piperidines and selfotel

The concept of neuroprotection relies on the principle that delayed neuronal injury occurs after ischemia. The phenomenon of the "ischemic cascade" has been described, and each step along this cascade provides a target for therapeutic intervention. A wide variety of drugs have been studied in humans. Ten classes of neuroprotective agents have reached phase III efficacy trials but have shown mixed results. They included calcium channel antagonists, NMDA receptor antagonists, lubeluzole, CDP-choline, the free radical scavenger tirilazad and ebselen, enlimomab, GABA agonist clomethiazole, the sodium channel antagonist fosphenytoin, magnesium, glycine site antagonist GV150526 and piracetam. Furthermore, the mechanisms that underlie the development of focal ischemic injury continue to be discovered, opening new therapeutic perspective for neuroprotection that might clinically be applicable in the future.

Topics: Acute Disease; Adult; Aged; Animals; Antioxidants; Calcium Channel Blockers; Chlormethiazole; Clinical Trials as Topic; Clinical Trials, Phase III as Topic; Excitatory Amino Acid Antagonists; Excitatory Amino Acids; Forecasting; GABA Modulators; Guanidines; Humans; Imidazoles; Middle Aged; Naltrexone; Narcotic Antagonists; Neuroprotective Agents; Pipecolic Acids; Piperidines; Quinoxalines; Rats; Receptors, N-Methyl-D-Aspartate; Reperfusion Injury; Stroke; Thiazoles

Topics: Animals; Brain Ischemia; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Humans; Pipecolic Acids; Piperidines; Receptors, AMPA; Receptors, Kainic Acid; Receptors, N-Methyl-D-Aspartate

The N-methyl-D-aspartate (NMDA) receptor has been recently identified as an important mediator of impulsive choice, as assessed in delay discounting. Although discounting is independently influenced by sensitivity to reinforcer magnitude and delayed reinforcement, few studies have examined how NMDA receptor ligands differentially affect these parameters.. The current study examined the effects of various NMDA receptor ligands on sensitivity to reinforcer magnitude and delayed reinforcement in a delay-discounting procedure.. Following behavioral training, rats received treatments of the following NMDA receptor ligands: the uncompetitive antagonists ketamine (0, 1.0, 5.0, or 10.0 mg/kg; i.p.), MK-801 (0, 0.003, 0.01, or 0.03 mg/kg; s.c.), and memantine (0, 2.5, 5.0, or 10.0 mg/kg; i.p.), the competitive antagonist CGS 19755 (0, 5.0, 10.0, or 20.0 mg/kg; s.c.), the non-competitive NR2B subunit-selective antagonist ifenprodil (0, 1.0, 3.0, or 10.0 mg/kg; i.p), and the partial agonist D-cycloserine (0, 3.25, 15.0, or 30.0 mg/kg; s.c.).. When an exponential model was used to describe discounting, CGS 19755 (5.0 mg/kg) increased impulsive choice without altering sensitivity to reinforcer magnitude. Conversely, ketamine (10.0 mg/kg), memantine (5.0 mg/kg), and ifenprodil (10.0 mg/kg) decreased sensitivity to reinforcer magnitude without altering impulsive choice. MK-801 and D-cycloserine did not alter delay-discounting performance, although two-way ANOVA analyses indicated D-cycloserine (15.0 mg/kg) decreased impulsive choice.. The behavioral changes observed in delay discounting following administration of NMDA receptor antagonists do not always reflect an alteration in impulsive choice. These results emphasize the utility in employing quantitative methods to assess drug effects in delay discounting.

Topics: Animals; Behavior, Animal; Choice Behavior; Cycloserine; Delay Discounting; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Impulsive Behavior; Ketamine; Ligands; Male; Memantine; Pipecolic Acids; Piperidines; Rats; Receptors, N-Methyl-D-Aspartate; Reinforcement, Psychology

Rat hippocampal glutamatergic terminals possess NMDA autoreceptors whose activation by low micromolar NMDA elicits glutamate exocytosis in the presence of physiological Mg(2+) (1.2 mM), the release of glutamate being significantly reduced when compared to that in Mg(2+)-free condition. Both glutamate and glycine were required to evoke glutamate exocytosis in 1.2 mM Mg(2+), while dizocilpine, cis-4-[phosphomethyl]-piperidine-2-carboxylic acid and 7-Cl-kynurenic acid prevented it, indicating that occupation of both agonist sites is needed for receptor activation. D-serine mimicked glycine but also inhibited the NMDA/glycine-induced release of [(3H]D-aspartate, thus behaving as a partial agonist. The NMDA/glycine-induced release in 1.2 mM Mg(2+) strictly depended on glycine uptake through the glycine transporter type 1 (GlyT1), because the GlyT1 blocker N-[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl])sarcosine hydrochloride, but not the GlyT2 blocker Org 25534, prevented it. Accordingly, [(3)H]glycine was taken up during superfusion, while lowering the external concentration of Na(+), the monovalent cation co-transported with glycine by GlyT1, abrogated the NMDA-induced effect. Western blot analysis of subsynaptic fractions confirms that GlyT1 and NMDA autoreceptors co-localize at the pre-synaptic level, where GluN3A subunits immunoreactivity was also recovered. It is proposed that GlyT1s coexist with NMDA autoreceptors on rat hippocampal glutamatergic terminals and that glycine taken up by GlyT1 may permit physiological activation of NMDA pre-synaptic autoreceptors.

Topics: Animals; Aspartic Acid; Calcium; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Glutamic Acid; Glycine; Glycine Plasma Membrane Transport Proteins; Hippocampus; Immunoprecipitation; Magnesium; Male; N-Methylaspartate; Pipecolic Acids; Piperidines; Presynaptic Terminals; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Synaptosomes; Tetrahydronaphthalenes; Tritium

Cannabinoids, as a result of their ability to activate cannabinoid CB1 receptors, have been shown to possess neuroprotective properties in vivo. In vitro studies into neuroprotective effects mediated by CB1 receptors have in general used primary neuronal cultures derived from embryonic rodents. In the present study, we have investigated whether embryonic chick telencephalon primary cultures in serum-free medium are a useful alternative for such in vitro studies. The CB agonist CP 55940 reduced the cAMP response to 5 microM forskolin by 40 and 50% at concentrations of 3 nM and 30 nM, respectively. This reduction was blocked by the CB1 receptor antagonist AM251, indicating the presence of functional CB1 receptors in the cultures. Incubation of the cultures with glutamate (100 microM or 1 mM) for 1 h followed by medium change and incubation for 24 h produced a release of the cytoplasmic enzyme lactate dehydrogenase into the medium. This release was prevented by MK-801 confirming the central role of NMDA receptors in the glutamate toxicity. However, 3-30 nM CP 55940 did not produce any neuroprotection in this model regardless as to whether dibutyryl cyclic AMP was added to the culture medium. The endocannabinoid anandamide was also without effect when added either per se or together with the related N-acyl ethanolamines palmitoylethanolamide, oleoylethanolamide and stearoylethanolamide (at relative concentrations matching those seen in rat brain after excitotoxic insult). It is concluded that embryonic chick neurons in primary serum-free culture are not a useful model for the study of neuroprotective effects mediated by CB1 receptors in vitro.

