dizocilpine-maleate and 1-amino-1-3-dicarboxycyclopentane

Human primary and clonal synovial cells were incubated with glutamate receptor agonists to assess their modulating influence on glutamate receptors N-methyl-d-aspartate (NMDA) NR1 and NR2 and inflammatory cytokines to determine potential for paracrine or autocrine (neurocrine) upregulation of glutamate receptors, as has been shown for bone and chondrocytes. Clonal SW982 synoviocytes constitutively express vimentin, smooth muscle actin (SMA), and NMDA NR1 and NR2. Coincubation (6 h) with glutamate agonists NMDA (5 microM), and the NMDA NR1 glycine site activator (+/-)1-aminocyclopentane-cis-1,3-dicarboxylic acid (5 muM), significantly increases cellular mRNA and protein levels of glutamate receptors, as well as increasing vimentin, SMA, tumor necrosis factor-alpha, and RANTES (regulated on activation, normal T-cell expressed and secreted), assessed qualitatively and quantitatively with nucleotide amplification, image analysis of immunocytochemical staining, fluorescein-activated cell sorting, Western blotting, and immunoassays. Human primary synovial cells harvested from patients with arthritic conditions also constitutively expressed NMDA NR1 with increases after agonist treatment. Glutamate receptor agonist-induced increases were blocked by the noncompetitive glutamate antagonist MK-801 (8 microg/ml) and NR1 blocking antibody. Coincubation with glutamate agonists and phorbol 12-myristate 13-acetate, a protein kinase C activator, significantly enhanced mean levels of TNF-alpha and RANTES in SW982 cell supernatants compared with incubation with either agent alone. Increases were diminished with protein kinase inhibitor and NR1 blocking antibody. The functional activation of glutamate receptors on human synoviocytes establishes a neurogenic cell signaling link between neurotransmitter glutamate released from nerve terminals and target cells in the joint capsule. The influence of glutamate on subsequent release of cellular proinflammatory mediators in non-neural tissue for activation of downstream immune events supports a peripheral neuroimmune link in arthritis.

Topics: Animals; Arthritis; CD11b Antigen; Cell Line, Tumor; Chemokine CCL5; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Humans; N-Methylaspartate; Neurogenic Inflammation; Neuroimmunomodulation; Protein Kinase C; Rats; Receptors, Complement 3d; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; RNA, Messenger; Sarcoma, Synovial; Synovial Membrane; Synovitis; Tumor Necrosis Factor-alpha; Up-Regulation; Vimentin

The excitatory amino acids (EAAs) transporters regulate the balance between physiological and pathological signaling over stimulation of the glutamatergic system pathway. The effect of transportable substrates and glutamate (Glu) receptor agonists on Glu uptake in neuronal cells was assessed at different conditions. Cells pre-incubated with Glu, L- or D-aspartate (Asp) and washed presented an inhibition on [(3)H]-Glu uptake and this effect was not mimicked by Glu receptors agonists. The effects of L- and D-Asp were not altered by the presence of N-methyl-d-aspartate (NMDA) receptor antagonists. Thus, the reduction on Glu uptake induced by EAAs is probably linked to the transporter activity. In contrast, the presence of NMDA or (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (SR-ACPD) during the pre-incubation and the [(3)H]-Glu uptake assay period increased Glu uptake, whilst kainic acid (KA) had no effect. The NMDA effect was not altered by its antagonists (+/-)-2-amino-5-phosphonopentanoic acid (AP-5) or dizocilpine (MK-801). The SR-ACPD effect was due to the activation of metabotropic Glu receptor, since it was abolished by its antagonist, L(+/-)-2-amino-3-phosphonopropionic acid (L-AP3). Thus, the current studies suggest that the neuronal EAAs transporter is regulated in different manner by transportable substrates and Glu receptor agonists. The possible involvement of this modulation after certain neurotoxicity insults is discussed.

Topics: Amino Acid Transport System X-AG; Animals; Animals, Newborn; Aspartic Acid; Cells, Cultured; Cerebellum; Cycloleucine; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Interactions; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Ligands; N-Methylaspartate; Naphthalenes; Neurons; Neuroprotective Agents; Oxepins; Rats; Rats, Wistar; Receptors, Glutamate; Tritium; Valine

l-Glutamate is a major excitatory neurotransmitter that binds ionotropic and metabotropic glutamate receptors. Cerebral endothelial cells from many species have been shown to express several forms of glutamate receptors; however, human cerebral endothelial cells have not been shown to express either the N-methyl-D-aspartate (NMDA) receptor message or protein. This study provides evidence that human cerebral endothelial cells express the message and protein for NMDA receptors. Human cerebral endothelial cell monolayer electrical resistance changes in response to glutamate receptor agonists, antagonists, and second message blockers were tested. RT-PCR and Western blot analysis were used to demonstrate the presence of the NMDA receptor. Glutamate and NMDA (1 mM) caused a significant decrease in electrical resistance compared with sham control at 2 h postexposure; this response could be blocked significantly by MK-801 (an NMDA antagonist), 8-(N,N-diethylamino)-n-octyl-3,4,5-trimethyoxybenzoate (an intracellular Ca2+ antagonist), and N-acetyl-L-cystein (an antioxidant). Trans(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid, a metabotropic receptor agonist (1 mM), did not significantly decrease electrical resistance. Our results are consistent with a model where glutamate, at excitotoxic levels, may lead to a breakdown in the blood brain barrier via activation of NMDA receptors.

Topics: Biological Transport; Blood-Brain Barrier; Blotting, Western; Brain; Calcium; Cells, Cultured; Cycloleucine; Dizocilpine Maleate; Endothelial Cells; Excitatory Amino Acid Antagonists; Glutamic Acid; Humans; Neuroprotective Agents; Reactive Oxygen Species; Receptors, N-Methyl-D-Aspartate; Reverse Transcriptase Polymerase Chain Reaction

Disruption of glutamate homeostasis frequently leads to oxidative stress and to the release of hydroxyl radicals (radical OH). Here, we investigated, via a microdialysis approach, the possible involvement of metabotropic glutamate receptors in the glutamate-induced release of hydroxyl radicals in adult rat striatum. Glutamate was applied at low amount, resulting in a moderate release that was not inhibited by dizocilpine (MK-801), a specific NMDA receptor antagonist. (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG), a broad spectrum metabotropic antagonist, that does not exert any effect on the basal release of radical OH suppressed their response to glutamate. (+/-)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (t-ACPD), a non-selective metabotropic glutamate receptors agonist, promoted an radical OH release almost similar to that observed after glutamate, which was similarly impaired by co-infusion with MCPG. By contrast, infusion of (RS)-3,5-dihydroxyphenylglycine (DHPG), a more specific group I metabotropic glutamate receptors agonist, did not result in any appreciable radical OH response. Thus, beside NMDA receptors, some metabotropic glutamate receptors may also be involved in the glutamate-induced release of hydroxyl radicals.

Topics: Analysis of Variance; Animals; Corpus Striatum; Cycloleucine; Dizocilpine Maleate; Drug Interactions; Excitatory Amino Acid Antagonists; Glutamic Acid; Glycine; Hydroxyl Radical; Male; Methoxyhydroxyphenylglycol; Rats; Rats, Wistar; Receptors, Metabotropic Glutamate; Time Factors

Na/K-ATPase prepared from cerebellum granule cells of 10-12-day-old mice is inhibited by glutamate and its agonists, NMDA (ligand for ionotropic receptors) and ACPD (ligand for metabotropic receptors). The inhibition is specific and prevented by subsequent antagonists (MK-801 for ionotropic NMDA-receptors and MCPG for metabotropic receptors). The inhibiting effect of NMDA is significantly reversed by cysteine and that of ACPD by chelerythrine or indolyl maleimide. It is concluded that ionotropic receptors inhibit Na/K-ATPase because of intracellular production of reactive oxygen species, and metabotropic receptors mediate their effect via protein kinase C.

