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See detailPeripubertal proliferation of progenitor cells in the preoptic area of Japanese quail (Coturnix japonica).
Mouriec, Karen; Balthazart, Jacques ULg

in Brain research (2013), 1516

Brain structures related to reproduction are thought to depend on the action of gonadal steroids acting either during early life (organizing irreversible effects) or adulthood (activating transient ... [more ▼]

Brain structures related to reproduction are thought to depend on the action of gonadal steroids acting either during early life (organizing irreversible effects) or adulthood (activating transient effects). More recently puberty has become a focus of attention and it was demonstrated that action of sex steroid hormones at this time plays a critical role in the final organization of brain and behavior. We studied by BrdU immunohistochemistry the ontogeny from hatching to sexual maturity of a previously identified cell population in the preoptic area labeled by a BrdU injection at the end of embryonic period (E12) of sexual differentiation in male and female Japanese quail. After an initial increase between E12 and hatching, the density of BrdU-immunoreactive cells decreased until the beginning of puberty but then increased again during sexual maturation in the caudal preoptic area specifically. Divisions of these cells took place in the brain parenchyma as indicated by the large numbers of pairs of labeled cells. No sex difference affecting these processes could be detected at any stage of development. Large numbers of new cells thus arise around puberty in the caudal preoptic area and presumably contribute to the reorganization of this structure that precedes the emergence of adult reproductive behaviors. [less ▲]

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See detailConnectivity graph analysis of the auditory resting state network in tinnitus.
MAUDOUX, Audrey ULg; Lefèbvre, Philippe ULg; Cabay, J.-E. et al

in Brain Research (2012), 1485

Thirteen chronic tinnitus patients and fifteen age-matched healthy controls were studied on a 3T magnetic resonance imaging (MRI) scanner during resting condition (i.e. eyes closed, no task performance ... [more ▼]

Thirteen chronic tinnitus patients and fifteen age-matched healthy controls were studied on a 3T magnetic resonance imaging (MRI) scanner during resting condition (i.e. eyes closed, no task performance). The auditory resting-state component was selected using an automatic component selection approach. Functional connectivity (correlations/anti-correlations) in the extracted network was portrayed by integrating the independent component analysis (ICA) approach with a graph theory method. Tinnitus and control groups showed different graph connectivity patterns. In the control group, the connectivity graph was divided into two distinct anti-correlated networks. The first one encompassed the auditory cortices and the insula. The second one encompassed frontoparietal and anterior cingulate cortices, brainstem, amygdala, basal ganglia/nucleus accumbens and parahippocampal regions. In the tinnitus group, only one of the two previously described networks was observed, encompassing the auditory cortices and the insula. Direct group comparison showed, in the tinnitus group, an increased functional connectivity between auditory cortices and the left parahippocampal region surviving multiple comparisons. We investigated a possible correlation between four tinnitus relevant measures (tinnitus handicap inventory (THI) and tinnitus questionnaire (TQ) scores, tinnitus duration and tinnitus intensity during the scanning session) and the connectivity pattern in the tinnitus population. We observed a significant positive correlation between the beta values of the posterior cingulate/precuneus region and the THI score. Our results show a modified functional connectivity pattern in tinnitus sufferers and highlight the role of the parahippocampal region in tinnitus physiopathology. They also point out the importance of the activity and connectivity pattern of the posterior cingulate cortex/precuneus region to the development of the tinnitus associated distress. This article is part of a Special Issue entitled: Tinnitus Neuroscience. [less ▲]

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See detailThe main and accessory olfactory systems of female mice are activated differentially by dominant versus subordinate male urinary odors.
Veyrac, Alexandra; Wang, Guan; Baum, Michael J et al

in Brain Research (2011), 1402

Previous studies have shown that female preferences for male pheromones depend on the female's reproductive condition and the dominance status of the male. However, it is unknown which olfactory system ... [more ▼]

