Publications by authors named "Kemel M"

Hammada articulata is a plant widely used by the locals of the Algerian Sahara for multiple medicinal purposes. However, little was known about its chemical composition and the mechanisms of its bioactivity. For this purpose, the derived extracts [chloroform (CHCl), ethyl acetate (EtOAc) and n-butanol (n-BuOH)] of the 80% ethanol extract of its aerial parts, were evaluated for their anti-inflammatory, diuretic, and anti-hyperglycemic activities in vivo.

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We report on the experimental observation of a color domain (CD) phenomenon in a dissipative soliton fiber laser. The CDs are constituted by a wavelength-dependent condensed phase of pulses in motion. Single CD, dual CD, and tricolor domain that occupy all the cavity space are observed.

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Background And Purpose: Using an in-house bioinformatics programme, we identified and synthesized a novel nonapeptide, H-Pro-Pro-Thr-Thr-Thr-Lys-Phe-Ala-Ala-OH. Here, we have studied its biological activity, in vitro and in vivo, and have identified its target in the brain.

Experimental Approach: The affinity of the peptide was characterized using purified whole brain and striatal membranes from guinea pigs and rats .

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Since 2007, actions have been undertaken in France to foster mental health research. Our objective was to assess their utility by estimating the evolution of public and non-profit funding for mental health research between 2007 and 2011, both in terms of total funding and the share of health research budgets. Public and non-profit funding was considered.

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Motor stereotypy is a key symptom of various neurological or neuropsychiatric disorders. Neuroleptics or the promising treatment using deep brain stimulation stops stereotypies but the mechanisms underlying their actions are unclear. In rat, motor stereotypies are linked to an imbalance between prefrontal and sensorimotor cortico-basal ganglia circuits.

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Motor stereotypy is a key symptom of various disorders such as Tourette's syndrome and punding. Administration of nicotine or cholinesterase inhibitors is effective in treating some of these symptoms. However, the role of cholinergic transmission in motor stereotypy remains unknown.

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The dysfunction of basal ganglia circuits related to stereotyped motor activity was analysed using the well-established model of cocaine-induced stereotypy in the rat. We examined and compared the neurochemical and electrophysiological effects occurring in medial prefrontal and sensorimotor basal ganglia circuits of the dorsal striatum after cocaine injection in sensitized and non-sensitized rats. Acute injections of cocaine (25 mg/kg), not inducing stereotyped behaviour, affected both medial prefrontal and sensorimotor circuits in a similar way: (i) a mild and delayed increase and decrease of N-methyl-D-aspartate-evoked dopamine and acetylcholine release, respectively and (ii) a marked decrease of cortically evoked inhibition of substantia nigra pars reticulata neurons revealing an imbalance of information transmission between the direct and indirect trans-striatal pathways.

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Three subtypes of vesicular transporters accumulate glutamate into synaptic vesicles to promote its vesicular release. One of the subtypes, VGLUT3, is expressed in neurons, including cholinergic striatal interneurons, that are known to release other classical transmitters. Here we showed that disruption of the Slc17a8 gene (also known as Vglut3) caused an unexpected hypocholinergic striatal phenotype.

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The tachykinin neurokinin 1 receptors (NK(1)Rs) regulation of acetylcholine release and its interaction with the enkephalin/mu opioid receptors (MORs) transmission was investigated in the limbic/prefrontal (PF) territory of the dorsal striatum. Using double immunohistochemistry, we first showed that in this territory, cholinergic interneurons contain tachykinin NK(1)Rs and co-express MORs in the last part of the light period (afternoon). In slices of the striatal limbic/PF territory, following suppression of the dopaminergic inhibitory control of acetylcholine release, application of the tachykinin NK(1)R antagonist, SSR240600, markedly reduced the NMDA-induced acetylcholine release in the morning but not in the afternoon when the enkephalin/MOR regulation is operational.

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Information processing within the striatum is regulated by local circuits involving dopamine, cholinergic interneurons and neuropeptides released by recurrent collaterals of striatal output neurons. In the limbic-prefrontal territory of the dorsal striatum, enkephalin inhibits the NMDA-evoked release of acetylcholine directly through micro-opioid receptors (MORs) located on cholinergic interneurons and indirectly through MORs of output neurons of striosomes. In this territory, we investigated the consequence of changes in dopamine transmission, bilateral 6-hydroxydopamine-induced degeneration of striatal dopaminergic innervation or cocaine (acute and chronic) exposure on (i) MOR expression in both cholinergic interneurons and output neurons of striosomes, and (ii) the direct and indirect enkephalin-MOR regulations of the NMDA-evoked release of acetylcholine.

