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Myung A. Lee

Bio: Myung A. Lee is an academic researcher from Vanderbilt University. The author has contributed to research in topics: Clozapine & Schizophrenia. The author has an hindex of 22, co-authored 40 publications receiving 1987 citations. Previous affiliations of Myung A. Lee include Vanderbilt University Medical Center & University Hospitals of Cleveland.

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Journal ArticleDOI
TL;DR: The muscarinic receptor agonist activities of NDMC are unique among antipsychotics, and provide a possible molecular basis for the superior clinical effects of clozapine pharmacotherapy.
Abstract: Clozapine is a unique antipsychotic, with efficacy against positive symptoms in treatment-resistant schizophrenic patients, and the ability to improve cognition and treat the negative symptoms characteristic of this disease. Despite its unique clinical actions, no specific molecular mechanism responsible for these actions has yet been described. To comprehensively profile a large library of neuropsychiatric drugs, including most antipsychotics, at human monoamine receptors using R-SAT, an in vitro functional assay. Profiling revealed that N-desmethylclozapine (NDMC), the principal metabolite of clozapine, but not clozapine itself, is a potent and efficacious muscarinic receptor agonist, a molecular property not shared by any other antipsychotic. To further explore the role of NDMC muscarinic receptor agonist properties in mediating the physiological actions of clozapine, systemically administered NDMC was found to stimulate the phosphorylation of mitogen-activated protein kinase (MAP kinase) in mouse CA1 hippocampal neurons, an effect that was blocked by scopolamine, confirming central M1 muscarinic receptor agonist activity in vivo. Lastly, an analysis of clozapine and NDMC serum levels in schizophrenic patients indicated that high NDMC/clozapine ratios better predicted improvement in cognitive functioning and quality of life than the levels of either compound alone. The muscarinic receptor agonist activities of NDMC are unique among antipsychotics, and provide a possible molecular basis for the superior clinical effects of clozapine pharmacotherapy.

218 citations

Journal Article
TL;DR: In this article, the effect of clozapine, an atypical antipsychotic drug, on cognitive function in 36 patients with treatment-resistant schizophrenia and non-treatment resistant schizophrenia was studied.
Abstract: Cognitive dysfunction may underlie some of the psychopathology of schizophrenia as well as contribute to impaired social and vocational function in this disorder. Chronic treatment with typical neuroleptics has been reported to produce only minimal improvement in and may impair cognitive function in schizophrenia. We have studied the effect of clozapine, an atypical antipsychotic drug, on cognitive function in 36 patients with treatment-resistant schizophrenia. In addition, patients with non-treatment-resistant schizophrenia were randomly assigned to clozapine (N = 24) or typical neuroleptics (N = 23). Cognitive function in the treatment-resistant schizophrenia group was studied after 6 weeks and 6 months of treatment, while the non-treatment-resistant patients were also studied at 12 months of treatment. Clozapine treatment improved several domains of cognitive function, especially attention and verbal fluency in both treatment-resistant schizophrenia and non-treatment-resistant schizophrenia. On the other hand, typical neuroleptic treatment produced minimal improvement in cognitive function. The effect of clozapine on some tests of attention and verbal fluency was significantly greater than that of typical neuroleptic treatment in non-treatment-resistant schizophrenia. These data suggest that clozapine treatment was superior to typical neuroleptics in improving cognitive function in schizophrenia. The possibility that this is related to normalization of dopaminergic function by clozapine is discussed.

198 citations

Journal Article
TL;DR: Clozapine treatment was superior to typical neuroleptics in improving cognitive function in schizophrenia, especially attention and verbal fluency in both treatment- resistant schizophrenia and non-treatment-resistant schizophrenia.

196 citations

Journal ArticleDOI
TL;DR: The decreases in plasma glycine levels support the evidence for an abnormality in the glutamatergic system in schizophrenia, and provide additional support for efforts to improve negative symptoms by augmentation of antipsychotic drugs with agonists at the glycine site of the NMDA receptor.
Abstract: Previous studies have suggested decreased N-methyl-D-aspartate (NMDA)-type glutamate receptor function may contribute to increased negative symptoms in patients with schizophrenia. Consistent with this hypothesis, glycine, a co-agonist at NMDA receptors, has been reported to improve negative symptoms associated with the illness. This study was performed to determine if plasma levels of glycine or its ratio to serine, a precursor of glycine, are decreased in patients with schizophrenia compared to normal control subjects or patients with major depression. We also tested the hypothesis that these amino acids were correlated with negative symptoms in subjects with schizophrenia. Plasma levels of glycine, serine, and their ratio, were compared in 144 patients with schizophrenia, 44 patients with major depression, and 49 normal control subjects. All subjects were medication-free. Psychopathology was evaluated using the Brief Psychiatric Rating Scale (BPRS). Plasma glycine levels and glycine/serine ratios were decreased in patients with schizophrenia relative to control subjects and patients with major depression. By contrast, serine levels were increased in patients with schizophrenia compared to normal subjects but not compared to major depression. Patients with major depression also had increased plasma serine levels and decreased glycine/serine ratios compared to normal controls, but glycine levels were not different from those of normal controls. In subjects with schizophrenia, glycine levels predicted the Withdrawal-Retardation score (BPRS), whereas no such correlation was found in subjects with major depression. These results provide additional evidence that decreased availability of glycine may be related to the pathophysiology of negative symptoms. The decreases in plasma glycine levels support the evidence for an abnormality in the glutamatergic system in schizophrenia, and provide additional support for efforts to improve negative symptoms by augmentation of antipsychotic drugs with agonists at the glycine site of the NMDA receptor.

168 citations

Journal ArticleDOI
TL;DR: The finding that the difference in age at onset between males and females is smaller in neuroleptic-resistant patients than in neuroLEptic-responsive patients suggests that neuroleptics differ premorbidly as well as after onset of illness.
Abstract: Objective: The age at onset of schizophrenia for males has usually but not always been reported to be less than that for females. Early onset has also been associated with poor response to neuroleptic treatment and worse long-term outcome. The authors compared age at onset in neuroleptic-resistant and -responsive schizophrenic patients to determine whether the gender difference in age at onset is related to response to neuroleptic treatment. Method: The subjects were 322 patients with schizophrenia or schizoaffective disorder who were consecutively admitted to a university hospital-based research program. Results: Analysis of variance showed significant relationships between age at onset and both gender and longterm responsivity to neuroleptic drugs. The mean ages at onset in the neuroleptic-responsive men (mean=21.2 years, SD=6.1, N=75), neuroleptic-resistant men (mean=19.4 years, SD=4.7, N=119), and neuroleptic-resistant women (mean=20.1 years, SD=6.3, N=77) were fairly similar, whereas that of the neuroleptic-responsive women (mean=24.2 years, SD=8.7, N=51) was significantly greater than for all other groups. A simple effects model indicated that male and female neuroleptic-resistant patients did not differ significantly in mean age at onset, whereas male and female neuroleptic-responsive patients did. The effect of gender and neuroleptic responsivity on age at onset was related to schizophrenic subtype. Conclusions: These results confirm previous data indicating neuroleptic resistance is associated with early onset. The finding that the difference in age at onset between males and females is smaller in neurolepticresistant patients than in neuroleptic-responsive patients suggests that neuroleptic-resistant patients differ premorbidly as well as after onset of illness. (Am J Psychiatry 1997; 154:475‐482)

157 citations


Cited by
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TL;DR: In response to stress, the brain activates several neuropeptide-secreting systems, which eventually leads to the release of adrenal corticosteroid hormones, which subsequently feed back on the brain and bind to two types of nuclear receptor that act as transcriptional regulators as mentioned in this paper.
Abstract: In response to stress, the brain activates several neuropeptide-secreting systems. This eventually leads to the release of adrenal corticosteroid hormones, which subsequently feed back on the brain and bind to two types of nuclear receptor that act as transcriptional regulators. By targeting many genes, corticosteroids function in a binary fashion, and serve as a master switch in the control of neuronal and network responses that underlie behavioural adaptation. In genetically predisposed individuals, an imbalance in this binary control mechanism can introduce a bias towards stress-related brain disease after adverse experiences. New candidate susceptibility genes that serve as markers for the prediction of vulnerable phenotypes are now being identified.