Previous studies have shown that female preferences for male pheromones depend on the female's reproductive condition and the dominance status of the male. However, it is unknown which olfactory system detects the odors that result in a preference for a dominant male. Therefore, in the present study, we asked whether dominant versus subordinate male urinary odors differentially activate the main and accessory olfactory systems in female (C57Bl/6j) mice by monitoring the induction of the immediate early gene, c-fos. A more robust induction of Fos was observed in female mice which had direct nasal contact with dominant male urinary odors in four specific segments of the accessory olfactory system, i.e., the posteroventral part of the medial amygdala, the bed nucleus of the stria terminalis, the medial part of the preoptic nucleus and the ventrolateral part of the ventromedial hypothalamus, compared to females that were exposed to subordinate male urine. This greater activation of the accessory olfactory pathway by dominant male urine suggests that there are differences in the nonvolatile components of dominant versus subordinate male urine that are detected by the vomeronasal organ. By contrast, subordinate male urinary odors induced a greater activation in the piriform cortex which is part of the main olfactory system, suggesting that female mice discriminate between dominant and subordinate male urine using their main olfactory system as well. [less ▲]

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See detailHere I am: the cortical correlates of visual self-recognition.
Devue, Christel ULg; Collette, Fabienne ULg; Balteau, Evelyne ULg et al

in Brain Research (2007), 1143

Recently, interest in the neural correlates of self-recognition has grown. Most studies concentrate on self-face recognition. However, there is a lack of convergence as to precise neuroanatomical ... [more ▼]

Recently, interest in the neural correlates of self-recognition has grown. Most studies concentrate on self-face recognition. However, there is a lack of convergence as to precise neuroanatomical locations underlying self-face recognition. In addition, recognition of familiar persons from bodies has been relatively neglected. In the present study, cerebral activity while participants performed a task in which they had to indicate the real appearance of themselves and of a gender-matched close colleague among intact and altered pictures of faces and bodies was measured. The right frontal cortex and the insula were found to be the main regions specifically implicated in visual self-recognition compared with visual processing of other highly familiar persons. Moreover, the right anterior insula along with the right anterior cingulate seemed to play a role in the integration of information about oneself independently of the stimulus domain. The processing of self-related pictures was also compared to scrambled versions of these pictures. Results showed that different areas of the occipito-temporal cortex were more or less recruited depending on whether a face or a body was perceived, as it has already been reported by several recent studies. The implication of present findings for a general framework of person identification is discussed. [less ▲]

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See detailPlatelet adhesion receptors do not modulate infarct volume after a photochemically induced stroke in mice.
Frederix, Kim ULg; Chauhan, Anil K; Kisucka, Janka et al

in Brain Research (2007), 1185

Photochemically induced cerebral infarction has been considered a clinically relevant model for ischemic stroke. We evaluated various transgenic mice to study the role of platelet adhesion molecules in ... [more ▼]

Photochemically induced cerebral infarction has been considered a clinically relevant model for ischemic stroke. We evaluated various transgenic mice to study the role of platelet adhesion molecules in this model. Infarction to the sensorimotoric cortex was induced by erythrosin B and laser light. Infarct volumes were calculated from triphenyltetrazolium chloride stained brain slices. Thrombus formation and vessel leakage were observed in vivo by multiphoton microscopy. Mice mutant in VWF, GPIbalpha, beta3 integrin, and P-selectin did not show any significant differences in infarct volume compared to wild type (WT). This is in contrast to the intraluminal middle cerebral artery occlusion model in which alphaIIbbeta3 integrin, GPIbalpha, and P-selectin are known to modulate infarct size. Multiphoton microscopy showed that small, non-occlusive embolizing platelet thrombi formed in the photochemically injured brains. Massive vessel leakage was observed within 25 min of laser injury. Interestingly, we observed a significant increase in infarct size with aging, accordant with heightened fragility of the blood brain barrier (BBB) in older mice. This model of photochemically induced stroke is closer to a BBB injury model than a thrombotic stroke model in which platelets and their adhesion molecules are crucial. This model will be useful to study mechanisms regulating BBB permeability. [less ▲]

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

in Brain Research (2006), 1126

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

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

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See detailImplicit oculomotor sequence learning in humans: Time course of offline processing
Albouy, Geneviève ULg; Ruby, P.; Phillips, Christophe ULg et al

in Brain Research (2006), 1090

Studies of manual and digital sequence learning indicate that motor memories continue to be processed after training has ended, following a succession of identifiable steps. However, it is not known ... [more ▼]