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Striatal cholinergic interneurons play a crucial role in the control of movement as well as in motivational and learning aspects of behaviour. Neuropeptides regulate striatal cholinergic transmission and particularly activation of mu opioid receptor (MOR) inhibits acetylcholine (ACh) release in the dorsal striatum. In the present study we investigated whether this cholinergic transmission could be modulated by an enkephalin/MOR direct process.

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Several aspects of our 25 year adventure in the field of tachykinins will be successively described. They concern: substance P (SP) synthesis and release in the basal ganglia, the identification and pharmacological characterization of central tachykinin NK(1), NK(2) and NK(3) binding sites and their topographical distribution, the description of some new biological tests for corresponding receptors, the identification of tachykinin NK(1) receptor subtypes or conformers sensitive to all endogenous tachykinins (substance P, neurokinin A (NKA), neurokinin B (NKB), neuropeptide gamma (NP gamma) and neuropeptide K (NPK)) and finally, the functional involvement of these receptors and their subtypes in tachykinin-induced regulations of dopamine and acetylcholine release in the striatum.

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Using an in vitro microsuperfusion procedure, the release of newly synthesized [(3)H]-acetylcholine (ACh), evoked by N-methyl-D-aspartate (NMDA) receptor stimulation, was investigated in striosome-enriched areas and matrix of the rat striatum. The role of micro-opioid receptors, activated by endogenously released enkephalin, on the NMDA-evoked release of ACh was studied using the selective micro-opioid receptor antagonist, beta-funaltrexamine. Experiments were performed 2 (morning) or 8 (afternoon) h after light onset, in either the presence or absence (alpha-methyl-p-tyrosine, an inhibitor of dopamine synthesis) of dopaminergic transmission.

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Article Synopsis
  • Scientists studied how certain brain chemicals work together in rats when a specific part of the brain is blocked from sending signals.
  • They looked at different types of receptors to see which ones help or stop the release of a chemical called ACh when stimulated by NMDA.
  • The results showed that certain blockers (antagonists) could reduce ACh release but could be reversed by specific activators (agonists), suggesting that these activators help improve brain signaling when dopamine is suppressed.
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Using a microsuperfusion method in vitro, the effects of the NK1, NK2, and NK3 tachykinin receptor antagonists SR140333, SR48968, and SR142801, respectively, on the NMDA-evoked release of [3H]-acetylcholine were investigated after both acute and chronic suppression of dopamine transmission in striosomes and matrix of the rat striatum. NMDA (1 mm) alone or with D-serine (10 microm) in the presence of alpha-methyl-p-tyrosine (100 microm) markedly enhanced the release of [3H]-acetylcholine through a dopamine-independent inhibitory process. In both conditions, as well as after chronic 6-OHDA-induced denervation of striatal dopaminergic fibers, SR140333, SR48968, or SR142801 (0.

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The contribution of endogenously released dopamine, GABA and its co-transmitters, substance P (SP) and neurokinin A (NKA), to the control of the evoked release of acetylcholine was investigated in vitro in the striosomes and the matrix of the rat striatum under various modalities of NMDA receptor stimulation (NMDA 50 microM or 1 mM without or with 10 microM D-serine). Sulpiride, bicuculline, SR140333 and SR48968, the antagonists of D(2), GABA A, NK(1) and NK(2) tachykinin receptors, respectively, were used for this purpose. (1) In both striatal compartments, the dopamine-mediated inhibitory regulation of the evoked release of acetylcholine only occurred when D-serine was co-applied with 50 microM or 1 mM NMDA.

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The role of endogenously released arachidonic acid in the control of the NMDA (50 microM)-evoked release of [3H]-acetylcholine previously formed from [3H]-choline was investigated in striosome-enriched areas and in the matrix of the rat striatum using a microsuperfusion procedure in vitro. Experiments were performed with either mepacrine (0.2 microM) or bovine serum albumin (BSA, 0.