Topics: Alkaloids; Animals; Benzoates; Benzophenanthridines; Cerebellum; Cycloleucine; Cysteine; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Female; Glutamates; Glycine; Male; Mice; Mice, Inbred AKR; N-Methylaspartate; Neurons; Phenanthridines; Receptors, Glutamate; Sodium-Potassium-Exchanging ATPase

Carbon monoxide (CO) has been identified as an endogenous biological messenger in the brain. Heme oxygenase catalyzes the metabolism of heme to biliverdin and CO. Recent studies have demonstrated that CO is involved in central cardiovascular regulation and modulates the baroreflex in the nucleus tractus solitarii of rats. The purpose of the present study was to investigate the possible interaction of CO and excitatory amino acids in the nucleus tractus solitarii. In anesthetized male Sprague-Dawley rats, unilateral intranucleus tractus solitarii microinjection of hematin, a heme molecule cleaved by heme oxygenase to yield CO, or excitatory amino acids L-glutamate produced depressor and bradycardiac effects. Similar cardiovascular effects were observed with several agonists for ionotropic glutamate receptors such as N-methyl-D-aspartate (NMDA), (+/-)-alpha-amino-3-hydroxyl-5-methylisoxazole-4-propanoic acid (AMPA), kainic acid and for metabotropic glutamate (mGlu) receptors, trans-(+/-)-1-amino-(1S,3R)-cyclopentanedicarboxylic acid (ACPD). Among these agonists, prior administration of the heme oxygenase inhibitor, zinc deuteroporphyrin 2,4-bis glycol (ZnDPBG) (1 nmol), significantly attenuated the cardiovascular effects of hematin, L-glutamate and ACPD. Furthermore, the cardiovascular effects of ACPD were prevented by the selective mGlu receptors antagonist L-2-amino-3-phosphonoprionate (L-AP3). However, pretreatment with ZnDPBG failed to prevent the cardiovascular responses to microinjection of NMDA, AMPA and kainic acid. On the other hand, prior administration of the NMDA receptor antagonist, diazocilpine (MK-801), or (+/-)-2-amino-5-phosphonopentanoic acid (APV) attenuated the depressor and bradycardiac effect of hematin. These results demonstrated that mGlu receptors may couple to the activation of heme oxygenase via the liberation of CO to participate in central cardiovascular regulation. They also suggested that CO and excitatory amino acids may interact in the nucleus tractus solitarii of rats.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Blood Pressure; Carbon Monoxide; Cardiovascular System; Cycloleucine; Deuteroporphyrins; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glutamic Acid; Heart Rate; Heme Oxygenase (Decyclizing); Hemin; Kainic Acid; Male; N-Methylaspartate; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate; Solitary Nucleus

Autoradiographical studies revealed that 10 nM [3H]N-acetyl-aspartyl-glutamate (NAAG) labelled grey matter structures, particularly in the hippocamus, cerebral neocortex, striatum, septal nuclei and the cerebellar cortex. The binding was inhibited by (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)-glycine (DCG IV), an agonist at group II metabotropic glutamate receptors (mGluR II). (RS)-alpha-Methyl-4-tetrazolylphenylglycine (MTPG), (RS)-alpha-cyclopropyl-4-phosphonoglycine (CPPG) and (RS)-alpha-methylserine-O-phosphate monophenyl ester (MSOPPE), all antagonists at mGluR II and mGluR III, also inhibited [3H]NAAG binding. Other inhibitors were (1S,3R)-1-aminocyclopentane-1,3-dicarboxylate (ACPD), a broad-spectrum mGluR agonist with preference for groups I and II and the mGluR I agonists/mGluR II antagonists (S)-3-carboxy-4-hydroxyphenylglycine (3,4-CHPG) and (S)-4-carboxy-3-hydroxyphenylglycine (4,3-CHPG). Neither the mGluR I specific agonist (S)-dihydroxyphenylglycine nor any of the ionotropic glutamate receptor ligands such as kainate, AMPA and MK-801 had strong effects (except for the competitive NMDA antagonist CGS 19755, which produced 20-40% inhibition at 100 microM) suggesting that, at low nM concentrations, [3H]NAAG binds predominantly to metabotropic glutamate receptors, particularly those of the mGluR II type. Several studies have indicated that NAAG can interact with mGluR II and the present study supports this notion by demonstrating that sites capable of binding NAAG at low concentrations and displaying pharmacological characteristics of mGluR II exist in the central nervous tissue. Furthermore, the results show that autoradiography of [3H]NAAG binding can be used to quantify the distribution of such sites in distinct brain regions and study their pharmacology at the same time.

Topics: Alanine; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Binding Sites; Brain; Brain Chemistry; Carboxypeptidases; Cold Temperature; Cycloleucine; Cyclopropanes; Dipeptides; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Female; Glutamate Carboxypeptidase II; Glycine; Kainic Acid; Male; Nerve Tissue Proteins; Phosphoserine; Pipecolic Acids; Rats; Rats, Sprague-Dawley; Receptors, Glutamate; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate; Tetrazoles

The potential toxic effects of the metabotropic glutamate receptor agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) and its interactions with the N-methyl-D-aspartate (NMDA) receptor were studied in hippocampal brain slice cultures, using densitometric measurements of the cellular uptake of propidium iodide (PI) to quantify neuronal degeneration. Cultures exposed to ACPD, showed a concentration (2-5 mM) and time (1-4 days) dependent increase in PI uptake in CA1, CA3 and dentate subfields after 24 h and 48 h of exposure, with CA1 pyramidal cells being most sensitive. The neurodegeneration induced by 2 mM ACPD was completely abolished by addition of 10 microM of the NMDA receptor antagonist (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801), while 20 microM of the 2-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)/kainic acid receptor antagonist 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX) had no effect. Co-exposing cultures to a subtoxic dose of 300 microM ACPD together with 10 microM NMDA, which at this dose is known to induce a fairly selective degeneration of CA1 pyramidal cells, significantly increased the PI uptake in both CA1 and CA3, compared to cultures exposed to 10 microM NMDA only. Adding the 300 microM ACPD as pretreatment for 30 min followed by a 30 min wash in normal medium before the ACPD/NMDA co-exposure, eliminated the potentiation of NMDA toxicity. The potentiation was also blocked by addition of 10 or 100 microM 2-methyl-6-(phenylethynyl)pyridine (MPEP) (mGluR5 antagonist) during the co-exposure, while a corresponding addition of 10 or 100 microM 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt) (mGluR1 antagonist) had no effect. We conclude that, stimulation of metabotropic glutamate receptors with ACPD at concentrations of 2 mM or higher induces a distinct subfield-related and time and concentration dependent pattern of hippocampal degeneration, and that ACPD at subtoxic concentrations modulates NMDA-induced excitotoxicity through the mGluR5 receptor in a time dependent way.

Topics: Animals; Coloring Agents; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Hippocampus; Immunohistochemistry; In Vitro Techniques; Microtubule-Associated Proteins; N-Methylaspartate; Nerve Tissue Proteins; Neurotoxins; Propidium; Quinoxalines; Rats; Rats, Wistar; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate; Staining and Labeling

Regulation of neuronal NMDA receptors (NMDARs) by group I metabotropic glutamate receptors (mGluRs) is known to play a critical role in synaptic transmission. The molecular mechanisms underlying mGluR1-mediated potentiation of NMDARs are as yet unclear. The present study shows that in Xenopus oocytes expressing recombinant receptors, activation of mGluR1 potentiates NMDA channel activity by recruitment of new channels to the plasma membrane via regulated exocytosis. Activation of mGluR1alpha induced (1) an increase in channel number times channel open probability, with no change in mean open time, unitary conductance, or reversal potential; (2) an increase in charge transfer in the presence of NMDA and the open channel blocker MK-801, indicating an increased number of functional NMDARs in the cell membrane; and (3) increased NR1 surface expression, as indicated by cell surface Western blots and immunofluorescence. Botulinum neurotoxin A or expression of a dominant negative mutant of synaptosomal associated protein of 25 kDa molelcular mass (SNAP-25) greatly reduced mGluR1alpha-mediated potentiation, indicating that receptor trafficking occurs via a SNAP-25-mediated form of soluble N-ethylmaleimide sensitive fusion protein attachment protein receptor-dependent exocytosis. Because group I mGluRs are localized to the perisynaptic region in juxtaposition to synaptic NMDARs at glutamatergic synapses in the hippocampus, mGluR-mediated insertion of NMDARs may play a role in synaptic transmission and plasticity, including long-term potentiation.

