The Experts below are selected from a list of 153 Experts worldwide ranked by ideXlab platform
Guy Chouvet - One of the best experts on this subject based on the ideXlab platform.
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Regulation of substantia nigra pars reticulata neuronal activity by excitatory amino acids.
Naunyn-Schmiedeberg's archives of pharmacology, 1999Co-Authors: Patricia Schmitt, Fabienne Soulière, C. Dugast, Guy ChouvetAbstract:Midbrain non-dopaminergic neurons of the substantia nigra pars reticulata play an important role in the basal ganglia circuitry. The regulation of their electrical activity by excitatory amino acid (EAA) inputs was investigated using in vivo electrophysiological methods in chloral hydrate-anaesthetized rats. We first determined the subtypes of EAA Receptors present on reticulata neurons, using microiontophoretic application of selective agonists: kainic acid (KA), (±)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N-methyl-d-aspartic acid (NMDA), and trans-(±)-1-amino-1,3-cyclopentanedicarboxylic acid (trans-ACPD). Each agonist activated reticulata neurons and the apparent rank order of efficacy was: KA≥AMPA=NMDA>trans-ACPD. Using pressure or iontophoretic microejections of ionotropic and Metabotropic Receptor Antagonists, we then investigated EAA Receptor subtypes involved in the spontaneous firing rate of reticulata neurons. Kynurenic acid and (±)-2-amino-5-phosphonopentanoic acid (AP-5) markedly decreased the spontaneous firing rate of reticulata neurons, while 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was much less effective. The Metabotropic Receptor Antagonist (R,S)-α-methyl-4-carboxyphenylglycine (MCPG) failed to affect the spontaneous electrical activity. In contrast to CNQX, microapplications of AP-5 sometimes produced total inhibition. This powerful effect may reflect the potential importance of NMDA Receptors in regulating the activity of some reticulata neurons.
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Regulation of substantia nigra pars reticulata neuronal activity by excitatory amino acids
Naunyn-Schmiedeberg's Archives of Pharmacology, 1999Co-Authors: Patricia Schmitt, Fabienne Soulière, C. Dugast, Guy ChouvetAbstract:Midbrain non-dopaminergic neurons of the substantia nigra pars reticulata play an important role in the basal ganglia circuitry. The regulation of their electrical activity by excitatory amino acid (EAA) inputs was investigated using in vivo electrophysiological methods in chloral hydrate-anaesthetized rats. We first determined the subtypes of EAA Receptors present on reticulata neurons, using microiontophoretic application of selective agonists: kainic acid (KA), (±)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N -methyl- d -aspartic acid (NMDA), and trans -(±)-1-amino-1,3-cyclopentanedicarboxylic acid ( trans -ACPD). Each agonist activated reticulata neurons and the apparent rank order of efficacy was: KA≥AMPA=NMDA> trans -ACPD. Using pressure or iontophoretic microejections of ionotropic and Metabotropic Receptor Antagonists, we then investigated EAA Receptor subtypes involved in the spontaneous firing rate of reticulata neurons. Kynurenic acid and (±)-2-amino-5-phosphonopentanoic acid (AP-5) markedly decreased the spontaneous firing rate of reticulata neurons, while 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was much less effective. The Metabotropic Receptor Antagonist ( R,S )-α-methyl-4-carboxyphenylglycine (MCPG) failed to affect the spontaneous electrical activity. In contrast to CNQX, microapplications of AP-5 sometimes produced total inhibition. This powerful effect may reflect the potential importance of NMDA Receptors in regulating the activity of some reticulata neurons. These results indicate that both functional ionotropic (NMDA and non-NMDA) and Metabotropic EAA Receptors are present on non-dopaminergic substantia nigra pars reticulata neurons. Moreover, in the anaesthetized animal, the spontaneous firing rate of these neurons, mediated by EAA inputs, seems mainly due to the tonic activation of ionotropic, but not Metabotropic, Receptors.
Patricia Schmitt - One of the best experts on this subject based on the ideXlab platform.
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Regulation of substantia nigra pars reticulata neuronal activity by excitatory amino acids.
