piperidines and eliprodil

Glutamate is the main excitatory neurotransmitter in the central nervous system and it plays a significant role not only in synaptic transmission but also in acute and chronic neuropathologies including stroke. Presently, four receptors for glutamate have been identified and the NMDA receptor family is the most intensively studied. A number of NMDA receptor antagonists have been developed and used for treatment of neurological diseases in patients. However, all of these drugs have been failed in clinical trials either because of intolerable side effects or lack of medical efficacy. Recently, the understanding of molecular structure of NMDA receptors has been advanced and this finding thus provides information for designing subtype-selective antagonists. Using NR2B subunit selective antagonists, ifenprodil and eliprodil, as basic structure models, second and third generation congeners have been developed. Several NR2B-selective compounds showed neuroprotective actions at doses that did not produce measurable side effects in preclinical studies. Some of NR2B subunit selective antagonists have also been tested for the treatment of ischemic brain injury. The present review describes the role of glutamate in ischemic brain injury with an emphasis on the NR2B containing NMDA receptors.

Topics: Animals; Brain; Brain Ischemia; Conotoxins; Drug Design; Excitatory Amino Acid Antagonists; Felbamate; Glutamic Acid; Humans; Neuroprotective Agents; Phenylcarbamates; Piperidines; Propylene Glycols; Protein Conformation; Rats; Receptors, N-Methyl-D-Aspartate

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

Sigma ligands have been identified as psychotomimetic agents unrelated to opioids. A number of neuroleptics possess moderate to high affinity for sigma binding sites, raising the possibility that sigma receptors mediate some of the antipsychotic effects of neuroleptics. In addition, sigma binding sites have been reported to be reduced in the temporal cortex and in the hippocampus of schizophrenic patients. This hypothesis is further supported by the use of the sigma ligands rimcazole, BMY-14802 and remoxipride as effective antipsychotic agents. The present report, reviewing briefly the physiological effects of sigma ligands, suggests that their antipsychotic properties are related to modulation of NMDA receptors. Thus, the use of sigma ligands may provide further understanding of the pathophysiology of psychoses and open new avenues for their treatment.

Topics: Antipsychotic Agents; Carbazoles; Hippocampus; Humans; Piperidines; Psychotropic Drugs; Pyrimidines; Receptors, sigma; Remoxipride; Schizophrenia; Thalamus

The psychotomimetic effects of opiate agonists/antagonists led to the hypothesis that opiate sigma receptors could be involved in the etiology of schizophrenia. This assumption is supported by animal trials with selective sigma-receptor antagonists. SL 82.0715 is a substance with a highly selective affinity for sigma receptors. To clarify the question whether it improves negative symptoms of schizophrenia, ten chronic schizophrenic patients with a predominant negative symptomatology were examined and treated with increasing doses (2.5 - 10.0 mg/d). Psychopathology was evaluated weekly using the PANSS, BPRS, and CGI, side-effects were assessed by the HAS and the S/A scale. Four patients showed improvement of negative symptoms (two slight, two marked improvement), two patients deteriorated as regards the positive symptomatology, psychopathology in the other patients did not change. The tolerability of SL 82.0715 was very good, no extrapyramidal side-effects occurred. To further evaluate the therapeutic efficacy, open studies with a larger number of patients and/or double-blind studies are necessary.

Topics: Adult; Excitatory Amino Acid Antagonists; Female; Humans; Male; Middle Aged; Piperidines; Psychiatric Status Rating Scales; Receptors, sigma; Schizophrenia; Schizophrenic Psychology

An HPLC method was developed and validated for the determination in human plasma and urine of the enantiomers of eliprodil, (+/-)-alpha-(4-chlorophenyl)-4[(4-fluorophenyl) methyl]piperidine-1-ethanol hydrochloride, a new anti-ischaemic agent administered as a racemate. Both enantiomers are present in human plasma in unchanged and glucuroconjugated form, whereas only the glucuroconjugated form is excreted into urine; as a consequence, such metabolites in human plasma and urine should be submitted to enzymatic deconjugation with beta-glucuronidase (Escherichia coli) before being extracted. The general method involves a liquid-liquid extraction of eliprodil and internal standard from alkalinized plasma or urine with n-hexane, evaporation of the organic phase and derivatization with (S)-(+)-naphthylethyl isocyanate to give carbamate diastereoisomeric derivatives of (S)-(+)- and (R)-(-)-eliprodil and internal standard; after evaporation of the derivatizing mixture and dissolution of the residue in a small volume of phosphate buffer-acetonitrile (60:40, v/v), an aliquot is injected into a column-switching HPLC system. The derivatized sample extract is purified on a precolumn filled with C8-bonded silica material, which is flushed with acetonitrile-water, then diastereoisomers of eliprodil and the internal standard are automatically transferred by the mobile phase to the analytical column. The analytical column is a C8 type, specially deactivated for basic compounds, the mobile phase is 0.025 M phosphate buffer (pH 2.6)-methanol-acetonitrile (42:2:56) at a flow-rate of 1.2 ml min-1 and fluorimetric detector operating at lambda ex = 275 nm and lambda em = 336 nm is used. The retention times, under these conditions, are about 16 and 17 min for (S)-(+)- and (R)-(-)-eliprodil diastereoisomers, respectively, and about 19 min for the first-eluted diastereoisomer of the internal standard. During the analysis time, the precolumn, reset in a different path from that of the analytical column, is back-flushed with different solvents, then re-equilibrated with acetonitrile-water before the next injection. Linearity in plasma, for unchanged eliprodil enantiomers, was assessed in the range 0.15-10 ng ml-1 and for total eliprodil enantiomers (unchanged + conjugated) in the range 0.75-500 ng ml-1; the limit of quantitation (LOQ) is 0.15 ng ml-1 for each unchanged enantiomer and 0.75 ng ml-1 for each total enantiomer. Linearity was also assessed in urine for total (conjugated) e

Topics: Calibration; Chromatography, High Pressure Liquid; Excitatory Amino Acid Antagonists; Glucuronates; Glucuronidase; Humans; Indicators and Reagents; Piperidines; Quality Control; Reference Standards; Reproducibility of Results; Specimen Handling; Spectrometry, Fluorescence; Stereoisomerism

The possible effects on memory, psychomotor performance and mood of eliprodil, a new non-competitive NMDA receptor antagonist acting through the polyamine modulatory site, was assessed in a randomized, double-blind, cross-over, placebo-controlled study involving 11 healthy young male volunteers. Eliprodil 30 mg, a placebo and midazolam 15 mg, a positive control, were administered as a single oral dose at 1 week wash-out intervals. Objective tests evaluated both memory (Sternberg memory scanning and paired words for short-term memory, delayed free recall of pictures for long-term memory) and psychomotor functions and arousal (critical flicker fusion threshold, choice reaction time, body sway). Mood was assessed using self-ratings (LARS, POMS, ARCI). Statistical analysis was performed using an ANOVA with pairwise comparisons using Tukey's method. A single dose of eliprodil 30 mg was free of any detrimental effect on memory and skilled performance and did not produce either subjective sedation or excitation or psychotomimetic effects in comparison with placebo. In contrast, a single dose of midazolam 15 mg induced a marked impairment in psychomotor performance and cognitive functions (significant reduction in CFF, increase in CRT and body sway, disruption of short- and long-term memory). The potent sedative activity of midazolam, peaking 1 to 3 h post-dose, was confirmed by subjective evaluation and had disappeared 8 h post-dose.

Topics: Adult; Affect; Arousal; Attention; Cross-Over Studies; Dose-Response Relationship, Drug; Double-Blind Method; Humans; Male; Mental Recall; Midazolam; Neuropsychological Tests; Piperidines; Psychomotor Performance; Receptors, N-Methyl-D-Aspartate; Retention, Psychology

Topics: Ligands; Piperidines; Receptors, N-Methyl-D-Aspartate; Structure-Activity Relationship; Tropanes

We have previously reported that the long-term exposure of organophosphorus induces vascular dementia (VD) in rats. As a coenzyme, vitamin B6 is mainly involved in the regulation of metabolisms. Whether vitamin B6 improves VD remains unknown.. The model of VD was induced by feeding rats with isocarbophos (0.5 mg/kg per two day, 12 weeks). The blood flow of the posterior cerebral artery (PCA) in rat was assessed by transcranial Doppler (TCD). The learning and memory were evaluated by the Morris Water Maze (MWM) test.. Administration of vitamin B6 increased the blood flow in the right and left posterior cerebral arteries and improved the functions of learning and memory in isocarbophos-treated rats. Vitamin B6 increased the protein levels of N-methyl-D-aspartate receptor (NMDAR) 2B, postsynaptic densities (PSDs) protein 95, and calmodulin-dependent protein kinase II (CaMK-II) in the hippocampus, which were decreased by isocarbophos in rats. Morphological analysis by light microscope and electronic microscope indicated disruptions of the hippocampus caused by isocarbophos were normalized by vitamin B6. Importantly, the antagonist of NMDAR signaling by eliprodil abolished these beneficial effects produced by vitamin B6 on PCA blood flow, learning, memory, and hippocampus structure in rats, as well as the protein expression of NMDAR 2B, PSDs protein 95, and CaMK-II in the hippocampus.. Vitamin B6 activates NMDAR signaling to prevent isocarbophos-induced VD in rats.

Topics: Animals; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Cerebrovascular Circulation; Dementia, Vascular; Disks Large Homolog 4 Protein; Excitatory Amino Acid Antagonists; Hippocampus; Hypertension; Malathion; Male; Maze Learning; Memory; Piperidines; Posterior Cerebral Artery; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Signal Transduction; Ultrasonography, Doppler; Vitamin B 6; Vitamin B Complex

In this paper a robust method is developed for the analysis of data consisting of repeated binary observations taken at up to three fixed time points on each subject. The primary objective is to compare outcomes at the last time point, using earlier observations to predict this for subjects with incomplete records. A score test is derived. The method is developed for application to sequential clinical trials, as at interim analyses there will be many incomplete records occurring in non-informative patterns. Motivation for the methodology comes from experience with clinical trials in stroke and head injury, and data from one such trial is used to illustrate the approach. Extensions to more than three time points and to allow for stratification are discussed.

Topics: Clinical Trials as Topic; Craniocerebral Trauma; Data Interpretation, Statistical; Excitatory Amino Acid Antagonists; Glasgow Outcome Scale; Humans; Models, Biological; Models, Statistical; Piperidines

Measurement of drug release of a sparingly soluble drug by conventional methods proceeds very slowly without the aid of surfactants. Two preliminary automated methods were developed that increase sensitivity and accelerate such studies by working at very small reservoir volumes. All high pressure liquid chromatography (HPLC) equipment components were commercially available. Results are presented for the drug release of a single pellet of the sparingly soluble drug Eliprodil in two types of drug release experiments using (1) a stirred cell and (2) a flow-through method. Release rates measured from each method were comparable.

Topics: Algorithms; Buffers; Chemistry, Pharmaceutical; Chromatography, High Pressure Liquid; Delayed-Action Preparations; Excitatory Amino Acid Antagonists; Piperidines; Polytetrafluoroethylene; Solubility

Prenatal exposure to alcohol can disrupt brain development, leading to a variety of behavioral alterations, including learning deficits. We have postulated that some central nervous system damage may be due to N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity that occurs during ethanol withdrawal. Consistent with this hypothesis, we previously demonstrated that administration of MK-801, an NMDA receptor antagonist, during ethanol withdrawal attenuates ethanol-related learning deficits using an animal model of fetal alcohol effects. However, MK-801 binds to the phencyclidine site, which affects all NMDA receptor subtypes and can cause adverse side effects and toxicity. Eliprodil is a more selective NMDA receptor antagonist that acts at the polyamine modulatory site of NMDA receptors.. The purpose of this study was to determine if administration of eliprodil during ethanol withdrawal would reduce the severity of learning deficits associated with developmental alcohol exposure.. Male rat pups were randomly assigned to ethanol-exposed or control treatments. On postnatal day (PD) 6, during a period of brain development similar to that of the mid-third trimester in humans, subjects were exposed to 6.0 g/kg ethanol or isocaloric maltose solutions via oral gavage. Twenty-four hours after the end of the ethanol treatment, during ethanol withdrawal, all subjects received an intraperitoneal injection of one of three doses of eliprodil (5, 10, or 25 mg/kg) or vehicle. On PD 40, all subjects were tested on a serial spatial discrimination reversal learning task.. Ethanol-exposed subjects treated with vehicle committed a significantly greater number of errors compared to controls. Administration of eliprodil during ethanol withdrawal significantly decreased the number of errors in the ethanol-exposed groups, but had no significant effect on the performance of controls.. These data support the hypothesis that NMDA receptor-mediated excitotoxicity during ethanol withdrawal contributes to fetal alcohol effects.

