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See detailActivational effects of estradiol and dihydrotestosterone on social recognition and the arginine-vasopressin immunoreactive system in male mice lacking a functional aromatase gene.
Pierman, S.; Sica, M.; Allieri, F. et al

in Hormones and Behavior (2008), 54(1), 98-106

In rodents, parts of the arginine-vasopressin (AVP) neuronal system are sexually dimorphic with males having more AVP-immunoreactive cells/fibers than females. This neuropeptide neuronal system is highly ... [more ▼]

In rodents, parts of the arginine-vasopressin (AVP) neuronal system are sexually dimorphic with males having more AVP-immunoreactive cells/fibers than females. This neuropeptide neuronal system is highly sensitive to steroids and has been proposed to play an important role in the processing of olfactory cues critical to the establishment of a social memory. We demonstrate here that gonadally intact male aromatase knockout (ArKO) mice, which cannot aromatize androgens into estrogens due to a targeted mutation in the aromatase gene, showed severe deficits in social recognition as well as a reduced AVP-immunoreactivity in several brain regions. To determine whether this reduction is due to a lack of organizational or activational effects of estrogens, we assessed social recognition abilities and AVP-immunoreactivity in male ArKO and wild-type (WT) mice when treated with estradiol benzoate (EB) in association with dihydrotestosterone propionate (DHTP) in adulthood. Adult treatment with EB and DHTP restored social recognition abilities in castrated ArKO males since they showed normal female-oriented ultrasonic vocalizations and were able to recognize an unfamiliar female using a habituation-dishabituation paradigm. Furthermore, adult treatment also restored AVP-immunoreactivity in the lateral septum of ArKO males to levels observed in intact WT males. These results suggest that social recognition in adulthood and stimulation of AVP expression in the adult mouse forebrain depend predominantly on the estrogenic metabolite of testosterone. Furthermore, our results are in line with the idea that the organization of the AVP system may depend on androgen or sex chromosomes rather than estrogens. [less ▲]

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See detailActivational effects of estradiol on the arginine-vasopressin immunoreactive system in the forebrain of male mice
Allieri, F.; Sica, M.; Bakker, Julie ULg et al

in Hormones & Behavior (2004, June), 46(1), 84

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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 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 detailSteroid-induced plasticity in the sexually dimorphic vasotocinergic innervation of the avian brain: behavioral implications
Panzica, G. C.; Aste, N.; Castagna, C. et al

in Brain Research Reviews (2001), 37(1-mars Sp. Iss. SI), 178-200

Vasotocin (VT, the antidiuretic hormone of birds) is synthesized by diencephalic magnocellular neurons projecting to the neurohypophysis. In addition, in male quail and in other oscine and non-oscine ... [more ▼]