Topics: Animals; Arachidonic Acids; Cannabinoids; Cells, Cultured; Chick Embryo; Colforsin; Cyclic AMP; Cyclohexanols; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Combinations; Endocannabinoids; Excitatory Amino Acid Antagonists; Glutamic Acid; L-Lactate Dehydrogenase; Models, Animal; Neurons; Pipecolic Acids; Piperidines; Polyunsaturated Alkamides; Pyrazoles; Receptor, Cannabinoid, CB1; Telencephalon

The objective of this study was to investigate the effects of the HIV-1 envelope protein gp120 and its peptide fragments on the function of N-methyl-D-aspartate (NMDA) receptors mediating release of cholecystokinin (CCK) and somatostatin (SRIF). These are nonconventional NMDA receptors recently found to be activated by glycine or D-serine 'only'. The release of cholecystokinin-like immunoreactivity (CCK-LI) and of somatostatin-like immunoreactivity (SRIF-LI) elicited by 12 mM K+ from superfused rat neocortex synaptosomes was potently increased by gp120, its cyclic V3 loop and the linear V3 sequence BRU-C-34-A, but not by RP-135 (a central portion of BRU-C-34-A). The EC50 values of gp120 were 0.02 nM (CCK-LI release) and 0.01 nM (SRIF-LI release). The releasing effect of gp120 was prevented by blocking the glycine site or the ion channel of NMDA receptors, but not the glutamate recognition site; in addition, the gp120 effect was strongly inhibited by nanomolar concentrations of Zn2+ ions and by low micromolar concentrations of ifenprodil. It is concluded that gp120 acts as a very potent agonist at the glycine site of NMDA receptors sited on CCK- and SRIF-releasing nerve endings; the protein is able to activate the receptor channel in the absence of glutamate. Gp120 activates the receptors through its V3 loop as peptide fragments related to V3 retain near-maximal activity. The sensitivity of the gp120 effect to both Zn2+ and ifenprodil would not be incompatible with the idea that these NMDA receptors contain the triple subunit combination NR1/NR2A/NR2B.

Topics: 2-Amino-5-phosphonovalerate; Animals; Cerebral Cortex; Cholecystokinin; Dizocilpine Maleate; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; HIV Envelope Protein gp120; HIV-1; Indoles; Kynurenic Acid; Male; Maleimides; Neurons; Nitroarginine; Peptide Fragments; Pipecolic Acids; Piperazines; Piperidines; Potassium; Protein Structure, Tertiary; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Somatostatin; Synaptic Transmission; Synaptosomes; Zinc

Conantokins, peptides from Conus snails, are N-methyl-D-aspartate (NMDA) receptor antagonists. NMDA receptor antagonists potentiate L-3,4-dihydroxyphenylalanine (L-DOPA)-induced rotation in 6-hydroxydopamine-treated rodents, an index of anti-Parkinsonian potential. This study examined the effects of conantokin-G, conantokin-T(G), CGS 19755, and ifenprodil on L-DOPA-induced contralateral rotation and immediate early gene (IEG) expression in 6-hydroxydopamine-treated rats. Rats received unilateral infusions of 6-hydroxydopamine into the medial forebrain bundle. Three weeks later, rats were treated with an NMDA receptor antagonist, followed by an injection of L-DOPA. Contralateral rotations were recorded for 2 h. In addition, the expression of zif268 and c-fos were examined. Conantokin-G, conantokin-T(G), and CGS 19755 potentiated L-DOPA-induced rotation. Conantokin-G and ifenprodil had no effect on L-DOPA-induced IEG expression, whereas conantokin-T(G) and CGS 19755 attenuated expression. These data suggest that conantokins may be useful in treating Parkinson's disease. Furthermore, different NMDA receptor antagonists have distinct effects on striatal gene expression.

Topics: Animals; Antiparkinson Agents; Conotoxins; DNA-Binding Proteins; Drug Interactions; Early Growth Response Protein 1; Excitatory Amino Acid Antagonists; Gene Expression; Genes, fos; Genes, Immediate-Early; Immediate-Early Proteins; Intercellular Signaling Peptides and Proteins; Levodopa; Male; Mollusk Venoms; Peptides; Pipecolic Acids; Piperidines; Rats; Rats, Sprague-Dawley; Transcription Factors

The human NMDAR2D subunit was cloned, and the pharmacological properties of receptors resulting from injection of transcripts encoding human NMDAR1A and NMDAR2D subunits in Xenopus oocytes were characterized by profiling NMDA receptor agonists and antagonists. We found that glutamate, NMDA, glycine, and D-serine were significantly more potent on hNMDAR1A/2D than on hNMDAR1A/2A or hNMDAR1A/2B. Also, the potencies of NMDA and glycine were higher for hNMDAR1A/2D than for hNMDAR1A/2C. Ifenprodil was more potent at hNMDAR1A/2B than at hNMDAR1A/2D, whereas 5,7-dichlorokynurenate was more potent at hNMDAR1A/2A than at hNMDAR1A/2D. As measured in transiently transfected human embryonic kidney 293 cells, the maximal inward current in the presence of external Mg2 occurred at -40 mV, and full block was not observed at negative potentials. Kinetic measurements revealed that the higher affinity of hNMDAR1A/2D for both glutamate and glycine relative to hNMDAR1A/2A and hNMDA1A/2B can be explained by slower dissociation of each agonist from hNMDAR1A/2D. The hNMDAR1A/2D combination represents a pharmacologically and functionally distinct receptor subtype and may constitute a potentially important target for therapeutic agents active in the human CNS.

Topics: Animals; Calcium; Cells, Cultured; DNA, Complementary; Dose-Response Relationship, Drug; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Fetus; Glutamic Acid; Glycine; Humans; Kidney; Kynurenic Acid; Membrane Potentials; Molecular Sequence Data; N-Methylaspartate; Oocytes; Patch-Clamp Techniques; Pipecolic Acids; Piperidines; Receptors, N-Methyl-D-Aspartate; Recombinant Proteins; Sequence Homology, Amino Acid; Serine; Xenopus laevis

Dopamine D1 receptor regulation of striatal gene expression is dependent on N-methyl-D-aspartate (NMDA) receptors. To determine whether pharmacologically distinct NMDA receptors are differentially involved, we examined the effects of different NMDA receptor antagonists on D1-induced immediate early gene expression. Systemic administration of the channel blocking antagonists MK-801 and dextrorphan and the competitive antagonist CGS 19755 blocked gene expression induced by the D1 agonist SKF 82958. The NMDA polyamine site antagonist ifenprodil, however, potentiated the effect of SKF 82958. Since ifenprodil is selective for receptors containing the NR2B subunit, the data suggest that subtypes of NMDA receptors may be differentially involved in regulating striatal function.

Topics: Animals; Corpus Striatum; Dextrorphan; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Gene Expression Regulation; Genes, Immediate-Early; Male; Pipecolic Acids; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D1; Receptors, N-Methyl-D-Aspartate

The function of striatopallidal neurons is regulated by N-methyl-D-aspartate (NMDA) and dopamine D2 receptors. Previous studies show that immediate early gene induction by D2 receptor blockade is suppressed by NMDA receptor antagonists. Because the pharmacology of NMDA receptors depends on the incorporation of different NR2 subunits and NR2 subunits show regional and cellular differences in their expression in striatum, our study examined whether different NMDA receptor antagonists would have differential effects on eticlopride-induced immediate early gene expression in striatum. Male Sprague-Dawley rats were pretreated with vehicle, CGS 19755, MK-801 or ifenprodil. Rats then received injections of eticlopride and were killed 40 min later. In situ hybridization histochemistry was used to determine the expression of c-fos and zif268 in the striatum. Eticlopride increased immediate early gene expression in striatum, with the increase generally being greater in lateral than in medial striatum. Pretreatment with each of the NMDA receptor antagonists dose-dependently decreased the expression of the immediate early genes. This suppression of eticlopride-induced gene expression was significant only in the medial-central aspect of striatum. Although there was a trend toward suppression of the gene induction in lateral striatum, it did not reach statistical significance and was not typically dose dependent. The data suggest that different types of NMDA receptor antagonists do not exert differential effects on D2 dopamine receptor-mediated function in the striatum. In addition, the data indicate that eticlopride-induced gene expression in the striatum is not uniformly dependent on NMDA receptor activation.