Topics: Animals; Animals, Newborn; Ethanol; Female; Fetal Alcohol Spectrum Disorders; Learning Disabilities; Male; Neuroprotective Agents; Piperidines; Pregnancy; Rats; Rats, Sprague-Dawley

1. The aim of this study was to analyse the effects of eliprodil, a noncardiac drug with neuroprotective properties, on the cardiac repolarisation under in vitro circumstances, under normal conditions and after the attenuation of the 'repolarisation reserve' by blocking the inward rectifier potassium current (I(K1)) current with BaCl(2). 2. In canine right ventricular papillary muscle by applying the conventional microelectrode technique, under normal conditions, eliprodil (1 microm) produced a moderate reverse rate-dependent prolongation of the action potential duration (7.4+/-1.5, 8.9+/-2.1 and 9.9+/-1.8% at cycle lengths of 300, 1000 and 5000 ms, respectively; n=9). 3. This effect was augmented in preparations where I(K1) was previously blocked by BaCl(2) (10 microm). BaCl(2) alone lengthened APD in a reverse frequency-dependent manner (7.0+/-1.3, 14.2+/-1.6 and 28.1+/-2.1% at cycle lengths of 300, 1000 and 5000 ms, respectively; n=8). When eliprodil (1 microm) was administered to these preparations, the drug induced a marked further lengthening relative to the APD values measured after the administration of BaCl(2) (12.5+/-1.0, 17.6+/-1.5 and 20.5+/-0.9% at cycle lengths of 300, 1000 and 5000 ms, respectively; n=8). 4. In the normal Langendorff-perfused rabbit heart, eliprodil (1 microm) produced a significant QT(c) prolongation at 1 Hz stimulation frequency (12.7+/-1.8%, n=9). After the attenuation of the 'repolarisation reserve' by the I(K1) blocker BaCl(2) (10 microm), the eliprodil-evoked QT(c) prolongation was greatly enhanced (28.5+/-7.9%, n=6). In two out of six Langendorff preparations, this QT(c) lengthening degenerated into torsade de pointes ventricular tachycardia. 5. Eliprodil significantly decreased the amplitude of rapid component of the delayed rectifier potassium current (I(Kr)), but slow component (I(Ks)), transient outward current (I(to)) and I(K1) were not considerably affected by the drug when measured in dog ventricular myocytes by applying the whole-cell configuration of the patch-clamp technique. 6. The results indicate that eliprodil, under normal conditions, moderately lengthens cardiac repolarisation by inhibition of I(Kr). However, after the attenuation of the normal 'repolarisation reserve', this drug can induce marked QT interval prolongation, which may result in proarrhythmic action.

Topics: Action Potentials; Animals; Arrhythmias, Cardiac; Barium Compounds; Chlorides; Dogs; Electrocardiography; Electrophysiology; Female; Heart; In Vitro Techniques; Male; Membrane Potentials; Microelectrodes; Neuroprotective Agents; Papillary Muscles; Patch-Clamp Techniques; Piperidines; Potassium Channel Blockers; Potassium Channels, Inwardly Rectifying; Rabbits

The exact site(s) and the molecular mechanism(s) by which ethanol inhibits the activity of NMDA receptors in the brain have so far not been identified although the involvement of several NMDA receptor modulatory sites activated by glycine, Mg2+, Zn2+, polyamines and red-ox agents has been suggested. In this study we investigated the effects of spermidine, a polyamine site agonist, on NMDA-induced neurotoxicity and its ability to modulate the inhibitory action of ethanol on neurotoxicity produced by the maximal neurotoxic concentration of NMDA as measured by the MTT assay in rat cerebellar granule cells. This assay measures the enzymatic activity in mitochondria and/or endosome/lysosome compartment that closely correlates with the cell viability. Spermidine dramatically potentiated NMDA-induced responses both at nontoxic and maximally neurotoxic NMDA concentrations. Ethanol, as expected, concentration-dependently inhibited the maximal neurotoxicity produced by NMDA. The potentiating effect of spermidine observed at nontoxic concentrations of NMDA was not altered by ethanol evidenced by the fact that the EC(50) value for spermidine was not significantly changed in the presence of ethanol. This suggests that ethanol and spermidine produce their effects by acting at different sites within the NMDA receptor complex. In contrast, the inhibitory effect of ethanol on the maximally neurotoxic action of NMDA was significantly reduced by spermidine in a concentration-dependent manner, suggesting that the spermidine enhancement of NMDA receptor function in this situation is more potent and is able mask the inhibitory action of ethanol on other sites within the NMDA receptor.

Topics: Analysis of Variance; Animals; Cell Survival; Cells, Cultured; Cerebellum; Dose-Response Relationship, Drug; Drug Interactions; Ethanol; N-Methylaspartate; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Spermidine

Dopamine (DA) receptor blockade induces catalepsy in rats which increases in strength upon retesting. This increase in catalepsy represents a form of sensitization which has been shown to be completely context dependent. Sensitization of catalepsy therefore represents a good model for studying the neurobiological mechanisms underlying the interaction between the cellular effect of a drug (DA-receptor blockade) and the context. This study investigated whether glutamatergic mechanisms are involved in the development of sensitization. Rats were treated with either haloperidol or haloperidol plus an N-methyl-D-aspartate (NMDA) receptor antagonist. Haloperidol consistently induced catalepsy which developed sensitization upon retesting. Co-administration of D-CPPene (5 mg/kg and 10 mg/kg, i.p.), eliprodil (30 mg/kg, i.p.) or Ro 25-6981 (15 mg/kg, i.p.) did not have any effect on sensitization, although all three drugs exerted some anticataleptic effects. When sensitization developed under haloperidol plus NMDA receptor antagonist, the sensitized response was expressed only in the presence of the NMDA receptor antagonist. This strongly suggests that the NMDA receptor antagonists represent contextual stimuli to which catalepsy has been conditioned, and this implies that the expression of sensitization has been rendered state-dependent.

Topics: Animals; Conditioning, Classical; Drug Interactions; Excitatory Amino Acid Antagonists; Haloperidol; Male; Phenols; Piperazines; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, Dopamine; Receptors, N-Methyl-D-Aspartate

NMDA receptor antagonists have been reported to affect learned behaviors conditioned with abused drugs, with the outcome dependent, in part, on the class of NMDA receptor antagonist used. The present study tested the ability of various site-selective NMDA receptor antagonists to modify cocaine-conditioned motor activity. Two procedures were used for independently assessing drug effects on spontaneous activity and expression of cocaine-conditioned behavior. In the conditioning experiments, rats were administered i.p. injections of cocaine (30 mg/kg) or saline paired with distinctive environments. Spontaneous horizontal activity was dose-dependently enhanced by dizocilpine (0.03-0.3 mg/kg) and memantine (1-30 mg/kg), but not by D-CPPene (3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphonic acid; SDZ EAA 494; 1-10 mg/kg), ACEA-1021 (5-nitro-6,7-dichloro-1,4-dihydro-2, 3-quinoxalinedione; 3-56 mg/kg), or eliprodil (3-30 mg/kg). Higher doses of memantine, D-CPPene (1-10 mg/kg), eliprodil (3-30 mg/kg), or ACEA-1021 reduced vertical activity. Following five cocaine-environment pairings, rats displayed significant increases in motor activity when exposed to the cocaine-paired environment. The following antagonists were administered prior to the conditioning test: dizocilpine (MK-801; 0.03-0.1 mg/kg), memantine (1-10 mg/kg), D-CPPene (0.3-3 mg/kg), ACEA-1021 (3-10 mg/kg), and eliprodil (1-10 mg/kg). Of these, memantine, ACEA-1021 and, to the lesser degree, eliprodil attenuated expression of cocaine-conditioned motor activity at doses that did not significantly affect spontaneous motor activity. These results show that cocaine-conditioned behaviors can be selectively modulated by some, but not all, NMDA receptor antagonists.

Topics: Animals; Cocaine; Conditioning, Operant; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Male; Memantine; Motor Activity; Piperazines; Piperidines; Quinoxalines; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate

Current perspectives on the clinical use of NMDA receptor antagonists infer repeated administration schedules for the management of different pathological states. The development of tolerance and cross-tolerance between different NMDA receptor antagonists may be an important factor contributing to the clinical efficacy of these drugs. The present study aimed to characterize the development of tolerance and cross-tolerance to the ability of various site-selective NMDA receptor antagonists to produce a decrement of operant responding (multiple extinction 9 s fixed-interval 1-s schedule of water reinforcement). Acute administration of D-CPPen (SDZ EAA 494; 1-5.6 mg/kg), dizocilpine (MK-801; 0.03-0.3 mg/kg), memantine (0.3-17 mg/kg), ACEA-1021 (10-56 mg/kg), and eliprodil (1-30 mg/kg) differentially affected operant responding. Both increases and decreases in response rates and accuracy of responding were observed. Repeated preexposure to D-CPPen (5.6 mg/kg, once a day for 7 days) attenuated a behavioral disruption produced by an acute challenge with D-CPPen or ACEA-1021, but potentiated the effects of dizocilpine, memantine, and eliprodil. Based on the present results, one can suggest that the repeated administration of a competitive NMDA receptor antagonist differentially affects the functional activity of various sites on NMDA receptor complex.

Topics: Animals; Conditioning, Operant; Depression, Chemical; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Tolerance; Excitatory Amino Acid Antagonists; Male; Memantine; Piperidines; Psychomotor Performance; Rats; Rats, Wistar; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate; Reinforcement Schedule; Water

A short synthesis of the NMDA receptor antagonist (rac)-Eliprodil (9) and its resolution into the enantiomers by chiral HPLC is described. The enantiomers (R)-9 and (S)-9 were found to exhibit markedly different affinities for NR2B subunit containing NMDA receptors.

Topics: Excitatory Amino Acid Antagonists; Piperidines; Receptors, N-Methyl-D-Aspartate; Stereoisomerism

Current symptomatic treatment for Parkinson's disease is based largely on dopamine-replacing agents. The fact that long-term treatment with these drugs is characterized by many side effects has lead to widespread interest in nondopaminergic therapies. To date, however, it has proved difficult to devise a nondopaminergic therapy with significant antiparkinsonian efficacy when administered as monotherapy. Overactivity of the striatolateral pallidal pathway, the "indirect" striatal output pathway, is thought be responsible for the generation of parkinsonian symptoms. Indeed, it has been suggested that selective reduction in the activity of the "indirect" pathway may be achieved by blockade of NR2B-containing NMDA receptors. In the present study, we demonstrate that selective blockade of NR2B-containing NMDA receptors with the polyamine antagonists ifenprodil and eliprodil causes a significant increase in locomotor activity in the reserpine-treated rat model of Parkinson's disease (30 mg/kg ifenprodil, 221.2 +/- 54 mobile counts compared to vehicle, 19.6 +/- 6.87, P < 0.001). Additionally, we show that, subsequent to dopamine depletion, the ability of ifenprodil to bind to the polyamine site and inhibit binding of the NMDA channel blocker [3H] MK-801 is increased fourfold (IC50 3.7 +/- 0.4 microM compared to vehicle, IC50 14.3 +/- 2.34 microM, P < 0.01). We suggest that ifenprodil selectively targets the polyamine site on overactive NR2B-containing NMDA receptors. Thus, we propose that NR2B-selective NMDA receptor antagonists may prove useful in the treatment of Parkinson's disease.

