Decreased expression of AMPA receptor messenger RNA and protein in AIDS: a model for HIV-associated neurotoxicity.

HIV infection can cause extensive neuronal loss and clinically a severe dementia. The cause of the neurotoxicity remains unclear as neurons are not infected, but disturbance of glutamate-linked calcium entry has been implicated. In this study, we have shown a decrease in HIV-infected brain of the expression of mRNA and protein of the GluR-A flop subtype of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) glutamate receptor in cerebellar Purkinje cells. Although Purkinje cells are relatively resistant to loss, the observed disturbance of AMPA receptors may contribute to the neurotoxic process in other vulnerable brain regions and clinically to the development of dementia.

Connecting patient needs with treatment management.

OBJECTIVE: To propose ideas for the development of a core strategy for monitoring patients with schizophrenia to ensure physical health and optimal treatment provision. METHOD: A panel of European experts in the field of schizophrenia met in Bordeaux in June 2006 to discuss, 'Patient management optimisation through improved treatment monitoring.' RESULTS: Key consensus from the discussion deemed that weight gain, oral health and ECG parameters were core baseline parameters to be monitored in all patients with schizophrenia. Further, an identification of a patient's own barriers to treatment alongside local health service strategies might comprise elements of an individualised management strategy which would contribute to optimisation of treatment. Any monitoring strategy should be kept simple to encourage physician compliance. CONCLUSION: A practical solution to the difficulties of providing holistic patient care would be to suggest a limited set of physical parameters to be monitored by physicians on a regular basis.

Randomised controlled trials of conventional antipsychotic versus new atypical drugs, and new atypical drugs versus clozapine, in people with schizophrenia responding poorly to, or intolerant of, current drug treatment.