Topics: Animals; Blotting, Western; Botulinum Toxins, Type A; Cell Membrane; Cells, Cultured; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Exocytosis; Fluorescent Antibody Technique; Ion Channel Gating; Membrane Potentials; Membrane Proteins; N-Methylaspartate; Nerve Tissue Proteins; Oocytes; Patch-Clamp Techniques; Protein Transport; Rats; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate; Synaptosomal-Associated Protein 25; Transfection; Xenopus

Glutamate-induced glutamate release may be involved in the delayed neuronal death induced by N-methyl-D-aspartate (NMDA). In order to examine a possible modulatory effect of the presynaptic group III mGluRs on glutamate excitotoxicity, the effect of L-2-amino-4-phosphonobutyrate (L-AP4) was examined on NMDA-induced delayed death of mouse cerebellar granule neurons in culture. We found that L-AP4, at high concentration (in the millimolar range), inhibited in a non-competitive manner the NMDA-induced toxicity. This effect was mimicked by high concentration of L-serine-o-phosphate (L-SOP), and was inhibited by pertussis toxin (PTX) indicating the involvement of a Gi/o protein. This suggests the involvement of mGluR7 in the L-AP4 effect, and this was consistent with the detection of both mGluR7 protein and mRNA in these cultured neurons. To examine the mechanism of the L-AP4-induced protection from excitotoxic damage, the effect of L-AP4 on glutamate release was examined. L-AP4 (> or = 1 mM) noncompetitively inhibited by more than 60% the glutamate release induced by NMDA during the insult. We also observed that the 10-min NMDA receptor stimulation resulted in a dramatic increase in the extracellular glutamate concentration reaching 6000% of the control value 24 h after the insult. This large increase was also inhibited when NMDA was applied in the presence of > or = 1 mM L-AP4. Part of the L-AP4-induced protection from excitotoxic damage of granule neurons may therefore result from the inhibition of the vicious cycle: dying cells release glutamate, glutamate induced cell death. The present results add to the hypothesis that presynaptic mGluRs, probably mGluR7, may be the targets of drugs decreasing glutamate release and then neuronal death observed in some pathological situations.

Topics: Animals; Calcium Channels; Cell Death; Cells, Cultured; Cerebellum; Cyclic GMP; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glutamic Acid; Kainic Acid; Mice; Microtubule-Associated Proteins; N-Methylaspartate; Neurons; Neuroprotective Agents; Neurotoxins; Patch-Clamp Techniques; Phosphoserine; Propionates; Receptors, AMPA; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate

Activation of glutamate receptors has been implicated in excitotoxicity. Here, we have investigated whether subtoxic concentrations of glutamate can modulate neuronal death in the developing retina. Explants of rat retinas were pre-incubated with glutamate, N-methyl-d-aspartate (NMDA), kainate, quisqualate or trans-1-amino-1,3-cyclopentanedicarboxylic acid (t-ACPD) for 18 h. Then, glutamate (6 mM) was added to the explants for an additional 6 h. Glutamate-induced degeneration was restricted to the emerging inner nuclear layer. Pre-incubation with glutamate, NMDA, or both, reduced glutamate-induced neuronal death and protected against neuronal death induced by irradiation (2 Gy). The NMDA receptor antagonists, 2-amino-5-phosphonovaleric acid (d-APV; 30 microM) or 5-methyl-10,11-dihydro-5H-dibenzocyclohepten-5,10-imine hydrogen maleate (MK-801; 30 microM), prevented glutamate-induced neuroprotection. To investigate whether this neuroprotection was mediated by neurotrophins, we incubated retinal explants with either brain-derived neurotrophic factor or neurotrophin-4. Both treatments resulted in partial protection against glutamate-induced neurotoxicity. Furthermore, NMDA mediated neuroprotection was totally reversed when a soluble form of the specific tyrosine kinase receptor B was simultaneously added to the explants. Our results suggest that activation of NMDA receptors may control neuronal death in the retina during development. This modulation seems to depend, at least in part, on the release of neurotrophins within the retina.

Topics: 2-Amino-5-phosphonovalerate; Animals; Apoptosis; Brain-Derived Neurotrophic Factor; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glutamic Acid; Kainic Acid; N-Methylaspartate; Nerve Growth Factors; Neuroprotective Agents; Quinoxalines; Quisqualic Acid; Rats; Rats, Inbred Strains; Receptor Protein-Tyrosine Kinases; Receptor, Ciliary Neurotrophic Factor; Receptors, N-Methyl-D-Aspartate; Receptors, Nerve Growth Factor; Retina

On-line in vivo microdialysis was used to determine the effects of a 16-min handling period on release of dopamine (DA) in the nucleus accumbens and of DA and noradrenaline (NA) in the medial prefrontal cortex of awake, freely moving rats. DA and NA were determined in one HPLC run. Handling resulted in an immediate and strong increase of both catecholamines in the prefrontal cortex. Maximal values for DA were 295%, and for NA 225%, of controls. DA in the nucleus accumbens was also increased (to 135% of controls) but only after a short delay. Local inhibition of ionotropic glutamate receptors by continuous reversed dialysis of the drugs 6-cyano-7-nitroquinoxaline, D-2-amino-5-phosphonopentanoic acid, or dizocilpine did not significantly affect handling-induced increases in cortical DA and NA release. Neither did the agonist of metabotropic glutamate receptors, trans-(1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), or the GABA-B agonist baclofen. Reversed dialysis of dizocilpine in the nucleus accumbens was equally ineffective, but ACPD inhibited the increase in DA release in this area. Stimulation of metabotropic glutamate receptors in the nucleus accumbens was previously reported to inhibit activation of DA release in that area after stimulation of glutamatergic or dopaminergic afferents. It is concluded that metabotropic receptors in the nucleus accumbens are important for the control of activation of DA release in the accumbens by physiological stimuli but that a similar mechanism is lacking in the prefrontal cortex.

Topics: 3,4-Dihydroxyphenylacetic Acid; 6-Cyano-7-nitroquinoxaline-2,3-dione; Animals; Baclofen; Cycloleucine; Dizocilpine Maleate; Dopamine; Excitatory Amino Acid Antagonists; GABA Agonists; Homovanillic Acid; Hydroxyindoleacetic Acid; Male; Microdialysis; Neuroprotective Agents; Norepinephrine; Nucleus Accumbens; Prefrontal Cortex; Rats; Rats, Wistar; Receptors, GABA-B; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate; Stress, Physiological

Expression of GAP-43 in the cerebellum and selected regions of the brain has been shown to be developmentally regulated. Localization of GAP-43 mRNA within granule cells of the immature and mature rat cerebellum has been demonstrated by in situ hybridization. Higher levels are detected in the neonate compared to the adult. To determine if the cerebellar neurotransmitters, GABA (gamma-amino-butyric acid) and glutamate are involved in the modulation of GAP-43 expression, cultured cerebellar granule cells were exposed to these transmitters. Cultures were treated with glutamate, GABA, or the agonists/antagonists to their receptors in serum-free media for 5-7 days. Analysis of the levels of GAP-43 mRNA by in situ hybridization indicated that a 7-day exposure to GABA (25 and 50 microM) significantly lowered levels of granule cell GAP-43 mRNA. Specific agonists to the GABAA (muscimol) and GABAB (baclofen) receptors produced a decrease similar to that observed for GABA. Results from these studies also indicated that exposure to non-NMDA (CNQX) and NMDA (CPP, MK-801) glutamate receptor antagonists, and a metabotropic receptor glutamate agonist (ACPD), decreased the level of GAP-43 mRNA. The involvement of GABA and glutamate in the modulation of GAP-43 expression was corroborated by Northern hybridization. These studies revealed that a 5-day exposure to GABA decreased the cellular content of GAP-43 mRNA by 21% whereas exposure to glutamate resulted in a 37% increase. Findings from the studies reported here, using an in vitro cerebellar granule cell model, suggest that levels of GAP-43 mRNA, in vivo, are modulated by input from both excitatory glutamatergic mossy fibers and inhibitory GABAergic Golgi interneurons. Thus, modulation of GAP-43 mRNA by these neurotransmitters may influence granule cell maturation during development in the neonate and neuroplasticity in the adult, possibly at the parallel fiber-Purkinje cell synapse.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Animals; Baclofen; Blotting, Northern; Cells, Cultured; Cerebellum; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; GABA Agonists; gamma-Aminobutyric Acid; GAP-43 Protein; Gene Expression Regulation, Developmental; Glial Fibrillary Acidic Protein; Glutamic Acid; Immunohistochemistry; In Situ Hybridization; Microtubule-Associated Proteins; Muscimol; N-Methylaspartate; Neurons; Neuroprotective Agents; Piperazines; Rats; Rats, Sprague-Dawley; RNA, Messenger

Effects of prenatal ethanol exposure on extracellular glutamate accumulation stimulated by glutamate receptor agonists were studied in rat cerebellar granule cell cultures. The prenatal exposure to ethanol was achieved via maternal consumption of a Sustacal liquid diet containing either 5% ethanol or isocaloric sucrose (pair-fed) substituted for ethanol from gestation d 11 until the day of parturition. Neither the basal level of extracellular glutamate nor the increased accumulation of glutamate stimulated by KCl (40 mM) or by ionotropic glutamate receptor agonists, N-methyl-D-aspartate (NMDA) or kainate (KA) (100 microM each), in cells prepared from the ethanol-fed group was significantly different from that in cells prepared from the pair-fed group. Glutamate accumulation stimulated by quisqualate (QA, 100 microM) or by trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (t-ACPD, 250 microM) in the ethanol-fed group was higher than that in the pair-fed group by 116 and 36%, respectively. In the presence of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 100 microM), an ionotropic QA receptor antagonist, the QA-induced accumulation of glutamate in the ethanol-fed group was still higher than that in the pair-fed group. In the presence of MK-801 (5 microM), an antagonist of the NMDA receptor, the enhanced accumulation of glutamate stimulated by either QA or t-ACPD was still observable in the ethanol-fed group as compared to the pair-fed group. Addition of (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG, 500 microM), a selective antagonist of the metabotropic glutamate receptor, abolished the enhanced accumulation of glutamate stimulated by either QA or t-ACPD in the ethanol-fed group. Although immunoblotting of mGluR1 and mGluR2/3 did not show apparent differences between the pair-fed and the ethanol-fed groups, the overall results suggest that the effect of prenatal ethanol exposure was selectively through a pathway mediated by the metabotropic glutamate receptor.

