Molecular signatures associated with cognitive deficits in schizophrenia: a study of biopsied olfactory neural epithelium.

Cognitive impairment is a key feature of schizophrenia (SZ) and determines functional outcome. Nonetheless, molecular signatures in neuronal tissues that associate with deficits are not well understood. We conducted nasal biopsy to obtain olfactory epithelium from patients with SZ and control subjects. The neural layers from the biopsied epithelium were enriched by laser-captured microdissection. We then performed an unbiased microarray expression study and implemented a systematic neuropsychological assessment on the same participants. The differentially regulated genes in SZ were further filtered based on correlation with neuropsychological traits. This strategy identified the SMAD 5 gene, and real-time quantitative PCR analysis also supports downregulation of the SMAD pathway in SZ. The SMAD pathway has been important in multiple tissues, including the role for neurodevelopment and bone formation. Here the involvement of the pathway in adult brain function is suggested. This exploratory study establishes a strategy to better identify neuronal molecular signatures that are potentially associated with mental illness and cognitive deficits. We propose that the SMAD pathway may be a novel target in addressing cognitive deficit of SZ in future studies.

Nuclear DISC1 regulates CRE-mediated gene transcription and sleep homeostasis in the fruit fly.

Disrupted-in-schizophrenia-1 (DISC1) is one of major susceptibility factors for a wide range of mental illnesses, including schizophrenia, bipolar disorder, major depression and autism spectrum conditions. DISC1 is located in several subcellular domains, such as the centrosome and the nucleus, and interacts with various proteins, including NudE-like (NUDEL/NDEL1) and activating transcription factor 4 (ATF4)/CREB2. Nevertheless, a role for DISC1 in vivo remains to be elucidated. Therefore, we have generated a Drosophila model for examining normal functions of DISC1 in living organisms. DISC1 transgenic flies with preferential accumulation of exogenous human DISC1 in the nucleus display disturbance in sleep homeostasis, which has been reportedly associated with CREB signaling/CRE-mediated gene transcription. Thus, in mammalian cells, we characterized nuclear DISC1, and identified a subset of nuclear DISC1 that colocalizes with the promyelocytic leukemia (PML) bodies, a nuclear compartment for gene transcription. Furthermore, we identified three functional cis-elements that regulate the nuclear localization of DISC1. We also report that DISC1 interacts with ATF4/CREB2 and a corepressor N-CoR, modulating CRE-mediated gene transcription.

Functional sites of neuroleptic drug action in the human brain: PET/FDG studies with and without haloperidol.

OBJECTIVE: The functional pathways through which antipsychotic drugs act in the brain to decrease psychosis remain unknown, despite our knowledge that their site of initial action is through blockade of dopamine D2 receptors. The authors sought to define the brain regions that are functionally altered by neuroleptic drugs. METHODS: Regional cerebral glucose metabolism was studied in 12 subjects with schizophrenia while they were receiving a fixed dose of haloperidol, again 5 days after withdrawal of the drug, and a third time 30 days after withdrawal. Positron emission tomography with an [18F]fluorodeoxyglucose tracer was used in a within-subject design. RESULTS: The analysis demonstrated a decrease in glucose metabolism in the caudate and putamen 30 days after withdrawal, indicating that haloperidol treatment enhanced glucose utilization in these areas. The thalamus, bilaterally but only in anterior areas, showed the same response to haloperidol. Only in the frontal cortex and in the anterior cingulate had metabolism increased 30 days after withdrawal, indicating that in those two cortical areas haloperidol depressed glucose metabolism. In the 5-day drug free scans, no regions differed significantly from those in the haloperidol condition, despite numerical changes. CONCLUSIONS: It appears that 5 days of neuroleptic withdrawal are inadequate to escape the effects of neuroleptic drugs on regional cerebral glucose metabolism. The pattern and localization of changes in metabolic activity between the haloperidol condition and the 30-day drug-free condition suggest that haloperidol exerts its primary antidopaminergic action in the basal ganglia. It is proposed that the additional changes in the thalamus and cortex are secondary to this primary site of drug action, mediated through classically described striato-thalamo-cortical pathways.