OBJECTIVES: To determine the clinical and cost-effectiveness of different classes of antipsychotic drug treatment in people with schizophrenia responding inadequately to, or having unacceptable side-effects from, their current medication. DESIGN: Two pragmatic, randomised controlled trials (RCTs) were undertaken. The first RCT (band 1) compared the class of older, inexpensive conventional drugs with the class of new atypical drugs in people with schizophrenic disorders, whose current antipsychotic drug treatment was being changed either because of inadequate clinical response or owing to side-effects. The second RCT (band 2) compared the new (non-clozapine) atypical drugs with clozapine in people whose medication was being changed because of poor clinical response to two or more antipsychotic drugs. Both RCTs were four-centre trials with concealed randomisation and three follow-up assessments over 1 year, blind to treatment. SETTING: Adult mental health settings in England. PARTICIPANTS: In total, 227 participants aged 18-65 years (40% of the planned sample) were randomised to band 1 and 136 (98% of the planned sample) to band 2. INTERVENTIONS: Participants were randomised to a class of drug. The managing clinician selected the individual drug within that class, except for the clozapine arm in band 2. The new atypical drugs included risperidone, olanzapine, quetiapine and amisulpride. The conventional drugs included older drugs, including depot preparations. As in routine practice, clinicians and participants were aware of the identity of the prescribed drug, but clinicians were asked to keep their participating patient on the randomised medication for at least the first 12 weeks. If the medication needed to be changed, the clinician was asked to prescribe another drug within the same class, if possible. MAIN OUTCOME MEASURES: The primary outcome was the Quality of Life Scale (QLS). Secondary clinical outcomes included symptoms [Positive and Negative Syndrome Scale (PANSS)], side-effects and participant satisfaction. Economic outcomes were costs of health and social care and a utility measure. RESULTS: Recruitment to band 1 was less than anticipated (40%) and diminished over the trial. This appeared largely due to loss of perceived clinical equipoise (clinicians progressively becoming more convinced of the superiority of new atypicals). Good follow-up rates and a higher than expected correlation between QLS score at baseline and at follow-up meant that the sample as recruited had 75% power to detect a difference in QLS score of 5 points between the two treatment arms at 52 weeks. The recruitment to band 2 was approximately as planned. Follow-up assessments were completed at week 52 in 81% of band 1 and 87% of band 2 participants. Band 1 data showed that, on the QLS and symptom measures, those participants in the conventional arm tended towards greater improvements. This suggests that the failure to find the predicted advantage for new atypicals was not due to inadequate recruitment and statistical power in this sample. Participants reported no clear preference for either class of drug. There were no statistically significant differential outcomes for participants entering band 1 for reasons of treatment intolerance to those entering because of broadly defined treatment resistance. Net costs over the year varied widely, with a mean of 18,850 pounds sterling in the conventional drug group and 20,123 pounds sterling in the new atypical group, not a statistically significant difference. Of these costs, 2.1% and 3.8% were due to antipsychotic drug costs in the conventional and atypical group, respectively. There was a trend towards participants in the conventional drug group scoring more highly on the utility measure at 1 year. The results for band 2 showed an advantage for commencing clozapine in quality of life (QLS) at trend level (p = 0.08) and in symptoms (PANSS), which was statistically significant (p = 0.01), at 1 year. Clozapine showed approximately a 5-point advantage on PANSS total score and a trend towards having fewer total extrapyramidal side-effects. Participants reported at 12 weeks that their mental health was significantly better with clozapine than with new atypicals (p < 0.05). Net costs of care varied widely, but were higher than in band 1, with a mean of 33,800 pounds sterling in the clozapine group and 28,400 pounds sterling in the new atypical group. Of these costs, 4.0% and 3.3%, respectively, were due to antipsychotic drug costs. The increased costs in the clozapine group appeared to reflect the licensing requirement for inpatient admission for commencing the drug. There was a trend towards higher mean participant utility scores in the clozapine group. CONCLUSIONS: For band 1, there is no disadvantage in terms of quality of life and symptoms, or associated costs of care, over 1 year in commencing conventional antipsychotic drugs rather than new atypical drugs. Conventional drugs were associated with non-significantly better outcomes and lower costs. Drug costs represented a small proportion of the overall costs of care (<5%). For band 2, there is a statistically significant advantage in terms of symptoms but not quality of life over 1 year in commencing clozapine rather than new atypical drugs, but with increased associated costs of care. The results suggest that conventional antipsychotic drugs, which are substantially cheaper, still have a place in the treatment of patients unresponsive to, or intolerant of, current medication. Further analyses of this data set are planned and further research is recommended into areas such as current antipsychotic treatment guidance, valid measures of utility in serious mental illness, low-dose 'conventional' treatment in first episode schizophrenia, QLS validity and determinants of QLS score in schizophrenia, and into the possible financial and other mechanisms of rewarding clinician participation in trials.

Reduced glial cell density and neuronal size in the anterior cingulate cortex in major depressive disorder.

BACKGROUND: Glial cells are more numerous than neurons in the cortex and are crucial to neuronal function. There is evidence for reduced neuronal size in schizophrenia, with suggestive evidence for reduced glial cell density in mood disorders. In this investigation, we have simultaneously assessed glial cell density and neuronal density and size in the anterior cingulate cortex in schizophrenia, major depressive disorder, and bipolar disorder. METHODS: We examined tissue from area 24b of the supracallosal anterior cingulate cortex in 60 postmortem brain specimens from 4 groups of 15 subjects, as follows: major depressive disorder, schizophrenia, bipolar disorder, and normal controls. Glial cell density and neuronal size and density were examined in all subjects using the nucleator and the optical disector. RESULTS: Glial cell density (22%) (P =.004) and neuronal size (23%) (P =.01) were reduced in layer 6 in major depressive disorder compared with controls. There was some evidence for reduced glial density in layer 6 (20%) (P =.02) in schizophrenia compared with controls, before adjusting for multiple layerwise comparisons, but there were no significant changes in neuronal size. There was no evidence for differences in glial density or neuronal size in bipolar disorder compared with controls. Neuronal density was similar in all groups to that found in controls. CONCLUSION: These findings suggest that there is reduced frontal cortical glial cell density and neuronal size in major depressive disorder.

Lack of association between a polymorphism in the promoter region of the dopamine-2 receptor gene and clozapine response.

Dopamine receptors are strong candidates for involvement in schizophrenia and are targeted by a wide variety of antipsychotics. We hypothesized that genetic variation in these neurotransmitter receptors may influence clinical response to clozapine, an antipsychotic which displays high affinity for dopamine D2 receptors in the limbic system. To test this hypothesis, we studied a functional polymorphism in the promoter region of the D2 receptor gene (-141C Ins/Del) in a sample of 151 clozapine treated patients of British origin. In addition, the influence of this polymorphism on antipsychotic response in general was investigated on a sample of 146 Han Chinese schizophrenic patients treated with a variety of antipsychotics. No association was found between this polymorphism and clinical response in either of the two samples suggesting that genetic variation in D2 receptors does not play a major role in determining clinical response to antipsychotic treatment.

Identification of novel polymorphisms in the 5' flanking region of CYP1A2, characterization of interethnic variability, and investigation of their functional significance.

CYP1A2 activity has been demonstrated to be bimodally or trimodally distributed in several populations, consistent with a codominant or recessive functional genetic polymorphism. However, studies aimed at identifying polymorphisms in CYPIA2 have not yet adequately accounted for this distribution pattern. To search for functional polymorphisms, we performed genome-walking, polymerase chain reaction (PCR) sequencing, and cloning, and identified three novel polymorphisms in the 5' flanking region of CYP1A2: a T-3591G substitution, a G-3595T substitution, and a T-3605 insertion. The frequency of the T-3591G substitution was determined by a PCR-restriction fragment length polymorphism assay, and found to be significantly higher (P < 0.0001) in Taiwanese (allele frequency 0.128, n = 125) compared to Caucasians (0.017, n = 87) or African Americans (0.024, n = 104). The functional consequence of the T-3591G and the G-3595T substitutions was determined by site-directed mutagenesis followed by transient transfection experiments. The T-3591G mutation was shown to be nonfunctional, while although the G-3595T mutation appeared to result in an increase in promoter activity, this was only to a small degree and therefore unlikely to be important in vivo. In addition, we report 532 bases of 5' flanking sequence further upstream than that reported to date, and four sequence discrepancies compared to the original published sequence (G-3649C, deltaT-3650, deltaA-4072, and C-4093 ins).

Immunoautoradiographic evidence for a loss of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate-preferring non-N-methyl-D-aspartate glutamate receptors within the medial temporal lobe in schizophrenia.

Decreased expression of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-preferring non-N-methyl-D-aspartate (non-NMDA) glutamate receptors (GluRs) occurs in the medial temporal lobe of schizophrenics in terms of reduced abundance of GluR1 and GluR2 subunit mRNAs. To investigate further these receptors in schizophrenia, we have performed a quantitative immunoautoradiographic study in medial temporal lobe sections of 11 schizophrenics and 10 well-matched controls. GluR1 and GluR2/3 were detected with polyclonal antisera coupled to 35S-labeled secondary antibodies. Both subunits were vulnerable to a prolonged postmortem interval and poor agonal state as indicated by brain pH. GluR1 also tended to decline with increasing age. These factors were therefore used as covariates. GluR1 abundance was reduced in schizophrenics in parahippocampal gyrus (p < .025), while GluR2/3 was lower in most subfields in the schizophrenics, significantly so in CA4 (p < .02). The present data extend the evidence for decreased expression of the AMPA subtype of non-NMDA receptors in the medial temporal lobe in schizophrenia, although the magnitude and spatial extent of the loss is smaller than that affecting the encoding mRNAs. Impaired AMPA receptor expression is consistent with a neurodevelopmental origin and with hypotheses of glutamatergic hypofunction in the disease; however, its true pathophysiological significance and relationship to the other neuropathological and pathochemical abnormalities in the medial temporal lobe in schizophrenia remain to be determined.

Cognitive functioning and GABAA/benzodiazepine receptor binding in schizophrenia: a 123I-iomazenil SPET study.

BACKGROUND: The role of the inhibitory neurotransmitter gamma aminobutyric acid (GABA) in schizophrenia has previously been investigated using postmortem material. Recently, using single photon emission tomography (SPET) with the selective benzodiazepine antagonist 123I-Iomazenil as the radioligand, we have demonstrated an in vivo relationship between reduced GABAA/benzodiazepine receptor binding and the severity of positive symptomatology in schizophrenia. The present study aimed to build on this using the same in vivo scanning techniques, and relating findings to cognitive functioning. METHODS: Ten nonpsychiatric control subjects and 15 schizophrenic patients, matched for age and handedness, were scanned. A battery of neuropsychologic tests was also administered. RESULTS: Correlational analysis revealed a pattern of increased correlations between GABAA/benzodiazepine receptor binding and task performance, in the schizophrenic group compared to the control group. CONCLUSIONS: Findings are preliminary but suggest a relationship between reduced GABAA/benzodiazepine receptor binding and poorer cognitive functioning, involving memory and visual attention processes, in the schizophrenic group but not in the control group. A role for GABA in the pathophysiology of schizophrenia is suggested. Limitations of the present study and suggestions for future research are discussed.

Association analysis of the catechol O-methyltransferase gene and bipolar affective disorder.

OBJECTIVE: Catechol O-methyltransferase (COMT) is an enzyme that inactivates catecholamines. Two common COMT alleles determine high and low activity of the enzyme. Previous studies using biochemical methods found lower enzyme activity in patients with major depression and bipolar disorder in comparison with control values, suggesting that a dysfunction in catecholamine metabolism may be related to the etiology of depression. METHOD: The authors studied two recently described DNA polymorphisms at the COMT gene (a silent C256G mutation and a structural mutation, Val-108-Met) in 88 patients with bipolar disorder and in 113 healthy comparison subjects, all of Spanish origin. RESULTS: The frequency of the C256 allele was 0.58 in the patients and 0.54 in the comparison subjects. The frequency of the Val108 variant was 0.57 for both the patients and the comparison subjects. No allelic or genotypic associations were observed. CONCLUSIONS: The lack of association suggests that the COMT gene is not a major risk factor for bipolar disorder.

Correlation between reduced in vivo benzodiazepine receptor binding and severity of psychotic symptoms in schizophrenia.

OBJECTIVE: Although there is evidence from postmortem studies suggestive of deficient inhibitory neurotransmission of gamma-aminobutyric acid (GABA) in schizophrenia, no direct in vivo evidence has been obtained to date. The authors used single photon emission computed tomography (SPECT) with iodine-123-labeled iomazenil ([123I]iomazenil), a radioligand that selectively binds with high affinity to the benzodiazepine subunit of the GABAA receptor complex in the human brain, to investigate the presence of benzodiazepine receptor abnormalities in the cerebral cortex of living subjects with schizophrenia. METHOD: Dynamic [123I]iomazenil SPECT was performed in 15 patients (14 patients with DSM-III-R schizophrenia and one with schizophreniform disorder) and 12 healthy subjects over a period of 2 hours. The time-integral method was used to generate ratios of "specific" to "nonspecific" [123I]iomazenil binding at equilibrium for several cortical regions. RESULTS: No overall between-group differences in benzodiazepine receptor binding were found, but significant correlations emerged between the severity of schizophrenic symptoms and [123I]iomazenil binding in limbic cortical regions: positive symptom scores were negatively correlated with benzodiazepine receptor binding in the left medial temporal region, and negative symptoms were inversely related to receptor binding in the medial frontal region. These correlations were not significant when a Bonferroni correction for multiple comparisons was applied. CONCLUSIONS: These preliminary results are consistent with previous research implicating limbic cortical regions in the pathophysiology of schizophrenia, suggesting that reduced inhibitory GABAergic tone in these areas may contribute to the appearance of schizophrenic symptoms.

Schizophrenia: a neurodevelopmental perspective.

The role of aberrant neurodevelopment in the etiology of schizophrenia is reviewed in light of recent neuropathologic, neurochemical, and neuroimaging evidence of cerebral abnormalities in schizophrenic patients. There may exist some genetic defect in the control of brain development. Clinical epidemiologic surveys highlight the importance of obstetric complications, and prenatal exposure to influenza epidemics in contributing to these abnormalities. It is suggested that such environmental hazards and aberrations in the control of early brain development produce the neuronal phenotype that manifests as schizophrenia with early age of onset of symptoms associated with soft neurologic signs and is more common in young males.

Quantitative autoradiographic analysis of glutamate binding sites in the hippocampal formation in normal and schizophrenic brain post mortem.

Using quantitative autoradiography, the anatomical distribution of the binding sites (kainate, N-methyl-D-aspartate and quisqualate) for the excitatory neurotransmitter glutamate has been established in the hippocampal formation from control and schizophrenic brains, post mortem. There is a loss of the kainate subtype particularly in schizophrenic hippocampi mainly from the CA4/CA3 mossy fibre termination zone of the cornu ammonis (CA4 and CA3; control and schizophrenic left hippocampus, respectively, 54.2 and 66.6 pmol/g; 18.3 and 17.9 pmol/g), as well as bilateral losses in the dentate gyrus (left 14.2 pmol/g and right 28.0 pmol/g; left 9.5 pmol/g and right 7.9 pmol/g, control and schizophrenic, respectively) and parahippocampal gyrus (left 50.8 pmol/g and right 41.7 pmol/g, left 27.7 pmol/g and right 25.3 pmol/g, control and schizophrenic, respectively). There is complete preservation of N-methy-D-aspartate sites in schizophrenic hippocampi, and a marginally significant loss of the quisqualate binding site in CA4/CA3 regions (left 249 fmol/g and right 306 fmol/g, left 157 fmol/g and right 148 fmol/g, control and schizophrenic, respectively). These findings reflect the possible importance of glutamate in the pathophysiology of schizophrenia and represent novel targets for therapeutic manipulation in schizophrenia.

A comparison of the effects of acute and one year's continuous neuroleptic treatment on the release of [3H]glutamate and [3H]acetylcholine from rat striatal slices.

The effect of neuroleptic drugs administered acutely or continuously for 1 year on the release of [3H]glutamate and [3H]acetylcholine from striatal slices in vitro has been compared. Acute in vivo administration of haloperidol, trifluoperazine and clozapine increased the potassium-evoked release of [3H]acetylcholine from striatal slices in a dose-dependent fashion, whereas sulpiride was without effect. None of the neuroleptics given acutely had any effect on the potassium-evoked striatal release of [3H]glutamate. Potassium-evoked striatal release of [3H]acetylcholine in animals receiving 1 year's continuous administration of haloperidol, trifluoperazine or sulpiride was no different from that in age-matched control animals, but was less than controls in animals receiving clozapine for 1 year. All drugs caused a decrease in potassium-evoked striatal [3H]glutamate release following drug administration for 1 year compared to age-matched controls. The reversal of the acute action of neuroleptic drugs on striatal [3H]acetylcholine and [3H]glutamate release is consistent with a functional increase in striatal dopamine transmission following long-term neuroleptic treatment.

Thyrotrophin releasing hormone stimulates release of [3H]-dopamine from slices of rat nucleus accumbens in vitro.

Thyrotrophin releasing hormone (TRH) (25 to 100 microM) was found to stimulate the efflux of [3Hu-dopamine from small slices of rat nucleus accumbens, but not from similar slices of rat caudate nucleus. Uptake inhibition was not responsible for this action, since at 10 and 50 microM TRH had no effect on the ability of small slices of nucleus accumbens to accumulate radioactivity when incubated with 10(-7) M [3H]-dopamine. In addition the hormone had no effect on basal or dopamine-stimulated adenylate cyclase, nor did it displace [3H]-spiperone binding, in membrane preparations from nucleus accumbens.

The effect of sodium-n-dipropyl acetate on gamma-aminobutyric acid-dependent inhibition in the rat cortex and substantia nigra in relation to its anticonvulsant activity.

1. We have examined the time course of the anticonvulsant property of valproate sodium on electroshock-induced convulsions in rats and a comparison of this has been made with the action of the drug on single unit activity in the rat brain. 2. Intraperitoneal valproate sodium (100 to 400 mg/kg) protected rats from electroshock-induced convulsion. This effect was dose-dependent, the latency of the effect decreasing as a function of dose from 5 to 2 min. 3. The time course of this anticonvulsant property was paralleled by a pronounced inhibition of the spontaneous firing rate of cortical and nigral neurones, following intraperitoneal administration of valproate sodium (100 to 400 mg/kg). 4. The inhibitory action of microiontophoretically applied gamma-aminobutyric acid (GABA) and muscimol on the firing rate of cortical neurones was potentiated within 1 to 3 min of microiontophoretic application of valproate sodium. In contrast, the inhibitory action of glycine on cortical neurones was unaffected during the microiontophoretic application of valproate sodium. 5. Microiontophoretically applied valproate sodium also potentiated inhibitory responses to GABA in rats which had received 100 mg/kg of a GABA-transaminase inhibitor, gabaculine, i.p. 16 h previously. 6. The duration of trans-synaptic inhibitory responses in the substantia nigra and cortex following submaximal electrical stimulation of the striatum and cortex respectively was, in general, unaffected by either intraperitoneal or local application of valproate sodium. 7. These observations are discussed in terms of the mechanisms underlying the rapid onset of the anticonvulsant properties of valproate sodium.

Antidepressants enhance glucocorticoid receptor function in vitro by modulating the membrane steroid transporters.

1. Previous data demonstrate that the tricyclic antidepressant, desipramine, induces glucocorticoid receptor (GR) translocation from the cytoplasm to the nucleus in L929 cells and increases dexamethasone-induced GR-mediated gene transcription in L929 cells stably transfected with the mouse mammary tumour virus-chloramphenicol acetyltransferase (MMTV-CAT) reporter gene (LMCAT cells) (Pariante et al., 1997). 2. To extend these findings, the present study has investigated the effects of 24 h coincubation of LMCAT cells with dexamethasone and amitriptyline, clomipramine, paroxetine, citalopram or fluoxetine. 3. All antidepressants, except fluoxetine, enhanced GR-mediated gene transcription, with clomipramine having the greatest effect (10 fold increase). Twenty-four hours coincubation of cells with desipramine, clomipramine or paroxetine, also enhanced GR function in the presence of cortisol, but not of corticosterone. 4. It is proposed that these effects are due to the antidepressants inhibiting the L929 membrane steroid transporter, which actively extrudes dexamethasone and cortisol from the cell, but not corticosterone. This is further confirmed by the fact that clomipramine failed to enhance GR-mediated gene transcription in the presence of dexamethasone when the membrane steroid transporter was blocked by verapamil. 5. The membrane steroid transporters that regulate access of glucocorticoids to the brain in vivo, like the multiple drug resistance p-glycoprotein, could be a fundamental target for antidepressant action.

Pharmacogenetics for the individualization of psychiatric treatment.