Vasotocin (VT, the antidiuretic hormone of birds) is synthesized by diencephalic magnocellular neurons projecting to the neurohypophysis. In addition, in male quail and in other oscine and non-oscine birds, a sexually dimorphic group of VT-immunoreactive (ir) parvocellular neurons is located in a region homologous to the mammalian nucleus of the stria terminalis, pars medialis (BSTm) and in the medial preoptic nucleus (POM). These cells are not visible in females. VT-ir fibers are present in many diencephalic and extradiencephalic locations. Quantitative morphometric analyses demonstrate that, in quail, these elements are expressed in a sexually dimorphic manner (males>females) in regions involved in the control of different aspects of reproduction: i.e., the POM (copulatory behavior), the lateral septum (secretion of gonadotropin-releasing hormone [GnRH]), the nucleus intercollicularis (control of vocalizations), and the locus coeruleus (the main noradrenergic center of the avian brain). In many of these regions,VT-ir fibers are closely related to aromatase-ir, GnRH-ir, or estrogen receptor-expressing neurons. This dimorphism has an organizational nature: administration of estradiol-benzoate to quail embryos (a treatment that abolishes male sexual behavior) results in a dramatic decrease of the VT-immunoreactivity in all sexually dimorphic regions of the male quail brain. Conversely, the inhibition of estradiol (E,) synthesis during embryonic life (a treatment that stimulates the expression of male copulatory behavior in adult testosterone (T)-treated females) results in a male-like distribution of VT-ir cells and fibers. Castration markedly decreases the immunoreactivity in both the VT-immunopositive elements of the BSTm and the innervation of the SL and POM, whereas T-replacement therapy restores the VT immunoreactivity to a level typical of intact birds. These changes reflect modifications of VT mRNA concentrations (and probably synthesis) as demonstrated by in situ hybridization and they are paralleled by similar changes in male copulatory behavior (absent in castrated male quail, fully expressed in CX+T males). The aromatization of T into estradiol (E-2) also controls VT expression and, in parallel limits the activation of male sexual behavior by T. In castrated male quail, the restoration by T of the VT immunoreactivity in POM, BSTm and lateral septum could be fully mimicked by a treatment with E-2, but the androgen 5alpha-dihydrotestosterone (DHT) had absolutely no effect on the VT immunoreactivity in these conditions. At the doses used in this study, DHT also did not synergize with E, to enhance the density of VT immunoreactive structures. Systemic or i.c.v. injections of VT markedly inhibit the expression of all aspects of male sexual behavior. VT, presumably, does not simply represent one step in the biochemical cascade of events that is induced by T in the brain and leads to the expression of male sexual behavior. Androgens and estrogens presumably affect reproductive behavior both directly, by acting on steroid-sensitive neurons in the preoptic area, and indirectly, by modulating peptidergic (specifically vasotocinergic) inputs to this and other areas. The respective contribution of these two types of actions and their interaction deserves further analysis. (C) 2001 Elsevier Science BY All rights reserved. [less ▲]

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See detailVasotocinergic Innervation of Areas Containing Aromatase-Immunoreactive Cells in the Quail Forebrain
Balthazart, Jacques ULg; Absil, Philippe ULg; Viglietti-Panzica, C. et al

in Journal of Neurobiology (1997), 33(1), 45-60

In the male quail forebrain, aromatase-immunoreactive (ARO-ir) elements are clustered within the sexually dimorphic medial preoptic nucleus (POM), nucleus striae terminalis (nST), nucleus accumbens (nAc ... [more ▼]

In the male quail forebrain, aromatase-immunoreactive (ARO-ir) elements are clustered within the sexually dimorphic medial preoptic nucleus (POM), nucleus striae terminalis (nST), nucleus accumbens (nAc), and ventromedial and tuberal hypothalamus. These ARO-ir cells are sensitive to testosterone and its metabolites: Their number and size increase after exposure to these steroids. The POM and lateral septum are also characterized by a dense vasotocinergic innervation that is also sensitive to testosterone. We analyzed here the anatomical relationships between ARO-ir elements and VT-ir fibers in the quail prosencephalon. Sequential staining for vasotocin, aromatase, or vasotocin plus aromatase was performed on adjacent 30-microm-thick cryostat sections. High concentrations of thin VT-ir fibers were observed within the POM, nST, lateral septum, periventricular mesencephalic central gray, and ventromedial and tuberal hypothalamus. There was a close correspondence between the extension of the ARO-ir cells and of VT-ir fibers. In double-labeled sections, all clusters of ARO-ir cells with the exception of those located in the nAc were embedded in a dense network of VT-ir fibers. Many of the VT-ir terminals appeared to end in the neuropile surrounding ARO-ir elements rather than directly on their cell bodies. This study supports the idea that the testosterone-dependent aromatase system is directly innervated by a testosterone-dependent peptidergic system. Aromatase-containing cells could therefore be modulated by steroids both directly and indirectly through the vasotocin system. Alternatively, this neuroanatomical arrangement may mediate the control of vasotocin synthesis or release by steroids. Functional studies demonstrate that both aromatase and vasotocin affect reproductive behavior in quail, and the present data provide anatomical support for the integration of these effects. [less ▲]