Topics: Animals; Antiparkinson Agents; Binding, Competitive; Corpus Striatum; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Male; Parkinson Disease, Secondary; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Reserpine

To examine the potential of eliprodil-a neuroprotective agent with a high affinity for sigma-receptors-to promote myelination in neuron-oligodendrocytes cocultures.. Remyelination is one of the major therapeutic issues in MS. Because neuronal integrity is required for CNS myelination, the authors postulated that neuroprotective molecules might favor myelination.. Two experimental culture conditions were compared: standard medium Bottenstein and Sato ([B-S] medium) and a medium depleted of both thyroid hormones and progesterone (depleted [D] medium). Myelination was quantified by counting the number of myelinated internodes, identified immunocytochemically with an antimyelin basic protein (anti-MBP) antibody.. The authors first confirmed that in D medium myelination was reduced by a factor of 3.5 compared with cultures maintained in B-S medium. Under both culture conditions, addition of 10(-6) M eliprodil did not modify significantly the total number of either microtubule associated protein-2-positive neurons or MBP-positive oligodendrocytes. However, eliprodil induced a twofold (p < 0.01) increase in myelination when added to B-S medium, and a 4.7-fold (p < 0.0001) increase when added to D medium.. Although the molecular mechanism mediating the effect of the sigma-receptor agonist on myelination remains to be elucidated, these results strongly suggest that neuroprotective molecules may be of therapeutic interest in demyelinating diseases such as MS.

Topics: Animals; Axons; Central Nervous System; Coculture Techniques; Drug Evaluation, Preclinical; Forecasting; Mice; Multiple Sclerosis; Myelin Sheath; Neurons; Neuroprotective Agents; Oligodendroglia; Piperidines; Receptors, sigma; Stimulation, Chemical; Triiodothyronine

The discovery that glutamate's activity at the N-methyl-D-aspartate (NMDA) receptor is positively modulated by glycine and polyamines has led to a new pharmacological strategy that NMDA receptor-mediated events could be antagonized indirectly at the strychnine-insensitive glycine co-agonist site (glycine(B) receptor) and the polyamine modulatory site. Recently we demonstrated that ifenprodil and L-701,324 (7-chloro-4-hydroxy-3(3-phenoxy)phenyl-2(H)quinoline), polyamine and glycine, receptor antagonists, respectively, at subeffective doses markedly increased after-discharge threshold (ADT) when applied together in amygdala-kindled rats. Because ifenprodil and its derivative, eliprodil, exhibit different affinities for NMDA receptors composed of different subunits, our current question was whether a combination of eliprodil and the glycine, receptor antagonist, L-701,324, would produce a super-additive anticonvulsant action. In addition, we examined the combined treatment of eliprodil with a competitive NMDA receptor antagonist CGP 40116 (D-(E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid) in the kindling model. Eliprodil alone (10-40 mg/kg) had no consistent ADT-increasing activity. When eliprodil was combined with an ineffective dose of L-701,324 (2.5 mg/kg), a significant rise in ADT was observed. Likewise, other measures of seizure activity such as severity and duration were modestly but significantly reduced. With respect to behavioral impairments, no signs of synergistic interaction were observed after the drug combinations. On the other hand, no anticonvulsant effects were found when CGP 40116 was administered alone at doses of 1.25-5 mg/kg or CGP 40116 1.25 mg/kg combined with eliprodil 10 mg/kg. These data suggest that combination therapy with antagonists at the polyamine and glycine sites might potentially treat therapy-resistant complex partial seizures.

Topics: 2-Amino-5-phosphonovalerate; Amygdala; Animals; Anticonvulsants; Drug Interactions; Excitatory Amino Acid Antagonists; Female; Kindling, Neurologic; Piperidines; Quinolones; Rats; Rats, Wistar; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate

To test whether eliprodil (SL 82.0715), a unique antagonist for the N-methyl-D-aspartate (NMDA) receptor, is protective in the glutamate-induced cytotoxicity model in cultured rat retinal ganglion cells (RGCs).. Two to four days after a fluorescent dye, Di-I, was injected near the superior colliculi, neonatal rats were killed, and retinal cells were dissociated and cultured. Survival of RGCs after drug treatment was assayed by counting Di-I fluorescent cells.. In rat RGCs, glutamate-induced toxicity with a mean EC50 of 10.7 microM. Only 47% of RGCs survived after a 3-day treatment with 100 microM glutamate. Studies using selective agonists and antagonists indicated that the glutamate-induced toxicity was mediated largely by the NMDA receptor. Pretreatment with eliprodil protected against such toxicity. Eliprodil exhibited a mean IC50 of 1.0 nM (log [IC50] = -9.00 +/- 0.01, mean +/- SEM, n = 3; against cell death produced by 100 microM glutamate). At 1 microM, eliprodil was maximally protective; cell survival in the presence of 100 microM glutamate challenge was 100% +/- 5% (n = 3). This protective effect of eliprodil may be related to its reduction (by 78%) of NMDA-induced currents recorded under patch-clamp recording in these cells.. Eliprodil is protective against glutamate cytotoxicity in retinal neurons. It may be a useful novel compound for the treatment of retinopathies including glaucoma in which excitotoxicity has been implicated.

Topics: Animals; Cell Death; Cells, Cultured; Drug Combinations; Electric Conductivity; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Female; Glutamic Acid; Glycine; Male; N-Methylaspartate; Neuroprotective Agents; Piperidines; Rats; Rats, Sprague-Dawley; Retinal Ganglion Cells

To evaluate whether eliprodil (SL82.0715), a NR2B-selective N-methyl-D-aspartate (NMDA) antagonist, is protective of retina subjected to an excitotoxic or ischemic insult.. To evaluate protection against retinal excitotoxicity, eliprodil was administered intraperitoneally before and after the injection of NMDA (5 microl, 20 nmol) into the vitreous of rats. Integrity of the retina was assessed by counting cells in the retinal ganglion cell layer (GCL) and measuring choline acetyltransferase (ChAT) activity. In a subsequent experiment, total retinal ischemia, as measured by a cessation of electroretinographic (ERG) activity, was induced in anesthetized rabbits by elevating intraocular pressure above systolic blood pressure for 65 minutes. After ischemia, recovery of ERG activity was assessed at 24 and 48 hours in animals treated with vehicle or eliprodil (1.0-10.0 mg/kg).. Intravitreal NMDA injection resulted in a dose-related decrease in cells of the GCL and in ChAT activity. Eliprodil administered intraperitoneally at 10 mg/kg completely prevented the loss of ChAT and the loss of cells in the GCL. Twenty-four hours after retinal ischemia, A and B waves of vehicle-treated animals were suppressed by 60% to 70%. Eliprodil administered intraperitoneally at 10 mg/kg ameliorated the A- and B-wave depression throughout the 48-hour experiment.. Eliprodil is neuroprotective of retinae subjected to either an excitotoxic or ischemic challenge and may be useful for treating a variety of retinal and optic nerve head disorders.

Topics: Animals; Choline O-Acetyltransferase; Electroretinography; Injections; Injections, Intraperitoneal; Ischemia; N-Methylaspartate; Neuroprotective Agents; Neurotoxins; Piperidines; Rats; Rats, Long-Evans; Retina; Retinal Ganglion Cells; Retinal Vessels; Vitreous Body

Several reports have indicated that N-methyl-D-aspartate (NMDA) receptor antagonists prevent the development of analgesic tolerance to opiates. Some effects of opiates, such as their discriminative stimulus effects, are known to be more resistant to tolerance induction. In this study, adult male Long-Evans rats were trained to discriminate 3.2 mg/kg of s.c. morphine from water (vehicle) using a standard, two-lever fixed ratio 10 schedule of food reinforcement. Subsequently, repeated morphine treatment (20 mg/kg; 14 days b.i.d.) was administered, which induced tolerance-like rightward shifts in the dose-effect curves for both morphine's discriminative stimulus and response rate-suppressing effects. Withdrawal-induced, response rate reductions indicative of behavioral dependence appeared as well. Separate groups were then treated repeatedly with a combination of morphine or its vehicle and one of the following competitive or noncompetitive NMDA antagonists: dizocilpine (0.1 mg/kg i.p.), 3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphonic acid (D-CPPene; 3 and 5.6 mg/kg i.p.), eliprodil (17.3 mg/kg i.p.), or R(+)-3-amino-1-hydroxy-2-pyrrolidone [(+)-HA-966; 10 mg/kg i.p.]. The development of tolerance to morphine's stimulus effects was attenuated by eliprodil and the higher dose of D-CPPene, but not by dizocilpine, the lower dose of D-CPPene, nor R(+)-3-amino-1-hydroxy-2-pyrrolidone. All antagonists prevented the induction of tolerance to morphine's response rate effects. Dizocilpine and D-CPPene (5.6 mg/kg) appeared to prevent the induction of behavioral dependence as well. NMDA antagonists can prevent tolerance to the discriminative stimulus effects of morphine, and perhaps to its behavioral dependence effects, but their site of action on the NMDA receptor complex confers a different ability to do so.

Topics: Animals; Discrimination Learning; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Tolerance; Excitatory Amino Acid Antagonists; Male; Morphine; Narcotics; Piperazines; Piperidines; Pyrrolidinones; Rats; Rats, Long-Evans; Receptors, N-Methyl-D-Aspartate

This study characterised the pharmacology of [3H]-ifenprodil binding to the polyamine binding sites (PBS) on the N-methyl-D-aspartate (NMDA) receptor channel complex on human retinas. These data were correlated with the known neuroprotective effects of ifenprodil and eliprodil.. Specific binding of [3H]-ifenprodil (under sigma site blockade) was investigated using human retinal homogenates and radioligand binding techniques. Scatchard and competition analyses were utilised to define the pharmacology of the [3H]-ifenprodil binding sites.. Specific binding of [3H]-ifenprodil comprised 73% (SEM 3%) of total and reflected interaction with two affinity sites (Kds = 0.39 and 4.3 microM) of different densities (Bmax = 14.4 and 105 pmol/mg protein) (n = 5). The rank order of affinity of compounds competing for [3H]-ifenprodil binding to the high affinity PBS was: ifenprodil > eliprodil > arcaine > spermine > diaminodecane > spermidine > putrescine >> MK-801 (n = 3-7). However, [3H]-ifenprodil binding was minimally inhibited by glutamate, NMDA, and kainate.. These studies have shown, for the first time, the presence of specific [3H]-ifenprodil binding sites in the human retina with pharmacological characteristics of PBS associated with the NMDA receptor ionophore complex. The neuroprotective effects of eliprodil and ifenprodil may, in part, be mediated via these [3H]-ifenprodil labelled sites.

Topics: Aged; Aged, 80 and over; Biguanides; Binding Sites; Excitatory Amino Acid Antagonists; Humans; N-Methylaspartate; Neuroprotective Agents; Piperidines; Polyamines; Receptors, N-Methyl-D-Aspartate; Retina

The N-methyl-D-aspartate (NMDA) subtype of glutamate receptor is one pathway through which excessive influx of calcium has been suggested to trigger ischemia-induced delayed neuronal death. NMDA receptors are heterooligomeric complexes comprised of both NR1 and NR2A-D subunits, in various combinations. NR2B-containing NMDA complexes exhibit larger, more prolonged conductances than those lacking this subunit. We tested the ability of the non-competitive, NR2B-selective NMDA antagonist eliprodil to (a) protect synaptic transmission in in vitro hippocampal slices from hypoxia, and (b) reduce ischemic delayed neuronal death in hippocampal organotypic slice cultures. Eliprodil markedly improved the recovery of Schaffer collateral-CA1 excitatory postsynaptic potentials following a 15 min hypoxic insult, with an EC50 of approximately 0.5 microM. In contrast to this functional protection, eliprodil did not reduce delayed death of CA1 pyramidal neurons in organotypic hippocampal slice cultures treated with severe hypoxia plus hypoglycemia, though it did potently protect CA3 pyramidal neurons in the same cultures. These data indicate that NMDA receptors containing NR2B subunits may play a role in long-term recovery of hippocampal synaptic function following ischemia/hypoxia. Furthermore, the selective protection of CA3, but not CA1, pyramidal neurons suggests that NR2B-containing NMDA receptors may preferentially contribute to an excitotoxic component of ischemia-induced delayed neuronal death.