Topics: Alcoholism; Amino Acids; Animals; Cells, Cultured; Cerebellum; Cycloleucine; Dizocilpine Maleate; Ethanol; Female; Glutamic Acid; Kainic Acid; N-Methylaspartate; Neurons; Potassium Chloride; Pregnancy; Pregnancy Complications; Prenatal Exposure Delayed Effects; Quisqualic Acid; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate

Kindling induced by 13 intraperitoneal injections of 40 mg/kg pentylenetetrazole (PTZ) over a period of 4 weeks resulted in a significant long-lasting increase in both the convulsive susceptibility of animals to the convulsant and the density of the specific [3H]-L-glutamate binding sites in the hippocampus. The quisqualate- and kainate-sensitive [3H]-L-glutamate binding sites were increased 24 h after the final PTZ injection, whereas the N-methyl-D-aspartate (NMDA)-sensitive sites had only a tendency to be enhanced. Furthermore, we investigated [3H]-L-glutamate binding on metabotropic receptors and found a significant increase in the hippocampus following PTZ kindling. In addition, in hippocampal tissue of kindled rats (+/-)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (trans-ACPD)-stimulated inositol phosphate formation is increased. It can be concluded that the increase in metabotropic glutamate receptor (mGluR) density may be the expression of a specific enhancement in susceptibility of the glutamatergic systems to this excitatory amino acid developing in the course of PTZ-induced kindling.

Topics: 2-Amino-5-phosphonovalerate; 6-Cyano-7-nitroquinoxaline-2,3-dione; Animals; Brain Chemistry; Convulsants; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Glutamic Acid; Hippocampus; Inositol Phosphates; Kindling, Neurologic; Male; Neuroprotective Agents; Pentylenetetrazole; Radioligand Assay; Rats; Rats, Wistar; Receptors, AMPA; Receptors, Glutamate; Receptors, Kainic Acid; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate; Tritium

The influence of intrahippocampal injections of glutamate receptor agonists on neuropeptide Y (NPY) mRNA expression was investigated in granule cells and interneurons of the rat dentate gyrus. One day after local injection of non-neurodegenerative doses (20 and 70 nmol) of the metabotropic glutamate receptor agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylate [(1S,3R)ACPD], NPY mRNA levels were more than doubled in ipsilateral granule cells and interneurons. Doses of 200 and 400 nmol caused up to 15.9- and 4.6-fold mRNA increases in granule cells and interneurons, respectively. The group I metabotropic glutamate receptor agonist (RS)-3,5-dihydroxyphenylglycine (DHPG; 50 nmol), but not the group III receptor agonist L(+)-2-amino-4-phosphonobutyrate (L-AP4; 20 and 200 nmol) exerted a similar action. The general metabotropic glutamate receptor antagonist (+)-alpha-methyl-4-carboxyphenylglycine (MCPG; 200 nmol), the group I receptor antagonist (S)-4-carboxyphenylglycine (4-CPG; 200 nmol) and the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (1 mg/kg; i.p.) partially blocked the (1S,3R)-1-aminocyclopentane-1,3-dicarboxylate-induced increase in NPY mRNA in granule cells, but not in interneurons. (S)-4-carboxyphenylglycine (200 nmol) by itself increased NPY mRNA levels in ipsilateral interneurons threefold, indicating the activation of phospholipase D coupled receptors. Non-neurodegenerative doses of (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA, 0.3 nmol) caused modest increases in NPY mRNA levels in ipsilateral interneurons, whereas neurodegenerative doses (1-10 nmol) induced markedly increased NPY mRNA levels in granule cells (up to 11-fold) and interneurons (up to threefold). It is suggested that activation of metabotropic glutamate receptors stimulates NPY mRNA expression in granule cells and interneurons in the rat dentate gyrus. Whereas in granule cells NPY mRNA upregulation is preferentially mediated by group I metabotropic glutamate receptors, it may involve ionotropic and metabotropic glutamate receptors in interneurons.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Cycloleucine; Dentate Gyrus; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Glutamic Acid; Hippocampus; Injections; Injections, Intraperitoneal; Male; N-Methylaspartate; Neuropeptide Y; Neuropeptides; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate; RNA, Messenger

Na+-K+-2Cl- cotransporters are important in renal salt reabsorption and in salt secretion by epithelia. They are also essential in maintenance and regulation of ion gradients and cell volume in both epithelial and nonepithelial cells. Expression of Na+-K+-2Cl- cotransporters in brain tissues is high; however, little is known about their function and regulation in neurons. In this study, we examined regulation of the Na+-K+-2Cl- cotransporter by the excitatory neurotransmitter glutamate. The cotransporter activity in human neuroblastoma SH-SY5Y cells was assessed by bumetanide-sensitive K+ influx, and protein expression was evaluated by Western blot analysis. Glutamate was found to induce a dose- and time-dependent stimulation of Na+-K+-2Cl- cotransporter activity in SH-SY5Y cells. Moreover, both the glutamate ionotropic receptor agonist N-methyl-D-aspartic acid (NMDA) and the metabotropic receptor agonist (+/-)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (trans-ACPD) significantly stimulated the cotransport activity in these cells. NMDA-mediated stimulation of the Na+-K+-2Cl- cotransporter was abolished by the selective NMDA-receptor antagonist (+)-MK-801 hydrogen maleate. trans-ACPD-mediated effect on the cotransporter was blocked by the metabotropic receptor antagonist (+)-alpha-methyl-(4-carboxyphenyl)glycine. The results demonstrate that Na+-K+-2Cl- cotransporters in neurons are regulated by activation of both ionotropic and metabotropic glutamate receptors.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Bumetanide; Carrier Proteins; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Agents; Gene Expression Regulation; Glutamic Acid; Humans; Kinetics; N-Methylaspartate; Neuroblastoma; Neurons; Potassium; Receptors, Glutamate; Sodium-Potassium-Chloride Symporters; Tumor Cells, Cultured

We tested the hypothesis that stimulation of metabotropic glutamate receptors (mGluRs) increases nitric oxide (NO) production in the hippocampus in vivo. Microdialysis probes were placed bilaterally into the CA3 region of the hippocampus of adult Sprague-Dawley rats under pentobarbital anesthesia. Probes were perfused for 5 h with artificial cerebrospinal fluid (CSF) containing 3 microM [14C]-L-arginine. Recovery of [14C]-L-citrulline in the effluent was used as a marker of NO production. In nine groups of rats, increases in [14C]-L-citrulline recovery were compared between right- and left-sided probes perfused with various combinations of the selective mGluR agonist, trans-(1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid (ACPD); the mGluR antagonist, (+/-)-alpha-methyl-4-carboxyphenylglycine (MCPG); the NO synthase inhibitor, N-nitro-L-arginine (LNNA); the ryanodine sensitive calcium-release channel inhibitor dantrolene, the non-N-methyl-D-aspartate (NMDA); receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX); the NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d] cyclohepten-5,10-imine (MK-801); and the Na+ channel blocker, tetrodotoxin. Recovery of [14C]-L-citrulline during perfusion with artificial CSF progressively increased to 90 +/- 21 fmol/min (+/-SD) over 5 h. Perfusion in the contralateral hippocampus with 1 mM ACPD augmented [14C]-L-citrulline recovery to 250 +/- 81 fmol/min. Perfusion of 1 mM nitroarginine + ACPD inhibited [14C]-L-citrulline recovery compared to that with ACPD alone. Perfusion with 1 mM MCPG + ACPD attenuated ACPD enhanced [14C]-L-citrulline recovery. Perfusion of 1 mM dantrolene + ACPD inhibited the ACPD-evoked increase in [14C]-L-citrulline recovery. Perfusion of 1 mM MCPG or dantrolene without ACPD did not decrease [14C]-L-citrulline recovery as compared to CSF alone. ACPD-enhanced [14C]-L-citrulline recovery was not attenuated by CNQX, MK-801, or tetrodotoxin (TTX). Using an indirect method of assessing NO production in vivo, these data demonstrate that mGluR stimulation enhances NO production in rat hippocampus. Inhibition with dantrolene suggests that calcium-induced calcium release amplifies the inositol triphosphate-mediated calcium signal associated with mGluR stimulation, thereby resulting in augmented calcium-dependent NO production.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Animals; Benzoates; Biomarkers; Calcium Channels; Citrulline; Cycloleucine; Dantrolene; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glycine; Hippocampus; Male; Microdialysis; Muscle Proteins; N-Methylaspartate; Nerve Tissue Proteins; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate; Ryanodine Receptor Calcium Release Channel; Tetrodotoxin

