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

in Journal of chemical neuroanatomy (2013)

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

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

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See detailIntroduction to the chemical neuroanatomy of birdsong.
Ball, Gregory F; Balthazart, Jacques ULg

in Journal of Chemical Neuroanatomy (2010), 39(2), 67-71

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See detailSeasonal and hormonal modulation of neurotransmitter systems in the song control circuit.
Ball, Gregory F; Balthazart, Jacques ULg

in Journal of Chemical Neuroanatomy (2010), 39(2), 82-95

In the years following the discovery of the song system, it was realized that this specialized circuit controlling learned vocalizations in songbirds (a) constitutes a specific target for sex steroid ... [more ▼]

In the years following the discovery of the song system, it was realized that this specialized circuit controlling learned vocalizations in songbirds (a) constitutes a specific target for sex steroid hormone action and expresses androgen and (for some nuclei) estrogen receptors, (b) exhibits a chemical neuroanatomical pattern consisting in a differential expression of various neuropeptides and neurotransmitters receptors as compared to surrounding structures and (c) shows pronounced seasonal variations in volume and physiology based, at least in the case of HVC, on a seasonal change in neuron recruitment and survival. During the past 30 years numerous studies have investigated how seasonal changes, transduced largely but not exclusively through changes in sex steroid concentrations, affect singing frequency and quality by modulating the structure and activity of the song control circuit. These studies showed that testosterone or its metabolite estradiol, control seasonal variation in singing quality by a direct action on song control nuclei. These studies also gave rise to the hypothesis that the probability of song production in response to a given stimulus (i.e. its motivation) is controlled through effects on the medial preoptic area and on catecholaminergic cell groups that project to song control nuclei. Selective pharmacological manipulations confirmed that the noradrenergic system indeed plays a role in the control of singing behavior. More experimental work is, however, needed to identify specific genes related to neurotransmission that are regulated by steroids in functionally defined brain areas to enhance different aspects of song behavior. [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 detailThe microtubule-associated protein doublecortin is broadly expressed in the telencephalon of adult canaries
Boseret, Géraldine ULg; Ball, G. F.; Balthazart, Jacques ULg

in Journal of Chemical Neuroanatomy (2007), 33(3), 140-154

The protein doublecortin (DCX) is expressed in post-mitotic migrating and differentiating neurons in the developing vertebrate brain and, as a part of the microtubule machinery, is required for neuronal ... [more ▼]

The protein doublecortin (DCX) is expressed in post-mitotic migrating and differentiating neurons in the developing vertebrate brain and, as a part of the microtubule machinery, is required for neuronal migration. DCX expression is generally maximal during embryonic and early post-natal life but decreases markedly and almost disappears in older animals in parallel with the major decrease or cessation of neurogenesis. In several seasonally breeding songbird species such as canaries, the volume of several song control nuclei in the brain varies seasonally such that the largest nuclei are observed in the late spring and early summer. This variation is based on changes in cell size, dendritic branching, and, in nucleus HVC, on the incorporation of neurons newly born in adulthood. Because songbirds maintain an active neurogenesis and neuronal incorporation in their telencephalon throughout their lives, we investigated here the distribution of DCX-immunoreactive (ir) structures in the brain of adult male canaries. Densely stained DCX-ir cells were found exclusively in parts of the telencephalon that are known to incorporate new neurons in adulthood, in particular the nidopallium. Within this brain region, the boundaries of the song control nucleus HVC could be clearly distinguished from surrounding structures by a higher density of DCX-ir structures. In most telencephalic areas, about two thirds of these cells displayed a uni- or bipolar fusiform morphology suggesting they were migrating neurons. The rest of the DCX-ir cells in the telencephalon were larger and had a round multipolar morphology. No such staining was found in the rest of the brain. The broad expression of DCX specifically in adult brain structures that exhibit the characteristic of active incorporation of new neurons suggests that DCX plays a key role in the migration of new neurons in the brain of adult songbirds as it presumably does during ontogeny. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailNeuroanatomical specificity of sex differences in expression of aromatase mRNA in the quail brain
Voigt, C.; Ball, G. F.; Balthazart, Jacques ULg

in Journal of Chemical Neuroanatomy (2007), 33(2), 75-86

In birds and mammals, aromatase activity in the preoptic-hypothalamic region (HPOA) is usually higher in males than in females. It is, however, not known whether the enzymatic sex difference reflects the ... [more ▼]