Topics: Animals; Excitatory Amino Acid Antagonists; Hippocampus; Hypoxia; In Vitro Techniques; Ischemia; Male; N-Methylaspartate; Neuroprotective Agents; Piperidines; Pyramidal Cells; Rats; Rats, Sprague-Dawley

Glutamate stimulation of N-methyl-D-aspartate (NMDA) receptors results in release of nitric oxide which may mediate the effects of NMDA receptor stimulation and/or may result in feedback inhibition of the presynaptic neuron. Results of a previous study showed that nitric oxide synthase (NOS) inhibitors blocked dizocilpine-induced behavior in mice. In the present study, NOS inhibitors were tested in combination with phencyclidine (PCP), a drug which typically dose-dependently disrupts prepulse inhibition of the acoustic startle response in rats. Alone, NOS inhibitors and promoters do not affect prepulse inhibition; however, when tested in combination with PCP, the NOS inhibitors, L-NOARG, 7-nitroindazole and arcaine--but not the NR2B-selective polyamine site NMDA antagonist, eliprodil--attenuated PCP-induced disruption of prepulse inhibition of the acoustic startle response. These effects are similar to those produced by many atypical antipsychotics and suggests that this class of drugs should be investigated further for their potential utility as antipsychotics and as treatments for PCP abuse.

Topics: Acoustic Stimulation; Animals; Biguanides; Biogenic Polyamines; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Indazoles; Inhibition, Psychological; Male; Nitric Oxide Synthase; Nitroarginine; Phencyclidine; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Reflex, Startle

We have previously demonstrated that a lateral fluid percussion-induced traumatic lesion of the right parietal cortex can lead to a deficit in a conditioned freezing response and that this deficit can be attenuated by both pre- and postlesion administration of the NMDA receptor antagonist dizocilpine. In the present study, we investigated the effects of eliprodil, a noncompetitive NMDA receptor antagonist acting at the polyamine modulatory site, which also acts as a Ca2+ channel blocker, on the trauma-induced conditioned freezing deficit. Eliprodil produced a 50% reduction in this deficit when administered as three 1 mg/kg injections i.v. at 15 min, 6 h, and 24 h following the lesion. Approximately the same degree of protection was afforded when 2 x 1.5 mg/kg were administered 6 and 24 h and equally at 12 and 24 h after surgery (56% and 59%, respectively). A single treatment (3 mg/kg) at 24 h was ineffective against the deficit. The protection afforded with treatment at 6 and 24 h after lesion was dose dependent, with a minimal active dose of 2 x 0.75 mg/kg. These data complement those previously published on the ability of eliprodil to reduce lesion volume following traumatic brain injury and show, in addition, that the neuroprotective effect has functional consequences.

Topics: Analysis of Variance; Animals; Brain Injuries; Cognition Disorders; Conditioning, Classical; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Fear; Male; Neuroprotective Agents; Parietal Lobe; Piperidines; Rats; Rats, Sprague-Dawley; Time and Motion Studies; Time Factors

The purpose of the present study was to evaluate in vivo the effect of a non competitive antagonist of the NMDA receptor, eliprodil, on the size of a focal ischaemic insult and on its temporal evolution in a rat model, using a spin-echo diffusion magnetic resonance imaging multislice technique. Rats were either injected with 1 mg/kg i.v. of eliprodil or with the vehicle only (placebo) 5 min after middle cerebral artery occlusion, or not injected (controls). Ten coronal slices were acquired every hour, up to 7 h after occlusion of the artery, and the volume of hyperintense signals was measured at each time point and for each animal. Diffusion magnetic resonance images revealed that the administration of eliprodil reduced significantly (by 50% or more) the volume of ischaemia, up to 7 h after occlusion, particularly in the cortex of the ipsilateral hemisphere. The results show the potential efficacy of eliprodil to reduce the cerebral ischaemic volume after arterial occlusion, thus confirming the interest of glutamate receptor antagonists in the treatment of ischaemia.

Topics: Animals; Brain Ischemia; Excitatory Amino Acid Antagonists; Magnetic Resonance Imaging; Male; Multivariate Analysis; Piperidines; Radiography; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

Effects of noncompetitive and competitive NMDA receptor antagonists have been repeatedly characterized using place conditioning models. The present study aimed to characterize the effects in mice of another NMDA receptor antagonist acting at polyamine binding site, eliprodil. Five-day conditioning with eliprodil (1-30 mg/kg, i.p.) resulted in a dose-dependent avoidance of an eliprodil-paired compartment during post-conditioning tests. These effects were: (i) observed both with eliprodil and without drug, and (ii) less pronounced in individually housed mice subjected to repeated social defeats and mild footshocks prior to and during the conditioning period (compared to group-housed and individually housed nonstressed mice). In a parallel set of experiments, the effects of dizocilpine (MK-801; 0.03-0.3 mg/kg, i.p.) were evaluated using the same study design as for eliprodil. Conditioned place preference was established with the dizocilpine dose of 0.3 mg/kg and this effect was not affected by housing/stressing or drug exposures during the test.

Topics: Animals; Behavior, Animal; Conditioning, Psychological; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Housing, Animal; Injections, Intraperitoneal; Male; Mice; Mice, Inbred Strains; Piperidines; Receptors, N-Methyl-D-Aspartate; Social Environment; Stress, Physiological

Between 1993 and 1996, a total of 452 patients were entered into a randomized trial evaluating eliprodil (a non-competitive NMDA receptor antagonist) in patients suffering from severe head injury. The primary efficacy analysis concerned the Glasgow Outcome Score (GOS), six months after randomization. This outcome was classified into three ordered categories: good recovery; moderate disability, and the worst category made up by combining severe disability, vegetative state and dead. A sample size calculation was performed prior to the commencement of the study, using a formula which depends on the anticipated proportions of patients in the three different outcome categories, the proportional odds assumption and on the relationship between outcome and prognostic factors such as Glasgow Coma Score at entry. Owing to uncertainty about the influence of prognostic factors, and about the proportion of patients in the three GOS categories, a blinded sample size review was planned. This review was performed on the basis of the first 93 patients to respond, and this led to an increase in the sample size from 400 to 450. In this paper the pre-trial simulations showing that the type I error rate would be influenced and the power would be preserved will be presented, and the implementation of the procedure will be described.

Topics: Craniocerebral Trauma; Glasgow Coma Scale; Humans; Models, Statistical; Piperidines; Prognosis; Randomized Controlled Trials as Topic; Receptors, N-Methyl-D-Aspartate; Sample Size; Treatment Outcome

[3H]TCP and [3H]ifenprodil binding to N-methyl-D-aspartate (NMDA) receptors in rat forebrain membranes was used to compare the inhibition of haloperidol and trifluperidol with that of ifenprodil and eliprodil. In the [3H]TCP binding assay, inhibition curves of ifenprodil, eliprodil, haloperidol and trifluperidol revealed two affinity states in the presence of glutamate, glycine and spermidine. The potency of these agents to inhibit the high-affinity fraction of the binding agreed with the results of other studies investigating their potency to block glutamate-induced current at recombinant NR1a/NR2B NMDA receptors expressed in Xenopus oocytes. These agents also inhibited [3H]ifenprodil binding in a biphasic manner, whether in the absence or the presence of either the sigma site ligand GBR-12909 or spermidine. Spermidine reduced the fraction of high-affinity sites labeled with [3H]ifenprodil. The only alteration in the affinity was a decrease in the IC50 value of haloperidol to inhibit the high-affinity fraction of [3H]ifenprodil binding. GBR-12909 also reduced the fraction of [3H]ifenprodil sites inhibited by these compounds with high affinity, with no change in the affinity for either fraction. These data suggest that spermidine is neither a competitive antagonist at the fraction of the binding inhibited by these agents with high affinity, nor is this fraction of the binding to sigma sites. Haloperidol and trifluperidol represent a new class of agent that interacts at a site that is labeled by [3H]ifenprodil as well as [3H]TCP in rat brain membranes and that closely reflects ifenprodil's voltage-independent site on the recombinant NR1a/NR2B subtype of the NMDA receptor.

Topics: Animals; Binding, Competitive; Brain; Cell Membrane; Female; Haloperidol; Illicit Drugs; Kinetics; Oocytes; Phencyclidine; Piperidines; Radioligand Assay; Rats; Receptors, N-Methyl-D-Aspartate; Recombinant Proteins; Trifluperidol; Xenopus

We have studied the effects of a variety of N-methyl-D-aspartate (NMDA) antagonists acting at different sites of the NMDA receptor complex on NMDA-induced currents in Xenopus oocytes expressing heteromeric NR1A/NR2 and NR1A/NR2B receptors. The polyamine site antagonists eliprodil (IC50 = 3.0 microM) and ifenprodil (IC50 = 0.27 microM) antagonized NMDA responses at NR1A/NR2B receptors but not at NR1A/NR2A receptors (IC50 > 100 microM). The channel blockers dizocilpine, memantine and phencyclidine (PCP) were equally potent antagonists at both receptor subtypes whereas dextromethorphan was four times more potent at NR1A/NR2A receptors. The glycine site antagonists L-689,560 and 7-Cl-kynurenate were 10 times more potent at NR1A/NR2A than at NR1A/NR2B receptor subtypes. The selectivity of eliprodil and ifenprodil for the NR1A/NR2B receptor subtype may, at least partially, explain their favorable side effects profile.

Topics: Animals; Binding Sites; Electric Conductivity; Excitatory Amino Acid Antagonists; Female; Patch-Clamp Techniques; Piperidines; Rats; Receptors, N-Methyl-D-Aspartate; Xenopus

We have investigated, by using the whole-cell patch-clamp technique, the Ca2+ channel antagonist properties of eliprodil in cultured cerebellar granule cells which are known to express L-, N-, P- as well as Q- and R-type Ca2+ channels. Eliprodil maximally antagonized 50% of the voltage-dependent Ba2+ current with an IC50 of 4 microM. omega-Conotoxin-GVIA (3.2 microM) and omega-agatoxin-IVA (0.5 microM) blocked 28 and 43% of the current, respectively. When eliprodil (30 microM) was added to omega-conotoxin-GVIA or omega-agatoxin-IVA the magnitude of the maximal inhibition was identical to that obtained with eliprodil alone confirming a full blockade by eliprodil of N-, P- and Q-type Ca2+ channels. The L-type channel antagonist nimodipine (10 microM) blocked 24% of the current; this blockade was fully additive to that of eliprodil, indicating that the nimodipine-sensitive component of the current is eliprodil-insensitive. In the presence of eliprodil and nimodipine a residual Cd2+ sensitive current (25%), identified as the R-type current, remained unblocked. We conclude that in cerebellar granule neurons R- and L-type Ca2+ channels are insensitive to eliprodil. The nimodipine-sensitive channels present in cerebellar granule neurons may represent a neuronal subtype of L channels distinct from that (eliprodil-sensitive/nimodipine-sensitive) present in cortical or hippocampal neurons.

Topics: Animals; Barium; Calcium Channel Blockers; Calcium Channels; Cells, Cultured; Cerebellum; Drug Interactions; Neurons; Nimodipine; omega-Agatoxin IVA; omega-Conotoxin GVIA; Patch-Clamp Techniques; Peptides; Piperidines; Rats; Spider Venoms

Ifenprodil is an atypical N-methyl-D-aspartate (NMDA) receptor antagonist that selectively blocks receptors containing the NR2B subunit. It has been proposed that ifenprodil may act at a stimulatory polyamine site on NMDA receptors, although interactions between ifenprodil and polyamines are non-competitive. NMDA receptors are also inhibited by extracellular protons, and an interaction between protons and polyamine stimulation has been described. Using voltage-clamp recording of recombinant NR1/NR2B receptors expressed in oocytes, ifenprodil inhibition was found to be pH sensitive with a smaller inhibition at alkaline pH. Similar effects of pH were seen on inhibition by nylidrin, eliprodil, and haloperidol, which are thought to act at the ifenprodil binding site. The pH sensitivity of ifenprodil block occurs at NR1B/NR2B as well as NR1A/NR2B receptors, suggesting that it is not influenced by the exon-5 insert that is present in NR1B but absent in NR1A. Protons may directly affect the ifenprodil binding site or may alter the coupling of ifenprodil binding to inhibition of channel gating.