A dose of N-methyl-D-aspartic acid (NMDA, 50 ng) that induces penile erection and yawning when injected into the paraventricular nucleus of the hypothalamus, increased the concentration of NO2- from 1.10 +/- 0.28 microM to 7.32 +/- 1.12 microM and of NO3 from 4.96 +/- 0.69 microM to 10.5 +/- 1.61 microM in the paraventricular dialysate obtained from male rats by in vivo microdialysis. NO2- concentration was not increased by (+/-)-alpha-(amino)-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA, 100 ng) or by trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (ACPD) (100 ng), which were unable to induce these behavioral responses. N-Methyl-D-aspartic acid effect on NO2- concentration, penile erection and yawning was prevented by dizolcipine (MK-801) (10-100 ng) or by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (20 microg), but not by the oxytocin receptor antagonist [d(CH2)5,Tyr(Me)2,Orn8]vasotocin (100 ng), or by the guanylate cyclase inhibitor methylene blue (20 microg) given in the paraventricular nucleus 15 min before N-methyl-D-aspartic acid or by the dopamine receptor antagonist haloperidol (0.5 mg/kg) given intraperitoneally 30 min before N-methyl-D-aspartic acid. In contrast, the nitric oxide scavenger hemoglobin (20 microg) given in the paraventricular nucleus prevented N-methyl-D-aspartic acid-induced NO2- concentration increase, but was unable to prevent penile erection and yawning. The results suggest that N-methyl-D-aspartic acid induces penile erection and yawning by increasing nitric oxide synthase activity in the paraventricular nucleus of the hypothalamus, possibly in the cell bodies of oxytocinergic neurons projecting to extra-hypothalamic brain areas and mediating these behavioral responses.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Hemoglobins; Male; Methylene Blue; Microdialysis; N-Methylaspartate; Neuroprotective Agents; NG-Nitroarginine Methyl Ester; Nitric Oxide; Oxytocin; Paraventricular Hypothalamic Nucleus; Penile Erection; Rats; Rats, Sprague-Dawley; Yawning

L-Glutamate, NMDA, DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA), and kainate (KA) increased the release of somatostatin-like immunoreactivity (SRIF-LI) from primary cultures of rat hippocampal neurons. In Mg(2+)-containing medium, the maximal effects (reached at approximately 100 microM) amounted to 737% (KA), 722% (glutamate), 488% (NMDA), and 374% (AMPA); the apparent affinities were 22 microM (AMPA), 39 microM (glutamate), 41 microM (KA), and 70 microM (NMDA). The metabotropic receptor agonist trans-1-aminocyclopentane-1,3-dicarboxylate did not affect SRIF-LI release. The release evoked by glutamate (100 microM) was abolished by 10 microM dizocilpine (MK-801) plus 30 microM 1-aminophenyl-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI 52466). Moreover, the maximal effect of glutamate was mimicked by a mixture of NMDA+AMPA. The release elicited by NMDA was sensitive to MK-801 but insensitive to GYKI 52466. The AMPA- and KA-evoked releases were blocked by 6,7-dinitroquinoxaline-2,3-dione (DNQX) or by GYKI 52466 but were insensitive to MK-801. The release of SRIF-LI elicited by all four agonists was Ca(2+) dependent, whereas only the NMDA-evoked release was prevented by tetrodotoxin. Removal of Mg2+ caused increase of basal SRIF-LI release, an effect abolished by MK-801. Thus, glutamate can stimulate somatostatin release through ionotropic NMDA and AMPA/KA receptors. Receptors of the KA type (AMPA insensitive) or metabotropic receptors appear not to be involved.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Anti-Anxiety Agents; Benzodiazepines; Calcium; Cells, Cultured; Cycloleucine; Dizocilpine Maleate; Drug Synergism; Glutamic Acid; Hippocampus; Kainic Acid; N-Methylaspartate; Pyramidal Cells; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Somatostatin; Tetrodotoxin

The microinjection of L-glutamate (1-6 nmol/rat) and N-methyl-D-aspartate (NMDA 1-10 nmol/rat), ionotropic glutamate receptor (iGluR) agonists, into the nucleus raphe obscurus caused a concentration -dependent increase of arterial blood pressure. In contrast, (+/-)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (t-ACPD, 14-42 nmol/rat), a metabotropic glutamate receptor (mGluRs) agonist, caused a concentration-dependent decrease in blood pressure. Pretreatment with D,L-2-amino-phosphono valeric acid (2-APV, 5 nmol/rat) a selective NMDA iGluR antagonist, and (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,b] cyclohepten-5,10-imine hydrogen maleate (MK801, 0.9 nmol/rat), a noncompetitive NMDA iGluR antagonist, blocked both the glutamate and NMDA pressor responses, while pretreatment with (+)-alpha-methyl-4-carboxyphenylglycine (MCPG, 0.05 nmol/rat), a mGluR1 antagonist, increased the glutamate-induced pressor effects and blocked the fall in blood pressure induced by t-ACPD. 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX, 0.4 nmol/rat) a non-NMDA iGluR antagonist, did not affected the glutamate-induced hypertension. These observations indicate opposing roles for ionotropic and metabotropic receptors in the glutamate-induced blood pressure changes elicited from the nucleus raphe obscurus. Moreover, we suggest that the glutamate-induced hypertension may be due to the activation of NMDA ionotropic receptor subtypes and the metabotropic receptors may influence this activation through a reduction of excitability at level of synapses.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Analysis of Variance; Animals; Benzoates; Blood Pressure; Cycloleucine; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glutamic Acid; Glycine; Hypertension; Male; Microinjections; N-Methylaspartate; Neurotoxins; Raphe Nuclei; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate; Structure-Activity Relationship; Valine

1. The abilities of the four diastereoisomers of 1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) to stimulate, and the metabotropic glutamate receptor (mGluR) antagonist (+/-)-alpha-methylcarboxyphenylglycine (MCPG) to inhibit, phosphoinositide turnover in neonatal rat cerebral cortex have been studied. Two indices of phosphoinositide cycle activity were assessed; inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) mass accumulation, and total inositol phosphate [3H]-InsPx accumulation (in the presence of Li+) in myo-[3H]-inositol prelabelled slices. 2. The diastereoisomers of ACPD stimulated each response with a rank order of potency of 1S, 3R > 1R, 3R > 1S, 3S >> 1R, 3S. The response to 1R, 3R-ACPD was largely prevented by pre-addition of the NMDA-receptor antagonist, MK-801, or omission of extracellular Ca2+, suggesting that this isomer acts indirectly on phosphoinositide responses through activation of NMDA-type ionotropic glutamate receptors. In contrast, the responses to 1S, 3R- and 1S, 3S-ACPD were unaffected by prior addition of MK-801, but were blocked by MCPG. 3. The concentration of 1S, 3R-ACPD required to half-maximally stimulate the Ins(1,4,5)P3 response (-log EC50 (M), -4.09 +/- 0.10) was significantly higher than that required to exert a similar effect on [3H]-InsPx accumulation (-log EC50 (M), -4.87 +/- 0.07; P < 0.01; n = 4). A similar marked 8-9 fold discrepancy between these two values was observed for the 1S, 3S isomer, which elicited similar maximal responses to those caused by 1S, 3R-ACPD. 4. Significant differences were also observed with respect to the ability of (+/-)-MCPG (1 mM) to cause a rightward shift in the concentration-response relationships for 1S, 3R-ACPD-stimulated Ins(1,4,5)P3 (5.59 +/- 0.24 fold shift) and [3H]-InsPx (3.04 +/- 0.34 fold shift; P < 0.01; n = 4) responses, giving rise to Kd values of 218 and 490 microM for (+/-)-MCPG antagonism of the respective responses. 5. The potency difference between the 1S, 3R-ACPD-stimulated Ins(1,4,5)P3 and [3H]-InsPx responses was reduced when experiments were performed in nominally calcium-free medium ([Ca2+]e = 2 - 5 microM) and EC50 values were almost identical when extracellular calcium was reduced further by EGTA addition ([Ca2+]e < or = 100 nM). Similarly, the Kd value for (+/-)-MCPG antagonism of the 1S, 3R-ACPD-stimulated [3H]-InsPx response decreased under [Ca2+]e-free conditions, approaching those obtained for the 1S, 3R-ACPD-stimulated Ins(1,4,5)P3 response in the presence

