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H J Kupferberg

Publications and source records attributed to H J Kupferberg.

At least 19 recordsLinked to original sources
PubMed1992

Strategies for identifying and developing new anticonvulsant drugs.

The identification of new anticonvulsant drugs depends on the use of different animal models of epilepsy. The models should be mechanism-independent, able to screen a large number of compounds, at limited cost and technical expertise. Primary screening models include genetic or reflex models of epilepsy and electrically and chemically induced seizures. Once active compounds have been identified, more advanced mechanistic and seizure-specific models are needed to refine the choice of a lead compound. These can be either in vivo or in vitro models. Models known to interact with specific receptors or the production of the putative neurotransmitters of neural excitability or inhibition are valuable in assessing possible mechanisms of action. In vitro models have evolved as important tools in correlating changes in electrical phenomena and therapeutic spectrum. The use of the hippocampal slice and the cultured neuron permits classification of anticonvulsant activity based on cellular actions of the drug. Interactions by the experimental drugs with specific subcellular fractions of the central nervous system augment information on possible mechanisms of action. The final choice of compounds for development requires synthesizing and comparing all of the pharmacodynamic information with the pharmacokinetic and toxicologic data. In the final analysis, no single animal model of epilepsy known today can assure the development of better drugs for all treatment of the epilepsies.

Animals↗
PubMed1990

Use of stable isotopes and gas chromatography-mass spectrometry in the study of different pools of neurotransmitter amino acids in brain slices.

A method was developed for simultaneous determination of endogenous and newly synthesized neurotransmitter amino acids (4-aminobutyric acid, glutamate and aspartate) and glutamine in brain in vitro. Brain slices were incubated in artificial cerebrospinal fluid in the presence of 13C-labeled precursors (glucose, pyruvate or acetate). After the incubation, the slices were homogenized in cold 80% ethanol and the supernatants were evaporated to dryness. The resultant residues were derivatized with N-methyl-N-(tert.-butyldimethylsilyl)trifluoroacetamide and analyzed by capillary gas chromatography-mass spectrometry in the electron-impact mode. N(O)-tert.-Butyldimethylsilyl derivatives of the naturally occurring amino acids, their 13C-enriched counterparts and deuterated internal standards were detected as their [M-57]+ fragments using selected-ion monitoring. The method was shown applicable to studying compartmentation of neurotransmitter amino acids.

Amino Acids↗
PubMed1990

Antagonism between intracerebroventricularly administered N-methyl-D-aspartate and bicuculline methiodide in induction of clonic seizures in mice.

N-Methyl-D-aspartate and bicuculline were administered alone or as a combination by intracerebroventricular injection to mice, and their convulsant activity was monitored. Both of these compounds elicited clonic seizures, though by different mechanisms. However, their simultaneous administration resulted in less than additive induction of clonic activity.

Animals↗
PubMed1989

Antiepileptic drug development program: a cooperative effort of government and industry.

The most important step in antiepileptic drug discovery is the choice of an appropriate animal model for the initial screening as well as for the more complex procedures that elucidate mechanisms of action. The currently available models fall short in their inability to identify all drugs for all types of seizures in a mechanism-independent manner. Nevertheless, spontaneous models of epilepsy are the most commonly used, and chemically or electrically induced seizures in rodents can also identify potential anticonvulsants. In the latter models, the intensity of the seizure stimulus is of paramount importance. The Antiepileptic Drug Development Program evaluates approximately 800 compounds each year, using two models for preliminary screening. One model assesses the ability of a compound to prevent seizure spread; the other weighs the ability to raise seizure threshold. In vivo tests, featuring amygdala- and corneal-kindled seizures, and in vitro assays, employing gamma-aminobutyric acid (GABA) receptors and synaptosomal uptake of adenosine, define drug-drug interactions and elucidate the pharmacological profiles of potential anticonvulsants.

Animals↗
PubMed1988

Effects of pharmacological manipulations on basal and newly synthesized levels of GABA, glutamate, aspartate and glutamine in mouse brain cortex.