Studies of manual and digital sequence learning indicate that motor memories continue to be processed after training has ended, following a succession of identifiable steps. However, it is not known whether this offline memory processing constitutes a basic feature of motor learning and generalizes to the implicit learning of a sequence of eye movements. To assess this hypothesis, we have created the serial oculomotor reaction time task (SORT). Participants were trained to the SORT then tested after either 30 min, 5 h or 24 h. During training, ocular reaction times decreased monotonically over practice of a repeated sequence, then increased when a different sequence was displayed, demonstrating oculomotor learning of the trained sequence. When tested 30 min after training, a significant gain in oculomotor performance was observed irrespective of the sequence learning. This gain was no longer present after 5 h. Remarkably, a gain in performance specific to the learned sequence emerged only 24 h after training. After testing, a generation task confirmed that most subjects learned implicitly the regularities of the sequence. Our results show that, as for manual or digital sequences, oculomotor sequences can be implicitly learned. The offline processing of oculomotor memories follows distinct stages in a way similar to those observed after manual or digital sequence learning. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailPost-ischemic hypothermia reduced IL-18 expression and suppressed microglial activation in the immature brain.
Fukui, On; Kinugasa, Yukiko; Fukuda, Aya et al

in Brain Research (2006), 1121(1), 35-45

Inflammation is an important factor for hypoxia-ischemia (HI) brain injury. Interleukin (IL)-18 is a proinflammatory cytokine which may be a contributor to injury in the immature brain after HI. To ... [more ▼]

Inflammation is an important factor for hypoxia-ischemia (HI) brain injury. Interleukin (IL)-18 is a proinflammatory cytokine which may be a contributor to injury in the immature brain after HI. To investigate the effects of post-HI hypothermia on IL-18 in the developing brain, 7-day-old rats were subjected to left carotid artery ligation followed by 8% oxygen for 60 min and divided into a hypothermia group (rectal temperature 32 degrees C for 24 h) and a normothermia group (36 degrees C for 24 h). The IL-18 mRNA was analyzed with real-time RT-PCR, and the protein level was analyzed by Western blot, and the location and source of IL-18 were assessed by immunohistochemistry. The significant increase of the IL-18 mRNA was observed in the ipsilateral hemispheres of the normothermia group at 24 h and 72 h after HI compared with controls, but the level in the ipsilateral hemispheres of the hypothermia group was significantly reduced at both time points, compared with the normothermia group, respectively. The IL-18 protein level in the ipsilateral hemispheres of the normothermia group significantly increased at 72 h after HI compared with controls, however, the protein level of the hypothermia group was significantly decreased, compared with the normothermia group. IL-18-positive cells were observed throughout the entire cortex, corpus callosum (CC) and striatum in the ipsilateral hemispheres of normothermia group at 72 h after HI, however, little positive cells were observed in the hypothermia group. Double labeling immunostaining found that most of the IL-18-positive cells were colocalized with lectin, which is a marker of microglia. The number of ameboid microglia (AM) in the normothermia group was significantly increased in cortex and CC, compared with the number in controls, but there were very few ramified microglia (RM) in these areas. In contrast, the number of AM in the hypothermia group was significantly decreased in cortex and CC, compared with the number in the normothermia group, and there were no significant differences in the number of AM and RM between the hypothermia group and controls. In conclusion, we found that IL-18 mRNA and the protein level were attenuated by post-HI hypothermia and that post-HI hypothermia may decrease microglia activation in the developing brain. [less ▲]

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See detailSex differences in the distribution of the steroid receptor coactivator SRC-1 in the song control nuclei of male and female canaries
Charlier, Thierry ULg; Balthazart, Jacques ULg; Ball, Gregory F

in Brain Research (2003), 959(2), 263-274

The steroid receptor coactivator SRC-1 modulates ligand-dependent transactivation of several nuclear receptors, including the receptors for sex steroid hormones. The distribution of SRC-1 transcripts was ... [more ▼]