Drug treatment of psychiatric disorders is troubled by severe adverse effects, low compliance and lack of efficacy in about 30% of patients. Pharmacogenetic research in psychiatry aims to elucidate the reasons for treatment failure and adverse reactions. Genetic variations in cytochrome P450 (CYP) enzymes have the potential to directly influence the efficacy and tolerability of commonly used antipsychotic and antidepressant drugs. The activity of psychiatric drugs can also be influenced by genetic alterations affecting the drug target molecule. These include the dopaminergic and serotonergic receptors, neurotransmitter transporters and other receptors and enzymes involved in psychiatric disorders. Association studies investigating the relation between genetic polymorphisms in metabolic enzymes and neurotransmitter receptors on psychiatric treatment outcome provide a step towards the individualization of psychiatric treatment through enabling the selection of the most beneficial drug according to the individual's genetic background.

Schizophrenia and the androgen receptor gene: report of a sibship showing co-segregation with Reifenstein syndrome but no evidence for linkage in 23 multiply affected families.

Crow et al. [1993: Am J Med Genet (Neuropsychiatr Genet) 48:159-160] have reported excess sharing of alleles by male sibling pairs with schizophrenia, at a triplet repeat marker within the androgen receptor gene, indicating that mutations at or near this gene may be a risk factor for males. In this report, we describe a pair of male siblings concordant for both schizophrenia and Reifenstein syndrome, which is caused by a mutation in this gene. This provides support for the hypothesis that the androgen receptor may contribute to liability to develop schizophrenia. Because of this, we have examined a collection of 23 pedigrees multiply affected by schizophrenia for linkage to the androgen receptor. We have found no evidence for linkage by both the LOD score and affected sibling-pair methods, under a range of genetic models with a broad and narrow definition of phenotype, and when families with male-to-male transmission are excluded. However, because of the small number of informative male-male pairs in our sample, we cannot confirm or refute the excess allele sharing for males reported by Crow.

Systematic screening of the 14-3-3 eta (eta) chain gene for polymorphic variants and case-control analysis in schizophrenia.

The neuronal protein 14-3-3 eta is a candidate gene for schizophrenia because it maps chromosome 22q12, a region implicated in the disease by linkage analysis, and is involved in brain development. We systematically screened this gene for polymorphic variants by comparison of public EST sequence data (five cDNAs and 72 ESTs, 21,155 bp of sequence) in parallel with single-stranded conformational polymorphism analysis, and we compared these methods by using a simple power calculation. Twelve potential polymorphisms were identified from EST sequence comparison, and two of these (a 5'-VNTR and 753G/A) were confirmed by SSCP analysis and sequencing. Three additional infrequent polymorphisms (-408T/G; 177 C/G; and 989 A/G) were found by SSCP only. We next examined these variants for association with schizophrenia. One variant in untranslated region of exon 1 (-408 T/G) was found to occur more frequently in the schizophrenic subjects (8%) than the controls (3%; P = 0.01). After fivefold correction of the P value for multiple testing, marginal association was found. Haplotype analysis of pairs of polymorphisms provided no evidence for association of this gene with schizophrenia in the population studied. Am. J. Med. Genet. (Neuropsychiatr. Genet. ) 96:736-743, 2000.

Analysis of clozapine response and polymorphisms of the dopamine D4 receptor gene (DRD4) in schizophrenic patients.

We have examined the hypothesis that a variable number of tandem repeats in the third cytoplasmic loop of the dopamine D4 receptor influences clinical response to clozapine using a sample of 189 schizophrenic patients. Alleles of the 48-bp repeat, which range from two to ten copies in the normal human population, were analysed by the polymerase chain reaction using genomic DNA as template. Association between these alleles and response to clozapine was tested using the difference in pre- and post-treatment GAS scores as a measure of response. We found no statistically significant variation between genotypic groups and response by analysis of variance. We conclude that the variation of the number of 48-bp repeats alone does not determine response to clozapine. Larger studies are underway to determine if there is a more subtle relationship with sequence variation within the repeats or at other polymorphic sites within the gene that may provide evidence for a component of clozapine's action being at D4 receptors.