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See detailAfferent and Efferent Connections of the Sexually Dimorphic Medial Preoptic Nucleus of the Male Quail Revealed by in Vitro Transport of Dii
Balthazart, Jacques ULg; Dupiereux, V.; Aste, N. et al

in Cell & Tissue Research (1994), 276(3), 455-75

The medial preoptic nucleus of the Japanese quail is a testosterone-sensitive structure that is involved in the control of male copulatory behavior. The full understanding of the role played by this ... [more ▼]

The medial preoptic nucleus of the Japanese quail is a testosterone-sensitive structure that is involved in the control of male copulatory behavior. The full understanding of the role played by this nucleus in the control of reproduction requires the identification of its afferent and efferent connections. In order to identify neural circuits involved in the control of the medial preoptic nucleus, we used the lipophilic fluorescent tracer DiI implanted in aldheyde-fixed tissue. Different strategies of brain dissection and different implantation sites were used to establish and confirm afferent and efferent connections of the nucleus. Anterograde projections reached the tuberal hypothalamus, the area ventralis of Tsai, and the substantia grisea centralis. Dense networks of fluorescent fibers were also seen in several hypothalamic nuclei, such as the anterior medialis hypothalami, the paraventricularis magnocellularis, and the ventromedialis hypothalami. A major projection in the dorsal direction was also observed from the medial preoptic nucleus toward the nucleus septalis lateralis and medialis. Afferents to the nucleus were seen from all these regions. Implantation of DiI into the substantia grisea centralis also revealed massive bidirectional connections with a large number of more caudal mesencephalic and pontine structures. The substantia grisea centralis therefore appears to be an important center connecting anterior levels of the brain to brain-stem nuclei that may be involved in the control of male copulatory behavior. [less ▲]

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See detailSexual differentiation and hormonal control of the sexually dimorphic medial preoptic nucleus in the quail.
Panzica, G. C.; Viglietti-Panzica, C.; Calacagni, M. et al

in Brain Research (1987), 416(1), 59-68

We recently identified a sexually dimorphic nucleus in the preoptic region of the Japanese quail, the medial preoptic nucleus (POM), which is significantly larger in males than in females. In the present ... [more ▼]

We recently identified a sexually dimorphic nucleus in the preoptic region of the Japanese quail, the medial preoptic nucleus (POM), which is significantly larger in males than in females. In the present study, we investigated the hormonal control of this morphological neuroanatomical difference and the possible relationships between the sexual dimorphism in POM volume and in copulatory behavior. Treatments which are known to affect sexual behavior were thus applied to different groups of birds and the POM volume was then measured. In one experiment, male and female quails were either gonadectomized, gonadectomized and treated with testosterone or left intact. The larger size of the POM in males was confirmed and treatments significantly affected the nucleus size which was decreased by gonadectomy and restored by testosterone treatment in both sexes to a level similar to that seen in intact males. In two other experiments, eggs were injected with estradiol benzoate on day 9 of incubation and the POM volume was measured in adulthood either in intact birds or in gonadectomized birds receiving a replacement therapy with testosterone. Despite the fact that estradiol benzoate treatment completely suppressed copulatory behavior, it did not affect the volume of the POM or slightly increased it. These data thus show that the POM volume is controlled by testosterone levels in adulthood and could thus be an interesting model for the study of the effects of steroids on the brain. [less ▲]

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See detailA sexually dimorphic nucleus in the quail preoptic area.
Viglietti-Panzica, C.; Panzica, G. C.; Fiori, M. G. et al

in Neuroscience Letters (1986), 64(2), 129-34

The cytoarchitectural analysis of the preoptic-anterior hypothalamic region of the Japanese quail reveals a sexual dimorphism in the total volume of the medial preoptic nucleus (significantly larger in ... [more ▼]

The cytoarchitectural analysis of the preoptic-anterior hypothalamic region of the Japanese quail reveals a sexual dimorphism in the total volume of the medial preoptic nucleus (significantly larger in males than in females). Different nuclei of the region (dorsal preopticus, suprachiasmaticus) do not show any statistically significant difference. The sex-related difference is more consistent comparing the distribution of dark volume. This last is due to a larger number of cells containing high amount of Nissl's substance in male than in female. Present findings represent the first example of sexual dimorphism in the avian hypothalamus. [less ▲]

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