The steroid receptor coactivator SRC-1 modulates ligand-dependent transactivation of several nuclear receptors, including the receptors for sex steroid hormones. The distribution of SRC-1 transcripts was analyzed here by in situ hybridization in coronal sections through the brain of male and female canaries. A broad but heterogeneous distribution of SRC-1 transcripts was observed with high numbers of densely labeled cells being present in many steroid-sensitive areas including the medial preoptic nucleus, several hypothalamic nuclei, five song control nuclei (HVc, the lateral and medial portion of the magnocellular nucleus of the anterior neostriatum, area X and the nucleus uvaeformis) and several catecholaminergic areas (area ventralis of Tsai, substantia nigra, locus coeruleus). The volume of two song control nuclei, HVc and area X were reconstructed based on the boundaries of the cell groups exhibiting a denser SRC-1 expression as compared to the surrounding areas. Sex differences in the expression of SRC-1 were also detected in several song control nuclei. In particular, the volume of HVc based on the high density of SRC-1 expression was significantly larger in males than in females. The effect of steroids on the song control system could be, at least in part, indirect and result from a modulation by steroids of the catecholaminergic inputs to the song control nuclei. The presence of the steroid receptor coactivator SRC-1 in the telencephalic song control nuclei and in the catecholaminergic cell groups that innervate the song system supports the idea that SRC-1 expression could play an active role in the control of singing behavior by modulating estrogen and androgen receptor action at both locations. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detail5-HT2A receptor antagonism potentiates haloperidol-induced dopamine release in rat medial prefrontal cortex and inhibits that in the nucleus accumbens in a dose-dependent manner
Liégeois, Jean-François ULg; Ichikawa, J.; Meltzer, H. Y.

in Brain Research (2002), 947(2), 157-165

Combined serotonin (5-HT)(2A) and dopamine (DA) D-2 blockade has been shown to contribute to the ability of atypical antipsychotic drugs (APDs) to increase DA release in rat medial prefrontal cortex (mPFC ... [more ▼]

Combined serotonin (5-HT)(2A) and dopamine (DA) D-2 blockade has been shown to contribute to the ability of atypical antipsychotic drugs (APDs) to increase DA release in rat medial prefrontal cortex (mPFC). We provide additional support for this hypothesis by examining the effect of the selective 5-HT2A antagonist M100907 plus haloperidol, a potent D, antagonist APD, on DA release in the mPFC and nucleus accumbens (NAC). Haloperidol (0.01-1.0 mg/kg) produced an inverted U-shaped increase in DA release in the mPFC, with a significant increase only at 0.1 mg/kg. Haloperidol (0.1 and 1.0 mg/kg) significantly increased DA release in the NAC. M100907 (0.1 mg/kg) by itself had no effect on DA release in either region. This dose of M100907 potentiated the ability of low (0.01-0.1 mg/kg), but not high dose (0.3-1.0 mg/kg) haloperidol to increase mPFC DA release, whereas it abolished the effect of both 0.1 and 1.0 mg/ka haloperidol on NAC DA release. These results suggest that the relatively higher ratio of 5-HT2A to D-2 antagonism may contribute to the potentiation of haloperidol-induced mPFC DA release, whereas 5-HT2A antagonism can diminish haloperidol-induced NAC DA release, even when combined with extensive D, antagonism, which may not be synergistic with 5-HT2A antagonism in the mPFC. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailTaurine increases in the nucleus accumbens microdialysate after acute ethanol administration to naive and chronically alcoholised rats
Dahchour, Abdelkhader; Quertemont, Etienne ULg; De Witte, Philippe

in Brain Research (1996), 735

The extracellular changes of amino acids glutamate, taurine and GABA in the nucleus accumbens of freely moving rats were estimated using the microdialysis technique following acute and chronic ethanol ... [more ▼]

The extracellular changes of amino acids glutamate, taurine and GABA in the nucleus accumbens of freely moving rats were estimated using the microdialysis technique following acute and chronic ethanol injections (1, 2, and 3 g/kg body weight). Compared to baseline values, taurine increased by 154%, 142% and 162%, 20 min after the acute injection of, respectively, 1, 2 and 3 g/kg body weight ethanol, while 40 min after ethanol injection, taurine had increased by 124%, 146% and 168%. No changes in either glutamate or GABA were detected at any time points assayed. In the rats which had received chronic ethanol administration prior to a further acute ethanol injection (1, 2, and 3 g/kg body weight), taurine increased by 138%, 144% and 180%, 20 min after the ethanol injection, and at 40 min post ethanol injection taurine had increased by 134%, 160% and 158%, compared to the basal baseline value. No significant changes were observed in either glutamate or GABA microdialysate content in these chronic studies. The biological role played by taurine after acute ethanol injection in the nucleus accumbens remains unclear but may be associated with a yet, undefined mechanism, in reducing the cytotoxicity of ethanol. [less ▲]

