Schizophrenia: from developmental deviance to dopamine dysregulation

Schizophrenia mediating the effect of smoking phenotypes on antisocial behavior: A Mendelian randomization analysis

AIMS

Previous studies have indicated that smoking is linked to an increased risk of developing schizophrenia, and that individuals with schizophrenia are more prone to engaging in antisocial behavior. However, the causal effects of smoking behaviors on antisocial behavior and the potential mediating role of schizophrenia remains largely unclear.

METHODS

In the present study, using the summary data from genome wide association studies of smoking phenotypes (N = 323,386-805,431), schizophrenia (Ncases = 53,386, Ncontrols = 77,258), and antisocial behavior (N = 85,359), we assessed bidirectional causality between smoking phenotypes and schizophrenia by the Mendelian randomization (MR) approach. Using a two-step MR approach, we further examined whether causal effects of smoking phenotypes/schizophrenia on antisocial behavior were mediated by schizophrenia/smoking phenotypes.

RESULTS

The results showed that smoking initiation (SmkInit) and age of smoking initiation (AgeSmk) causally increase the risk of schizophrenia (SmkInit: OR = 2.06, 95% CI = 1.77-2.39, p = 4.36 × 10-21 ; AgeSmk: OR = 0.32, 95% CI = 0.16-0.62, p = 8.11 × 10-4 , Bonferroni corrected). However, there was no causal effect that liability to schizophrenia leads to smoking phenotypes. MR evidence also revealed causal influences of SmkInit and the amount smoked (CigDay) on antisocial behavior (SmkInit: OR = 1.28, 95% CI = 1.17-1.41, p = 2.53 × 10-7 ; CigDay: OR = 1.16, 95% CI = 1.06-1.27, p = 1.60 × 10-3 , Bonferroni corrected). Furthermore, the mediation analysis indicated that the relationship between SmkInit and antisocial behavior was partly mediated by schizophrenia (mediated proportion = 6.92%, 95% CI = 0.004-0.03, p = 9.66 × 10-3 ).

CONCLUSIONS

These results provide compelling evidence for taking smoking interventions as a prevention strategy for schizophrenia and its related antisocial behavior.

The development of compulsive coping behavior depends on dorsolateral striatum dopamine-dependent mechanisms

Humans greatly differ in how they cope with stress, a natural behavior learnt through negative reinforcement. Some individuals engage in displacement activities, others in exercise or comfort eating, and others still in alcohol use. Across species, adjunctive behaviors, such as polydipsic drinking, are used as a form of displacement activity that reduces stress. Some individuals, in particular those that use alcohol to self-medicate, tend to lose control over such coping behaviors, which become excessive and compulsive. However, the psychological and neural mechanisms underlying this individual vulnerability have not been elucidated. Here we tested the hypothesis that the development of compulsive adjunctive behaviors stems from the functional engagement of the dorsolateral striatum (DLS) dopamine-dependent habit system after a prolonged history of adjunctive responding. We measured in longitudinal studies in male Sprague Dawley rats the sensitivity of early established vs compulsive polydipsic water or alcohol drinking to a bilateral infusion into the anterior DLS (aDLS) of the dopamine receptor antagonist α-flupentixol. While most rats acquired a polydipsic drinking response with water, others only did so with alcohol. Whether drinking water or alcohol, the acquisition of this coping response was insensitive to aDLS dopamine receptor blockade. In contrast, after prolonged experience, adjunctive drinking became dependent on aDLS dopamine at a time when it was compulsive in vulnerable individuals. These data suggest that habits may develop out of negative reinforcement and that the engagement of their underlying striatal system is necessary for the manifestation of compulsive adjunctive behaviors.

Prenatal nicotine exposure during pregnancy results in adverse neurodevelopmental alterations and neurobehavioral deficits

Maternal tobacco use and nicotine exposure during pregnancy have been associated with adverse birth outcomes in infants and can lead to preventable pregnancy complications. Exposure to nicotine and other compounds in tobacco and electronic cigarettes (e-cigarettes) has been shown to increases the risk of miscarriage, prematurity, stillbirth, low birth weight, perinatal morbidity, and sudden infant death syndrome (SIDS). Additionally, recent data provided by clinical and pre-clinical research demonstrates that nicotine exposure during pregnancy may heighten the risk for adverse neurodevelopmental disorders such as Attention-Deficit Hyperactivity (ADHD), anxiety, and depression along with altering the infants underlying brain circuitry, response to neurotransmitters, and brain volume. In the United States, one in 14 women (7.2%) reported to have smoked cigarettes during their pregnancy with the global prevalence of smoking during pregnancy estimated to be 1.7%. Approximately 1.1% of women in the United States also reported to have used e-cigarettes during the last 3 months of pregnancy. Due to the large percentage of women utilizing nicotine products during pregnancy in the United States and globally, this review seeks to centralize pre-clinical and clinical studies focused on the neurobehavioral and neurodevelopmental complications associated with prenatal nicotine exposure (PNE) such as alterations to the hypothalamic-pituitary-adrenal (HPA) axis and brain regions such as the prefrontal cortex (PFC), ventral tegmental area (VTA), nucleus accumbens (NA), hippocampus, and caudate as well as changes to nAChR and cholinergic receptor signaling, long-term drug seeking behavior following PNE, and other related developmental disorders. Current literature analyzing the association between PNE and the risk for offspring developing schizophrenia, attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), anxiety, and obesity will also be discussed.