Topics: Animals; Benzoates; Cerebral Cortex; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Female; Glycine; Inositol 1,4,5-Trisphosphate; Male; Molecular Conformation; Phosphatidylinositols; Rats; Rats, Wistar; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate; Stereoisomerism

Developmental changes in glutamate receptor agonist-produced enhancement of 4-beta-[3H]phorbol-12,13-dibutyrate binding ([3H]-PDBu binding), indicative of an intracellular translocation of protein kinase C (PKC), were investigated in cerebellar granule cells. Our observations demonstrate that the magnitude of glutamate-, NMDA-, and kainate-produced enhancement of PKC translocation was dramatically decreased between 2 and 12 DIV, whereas there was only a minor reduction in the corresponding response caused by the non-NMDA receptor agonist, AMPA. The maximally enhanced stimulation of PKC translocation caused by glutamate and NMDA was significantly reduced already at 4 DIV, whereas a significant reduction of the kainate-induced enhancement of [3H]PDBu binding was not observed until 8 DIV. Glutamate- and NMDA-induced responses were effectively blocked by the specific NMDA receptor antagonists MK-801 (1 microM) and APV (100 microM) as well as by the addition of Mg2+ into assay media. In contrast, the non-NMDA receptor antagonist, CNQX (10 microM), effectively blocked the kainate-induced enhancement of [3H]PDBu binding, but had no effect on the NMDA- and glutamate-induced stimulation of PKC translocation. The metabotropic glutamate receptor agonist, ACPD (up to 250 microM), had no effect on the translocation of PKC. Taken together, our data support the working hypothesis that the rapidly occurring changes in the glutamate receptor agonist-produced translocation of PKC are most likely due to a differential maturation of glutamate ionotropic receptor subtypes and/or to development-dependent alterations in mechanisms responsible for the coupling between the glutamate receptor subtypes and the activation of PKC translocation in cerebellar granule neurons.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Binding, Competitive; Biological Transport; Carcinogens; Cells, Cultured; Cerebellum; Cycloleucine; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glutamic Acid; Kainic Acid; Magnesium; N-Methylaspartate; Neurotoxins; Phorbol 12,13-Dibutyrate; Protein Kinase C; Rats; Rats, Sprague-Dawley; Receptors, Glutamate; Tritium

The purpose of this study was to examine the motor effects of (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD), an agonist at metabotropic glutamate receptors, its interaction with dizocilpine (MK-801), a NMDA receptor antagonist, and with D,L-amphetamine, an indirect dopamine receptor agonist. 1S,3R-ACPD (20, 30, 40, 80 micrograms) evoked prominent locomotor and exploratory deficits in an open-field hole-board test and a moderate akinesia and rigidity in a catalepsy test (30, 40, 80 micrograms). MK-801 (0.08, 0.16, 0.32 mg/kg i.p.) as well as D,L-amphetamine (1.0, 2.0, 3.0 mg/kg i.p.) potently reversed 1S,3R-ACPD-induced (80 micrograms) catalepsy. MK-801 and D,L-amphetamine, administered alone, induced motor stimulation. 1S,3R-ACPD (80 micrograms) reversed the effects of the two lower doses of MK-801. 1S,3R-ACPD reversed D,L-amphetamine-induced motor stimulation to a minor extent than that of MK-801. Thus motor deficits induced by 1S,3R-ACPD were reversed by both, NMDA receptor blockade and dopamine receptor activation. 1S,3R-ACPD reversed motor stimulation, induced by NMDA receptor blockade and, however less pronounced, that by dopamine receptor activation.

Topics: Amphetamine; Animals; Catalepsy; Cycloleucine; Dizocilpine Maleate; Dose-Response Relationship, Drug; Locomotion; Male; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Reaction Time

The effect of excitatory amino acids (EAA) on phosphatidylinositol (PI) turnover in human cerebral cortical slices was investigated. Trans-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) increased inositol phosphate (IP) formation in the 1-1000 microM range. Quisqualic acid (QA) was maximally effective at 10-100 microM, showing an inverse correlation between concentration and effect in the 100-1000 microM range. The glutamate metabotropic receptor antagonist 2-amino-3-phosphonopropionic acid (AP3), the ionotropic non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and the NMDA channel blocker dizolcipine (MK-801) failed to prevent the PI response to ACPD (1000 microM). However, CNQX (100 microM) modified the concentration-response curve of QA reducing the effect of QA 10 microM by approx. 50% and enhancing that of QA 1000 microM by 2-fold. In addition, CNQX (100 microM) together with MK-801 (100 microM) unmasked the ability of L-glutamate (L-GLU) 3000 microM to stimulate PI turnover. The effect of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) on the EAA-induced PI turnover was also studied. AMPA (0.1-1 microM) potentiated the response to submaximal (30 microM) ACPD and (1 microM) QA concentrations. However, higher AMPA concentrations (10 microM) failed to synergize with ACPD 30 microM and, in addition, inhibited the PI turnover maximally stimulated by QA 10 microM. These results further support the presence of the glutamate metabotropic receptor in the human neocortex. In addition, they show the occurrence of a concentration-related dual interaction between AMPA and glutamate metabotropic receptor activation in the IP formation in this brain area.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Adolescent; Adult; Aged; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Calcimycin; Cerebral Cortex; Child; Cycloleucine; Dizocilpine Maleate; Female; Glutamic Acid; Humans; Male; Middle Aged; N-Methylaspartate; Phosphatidylinositols; Quisqualic Acid; Receptors, AMPA; Receptors, Metabotropic Glutamate; Signal Transduction; Tetrodotoxin

The mobilization of inositol triphosphate ip3 by N-methyl D-aspartate (NMDA) and kainate, two excitatory amino acid EAA receptor agonists, was studied in cultured chick retina cells as a function of culture differentiation. Kainate (EC50 = 30 microM) stimulated from 6 to 9-fold the production of [3H]ip3 between E8C3 (embryonic day 8 plus 3 days in vitro) and E8C13. The kainate response was blocked by CNQX (100 microM) by more than 80% until stage E8C9. MK-801, however, was totally ineffective in preventing the kainate induced ip3 generation. [3H]ip3 production evoked by NMDA was increased 4-fold above basal levels at E8C3. As cultures differentiated, [3H]ip3 production promoted by NMDA decreased to 2.5-fold at E8C6 to 1.6-fold the basal levels in cultures at later stages of differentiation. The removal of Mg2+ from the incubating medium at E8C3 increased the NMDA mediated [3H]ip3 production by 80%. However, at more differentiated stages of the cultures, when cells were not responsive to NMDA, removal of Mg2+ plus the addition of 1 mM glycine did not change the pattern of the response. Although NMDA mediated ip3 production is almost absent in more differentiated cultures, NMDA is able to induce [3H]GABA release in E8C3 and E8C13 cultures with characteristics that reflect typical NMDA receptor activation: it is highly potentiated by the absence of Mg2+ and by the presence of glycine. The NMDA induced production of [3H]ip3 at E8C3 was entirely blocked by MK-801 (100 microM) and APV (100 microM) but not by CNQX.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Animals; Cells, Cultured; Chick Embryo; Cycloleucine; Dizocilpine Maleate; gamma-Aminobutyric Acid; Inositol 1,4,5-Trisphosphate; Kainic Acid; N-Methylaspartate; Neurotoxins; Receptors, N-Methyl-D-Aspartate; Retina; Time Factors

