14 research outputs found

    Changes in striatal neuropeptides and GAD67 expression following a minimal cortical lesion.

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    We have analyzed the effects of a small cortical infarct which is known to induce dramatic changes in gene expression in the entire cerebral cortex, on the gene expression in the striatum, a target structure of cortical neurons. Striatal glutamic acid decarboxylase (GAD67) and enkephalin expressions were increased in the striatum ipsilateral to the lesion. Conversely, neuropeptide Y- and somatostatin-like immunoreactivity were decreased in the ipsilateral striatum and this decrease was only related to a decrease in the labeling of processes with no changes in the number of labeled neurons. A minimal cortical lesion may therefore induce changes in gene expression in a subcortical structure through hyperactivity of glutamatergic synaptic inputs. One should therefore remember these extensive and long-lasting effects when surgical manipulations are performed on rat brain for stereotaxic surgery and placement of electrodes or probes.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

    GTP-cyclohydrolase-I like immunoreactivity in rat brain

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    GTPCH-I immunoreactive structures in the rat brain were studied using a polyclonal antibody raised in the chick. General mapping was made using the avidin-biotin-peroxidase technique and compared with the distribution of tyrosine hydroxylase and serotonin immunoreactivities. Double immunofluorescence was performed in order to establish real intracellular colocalization. GTPCH-I immunoreactivity was generally found to be low. Immunostained neurons were present in all the serotonin cell groups. In catecholaminergic neurons, although tyrosine hydroxylase immunoreactivity was always very high, GTPCH-I immunoreactivity was extremely variable, from relatively strong (substantia nigra, ventral tegmental area) to low (locus coeruleus, caudal part of the hypothalamus), extremely low (rostral hypothalamus, ventral brainstem) or almost absent (dorsal brainstem, some hypothalamic nuclei). When feasible, double immunolabeling revealed that all the serotonin cells and most of the tyrosine hydroxylase cells were also expressing GTPCH-I. Our results argue in favor of a regulation of tyrosine hydroxylase activity by the intracellular synthesis of BH4.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

    Regulation of nociceptin mRNA expression in the septum by dopamine and adenosine systems.

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    Most effects of nociceptin are related to blockade of stress and anxiolytic-like effects. This neuropeptide is highly expressed in septal nuclei, which are involved in response to stressful situations. Dopamine and adenosine may have modulatory effects on stress behaviour by acting on septal neurons. We therefore analysed the regulation of septal nociceptin expression using quantitative in situ hybridization following manipulations of adenosine and dopamine neurotransmission. No difference was observed between wild-type and A2A receptor-deficient mice. In both genotypes, chronic treatments with caffeine, an equipotent A1 and A2A adenosine receptor antagonist, did not significantly modify nociceptin expression. 6-Hydroxydopamine-induced dopamine depletion was also without effect. These results demonstrate that dopamine and adenosine are not involved in the regulation of septal nociceptin expression in spite of the involvement of these three neurotransmitters in stress and anxiety behaviours.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

    Distribution of SV2C mRNA and protein expression in the mouse brain with a particular emphasis on the basal ganglia system.

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    Synaptic vesicle 2 proteins (SV2), SV2A, SV2B and SV2C, are integral proteins localized on the surface of synaptic vesicles in all neurons. SV2 proteins appear to play an important, but not yet fully understood role in synaptic vesicle exocytosis and neurotransmitter release. Moreover, SV2 seems to be the receptor of the botulinum neurotoxin A. In the present study, using single and double-labeling fluorescent immunohistochemistry and in situ hybridization we have identified the brain pattern of SV2C mRNA and protein expression in mice. Our results indicated that SV2C protein was expressed in a small subset of brain regions including the olfactory bulb, olfactory tubercle, nucleus accumbens, caudate-putamen, ventral pallidum, globus pallidus, substantia nigra and the ventral tegmental area. These results were confirmed by means of in situ hybridization, except for the globus pallidus and the substantia nigra pars reticulata, in which no labeling was found, suggesting that SV2C-positive fibers in these areas are terminals of striatal projecting neurons. In the striatum, we found that, in addition to its presence in the projection neurons, SV2C was densely expressed in a fraction (around 45%) of cholinergic interneurons. In addition, our data also showed that SV2C was densely expressed in most dopaminergic neurons in the substantia nigra pars compacta and the ventral tegmental area (more than 70% of the dopaminergic neurons analyzed were SV2C-positive). Altogether, our results suggest that SV2C may contribute to the regulation of neurotransmitter release and synaptic transmission in the basal ganglia including cholinergic striatal interneurons and nigro-striatal/mesolimbic dopamine neurons.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

    Caffeine-mediated induction of c-fos, zif-268 and arc expression through A1 receptors in the striatum: different interactions with the dopaminergic system.