3,727 citations

Journal ArticleDOI
TL;DR: This paper will attempt to confirm the conclusions from a previous review that certain neurocognitive domains (secondary verbal memory, immediate memory, executive functioning as measured by card sorting, and vigilance) are associated with functional outcome.
Abstract: There has been a surge of interest in the functional consequences of neurocognitive deficits in schizophrenia. The published literature in this area has doubled in the last few years. In this paper, we will attempt to confirm the conclusions from a previous review that certain neurocognitive domains (secondary verbal memory, immediate memory, executive functioning as measured by card sorting, and vigilance) are associated with functional outcome. In addition to surveying the number of replicated findings and tallying box scores of results, we will approach the review of the studies in a more thorough and empirical manner by applying a meta-analysis. Lastly, we will discuss what we see as a key limitation of this literature, specifically, the relatively narrow selection of predictor measures. This limitation has constrained identification of mediating variables that may explain the mechanisms for these relationships.

2,911 citations

Journal Article
TL;DR: A rating scale for drug-induced akathisia has been derived that incorporates diagnostic criteria for pseudoakathisio, and mild, moderate, and severe akath isia, and there is an item for rating global severity.
Abstract: A rating scale for drug-induced akathisia has been derived that incorporates diagnostic criteria for pseudoakathisia, and mild, moderate, and severe akathisia. It comprises items for rating the observable, restless movements which characterise the condition, the subjective awareness of restlessness, and any distress associated with the akathisia. In addition, there is an item for rating global severity. A standard examination procedure is recommended. The inter-rater reliability for the scale items (Cohen's kappa) ranged from 0.738 to 0.955. Akathisia was found in eight of 42 schizophrenic in-patients, and nine had pseudoakathisia, where the typical sense of inner restlessness was not reported.

1,942 citations

Journal ArticleDOI
TL;DR: A facile approach for designing families of GPCRs with engineered ligand specificities will prove to be powerful tools for selectively modulating signal-transduction pathways in vitro and in vivo.
Abstract: We evolved muscarinic receptors in yeast to generate a family of G protein-coupled receptors (GPCRs) that are activated solely by a pharmacologically inert drug-like and bioavailable compound (clozapine-N-oxide) Subsequent screening in human cell lines facilitated the creation of a family of muscarinic acetylcholine GPCRs suitable for in vitro and in situ studies We subsequently created lines of telomerase-immortalized human pulmonary artery smooth muscle cells stably expressing all five family members and found that each one faithfully recapitulated the signaling phenotype of the parent receptor We also expressed a Gi-coupled designer receptor in hippocampal neurons (hM4D) and demonstrated its ability to induce membrane hyperpolarization and neuronal silencing We have thus devised a facile approach for designing families of GPCRs with engineered ligand specificities Such reverse-engineered GPCRs will prove to be powerful tools for selectively modulating signal-transduction pathways in vitro and in vivo

1,696 citations

Journal ArticleDOI
TL;DR: This review aims to synthesize the available evidence and assess the value of the clock‐drawing test according to well‐defined criteria.
Abstract: Objective. The clock-drawing test has achieved widespread clinical use in recent years as a cognitive screening instrument and a significant amount of literature relates to its psychometric properties and clinical utility. This review aims to synthesize the available evidence and assess the value of this screening test according to well-defined criteria. Design. A Medline and Psycho-info literature search of all languages was done from 1983 to 1998 including manual cross-referencing of bibliographies. A brief summary of all original scoring systems is provided as well as a review of replication studies. Psychometric data including correlations with other cognitive tests were recorded. Qualitative aspects of the test are also described. Results. Among published studies, the mean sensitivity (85%) and specificity (85%) of the clock-drawing test are impressive. Correlations with the Mini-Mental State Examination and other cognitive tests was high, generally greater than r = 0.5. High levels of inter-rater and test–re-test reliability and positive predictive value are recorded and despite significant variability in the scoring systems, all report similar psychometric properties. The clock test also shows a sensitivity to cognitive change with good predictive validity. Conclusions. The clock-drawing test meets defined criteria for a cognitive screening instrument. It taps into a wide range of cognitive abilities including executive functions, is quick and easy to administer and score with excellent acceptability by subjects. Together with informant reports, the clock-drawing test is complementary to the widely used and validated Mini-Mental State Examination and should provide a significant advance in the early detection of dementia and in monitoring cognitive change. A simple scoring system with emphasis on the qualitative aspects of clock-drawing should maximize its utility. Copyright © 2000 John Wiley & Sons, Ltd.

1,193 citations