Use of a Bayesian Network Model to predict psychiatric illness in individuals with 'at risk mental states' from a general population cohort

The 'at risk mental state' (ARMS) paradigm has been introduced in psychiatry to study prodromal phases of schizophrenia. With time it was seen that the ARMS state can also precede mental disorders other than schizophrenia, such as depression and anxiety. However, several problems hamper the paradigm's use in preventative medicine, such as varying transition rates across studies, the use of non-naturalistic samples, and the multifactorial nature of psychiatric disorders. To strengthen ARMS predictive power, there is a need for a holistic model incorporating-in an unbiased fashion-the small-effect factors that cause mental disorders. Bayesian networks, a probabilistic graphical model, was used in a populational cohort of 83 ARMS individuals to predict conversion to psychiatric illness. Nine predictors-including state, trait, biological and environmental factors-were inputted. Dopamine receptor 2 polymorphism, high private religiosity, and childhood trauma remained in the final model, which reached an 85.51% (SD = 0.1190) accuracy level in predicting conversion. This is the first time a robust model was produced with Bayesian networks to predict psychiatric illness among at risk individuals from the general population. This could be an important tool to strengthen predictive measures in psychiatry which should be replicated in larger samples to provide the model further learning.

Effects of Psychostimulants and Antipsychotics on Serum Lipids in an Animal Model for Schizophrenia

Schizophrenia (SCZ) treatment is essentially limited to the use of typical or atypical antipsychotic drugs, which suppress the main symptoms of this mental disorder. Metabolic syndrome is often reported in patients with SCZ under long-term drug treatment, but little is known about the alteration of lipid metabolism induced by antipsychotic use. In this study, we evaluated the blood serum lipids of a validated animal model for SCZ (Spontaneously Hypertensive Rat, SHR), and a normal control rat strain (Normotensive Wistar Rat, NWR), after long-term treatment (30 days) with typical haloperidol (HAL) or atypical clozapine (CLZ) antipsychotics. Moreover, psychostimulants, amphetamine (AMPH) or lisdexamfetamine (LSDX), were administered to NWR animals aiming to mimic the human first episode of psychosis, and the effects on serum lipids were also evaluated. Discrepancies in lipids between SHR and NWR animals, which included increased total lipids and decreased phospholipids in SHR compared with NWR, were similar to the differences previously reported for SCZ patients relative to healthy controls. Administration of psychostimulants in NWR decreased omega-3, which was also decreased in the first episode of psychosis of SCZ. Moreover, choline glycerophospholipids allowed us to distinguish the effects of CLZ in SHR. Thus, changes in the lipid metabolism in SHR seem to be reversed by the long-term treatment with the atypical antipsychotic CLZ, which was under the same condition described to reverse the SCZ-like endophenotypes of this validated animal model for SCZ. These data open new insights for understanding the potential influence of the treatment with typical or atypical antipsychotics on circulating lipids. This may represent an outcome effect from metabolic pathways that regulate lipids synthesis and breakdown, which may be reflecting a cell lipids dysfunction in SCZ.

