapsigargin or stimulation of various neurotransmitter receptors (alpha-amino-3-hydroxy-methyl-4-isoxazole propionic acid (AMPA), kainate, and N-methyl-d-aspartate (NMDA)) leading to enhanced intracellular calcium concentrations depress within minutes the aromatase activity measured in quail preoptic explants. The effects of receptor stimulation are presumably direct: electrophysiological data confirm the presence of these receptors in the membrane of aromatase-expressing cells. Inhibitors of protein kinases interfere with these processes andWestern blotting experiments on brain aromatase purified by immunoprecipitation confirm that the phosphorylations regulating aromatase activity directly affect the enzyme rather than another regulatory protein. Accordingly, several phosphorylation consensus sites are present on the deduced amino acid sequence of the recently cloned quail aromatase. Fast changes in the local availability of estrogens in the brain can thus be caused by aromatase phosphorylation so that estrogen could rapidly regulate neuronal physiology and behavior. The rapid as well as slower processes of local estrogen production in the brain thus match well with the genomic and non-genomic actions of steroids in the brain. These two processes potentially provide sufficient temporal variation in the bio-availability of estrogens to support the entire range of established effects for this steroid. [less ▲]

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See detailThe neuroendocrinology of reproductive behavior in Japanese quail
Balthazart, Jacques ULg; Baillien, Michelle; Charlier, Thierry ULg et al

in Domestic Animal Endocrinology (2003), 25

Sex steroid hormones such as testosterone have widespread effects on brain physiology and function but one of their best characterized effects arguably involves the activation of male sexual behavior ... [more ▼]

Sex steroid hormones such as testosterone have widespread effects on brain physiology and function but one of their best characterized effects arguably involves the activation of male sexual behavior. During the past 20 years we have investigated the testosterone control of male sexual behavior in an avian species, the Japanese quail (Coturnix japonica).We briefly reviewhere the main features and advantages of this species relating to the investigation of fundamental questions in the field of behavioral neuroendocrinology, a field that studies inter-relationship among hormones, brain and behavior. Special attention is given to the intracellular metabolism of testosterone, in particular its aromatization into an estrogen, which plays a critical limiting role in the mediation of the behavioral effects of testosterone. Brain aromatase activity is controlled by steroids which increase the transcription of the enzyme, but afferent inputs that affect the intraneuronal concentrations of calcium also appear to have a pronounced effect on the enzyme activity through rapid changes in its phosphorylation status. The physiological significance of these slowgenomic and rapid, presumably non-genomic, changes in brain aromatase activity are also briefly discussed. [less ▲]

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See detailChanges in the arginine-vasopressin immunoreactive systems in male mice lacking a functional aromatase gene
Plumari, L.; Viglietti-Panzica, C.; Allieri, F. et al

in Journal of Neuroendocrinology (2002), 14(12), 971-978

In male rodents, the arginine-vasopressin-immunoreactive (AVP-ir) neurones of the bed nucleus of the stria terminalis (BNST) and medial amygdala are controlled by plasma testosterone levels (decreased ... [more ▼]

In male rodents, the arginine-vasopressin-immunoreactive (AVP-ir) neurones of the bed nucleus of the stria terminalis (BNST) and medial amygdala are controlled by plasma testosterone levels (decreased after castration and restored by exogenous testosterone). AVP transcription in these nuclei is increased in adulthood by a synergistic action of the androgenic and oestrogenic metabolites of testosterone and, accordingly, androgen and oestrogen receptors are present in both BNST and medial amygdala. We used knockout mice lacking a functional aromatase enzyme (ArKO) to investigate the effects of a chronic depletion of oestrogens on the sexually dimorphic AVP system. Wild-type (WT) and ArKO male mice were perfused 48 h after an i.c.v. colchicine injection and brain sections were then processed for AVP immunocytochemistry. A prominent decrease (but not a complete suppression) of AVP-ir structures was observed in the BNST and medial amygdala of ArKO mice by comparison with the WT. Similarly, AVP-ir fibres were reduced in the lateral septum of ArKO mice and but not in the medial preoptic area, a region where the AVP system is not sexually dimorphic in rats. No change was detected in the supraoptic and suprachiasmatic nuclei. However, a decrease in AVP-ir cell numbers was however, detected in one subregion of the paraventricular nucleus. These data support the hypothesis that the steroid-sensitive sexually dimorphic AVP system of the mouse forebrain is mainly under the control of aromatized metabolites of testosterone. [less ▲]