Topics: Animals; Excitatory Amino Acid Antagonists; Haloperidol; Hydrogen-Ion Concentration; Neuroprotective Agents; Nylidrin; Oocytes; Patch-Clamp Techniques; Piperidines; Receptors, N-Methyl-D-Aspartate; Xenopus laevis

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

The ethanol-like discriminative stimulus properties of a novel NMDA glycine receptor antagonist, L-701,324 ((7-chloro-4-hydroxy-3-(3-phenoxy)phenyl-2-(1H)-quinolone), a polyamine receptor antagonist, eliprodil, and a non-competitive NMDA receptor antagonist, MK-801 (dizocilpine), were examined in rats trained to discriminate ethanol from vehicle in a two-lever discrimination procedure. In rats trained to discriminate ethanol from vehicle, L-701,324 and MK-801 substituted for ethanol in a dose-dependent fashion with a complete substitution noted following administration of 7.5 mg/kg L-701,324 and 0.2 mg/kg MK-801, respectively. Full substitution for ethanol was achieved with no alteration in the rate of responding. In contrast, administration of eliprodil (in doses up to 5 mg/kg) showed only a partial, but not dose-dependent, substitution for ethanol. These findings indicate that a reduction of NMDA receptor activity, produced either via a blockade of non-competitive NMDA recognition sites or of NMDA/glycine-sensitive regulatory sites, had discriminative stimulus properties that are similar to those produced by ethanol. Furthermore, the observation that the NMDA/glycine receptor antagonist, L-701,324, was a more effective substitute for ethanol than was the polyamine antagonist, eliprodil, suggests that several NMDA receptor subunits, and thus not only NMDAR2B receptor subunits, are of importance for the discriminative stimulus effects of ethanol.

Topics: Administration, Oral; Animals; Behavior, Animal; Discrimination Learning; Dizocilpine Maleate; Dose-Response Relationship, Drug; Ethanol; Excitatory Amino Acid Antagonists; Male; Piperidines; Quinolones; Rats; Rats, Sprague-Dawley; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate

Topics: Animals; Dizocilpine Maleate; Electric Stimulation; Excitatory Amino Acid Antagonists; Hippocampus; Hypoxia, Brain; In Vitro Techniques; Long-Term Potentiation; Neuronal Plasticity; Neuroprotective Agents; Piperidines; Rats; Synapses

We have studied in a well-characterized in vitro neuronal system, cultures of cerebellar granule cells, the toxicity of polyamines endogenously present in the brain: spermine, spermidine, and putrescine. Twenty-four-hour exposure of mature (8 days in vitro) cultures to 1-500 microM spermine resulted in a dose-dependent death of granule cells, with the half-maximal effect being reached below 50 microM concentration. Putrescine was moderately toxic but only at 500 microM concentration. Spermidine was tested at 50 and 100 microM concentration and its toxicity was evaluated to be about 50% that of spermine. Neuronal death caused by spermine occurred, at least in part, by apoptosis. Spermine toxicity was completely prevented by competitive (CGP 39551) and noncompetitive (MK-801) antagonists of the NMDA receptor, but was unaffected by a non-NMDA antagonist (NBQX) or by antagonists of the polyamine site present on the NMDA receptor complex, such as ifenprodil. A partial protection from spermine toxicity was obtained through the simultaneous presence of free radical scavengers or through inhibition of the free radical-generating enzyme nitric oxide synthase, known to be partially effective against direct glutamate toxicity. The link between spermine toxicity and glutamate was further strengthened by the fact that, under culture conditions in which glutamate toxicity was ineffective or much reduced, spermine toxicity was absent or very much decreased. Exposure to spermine was accompanied by a progressive accumulation of glutamate in the medium of granule cell cultures. This was attributed to glutamate leaking out from dying or dead cells and was substantially prevented by the simultaneous presence of MK-801 or CGP 39551. The present results demonstrate that polyamines are toxic to granule cells in culture and that this toxicity is mediated through the NMDA receptor by interaction of exogenously added polyamines with endogenous glutamate released by neurons in the medium. The involvement of brain polyamines, in particular spermine and spermidine, in excitotoxic neuronal death is strongly supported by our present results.

Topics: 2-Amino-5-phosphonovalerate; Animals; Apoptosis; Aspartic Acid; Butylated Hydroxytoluene; Cells, Cultured; Cerebellar Cortex; Dizocilpine Maleate; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Female; Free Radical Scavengers; Glutamic Acid; L-Lactate Dehydrogenase; Male; Nerve Tissue Proteins; Neurons; Neuroprotective Agents; Nitric Oxide Synthase; Nitroarginine; Piperidines; Putrescine; Quinoxalines; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Spermidine; Spermine; Vitamin E

In the present study, we have assessed the efficacy of eliprodil, a neuroprotective agent which blocks both the modulatory polyamine site of the NMDA receptor and neuronal voltage-sensitive calcium channels, alone or in combination with the thrombolytic agent, rt-PA, in a rat embolic stroke model using a neurological score and the volume of the infarct as endpoints. Embolization was induced by intracarotid injection of an arterial blood clot. Eliprodil, administered at the dose of 1 mg/kg, iv. 10 min and 2 h 30 after embolization, reduced the neurological deficit by 54% (P < 0.01) and the total volume of the brain lesion by 49%. Thrombolysis with rt-PA (2.5 mg/kg, as a 30 min iv infusion beginning 1 h after embolization) decreased the neurological deficit by 48% (P < 0.05) and the size of the total infarct by 55% (P < 0.05). Combined therapy greatly improved the degree of neuroprotection as assessed by neurological and histological outcomes (70% (P < 0.001) and 89% (P < 0.01) neuroprotection, respectively). These results demonstrate that the administration of a neuroprotective drug (eliprodil) or a thrombolytic agent (rt-PA) similarly reduce the volume of brain damage and the neurological deficit in a rat embolic stroke model. Combined cytoprotective therapy and thrombolysis markedly improved the degree of neuroprotection and may, thus, represent a valuable approach for the treatment of stroke in humans.

Topics: Animals; Brain Ischemia; Cerebral Infarction; Cerebrovascular Disorders; Disease Models, Animal; Fibrinolytic Agents; Hemostasis; Male; Neurologic Examination; Neuroprotective Agents; Partial Thromboplastin Time; Piperidines; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Tissue Plasminogen Activator

Activation of NMDA receptors in dissociated cerebellar granule cells reduced mitochondrial membrane potential (MMP), as measured by rhodamine 123 fluorescence in a flow cytometer. This effect was inhibited by several NMDA-receptor antagonists with the following rank order of potency: MK-801 > PCP > TCP > dextrorphan > dichlorokynurenic acid > D-AP5 > dextromethorphan. Neither spermine nor arcaine modified the NMDA-induced reduction in MMP, whereas ifenprodil and eliprodil inhibited this response in the micromolar range. The mechanism responsible for the alteration of MMP mediated by NMDA was studied. Mepacrine and dibucaine prevented the MMP reduction induced by NMDA, as did W13 (calmodulin antagonist). In contrast, this effect was not blocked by cyclooxygenase or lipooxygenase inhibitors, H7 (a protein kinase C inhibitor) or nitroarginine (nitric oxide synthase inhibitor). These data suggest a direct interaction between NMDA-receptor activation and arachidonic acid formation, and indicate that NMDA receptor-mediated effect on MMP could involve arachidonic acid.

Topics: 2-Amino-5-phosphonovalerate; Anesthetics, Local; Animals; Arachidonic Acid; Biomarkers; Cells, Cultured; Cerebellum; Dibucaine; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Flow Cytometry; Fluorescent Dyes; Glycine; Intracellular Membranes; Kynurenic Acid; Membrane Potentials; Mitochondria; N-Methylaspartate; Piperidines; Quinacrine; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Rhodamine 123; Rhodamines; Sulfonamides

The non-competitive NMDA polyamine site antagonist, eliprodil, was examined for its effects on exploratory activity in non-habituated mice and for its antiakinetic potential in reserpine-treated mice. A low dose of eliprodil (5 mg/kg) weakly stimulated locomotion in naive animals, whilst higher doses depressed rearing (20-40 mg/kg) and grooming (40 mg/kg), consistent with a sedative action. At no dose did eliprodil cause ataxia. In 24 h reserpine-treated mice, eliprodil (10-40 mg/kg) reversed akinesia, but this effect was subject to considerable inter-animal variation and was not statistically significant. Eliprodil did not alter the motor recovery elicited by the dopamine D1 agonist SKF 38393, or the dopamine D2 agonist RU 24213, and suppressed the motor stimulation induced by L-DOPA. These results indicate that eliprodil displays a far lower propensity than many other NMDA receptor antagonists for disturbing posture and gait, but lacks the essential motor stimulant action required to make it a safe and effective antiparkinsonian agent, at least in the reserpine-treated mouse model of Parkinson's disease.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Animals; Behavior, Animal; Biogenic Monoamines; Disease Models, Animal; Dopamine Agents; Dopamine Agonists; Dose-Response Relationship, Drug; Efferent Pathways; Excitatory Amino Acid Antagonists; Levodopa; Locomotion; Male; Mice; Mice, Inbred Strains; Motor Neurons; Parkinson Disease; Phenethylamines; Piperidines; Receptors, Dopamine D1; Reserpine; Sympatholytics

To evaluate the role played by nitric oxide in global cerebral ischaemia we examined the effects of 7-nitroindazole and a sodium salt of 7-nitroindazole (inhibitors of neuronal nitric oxide (NO) synthase) and NG-nitro-L-arginine methyl ester (a more general inhibitor of NO synthase) in the gerbil model of cerebral ischaemia. Four experiments were carried out. In the first experiment, animals were either sham-operated, subjected to 5 min bilateral carotid occlusion (BCAO) or administered 7-nitroindazole or NG-nitro-L-arginine methyl ester immediately after occlusion followed by three further doses at 3, 6 and 24 h post-occlusion. In the second experiment, we examined the effects of a sodium salt of 7-nitroindazole, which is more soluble than 7-nitroindazole, using the same protocol. In the third experiment, the effects of the sodium salt of 7-nitroindazole administered at 10 mg/kg at 0, 3, 6, 24, 27, 30, 33, 52, 55, 72, 75 and 78 h post-occlusion or at 0.05 mg/h for 72 h via mini-pumps were evaluated. In separate experiments, we examined the effects of three reference compounds dizocilpine (MK-801), 2, 3-dihydroxy-6-nitro-7-sulphamoyl-benz(F)-quinoxaline (NBQX) and eliprodil using the same model. Extensive neuronal death was observed in the CA1 layer of the hippocampus in 5 min bilateral carotid occluded animals 5 days after surgery. Both 7-nitroindazole and NG-nitro-L-arginine methyl ester provided significant neuroprotection (P < 0.01) against this neuronal death. The sodium salt of 7-nitroindazole showed no protection when administered up to 12 times post-occlusion, but did provide significant (P < 0.01) neuroprotection when administered via mini-pump. The neuroprotection was similar to that provided by MK-801 and eliprodil, but not as good as that observed with NBQX. These results indicate that nitric oxide plays a role in ischaemic cell death and that selective neuronal nitric oxide synthase inhibitors can protect against ischaemic brain damage.

Topics: Animals; Brain Ischemia; Disease Models, Animal; Dizocilpine Maleate; Enzyme Inhibitors; Gerbillinae; Indazoles; Male; Neuroprotective Agents; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Piperidines; Quinoxalines

The present study examined whether eliprodil (SL 82.0715), an N-methyl-D-aspartate (NMDA) receptor antagonist acting on the polyamine sites induced expression of the 70 kDa heat shock protein (HSP70) in the rat brain. Whereas the NMDA channel blocker MK801 consistently induced HSP70 in posterior cingulate and retrosplenial cortices, eliprodil had no such effects even at the highest dose (50 mg/kg, intraperitoneally), supporting the idea that injury to the cerebrocortical neurones by NMDA receptor antagonists is probably related to specific sites of the receptor. Furthermore, eliprodil, given immediately after injection of MK801, blocked the effects of MK801 on HSP70. The result is discussed in terms of high affinity of eliprodil for the sigma receptor.