Abnormal smooth pursuit eye movements in schizophrenic patients are associated with cerebral glucose metabolism in oculomotor regions.

The purpose of this study was to test the hypothesis that abnormal smooth pursuit eye movements in schizophrenic patients would be related to cerebral glucose utilization in specific oculomotor regions. Eye movements were assessed with infrared oculography in 11 unmedicated schizophrenic patients and 13 normal comparison subjects. For the patients only, regional cerebral metabolic rate of glucose utilization was measured with positron emission tomography. Abnormal pursuit tracking in the patients was associated with relatively decreased metabolism in the frontal eye fields and increased metabolism in the caudate nuclei. The results are consistent with the hypothesis that these cerebral regions are involved in the pathophysiology of abnormal pursuit as related parts of a cortical-subcortical oculomotor circuit.

Savoxepine fails to selectively influence glucose metabolism in the rat limbic system.

The [14C]-2-deoxyglucose method was used to map the in vivo metabolic response of glucose to savoxepine, a novel tetracyclic cyano-dibenzoxepino-azepine. Savoxepine is reported to have higher affinity for dopamine (DA) receptors in the hippocampus than in the striatum and hence should have dose-dependent, anatomically selective actions. Two doses of savoxepine (0.05 mg/kg and 0.5 mg/kg) were compared with haloperidol (1 mg/kg) to test the hypothesis that low doses of savoxepine would display a selective action on limbic brain areas. Results failed to show that low dose savoxepine selectively modifies glucose utilization in the limbic system as previous biochemical studies suggested. In fact, low doses of the drug displayed a potent activity quite similar to haloperidol in effect and localization. The low dose did not produce significantly altered glucose metabolism in the nucleus accumbens or in the lateral habenular nucleus as observed with most other neuroleptics, suggesting a lack of antipsychotic action at this dose. Our findings demonstrate the difficulty of designing a neuroleptic with a preferential blockade of limbic DA receptors and point to the need for functional assessment of regional receptor binding differences.

Impulsiveness and subjective effects of intravenous cocaine administration in the laboratory.

Cardiovascular and subjective responses to placebo and 40-mg intravenous (iv) cocaine injections were measured in 29 male iv cocaine users: most subjects received each of these injections on two separate occasions. Most of the subjects also completed various measures of psychopathology and personality. Although the small sample size made any conclusions tentative, an expected significant association between impulsivity and subjective euphoria following 40-mg cocaine administration was obtained, whereas associations of personality measures with cardiovascular responses to cocaine administration were inconsistent.

d-cycloserine adjuvant therapy to conventional neuroleptic treatment in schizophrenia: an open-label study.

D-cycloserine, a partial agonist at the strychnine-insensitive glycine site of the NMDA receptor complex, was tested as adjuvant treatment to conventional neuroleptics in chronic schizophrenic volunteers. The drug was administered, o.a.d., at the daily dose of 250 mg for six weeks. Mental status outcome measures were completed at the end of each week of treatment. The major finding was a deterioration of the patients' clinical condition, specifically of their psychotic symptoms. These preliminary results are discussed among others in view of d-cycloserine pharmacologic properties and recent findings on the interaction between NMDA agonists and dopamine system. This study, finally, suggests the need for a controlled dose-finding trial to establish the activity and a therapeutic "window" of this drug in schizophrenia.

Sensitivity to subjective effects of cocaine in drug abusers: relationship to cerebral ventricle size.

