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Biomedical subjects

G E Tsai

Publications and source records attributed to G E Tsai.

7 recordsLinked to original sources
PubMed1999

D-serine added to clozapine for the treatment of schizophrenia.

OBJECTIVE: D-Serine is a full agonist at the glycine site on the N-methyl-D-aspartate (NMDA) receptor. Previous administration of D-serine to schizophrenic patients taking nonclozapine antipsychotics improved positive, negative, and cognitive symptoms, whereas the partial agonist D-cycloserine improved negative symptoms of patients taking conventional antipsychotics but worsened symptoms in clozapine-treated patients. To study the difference between full and partial agonists at the NMDA receptor glycine site, the clinical effects of adding D-serine to clozapine were assessed. METHOD: In a 6-week double-blind trial, 20 schizophrenic patients received placebo or D-serine (30 mg/kg per day) in addition to clozapine. Clinical efficacy, side effects, and serum levels of D-serine were determined every other week. RESULTS: The patients exhibited no improvement with D-serine, nor did their symptoms worsen, as previously reported with D-cycloserine. CONCLUSIONS: The results suggest either that clozapine may have an agonistic effect on the NMDA system or that clozapine-treated patients do not respond to D-serine.

Antipsychotic Agents↗
PubMed1999

Improved cognition in Alzheimer's disease with short-term D-cycloserine treatment.

OBJECTIVE: Glutamatergic neurotransmission is important for memory and cognition and is severely affected in Alzheimer's disease. D-Cycloserine exhibits partial agonist activity at the glycine site of N-methyl-D-aspartate subtype glutamate receptor, facilitating activation of the receptor and improving cognition and memory. METHOD: Seventeen patients with Alzheimer's disease received a three-phase, double-blind, placebo-controlled trial of 50 mg and 100 mg/day of D-cycloserine. RESULTS: D-Cycloserine was associated with significant improvement in scores on the cognitive subscale of the Alzheimer's Disease Assessment Scale (improvement of 3.0 points) when given at a dose of 100 mg/day. CONCLUSIONS: D-Cycloserine has cognitive benefits for patients with Alzheimer's disease.

Aged↗
PubMed1998

Increased glutamatergic neurotransmission and oxidative stress after alcohol withdrawal.

OBJECTIVE: Neurophysiological and pathological effects of ethanol may be mediated, to an important extent, via the glutamatergic system. Animal studies indicate the acute effects of ethanol disrupt glutamatergic neurotransmission by inhibiting the response of the N-methyl-D-aspartate (NMDA) receptor. Persistent attenuation of glutamatergic neurotransmission by chronic ethanol exposure results in the compensatory up-regulation of NMDA receptors. Whether glutamatergic neurotransmission and oxidative stress are enhanced during ethanol withdrawal in humans is unknown. METHOD: CSF was obtained from 18 matched comparison subjects and from 18 patients with alcohol dependence 1 week and 1 month after cessation of ethanol ingestion. CSF samples were analyzed for excitatory neurotransmitters, gamma-aminobutyric acid (GABA), and markers for oxidative stress. RESULTS: The alcohol-dependent patients' CSF levels of aspartate, glycine, and N-acetylaspartylglutamate were all higher than those of the comparison subjects, and their concentration of GABA was lower. In addition, there were significant correlations between excitatory neurotransmitters and oxidative stress markers, which suggest that the two mechanisms may play an interactive role in neurotoxicity mediated by ethanol withdrawal. CONCLUSIONS: The data suggest that augmentation of excitatory neurotransmission may lead to enhanced oxidative stress, which, in concert with reduced inhibitory neurotransmission, may contribute to the symptoms of ethanol withdrawal and associated neurotoxicity in humans. Whether these abnormalities represent a trait- or state-dependent marker of ethanol dependence remains to be resolved.

Adult↗
PubMed1998

A preliminary study of D-cycloserine treatment in Alzheimer's disease.

D-cycloserine is a partial agonist on the glycine site of the N-methyl-D-aspartate glutamate receptor. This double-blind crossover study of 15 mg D-cycloserine in Alzheimer's disease patients did not demonstrate clinical benefit. Higher medication dosage or long-term treatment may be required.

Aged↗
PubMedDate not supplied

A glutamatergic model of ECT-induced memory dysfunction.

Electroconvulsive therapy (ECT) is an efficacious treatment for a variety of neuropsychiatric conditions including major depression, mania, catatonia, Parkinson's disease, and neuroleptic malignant syndrome. However, ECT-induced memory dysfunction complicates the treatment and is a major concern for both patients and providers. We briefly review ECT-induced memory dysfunction and propose a glutamatergic model for it. (Articles examined were retrieved by a Medline search on the terms electroconvulsion and glutamate, with language limited to English.) Specifically, we hypothesize that ECT-induced memory dysfunction results from neuronal insults due to excessive release of excitatory amino acids and activation of their receptors, which produce cation and water flux and reversible oxidative stress. This model offers multiple testable hypotheses; exploring them may help to identify the risk factors for this significant side effect of ECT treatment and may thus yield effective agents for its prevention and treatment.

Electroconvulsive Therapy↗