Topics: Animals; Corpus Striatum; Dizocilpine Maleate; Dopamine Antagonists; Excitatory Amino Acid Antagonists; Gene Expression; Genes, Immediate-Early; Male; Pipecolic Acids; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Salicylamides

The neuroprotective activity of (1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (CP-101,606), an N-methyl-D-aspartate (NMDA) receptor antagonist structurally similar to ((+/-)-(R*,S*)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-++ +piperidineethanol (ifenprodil), was investigated in neurons in primary culture. CP-101,606 potently and efficaciously protected hippocampal neurons from glutamate toxicity but was > 900-fold less effective for cerebellar granule neurons. The neuroprotective activity in the hippocampal neurons is mediated through a high affinity binding site distinct from the agonist and thienylcyclohexylpiperidine (TCP) binding sites of the NMDA receptor. Autoradiography indicates the CP-101,606 binding site is localized in forebrain, most notably in hippocampus and the outer layers of cortex. The functional selectivity for hippocampal neurons, forebrain localization of binding sites, and structural relation to ifenprodil suggest that CP-101,606 is an NMDA antagonist highly selective for NR2B subunit containing receptors.

Topics: Animals; Autoradiography; Binding Sites; Cells, Cultured; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glutamic Acid; Glycine; Kinetics; Neurons; Neuroprotective Agents; Pipecolic Acids; Piperidines; Prosencephalon; Rats; Receptors, N-Methyl-D-Aspartate; Stereoisomerism

The cytotoxicity induced by the transient expression of functional N-methyl-D-aspartate (NMDA) receptors has been examined with the use of a luciferase reporter assay in Chinese hamster ovary cells. Various NMDA receptor antagonists, in a dose-dependent manner, prevented a loss of luciferase activity 24 to 48 hr post-transfection of either the NR1/NR2A or NR1/ NR2B subunit receptor configurations, likely correlating to the time required to express functionally these receptors. Both glutamate and NMDA were potently cytotoxic to transfected cells previously protected by antagonists. The novel ifenprodil analog (1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (CP101,606-27) protected cells expressing NR1/NR2B, but not those cells expressing either NR1/NR2A or, putatively, NR1/NR2A/NR2B. Decreased cytotoxicity was observed when a mutated NR1 subunit (N616R) with reduced Ca++ permeability was used in coexpression studies with NR2A or NR2B. In contrast to our results with NR1/NR2A or NR1/NR2B, cells expressing NR1/NR2C did not perish. Our studies suggest that expression of functional NMDA receptors in non-neuronal cells leads to a form of excitotoxicity similar to that observed in mammalian neurons in vitro.

Topics: Animals; Calcium; Cell Survival; CHO Cells; Cricetinae; Dizocilpine Maleate; Kynurenic Acid; L-Lactate Dehydrogenase; Luciferases; Pipecolic Acids; Piperidines; Receptors, N-Methyl-D-Aspartate; Transfection

A series of 3- and 4-(sulfo- and sulfonamidoalkyl)pyridine and piperidine-2-carboxylic acid derivatives as analogs of NMDA receptor antagonists was prepared. Affinity for the NMDA receptor was determined by binding assays using the specific radioligand [3H] (2SR,4RS)-4-(phosphonomethyl)piperidine-2-carboxylic acid (CGS-19755). The 3-alkylsulfonyl moiety was introduced by selective reduction of a carboxylic acid function followed by bromination, substitution by Na2SO3 and catalytic reduction. For the 4-alkylsulfonic derivatives the crucial step was the introduction of the 2-cyano function and its further conversion to 2-carboxylic acid. The most potent compound of the series was the pyridine (11a) [4-(sulfomethyl)pyridine-2-carboxylic acid] with a modest IC50 of 40 microM. A molecular modeling study has been undertaken to understand the pharmacological results. In a first step, a comparative modeling study of the active pyridine and the poorly active piperidine sulfonic acid derivatives 11a and 10a [4-(sulfomethyl)piperidine-2-carboxylic acid] and of the phosphonic homologues was performed. We propose that the binding geometry of the sulfonic moiety within the NMDA receptor is different from that of the phosphonic containing antagonists. In order to test this assumption, we have made, in a second step, a complete conformational analysis of the sulfonic acid derivatives, as well as some analogs taken from the literature, either active or inactive as NMDA antagonists. A preferred conformation of the sulfonic acids is proposed.

Topics: Binding, Competitive; Carboxylic Acids; Excitatory Amino Acid Antagonists; Kinetics; Molecular Conformation; Pipecolic Acids; Piperidines; Pyridines; Receptors, N-Methyl-D-Aspartate; Structure-Activity Relationship; Sulfonamides; Tritium

The non-competitive N-methyl-D-aspartate (NMDA) antagonist, ifenprodil, discriminates two receptor populations, each of which shows a reciprocal abundance in cultured cortical and cerebellar granule cells. Thus approximately 70% of NMDA-gated membrane current was antagonized with high affinity (IC50 = 1.4 +/- 0.9 microM) in cortical neurones whereas only approximately 20% was antagonized with high affinity (IC50 = 1.3 +/- 0.3 microM) in granule cells. Inhibition curves for CGS 19755 appeared relatively monophasic: this competitive NMDA antagonist had a significantly higher affinity for the granule cell receptor (Ki = 0.8 +/- 0.2 microM) compared with that on cortical neurones (Ki = 2 +/- 0.6 microM). The data suggest that these two antagonists may be of value in identifying the expression of subpopulations of native NMDA receptors in other brain regions.

Topics: Animals; Brain; Brain Chemistry; Cells, Cultured; Glycine; N-Methylaspartate; Neurons; Patch-Clamp Techniques; Pipecolic Acids; Piperidines; Rats; Receptors, N-Methyl-D-Aspartate

Antagonists of 4 distinct regulatory sites on the N-methyl-D-aspartate (NMDA) receptor were tested for their ability to attenuate NMDA-mediated acute excitotoxicity in isolated chick retina of various embryonic ages between days 11 and 19 in ovo. Acute excitotoxicity was monitored by histology and by release of endogenous gamma-aminobutyric acid (GABA) into the medium during 30 min of incubation with 50 microM NMDA. The uncompetitive PCP channel site antagonist, MK-801, the competitive antagonist, CGS 19755, and the strychnine-insensitive glycine site antagonist, 7-chlorokynurenate, completely blocked NMDA-induced cell swelling and increased GABA release at all ages tested. Potencies versus NMDA were MK-801 greater than CGS 19755 greater than 7-chlorokynurenate with IC50S of 0.02, 0.62, and 15 microM, respectively. NMDA antagonism by the polyamine site antagonist, ifenprodil, differed from other classes of antagonists in several respects. At the earlier embryonic ages tested (E12-13) ifenprodil provided differential protection; completely blocking somal and neuritic swelling in most but not all inner nuclear layer neurons and inner plexiform processes. In dose-response studies, ifenprodil attenuated the NMDA-induced increase in medium GABA at all ages tested with an Imax of 10 microM. Ifenprodil, however, showed a decreased ability to completely protect some NMDA-sensitive neurons. This was reflected both histologically and by GABA release. Maximal attenuation of NMDA evoked GABA release was 83, 80, 62 and 50% at days E12, 13, 15 and 19, respectively. Histologically, differential protection was seen at E12 and 13, in limited areas at E15, and was no longer present at E19.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amino Acids; Animals; Biogenic Polyamines; Chick Embryo; Dizocilpine Maleate; Kynurenic Acid; N-Methylaspartate; Pipecolic Acids; Piperidines; Receptors, Glutamate; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Receptors, Phencyclidine; Retina

The administration of methamphetamine (METH) to experimental animals results in damage to nigrostriatal dopaminergic neurons. We have demonstrated previously that the excitatory amino acids may be involved in this neurotoxicity. For example, several compounds which bind to the phenyclidine site within the ion channel linked to the N-methyl-D-aspartate (NMDA) receptor protected mice from the METH-induced loss of neostriatal tyrosine hydroxylase activity and dopamine content. The present study was conducted to characterize further the role of the excitatory amino acids in mediating the neurotoxic effects of METH. The administration of three or four injections of METH (10 mg/kg) every 2 hr to mice produced large decrements in neostriatal dopamine content (80-84%) and in tyrosine hydroxylase activity (65-74%). A dose-dependent protection against these METH-induced decreases was seen with two noncompetitive NMDA antagonists, ifenprodil and SL 82.0715 (25-50 mg/kg/injection), both of which are thought to bind to a polyamine or sigma site associated with the NMDA receptor complex, and with two competitive NMDA antagonists, CGS 19755 (25-50 mg/kg/injection) and NPC 12626 (150-300 mg/kg/injection). Moreover, an intrastriatal infusion of NMDA (0.1 mumol) produced a slight but significant loss of neostriatal dopamine which was potentiated in mice that also received a systemic injection of METH. The results of these studies strengthen the hypothesis that the excitatory amino acids play a critical role in the nigrostriatal dopaminergic damage induced by METH.