OBJECTIVE: The purpose of this study was to assess the functional significance of ventricle-brain ratio (VBR) in terms of how it might affect sensitivity to cocaine, an indirect dopamine agonist. METHOD: Relationships between VBR and subjective responses to acute intravenous cocaine hydrochloride were examined in 20 male polydrug abusers. Tests were performed in conjunction with positron emission tomography scans to measure cerebral glucose metabolism. RESULTS: Subjective measures of effects of cocaine, including self-report ratings of intensity of the drug effect, scores on the morphine-benzedrine scale of the Addiction Research Center Inventory, and several items on visual analogue scales, correlated negatively with VBR. VBR also differed significantly among subjects who were grouped according to scores on items ("rush" and "crash") of the Cocaine-Sensitive Scale (larger VBR in subjects with weaker responses). VBR was not correlated with cocaine-induced changes in cerebral metabolic rates for glucose. CONCLUSIONS: Relative insensitivity to the subjective effects of cocaine in polydrug abusers with ventricle enlargement suggests that ventriculomegaly may reflect changes in periventricular brain regions that mediate these effects of cocaine.

PET-FDG test-retest reliability during a visual discrimination task in schizophrenia.

OBJECTIVE: Reliability of assessment is important in any kind of neuropsychiatric study, but is particularly pivotal in schizophrenia research where symptom instability is common. MATERIALS AND METHODS: Two fluorodeoxyglucose PET scans, 1 week apart, were carried out in schizophrenic patients while they were performing a simple visual discrimination task. Subject and scan conditions were held constant. Regional metabolic rates of glucose utilization were calculated as absolute and scaled; they were compared using correlational statistics. RESULTS: Average differences between scans were 5-9% for the parietal and occipital cortices, but 1-3% for other cortical areas, differences comparable with reported variances in normal controls. CONCLUSION: These results suggest that test-retest variance in metabolic imaging in schizophrenia is relatively low and that task performance increases metabolic stability in brain areas unrelated to task performance.

Pharmacologic properties of (-)-3PPP (preclamol) in man.

The dopamine (DA) autoreceptor agonist (-)-3PPP (preclamol) was tested in male schizophrenic volunteers for safety. The drug was administered intramuscularly in a single rising dose design, crossed with a similar "rising dose" placebo period; all evaluations and raters were blind to drug or placebo administration. Pharmacokinetic, endocrine, safety, and mental status outcome measures were completed before and after each single dose of drug or placebo. Pharmacokinetic analysis showed blood levels between 200-500 pmoles/ml after the intramuscular drug doses of 30-40 mg. Drug half life is 2-2.5 hrs. Growth hormone (GH) levels were elevated in a linear fashion to the 30 mg dose; whereafter, the drug failed to affect GH at all. All safety evaluations were negative, including any untoward effects on the major organ systems. After single dose drug administration, evidence of antipsychotic action occurred in two of the four subjects. This study suggests that (-)-3PPP/preclamol is a safe drug for study in the treatment of schizophrenia and may have antipsychotic efficacy.

Effects of substance abuse on ventricular and sulcal measures assessed by computerised tomography.

Computerised tomography (CT) was used to assess the possible effects of substance abuse on brain morphology. Polydrug abusers had significantly wider third ventricles than normal controls, with a positive correlation between age and ventricle:brain ratio (VBR). Assuming no effect of age, estimated quantity of substance abuse was not significantly related to ventricular and sulcal measures, except that alcohol consumption correlated positively with VBR and severity of cocaine use correlated negatively with sulcal width. When age of the subjects was partialled out, alcohol use showed a tendency for association with VBR; however, severity of cocaine use did not remain a significant predictor of cortical sulcal width. The findings suggest that chronic use of alcohol, but not necessarily of other commonly abused substances, produces brain atrophy.

Program for PET image alignment: effects on calculated differences in cerebral metabolic rates for glucose.

A program was developed to align positron emission tomography images from multiple studies on the same subject. The program allowed alignment of two images with a fineness of one-tenth the width of a pixel. The indications and effects of misalignment were assessed in eight subjects from a placebo-controlled double-blind crossover study on the effects of cocaine on regional cerebral metabolic rates for glucose. Visual examination of a difference image provided a sensitive and accurate tool for assessing image alignment. Image alignment within 2.8 mm was essential to reduce variability of measured cerebral metabolic rates for glucose. Misalignment by this amount introduced errors on the order of 20% in the computed metabolic rate for glucose. These errors propagate to the difference between metabolic rates for a subject measured in basal versus perturbed states.