In vivo microdialysis was used to assess the effects of electrical stimulation of the prefrontal cortex (PFC) on dopamine (DA) release in the nucleus accumbens (NAC) of awake, unrestrained rats. The PFC was stimulated bilaterally for 20 min at parameters previously shown to support intracranial self-stimulation in this structure. Stimulation at 50 microA evoked a 38% increase in DA release while 100 microA produced a 69% increase. Thus, phasic activation of the PFC increases DA release in the NAC. Additional experiments were performed to establish whether glutamate receptors in the NAC mediated these effects. The noncompetitive NMDA antagonist dizocilpine maleate (MK-801) and the broad spectrum competitive antagonist kynurenic acid were each applied locally to the NAC via reverse dialysis alone or in combination with electrical stimulation of the PFC (100 microA). Both MK-801 (10 microM) and kynurenic acid (5 mM) increased DA release when administered alone. When a "subthreshold" concentration (i.e., the highest concentration employed that did not itself increase DA release) of either compound was administered together with PFC stimulation, neither kynurenic acid (1 mM) nor MK-801 (1 microM) attenuated the effect of stimulation on DA release, thereby indicating that this effect is not mediated by ionotropic glutamate receptors located within the NAC. To examine the possible role of metabotropic glutamate receptors in regulating DA release, the metabotropic glutamate agonist trans(1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) was employed. When applied locally to the NAC, ACPD had a dose-dependent effect on DA release with a high concentration (1 mM) causing an increase and a lower concentration (100 microM) causing a small decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Cycloleucine; Dizocilpine Maleate; Dopamine; Dose-Response Relationship, Drug; Electric Stimulation; Excitatory Amino Acid Antagonists; Kinetics; Kynurenic Acid; Male; Microdialysis; Nucleus Accumbens; Prefrontal Cortex; Rats; Rats, Wistar; Tetrodotoxin; Time Factors

We found in cultured glioma (C6BU-1) cells that excitatory amino acids (EAAs) such as glutamate, N-methyl-D-aspartate (NMDA), aspartate, and metabotropic glutamate receptor agonist trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylate caused an increase in the inositol 1,4,5-trisphosphate formation and the intracellular Ca2+ concentration ([Ca2+]i) in the absence of extracellular Mg2+ and Ca2+. Pertussis toxin treatment abolished this glutamate-induced [Ca2+]i increase. Various antagonists against NMDA receptor-ion channel complex, such as Mg2+, D-2-amino-5-phosphonovalerate (D-APV), HA-966, and MK-801, also inhibited the increase in [Ca2+]i induced by glutamate. These results indicate that these metabotropic EAA receptors coupled to pertussis toxin-susceptible GTP-binding protein and phospholipase C system in C6BU-1 glioma cells have the pharmacological properties of NMDA receptor-ion channel complexes. We also found that in the presence of Mg2+ these metabotropic receptors resemble the NMDA receptor-ion channel complex interacted with 5-hydroxytryptamine2 (5-HT2) receptor signaling. EAAs inhibited 5-HT2 receptor-mediated intracellular Ca2+ mobilization and inositol 1,4,5-trisphosphate formation in a concentration-dependent manner. The inhibitory effect of glutamate was reversed by various NMDA receptor antagonists (D-APV, MK-801, phencyclidine, and HA-966), but L-APV failed to block the inhibitory effect of glutamate. The same result was observed in the absence of extracellular Ca2+. In addition, this inhibitory effect on 5-HT2 receptor-mediated signal transduction was abolished by treatment of C6BU-1 cells with pertussis toxin, whereas 5-HT2 receptor-mediated [Ca2+]i increase was not abolished by pertussis toxin treatment. We can, therefore, conclude that the inhibitory effect of glutamate is not a result of the influx of Ca2+ through the ion channel and that it operates via metabotropic glutamate receptors, having NMDA receptor-ion channel complex-like properties and being coupled with pertussis toxin-sensitive GTP-binding protein and phospholipase C.

Topics: 2-Amino-5-phosphonovalerate; Animals; Aspartic Acid; Calcium; Cell Line; Cycloleucine; Dizocilpine Maleate; Glioma; Glutamic Acid; Inositol 1,4,5-Trisphosphate; Ion Channels; Kainic Acid; Kinetics; Magnesium Chloride; N-Methylaspartate; Neurotoxins; Pyrrolidinones; Rats; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate; Receptors, Serotonin; Signal Transduction; Tumor Cells, Cultured

This study examined the effects of glutamate receptor agonists on the release of neuropeptide FF-like immunoreactivity from rat spinal dorsal half slices. Glutamate (10 microM) only induced release in Mg(2+)-free medium enriched with glycine (1 microM) and with slight depolarization (15 mM K+). This effect was abolished by the NMDA receptor antagonist, 2-amino-5-phosphonovalerate (100 microM), suggesting major participation of NMDA receptors. The quisqualate and metabotropic receptor agonists, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) and trans-1-hydroxy-5-methylisoxazole-4-propionate (t-ACPD) respectively, had no effect at 10 microM. In contrast, NMDA dose dependently stimulated neuropeptide FF release, even in the presence of the Na+ channel blocker, tetrodotoxin (1 microM), suggesting that NMDA receptors involved in the release of neuropeptide FF are mainly located on nerve terminals. The NMDA receptor antagonists, 2-amino-5-phosphonovalerate or (+)-5-methyl-10-11-dihydro-5H-dibenzo [a,d]cyclohepten-5,10-imine (MK-801) (100 microM), blocked the 10 microM NMDA effect. Furthermore, neuropeptide FF-like material inhibited binding of [125I]Y8Fa, a radioiodinated analog of neuropeptide FF, to spinal membranes, suggesting physiological relevance of NMDA-induced release. Taken together, these results suggest a relationship between neuropeptide FF and NMDA receptors in the spinal cord.

Topics: 2-Amino-5-phosphonovalerate; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Cycloleucine; Dizocilpine Maleate; Glutamic Acid; In Vitro Techniques; Iodine Radioisotopes; Male; Membranes; N-Methylaspartate; Neuropeptides; Neurotoxins; Oligopeptides; Radioimmunoassay; Radioligand Assay; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Spinal Cord

1. The effect of NMDA-receptor stimulation on phosphoinositide signalling in response to the metabotropic glutamate receptor agonist 1-aminocyclopentane-1S,3R-dicarboxylic acid (1S,3R-ACPD) has been examined in neonatal rat cerebral cortex slices. 2. Total [3H]-inositol phosphate ([3H]-InsPx) accumulation, in the presence of 5 mM LiCl, in [3H]-inositol pre-labelled slices was concentration-dependently increased by 1S,3R-ACPD (EC50 16.6 microM) and, at a maximally effective concentration, 1S,3R-ACPD (300 microM) increased [3H]-InsPx accumulation by 12.8 fold over basal values. 3. [3H]-InsPx accumulation stimulated by 1S,1R-ACPD was enhanced by low concentrations of NMDA (3-30 microM), but not by higher concentrations (> 30 microM). [3H]-InsPx accumulations stimulated by 1S,3R-ACPD in the absence or presence of 10 microM NMDA were linear with time, at least over the 15 min period examined; however, in the presence of 100 microM NMDA the initial enhancement of 1S,3R-ACPD-stimulated phosphoinositide hydrolysis progressively decreased with time. 4. In the presence of a maximal enhancing concentration of NMDA (10 microM), the response to 1S,3R-ACPD (300 microM) was increased 1.9 fold and the EC50 for agonist-stimulated [3H]-InsPx accumulation decreased about 4 fold. The enhanced response to the metabotropic agonist was concentration-dependently inhibited by competitive and uncompetitive antagonists of NMDA-receptor activation. 5. 1S,3R-ACPD also stimulated inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) mass accumulation with an initial peak response (5-6 fold over basal) at 15 s decaying to a smaller (2 fold), but persistent elevated accumulation (1-10 min). 6. Co-addition of 10 or 100 MicroM NMDA enhanced the initial peak Ins(1,4,5)P3 response to 1S,3RACPD.However, the enhancing effect was only maintained over 10 min in the presence of 1O Micro MNMDA, whilst in contrast, 100 MicroM NMDA ceased to cause a significant enhancement of the metabotropic response by 5 min and completely suppressed lS,3R-ACPD-stimulated Ins(1,4,5)P3 accumulation at 10 min.7. Both basal and 1S,3R-ACPD-stimulated Ins(1,4,5)P3 accumulations were reduced when slices were incubated in nominally Ca2"-free medium. Under these conditions only a concentration-dependent enhancement of the response was observed (EC50 for NMDA facilitation of lS,3R-ACPD-stimulated Ins(1,4,5)P3 accumulation of 32 MicroM).8. These experiments have revealed that at low concentrations, NMDA can dramatically potentiate1S

Topics: 2-Amino-5-phosphonovalerate; Animals; Animals, Newborn; Calcium; Cerebral Cortex; Cycloleucine; Dizocilpine Maleate; Female; Hydrolysis; In Vitro Techniques; Inositol 1,4,5-Trisphosphate; Male; N-Methylaspartate; Neurotoxins; Phosphatidylinositols; Rats; Rats, Wistar; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate

Two antagonists of metabotropic glutamate receptors, L-AP4 and MCPG, were tested in a one-trial passive avoidance task in the chick to investigate whether these receptor subtypes play a role in learning and memory. Drugs were injected i.c. L-AP4 produced amnestic effects when injected pre- or post-training. When injected pretraining, amnesia onset was observed after 1 h post-training. D-AP4 had no effect on memory formation. MCPG in comparison had no effect when injected post-training. When injected pretraining, the onset of amnesia was dose-dependent, ranging from 2 to 1 h post-training. When injecting MCPG along with the mGluR agonist ACPD, no amnestic effect was visible. ACPD on its own had no effect at the dose used.

