cgp-39653 and 5-7-dichlorokynurenic-acid

Quinolinic acid (QUIN) displaced binding of agonist and antagonist ligands for the N-methyl-D-aspartate (NMDA) receptor in rat brain synaptic membranes. Both QUIN and glutamic acid (GLU) potentiated binding of [3H]dizocilpine (MK-801) in the presence of glycine (GLY) alone, whereas the potentiation by QUIN was in a bell-shaped fashion in contrast to that by GLU. However, further addition of spermidine (SPD) induced bell-shaped potentiation by GLU as well as QUIN. The potentiation by QUIN was markedly deteriorated by the further addition of FeCl2 irrespective of the presence of GLY and SPD added. These results suggest that QUIN may potentiate [3H]MK-801 binding to the open NMDA channel in rat brain synaptic membranes through a mechanism different from that underlying the potentiation by GLU.

Topics: 2-Amino-5-phosphonovalerate; Allosteric Regulation; Animals; Binding Sites; Brain; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Ferrous Compounds; Glutamic Acid; Glycine; Inhibitory Concentration 50; Kynurenic Acid; Male; Quinolinic Acid; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Spermidine; Synaptic Membranes

We used a partial agonist model to understand further the allosteric modulation of D,L-(E)-2-amino4-propyl-5-phosphono-3-pentenoic acid ([3H]CGP-39653) binding by glycine, 1-hydroxy-3-amino-2-pyrrolidone (HA-966) and 5,7-dichlorokynurenic acid at the NMDA receptor. Binding of [3H]CGP-39653 was investigated in homogenates of cortex, hippocampus and cerebellum of adult rat. Glycine, HA-966 and 5,7-dichlorokynurenic acid maximally decreased the binding of 10 nM of [3H]CGP-39653 by approximately 50, 40 and 22%, respectively. Glycine, HA-966 and 5,7-dichlorokynurenic acid reduced [3H]CGP-39653 binding with IC50 values of 0.31, 11 and 0.044 microM, respectively. The decrease in [3H]CGP-39653 binding was due to a reduced affinity (Kd) and number of binding sites (Bmax) by all three drugs at concentrations where approximately maximum inhibition was observed. Glycine, HA-966 and 5,7-dichlorokynurenic acid lowered the Bmax by approximately 29, 16 and 10%, respectively, whereas the Kd values were increased by approximately 84, 44 and 32%, respectively, in cortex and hippocampus. There was no change in the binding of [3H]CGP-39653 in the cerebellum. The model used revealed that neither 5,7-dichlorokynurenic acid nor HA-966 had partial agonist characteristics in respect with the allosteric modulation of [3H]CGP-39653 binding. Furthermore, the results showed that brain regions have different pharmacological profiles which may depend on the NMDA receptor subunit composition.

Topics: 2-Amino-5-phosphonovalerate; Allosteric Regulation; Animals; Cerebellum; Cerebral Cortex; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glycine; Hippocampus; In Vitro Techniques; Kynurenic Acid; Male; Models, Biological; Protein Binding; Pyrrolidinones; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

Topics: 2-Amino-5-phosphonovalerate; Animals; Binding, Competitive; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; gamma-Aminobutyric Acid; In Vitro Techniques; Kainic Acid; Kynurenic Acid; Male; Piperidines; Radioligand Assay; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate

A stoichiometric analysis of N-methyl-D-aspartate (NMDA) receptor binding was conducted using [3H]dizocilpine, [3H]dichlorokynurenic acid and [3H]CGP39653, and membranes from various brain regions of rats. The ratio of the density of [3H]CGP39653 binding to [3H]dizocilpine binding was > 1 in frontal cortex and hippocampus, approximately 1 in striatum and spinal cord and < 1 in cerebellum. When [3H]dichlorokynurenic acid binding was compared with [3H]dizocilpine binding, the ratios were > 1 in frontal cortex, hippocampus and striatum, 3-4 in cerebellum, and approximately 2 in spinal cord. These observations suggest that a single channel complex may have more than one binding site for NMDA and/or glycine and that the stoichiometry between the binding domains of the NMDA receptor varies regionally.