Concentrations of basal and newly synthesized inhibitory (gamma-aminobutyric acid, GABA) and excitatory (glutamate and aspartate) neurotransmitter amino acids and glutamine were determined in mouse brain cortex. Isotopic enrichment following an intravenous infusion of a stable-labeled precursor, [13C6]D-glucose, was used to estimate the newly synthesized amino acid content. Effects of various pharmacological agents (valproate, aminooxyacetic acid, 3-mercaptopropionic acid, N-methyl-D-aspartate, and 2-amino-7-phosphonohepatanoic acid) were evaluated. The effects of 3-mercaptopropionic acid (an inhibitor of glutamate decarboxylase, a GABA-synthesizing enzyme) were restricted to the GABAergic system. On the other hand, N-methyl-D-aspartate (an agonist of a glutamate receptor subtype) was selective for the glutamate-glutamine system, and its effects were prevented by its selective antagonist, 2-amino-7-phosphonoheptanoic acid. In some cases, divergent effects were observed on basal and new amino acids. This suggested that basal and new amino acids may represent different compartments. The anticonvulsant drug valproate caused an increase in basal but a decrease in newly synthesized GABA. Aminooxyacetic acid caused a dramatic increase in basal GABA without affecting the newly synthesized GABA. This approach may be useful in studying compartmentation and fluxes of neurotransmitters.

2-Amino-5-phosphonovalerate↗
PubMed1987

Determination of 4-aminobutyric acid, aspartate, glutamate and glutamine and their 13C stable-isotopic enrichment in brain tissue by gas chromatography-mass spectrometry.

A selected-ion monitoring method was developed for measuring 4-aminobutyric acid, aspartate, glutamate, and glutamine in brain tissue. Natural isotopes of these amino acids and their stable-isotopic enrichment following intravenous infusion of a precursor, [13C]glucose, were quantitated. Frozen mouse brain tissue was homogenized in cold 80% ethanol, and the supernatant, equivalent to 1 mg of wet weight brain tissue, was extracted using solid-phase bonded silica ion-exchange columns. Aspartate and glutamate (dicarboxylic acids) were isolated from strong anion-exchange columns, whereas 4-aminobutyric acid and glutamine (neutral amino acids) were isolated from strong-cation exchange columns. n-Butyl ester pentafluoropropionyl amide derivatives of these amino acids were analyzed by gas chromatography-mass spectrometry using a methane positive chemical ionization mode after gas chromatographic separation on a wide-bore, fused-silica capillary column. The method is applicable to determination of brain concentrations of these amino acids as well as their fluxes following administration of a stable-isotopic tracer.

Amino Acids↗
PubMed1986

Determination in plasma of a new antiepileptic drug, dl-(5 alpha,9 alpha,11S*)-5,6,9,10-tetrahydro-N,N-dimethyl-5,9-methanobenzocycloo cten-11-amine hydrochloride, and its N-desmethyl metabolite by liquid-solid extraction and capillary gas chromatography.

We have developed a sensitive and accurate method for the determination in plasma of the antiepileptic drug dl-(5 alpha,9 alpha,11S*)-5,6,9,10- tetrahydro-N,N-dimethyl-5,9-methanobenzocycloocten-11-amine hydrochloride and its N-desmethyl metabolite. The extraction procedure utilizes base-treated disposable C2 solid-phase columns, with the analyte eluted with organic solvent. Nitrogen-selective gas chromatography is used for detection. Linear regression analysis showed that the method is linear between 4 and 1500 ng/ml for the parent drug and between 8 and 3000 ng/ml for the N-desmethyl metabolite. Intra- and inter-day variability, as shown by the coefficient of variation, is less than 8% for both compounds. The method is applicable to routine plasma determination of both these compounds in clinical pharmacokinetic studies.

Anticonvulsants↗
PubMed1986

Enhanced bursting activity in the CA3 region of the mouse hippocampal slice without long-term potentiation in the dentate gyrus after systemic pentylenetetrazole kindling.

The repeated administration of subconvulsant doses of pentylenetetrazole (24 mg/kg, i.p.) produced chemically kindled seizures in 16 of 20 mice. Hippocampal slices prepared from the mice with kindled seizures were tested for input-output characteristics in the dentate gyrus, and for spontaneous burst discharge frequency in area CA3. The kindled slices displayed no change in the magnitude of the evoked granule cell excitatory postsynaptic potential (pEPSP) to a given stimulus intensity applied to the perforant path, nor in magnitude of the granule cell population spike for a given pEPSP. Although long-term potentiation of synaptic transmission has been proposed as the cellular mechanism of kindling, these results indicate either that long-term potentiation may not underlie kindling or that systemic pentylenetetrazole kindling and focal electrical kindling may be accomplished by different mechanisms. Hippocampal slices from kindled animals did, however, show an increased incidence of spontaneous burst discharges in area CA3 pyramidal neurons in both the absence and the presence of pentylenetetrazole in the bathing medium.