In birds and mammals, aromatase activity in the preoptic-hypothalamic region (HPOA) is usually higher in males than in females. It is, however, not known whether the enzymatic sex difference reflects the differential activation of aromatase transcription or some other control mechanism. Although sex differences in aromatase activity are clearly documented in the HPOA of Japanese quail (Coturnix japonica), only minimal or even no differences at all were observed in the number of aromatase-immunoreactive (ARO-ir) cells in the medial preoptic nucleus (POM) and in the medial part of the bed nucleus striae terminalis (BSTM). We investigated by in situ hybridization the distribution and possible sex differences in aromatase mRNA expression in the brain of sexually active adult quail. The distribution of aromatase mRNA matched very closely the results of previous immunocytochemical studies with the densest signal being observed in the POM, BSTM and in the mediobasal hypothalamus (MBH). Additional weaker signals were detected in the rostral forebrain, arcopallium and mesencephalic regions. No sex difference in the optical density of the hybridization signal could be found in the POM and MBH but the area covered by mRNA was larger in males than in females, indicating a higher overall expression in males. In contrast, in the BSTM, similar areas were covered by the aromatase expression in both sexes but the density of the signal was higher in females than in males. The physiological control of aromatase is thus neuroanatomically specific and with regard to sex differences, these controls are at least partially different if one compares the level of transcription, translation and activity of the enzyme. These results also indirectly suggest that the sex difference in aromatase enzyme activity that is present in the quail HPOA largely results from differentiated controls of enzymatic activity rather than differences in enzyme concentration. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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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 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 detailDistribution of aromatase immunoreactivity in the forebrain of red-sided garter snakes at the beginning of the winter dormancy
Krohmer, R. W.; Bieganski, G. J.; Baleckaitis, D. D. et al

in Journal of Chemical Neuroanatomy (2002), 23(1), 59-71

Until recently, it has been difficult to identify the exact location of aromatase containing cells in the brain. The development of new antibodies has provided a sensitive tool to analyze the distribution ... [more ▼]

Until recently, it has been difficult to identify the exact location of aromatase containing cells in the brain. The development of new antibodies has provided a sensitive tool to analyze the distribution of aromatase immunoreactive (ARO-ir) material at a cellular level of resolution. In the present study we examined, for the first time, the distribution of ARO-ir cells in the brain of a reptile, the red-sided garter snake, at the beginning of the winter dormancy. ARO-ir cells were found at all rostro-caudal levels in the red-sided garter snake brain. Although weakly stained cells were distributed throughout the brain, more intensely immunoreactive cells were primarily concentrated in the preoptic area, anterior hypothalamus, septum and nucleus sphericus. Although androgens are elevated upon emergence from hibernation in the male red-sided garter snake, initiation of courtship behavior appears to be independent of direct androgen control. To date, the only known stimulus found to initiate courtship is a period of low temperature dormancy followed by exposure to warm temperatures. Circumstantial data, however, suggest an indirect role in the activation of male copulatory behavior for estrogenic metabolites of testosterone produced in the brain by aromatization during the winter dormancy. This study provides the first documentation of the distribution of ARO-ir cells in a reptilian species and demonstrates that while the aromatase enzyme occurs in most regions of the brain, the ARO-ir cells that appear to contain the highest concentration of enzyme are clustered in brain areas classically associated with the control of courtship behavior and mating in vertebrates. These data are consistent with the idea that estrogens locally produced in the brain may participate in some way to the activation of sexual behavior in this species also. This notion should now be experimentally tested by analyzing annual changes in aromatase activity and immunoreactivity and assessing the effects of pharmacological blockade of the enzyme activity at different times of the year. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailIdentification of the Origin of Catecholaminergic Inputs to Hvc in Canaries by Retrograde Tract Tracing Combined with Tyrosine Hydroxylase Immunocytochemistry
Appeltants, D.; Absil, Philippe ULg; Balthazart, Jacques ULg et al

in Journal of Chemical Neuroanatomy (2000), 18(3), 117-33

The telencephalic nucleus HVc (sometimes referred to as the high vocal center) plays a key role in the production and perception of birdsong. Although many afferent and efferent connections to this ... [more ▼]