Effects of Doxycycline in Swiss Mice Predictive Models of Schizophrenia

Schizophrenia patients show very complex symptoms in several psychopathological domains. Some of these symptoms remain poorly treated. Therefore, continued effort is needed to find novel pharmacological strategies for improving schizophrenia symptoms. Recently, minocycline, a second-generation tetracycline, has been suggested as an adjunctive treatment for schizophrenia. The antipsychotic-like effect of doxycycline, a minocycline analog, was investigated here. We found that both minocycline and doxycycline prevented amphetamine-induced prepulse inhibition (PPI) disruption. However, neither of them blocked MK801-induced effects, albeit doxycycline had a modest impact against ketamine-induced effects. Neither c-Fos nor nNOS expression, which was evaluated in limbic regions, were modified after acute or sub-chronic treatment with doxycycline. Therefore, apomorphine inducing either PPI disruption and climbing behavior was not prevented by doxycycline. This result discards a direct blockade of D2-like receptors, also suggested by the lack of doxycycline cataleptic-induced effect. Contrasting, doxycycline prevented SKF 38393-induced effects, suggesting a preferential doxycycline action at D1-like rather than D2-like receptors. However, doxycycline did not bind to the orthosteric sites of D1, D2, D3, D4, 5-HT2A, 5-HT1A, and A2A receptors suggesting no direct modulation of these receptors. Our data corroborate the antipsychotic-like effect of doxycycline. However, these effects are probably not mediated by doxycycline direct interaction with classical receptors enrolled in the antipsychotic effect.

Urbanicity: The need for new avenues to explore the link between urban living and psychosis

AIM

A growing body of evidence suggests that urban living contributes to the development of psychosis. However, the mechanisms underlying this phenomenon remain unclear. This paper aims to explore the best available knowledge on the matter, identify research gaps and outline future prospects for research strategies.

METHOD

A comprehensive literature survey on the main computerized medical research databases, with a time limit up to August 2017 on the issue of urbanicity and psychosis has been conducted.

RESULTS

The impact of urbanicity may result from a wide range of factors (from urban material features to stressful impact of social life) leading to "urban stress." The latter may link urban upbringing to the development of psychosis through overlapping neuro- and socio-developmental pathways, possibly unified by dopaminergic hyperactivity in mesocorticolimbic system. However, "urban stress" is poorly defined and research based on patients' experience of the urban environment is scarce.

CONCLUSIONS

Despite accumulated data, the majority of studies conducted so far failed to explain how specific factors of urban environment combine in patients' daily life to create protective or disruptive milieus. This undermines the translation of a vast epidemiological knowledge into effective therapeutic and urbanistic developments. New studies on urbanicity should therefore be more interdisciplinary, bridging knowledge from different disciplines (psychiatry, epidemiology, human geography, urbanism, etc.) in order to enrich research methods, ensure the development of effective treatment and preventive strategies as well as create urban environments that will contribute to mental well-being.

Contribution of CB2 receptors in schizophrenia-related symptoms in various animal models: Short review

Schizophrenia is a severe and chronic mental disease with a high prevalence and a variety of symptoms. Data from behavioural studies suggest that it is rational to investigate the endocannabinoid system (ECS) and its cannabinoid receptor (CBr) because they seem to underlie susceptibility to schizophrenia, and these findings have pointed to several lines of future research. Currently, most available studies address the role of CBr type 1 in schizophrenia-like responses. Here, we present for the first time, a review that demonstrates the pivotal role of CBr type 2 in the regulation of neurobiological processes underlying cognition, psychosis- and mood-related (anxiety, depression) behaviours, all of which may be included in schizophrenia symptoms. This review is based on available evidence from the PubMed database regarding schizophrenia-like symptoms induced via CB2r modulation in various animal models. The data presented in this manuscript indicate that CB2r could be a promising new key target in the treatment of different central nervous system (CNS) disorders, which manifest as psychosis, mood-related disturbances and/or memory impairment.

Are CB2 Receptors a New Target for Schizophrenia Treatment?

Schizophrenia is a complex disorder that involves several neurotransmitters such as dopamine, glutamate, and GABA. More recently, the endocannabinoid system has also been associated with this disorder. Although initially described as present mostly in the periphery, cannabinoid type-2 (CB2) receptors are now proposed to play a role in several brain processes related to schizophrenia, such as modulation of dopaminergic neurotransmission, microglial activation, and neuroplastic changes induced by stress. Here, we reviewed studies describing the involvement of the CB2 receptor in these processes and their association with the pathophysiology of schizophrenia. Taken together, these pieces of evidence indicate that CB2 receptor may emerge as a new target for the development of antipsychotic drugs.

A Peptide Link Between Human Cytomegalovirus Infection, Neuronal Migration, and Psychosis

Alongside biological, psychological, and social risk factors, psychotic syndromes may be related to disturbances of neuronal migration. This highly complex process characterizes the developing brain of the fetus, the early postnatal brain, and the adult brain, as reflected by changes within the subventricular zone and the dentate gyrus of the hippocampus, where neurogenesis persists throughout life. Psychosis also appears to be linked to human cytomegalovirus (HCMV) infection. However, little is known about the connection between psychosis, HCMV infection, and disruption of neuronal migration. The present study addresses the hypothesis that HCMV infection may lead to mental disorders through mechanisms of autoimmune cross-reactivity. Searching for common peptides that underlie immune cross-reactions, the analyses focus on HCMV and human proteins involved in neuronal migration. Results demonstrate a large overlap of viral peptides with human proteins associated with neuronal migration, such as ventral anterior homeobox 1 and cell adhesion molecule 1 implicated in GABAergic and glutamatergic neurotransmission. The present findings support the possibility of immune cross-reactivity between HCMV and human proteins that-when altered, mutated, or improperly functioning-may disrupt normal neuronal migration. In addition, these findings are consistent with a molecular and mechanistic framework for pathological sequences of events, beginning with HCMV infection, followed by immune activation, cross-reactivity, and neuronal protein variations that may ultimately contribute to the emergence of mental disorders, including psychosis.