Topics: 2-Amino-5-phosphonovalerate; Animals; Brain; Brain Chemistry; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; In Vitro Techniques; Kinetics; Kynurenic Acid; Male; Nerve Tissue Proteins; Radioligand Assay; Rats; Rats, Inbred F344; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate

Chronic antidepressant treatment results in adaptation of the NMDA receptor complex in the rodent cortex. This adaptation consists of a reduction in the potency of glycine to displace [3H]5,7-dichlorokynurenic acid from strychnine-insensitive glycine receptors and a reduction in high affinity, glycine-displaceable [3H]CGP-39653 binding to glutamate receptors. We hypothesized that dysfunction of NMDA receptors might occur in frontal cortices from human suicide victims. We now report that the proportion of high affinity, glycine displaceable [3H]CGP-39653 binding to glutamate receptors is reduced from 45 +/- 5% in controls to 27 +/- 6% in age- and post-mortem interval-matched suicide victims. In contrast, neither the potency nor the maximum efficacy of glycine to inhibit [3H]CGP-39653 binding is altered in the frontal cortex of suicide victims compared to controls. Moreover, neither the potency of glycine to inhibit [3H]5,7-dichlorokynurenic acid binding to the strychnine-insensitive glycine receptor nor the specific binding of [3H]5,7-dichlorokynurenic acid binding differed in suicide victims compared to controls. Likewise, neither basal nor glycine- or glutamate enhanced non-equilibrium binding of [3H]dizocilpine was altered in the frontal cortex of suicide victims compared to controls. These data represent the first demonstration supporting the hypothesis that glutamatergic dysfunction is involved in psychopathology underlying suicide and, potentially in human major depression.

Topics: 2-Amino-5-phosphonovalerate; Adult; Dizocilpine Maleate; Female; Frontal Lobe; Humans; In Vitro Techniques; Kynurenic Acid; Male; Middle Aged; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate; Suicide

The ligand preferences of recombinant NR1 homomeric and NR1-NR2 heteromeric NMDA receptors were examined by homogenate binding assay. The binding affinities for most ligands were similar to those reported for native NMDA receptors. The order of affinity for [3H]glutamate was NR1-NR2B > NR1-NR2A approximately NR1-NR2D > NR1-NR2C > NR1. NMDA had approximately equal affinity for all heteromeric types (Ki approximately 5 microM), but the competitive antagonists CGS 19755 (cis-4-(phosphonomethyl)piperidine-2-carboxylic acid) and CGP 39653 (D,L-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic acid) displayed the affinity order NR1-NR2A > NR1-NR2B > NR1-NR2D > NR1-NR2C. Binding of [3H]CGP 39653 could only be detected at the NR1-NR2A receptor type (Kd approximately 6 nM). The glycine site antagonist [3H]5,7-dichlorokynurenate bound with good affinity to all recombinant receptors (Kd approximately 50-100 nM), while glycine exhibited an affinity order of NR1-NR2C >> NR1 = NR1-NR2B = NR1-NR2D > NR1-NR2A. The channel-site ligand [3H]MK 801 ((+)-5-methyl-10,11-dihydro-5H- dibenzo[a,d]cyclo-hepten-5,10-imine hydrogen maleate) showed the affinity ranking NR1-NR2A = NR1-NR2B >> NR1 > NR1-NR2C = NR1-NR2D. Thus the ligand binding affinities of recombinant NMDA receptors is dependent on their subunit composition. The NR1-NR2A, NR1-NR2B, NR1-NR2C and NR1-NR2D receptors may account for the antagonist-preferring, agonist-preferring, cerebellar, and medial thalamic subtypes of native NMDA receptors, respectively.

Topics: 2-Amino-5-phosphonovalerate; Animals; Autoradiography; Binding Sites; Binding, Competitive; Brain; Cloning, Molecular; Dizocilpine Maleate; DNA; Glutamic Acid; Ion Channels; Kinetics; Kynurenic Acid; Ligands; Rats; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate; Recombinant Proteins