Topics: Aminobutyrates; Amnesia; Animals; Avoidance Learning; Benzoates; Chickens; Cycloleucine; Cyclopropanes; Dizocilpine Maleate; Dose-Response Relationship, Drug; Female; Glycine; Injections, Intraperitoneal; Injections, Intraventricular; Male; Motor Activity; Phosphoserine; Receptors, Metabotropic Glutamate

Intracerebroventricular (i.c.v.) infusion in mice of the selective metabotropic excitatory amino acid receptor agonist 1S,3R-1- aminocyclopentane-1,3-dicarboxylate (1S,3R-ACPD) (0.6-575 nmol/min) dose dependently induced face washing and scratching. In contrast, the subtype-specific ionotropic excitatory amino acid receptor agonists N-methyl-D-aspartate (NMDA), kainate and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) (0.3-3.0 nmol/min) dose dependently induced clonic convulsions. I.c.v. infusion of the non-selective metabotropic receptor agonists ibotenate (6 nmol/min) or quisqualate (30 nmol/min) induced clonic convulsions. However, when ionotropic receptors were blocked with (+)-5-methyl-10,11-dihydro-5H-dibenzo-(a,d)cyclohepten-5,10-imine maleate (MK-801, dizoclipine) (3 nmol/min) or 2,3-dihydroxy-6-nitro-7- sulfamoyl-benzo(f)-quinoxaline (NBQX) (9 nmol/min), respectively, face washing and scratching behavior emerged. Neither MK-801 or NBQX (ED50 value > 100 nmol/min), nor the putative metabotropic receptor antagonist L-amino-3-phosphoro-propionic acid (L-AP3) (> 176 nmol/min); nor the dopamine receptor antagonists SCH 23390 (> 74 nmol/min), metoclopramide (> 89 nmol/min) and haloperidol (> 27 nmol/min) antagonized 1S,3R-ACPD-induced scratching (144 nmol/min). These results suggest that the behavioral consequences of i.c.v. infusion of 1S,3R-ACPD in mice reflect a selective activation of metabotropic receptors that differs from the behavioral changes observed with i.c.v. infusion of ionotropic receptor agonists.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Behavior, Animal; Cycloleucine; Dizocilpine Maleate; Dose-Response Relationship, Drug; Ibotenic Acid; Kainic Acid; Male; Mice; N-Methylaspartate; Quinoxalines; Quisqualic Acid; Receptors, Glutamate; Seizures

The role of metabotropic excitatory amino acid receptors in seizures and brain injury was examined using the selective metabotropic agonist 1S,3R-ACPD [(1S,3R)-1-aminocyclopentane-1-3-dicarboxylic acid] in 7-d-old neonatal rats. Systemic administration of 1S,3R-ACPD produced dose-dependent convulsions (ED50 = 16 mg/kg, i.p.) that were stereoselective for the active metabotropic ACPD isomer, since 1R,3S-ACPD was less potent (ED50 = 93 mg/kg, i.p.). 1S,3R-ACPD-induced seizures were antagonized by systemic administration of dantrolene, an inhibitor of intracellular calcium mobilization, but not by the ionotropic glutamate antagonists MK-801 or GYKI-52466. As indexed by hemispheric brain weight differences 5 d postinjection, unilateral intrastriatal injection of 1S,3R-ACPD (0.1-2.0 mumol/microliters), but not 1R,3S-ACPD, produced dose-dependent brain injury (maximal effect of 3.4 +/- 0.5% damage). 1S,3R-ACPD brain injury occurred in the absence of prominent behavioral convulsions. Histologic and ultrastructural examination of 1S,3R-ACPD-injected rat brains revealed swelling and degeneration of select neurons at 4 hr postinjection, but little evidence of injured neurons 5 d later. 1S,3R-ACPD-mediated brain injury was not attenuated by systemic administration of the NMDA antagonist MK-801 or the AMPA antagonist GYKI-52466. However, cointrastriatal injection of dantrolene reduced the severity of 1S,3R-ACPD injury by 88 +/- 7%. These studies indicate that seizures and neuronal injury can be elicited by the selective activation of metabotropic glutamate receptors in perinatal rats, and these effects of 1S,3R-ACPD involve the mobilization of intracellular calcium stores.

Topics: Animals; Animals, Newborn; Anti-Anxiety Agents; Benzodiazepines; Brain Injuries; Cell Nucleus; Corpus Striatum; Cycloleucine; Dantrolene; Dizocilpine Maleate; Female; Hippocampus; Male; Microscopy, Electron; Neurons; Neurotoxins; Rats; Rats, Sprague-Dawley; Receptors, Glutamate; Seizures; Stereotaxic Techniques

beta-N-methylamino-L-alanine (L-BMAA) is an excitotoxin whose neurodegenerative effects are associated with its agonist properties at the N-methyl-D-aspartate (NMDA) receptor. We measured the effects of L-BMAA on inositol phosphate (InsP) formation in primary cultured striatal neurons. This culture is almost devoid of glial cells and the pharmacology of glutamate receptors is well-defined. This allowed us to show that L-BMAA induced InsP formation via a direct action at the glutamate metabotropic (Qp) receptors coupled to InsP formation. We demonstrated that L-BMAA is a full-agonist of the Qp receptor, but with a low potency. Therefore, the neurotoxic properties of L-BMAA might implicate the activation of the Qp receptor in association with the NMDA receptor.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Amino Acids, Diamino; Animals; Carbachol; Cells, Cultured; Corpus Striatum; Cyanobacteria Toxins; Cycloleucine; Dizocilpine Maleate; Embryo, Mammalian; Glutamates; Inositol; Inositol Phosphates; Kinetics; Mice; Neurons; Neurotoxins; Phorbol 12,13-Dibutyrate; Quinoxalines; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

The complex modulation of cytoplasmic free calcium concentration ([Ca2+]c) in primary cultures of cerebellar granule cells in response to glutamate receptor agonists has been the subject of several contradictory reports. We here show that 3 components of the [Ca2+]c response can be distinguished: (1) Ca2+ entry through voltage-dependent Ca2+ channels, following KCl- or receptor-evoked depolarization, (2) Ca2+ entry through NMDA receptor channels, and (3) liberation of internal Ca2+ via a metabolotropic receptor. Depolarization with KCl induced a transient [Ca2+]c response (subject to voltage inactivation) decaying to a sustained plateau (largely inhibited by nifedipine). The NMDA response was potentiated by glycine, totally inhibited by (+)5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801), and blocked by Mg2+ in a voltage-sensitive manner. Polarized cells displayed small responses to quisqualate (QA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA). Depolarization enhanced a transient response to QA, but not to AMPA. Trans-1-amino-1,3-cyclopentanedicarboxylic acid (trans-ACPD), a selective agonist for the metabolotropic glutamate receptor, caused a transient elevation of [Ca2+]c, which was blocked by prior exposure to QA but not AMPA. The prolonged [Ca2+]c response to kainate (KA) can be resolved into 2 major components: an indirect NMDA receptor-mediated response due to released glutamate and a nifedipine-sensitive component consistent with depolarization-mediated entry via Ca2+ channels. 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX), QA at greater than 10 microM, and AMPA (but not trans-ACPD) reversed the KA response, consistent with an inactivation of the KA receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Calcium; Calcium Channels; Cell Membrane; Cells, Cultured; Cerebellum; Cycloleucine; Dizocilpine Maleate; Ibotenic Acid; Kainic Acid; Magnesium; Membrane Potentials; Neurons; Quinoxalines; Quisqualic Acid; Rats; Rats, Inbred Strains; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter