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Analysis of serotonin 5HT2 and 5HT1A receptor coding sequences in schizophrenia patients and control subjects
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evaluated several close structural analogs of clozapine for their ability to prevent NRH neurotoxicity induced by the powerful NMDA antagonist, MK-801. Olanzapine and fluperlapine, which are thought to possess the same atypical antipsychotic property as clozapine, were at least as potent as clozapine in preventing NRH neurotoxicity. Loxapine, an antipsychotic without the atypicality of clozapine, was moderately effective and amoxapine, which has little or no antipsychotic activity, was ineffective in preventing NRH neurotoxicity. We propose that further research aimed at identifying the neural circuits and receptor systems through which clozapine and its analogs act to block NRH neurotoxicity may help clarify the basis for clozapine's unique clinical profile.
ANALYSIS OF SEROTONIN 5HT2 AND 5HT1A RECEPTOR CODING SEQUENCES IN SCHIZOPHRENIA PATIENTS AND CONTROL SUBJECTS B.C-T. Wu, J.T. Warren, Jr., J. Shih, R. Tandon, H. Meltzer, J.K. Fink*
Department of Neurology, University of Michigan, Ann Arbor, M148105, USA Neurochemical and neuropharmacologic evidence raise the possibility that dysfunction of serotonin receptors may be involved in schizophrenia. For some patients, these abnormalities could be due to inherited mutations in the genes encoding serotonin receptors. We developed denaturing gradient gel electrophoresis (DGGE) strategies to evaluate the 5HT2 and 5HT1A coding sequences for mutations that might be associated specifically with schizophrenia. DGGE is an extremely sensitive and efficient method for identifying single nucleotide substitutions, small deletions and insertions. Our DGGE system can detect mutations in all regions of the 5HT1A coding sequence ( 1.2 kb) and in more than 90% of the 5HT2 coding sequence ( 1.5 kb). We evaluated 5HT1A and 5HT2 coding sequences in samples from 126 schizophrenia subjects and 116 control subjects. Schizophrenia subjects were diagnosed according to DSMIII-R criteria. Control subjects were older than age 60, did not endorse any major criteria on the Screening Criteria for Informative Diagnoses (SCID) questionnaire, and did not have first degree relatives with schizophrenia or depression. PCR was used to amplify 5HT1A and 5HT2 coding sequences as a series of overlapping fragments from leukocyte DNA. Each fragment was analyzed by DGGE. We identified 4 novel polymorphisms in the 5HT1A coding sequence and 7 novel polymorphisms in the 5HT2 coding sequence. In general, each unique polymorphism occurred in only several subjects. To date, no polymorphism is associated specifically with schizophrenia. Our data indicate that disturbance of serotonergic neurotransmission in schizophrenia is not related to mutations in coding sequences of serotonergic receptors 5HTIA and 5HT2. If disturbance of serotonergic neurotransmission is a primary, etiologic process in schizophrenia, our findings suggest that alternative mechanisms (e.g. promoter mutations) for 5HT1A and 5HT2 or that other genes
(e.g. other types of serotonin receptors or serotonin transporters) are involved.
PHENCYCLIDINE PRODUCES DISTINCT TIME-DEPENDENT REGIONAL ALTERATIONS IN FOUR DIFFERENT IMMEDIATE EARLY GENES IN RAT BRAIN X.M. Gao*, T. Hashimoto, C.A. Tamminga
Maryland Psychiatric Research Center, Universityof Maryland, Baltimore, MD 21228, USA We have previously reported extended time-dependent actions of PCP and MK801 in rat brain using regional cerebral glucose utilization and hippocampal glutamate receptor density (Eur. J. Pharmacol. 241: 7, 1993; Neurosci. Lett. 174: 149, 1994). Now we have examined the extended time-dependent action of PCP (8.6 mg/kg) on the pattern of expression of four different immediate early genes (lEGs) in rat. Zif268, cfos, c-jun and jun-B mRNA were quantified by in situ hybridization at 0, 1, 3, 6, 24, and 48 h after PCP. Selective induction of cfos, c-jun, and jun-B mRNAs occurred in anterior and posterior cingulate cortex from one to six hours after PCP with normalization by 24 h; additional regional changes distinguished these IEGs. In contrast, the expression of zif268 mRNA was depressed by PCP; moreover, the change was extended over 3 h, 6 h and 24 h, particularly in the limbic system (hippocampal CA1 and anterior cingulate cortex). This zif268 suppression lasting at least 24 h, may parallel the time course of PCP action in our previous glucose metabolism study. Elsewhere in this volume, our colleagues report that ketamine, a phencyclidine agonist, increased the rCBF in human anterior cingulate cortex and decreased blood flow in hippocampus while inducing psychosis changes in schizophrenia (Neuropharmacology 1994, in press). Taken together, these data suggest that the limbic system (anterior cingulate and hippocampal cortex), is a site which may be related to the acute and delayed psychotomimetic actions of PCP in humans and, speculatively, to schizophrenia itself.