Topics: Amino Acids; Animals; Corpus Striatum; Dizocilpine Maleate; Male; Methamphetamine; Mice; N-Methylaspartate; Pipecolic Acids; Piperidines; Receptors, Dopamine; Receptors, N-Methyl-D-Aspartate; Tyrosine 3-Monooxygenase

The non-competitive N-methyl-D-aspartate (NMDA) antagonists (channel blockers), MK 801, phencyclidine (PCP) and ketamine induced spontaneous tail-flicks in rats. Their order of relative potency (MK 801 greater than PCP greater than ketamine) corresponds to their relative affinities for the ion channel coupled to NMDA receptors. Drugs interacting with their other potential targets (sigma receptors as well as dopamine, serotonin and noradrenaline uptake sites) failed to induce spontaneous tail-flicks. In addition, the catecholamine stimulants, methylphenidate and cocaine were inactive. CPP and CGS 19755, antagonists at the NMDA recognition site, also dose dependently elicited spontaneous tail-flicks: their maximal effect was equal to that of the channel blockers. In contrast, HA-966 and ifenprodil, putative antagonists at the glycine and polyamine recognition sites, respectively, failed to elicit spontaneous tail-flicks. These data demonstrate that both antagonists of the NMDA recognition site and non-competitive blockers of the associated channel induce spontaneous tail-flicks in rats.

Topics: Animals; Behavior, Animal; Dizocilpine Maleate; Dose-Response Relationship, Drug; Ion Channels; Ketamine; Male; N-Methylaspartate; Organophosphorus Compounds; Phencyclidine; Pipecolic Acids; Piperazines; Piperidines; Pyrrolidinones; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate

The actions of a series of endogenous excitatory amino acid (EAA) agonists and synthetic antagonists at the N-methyl-D-aspartate (NMDA) receptor system coupled to the evoked release of gamma-[3H]aminobutyric acid (GABA) from purified populations of striatal neurons in primary culture were examined. EAA agonists displayed the following rank order of potency in evoking [3H]GABA release: glutamate greater than homocysteate greater than aspartate, NMDA greater than cysteine sulfinate. Glutamate, homocysteate and cysteine sulfinate were equieffective, whereas at saturating concentrations, aspartate and NMDA reached 75 and 65%, respectively, of the maximum efficacy of the former three agonists. The release of [3H]GABA evoked by 100 microM NMDA was attenuated in a dose-dependent manner by the following antagonists (IC50, micromolar): MK-801 (0.067), phencyclidine (0.151), CGS-19755 (3.31), 2-aminophosphonovalerate (18.8), kynurenate (100) and gamma-D-glutamylglycine (100). The antagonist properties of MK-801 and phencyclidine were not competitive with NMDA, whereas NMDA dose-response curves performed in the absence and presence of increasing concentrations of CGS-19755 resulted in parallel rightward shifts (pA2 = 5.95). CGS-19755 produced similar rightward shifts of the homocysteate dose-response curve (pA2 = 5.89). At glutamate concentrations less than 100 microM, CGS-19755 and 2-aminophosphonovalerate were potent antagonists of glutamate-evoked release; however, at glutamate concentrations greater than 100 microM these agents were ineffective blockers. The blockade of NMDA-evoked release of [3H]GABA by kynurenate was not competitive in nature.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 2-Amino-5-phosphonovalerate; Amino Acids; Animals; Cells, Cultured; Corpus Striatum; Dose-Response Relationship, Drug; gamma-Aminobutyric Acid; Glutamates; Glutamic Acid; Glycine; Mice; Neurons; Pipecolic Acids; Piperidines; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

In synaptic plasma membranes from rat forebrain, the potencies of glycine recognition site agonists and antagonists for modulating [3H]1-[1-(2-thienyl)cyclohexyl]piperidine ([3H]TCP) binding and for displacing strychnine-insensitive [3H]glycine binding are altered in the presence of N-methyl-D-aspartate (NMDA) recognition site ligands. The NMDA competitive antagonist, cis-4-phosphonomethyl-2-piperidine carboxylate (CGS 19755), reduces [3H]glycine binding, and the reduction can be fully reversed by the NMDA recognition site agonist, L-glutamate. Scatchard analysis of [3H]glycine binding shows that in the presence of CGS 19755 there is no change in Bmax (8.81 vs. 8.79 pmol/mg of protein), but rather a decrease in the affinity of glycine (KD of 0.202 microM vs. 0.129 microM). Similar decreases in affinity are observed for the glycine site agonists, D-serine and 1-aminocyclopropane-1-carboxylate, in the presence of CGS 19755. In contrast, the affinity of glycine antagonists, 1-hydroxy-3-amino-2-pyrrolidone and 1-aminocyclobutane-1-carboxylate, at this [3H]glycine recognition site increases in the presence of CGS 19755. The functional consequence of this change in affinity was addressed using the modulation of [3H]TCP binding. In the presence of L-glutamate, the potency of glycine agonists for the stimulation of [3H]TCP binding increases, whereas the potency of glycine antagonists decreases. These data are consistent with NMDA recognition site ligands, through their interactions at the NMDA recognition site, modulating activity at the associated glycine recognition site.

Topics: Animals; Aspartic Acid; Binding Sites; Binding, Competitive; Glutamates; Glutamic Acid; Glycine; Ligands; N-Methylaspartate; Phencyclidine; Pipecolic Acids; Piperidines

The interaction between glycine and competitive N-methyl-D-aspartate (NMDA) antagonists was investigated. Glycine (IC50 = 170 nM) partially (approximately 60%) inhibited [3H]CGS-19755 ((+/-)-4-phosphonomethyl-2-piperdine carboxylic acid), but not [3H]CPP (3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid) binding. The action of glycine was mimicked by D-serine and antagonized by 7-chlorokynurenate. CGS-19755 (IC50 = 230 nM) partially inhibited [3H]glycine binding from strychnine-insensitive sites; this effect was antagonized by NMDA. CPP and NPC 12626 (2-amino-4,5-(1,2-cyclohexyl)-7-phosphonoheptanoic acid) inhibited [3H]glycine binding, but only at concentrations 100- to 1000-fold greater than required to displace [3H]CGS-19755 or [3H]CPP. These data provide the first evidence for bidirectional interactions between glycine and NMDA recognition sites and suggest pharmacological differences among competitive NMDA antagonists.