Action Potentials↗
PubMed1986

Single and multiple dose kinetics of a new antiepileptic drug, Org 6370, and its desmethyl metabolite, Org 6363.

The pharmacokinetic parameters of the new antiepileptic drug, Org 6370, and its desmethyl metabolite, Org 6363, were studied in healthy male volunteers. Plasma concentrations of the compounds were determined by a new method using liquid-solid extraction and capillary gas-chromatographic separation with a nitrogen-selective detector. The kinetic parameters obtained after a single oral dose of Org 6370 were not good predictors of multiple-dose parameters. With long-term treatment, there was unanticipated accumulation of the parent drug and especially the metabolite. The clinical implication of these findings is that caution must be exercised in clinical trials of Org 6370.

Adult↗
PubMed1985

Effect of GABA agonists on the neurotoxicity and anticonvulsant activity of benzodiazepines.

Progabide (50 mg/kg, i.p.), a GABA receptor agonist, significantly decreases the median minimal neurotoxic dose (TD50) of clobazam, chlordiazepoxide, and diazepam; the receptor binding of these substances is highly enhanced by muscimol. Progabide has no significant effect on the TD50 of clonazepam and triazolam; the receptor bindings of these substances is either only slightly enhanced or not altered by muscimol. Progabide also significantly decreases the median antimaximal electroshock dose (MES ED50) of all the benzodiazepines tested. However, progabide has no effect on the median antipentylenetetrazol dose (PTZ ED50) of the benzodiazepines. Likewise, THIP (2.5 mg/kg, i.p.) significantly decreases the TD50 of chlordiazepoxide but not that of triazolam. THIP significantly decreases the MES ED50 of chlordiazepoxide and triazolam but has no effect on the PTZ ED50 of these two substances. The above data suggest that benzodiazepine receptors linked to GABA receptors contribute to the minimal neurotoxicity and anti-MES activity but not to the anti-PTZ activity of benzodiazepines.

Animals↗
PubMed1985

Advances in the clinical development of antiepileptic drugs.

In this paper we describe advances in the clinical development of antiepileptic drugs as a function of the Antiepileptic Drug Development Program of the National Institute of Neurological and Communicative Disorders and Stroke. This program encompasses both the preclinical and clinical elements of drug development through the Anticonvulsant Screening Project, the Toxicology Project, and the support of controlled clinical trials of potential new drugs that emerge from these projects and promise to be more effective and less toxic than those currently available for the treatment of epilepsy.

Animals↗
PubMed1985

Antiepileptic drugs: detection, quantification, and evaluation.

The anticonvulsant potential of chemical substances can be identified with test procedures that act at various biological levels, ranging from subcellular elements to the normal or modified intact animal. All of these procedures modify either some minimal overt threshold electrochemical or neurochemical event or a suprathreshold manifestation such as seizure spread. This suggests that laboratory tests for the detection, quantification, and evaluation of antiepileptic drugs should be designed to identify substances that elevate seizure threshold and/or prevent seizure spread. The s.c. Metrazol (pentylenetetrazol) seizure threshold test and the supramaximal electroshock seizure test are commonly used to achieve this objective. Additional chemoshock tests may be used to delineate further the mechanisms of anticonvulsant action. Numerous variables, such as experimental animals, electroshock apparatus, parameters of electrical and chemical stimulus, and routes of drug administration, must be controlled to ensure accurate, reliable, and reproducible results. The in vivo procedures described are reliable and reproducible, and predict clinical utility of the drugs tested. New models for testing anticonvulsant activity are evaluated against clinically effective antiepileptic drugs originally identified by these same procedures.

Age Factors↗
PubMed1984

Disposition of mephenytoin and its metabolite, nirvanol, in epileptic patients.

We investigated the conversion of mephenytoin to nirvanol in five patients with uncontrolled complex partial seizures. After a 50-mg single oral dose, mean peak mephenytoin level was 0.48 microgram/ml and nirvanol 0.37 microgram/ml. After 400 mg, peak mephenytoin level was 3.9 micrograms/ml and nirvanol 2.5 micrograms/ml. On 400 mg daily, mephenytoin reached a mean steady-state level of 1.5 micrograms/ml. Nirvanol mean steady-state level was 18 micrograms/ml. Mean plasma half-life was 17 hours for mephenytoin and 114 hours for nirvanol. Two patients had reduced seizures during mephenytoin therapy and one a transient increase during drug withdrawal. No toxicity was seen, but mephenytoin was not more effective than phenytoin.

Adolescent↗