Topics: Animals; Cerebral Cortex; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Female; Heat-Shock Proteins; Molecular Weight; Neurons; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, sigma

Ifenprodil and eliprodil are both non-competitive NMDA receptor antagonists which have been shown to inhibit neuronal Ca2+ channel currents. We have examined the effects of these agents on two defined subtypes of voltage-dependent Ca2+ channels and in the gerbil model of global cerebral ischaemia. Recombinantly expressed human alpha 1B-1 alpha 2b beta 1-3 Ca2+ subunits in HEK293 cells, which results in an omega-conotoxin-sensitive neuronal N-type voltage-dependent Ca2+ channel and omega-Aga IVA sensitive Ca2+ channels (P-type) in acutely isolated cerebellar Purkinje neurones were reversibly inhibited by ifenprodil and eliprodil. Human N-type Ca2+ channel currents were inhibited by ifenprodil and eliprodil with IC50 values of 50 microM and 10 microM respectively whereas P-type Ca2+ channel currents were inhibited reversibly by ifenprodil and eliprodil with approximate IC50 values of 60 microM and 9 microM respectively. Maximum current block observed for both channel subtypes was approximately 80% for both ifenprodil and eliprodil. For neuroprotection studies, animals were subjected to 5 min bilateral carotid artery occlusion with or without administration of either ifenprodil or eliprodil (5, 10 or 20 mg/kg i.p.) immediately after surgery followed by two further doses (2.5, 5 or 10 mg/kg, respectively) at 3 and 6 h post-occlusion. Both compounds provided significant protective effects against ischaemia-induced neurodegeneration in the CA1 region of the hippocampus. These results indicate that both ifenprodil and eliprodil protect against ischaemia-induced neurodegeneration when administered post-occlusion and that they also block N and P-type voltage-dependent Ca2+ channels.

Topics: Animals; Body Temperature; Brain Ischemia; Calcium Channels; Cell Line; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Gerbillinae; Hippocampus; Male; Patch-Clamp Techniques; Piperidines; Purkinje Cells; Rats; Receptors, N-Methyl-D-Aspartate

Cessation of chronic administration of orally administered large amounts of ethanol for 7 days resulted in a markedly increased frequency of audiogenic seizures in Sprague-Dawley rats. Oral administration of the novel glycine receptor antagonist, L-701,324, produced a dose-dependent (2.5 and 5.0 mg/kg; -30 min) inhibition of ethanol withdrawal signs when measured about 12 h after withdrawal of the ethanol treatment. Similarly, using the same experimental paradigm, oral administration of the specific polyamine receptor antagonist, eliprodil, caused a dose-related (2.0 and 5.0 mg/kg; -30 min) inhibition of ethanol withdrawal-induced audiogenic seizure activity. The inhibition of ethanol withdrawal seizures produced by L-701,324 and eliprodil, respectively, was obtained at doses which by themselves did not change the locomotor activity in naive Sprague-Dawley rats. The findings that L-701,324 and eliprodil are potent inhibitors of seizure activity induced by cessation of chronic ethanol administration and the fact that they, in contrast to currently available NMDA receptor antagonists, do not produce psychotomimetic and/or sedative effects, suggest that these drugs may represent a new class of therapeutically useful pharmacological agents for the treatment of ethanol withdrawal seizures. Furthermore, since there is evidence that eliprodil produces its pharmacological actions through a specific inhibition of NMDAR1 and/or NMDAR2B subunits, these data may indicate that certain NMDA receptor subunits may be of particular importance for the mediation of seizure activity following the discontinuation of chronic ethanol exposure.

Topics: Acoustic Stimulation; Administration, Oral; Animals; Anticonvulsants; Central Nervous System Depressants; Dizocilpine Maleate; Ethanol; Excitatory Amino Acid Antagonists; Male; Motor Activity; Piperidines; Quinolones; Rats; Rats, Sprague-Dawley; Seizures; Substance Withdrawal Syndrome

NMDA increases the release of [14C]acetylcholine and [3H]spermidine or of [14C]GABA and [3H]dopamine from rat striatal slices. The pharmacology of these responses suggests that release of dopamine and GABA, acetylcholine, and spermidine is mediated, respectively, by three distinct NMDA receptor subtypes. IC50 values of compounds for the inhibition of dopamine and GABA release were closely matched, suggesting mediation by the same subtype. This receptor was generally more sensitive to all NMDA antagonists tested relative to that controlling acetylcholine or spermidine release (channel blockers, glycine antagonists, competitive antagonists and polyamine antagonists). The receptors controlling acetylcholine and spermidine release were characterised by lower antagonist sensitivity in general, and that controlling spermidine release was further defined by a marked insensitivity to ifenprodil, eliprodil, magnesium, dextromethorphan, dextrorphan, memantine, desipramine and polyamine spider toxins. In binding studies in which the displacement of 2 nM [3H]MK801 was studied in membranes prepared from a number of brain regions (in the presence of saturating concentrations of glutamate, glycine and spermidine) small regional differences in IC50 values were observed for a number of channel blockers, but no compound generated biphasic displacement curves that would allow masking of a particular subtype and it was not possible to detect binding components that were insensitive to memantine, dextrorphan dextromethorphan or desipramine. Ifenprodil produced biphasic displacement curves in the 1-day-old rat cortex and midbrain (with IC50 values of approximately 2 and 70 microM) and both ifenprodil and eliprodil displaced a small proportion (18%) of [3H]MK-801 with high affinity in the adult rat spinal cord. Displacement of [3H]MK801 by these compounds in all other adult brain regions (cortex, striatum, hippocampus, thalamus, pons, medulla, cerebellum) was monophasic and of low affinity. In general the subtype selectivity suggested by the release studies was not mirrored in the binding experiments, probably because of excessive heterogeneity of sites in the membrane preparations and to the subtype selectivity of [3H]MK801 itself.

Topics: Animals; Calcium Channel Blockers; Corpus Striatum; Dantrolene; Excitatory Amino Acid Antagonists; In Vitro Techniques; N-Methylaspartate; Neurotransmitter Agents; Piperidines; Radioligand Assay; Rats; Receptors, N-Methyl-D-Aspartate; Sodium Channel Blockers; Tetrodotoxin

NMDA receptor stimulation concomitantly increases the release of [14C]acetylcholine and [3H]-spermidine from rat striatal slices in vitro. The NMDA-induced release of both acetylcholine and spermidine was blocked with equal potency by the NMDA channel blocker phencyclidine (0.1-10 microM). However, certain other channel blockers, including dextromethorphan (1-100 microM), which antagonized NMDA-evoked acetylcholine release without affecting NMDA-evoked spermidine release, and dextrorphan (1-100 microM) and memantine (1-100 microM), which block NMDA-evoked acetylcholine release more potently than NMDA-evoked spermidine release, showed greater selectivity of action. As previously shown for ifenprodil, eliprodil (SL82.0715; 1-100 microM) blocked NMDA-evoked acetylcholine but not spermidine release. This selectivity is also observed for other agents interacting with the polyamine site(s) on the NMDA receptor, including arcaine (1-1,000 microM), philanthotoxin343, and argiotoxin636 (10 microM) and was also noted for desipramine (1-100 microM). The NMDA-induced release of acetylcholine and spermidine is likely to be mediated by different native NMDA receptor subtypes, and several NMDA antagonists may be candidates for a selective action at a particular NMDA receptor subtype.

Topics: Acetylcholine; Animals; Corpus Striatum; Desipramine; Dextromethorphan; Indoleacetic Acids; N-Methylaspartate; Phenols; Phenylacetates; Piperidines; Polyamines; Rats; Receptors, N-Methyl-D-Aspartate; Spermidine; Spider Venoms

Observations of sigma (sigma) receptor heterogeneity have prompted interest in identifying ligands for sigma receptor subtypes. Selective ligands for the sigma-2 are unavailable, but [3H]ifenprodil labels sigma-2 sites. Therefore, isomers and analogues of ifenprodil were compared as potential sigma-2 ligands. Threo-ifenprodil and erythro-ifenprodil had high affinity (Ki congruent to 2 nM) for sigma-2 sites; erythro-iodoifenprodil had moderate affinity (Ki congruent to 46 nM); eliprodil had lowest affinity (Ki congruent to 630 nM). Threo-ifenprodil, which has less affinity for alpha 1-adrenoceptors than erythro-ifenprodil, was slightly more selective than erythro-ifenprodil for sigma-2 sites. These results identify threo-ifenprodil as potentially useful for studies of sigma-2 receptors.

Topics: Animals; Binding, Competitive; Drug Interactions; In Vitro Techniques; Kinetics; Ligands; Male; Pentazocine; Piperidines; Rats; Rats, Inbred F344; Receptors, N-Methyl-D-Aspartate; Receptors, sigma; Stereoisomerism

Functional N-methyl-D-aspartate (NMDA) antagonists including competitive antagonists, glycine partial agonists, and use-dependent channel blockers exhibit antidepressant-like actions in preclinical models. The present study examined the effects of eliprodil (SL-82.0715), an NMDA antagonist acting at polyamine sites, in behavioral and neurochemical tests predictive of antidepressant activity. In mice, eliprodil produced a dose-dependent reduction in immobility in the forced swim test, but was inactive in the tail suspension test. Chronic treatment with eliprodil produced both a significant downregulation of beta-adrenoceptors and a reduction in the potency of glycine to inhibit [3H]5,7-dichlorokynurenic acid binding to strychnine-insensitive glycine receptors in neocortical membranes. In toto, these data indicate that like other NMDA antagonists, eliprodil possesses antidepressant-like actions in preclinical tests predictive of clinical efficacy.

Topics: Adrenergic beta-Antagonists; Adrenergic Uptake Inhibitors; Animals; Antidepressive Agents; Behavior, Animal; Biogenic Polyamines; Brain Chemistry; Down-Regulation; Excitatory Amino Acid Antagonists; Glycine; Imipramine; Kynurenic Acid; Male; Mice; Mice, Inbred C57BL; Motor Activity; Piperidines; Receptors, Glycine

This investigation studied the possible effect of different iv administration rates (bolus and infusions) of eliprodil, a new anti-ischemic agent, on the drug distribution in various body compartments. Following bolus administration of a 15-mg kg-1 dose, plasma concentrations were best fitted by a 3-compartment open model of t1/2 alpha = 14 sec, t1/2 beta = 4 min, and t1/2 gamma = 1.8 hr. Plasma and heart Cmax values were lowered by decreasing the infusion rate (the 15-mg dose was administered in 15 or 60 min) whereas brain Cmax values were not modified. In contrast, AUC values did not depend upon the rate of infusion. The present findings may have important implications in relating tissue concentrations with the desired therapeutic effect as well as with the side effects of the drug at its sites of action within brain and heart. The use of a simplified model built with plasma and tissue kinetic parameters following bolus injection allows one to predict the amount of drug present in the organs according to the mode of administration, but not the evolution of tissue to plasma ratio during the infusions.

Topics: Animals; Brain; Chromatography, High Pressure Liquid; Excitatory Amino Acid Antagonists; Infusions, Intravenous; Injections, Intravenous; Male; Models, Biological; Myocardium; Piperidines; Rats; Rats, Sprague-Dawley; Tissue Distribution

The effect of eliprodil on P-type Ca2+ channels was investigated in acutely dissociated rat Purkinje neurons, by using the whole-cell patch-clamp technique. Eliprodil inhibited in a reversible manner the omega-agatoxin-IVA-sensitive Ba2+ current elicited by step depolarizations from a -80 mV holding voltage (IC50 = 1.9 microM). The Ba2+ current showed steady-state inactivation (V1/2 = -61 mV) which was shifted toward more positive values when the intracellular Ca2+ buffering was increased. In these conditions, the potency of eliprodil was decreased (IC50 = 8.2 microM), suggesting a modulation by intracellular Ca2+ of the eliprodil blockade. The potency of eliprodil was not modified at more depolarized holding potentials and was not dependent on the frequency at which the step-depolarizations were applied (0-0.2 Hz) indicating a lack of voltage and use dependence of the eliprodil blockade. When eliprodil was applied in the patch-pipette at a concentration which causes full block when applied externally, the Ba2+ current amplitude was not affected and external application of eliprodil was still efficacious, indicating an extracellular location of the binding site. Analysis of the time course of recovery from Ca2+ channel blockade obtained by concomitant application of eliprodil with Cd2+, omega-agatoxin-IVA or fluspirilene, indicated that these later compounds did not interact with eliprodil, suggesting that eliprodil acts at a different site. These results demonstrate that eliprodil blocks P-type Ca2+ channels in cerebellar Purkinje neurons and suggest that this property may contribute to its neuroprotective activity.

Topics: Animals; Binding Sites; Cadmium; Calcium Channel Blockers; Dopamine Antagonists; Electrophysiology; Excitatory Amino Acid Antagonists; Fluspirilene; In Vitro Techniques; omega-Agatoxin IVA; Patch-Clamp Techniques; Piperidines; Purkinje Cells; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Solutions; Spider Venoms

The present investigation examined the effect of eliprodil, an atypical NMDA receptor antagonist that acts at the polyamine modulatory site, on local cerebral glucose utilization using the quantitative autoradiographic 2-[14C]deoxyglucose method in the conscious rat. Eliprodil, at doses of 3, 10 and 30 mg/kg i.p., did not increase cerebral glucose use in any of the 82 different brain regions studied. However, in some of the regions examined, local cerebral glucose utilization was slightly reduced, the most pronounced decreases being measured in some extrapyramidal, sensorimotor and limbic areas (dentate gyrus, septum, lateral habenula, amygdala). This decrease in glucose utilization was dose-dependent: no significant change was noted after 3 mg/kg i.p. of eliprodil, while 18 (at 10 mg/kg, i.p.) and 29 (at 30 mg/kg, i.p.) regions displayed a moderate (20-25%) though significant decrease in glucose use. These data demonstrate that the pattern of alterations in glucose use produced by eliprodil is different from that induced by NMDA channel blockers or competitive NMDA receptor antagonists. The fact that blockade of the polyamine modulatory site is not associated with an activation of specific limbic circuits may explain why, at neuroprotective doses, eliprodil is devoid of those unwanted side effects (including intrinsic neurotoxicity on cortical neurons) associated with NMDA channel blockers.

Topics: Animals; Biogenic Polyamines; Brain; Glucose; Male; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

Two studies examined the abuse potential of the N-methyl-D-aspartate (NMDA) non-competitive antagonist eliprodil [(+/-)-alpha-(4-chlorophenyl)-4-[(fluorophenyl)methyl]-1- piperidineethanol] by evaluating its reinforcing effects in rhesus monkeys and its phencyclidine (PCP)-like discriminative stimulus effects in rats. The monkeys were trained to self-administer PCP i.v. under a fixed ratio 10 schedule of reinforcement. After the monkeys were trained, saline, vehicle and various doses of eliprodil were substituted for PCP. The rats were trained to discriminate 3 micrograms/kg PCP from saline using a standard two-lever discrimination procedure with correct-lever responding reinforced under a fixed ratio 10 schedule of food reinforcement. After acquiring the discrimination, the rats were tested with various doses of PCP, dizocilpine and eliprodil. The self-administration study showed that eliprodil did not have reinforcing effects, since it maintained injection rates comparable to the negative controls, saline and vehicle. In the discrimination study it was found that the higher doses of PCP and dizocilpine resulted in 100% PCP-associated lever responding, whereas eliprodil occasioned no responding on the PCP-associated lever. The results from these studies suggest that eliprodil has a low potential for abuse in humans as well as providing further evidence that eliprodil produces a profile of behavioral effects unlike the PCP-site selective NMDA antagonists.

Topics: Animals; Appetitive Behavior; Brain; Discrimination Learning; Dizocilpine Maleate; Dose-Response Relationship, Drug; Female; Injections, Intravenous; Macaca mulatta; Male; Motivation; N-Methylaspartate; Phencyclidine; Piperidines; Rats; Rats, Wistar; Reinforcement Schedule; Self Administration

The effect of the non-competitive NMDA receptor antagonist eliprodil on NMDA receptor- and voltage-operated Ca2+ currents was investigated in rat cultured cortical neurons by using the whole-cell patch clamp technique. With neurons voltage-clamped at -40 mV, eliprodil reduced in a concentration-dependent manner the inward current induced by N-methyl-D-aspartate (NMDA) (10 microM) in the presence of D-serine with an IC50 of 0.67 microM (Imax = 83%). Eliprodil also blocked the total inward Ba2+ current carried in part by L- and N-type Ca2+ channels with an IC50 of 1.48 microM (Imax = 87%). These results suggest that the neuroprotective properties of eliprodil could be due to its combined ability to antagonize the NMDA receptor- and voltage-operated Ca2+ channels.

Topics: Animals; Calcium Channels; Cells, Cultured; Cerebral Cortex; Electrophysiology; Neurons; Piperidines; Rats; Receptors, N-Methyl-D-Aspartate

Ethanol (EtOH) administration is considered to elicit its reinforcing properties by stimulating dopaminergic (DA) transmission in the mesolimbic system. Accordingly, (EtOH) activates dopamine neuronal firing in the Ventro-Tegmental Area (VTA) and DA output in the nucleus accumbens. Concomitantly, EtOH reduces the firing rate of Pars Reticulata (PR) neurons which are thought to exert an inhibitory control over DA neurons. Further, chronic ingestion of EtOH produces tolerance to its sedative effects as to the depressant effect on PR neurons but no tolerance to the DA stimulating action. Moreover the NMDA antagonist MK-801, but not SL-820715, stimulates DA firing, suggesting that this effect is not a general characteristic of NMDA receptor antagonists and questioning the possibility that NMDA-receptor blockade may underlie EtOh-induced activation of DA-ergic transmission. The results indicate that activation of the mesolimbic DA tract is essential in the rewarding properties of EtOH and that neither GABA-ergic inhibition nor NMDA-receptor blockade by EtOH, are causally linked to the EtOH-induced activation of DA-ergic transmission.

Topics: Alcoholism; Animals; Aversive Therapy; Dizocilpine Maleate; Dopamine; Electrophysiology; Ethanol; gamma-Aminobutyric Acid; Glutamic Acid; Limbic System; Male; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Reward; Synaptic Transmission

The neuroprotective potential of eliprodil (SL 82.0715), an N-methyl-D-aspartate (NMDA) receptor antagonist acting at the polyamine modulatory site, in brain trauma was examined in a rat model of lateral fluid-percussion brain injury. The volume of the lesion was assessed histologically by measuring, at 7 days post-injury, the area of brain damage at 10 coronal planes. Eliprodil (10 mg/kg i.p.) when given 15 min, 6 h and 24 h after fluid percussion (1.6 atm) and then b.i.d. for the following 6 days, reduced by 60% the volume of cortical damage. A similar neuroprotection was obtained when the first administration of eliprodil was delayed by up to 12 h after the brain insult. Moreover, when the treatment with this compound was started at 18 h post-injury, cortical damage was still significantly reduced by 33%. Autoradiographic studies showed that eliprodil treatment (10 mg/kg, i.p.), initiated 15 min after the trauma, also caused a marked reduction of the loss of the neuronal marker omega 1-2 (central benzodiazepine) binding sites and of the increase in the glial/macrophage marker peripheral type benzodiazepine binding sites in the cerebral cortex. In contrast, dizocilpine (a blocker of the cationic channel coupled to the NMDA receptor) when administered 6 h and 24 h after fluid percussion and then b.i.d. for the following 6 days induced a non significant reduction of the volume of the lesion at the highest tolerated dose (0.6 mg/kg i.p.). These results demonstrate the neuroprotective activity of eliprodil in experimental brain trauma using neuropathology as an endpoint and indicate that there is a very large time window for therapeutic intervention, consistent with the delayed nature of the neuronal loss, in this condition.

Topics: Animals; Autoradiography; Benzodiazepines; Binding Sites; Brain; Brain Injuries; Dizocilpine Maleate; Drug Administration Schedule; Male; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Time Factors

The N-methyl-D-aspartate (NMDA) antagonists ifenprodil and SL-82,0715 were examined for neuroprotective efficacy against glutamate toxicity of hippocampal neurons in culture. Hippocampal cells were grown on 96-well culture plates for 2 to 3 weeks and then exposed for a 15-min period to glutamate or NMDA. Neurodegeneration was quantified 24 hr after the excitotoxin exposure, by measuring the activity of lactate dehydrogenase leaked into the culture medium by the damaged cells. Glutamate induced a concentration-dependent increase in lactate dehydrogenase that reached 3-fold the activity of control cultures. The NMDA antagonists MK-801 and AP-7 blocked this neurotoxicity when added either during or after the glutamate exposure. Ifenprodil and SL-82,0715 blocked the neurotoxicity only when added during the excitotoxin exposure. Ifenprodil was 3 times more potent than SL-82,0715 in blocking glutamate or NMDA-induced neurotoxicity. Glycine did not reverse the neuroprotective effects of these antagonists. The neuroprotective effect of ifenprodil or SL-82,0715 did not appear to result from actions at alpha-1 adrenergic or sigma receptor sites because the alpha-1 adrenergic antagonist prazosin and the sigma ligands haloperidol, 3-(3-hydroxyphenyl)-N-propylpiperidine) and 1,3-di-o-tolylguanidine) showed no neuroprotective activity. We conclude that ifenprodil and SL-82,0715 protect cultured hippocampal neurons from excitotoxic damage by antagonizing NMDA receptors.

Topics: Animals; Cells, Cultured; Culture Media; Dizocilpine Maleate; Drug Antagonism; Glutamates; Glutamic Acid; Hippocampus; L-Lactate Dehydrogenase; N-Methylaspartate; Piperidines; Rats; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

NMDA stimulated the release of endogenous or tritiated dopamine from rat striatal slices and tritiated norepinephrine from cortical and hippocampal slices. The putative polyamine antagonists ifenprodil and SL 82.0715 inhibited [3H]norepinephrine release from cortical and hippocampal slices but enhanced the basal efflux of endogenous and tritiated dopamine from striatal slices. Incubation of striatal slices in a calcium-free buffer did not ameliorate these effects suggesting that the increase in dopamine efflux was not due to a calcium-dependent release process. Superfusion of striatal slices with 10 microM of either ifenprodil, cocaine, or amphetamine resulted in a significant release of tritiated dopamine which was reversed when the slices were again superfused with non-drug-containing buffer. The release observed in the presence of 10 microM ifenprodil (7-fold increase over basal) was intermediate between that observed for cocaine (3-fold increase) and amphetamine (12-fold increase). Both ifenprodil and SL 82.0715 also blocked the uptake of [3H]dopamine into striatal synaptosomes with IC50 values of approximately 1.5 microM. This was again intermediate between the values obtained for cocaine (0.43 microM) and amphetamine (4.2 microM). These results suggest that ifenprodil and its analog SL 82.0715 may act as indirect dopamine agonists by both blocking presynaptic dopamine uptake and by directly increasing the basal efflux of dopamine.

Topics: Adrenergic alpha-Antagonists; Animals; Brain; Cocaine; Dopamine; Male; N-Methylaspartate; Norepinephrine; Piperidines; Polyamines; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate

Topics: Antipsychotic Agents; Humans; Piperidines; Psychotic Disorders; Receptors, Opioid; Receptors, sigma

Withdrawal of rats from chronic ethanol, morphine, cocaine and amphetamine resulted in a marked reduction in extracellular dopamine (DA) concentration in the ventral striatum as measured by microdialysis. Following ethanol and naloxone-precipitated morphine withdrawal, the time course of DA reduction paralleled that of the withdrawal symptomatology. On the other hand, following discontinuation of chronic cocaine, DA reduction was delayed by over 24 h but persisted for several days. After amphetamine withdrawal the fall in DA occurred more rapidly but the reduction also persisted for several days. The administration of the NMDA receptor antagonist, MK-801, to rats withdrawn from chronic ethanol, morphine or amphetamine, but not from chronic cocaine, readily reversed the fall in DA output. The reduction in extracellular DA during ethanol withdrawal was also reversed by SL 82.0715, another NMDA receptor antagonist.

Topics: Amphetamine; Animals; Cocaine; Corpus Striatum; Dizocilpine Maleate; Dopamine; Ethanol; Male; Morphine; Naloxone; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Substance Withdrawal Syndrome

The potential neuroprotective effect of seven sigma ligands has been evaluated in a mouse model of focal cerebral ischemia (induced by coagulation of the left middle cerebral artery) and compared to that of known N-methyl-D-aspartate (NMDA) antagonists. When given after the induction of cerebral ischemia, the NMDA receptor antagonists dizocilpine and CGS 19755 and the mixed NMDA antagonist/sigma ligand eliprodil (SL 82.0715) afforded very substantial protection against cortical infarction (92, 44 and 72%, at the doses of 1, 10 and 10 mg/kg, i.p., for dizocilpine, CGS 19755 and eliprodil, respectively). In contrast, none of the sigma ligands investigated--DTG, DMTG, GBR 12909, (+)- and (-)-3-PPP (up to 10 mg/kg), BMY 14802 (up to 30 mg/kg), except haloperidol at a high dose (3 mg/kg)--had neuroprotective effects.

Topics: Animals; Brain Ischemia; Cerebral Cortex; Dose-Response Relationship, Drug; Guanidines; Isoquinolines; Ligands; Male; Mice; Piperidines; Receptors, N-Methyl-D-Aspartate; Receptors, sigma

In the present study, we have examined by light and electron microscopy whether SL 82.0715, a polyamine site-directed N-methyl-D-aspartate (NMDA) antagonist, causes pathological changes in cerebrocortical neurons similar to those observed with NMDA receptor channel blockers in the rat brain. Dizocilpine (1, 2 and 5 mg.kg-1, s.c.) induced a dose-dependent vacuolization of the neuronal cytoplasm in specific neurons of the retrosplenial and posterior cingulate cortices (layers III and IV) even at the lowest dose studied, at 6 h post-injection. In contrast, SL 82.0715 (10 and 30 mg.kg-1 i.p., 6 h post-injection) did not induce such morphological alterations. These results indicate that NMDA receptor blockade is not necessarily associated with alterations of cortical neuronal morphology.

Topics: Animals; Biogenic Polyamines; Cerebral Cortex; Cytoplasm; Dizocilpine Maleate; In Vitro Techniques; Male; Microscopy, Electron; N-Methylaspartate; Neurons; Piperidines; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Vacuoles

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

Ifenprodil and SL 82.0715 are noncompetitive N-methyl-D-aspartate (NMDA) antagonists whose inhibitory actions are not explained by antagonistic effects at any of the three commonly recognized sites within the NMDA receptor complex (recognition, channel and modulatory glycine sites). We presently show that ifenprodil and SL 82.0715 antagonize the effects of NMDA via a selective action at the recently described polyamine modulatory site. Spermine and spermidine (0.5-100 microM) increase the binding of [3H]1-[1-(2-thienyl)cyclohexyl] piperidine to washed rat forebrain membranes in the presence of glutamate (10 microM). This effect is antagonized by ifenprodil and SL 82.0715 (0.1-10 microM) at concentrations which do not displace [3H]1-(2-thienyl)cyclohexyl] piperidine in the absence of added polyamine. Spermine and spermidine (up to 100 microM) do not significantly alter the binding of [3H]glycine but increase the binding of the NMDA recognition site ligand [3H](+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid. Ifenprodil and SL 82.0715 (0.1-10 microM) antagonize this effect; ((+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-10-imine maleate) or 7-chlorokynurenate (100 microM) are ineffective. In immature rat cerebellar slices, spermine and spermidine (10-1000 microM) potentiate the maximal effects of NMDA (80-160 microM) on cyclic GMP production. Spermine (100-1000 microM) reverses the antagonistic effects of ifenprodil (0.15-50 microM) but not of ((+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-10-imine acid or kynurenate on the NMDA receptor-mediated increase in cyclic GMP levels. Ifenprodil (0.01-1 microM) potently but only partially antagonizes the depolarizing effects of NMDA (10 microM) on the immature rat spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adrenergic alpha-Antagonists; Animals; Aspartic Acid; Binding Sites; Binding, Competitive; Brain; Cells, Cultured; Drug Interactions; Female; Glycine; Male; N-Methylaspartate; Phencyclidine; Piperidines; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Spermidine; Spermine; Spinal Cord

SL 82.0715 and ifenprodil are potent anti-ischemic agents, which are believed to be due to non-competitive antagonism of N-methyl-D-aspartate (NMDA). It has been proposed that SL 82.0715 and ifenprodil non-competitively antagonize the actions of NMDA by interacting as antagonists with a polyamine site associated with the NMDA/phencyclidine (PCP)/glycine complex. The present study demonstrates that the actions of SL 82.0715 and ifenprodil may also be due in part to an interaction with sigma binding sites, a property that is not shared with polyamines.

Topics: Animals; Binding, Competitive; Brain; Dopamine Agents; Kinetics; Male; Piperidines; Radioligand Assay; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, sigma; Tritium

The measurement of cortical omega 3 (peripheral-type benzodiazepine binding) site densities provides an accurate index for the detection and quantification of ischaemic brain lesions following middle cerebral artery occlusion (MCAO) in mice. Here, we have used this marker to assess the neuroprotective activity of potential anti-ischaemic drugs belonging to several chemical classes. In untreated mice, the mean infarcted volume measured 96 h after unilateral coagulation of the middle cerebral artery was 27.9 +/- 4.3 mm3 (17.5% of the hemisphere volume) and omega 3 site densities (measured by incubation with 3H-PK 11195) were increased by 107.3 +/- 4.8% (cortical homogenates) or by 81% (coronal brain sections). The administration of the anti-ischaemic agent SL 82.0715 (10 mg/kg i.p.), 5 min, 6 h and 18 h after the occlusion and then twice daily until sacrifice evoked a decrease of similar magnitude (ca. 60-70%) in the volume of the infarction and in the proliferation of omega 3 sites. The constant tissue sparing effect of SL 82.0715 allowed the examination of the window of therapeutic opportunity. A significant diminution of cortical omega 3 sites was still noted when the first administration was delayed until 3 h post-occlusion. Moreover, the protective effect of SL 82.0715 was enhanced by repeated treatment for the first 36 h but not thereafter. Based on the histological, autoradiographic and homogenate binding results obtained with SL 82.0715, we studied the protective effects of several competitive and non-competitive NMDA receptor antagonists. When administered according to the above-described standard protocol, these drugs reduced omega 3 site levels in cortical homogenates from MCAO mice in a dose-dependent manner. The dose preventing by 50% the increase in omega 3 site levels (in mg/kg i.p.) and the maximal inhibition were respectively: MK-801 (0.2, 93%); TCP (1.6, 66%); kynurenate (260, 58%); ifenprodil (7.0, 58%); SL 82.0715 (1.1, 72%); CGS 19755 (46% at 10 mg/kg); dextromethorphan (46% at 30 mg/kg). In contrast, agents acting preferentially upon sigma (sigma) opiate receptors ((+)-3PPP, 1-10 mg/kg i.p. and haloperidol, 0.3-3 mg/kg i.p.) did not provide a significant protection. In general, calcium channel blockers (nimodipine, flunarizine, verapamil, perhexiline, diltiazem) were devoid of a clear neuroprotective potential when administered at non-toxic doses after the coagulation of the middle cerebral artery. Diltiazem (3 and 10 mg/kg i.p.) provi

Topics: Animals; Calcium Channel Blockers; Cell Survival; Cyclandelate; Ischemic Attack, Transient; Male; Mice; Molecular Structure; N-Methylaspartate; Piperidines; Platelet Activating Factor; Receptors, GABA-A; Receptors, Opioid; Receptors, sigma; Vincamine

Topics: Adrenergic alpha-Antagonists; Animals; Brain Chemistry; Glutamates; Male; Piperidines; Rats; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Spermidine

Topics: Adrenergic alpha-Antagonists; Animals; Cerebellum; Cyclic GMP; Glycine; Injections; Male; Mice; Piperidines; Receptors, Amino Acid; Receptors, Cell Surface; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Serine; Time Factors

The effects of the anti-ischemic agents ifenprodil and its derivative SL 82.0715 ((+/-)-alpha-(4-chlorophenyl)-4-[(4-fluorophenyl) methyl]-1-piperidineethanol] have been analyzed in a number of models indicative of N-methyl-D-aspartate (NMDA) antagonistic potential in vitro and in vivo. Ifenprodil and SL 82.0715 potently and noncompetitively antagonize the stimulatory effects of NMDA on cyclic GMP production in immature rat cerebellar slices (IC50 values, 0.4 and 10 microM, respectively), as well as the NMDA-evoked [3H]acetylcholine release in adult rat striatal slices (IC50 values, 1.6 and 6.6 microM, respectively). Ifenprodil is 10 times more potent than (+/-)3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) but less active than the reference noncompetitive NMDA channel blockers [MK 801, ((+)-5-methyl-10,11-dihydro-5H-dibenzo-[a,d]cyclohepten-5,10-imine ], phencyclidine and 1-[1-(2-thienyl)cyclohexyl]piperidine (TCP)] in these models. Ifenprodil and SL 82.0715 partially displace (maximal displacement 40-50% at 10 microM) the NMDA receptor ligand [3H]CPP from its binding site to rat brain membranes (IC50 values, 0.1 and 0.3 microM, respectively) in a noncompetitive manner; in the micromolar range the two agents also partially displace the NMDA channel ligand [3H]TCP from its binding site to rat brain membranes, and noncompetitively antagonize the L-glutamate-induced increase in [3H]TCP binding. Ifenprodil (0.01-1 microM) partially antagonizes the depolarizing effects of NMDA on the immature rat hemisected spinal cord in vitro. In mouse cultured spinal cord neurons, ifenprodil dose-dependently antagonizes the depolarizing effects of micropressure applied NMDA. Inhibition of the effects of NMDA in this model by ifenprodil and SL 82.0715 is noncompetitive. In vivo and after systemic i.p. administration, ifenprodil and SL 82.0715 antagonize the stimulatory effects of intrastriatally dialyzed NMDA on striatal dopamine release in rats (ID50 values, 0.9 and 0.3 mg/kg, respectively), and block the harmaline-evoked increase in cerebellar cyclic GMP production in mice (ID50 values, 3 and 4 mg/kg, respectively). These results indicate that ifenprodil is a noncompetitive NMDA antagonist which has a mechanism of action distinct from either the reference competitive NMDA receptor antagonists (CPP and 2-amino-5-phosphonovalerate) or the noncompetitive NMDA channel blockers (phencyclidine, TCP and MK 801). The potent NMDA antagonistic effects of the ifenprodil c

Topics: Animals; Aspartic Acid; Brain Ischemia; Cells, Cultured; Cerebellum; Corpus Striatum; Cyclic GMP; Dopamine; Harmaline; In Vitro Techniques; Mice; N-Methylaspartate; Phencyclidine; Piperazines; Piperidines; Rats; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Spinal Cord

Recent studies have strongly implicated the excitatory neurotransmitter glutamate in the cascade of pathological mechanisms that cause neuronal loss after certain types of brain ischemia. The neurotoxic effects of glutamate are mediated, at least in global ischemia, via NMDA receptors. In the present study we have examined the effects of compounds that possess NMDA receptor antagonist properties (ifenprodil, SL 82.0715 [(+/-)-alpha-(4-chlorophenyl)-4-[(4-fluorophenyl)methyl]- 1-piperidineethanol] and 1-[1-(2-thienyl)cyclohexyl]piperidine) on the histological consequences of focal, as opposed to global, cerebral ischemia in both the rat and the cat. Ifenprodil (0.3-3 mg/kg i.v.) administered as a perfusion over 3 hr after occlusion of the feline middle cerebral artery reduced the volume of infarcted tissue (measured 4 days after occlusion) in a dose-related manner. At the highest dose a 42% reduction of infarcted volume was noted, essentially in cortical tissue. In an identical protocol, a derivative of ifenprodil, SL 82.0715, reduced the volume of infarction in a manner comparable to that described for ifenprodil. As SL 82.0715 possesses better p.o. bioavailability, this compound was also evaluated in the rat, again after middle cerebral artery occlusion. First administered 30 min after the induction of ischemia, SL 82.0715 (1 and 10 mg/kg p.o.) reduced infarction volume by 34 and 48%, respectively. The quantitative histology was performed 2 days after middle cerebral artery occlusion. The noncompetitive receptor antagonist, 1-[1-(2-thienyl)cyclohexyl]piperidine, administered (1 mg/kg i.p.) before the induction of focal ischemia, similarly and significantly decreased the final volume of infarction. As both ifenprodil and SL 82.0715 are noncompetitive antagonists of the NMDA receptor, two conclusions may be drawn from the present investigation. First, NMDA antagonism by ifenprodil and its derivative is an effective approach for tissue sparing in animal models of stroke and brain infarction. Second, these pharmacological observations provide evidence for the involvement of excitatory amino-acid induced-neurotoxicity in the evolution and consequences of focal cerebral ischemia.

Topics: Animals; Aspartic Acid; Brain Ischemia; Cats; Female; Male; Models, Cardiovascular; N-Methylaspartate; Phencyclidine; Piperidines; Rats; Rats, Inbred F344; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Vasoconstriction