Cocaine-induced reduction of glucose utilization in human brain. A study using positron emission tomography and [fluorine 18]-fluorodeoxyglucose.

We examined the effects of cocaine hydrochloride (40 mg intravenously) on regional cerebral metabolic rates for glucose and on subjective self-reports of eight polydrug abusers in a double-blind, placebo-controlled, crossover study. The regional cerebral metabolic rate for glucose was measured by the [fluorine 18]-fluorodeoxyglucose method, using positron emission tomography. With eyes covered, subjects listened to a tape that presented white noise, "beep" prompts, and questions about subjective effects of cocaine or saline. Cocaine produced euphoria and reduced glucose utilization globally (mean reduction, 14%). Twenty-six of 29 brain regions (all neocortical areas, basal ganglia, portions of the hippocampal formation, thalamus, and midbrain) showed significant decrements (5% to 26%) in the regional cerebral metabolic rate for glucose. No significant effects of cocaine were observed in the pons, the cerebellar cortex, or the vermis. Right-greater-than-left hemispheric asymmetry of regional cerebral metabolic rates for glucose occurred in the lateral thalamus. The findings demonstrate that reduced cerebral metabolism is associated with cocaine-induced euphoria.

Morphine-induced metabolic changes in human brain. Studies with positron emission tomography and [fluorine 18]fluorodeoxyglucose.

Morphine sulfate effects (30 mg, intramuscularly) on cerebral glucose utilization and subjective self-reports were examined in 12 polydrug abusers by positron emission tomography and [fluorine 18]fluorodeoxyglucose in a double-blind placebo-controlled crossover study. During testing, subjects sat with eyes covered, listening to white noise and "beep" prompts. Morphine significantly reduced glucose utilization by 10% in whole brain and by about 5% to 15% in telencephalic areas and the cerebellar cortex, assuming no contribution of hypercapnia. When the contribution of PaCO2 (45 minutes after morphine was administered) was partialled out, significant morphine-induced reductions persisted in whole brain and six cortical areas. Irrespective of morphine, left-greater-than-right asymmetry occurred in the temporal cortex, and an interaction between hemisphere and drug was noted in the postcentral gyrus. In most cases, effects on glucose utilization were not significantly related to measures of euphoria.

Placebo responses to cocaine administration in humans: effects of prior administrations and verbal instructions.

Subjective and physiological responses of eight male cocaine-using research volunteers were studied after a double-blind saline infusion (placebo) was given when subjects were instructed that a cocaine infusion might be given. Cardiovascular and subjective responses to placebo were similar in pattern and direction, though of lesser magnitude, than after a 40 mg cocaine infusion. These placebo responses were compared to responses after an earlier saline infusion condition in which subjects were instructed prior to the infusion that they would receive saline (instructed placebo). The design was thus meant to test for the effects of instructions on placebo responses to cocaine. Heart rates at baseline (pre-infusion) were significantly higher in the placebo than in the instructed placebo condition. Similar trends were found for elevated baseline placebo responses on two subjective effects measures. A comparison with an initial placebo session prior to the placebo and instructed placebo conditions described above provided evidence for conditioning of placebo responses on diastolic blood pressure and heart rate. The present results suggest that verbal instructions, as well as conditioning in the laboratory, could contribute to the observed placebo responses to cocaine infusions.

Cocaine-induced cocaine craving.

In nine experienced users of cocaine, we examined the urge to use cocaine or other drugs following a 40 mg dose of intravenous (IV) cocaine with and without oral pretreatment with 2.5 mg bromocriptine. The urge to use cocaine was assessed with a questionnaire constructed to assess both "wanting" and "craving" for cocaine or other drugs. Fifteen minutes after the administration of cocaine (but not after placebo), subjects' ratings for both drug "wanting" and drug "craving" were significantly increased. Our results provide a laboratory demonstration of cocaine-induced increases in the urge to use drugs in humans. The findings, stressing the role of internal stimuli associated with drug administration, suggest the possibility of distinguishing among related, but perhaps distinct, components of the fluctuating levels of motivation to reuse drugs.