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See detailDopamine activates noradrenergic receptors in the preoptic area
Cornil, Charlotte ULg; Balthazart, Jacques ULg; Motte, Patrick ULg et al

in Journal of Neuroscience (2002), 22(21), 9320-9330

Dopamine (DA) facilitates male sexual behavior and modulates aromatase activity in the quail preoptic area (POA). Aromatase neurons in the POA receive dopaminergic inputs, but the anatomical substrate ... [more ▼]

Dopamine (DA) facilitates male sexual behavior and modulates aromatase activity in the quail preoptic area (POA). Aromatase neurons in the POA receive dopaminergic inputs, but the anatomical substrate that mediates the behavioral and endocrine effects of DA is poorly understood. Intracellular recordings showed that 100 muM DA hyperpolarizes most neurons in the medial preoptic nucleus (80%) by a direct effect, but depolarizes a few others (10%). DA-induced hyperpolarizations were not blocked by D1 or D2 antagonists (SCH-23390 and sulpiride). Extracellular recordings confirmed that DA inhibits the firing of most cells (52%) but excites a few others (24%). These effects also were not affected by DA antagonists (SCH-23390 and sulpiride) but were blocked by alpha(2)-(yohimbine) and alpha(1)-(prazosin) noradrenergic receptor antagonists, respectively. Two dopamine-beta-hydroxylase (DBH) inhibitors (cysteine and fusaric acid) did not block the DA-induced effects, indicating that DA is not converted into norepinephrine (NE) to produce its effects. The pK(B) of yohimbine for the receptor involved in the DA- and NE-induced inhibitions was similar, indicating that the two monoamines interact with the same receptor. Together, these results demonstrate that the effects of DA in the POA are mediated mostly by the activation of alpha(2) (inhibition) and alpha(1) (excitation) adrenoreceptors. This may explain why DA affects the expression of male sexual behavior through its action in the POA, which contains high densities of alpha(2)-noradrenergic but limited amounts of DA receptors. This study thus clearly demonstrates the existence of a cross talk within CNS catecholaminergic systems between a neurotransmitter and heterologous receptors. [less ▲]

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See detailLocalization of oestrogen receptors in the sensory and motor areas of the spinal cord in Japanese quail (Coturnix japonica)
Evrard, H. C.; Balthazart, Jacques ULg

in Journal of Neuroendocrinology (2002), 14(11), 894-903

In Japanese quail, the presence of aromatase (oestrogen synthase) in the dorsal horn of the spinal cord suggests that spinal sensory processes might be controlled by local actions of oestrogens. This is ... [more ▼]

In Japanese quail, the presence of aromatase (oestrogen synthase) in the dorsal horn of the spinal cord suggests that spinal sensory processes might be controlled by local actions of oestrogens. This is supported by the presence of oestrogen receptors and aromatase in the dorsal horn of the spinal cord in rats, and by the alteration of sensitivity by oestrogens in various mammalian species and also in canaries. We investigated whether oestrogens that are locally produced in the quail spinal cord can bind to specific receptors in the vicinity of their site of synthesis. We demonstrate the presence of numerous oestrogen receptor alpha-immunoreactive (ERalpha-ir) cell nuclei, predominantly in laminae II and, to a lesser extent, I and III of the dorsal horn of the spinal cord (i.e. in the area where aromatase was previously identified). ERalpha-ir cells were also seen in various parts of the intermediate zone (laminae V-VII). This presence of ERalpha-ir cells in the dorsal horn and intermediate zone fits in well with the distribution of ERalpha-ir cells in homologous areas in mammals, including rats. Only a few labelled cells were found in the ventral horn in the cervical, brachial, thoracic and first lumbar segments, but a conspicuous dense group of large ERalpha-ir cells was identified in lamina IX of the ventral horn in synsacral segments 8-10, which contain the motoneurones innervating the muscles of the cloacal gland. The presence of ERalpha-ir cells in lamina IX of these synsacral segments in quail contrasts with the finding that motoneurones innervating penile muscles in rats contain androgen, but not oestrogen receptors, and are influenced by androgens rather than by oestrogens. Together, these data suggest that spinal actions of oestrogens may modulate the sensory and motor systems that participate in reproduction, as well as other nonreproductive functions in quail. [less ▲]