Naunyn-Schmiedeberg's archives of pharmacology, 1999Co-Authors: Patricia Schmitt, Fabienne Soulière, C. Dugast, Guy ChouvetAbstract:Midbrain non-dopaminergic neurons of the substantia nigra pars reticulata play an important role in the basal ganglia circuitry. The regulation of their electrical activity by excitatory amino acid (EAA) inputs was investigated using in vivo electrophysiological methods in chloral hydrate-anaesthetized rats. We first determined the subtypes of EAA Receptors present on reticulata neurons, using microiontophoretic application of selective agonists: kainic acid (KA), (±)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N-methyl-d-aspartic acid (NMDA), and trans-(±)-1-amino-1,3-cyclopentanedicarboxylic acid (trans-ACPD). Each agonist activated reticulata neurons and the apparent rank order of efficacy was: KA≥AMPA=NMDA>trans-ACPD. Using pressure or iontophoretic microejections of ionotropic and Metabotropic Receptor Antagonists, we then investigated EAA Receptor subtypes involved in the spontaneous firing rate of reticulata neurons. Kynurenic acid and (±)-2-amino-5-phosphonopentanoic acid (AP-5) markedly decreased the spontaneous firing rate of reticulata neurons, while 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was much less effective. The Metabotropic Receptor Antagonist (R,S)-α-methyl-4-carboxyphenylglycine (MCPG) failed to affect the spontaneous electrical activity. In contrast to CNQX, microapplications of AP-5 sometimes produced total inhibition. This powerful effect may reflect the potential importance of NMDA Receptors in regulating the activity of some reticulata neurons.
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Regulation of substantia nigra pars reticulata neuronal activity by excitatory amino acids
Naunyn-Schmiedeberg's Archives of Pharmacology, 1999Co-Authors: Patricia Schmitt, Fabienne Soulière, C. Dugast, Guy ChouvetAbstract:Midbrain non-dopaminergic neurons of the substantia nigra pars reticulata play an important role in the basal ganglia circuitry. The regulation of their electrical activity by excitatory amino acid (EAA) inputs was investigated using in vivo electrophysiological methods in chloral hydrate-anaesthetized rats. We first determined the subtypes of EAA Receptors present on reticulata neurons, using microiontophoretic application of selective agonists: kainic acid (KA), (±)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N -methyl- d -aspartic acid (NMDA), and trans -(±)-1-amino-1,3-cyclopentanedicarboxylic acid ( trans -ACPD). Each agonist activated reticulata neurons and the apparent rank order of efficacy was: KA≥AMPA=NMDA> trans -ACPD. Using pressure or iontophoretic microejections of ionotropic and Metabotropic Receptor Antagonists, we then investigated EAA Receptor subtypes involved in the spontaneous firing rate of reticulata neurons. Kynurenic acid and (±)-2-amino-5-phosphonopentanoic acid (AP-5) markedly decreased the spontaneous firing rate of reticulata neurons, while 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was much less effective. The Metabotropic Receptor Antagonist ( R,S )-α-methyl-4-carboxyphenylglycine (MCPG) failed to affect the spontaneous electrical activity. In contrast to CNQX, microapplications of AP-5 sometimes produced total inhibition. This powerful effect may reflect the potential importance of NMDA Receptors in regulating the activity of some reticulata neurons. These results indicate that both functional ionotropic (NMDA and non-NMDA) and Metabotropic EAA Receptors are present on non-dopaminergic substantia nigra pars reticulata neurons. Moreover, in the anaesthetized animal, the spontaneous firing rate of these neurons, mediated by EAA inputs, seems mainly due to the tonic activation of ionotropic, but not Metabotropic, Receptors.
I Izquierdo - One of the best experts on this subject based on the ideXlab platform.
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Novelty enhances retrieval of one-trial avoidance learning in rats 1 or 31 days after training unless the hippocampus is inactivated by different Receptor Antagonists and enzyme inhibitors.