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See detailAlpha-MSH stimulates neurite outgrowth of neonatal rat corticospinal neurons in vitro.
Joosten, E. A.; Verhaagh, S.; Martin, Didier ULg et al

in Brain Research (1996), 736(1-2), 91-8

Peptides related to melanocortin (alpha MSH) and corticotropin (ACTH), collectively termed melanocortins, exert trophic effects on the outgrowth of neurites from peripheral and central nervous system in ... [more ▼]

Peptides related to melanocortin (alpha MSH) and corticotropin (ACTH), collectively termed melanocortins, exert trophic effects on the outgrowth of neurites from peripheral and central nervous system in vitro. Here we study the neurite outgrowth promoting effect of alpha-MSH on corticospinal (CS) neurons in vitro. Corticospinal neurons were identified in cell culture of neonatal rat cortex by immunostaining of cholera toxin subunit B (CTB), retrogradely transported from the cervical parts of the spinal cord. The CTB-immunoreactive neurons represent a small percentage (3-5%) of the total cell population after 72 h in vitro. The axons or dendrites of cortical and CTB-labelled layer V neurons were visualized using antibodies against axon- or dendrite-specific markers and measured using a semi-automatic quantification device. Here we report that alpha-MSH stimulates axonal as well as dendrite outgrowth from both total and CTB-labelled neurons with a bell-shape response curve. Axonal outgrowth of CTB-labelled neurons was dose-dependently stimulated with a maximal effect of 50% at 10(-10) M alpha-MSH. The maximal effect for stimulation of axon outgrowth for the total cortex population was observed at 10(-8) M alpha-MSH. In addition dendrite outgrowth of both total and CTB-labelled neurons is stimulated in a dose-dependent manner with maximal effects (varying between 46 and 48%) at 10(-8) M alpha-MSH. Explanations in the shift for the optimal alpha-MSH concentration for stimulation of axonal outgrowth of CTB-labelled layer V neurons as compared to total cortex neurons are discussed. [less ▲]

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See detailPre- and Post-Translational Regulation of Aromatase by Steroidal and Non-Steroidal Aromatase Inhibitors
Foidart, Agnès ULg; Tlemcani, O.; Harada, N. et al

in Brain Research (1995), 701(1-2), 267-78

Treatment of castrated quail with testosterone (T) reliably activates male copulatory behavior and, at the same time, increases the aromatase activity (AA), the number of aromatase-immunoreactive (ARO-ir ... [more ▼]

Treatment of castrated quail with testosterone (T) reliably activates male copulatory behavior and, at the same time, increases the aromatase activity (AA), the number of aromatase-immunoreactive (ARO-ir) cells and the concentration of aromatase mRNA as measured by RT-PCR in the brain. All these effects can be mimicked by estrogens. The behavioral effects of T can be blocked by a variety of aromatase inhibitors and, in parallel, the AA is strongly inhibited in the preoptic area (POA). We showed recently that the steroidal inhibitor, 4-OH-androstenedione (OHA) markedly decreases the immunostaining density of brain ARO-ir cells while the non-steroidal inhibitor, R76713 (racemic Vorozole; VOR) unexpectedly increased the density of this staining, despite the fact that the enzyme activity was completely inhibited. To generalize these findings and try to identify the underlying mechanism, we compared here the effects of two steroidal (OHA and androstatrienedione [ATD]) and two non-steroidal (VOR and Fadrozole [FAD]) aromatase inhibitors on the aromatase immunostaining and aromatase mRNA concentration in the brain of castrated quail concurrently treated with T. The 4 inhibitors significantly blocked the activation by T of male copulation. The two steroidal inhibitors decreased the immunostaining of brain ARO-ir cells but both VOR and FAD markedly enhanced the density of this staining. In parallel, OHA and ATD completely blocked the T-induced increase in aromatase mRNA concentration, while VOR and FAD had no effect on these RNA concentrations in the POA-anterior hypothalamus and they decreased them only slightly in the posterior hypothalamus. Taken together these results suggest that the inhibition of AA by ATD or OHA and the subsequent removal of locally produced estrogens blocks the synthesis of aromatase presumably at the transcriptional level. By contrast, the two non-steroidal inhibitors tested here block AA but in parallel increase the aromatase immunostaining. This effect does not result from an enhanced transcription and it is therefore speculated that these compounds increase either the translation of the aromatase mRNA or the half-life of the protein itself. [less ▲]

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See detailHydrogen Peroxide Hyperpolarizes Rat Ca1 Pyramidal Neurons by Inducing an Increase in Potassium Conductance
Seutin, Vincent ULg; Scuvée-Moreau, Jacqueline ULg; Massotte, Laurent ULg et al

in Brain Research (1995), 683(2), 275-8

It has been suggested that hydrogen peroxide is involved in cascades of pathological events affecting neural cells. The aim of this study was therefore to examine whether this molecule is able by itself ... [more ▼]

It has been suggested that hydrogen peroxide is involved in cascades of pathological events affecting neural cells. The aim of this study was therefore to examine whether this molecule is able by itself to modify membrane properties of pyramidal neurons in the CA1 region of the rat hippocampus. Intracellular recordings in the slice preparation showed that 3.3 mM hydrogen peroxide hyperpolarized all neurons tested (n = 41) by 11 +/- 3 mV. This effect persisted in the presence of tetrodotoxin. It developed slowly, was reversible and reproducible. In the presence of tetrodotoxin, the extrapolated reversal potential of this effect was -95 +/- 5 mV in 2.5 mM external potassium. This value was not significantly different from the one obtained with the GABAB agonist baclofen (10 microM) (-98 +/- 5 mV). It shifted when the concentration of external potassium was increased to 10.5 mM (from -96 +/- 5 to -62 +/- 4 mV), in close agreement with the Nernst equation potassium ions. The hyperpolarization was significantly reduced (by 65 +/- 22%) by the potassium channel blocker barium (100 microM). We suggest that hydrogen peroxide is able to induce an increase in potassium conductance in rat CA1 pyramidal neurons. The exact mechanism by which it produces this effect (direct action on channels or indirect effect) remains to be determined. [less ▲]

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See detailEffects of Steroidal and Non Steroidal Aromatase Inhibitors on Sexual Behavior and Aromatase-Immunoreactive Cells and Fibers in the Quail Brain
Foidart, Agnès ULg; Harada, N.; Balthazart, Jacques ULg

in Brain Research (1994), 657(1-2), 105-23

Castrated quail were treated with Silastic implants filled with testosterone (T) in association with injections of the aromatase inhibitors, R76713 (racemic vorozole; 1 mg/kg twice a day) or 4 ... [more ▼]

Castrated quail were treated with Silastic implants filled with testosterone (T) in association with injections of the aromatase inhibitors, R76713 (racemic vorozole; 1 mg/kg twice a day) or 4-hydroxyandrostenedione (OHA; 5 mg/bird twice a day). [less ▲]

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See detailModulation of Temporalis Muscle Exteroceptive Suppression by Limb Stimuli in Normal Man
Schoenen, Jean ULg; Wang, W.; Gérard, P.

in Brain Research (1994), 657(1-2), 214-20

The effects of noxious and non-noxious limb stimulations on the second exteroceptive suppression of voluntary temporalis muscle activity (ES2) were studied in healthy human volunteers. Duration of ... [more ▼]

The effects of noxious and non-noxious limb stimulations on the second exteroceptive suppression of voluntary temporalis muscle activity (ES2) were studied in healthy human volunteers. Duration of temporalis ES2 was measured on averaged rectified responses obtained after stimulating the labial commissure at an intensity of 25 mA. Single peripheral electrical stimuli applied over nerve trunks or over the skin before the labial stimulus decreased ES2 duration. This effect was most pronounced after cutaneous stimuli, especially of the index finger, and it was not observed when the conditioning stimulus was a 10 second, high frequency train. For stimulation at the index finger, temporalis ES2 inhibition progressively increased with intensity from 10 mA to 40 mA; it was maximal for an interstimulus interval between 50 and 140 ms. After naloxone (0.4 mg or 4 mg, i.v.) there was a partial reversal of the index-induced ES2 depression, but this effect was not significant. Immersion of one hand in water heated at 47 degrees C produced a short-lasting ES2 reduction. These results are comparable, though not similar, to the inhibition of the digastric reflex (or jaw opening reflex) observed in animals after limb stimuli and to the depression of the spinal flexion reflex reported in man after heterotopic peripheral stimuli. Although peripheral stimuli were able by themselves to suppress temporalis EMG activity in some subjects, it is likely that they reduce labial-induced ES2 via activation of brainstem structures, such as periaqueductal gray matter or raphe magnus nucleus, which are thought to inhibit the medullary inhibitory interneurons mediating ES2. [less ▲]