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See detailContext-dependent effects of castration and testosterone treatment on song in male European starlings
Pinxten, R.; De Ridder, E.; Balthazart, Jacques ULg et al

in Hormones & Behavior (2002), 42(3), 307-318

Most seasonally breeding songbirds display dramatic seasonal fluctuations in plasma testosterone (T) levels and mate attraction behaviors, including song. However, males of some songbird species, such as ... [more ▼]

Most seasonally breeding songbirds display dramatic seasonal fluctuations in plasma testosterone (T) levels and mate attraction behaviors, including song. However, males of some songbird species, such as the European starling (Stumus vulgaris), continue to sing at high levels after the breeding season, when T levels are basal. In male starlings song during the breeding season functions mainly to attract mates, whereas song during the nonbreeding season appears unrelated to reproduction. This suggests that song produced in a context unrelated to female courtship, unlike song directed toward females, is not regulated by plasma T. In captive males housed in large outdoor aviaries we explored the relationship between plasma T and song produced during the breeding season within and outside a courtship context. This was achieved by determining the effects of castration and subsequent T treatment on song and mate attraction behaviors in both the presence and the absence of a female. Compared to intact males, castrated males did not show reduced song activity in the absence of a female for at least 6 months after the operation, strongly suggesting that the expression of noncourtship song is not regulated by plasma T. Likewise, we found that experimentally elevating T levels in castrated males did not affect noncourtship song rates. However, control castrated males receiving empty implants tended to show reduced noncourtship song rates after implantation. This may have been due to a suppressive effect caused by the presence of the T-implanted castrated males in the same aviary. In contrast, courtship singing was clearly controlled by plasma T: it was abolished by castration and restored by subsequent T replacement when males were housed both individually and in a group situation. High plasma levels of T also appeared necessary for the activation of three other behavioral traits critical for mate attraction, namely, nesthole occupancy, spending time (singing) in a nesthole, and carrying green nesting material into a nesthole. (C) 2002 Elsevier Science (USA). [less ▲]

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See detailThe aromatase knock-out mouse provides new evidence that estradiol is required during development in the female for the expression of sociosexual behaviors in adulthood
Bakker, Julie ULg; Honda, S. I.; Harada, N. et al

in Journal of Neuroscience (2002), 22(20), 9104-9112

We used estrogen-deficient aromatase knock-out (ArKO) mice to determine whether estrogens contribute to the development of the brain and behavior in females. Female mice of three different genotypes [i.e ... [more ▼]

We used estrogen-deficient aromatase knock-out (ArKO) mice to determine whether estrogens contribute to the development of the brain and behavior in females. Female mice of three different genotypes [i.e., wild type (WT), heterozygous (HET), and homozygous (ArKO)] were ovariectomized in adulthood and subsequently tested for odor preferences (choice: intact male vs estrous female) in a Y-maze. When treated with testosterone, ArKO females spent significantly less time sniffing odors (both volatile and nonvolatile) from either male or female stimuli compared with WT and HET females. When given direct access to anesthetized stimulus animals or when given a choice between odor and visual cues from both stimulus animals, ArKO females continued to spend less time investigating the stimuli compared with WT and HET females. These defects in olfactory investigation of ArKO females were partially corrected with estradiol treatment in adulthood. Estradiol-treated ArKO females no longer differed from WT and HET females in the time spent investigating either nonvolatile odors or the anogenital region of anesthetized animals. However, ArKO females still investigated volatile odors and/or visual cues less than WT and HET females. Sexual receptivity was severely impaired in ArKO females after treatments with estradiol and progesterone that successfully induced receptivity in WT and HET females. Furthermore, ArKO females showed diminished levels of male sexual behaviors, whereas WT and HET females readily mounted an estrous female. Together, these findings demonstrate that estrogen is required for normal female development. The concept that the female brain develops in the absence of any hormonal stimulation should therefore be reconsidered. [less ▲]

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See detailSexual partner preference requires a functional aromatase (Cyp19) gene in male mice
Bakker, Julie ULg; Honda, S.; Harada, N. et al

in Hormones & Behavior (2002), 42(2), 158-171

Sexual motivation, sexual partner preference, and sexual performance represent three different aspects of sexual behavior that are critical in determining the reproductive success of a species. Although ... [more ▼]

Sexual motivation, sexual partner preference, and sexual performance represent three different aspects of sexual behavior that are critical in determining the reproductive success of a species. Although the display of sexual behavior is under strict hormonal control in both sexes, the relative roles of androgen and estrogen receptors in activating the various components of male sexual behavior are still largely unknown. A recently developed mouse model that is deficient in estradiol due to targeted disruption of exons 1 and 2 of the Cyp19 gene (aromatase knockout (ArKO) mice) was used here to analyze the role of estradiol in the control of all three aspects of male sexual behavior. When tested in a Y-maze providing volatile olfactory cues, male ArKO mice did not show a preference for the odors from an estrous female over those from an intact male, whereas wildtype (WT) and heterozygous (HET) males clearly preferred to sniff estrous odors. When provided with visual and olfactory cues, male ArKO mice also failed to show a preference for an estrous female when given a choice between an estrous female and an empty arm. However, sexual partner preferences of male ArKO mice were not sex-reversed: they did not prefer to investigate an intact male over an estrous female or empty arm. Thus, male ArKO mice seemed to have general deficits in discriminating between conspecifics by using olfactory and visual cues. Male coital behavior was also severely impaired in male ArKO mice: they displayed significantly fewer mounts, intromissions, and ejaculations than WT and HET males. Latencies to first mount or intromission were also significantly longer in ArKO males compared to WT and HET males, in addition to them showing less interest in investigating olfactory and visual cues in a Y-maze, suggesting that they were sexually less motivated. However, three out of seven male ArKO mice were capable of siring litters provided they were housed with a female for a prolonged period of time. In conclusion, aromatization of testosterone to estradiol appears to be essential for sexual motivation and sexual partner preference. By contrast, estradiol may play only a limited role in the expression of male coital behaviors. (C) 2002 Elsevier Science (USA). [less ▲]

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See detailNoradrenergic control of auditory information processing in female canaries
Appeltants, D.; Del Negro, C.; Balthazart, Jacques ULg

in Behavioural Brain Research (2002), 133(2), 221-235

An ethological procedure, based on the study of the sexual responsiveness of female canaries (Serinus canaria) to song playbacks was used to investigate the function of central noradrenergic inputs in the ... [more ▼]

An ethological procedure, based on the study of the sexual responsiveness of female canaries (Serinus canaria) to song playbacks was used to investigate the function of central noradrenergic inputs in the processing of auditory information. The effects of a noradrenergic denervation on sexual responses was analyzed in females exposed to playbacks of biological relevant auditory stimuli, i.e. sexually stimulating songs, presented alone or masked by auditory distractors. A decrease in behavioral responsiveness was observed as a function of the amount of masking distractors indicating that female canaries have the perceptual ability to discriminate and selectively attend to biologically relevant songs. After the systemic administration of DSP-4, a specific noradrenergic neurotoxin, females exhibited an overall decrease in sexual responsiveness to songs masked or not by distractors. No effect of DSP-4 were detected on the motor activity nor on reproductive behaviors. These results indicate that central noradrenergic inputs modulate the sexual behavior of female canaries by affecting the auditory processing of relevant information contained in sexually stimulating songs. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailThe parvocellular vasotocin system of Japanese quail: A developmental and adult model for the study of influences of gonadal hormones on sexually differentiated and behaviorally relevant neural circuits
Panzica, G. C.; Balthazart, Jacques ULg; Pessatti, M. et al

in Environmental Health Perspectives (2002), 110(Suppl. 3), 423-428

Vasotocin (VT; the antidiuretic hormone of birds) is synthesized by diencephalic magnocellular neurons projecting to the neurohypophysis. A sexually dimorphic system of VT-immunoreactive (ir ... [more ▼]