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    Adenosine and the adenosine receptor antagonist, caffeine, modulate locomotor activity and striatal neuropeptide expression through interactions with the dopaminergic system by mechanisms which remain partially undetermined. We addressed this question by using quantitative immunocytochemistry and in situ hybridization, combined with retrograde tracing of striatal neurons, to characterize the mechanism(s) leading to the striatal increase in the immediate early genes (IEG), c-fos, zif-268 and arc, following a single injection of caffeine or the A1 antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). Caffeine and DPCPX induced c-fos, zif-268 and arc expression, both at mRNA and protein levels, in large proportions of striatonigral and striatopallidal neurons. The involvement of dopamine systems was evaluated by manipulations of the dopaminergic transmission. Quinpirole, a D2 agonist, almost completely blocked the caffeine-induced IEG increase in both striatopallidal and striatonigral neurons. Conversely, the lesion of the nigrostriatal pathway and the D1 antagonist SCH23390 abolished the caffeine effects in striatonigral neurons but had no or slight effect, respectively, on its action in striatopallidal neurons. These observations demonstrate that caffeine- and DPCPX-mediated IEG inductions involved different mechanisms in striatonigral and striatopallidal neurons through blockade of A1 receptors. Immediate early gene inductions result from a stimulation of dopamine release in striatonigral neurons and from activation of glutamate release and probably also acetylcholine release in striatopallidal neurons. These results also support the idea that, besides A2A receptors, adenosine acting at the A1 receptor plays pivotal functions in the basal ganglia physiology and that blockade of these receptors by specific or nonspecific antagonists, DPCPX and caffeine, may influence a broad range of neuronal functions in the striatum.Journal ArticleResearch Support, Non-U.S. Gov'tFLWINinfo:eu-repo/semantics/publishe

    A2A receptor and striatal cellular functions: regulation of gene expression, currents, and synaptic transmission.

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    A2A receptor is highly coexpressed with enkephalin and D2 receptor in striatopallidal neurons. A2A antagonists acutely enhance motor behavior in animal models of Parkinson's disease (PD) and are therefore considered potential PD therapeutic agents. Analysis of gene expression regulation using pharmacologic tools or A2A receptor-deficient mice (A2A-/-) shows that the A2A receptor positively and tonically controls the expression of enkephalin and immediate early genes in striatopallidal neurons. Because this regulation strictly mirrors the effect of D2 receptor, these data strongly support the hypothesis that A2A antagonists reduce the activity of striatopallidal neurons in models of PD. However, analysis of A2A-/- mice suggests additional effects of A2A receptor in the control of striatal physiology. Unexpectedly, these animals exhibited a reduction in exploratory activity and a 50% reduction in substance P expression. This was associated with a 45% decrease in the striatal extracellular dopamine concentration, suggesting that chronic absence of A2A receptor results in a functional hypodopaminergic state in the striatum. The A2A receptor controls inhibitory synaptic transmission negatively in the striatum and positively in the globus pallidus; this further supports the efficacy of A2A antagonists in reducing the activity of striatopallidal neurons in PD. The A2A receptor does not modulate basal alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA)-mediated excitatory corticoaccumbal synaptic transmission during normal physiologic conditions. However, genetic inactivation or pharmacologic blockade of the A2A receptor significantly reduced long-term potentiation (LTP) at this synapse. Therefore, this receptor is implicated in the induction of corticoaccumbal LTP, an effect that could be related to its involvement in long-term behavioral sensitization to repeated dopaminergic treatment.Journal ArticleResearch Support, Non-U.S. Gov'tReviewinfo:eu-repo/semantics/publishe

    Differential expression of calbindin and calmodulin in motoneurons after hypoglossal axotomy.

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    Axotomy induces a profound modification of Ca2+ homeostasis in injured neurons which may lead to neuronal death. Remarkably, after axotomy and resection of the hypoglossal nerve, 65-75% of the hypoglossal motoneurons survive in the long term and this suggests some adaptive mechanisms compensating the massive calcium influx. As potential components of this adaptation, we have examined calmodulin and calbindin-D28k by in situ hybridisation and immunohistochemistry in motoneurons of the rat after hypoglossal nerve transection. Neuronal calbindin mRNA and protein content was low in normal state, transiently increased to 200% of the basal expression at 8 days post-operation (dpo), then declined to normal again until 28 dpo. Calmodulin mRNA was highly expressed in normal hypoglossal motoneurons and remained constant after axotomy. Calmodulin protein immunoreactivity, however, was transiently decreased in axotomised motoneurons suggesting post-transcriptional modification. The upregulation of calbindin expression may facilitate the survival of injured motoneurons.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

    Axotomy induces transient calbindin D28K immunoreactivity in hypoglossal motoneurons in vivo.

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    Calbindin D28K, an intracellular calcium-binding protein, acts as Ca2+ buffering system in the cytoplasm. By means of this property, calbindin may protect neurons against large fluctuations in free intracellular Ca2+ and, hence, may prevent cell death. Although axotomy causes a massive influx of calcium into the lesioned neurons, resection of the hypoglossal nerve does not induce extensive neuronal cell death in rats. Even several weeks after axotomy, about 70% of the motoneurons survive despite permanent target deprivation. The mechanisms responsible for this remarkable survival rate are unknown. In this study, we have looked at the modification of calbindin immunoreactivity in axotomized hypoglossal motoneurons. In non-axotomized motoneurons, no calbindin is detectable by immunocytochemistry. Axotomy induced an increase of calbindin immunoreactivity in lesioned motoneurons. This increase, visualised by the number of calbindin-immunoreactive neurons extended from 1 day to 28 days. At this time most, but not all, motoneurons located on the side of the lesion were calbindin-positive as shown by retrograde labeling and immunoquenching. From 14 days post operation, calbindin immunoreactivity decreased and reached its basal value after 35 days post operation. At that time, only fibres were still calbindin immunoreactive. Interestingly, calbindin-immunoreactivity was also increased in almost all cell nuclei, compatible with a nuclear regulation. These data are consistent with the hypothesis that, as a reaction to axotomy, motoneurons trigger an increase in calbindin expression which acts as a compensatory Ca(2+)-buffering system, enabling neurons to maintain Ca2+ homeostasis and the survival of many motoneurons after axotomy.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe
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