Immobilization stress in water for 3 h was effective in inducing significant potentiation of [3H](+)-5-methyl-10,11-dihydro-5H- dibenzo [a,d] cyclohepten-5,10-imine ([3H]MK-801) binding 5 days after the stressful manipulation in rat hypothalamus and cerebellum when determined before equilibrium in the absence of any added agonists, in addition to resulting in marked reduction of rearing behaviors of animals. However, the stressful manipulation failed to modulate the [3H]MK-801 binding in other central regions examined, and binding of either [3H]DL-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid or [3H]kainic acid was not significantly affected in all brain structures studied 5 days after the stress application. In contrast, the stressful procedures potentiated binding of both L-[3H]glutamic ([3H]Glu) and [3H]DL-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic ([3H]CGP-39653) acids in the hypothalamus and cerebellum 5 days later, without affecting binding of [3H]-glycine and 5,7-dichloro[3H]kynurenic acid. The systemic administration of corticosterone mimicked the stress manipulation at doses of 5-50 mg/kg in terms of inducing significant enhancement of binding of both [3H]Glu and [3H]CGP-39653 in the hypothalamus and cerebellum when determined 5 days after the single administration. The translation inhibitor cycloheximide was effective in preventing the stress-induced potentiation of [3H]Glu binding in the cerebellum, without altering that in the hypothalamus. Furthermore, the stressful handling significantly increased the densities of [3H]Glu binding sites in the hypothalamus and cerebellum, with the affinities being unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 2-Amino-5-phosphonovalerate; Adrenal Cortex Hormones; Animals; Autoradiography; Behavior, Animal; Brain Chemistry; Cerebellum; Corpus Striatum; Cycloheximide; Dizocilpine Maleate; Dose-Response Relationship, Drug; Glycine; Hypothalamus; Kynurenic Acid; Male; N-Methylaspartate; Rats; Rats, Wistar; Stress, Physiological; Tritium

Chronic (14 days) administration of either imipramine or electroconvulsive shock effected significant changes in the ligand binding properties of the NMDA (N-methyl-D-aspartate) receptor complex in rat cortex. These changes were manifested as: (1) a reduction in the potency of glycine to inhibit the binding of 5,7-dichloro[3H]kynurenic acid to strychnine-insensitive glycine receptors; and (2) a reduction in the proportion of high affinity, glycine-displaceable [3H]CGP-39653 binding to NMDA receptors. Chronic electroconvulsive shock, but not imipramine treatment also reduced the density of [3H]CGP-39653 binding sites in cortical membranes. These findings demonstrate that the ability of chronic antidepressant treatments to induce adaptive changes in the glycine and glutamate regulatory sites of the NMDA receptor is not species specific, since it obtains in rats as well as mice.

Topics: 2-Amino-5-phosphonovalerate; Animals; Cerebral Cortex; Electroshock; Glycine; Imipramine; In Vitro Techniques; Kynurenic Acid; Male; Radioligand Assay; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

Chronic (14 daily injections) treatment of mice with the prototypic tricyclic antidepressant imipramine significantly alters ligand binding to the N-methyl-D-aspartate (NMDA) receptor complex. These effects were compared to a chronic regimen of 1-aminocyclopropanecarboxylic acid, a high-affinity partial agonist at strychnine-insensitive glycine receptors which mimics the effects of imipramine in preclinical models predictive of antidepressant action. Changes in the NMDA receptor complex after chronic, but not acute treatment with imipramine were manifested as: 1) a reduction in the potency of glycine to inhibit [3H]5,7-dichlorokynurenic acid binding to strychnine-insensitive glycine receptors; 2) a decrease in the proportion of high-affinity glycine sites inhibiting [3H]CGP 39653 binding to NMDA receptors; and 3) a decrease in basal [3H]MK-801 binding (under nonequilibrium conditions) to sites within NMDA receptor-coupled cation channels which was reversible by the addition of glutamate. These effects were observed in cerebral cortex, but not in hippocampus, striatum or basal forebrain. Chronic treatment with 1-aminocyclopropanecarboxylic acid resulted in changes which paralleled those of imipramine on ligand binding to the NMDA receptor complex, but the reduction in basal [3H]MK-801 binding did not achieve statistical significance. These findings indicate that adaptive changes in the NMDA receptor complex could be a feature common to chronic treatment with structurally unrelated antidepressants.

Topics: 2-Amino-5-phosphonovalerate; Amino Acids; Amino Acids, Cyclic; Animals; Brain; Dizocilpine Maleate; Drug Administration Schedule; Glycine; Imipramine; In Vitro Techniques; Kynurenic Acid; Male; Mice; Receptors, N-Methyl-D-Aspartate