Behavioural brain research, 2000Co-Authors: L A Izquierdo, D M Barros, J H Medina, I IzquierdoAbstract:Rats were implanted bilaterally with cannulae in the CA1 region of the dorsal hippocampus. The animals were trained in one-trial step-down inhibitory avoidance and tested either 1 or 31 days later. Some of the animals were exposed, 1 h prior to retention testing, to a novel environment. This was a 50-cm high, 50-cm wide and 39-cm high wooden box covered on the inside with black plastic. Through the cannulae, 10 min prior to the retention test, the rats received 0.5-microl infusions of saline, of a vehicle (2% dimethylsulfoxide in saline), or of the following drugs: the glutamate NMDA Receptor blocker, aminophosphonopentanoic acid (AP5, 5.0 microg), the AMPA Receptor blocker, 6,7-cyanonitroquinoxaline-2,3-dione (CNQX, 1.25 microg), the generic glutamate Metabotropic Receptor Antagonist, alpha-methyl-(4-carboxyphenyl)glycine (MCPG), the inhibitor of cAMP-dependent protein kinase (PKA), Rp-cAMPs (0.1 or 0.5 microg), or the inhibitor of the mitogen-activated protein kinase (MAPK), PD098059 (10 or 50 microM). CNQX and PD098059 were dissolved in the vehicle; AP5 and Rp-cAMPs were dissolved in saline. All these drugs except AP5 had been previously found to alter retrieval of this task. Novelty markedly enhanced retention test performance of the avoidance task. The drugs, in accordance with previous results, and with the exception of AP5 at any of the two training-test intervals and of CNQX at the 31-day interval, hindered retention test performance. The results indicate that the effect of novelty on retrieval can not be observed if the major biochemical mechanisms of retrieval (AMPA Receptors, PKA, MAPK) are blocked, i.e. if the hippocampus was temporarily inactivated by drugs that inhibit those mechanisms.
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Different hippocampal molecular requirements for short- and long-term retrieval of one-trial avoidance learning.
Behavioural brain research, 2000Co-Authors: L A Izquierdo, D M Barros, J H Medina, P G Ardenghi, P Pereira, C Rodrigues, H Choi, I IzquierdoAbstract:Rats were trained in one-trial step-down inhibitory avoidance and tested either 3 h or 31 days later. Ten minutes prior to the retention test, through indwelling cannulae placed in the CA1 region of the dorsal hippocampus, they received 0.5 microl infusions of: saline, a vehicle (2% dimethylsulfoxide in saline), the glutamate NMDA Receptor blocker, aminophosphonopentanoic acid (AP5) (5.0 microg), the AMPA/kainate Receptor blocker, cyanonitroquinoxaline dione (CNQX) (0.25 or 1.25 microg), the Metabotropic Receptor Antagonist, methylcarboxyphenylglycine (MCPG) (0.5 or 2.5 microg), the inhibitor of calcium/calmodulin-dependent protein kinase II (KN62) (3.5 microg), the inhibitor of cAMP-dependent protein kinase (PKA), Rp-cAMPs (0.1 or 0.5 microg), the stimulant of the same enzyme, Sp-cAMPs (0.1 or 0.5 microg), or the inhibitor of the mitogen-activated protein kinase (MAPK) kinase, PD098059 (10 or 50 microM). CNQX, KN62 and PD098059 were dissolved in the vehicle; the other drugs were dissolved in saline. All these drugs, at the same doses, had been previously found to affect short- and long-term memory formation of this task. Retrieval measured 3 h after training (short-term memory) was blocked by CNQX and MCPG, and was unaffected by all the other drugs. In contrast, retrieval measured at 31 days was blocked by MCPG, Rp-cAMPs and PD098059, enhanced by Sp-cAMPs, and unaffected by CNQX, AP5 or KN62. The results indicate that, in CA1, glutamate Metabotropic Receptors are necessary for the retrieval of both short- and long-term memory; AMPA/kainate Receptors are necessary for short-term but not long-term memory retrieval, and NMDA Receptors are uninvolved in retrieval. Both the PKA and MAPK signalling pathways are required for the retrieval of long-term but not short-term memory.
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Molecular signalling pathways in the cerebral cortex are required for retrieval of one-trial avoidance learning in rats.