Vasotocin (VT; the antidiuretic hormone of birds) is synthesized by diencephalic magnocellular neurons projecting to the neurohypophysis. A sexually dimorphic system of VT-immunoreactive (ir) parvocellular elements has been described within the male medial preoptic nucleus (POM) and the nucleus of the stria terminalis, pars medialis (BSTm). VT-ir fibers are present in many diencephalic and extradiencephalic locations, and quantitative morphometric analyses demonstrated their sexually dimorphic distribution in regions involved in the control of different aspects of reproduction. Moreover, systemic or intracerebroventricular injections of VT markedly inhibit the expression of some aspects of male sexual behavior. In adult animals, circulating levels of testosterone (T) have a profound influence on the VT immunoreactivity within BSTm, POM, and lateral septum. Castration markedly decreases the immunoreaction, whereas T-replacement therapy restores a situation similar to the intact birds. We observed no changes in gonadectomized females treated with T. These changes parallel similar changes in male copulatory behavior (not present in castrated male quail, fully expressed in castrated, T-treated males). The restoration by T of the VT immunoreactivity in castrated male quail could be fully mimicked by a treatment with estradiol (E-2), suggesting that the aromatization of T into E-2 may play a key limiting role in both the activation of male sexual behavior and the induction of VT synthesis. This dimorphism has an organizational nature: administration of E-2 to quail embryos (a treatment that abolishes male sexual behavior) results in a dramatic decrease of the VT immuno reactivity in sexually dimorphic regions. Conversely, the inhibition of E-2 synthesis during embryonic life (a treatment that stimulates the expression of male copulatory behavior in treated females exposed in adulthood to T) results in a malelike distribution of VT immunoreactivity. The VT parvocellular system of the Japanese quail can therefore be considered an accurate marker of the sexual differentiation of brain circuits mediating copulatory behavior and could be a very sensitive indicator of the activity of estrogenlike substances on neural circuits. [less ▲]

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See detailThe medial preoptic nucleus receives vasotocinergic inputs in male quail: a tract-tracing and immunocytochemical study
Absil, Philippe ULg; Papello, M.; Viglietti-Panzica, C. et al

in Journal of Chemical Neuroanatomy (2002), 24(1), 27-39

The sexually dimorphic testosterone-sensitive medial preoptic nucleus (POM) of quail can be identified by the presence of a dense network of vasotocinergic fibers. This innervation is sexually ... [more ▼]

The sexually dimorphic testosterone-sensitive medial preoptic nucleus (POM) of quail can be identified by the presence of a dense network of vasotocinergic fibers. This innervation is sexually differentiated (present in males only) and testosterone sensitive. The origin of these fibers has never been formally identified although their steroid sensitivity Suggests that they originate in parvocellular vasotocinergic neurons that are found in quail only in the medial part of the bed nucleus striae terminalis (BSTm) and in smaller numbers within the POM itself. We report here that following injections of a retrograde tracer into the POM of male quail, large populations of retrogradely labeled cells can be identified in the BSTm. The POM also receives afferent projections from magnocellular vasotocinergic nuclei, the supraoptic and paraventricular nuclei. Double labeling for vasotocin immunoreactivity of the retrogradely labeled sections failed however to clearly identify magnocellular vasotocin-immunoreactive cells that were retrogradely labeled from POM. In contrast a substantial population of vasotocin-immunoreactive neurons in the BSTm contained tracer retrogradely transported from the POM. These data therefore demonstrate that a significant part of the vasotocinergic innervation of the quail POM originates in the medial part of the BST. An intrinsic innervation could however also contribute to this network. This interaction between BSTm and POM could play a key role in the control of male-typical sexual behavior and in its sex dimorphism in quail. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailThe assessment of nociceptive and non-nociceptive skin sensitivity in the Japanese quail (Coturnix japonica)
Evrard, H. C.; Balthazart, Jacques ULg

in Journal of Neuroscience Methods (2002), 116(2), 135-146

We evaluated the efficacy of two nociceptive tests, the hot water (HWT) and the foot pressure tests (FPT), and one non-nociceptive test (Semmes-Weinstein test, SWT) in assessing skin sensitivity in ... [more ▼]