Topics: Amino Acids; Animals; Brain Chemistry; In Vitro Techniques; Kynurenic Acid; Male; Pipecolic Acids; Piperazines; Piperidines; Rats; Rats, Inbred Strains; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Serine

Several lines of evidence suggest a tight functional coupling between N-methyl-D-aspartate (NMDA) and phencyclidine (PCP) receptors. The effects of PCP receptor agonists (PCP, dexoxadrol, ketamine and MK-801) and NMDA receptor antagonists, cis-4-phosphonomethyl-2-piperidine carboxylic acid (CGS-19755) and 3-(2-carboxypiperizin-4-yl)-propyl-1-phosphonic acid (CPP), have been examined on the metabolism of dopamine in the mesocortex, with a view of studying the coupling between these two receptor systems. Phencyclidine receptor agonists selectively increased the metabolism of dopamine in the mesocortex without affecting the metabolism of dopamine in the striatum. N-Methyl-D-aspartate and the competitive antagonists of NMDA receptors did not effect the metabolism of dopamine, neither did the sigma receptor ligands, 1,3-di-(2-tolyl)guanidine (DTG) and rimcazole. Rimcazole also did not affect the increases in the metabolism of dopamine in the mesocortex, seen after MK-801. These data indicate that dopaminergic neurons in the mesocortex are positively modulated by PCP receptors but tentatively suggest that those recognition sites for PCP are not coupled to NMDA receptors.

Topics: 3,4-Dihydroxyphenylacetic Acid; Animals; Brain Chemistry; Carbazoles; Cerebral Cortex; Dibenzocycloheptenes; Dizocilpine Maleate; Dopamine; Dose-Response Relationship, Drug; Guanidines; Ligands; Male; Neural Pathways; Pipecolic Acids; Piperazines; Piperidines; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Receptors, Phencyclidine; Stereoisomerism

We have administered antagonists acting competitively or noncompetitively at the N-methyl-D-aspartate receptor after a short period of incomplete ischaemia and evaluated selective neuronal loss in the CA1 region of the rat hippocampus. The competitive antagonists D-(-)-2-amino-7-phosphonoheptanoate (2APH); 100 or 330 mg/kg; 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonate (CPP); 3.3 or 10 mg/kg; and CGS 19755 (cis-4-phosphonomethyl-2-piperidine carboxylate) 3.3 or 10 mg/kg; and the noncompetitive antagonists MK801 [+)5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate), 0.3, 1, or 3 mg/kg, and dextrorphan, 2, 6, 18, or 54 mg/kg, were administered intraperitoneally 15 min and 5 h after a 10-min incomplete ischaemia period; additionally MK801 (1 or 3 mg/kg) and CGS 19755 (10 or 30 mg/kg) were administered 5 and 10 h postischaemia. Seven days after ischaemia, the brains were fixed by perfusion. CA1 pyramidal cell counts were performed on Nissl-stained sections using an ocular grid piece. Ventilated (no ischaemia) control animals had a mean of 406 +/- 13 CA1 neurones/3 grid lengths. Ischaemia reduced this mean to 157 +/- 23. A significant protective effect against this cell loss was seen after two injections (at 15 min and 5 h postischaemia) of 2APH, CPP (10 mg/kg), CGS 19755 (10 mg/kg), MK801 (1 mg/kg), and dextrophan (54 mg/kg). Delayed injection (5 and 10 h postischaemia) of CGS 19755 (10 and 30 mg/kg) and MK801 (1 and 3 mg/kg) did not provide any protection against pyramidal cell loss.

Topics: 2-Amino-5-phosphonovalerate; Amino Acids; Animals; Anticonvulsants; Aspartic Acid; Brain; Brain Ischemia; Dibenzocycloheptenes; Dizocilpine Maleate; Male; N-Methylaspartate; Neurons; Pipecolic Acids; Piperazines; Piperidines; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

The effects of excitatory amino acid antagonists on convulsions induced by intracerebroventricular (i.c.v.) or systemic (s.c.) administration of the gamma-aminobutyric acidA (GABAA) antagonist bicuculline (BIC) were tested in mice. 3-[+/-)-2-Carboxypiperazin-4-yl)-propyl-1-phosphonate (CPP), 2-amino-7-phosphonoheptanoate (AP7) and (+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cycloheptan-5,10-imine maleate (MK-801) were used as representatives of N-methyl-D-aspartate (NMDA) antagonists. gamma-D-Glutamylaminomethylsulphonate (gamma-D-GAMS) typified a preferential kainate (KA) antagonist, 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX) represented a preferential quisqualate (QA) antagonist, and kynurenic acid (KYNA) was used as a mixed NMDA/KA antagonist. Bicuculline methiodide (BMI) induced clonic convulsions following i.c.v. administration with a CD50 of 0.183 nmol (range 0.164-0.204). The excitatory amino acid antagonists blocked clonic seizures induced by BMI in the dose of 0.224 nmol (approximately CD97) when coinjected into the lateral ventricle. CPP (ED50 0.0075 nmol) was the most potent anticonvulsant and was followed by AP7 (0.182 nmol), MK-801 (0.22 nmol), gamma-D-GAMS (0.4 nmol), KYNA (1.7 nmol) and CNQX (5.17 nmol). Muscimol (MSC), the GABAA agonist, blocked BMI-induced seizures with an ED50 of 0.25 nmol. Systemic (s.c.) administration of BIC induced in mice generalized seizures with a CD50 of 2.2 mg/kg (range 1.9-2.5) for clonus and CD50 of 2.4 mg/kg (range 2.2-2.7) for tonus.2+ the pathogenesis of seizures triggered by bicuculline in mice.

Topics: Animals; Bicuculline; Dibenzocycloheptenes; Dizocilpine Maleate; Dose-Response Relationship, Drug; Male; Mice; Muscimol; Pipecolic Acids; Piperazines; Piperidines; Receptors, Amino Acid; Receptors, Cell Surface; Seizures

Pharmacological inhibition of cell excitation during focal ischemia was studied in the rat middle cerebral artery occlusion model. The potent and selective N-methyl-D-aspartate antagonist CGS 19755, administered 5 minutes prior to or 5 minutes following permanent middle cerebral artery occlusion, caused a substantial decrease in infarct size, which was associated with reduction of postischemic cerebral glucose hypermetabolism. These data support a role for excitation-induced hypermetabolism in the pathogenesis of infarction following focal cerebrovascular occlusion.

Topics: Animals; Deoxy Sugars; Deoxyglucose; Energy Metabolism; Ischemic Attack, Transient; Male; Pipecolic Acids; Piperidines; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

We evaluated several doses of cis-4-(phosphonomethyl)-2-piperidine-carboxylic acid (CGS-19755), a potent competitive N-methyl-D-aspartate (NMDA) receptor antagonist, systemically administered either before or after 20 to 30 minutes of global ischemia in rats. We measured outcome by mortality, histological damage by light microscopy, and learning ability on an eight-arm maze, and determined the drug's mechanism of action by an immunohistochemical assay of calcium-calmodulin binding. High-dose treatment begun prior to ischemia resulted in reduced cellular damage in severely ischemic hippocampal tissue, but also caused high mortality due to respiratory depression. Treatment begun 30 minutes after ischemia resulted in little histological protection but significantly improved learning ability when tested 1 month after ischemia, and did not increase mortality. Furthermore, CGS-19755, 10 mg/kg intraperitoneally, begun either before or after ischemia substantially reduced calcium influx into ischemic neurons as evidenced by reduced calcium-calmodulin binding. We conclude that CGS-19755 prevents calcium entry into ischemic neurons and may be effective therapy for very acute cerebral ischemia.