The telencephalic nucleus HVc (sometimes referred to as the high vocal center) plays a key role in the production and perception of birdsong. Although many afferent and efferent connections to this nucleus have been described, it has been clear for many years, based on chemical neuroanatomical criteria, that there are projections to this nucleus that remain undescribed. A variety of methods including high performance liquid chromatography, immunohistochemistry and receptor autoradiography have identified high levels of catecholamine transmitters, the presence of enzymes involved in the synthesis of catecholamines such as tyrosine hydroxylase and a variety of catecholamine receptor sub-types in the HVc of several songbird species. However, no definitive projections to HVc have been described from cells groups known to synthesize catecholamines. These projections were analyzed in the present study by retrograde tract tracing combined with immunocytochemistry for tyrosine hydroxylase. The origin of the catecholaminergic inputs to HVc were determined based exclusively on birds in which injections of the retrograde tracer (latex fluospheres) were confined within the cytoarchitectonic boundaries of the nucleus. Retrogradely transported latex fluospheres were found mainly in cells of two dopaminergic nuclei, the mesencephalic central gray (A11) and, to a lesser extend, the area ventralis of Tsai (A10; homologous to the ventral tegmental area of mammals). A few retrogradely-labelled cells were also found in the noradrenergic nucleus subceruleus (A6). Most of these retrogradely-labelled cells were also tyrosine hydroxylase-positive. Other catecholaminergic nuclei were devoid of retrograde label. These data converge with others studies to indicate that HVc receives discrete dopaminergic and noradrenergic inputs. These inputs may influence the steroid regulation of HVc, attentional processes related to song and modulate sensory inputs to the song system. [less ▲]

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See detailCalcium binding protein calcyphosin in dog central astrocytes and ependymal cells and in peripheral neurons
Halleux, P.; Schurmans, Stéphane ULg; Schiffmann, S. N. et al

in Journal of Chemical Neuroanatomy (1998), 15

Calcyphosine is a calcium binding protein discovered in the dog thyroid in 1979. Calcyphosine mRNA and immunoreactivity were detected using Western and Northern blotting in the cerebral cortex, cerebral ... [more ▼]

Calcyphosine is a calcium binding protein discovered in the dog thyroid in 1979. Calcyphosine mRNA and immunoreactivity were detected using Western and Northern blotting in the cerebral cortex, cerebral white matter and cerebellum. Using immunohistochemistry and in situ hybridization, both are present in ependymal cells, choroid plexus cells and several types of astrocytes of the subependymal cerebral layer, the cerebellar Bergmann layer, the retinal ganglion cell layer, the optic nerve and the posterior pituitary. Both are also present in neurons of nasal olfactory mucosa, enteric Auerbach and Meissner plexuses, orthosympathic and spinal cord ganglia as well as in endocrine cells of neural crest origin in the adrenal medulla. Calcyphosine immunoreactive astrocytes were also present mainly in hemispheric cerebral gray and white matter, hemispheric subcortical structures, brain stem and spinal cord. These results show that calcyphosine is a characteristic calcium binding protein of astrocytes and ependymal cells in the central nervous system and of neurons in the peripheral nervous system. This is of interest in view of the importance of calcium regulation in these cells, and since calcyphosine a calcium binding protein phosphorylated by cAMP dependent process, may be an intermediate between cAMP and inositol phosphate cascades [less ▲]

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See detailLocalization of Testosterone-Sensitive and Sexually Dimorphic Aromatase-Immunoreactive Cells in the Quail Preoptic Area
Balthazart, Jacques ULg; Tlemcani, O.; Harada, N.