We evaluated the efficacy of two nociceptive tests, the hot water (HWT) and the foot pressure tests (FPT), and one non-nociceptive test (Semmes-Weinstein test, SWT) in assessing skin sensitivity in conscious Japanese quail. All stimuli elicited a reflex-like, strongly reproducible response. Responses in the HWT and FPT were identified as typical nocifensive flight-fight behavior. In untreated birds, these responses occurred at temperatures and forces described previously as noxious. In the SWT, two responses were observed: a slight ruffling of the cloacal gland feathers due to the stimulation of the cloacal gland, and a brief extension of the limbs due to the stimulation of the ilium or pectoral apterium. These reactions occurred at intensities recognized as innocuous. Morphine significantly altered the response latency and threshold in the HWT and FPT, but had no effect in the SWT. However, the SWT response threshold was significantly increased by local application of xylocaine. Taken together, the pattern of the responses, the intensities and the effects of morphine and xylocaine allowed to distinguish between nociceptive and non-nociceptive tests. They also demonstrate the efficacy of these tests to evaluate skin sensitivity in quail and to assess its modulation by chemical factors that affect somatosensory processes. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailInteractions between aromatase (estrogen synthase) and dopamine in the control of male sexual behavior in quail
Balthazart, Jacques ULg; Baillien, M.; Ball, G. F.

in Comparative Biochemistry & Physiology Part B (2002), 132(1), 37-55

In male quail, like in other vertebrates including rodents, testosterone acting especially through its estrogenic metabolites is necessary for the activation of male sexual behavior. Also, the ... [more ▼]

In male quail, like in other vertebrates including rodents, testosterone acting especially through its estrogenic metabolites is necessary for the activation of male sexual behavior. Also, the administration of dopamine agonists and antagonists profoundly influences male sexual behavior. How the steroid-sensitive neural network and dopamine interact physiologically, remains largely unknown. It is often implicitly assumed that testosterone or its metabolite estradiol, stimulates male sexual behavior via the modification of dopaminergic transmission. We have now identified in quail two possible ways in which dopamine could potentially affect sexual behavior by modulating the aromatization of testosterone into an estrogen. One is a long-acting mechanism that presumably involves the modification of dopaminergic transmission followed by the alteration of the genomic expression of aromatase. The other is a more rapid mechanism that does not appear to be dopamine receptor-mediated and may involve a direct interaction of dopamine with aromatase (possibly via substrate competition). We review here the experimental data supporting the existence of these controls of aromatase activity by dopamine and discuss the possible contribution of these controls to the activation of male sexual behavior. (C) 2002 Elsevier Science Inc. All rights reserved. [less ▲]

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See detailThe origin of catecholaminergic inputs to the song control nucleus RA in canaries
Appeltants, D.; Ball, G. F.; Balthazart, Jacques ULg

in Neuroreport (2002), 13(5), 649-653

Song control nuclei in oscines receive dense catecholaminergic inputs but their anatomical origin is poorly understood. We analyzed catecholaminergic inputs to the nucleus robustus archistriatalis (RA) in ... [more ▼]

Song control nuclei in oscines receive dense catecholaminergic inputs but their anatomical origin is poorly understood. We analyzed catecholaminergic inputs to the nucleus robustus archistriatalis (RA) in canaries by retrograde tract-tracing combined with immunocytochemistry for tyrosine hydroxylase. In both sexes, dopaminergic inputs to RA come mostly from the A1 1 (mesencephalic central gray) and A10 (area ventralis of Tsai) cell groups but the locus coeruleus and subcoeruleus (A6) also send noradrenergic projections to RA. No input originates in the hypothalamic and in the A5 to A1 catecholaminergic groups. These findings and previous work on the high vocal center (HVc) indicate that the two major nuclei of the motor pathway controlling song production (RA and HVc) receive catecholaminergic inputs of similar origins. [less ▲]

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