Topics: Animals; Calcium; Calmodulin; Dose-Response Relationship, Drug; Ischemic Attack, Transient; Male; Pipecolic Acids; Piperidines; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

DL-2-Amino-3-phosphonopropionic acid, a phosphonate-substituted derivative of aspartic acid, has been shown to be an inhibitor of excitatory amino acid-stimulated phosphoinositide hydrolysis in rat brain slices. In this study, the enantiomers of 2-amino-3-phosphonopropionic acid were synthesized and used to further characterize the stereoselectivity and mechanism of interaction of this compound for inhibiting phosphoinositide-coupled (metabotropic) excitatory amino acid receptors. L-2-Amino-3-phosphonopropionic acid was 3-5 times more potent than D-2-amino-3-phosphonopropionic acid as an inhibitor of ibotenate-stimulated [3H]inositol monophosphate formation in slices of the rat hippocampus or quisqualate-stimulated [3H]inositol monophosphate formation in neonatal rat cerebral cortical slices. Carbachol-stimulated phosphoinositide hydrolysis was not inhibited by L-2-amino-3-phosphonopropionic acid, and L-2-amino-3-phosphonopropionic acid had no appreciable affinity for ionotropic excitatory amino acid receptors at concentrations required to inhibit metabotropic excitatory amino acid responses. The inhibitory effects of L-2-amino-3-phosphonopropionic acid or L-2-amino-4-phosphonobutyric acid on phosphoinositide hydrolysis were not competitive, because they could not be surmounted by increasing concentrations of ibotenate or quisqualate. L-2-Amino-3-phosphonopropionic acid inhibition also could not be prevented by washing the tissue before incubation with ibotenate. Thus, L-2-amino-3-phosphonopropionic acid is a stereoselective inhibitor of metabotropic excitatory amino acid receptors with little affinity for ionotropic receptors. However, the inhibitory effects of L-2-amino-3-phosphonopropionic acid or L-2-amino-4-phosphonobutyric acid were not readily reversed, and the site at which they act to inhibit metabotropic excitatory amino acid receptors remains to be determined.

Topics: Alanine; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Aminobutyrates; Animals; Aspartic Acid; Brain; Hydrolysis; Ibotenic Acid; Inositol Phosphates; Kainic Acid; Male; N-Methylaspartate; Pipecolic Acids; Piperidines; Radioligand Assay; Rats; Rats, Inbred Strains; Receptors, Amino Acid; Receptors, Cell Surface; Stereoisomerism

The experiments examined the ability of competitive N-methyl-D-aspartate (NMDA) antagonists (CPP, CGS 19755), noncompetitive NMDA antagonists [phencyclidine (PCP), ketamine, MK-801], other putative excitatory amino acid antagonists (ifenprodil, PK 26124), and anticonvulsants (pentobarbital, chlordiazepoxide) to antagonize the discriminative stimulus (DS) effects of NMDA and to produce PCP-like DS effects. Rats were trained to discriminate NMDA (40 mg/kg) from saline. The DS effects of NMDA were blocked by the competitive NMDA antagonists but were antagonized at best partially by the other drugs tested. The response rate decreasing effects of NMDA were attenuated to varied extents by both the competitive and the noncompetitive NMDA antagonists. Some competitive and noncompetitive NMDA antagonists partially mimicked NMDA. To further examine their NMDA-antagonist properties, the compounds were also tested for antagonism of NMDA (160 mg/kg)-induced lethality in mice; only the competitive and noncompetitive NMDA antagonists completely protected against NMDA-induced lethality. In rats discriminating PCP (2.5 mg/kg) from saline, the competitive NMDA antagonists produced less drug-appropriate responding than the noncompetitive NMDA antagonists but more than was produced by the other drugs tested. The extent to which compounds antagonize behavioral effects of NMDA and produce PCP-like DS effects may depend partly on the effect measured and on the component of the NMDA receptor complex with which they interact. Although the competitive NMDA antagonists were more effective in blocking NMDA than the other drugs tested, they failed to act as pure antagonists of the DS effects of NMDA.

Topics: Animals; Anticonvulsants; Aspartic Acid; Behavior, Animal; Injections, Intraperitoneal; Kainic Acid; Male; Mice; N-Methylaspartate; Phencyclidine; Pipecolic Acids; Piperidines; Rats; Rats, Inbred Strains

We correlated the efficacy of several clinically relevant pharmacotherapies with their ability to prevent calcium influx into neurons and subsequent binding to calmodulin. We studied the administration of CGS 19755, nimodipine, nicardipine, and combinations of these drugs before or immediately after ischemia in globally ischemic rats. Calcium-calmodulin binding was graded by an immunohistochemical assay after 2 and 24 hours of reperfusion (n = 5-6 at each time period), and histologic damage was graded by light microscopy after 72 hours of reperfusion (n = 6). Calcium-calmodulin binding correlated with the severity of delayed histologic damage in various brain regions. In untreated ischemic control rats, marked calcium-calmodulin binding was seen in CA1 and CA3 after 24 hours of reperfusion (p less than or equal to 0.01). Administered before ischemia, CGS 19755 prevented calcium-calmodulin binding across all brain regions after 2 and 24 hours of reperfusion compared with controls (p less than or equal to 0.05). This effect was most prominent in CA3 and CA1, where the drug also reduced delayed neuronal damage (p less than or equal to 0.05). Lower doses or postischemic administration of CGS 19755, nimodipine, nicardipine, and a combination of postischemic CGS 19755 and nicardipine had a more limited effect on calcium-calmodulin binding and did not protect against delayed neuronal damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Brain Ischemia; Calcium; Calmodulin; Hippocampus; Neurons; Nicardipine; Nimodipine; Pipecolic Acids; Piperidines; Rats

The competitive excitatory amino acid antagonist cis-4-phosphonomethyl-2-piperidine-carboxylic acid (CGS 19755) increased the latency for monkeys to remove their tails from warm water (analgesia); larger doses produced ataxia, loss of righting, salivation, and eliminated reactivity to stimulation (anesthesia). CGS 19755 decreased tidal volume and had little effect on frequency of respiration. Although longer lasting, the effects of CGS 19755 were similar to the effects of ketamine, suggesting these effects result from actions at the NMDA receptor complex.

Topics: Analgesics; Anesthetics; Animals; Binding, Competitive; Dose-Response Relationship, Drug; Ketamine; Macaca mulatta; N-Methylaspartate; Pipecolic Acids; Piperidines; Reaction Time; Respiration; Video Recording

CGS 19755 (cis-4-phosphonomethyl-2-piperidine-carboxylic acid), a competitive antagonist at N-methyl-D-aspartate (NMDA)-preferring receptors, blocked both NMDA-induced convulsions in normal CF1 mice and sound-induced wild running in seizure-prone DBA/2 mice. The ED50 values for CGS 19755 to produce these effects (in the range of 2 mg/kg i.p.) were at least 3-fold lower than those which impaired the traction reflex, an index of motor coordination. When administered p.o. by gavage, CGS 19755 had little or no effect in these test procedures. In an experimental model of anxiety in rats, CGS 19755 significantly increased conflict responding within a relatively narrow dose range (minimum effective dose, 1.73 mg/kg i.p.). At higher doses of CGS 19755, this effect appeared to be obscured by drug-induced reductions in overall responding. Potential muscle relaxant effects were also suggested by the generalization of CGS 19755 to diazepam discriminative stimuli (ED50 = 9.0 mg/kg i.p.) and by impaired rotorod performance (ED50 = 6.2 mg/kg i.p.) in rats. Although some resemblances were apparent between the behavioral effects of CGS 19755 and those of phencyclidine-type drugs, the phencyclidine-like behaviors appeared only at considerably higher doses of CGS 19755 than those associated with anticonflict activity, and only partial generalization of CGS 19755 to dexoxadrol was observed at high doses. CGS 19755 promises to be an important new research tool for investigating the function of brain NMDA receptors.

Topics: Animals; Anticonvulsants; Aspartic Acid; Conflict, Psychological; Discrimination Learning; Male; Mice; Mice, Inbred DBA; Motor Activity; N-Methylaspartate; Phencyclidine; Pipecolic Acids; Piperidines; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

A series of 4-(phosphonoalkyl)- and 4-(phosphonoalkenyl)-2-piperidinecarboxylic acids were synthesized, and their biological activity was assessed as competitive ligands for the NMDA receptor, both in vitro by using a receptor binding assay ([3H]CGS 19755 binding) and in vivo by using an NMDA seizure model in mice. The analogues were also evaluated in [3H]AMPA and [3H]kainate binding to assess their affinity for non-NMDA excitatory amino acid receptor subtypes. A number of these analogues show potent and selective NMDA antagonistic activity both in vitro and in vivo. Most notable are 4-(phosphonomethyl)-2-piperidinecarboxylic acid (1a) (CGS 19755) and the phosphonopropenyl analogue 1i, both of which show anticonvulsant activity in the 1-2 mg/kg ip range. With the aid of computer-assisted modeling, a putative bioactive conformation for AP-5 is hypothesized from the SAR data presented and a preliminary model for the antagonist-preferring state of the NMDA receptor is presented.

Topics: Animals; Anticonvulsants; Aspartic Acid; Chemical Phenomena; Chemistry; Male; Mice; N-Methylaspartate; Pipecolic Acids; Piperidines; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Stereoisomerism; Structure-Activity Relationship

The in vivo efficacies and potencies of various excitatory amino acid agonists in inducing cholinergic neuronal degeneration were compared following unilateral injections into the rat striatum. Kainic acid (KA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), ibotenic acid (IBO), and N-methyl-D-aspartic acid (NMDA) all produced dose-related decreases in choline acetyltransferase (ChAT) activity. The relative order of potency was KA greater than AMPA greater than IBO greater than NMDA. Quisqualic acid (QUIS) was about as potent as NMDA, but the maximal decrease in ChAT activity was less (36%). N-acetylaspartyl-L-glutamate (NAAG) did not significantly decrease ChAT activity when up to 1,000 nmoles was injected. Approximate equitoxic doses of agonists were then used to examine the ability of i.p. administered CGS-19755 and MK-801 to prevent in vivo excitatory amino acid-induced cholinergic and GABAergic neuronal degeneration. NMDA-induced decreases in ChAT and glutamic acid decarboxylase (GAD) activities were prevented by CGS-19755 (10-40 mg/kg) and MK-801 (1-10 mg/kg). CGS-19755 (40 mg/kg) and MK-801 (10 mg/kg) did not prevent loss of ChAT or GAD induced by KA or AMPA, but did prevent the degenerative effects of IBO. This study shows that CGS-19755 and MK-801, two NMDA receptor antagonists that act by different mechanisms, are completely selective following systemic administration. Moreover, the in vivo excitotoxic effects of IBO are mediated at NMDA receptor sites that are blocked by these compounds.

Topics: Animals; Aspartic Acid; Choline O-Acetyltransferase; Cholinergic Fibers; Corpus Striatum; Dibenzocycloheptenes; Dizocilpine Maleate; gamma-Aminobutyric Acid; Ibotenic Acid; Male; N-Methylaspartate; Nerve Degeneration; Oxazoles; Pipecolic Acids; Piperidines; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

The purported competitive excitatory amino acid antagonist CGS 19755 was compared to the non-competitive antagonists ketamine and MK-801 in three rhesus monkeys discriminating between 1.78 mg/kg of ketamine and saline while responding under a fixed-ratio 100 schedule of food presentation. MK-801 substituted completely for the ketamine discriminative stimulus and was 32 times more potent than ketamine as a discriminative stimulus. CGS 19755 was studied using single and cumulative dosing procedures up to a dose of 10.0 mg/kg; for all conditions, CGS 19755 produced responding exclusively on the saline lever and had only modest rate-decreasing effects. N-Methyl-D-aspartate administered alone also did not produce ketamine-appropriate responding but did decrease response rates in a dose-related manner. N-Methyl-D-aspartate eliminated responding in all monkeys at doses of 5.6-10.0 mg/kg. MK-801 and ketamine antagonized the rate-decreasing effects of N-methyl-D-aspartate, however, ketamine was most effective as an antagonist at doses that decreased response rates when administered alone. CGS 19755 also attenuated the rate-decreasing effects of N-methyl-D-aspartate and shifted the N-methyl-D-aspartate dose-effect curve more than 5-fold to the right. The magnitude of antagonism of N-methyl-D-aspartate appeared to be somewhat greater with CGS 19755 than with MK-801 or ketamine. Thus, a competitive (CGS 19755) and some non-competitive (MK-801 and ketamine) excitatory amino acid antagonists can attenuate the rate-decreasing effects of N-methyl-D-aspartate.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Anticonvulsants; Aspartic Acid; Dibenzocycloheptenes; Discrimination, Psychological; Dizocilpine Maleate; Ketamine; Macaca mulatta; Male; N-Methylaspartate; Pipecolic Acids; Piperidines

The N-Methyl-D-aspartate (NMDA)-type receptor blocking properties of CGS 19755, a novel, rigid analog of 2-amino-5-phosphonopentanoate, were demonstrated in vitro by the ability of the compound to block NMDA-evoked [3H]acetylcholine release (pA2 = 5.93). CGS 19755 (0.045 and 0.224 mmol/kg i.p.) was shown to be active in vivo as well by its ability to block harmaline-induced increases in cerebellar cGMP. Finally, CGS 19755 blocked sound-induced seizures in DBA/2 mice completely at doses of 1.0 nmol i.c.v. or 0.1 mmol/kg i.p. Taken together, these data indicate that CGS 19755 is a potent and competitive NMDA antagonist in vitro which is also active in vivo.

Topics: Acetylcholine; Animals; Aspartic Acid; Binding, Competitive; Blood-Brain Barrier; Cerebellum; Cyclic GMP; Harmaline; Male; Mice; Mice, Inbred DBA; N-Methylaspartate; Pipecolic Acids; Piperidines; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Seizures

Competitive N-methyl-D-aspartate (NMDA) receptor antagonists, including CGS 19755, have the ability to antagonize NMDA-induced convulsions, to cause ataxia and, at high doses, to increase spontaneous locomotor activity. It was of interest to determine whether or not repeated treatment with CGS 19755 would induce tolerance to some or all of these effects. CGS 19755 was administered to mice twice daily for 14 days at 54 mg/kg i.p. per injection. One day after the last repeated injection, mice were challenged with vehicle or one of several doses of CGS 19755 (10, 30, 54 and 100 mg/kg) and were tested for evidence of motor impairment (using righting reflex and traction tests), for spontaneous locomotor activity and for the threshold dose of NMDA required to induce convulsions. When challenged with CGS 19755, mice that had previously received only vehicle showed reduced motor activity in response to doses of 54 and 100 mg/kg. In contrast, mice that had received the repeated treatment regimen of CGS 19755 increased motor activity in response to challenge doses of 30 and 54 mg/kg. These effects resembled those reported previously by some investigators for phencyclidine. However, repeated treatment with CGS 19755 induced only slight tolerance to the ability of this drug to cause ataxia. In mice treated repeatedly with CGS 19755, the threshold dose of NMDA to induce convulsions did not differ significantly from that in mice treated repeatedly with vehicle, indicating no demonstrable tolerance to the apparent anticonvulsant effects of CGS 19755 over this time period.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Behavior, Animal; Binding, Competitive; Body Weight; Drug Tolerance; Male; Mice; Motor Activity; Pipecolic Acids; Piperidines; Posture; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

1. CGS 19755 (cis-4-phosphonomethyl-2-piperidine carboxylic acid), a rigid analogue of 2-amino-5-phosphonopentanoic acid (AP5), is one of the most potent competitive N-methyl-D-aspartate (NMDA) antagonists described. Using Triton-treated crude synaptic membranes from rat brain, binding studies indicated that [3H]-CGS 19755 bound with high affinity and selectivity to the NMDA-type excitatory amino acid receptor. 2. [3H]-CGS 19755 binding was saturable, reversible, heat-labile, pH-dependent and linear with protein concentration. Specific binding represented 80-85% of the total amount bound. 3. Using a centrifugation assay, saturation experiments revealed two distinct binding components with Kd values of 9 and 200 nM, and corresponding Bmax values of 0.55 and 1.00 pmol mg-1 protein. In contrast, a single binding component with a Kd value of 24 nM and an apparent Bmax value of 0.74 pmol mg-1 protein was observed with a filtration assay. 4. Competition experiments in which both assay techniques were used, showed that [3H]-CGS 19755 selectively labels the NMDA receptor. The most active inhibitors of [3H]-CGS 19755 binding were L-glutamate and CGS 19755 (IC50 values = 100 nM). 5. In the centrifugation assay, a number of excitatory amino acids were found to generate shallow inhibition curves, and computer analysis indicated the presence of two binding components. The quisqualate receptor ligand AMPA (D,L-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate), kainic acid and the non-competitive NMDA antagonists, such as phencyclidine, tiletamine and MK-801, were without activity. 6. The high affinity binding obtained with [3H]-CGS 19755 by use of filtration techniques thus permits the more rapid evaluation of compounds as potential NMDA antagonists and agonists. Therefore, this rigid analogue of AP5 is a more suitable radioligand for NMDA receptors than [3H]-CPP (34-+/-)2-carboxypiperazin-4-yl)propyl-1-phosphonic acid), the corresponding analogue of 2-amino-7-phosphonoheptanoic acid (AP7).

Topics: Animals; Aspartic Acid; Brain; Intracellular Membranes; Male; N-Methylaspartate; Pipecolic Acids; Piperidines; Radioligand Assay; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

Transient brain ischemia results in a selective destruction of cell bodies within the hippocampus and cortex. This cellular destruction appears to be mediated through a release of endogenous exictatory amino acids following the ischemic episode, since the neurotoxic effects of ischemia can be attenuated by compounds that have antagonist activity at N-methyl-D-aspartate (NMDA) receptors. In the present study, the protective effects of a novel NMDA receptor antagonist, CGS 19755, were further evaluated by using quantitative autoradiography to characterize adenosine A1, NMDA, PCP, and benzodiazepine receptors in ischemic gerbil brain. Bilateral carotid artery occlusion (20 minutes) resulted in marked decreases (30-60%) in adenosine A1, NMDA, and PCP, but not benzodiazepine, receptors in gerbil forebrain. Postischemic treatment with CGS 19755 was found to completely block the ischemia-induced decreases in brain adenosine and NMDA receptors. [3H]TCP binding in ischemic gerbil brain was also elevated by CGS 19755 treatment; significant differences remained, however, between the CGS 19755-treated and control gerbils. These results indicate that transient brain ischemia produces significant and selective alterations in gerbil forebrain receptor systems. The observed decreases in radioligand binding are probably reflective of an ischemia-induced destruction of forebrain structures. However, there is some evidence that transient ischemia can also cause long-term changes in the affinity of some receptor systems. The postischemic efficacy of CGS 19755 appears to be due to its ability to block the neurotoxic effects of transient ischemia.

Topics: Adenosine; Animals; Autoradiography; Female; Flunitrazepam; Gerbillinae; Image Processing, Computer-Assisted; Ischemic Attack, Transient; Pipecolic Acids; Piperazines; Piperidines; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Receptors, Phencyclidine

CPP (3-(2-carboxypiperazin-4-yl-propyl-1-phosphonic acid), a rigid analog of AP7 (2-amino-7-phosphonoheptanoate), previously shown to be a selective antagonist of the NMDA (N-methyl-D-aspartate) receptor (IC50 = 209 nM) has been reported to be exceptionally active (IC50 = 430 pM) at benzodiazepine binding sites. Re-examination of CPP, and the rigid AP5 analog, CGS 19755 (cis-4-phosphonomethyl-2-piperidine carboxylic acid; 0.001-10,000 nM), showed that, as previously reported, neither compound affected the binding of [3H]flunitrazepam. These compounds are thus selective NMDA receptor antagonists.

Topics: Animals; Anticonvulsants; Aspartic Acid; Binding, Competitive; Brain; Flunitrazepam; In Vitro Techniques; N-Methylaspartate; Pipecolic Acids; Piperazines; Piperidines; Rats; Receptors, GABA-A

CGS 19755 (cis-4-phosphonomethyl-2-piperidine carboxylic acid) was found to be a potent, stereospecific inhibitor of N-methyl-D-aspartate (NMDA)-evoked, but not KCl-evoked, [3H] acetylcholine release from slices of the rat striatum. The concentration-response curve to NMDA was shifted to the right by CGS 19755 (pA2 = 5.94), suggesting a competitive interaction with NMDA-type receptors. CGS 19755 inhibited the binding of [3H]-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid to NMDA-type receptors with an IC50 of 50 nM, making it the most potent NMDA-type receptor antagonist reported to date. CGS 19755 failed to interact with 23 other receptor types as assessed by receptor binding, including the quisqualate- and kainate-type excitatory amino acid receptors. In crude P2 fractions, no evidence was obtained to suggest that CGS 19755 is taken up by an active transport system. Furthermore, CGS 19755 failed to affect the uptake of L-[3H]glutamate, or to interact with aconitine-induced inhibition of L-[3H]glutamate uptake, the latter finding suggesting a lack of membrane-stabilizing or local anesthetic properties. CGS 19755 selectively antagonized the excitatory effect of iontophoretically applied NMDA in the red nucleus of the rat without affecting the excitatory effects of quisqualate. CGS 19755 blocked the harmaline-induced increase in cerebellar cyclic GMP levels at a dose of 4 mg/kg i.p. with a duration of action exceeding 2 hr. CGS 19755 inhibited convulsions elicited by maximal electroshock in rat (ED50 = 3.8 mg/kg i.p. 1 hr after administration) and in mouse (ED50 = 2.0 mg/kg i.p. 0.5 hr after administration). Likewise, convulsions elicited by picrotoxin were inhibited by CGS 19755, whereas the compound was relatively weak in protecting against convulsions elicited by pentylenetetrazole or strychnine. CGS 19755 produced retention performance deficits in a dark avoidance task. However, CGS 19755 did not show a unique propensity for learning and memory disruption compared to other anticonvulsants.

Topics: Acetylcholine; Aconitine; Animals; Anticonvulsants; Aspartic Acid; Avoidance Learning; Binding, Competitive; Darkness; Glutamates; Glutamic Acid; Male; N-Methylaspartate; Pentylenetetrazole; Picrotoxin; Pipecolic Acids; Piperidines; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Seizures; Structure-Activity Relationship; Tetrodotoxin

N-Methyl-D-aspartate (NMDA) antagonists reduce ischemic brain damage and associated hypermotility. Two potent, selective and competitive NMDA antagonists, cis-4-(phosphonomethyl)-2-piperidine-carboxylic acid (CGS 19755) and 4-(3-phosphonopropyl)-2-piperazine-carboxylic acid (CPP), were characterized in the gerbil ischemia model with respect to dose-response and time course effects. Both drugs were effective in reducing ischemia-induced hippocampal brain damage as well as hypermotility. In this model, CGS 19755 was more potent than CPP, and had protective effects when given after longer delays between ischemia and drug administration.

Topics: Animals; Aspartic Acid; Brain; Female; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Motor Activity; N-Methylaspartate; Neurons; Pipecolic Acids; Piperazines; Piperidines

A computerized motor activity data collection and analysis system is described. An example of the utilization of the Digiscan system is provided, in which motor activity patterns induced by three N-methyl-D-aspartate (NMDA) antagonists and the dissociative anesthetic, ketamine, are compared. All of these compounds produce a distinct pattern of motor activity characterized by an increase in distance traveled, movement time, speed and perimeter walking, with a decrease in vertical activity. Recently described links between NMDA and phencyclidine (PCP) binding sites may account for these findings. The utility of computerized motor activity apparatus is clearly demonstrated.

Topics: 2-Amino-5-phosphonovalerate; Amino Acids; Animals; Aspartic Acid; Dose-Response Relationship, Drug; Electronic Data Processing; Female; Gerbillinae; Ketamine; Motor Activity; N-Methylaspartate; Pipecolic Acids; Piperazines; Piperidines; Time Factors