in Journal of Chemical Neuroanatomy (1996), 11(3), 147-71

The distribution of aromatase-immunoreactive cells was studied in the medial preoptic nucleus of male and female quail that were sexually mature and gonadally intact, or gonadectomized, or gonadectomized ... [more ▼]

The distribution of aromatase-immunoreactive cells was studied in the medial preoptic nucleus of male and female quail that were sexually mature and gonadally intact, or gonadectomized, or gonadectomized and treated with testosterone. The study first confirmed the existence of a significant difference in the number of aromatase-immunoreactive cells between males and females (males > females) and the marked effect of castration and testosterone treatment which, respectively, decrease and restore the number of these cells. An analysis of the distribution in space of this neurochemically defined cell population was also carried out. This study revealed that castration does not uniformly decrease the density of aromatase-immunoreactive cells, but local increases are observed in an area directly adjacent to the third ventricle. A number of new sex differences in the organization of the medial preoptic nucleus and its population of aromatase cells have, in addition, been identified. The density of aromatase-immunoreactive cells is not higher in males than in females throughout the nucleus, but a higher density of immunoreactive cells is present in the ventromedial part of the nucleus in females as compared to males. In addition, the cross-sectional area of the nucleus as defined by the population of aromatase-immunoreactive cells is larger in males than in females in its rostral part and its shape is more elongated in the dorso-ventral direction in females than in males. Some of these differences (e.g. higher density of ARC-ir cells in the ventromedial part of the female POM, shape of the nucleus) appear to be organizational in nature, because they are still present in birds exposed to the same endocrine conditions during adult life (e.g. gonadectomized and treated with a same dose of testosterone). This conclusion should now be tested by experiments manipulating the endocrine environment of quail embryos. The anatomical heterogeneity of the medial preoptic nucleus revealed by this study also suggests a functional heterogeneity and the specific roles of the medial and lateral parts of the nucleus should also be investigated. [less ▲]

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See detailCritical Re-Examination of the Distribution of Aromatase-Immunoreactive Cells in the Quail Forebrain Using Antibodies Raised against Human Placental Aromatase and against the Recombinant Quail, Mouse or Human Enzyme
Foidart, Agnès ULg; Reid, J.; Absil, Philippe ULg et al

in Journal of Chemical Neuroanatomy (1995), 8(4), 267-82

Mouse and quail aromatase cDNAs were isolated from libraries of mouse ovary and quail brain by using a human aromatase cDNA fragment (hA-24) as a probe. These three cDNAs were inserted into plasmid ... [more ▼]

Mouse and quail aromatase cDNAs were isolated from libraries of mouse ovary and quail brain by using a human aromatase cDNA fragment (hA-24) as a probe. These three cDNAs were inserted into plasmid vectors and expressed in Escherichia coli. Antisera against these purified recombinant proteins were raised in rabbit and purified by ammonium sulfate fractionation and affinity chromatography. The three antibodies directed against recombinant human, mouse and quail proteins were used to visualize aromatase-immunoreactive cells in the quail brain. They were compared with the antibody raised against human placental aromatase used in previous experiments and with another antibody recently developed by similar methods. The signal obtained with all antibodies was completely abolished by preadsorption with the homologous recombinant antigens and the signal produced by the two antibodies raised against placental aromatase was similarly abolished by a preadsorption with recombinant quail aromatase. The antibodies raised against recombinant proteins identified the major groups of aromatase cells previously described in the quail brain. The antibodies directed against the mouse and quail antigen identified more positive cells and stained them more densely than the antibodies raised against human recombinant antigen or purified placental aromatase. The new cell groups identified by the antibody raised against quail recombinant aromatase were located in an area ventral to the fasciculus prosencephali lateralis, the nucleus accumbens, the paleostriatum ventrale, the nucleus taeniae, the area around the nucleus ovoidalis, the caudal tuber and the mesencephalic central gray. A critical re-examination of the distribution and nomenclature of the aromatase-positive cells is proposed based on these new findings. [less ▲]

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