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See detailChloride Permeability of Rat Brain Membrane Vesicles Correlates with Thiamine Triphosphate Content
Bettendorff, Lucien ULg; Hennuy, Benoît ULg; De Clerck, Anne et al

in Brain Research (1994), 652(1), 157-160

Incubation of rat brain homogenates with thiamine or thiamine diphosphate (TDP) leads to a synthesis of thiamine triphosphate (TTP). In membrane vesicles subsequently prepared from the homogenates ... [more ▼]

Incubation of rat brain homogenates with thiamine or thiamine diphosphate (TDP) leads to a synthesis of thiamine triphosphate (TTP). In membrane vesicles subsequently prepared from the homogenates, increased TTP content correlates with increased 36Cl- uptake. A hyperbolic relationship was obtained with a K0.5 of 0.27 nmol TTP/mg protein. In crude mitochondrial fractions from the brains of animals previously treated with thiamine or sulbutiamine, a positive correlation between 36Cl- uptake and TTP content was found. These results, together with other results previously obtained with the patch-clamp technique, suggest that TTP is an activator of chloride channels having a large unit conductance. [less ▲]

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See detailApamin increases NMDA-induced burst-firing of rat mesencephalic dopamine neurons.
Seutin, Vincent ULg; Johnson, S. W.; North, R. A.

in Brain Research (1993), 630(1-2), 341-4

Intracellular recordings made in vitro from rat midbrain dopamine neurons showed that apamin (100 nM) did not alter the regular spontaneous firing of the neurons, but it increased the occurrence of bursts ... [more ▼]

Intracellular recordings made in vitro from rat midbrain dopamine neurons showed that apamin (100 nM) did not alter the regular spontaneous firing of the neurons, but it increased the occurrence of bursts of action potentials in N-methyl-D-aspartate. Apamin appeared to facilitate burst-firing induced by NMDA because, by blocking an outward calcium-activated potassium current, it increased the depolarizing action of NMDA. [less ▲]

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See detailNeuroanatomical Specificity in the Autoregulation of Aromatase-Immunoreactive Neurons by Androgens and Estrogens: An Immunocytochemical Study
Balthazart, Jacques ULg; Foidart, Agnès ULg; Surlemont, C. et al

in Brain Research (1992), 574(1-2), 280-90

Testosterone (T) increases brain aromatase activity (AA) in quail and other avian and mammalian species. It was shown both in quail and in rat that this enzymatic induction results from a synergistic ... [more ▼]

Testosterone (T) increases brain aromatase activity (AA) in quail and other avian and mammalian species. It was shown both in quail and in rat that this enzymatic induction results from a synergistic action of androgens and estrogens. These studies provide little information on possible anatomical or cellular specificity of the effect. Using a polyclonal antiserum against human placental aromatase, we have previously identified aromatase-immunoreactive (ARO-ir) neurons in the quail brain and demonstrated that T increases the number of ARO-ir cells in the quail preoptic area (POA) supporting previous evidence that T increases AA in the brain. However, which T metabolites are involved, the actual mechanism of regulation and the possibility of anatomical specificity for these effects are not yet clear. In the present study, we disassociated the effects of androgens and estrogens in aromatase induction by comparing ARO-ir neurons of quail treated with T alone or T in the presence of a potent aromatase inhibitor (R76713), which has been shown to depress AA levels and to suppress T-activated copulatory behavior. T increased the number of ARO-ir cells in POA, bed nucleus striae terminalis (BNST) and tuberal hypothalamus (Tu). The T effect was inhibited by concurrent treatment with aromatase inhibitor in Tu, but not in POA and BNST. This differential effect of the aromatase inhibitor fits in very well with our previous studies of the co-localization of aromatase and estrogen receptors. The T effect was blocked by R76713 in areas where ARO-ir and estrogen receptor-ir are generally co-localized (Tu) and was not affected in areas with mainly ARO-ir positive, estrogen receptor-ir negative cells (POA, BNST). This suggests anatomical differences in the expression or clearance of aromatase which may be differentially sensitive to androgens and estrogens and dependent upon the presence of sex steroid receptors. [less ▲]

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