HEIGHTENED VASOPRESSIN SECRETION FOLLOWING PSYCHOTIC EXACERBATIONS IN POLYDIPSIC SCHIZOPHRENIC PATIENTS WITH HYPONATREMIA M.B. Goldman*, G.L. Robertson, D.J. Luchins, D. Hedeker, G.N. Pandey
Department of Psychiatry, Pritzker School of Medicine, MC 3077, Chicago, IL 60637, USA Episodic water intoxication causes serious problems for many chronic schizophrenics. Previously characterized defects in fluid intake and excretion can account for these patients' mild basal hyponatremia, but are insufficient to explain why they become
evaluated several close structural analogs of clozapine for their ability to prevent NRH neurotoxicity induced by the powerful NMDA antagonist, MK-801. Olanzapine and fluperlapine, which are thought to possess the same atypical antipsychotic property as clozapine, were at least as potent as clozapine in preventing NRH neurotoxicity. Loxapine, an antipsychotic without the atypicality of clozapine, was moderately effective and amoxapine, which has little or no antipsychotic activity, was ineffective in preventing NRH neurotoxicity. We propose that further research aimed at identifying the neural circuits and receptor systems through which clozapine and its analogs act to block NRH neurotoxicity may help clarify the basis for clozapine's unique clinical profile.
ANALYSIS OF SEROTONIN 5HT2 AND 5HT1A RECEPTOR CODING SEQUENCES IN SCHIZOPHRENIA PATIENTS AND CONTROL SUBJECTS B.C-T. Wu, J.T. Warren, Jr., J. Shih, R. Tandon, H. Meltzer, J.K. Fink*
Department of Neurology, University of Michigan, Ann Arbor, M148105, USA Neurochemical and neuropharmacologic evidence raise the possibility that dysfunction of serotonin receptors may be involved in schizophrenia. For some patients, these abnormalities could be due to inherited mutations in the genes encoding serotonin receptors. We developed denaturing gradient gel electrophoresis (DGGE) strategies to evaluate the 5HT2 and 5HT1A coding sequences for mutations that might be associated specifically with schizophrenia. DGGE is an extremely sensitive and efficient method for identifying single nucleotide substitutions, small deletions and insertions. Our DGGE system can detect mutations in all regions of the 5HT1A coding sequence ( 1.2 kb) and in more than 90% of the 5HT2 coding sequence ( 1.5 kb). We evaluated 5HT1A and 5HT2 coding sequences in samples from 126 schizophrenia subjects and 116 control subjects. Schizophrenia subjects were diagnosed according to DSMIII-R criteria. Control subjects were older than age 60, did not endorse any major criteria on the Screening Criteria for Informative Diagnoses (SCID) questionnaire, and did not have first degree relatives with schizophrenia or depression. PCR was used to amplify 5HT1A and 5HT2 coding sequences as a series of overlapping fragments from leukocyte DNA. Each fragment was analyzed by DGGE. We identified 4 novel polymorphisms in the 5HT1A coding sequence and 7 novel polymorphisms in the 5HT2 coding sequence. In general, each unique polymorphism occurred in only several subjects. To date, no polymorphism is associated specifically with schizophrenia. Our data indicate that disturbance of serotonergic neurotransmission in schizophrenia is not related to mutations in coding sequences of serotonergic receptors 5HTIA and 5HT2. If disturbance of serotonergic neurotransmission is a primary, etiologic process in schizophrenia, our findings suggest that alternative mechanisms (e.g. promoter mutations) for 5HT1A and 5HT2 or that other genes
(e.g. other types of serotonin receptors or serotonin transporters) are involved.
PHENCYCLIDINE PRODUCES DISTINCT TIME-DEPENDENT REGIONAL ALTERATIONS IN FOUR DIFFERENT IMMEDIATE EARLY GENES IN RAT BRAIN X.M. Gao*, T. Hashimoto, C.A. Tamminga
Maryland Psychiatric Research Center, Universityof Maryland, Baltimore, MD 21228, USA We have previously reported extended time-dependent actions of PCP and MK801 in rat brain using regional cerebral glucose utilization and hippocampal glutamate receptor density (Eur. J. Pharmacol. 241: 7, 1993; Neurosci. Lett. 174: 149, 1994). Now we have examined the extended time-dependent action of PCP (8.6 mg/kg) on the pattern of expression of four different immediate early genes (lEGs) in rat. Zif268, cfos, c-jun and jun-B mRNA were quantified by in situ hybridization at 0, 1, 3, 6, 24, and 48 h after PCP. Selective induction of cfos, c-jun, and jun-B mRNAs occurred in anterior and posterior cingulate cortex from one to six hours after PCP with normalization by 24 h; additional regional changes distinguished these IEGs. In contrast, the expression of zif268 mRNA was depressed by PCP; moreover, the change was extended over 3 h, 6 h and 24 h, particularly in the limbic system (hippocampal CA1 and anterior cingulate cortex). This zif268 suppression lasting at least 24 h, may parallel the time course of PCP action in our previous glucose metabolism study. Elsewhere in this volume, our colleagues report that ketamine, a phencyclidine agonist, increased the rCBF in human anterior cingulate cortex and decreased blood flow in hippocampus while inducing psychosis changes in schizophrenia (Neuropharmacology 1994, in press). Taken together, these data suggest that the limbic system (anterior cingulate and hippocampal cortex), is a site which may be related to the acute and delayed psychotomimetic actions of PCP in humans and, speculatively, to schizophrenia itself.
HEIGHTENED VASOPRESSIN SECRETION FOLLOWING PSYCHOTIC EXACERBATIONS IN POLYDIPSIC SCHIZOPHRENIC PATIENTS WITH HYPONATREMIA M.B. Goldman*, G.L. Robertson, D.J. Luchins, D. Hedeker, G.N. Pandey
Department of Psychiatry, Pritzker School of Medicine, MC 3077, Chicago, IL 60637, USA Episodic water intoxication causes serious problems for many chronic schizophrenics. Previously characterized defects in fluid intake and excretion can account for these patients' mild basal hyponatremia, but are insufficient to explain why they become