Behavioural brain research, 2000Co-Authors: D M Barros, L A Izquierdo, J H Medina, P G Ardenghi, P Pereira, T Mello E Souza, I IzquierdoAbstract:Rats were implanted bilaterally with cannulae in the CA1 region of the dorsal hippocampus, the entorhinal cortex, anterior cingulate cortex, posterior parietal cortex, or the basolateral complex of the amygdala. The animals were trained in one-trial step-down inhibitory avoidance and tested 24 h later. Prior (10 min) to the retention test, through the cannulae, they received 0.5 microl infusions of a vehicle (2% dimethylsulfoxide in saline), or of the following drugs dissolved in the vehicle: the glutamate NMDA Receptor blocker, aminophosphonopentanoic acid (AP5, 2.0 or 5.0 microg), the AMPA Receptor blocker, 6,7-dinitroquinoxaline-2,3 (1H,4H)dione (DNQX, 0.4 or 1.0 microg), the Metabotropic Receptor Antagonist, methylcarboxyphenylglycine (MCPG, 0.5 or 2.5 microg), the inhibitor of cAMP-dependent protein kinase (PKA), Rp-cAMPs (0.1 or 0.5 microg), the PKA stimulant, Sp-cAMPs (0.5 microg), or the inhibitor of the mitogen-activated protein kinase (MAPK), PD098059 (10 or 50 microM). All these drugs, at the same doses, had been previously found to alter long-term memory formation of this task. Here, retrieval test performance was blocked by DNQX, MCPG, Rp-cAMPs and PD098059 and enhanced by Sp-cAMPs infused into CA1 or the entorhinal cortex. The drugs had similar effects when infused into the parietal or anterior cingulate cortex, except that in these two areas AP5 also blocked retrieval, and in the cingulate cortex DNQX had no effect. Infusions into the basolateral amygdala were ineffective except for DNQX, which hindered retrieval. None of the treatments that affected retrieval had any influence on performance in an open field or in a plus maze; therefore, their effect on retention testing can not be attributed to an influence on locomotion, exploration or anxiety. The results indicate that the four cortical regions studied participate actively in, and are necessary for, retrieval of the one-trial avoidance task. They require Metabotropic and/or NMDA glutamate Receptors and PKA and MAPK activity. In contrast, the basolateral amygdala appears to participate only through a maintenance of its regular excitatory transmission mediated by glutamate AMPA Receptors.
C. Dugast - One of the best experts on this subject based on the ideXlab platform.
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Regulation of substantia nigra pars reticulata neuronal activity by excitatory amino acids.
Naunyn-Schmiedeberg's archives of pharmacology, 1999Co-Authors: Patricia Schmitt, Fabienne Soulière, C. Dugast, Guy ChouvetAbstract:Midbrain non-dopaminergic neurons of the substantia nigra pars reticulata play an important role in the basal ganglia circuitry. The regulation of their electrical activity by excitatory amino acid (EAA) inputs was investigated using in vivo electrophysiological methods in chloral hydrate-anaesthetized rats. We first determined the subtypes of EAA Receptors present on reticulata neurons, using microiontophoretic application of selective agonists: kainic acid (KA), (±)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N-methyl-d-aspartic acid (NMDA), and trans-(±)-1-amino-1,3-cyclopentanedicarboxylic acid (trans-ACPD). Each agonist activated reticulata neurons and the apparent rank order of efficacy was: KA≥AMPA=NMDA>trans-ACPD. Using pressure or iontophoretic microejections of ionotropic and Metabotropic Receptor Antagonists, we then investigated EAA Receptor subtypes involved in the spontaneous firing rate of reticulata neurons. Kynurenic acid and (±)-2-amino-5-phosphonopentanoic acid (AP-5) markedly decreased the spontaneous firing rate of reticulata neurons, while 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was much less effective. The Metabotropic Receptor Antagonist (R,S)-α-methyl-4-carboxyphenylglycine (MCPG) failed to affect the spontaneous electrical activity. In contrast to CNQX, microapplications of AP-5 sometimes produced total inhibition. This powerful effect may reflect the potential importance of NMDA Receptors in regulating the activity of some reticulata neurons.
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Regulation of substantia nigra pars reticulata neuronal activity by excitatory amino acids
Naunyn-Schmiedeberg's Archives of Pharmacology, 1999Co-Authors: Patricia Schmitt, Fabienne Soulière, C. Dugast, Guy ChouvetAbstract:Midbrain non-dopaminergic neurons of the substantia nigra pars reticulata play an important role in the basal ganglia circuitry. The regulation of their electrical activity by excitatory amino acid (EAA) inputs was investigated using in vivo electrophysiological methods in chloral hydrate-anaesthetized rats. We first determined the subtypes of EAA Receptors present on reticulata neurons, using microiontophoretic application of selective agonists: kainic acid (KA), (±)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N -methyl- d -aspartic acid (NMDA), and trans -(±)-1-amino-1,3-cyclopentanedicarboxylic acid ( trans -ACPD). Each agonist activated reticulata neurons and the apparent rank order of efficacy was: KA≥AMPA=NMDA> trans -ACPD. Using pressure or iontophoretic microejections of ionotropic and Metabotropic Receptor Antagonists, we then investigated EAA Receptor subtypes involved in the spontaneous firing rate of reticulata neurons. Kynurenic acid and (±)-2-amino-5-phosphonopentanoic acid (AP-5) markedly decreased the spontaneous firing rate of reticulata neurons, while 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was much less effective. The Metabotropic Receptor Antagonist ( R,S )-α-methyl-4-carboxyphenylglycine (MCPG) failed to affect the spontaneous electrical activity. In contrast to CNQX, microapplications of AP-5 sometimes produced total inhibition. This powerful effect may reflect the potential importance of NMDA Receptors in regulating the activity of some reticulata neurons. These results indicate that both functional ionotropic (NMDA and non-NMDA) and Metabotropic EAA Receptors are present on non-dopaminergic substantia nigra pars reticulata neurons. Moreover, in the anaesthetized animal, the spontaneous firing rate of these neurons, mediated by EAA inputs, seems mainly due to the tonic activation of ionotropic, but not Metabotropic, Receptors.
Fabienne Soulière - One of the best experts on this subject based on the ideXlab platform.
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Regulation of substantia nigra pars reticulata neuronal activity by excitatory amino acids.
Naunyn-Schmiedeberg's archives of pharmacology, 1999Co-Authors: Patricia Schmitt, Fabienne Soulière, C. Dugast, Guy ChouvetAbstract:Midbrain non-dopaminergic neurons of the substantia nigra pars reticulata play an important role in the basal ganglia circuitry. The regulation of their electrical activity by excitatory amino acid (EAA) inputs was investigated using in vivo electrophysiological methods in chloral hydrate-anaesthetized rats. We first determined the subtypes of EAA Receptors present on reticulata neurons, using microiontophoretic application of selective agonists: kainic acid (KA), (±)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N-methyl-d-aspartic acid (NMDA), and trans-(±)-1-amino-1,3-cyclopentanedicarboxylic acid (trans-ACPD). Each agonist activated reticulata neurons and the apparent rank order of efficacy was: KA≥AMPA=NMDA>trans-ACPD. Using pressure or iontophoretic microejections of ionotropic and Metabotropic Receptor Antagonists, we then investigated EAA Receptor subtypes involved in the spontaneous firing rate of reticulata neurons. Kynurenic acid and (±)-2-amino-5-phosphonopentanoic acid (AP-5) markedly decreased the spontaneous firing rate of reticulata neurons, while 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was much less effective. The Metabotropic Receptor Antagonist (R,S)-α-methyl-4-carboxyphenylglycine (MCPG) failed to affect the spontaneous electrical activity. In contrast to CNQX, microapplications of AP-5 sometimes produced total inhibition. This powerful effect may reflect the potential importance of NMDA Receptors in regulating the activity of some reticulata neurons.
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Regulation of substantia nigra pars reticulata neuronal activity by excitatory amino acids
Naunyn-Schmiedeberg's Archives of Pharmacology, 1999Co-Authors: Patricia Schmitt, Fabienne Soulière, C. Dugast, Guy ChouvetAbstract:Midbrain non-dopaminergic neurons of the substantia nigra pars reticulata play an important role in the basal ganglia circuitry. The regulation of their electrical activity by excitatory amino acid (EAA) inputs was investigated using in vivo electrophysiological methods in chloral hydrate-anaesthetized rats. We first determined the subtypes of EAA Receptors present on reticulata neurons, using microiontophoretic application of selective agonists: kainic acid (KA), (±)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N -methyl- d -aspartic acid (NMDA), and trans -(±)-1-amino-1,3-cyclopentanedicarboxylic acid ( trans -ACPD). Each agonist activated reticulata neurons and the apparent rank order of efficacy was: KA≥AMPA=NMDA> trans -ACPD. Using pressure or iontophoretic microejections of ionotropic and Metabotropic Receptor Antagonists, we then investigated EAA Receptor subtypes involved in the spontaneous firing rate of reticulata neurons. Kynurenic acid and (±)-2-amino-5-phosphonopentanoic acid (AP-5) markedly decreased the spontaneous firing rate of reticulata neurons, while 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was much less effective. The Metabotropic Receptor Antagonist ( R,S )-α-methyl-4-carboxyphenylglycine (MCPG) failed to affect the spontaneous electrical activity. In contrast to CNQX, microapplications of AP-5 sometimes produced total inhibition. This powerful effect may reflect the potential importance of NMDA Receptors in regulating the activity of some reticulata neurons. These results indicate that both functional ionotropic (NMDA and non-NMDA) and Metabotropic EAA Receptors are present on non-dopaminergic substantia nigra pars reticulata neurons. Moreover, in the anaesthetized animal, the spontaneous firing rate of these neurons, mediated by EAA inputs, seems mainly due to the tonic activation of ionotropic, but not Metabotropic, Receptors.