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The effects of SR140333 and SR48968 (neurokinin1 and neurokinin2 tachykinin receptor antagonists, respectively) on the N-methyl-D-aspartate-evoked release of [3H]acetylcholine (previously formed from [3H]choline) were investigated in striosome-enriched areas and in the matrix of the rat striatum using an in vitro microsuperfusion method. In both striatal compartments, SR140333 and SR48968 did not modify the 50 microM N-methyl-D-aspartate-evoked release of [3H]acetylcholine. However, in low concentrations, both SR140333 (0.

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The N-methyl-D-aspartate-evoked release of [3H]acetylcholine previously formed from [3H]choline was estimated in striosome- (identified by [3H]naloxone binding) or matrix-enriched areas of the rat striatum using an in vitro microsuperfusion procedure. Experiments were performed in either the absence or the presence of dopaminergic and/or GABAergic receptor antagonists. Although the cell bodies of the cholinergic interneurons were mainly found in the matrix, in the absence of magnesium, N-methyl-D-aspartate (50 microM) stimulated the release of [3H]acetylcholine in both striatal compartments.

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The effects of septide (a short substance P C-terminal analogue) and of the neurokinin-1 receptor agonist [Pro9]substance P on the N-methyl-D-aspartate (50 microM)-evoked release of [3H]dopamine (continuously synthesized from [3H]tyrosine) were investigated in the absence or the presence of the selective neurokinin-1 receptor antagonist RP 67580 in selected striosome- and matrix-enriched areas of the rat striatum. Experiments were performed in vitro using a microsuperfusion procedure described previously. At a concentration of 0.

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The topographical organization of the striatonigral projection was investigated in the cat by comparing the localization and the intensity of labelling of retrogradely labelled cells in the caudate nucleus following one or multiple injections of horseradish peroxidase-wheat germ agglutinin into the center or along the rostrocaudal axis of the substantia nigra pars reticulata. Second, the localizations of retrogradely labelled striatopallidal neurons and of clusters of aggregated striatonigral neurons (as outlined by the transport of 14C-material) were compared in cats that received four horseradish peroxidase-wheat germ agglutinin injections into the internal segment of the globus pallidus and three nigral injections of 14C-amino acids into the substantia nigra pars reticulata. Two types of striatonigral neurons located predominantly within the matrix compartment were identified: poorly collateralized aggregated cells distributed in clusters and more numerous collateralized cells distributed outside the clusters.

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Using a new superfusion procedure in vitro, we have previously reported that the NMDA-evoked release of newly synthesized 3H-dopamine (DA) was higher in matrix- than in striosome-enriched areas of the rat striatum. In addition, GABAergic medium-sized spiny neurons were shown to be indirectly involved in this regulation. Since dynorphin and GABA are colocalized in a population of medium-sized spiny neurons, the role of dynorphin-containing neurons in the NMDA-evoked release of 3H-DA has been investigated using the same superfusion procedure on rat striatal slices.

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The NMDA regulation of the dendritic release of [3H]dopamine ([3H]DA) synthesized from [3H]tyrosine was investigated in vitro using a microsuperfusion procedure in the pars compacta (SNC) and the pars reticulata (SNR) of the cat substantia nigra. The spontaneous release of [3H]DA was threefold higher in the SNC than in the SNR and amphetamine (1 microM) enhanced similarly [3H]DA release in both nigral areas. In the absence of magnesium, NMDA (50 microM) stimulated markedly the release of [3H]DA in the SNC and SNR, these effects being completely prevented by MK 801 (1 microM), the NMDA receptor antagonist.

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In two areas of the rat striatum, the in vitro N-methyl-D-aspartate (NMDA, 50 microM)-evoked release of [3H]dopamine was studied in the presence of bicuculline (5 and 50 microM), an antagonist of GABAA receptors. The responses observed with the higher concentration (50 microM) is compatible with an antagonistic activity of bicuculline on NMDA receptor, as recently reported by Wright and Nowak.

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The visualization of mu opiate receptors by [3H]naloxone binding was used to determine precisely the spatial organization of the patch compartment in the rat striatum and its reproducibility in different animals. Three-dimensional reconstruction of the patch network was made using maps of autoradiographic data obtained from successive coronal, sagittal or horizontal sections. The extreme rostral pole of the striatum (A 11) was characterized by a large patch territory exhibiting complex and tortuous fields with several extensions.

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