Significant repetition probability effects in schizophrenia

BACKGROUND

A growing body of evidence suggests that the comparison of expected and incoming sensory stimuli (the prediction-error (ε) processing) is impaired in schizophrenia patients (SZ). For example, in studies of mismatch negativity, an ERP component that signals ε, SZ patients show deficits in the auditory and visual modalities. To test the role of impaired ε processing further in SZ, using neuroimaging methods, we applied a repetition-suppression (RS) paradigm.

METHODS

Patients diagnosed with SZ (n = 17) as well as age- and sex- matched healthy control subjects (HC, n = 17) were presented with pairs of faces, which could either repeat or alternate. Additionally, the likelihood of repetition/alternation trials was modulated in individual blocks of fMRI recordings, testing the effects of repetition probability (P(rep)) on RS.

RESULTS

We found a significant RS in the fusiform and occipital face areas as well as in the lateral occipital cortex that was similar in healthy controls and SZ patients SZ. More importantly, we observed similar P(rep) effects (larger RS in blocks with high frequency of repetitions than in blocks with low repetition likelihood) in both the control and the patient group.

CONCLUSION

Our findings suggest that repetition_probability modulations affect the neural responses in schizophrenia patients and healthy participants similarly. This suggests that the neural mechanisms determining perceptual inferences based on stimulus probabilities remain unimpaired in schizophrenia.

The effect of minocycline on symptoms in schizophrenia: Results from a randomized controlled trial

BACKGROUND

Studies have hypothesized that immunological abnormalities might contribute to schizophrenia, and basic science studies, as well as several clinical trials suggest that minocycline could be efficacious in ameliorating both positive and negative symptoms of schizophrenia. In this study we examined the effect of minocycline on schizophrenia in a large randomized controlled trial.

METHODS

We performed a 16-week, multi-center, double-blind, randomized, placebo-controlled study on 200 subjects with schizophrenia or schizoaffective disorder randomized to receive either minocycline (200 mg/day, n = 100), or placebo (n = 100) as an add-on to anti-psychotic treatment. The primary outcome measure was the PANSS total score.

RESULTS

Mixed models for repeated measures showed no significant difference between minocycline and placebo for total PANSS (p = 0.862), PANSS subscales, CGI or BACS.

CONCLUSIONS

Minocycline did not improve symptoms or cognition in schizophrenia.

Effect of Vaccinium macrocarpon on MK-801-induced psychosis in mice

OBJECTIVES

This study was aimed to investigate the effect of aqueous cranberry extract (ACE) on MK-801-induced psychosis in mice.

MATERIALS AND METHODS

MK-801-treated mice were administered ACE (1 and 2 g/kg, p.o.) for 14 days. Various behavioral parameters and neurochemical estimations such as dopamine (DA), 5-hydroxytryptamine (5-HT), norepinephrine (NE), gamma-aminobutyric acid (GABA), glutamate, and glycine as well as markers of oxidative stress such as nitrite levels were measured.

RESULTS

Psychosis-induced mice showed a significant elevation of immobility time in forced swim test, locomotor activity, and reduction in time of permanency in rota-rod test, escape latency time in Cook's pole test while treatment with ACE showed a significant alteration in above-mentioned behavioral parameters in MK-801-induced psychosis. Moreover, MK-801-induced psychosis in the mice showed a significant increase in DA, 5-HT, and NA levels and decrease in GABA, glutamate, and glycine levels in the brain. In contrast, treatment with ACE at both doses remarkably altered the neurochemical parameters. In addition, ACE-treated mice showed a substantial reduction in acetylcholinesterase, D-amino acid oxidase enzyme activity, and nitrite levels which were elevated by the administration of MK-801.

CONCLUSIONS

Treatment with ACE once for 14 days (1 and 2 g/kg) significantly ameliorated the behavioral symptoms in experimentally induced psychosis by virtue of neuromodulation and decreased oxidative stress.

Characterizing amino-acid biosignatures amongst individuals with schizophrenia: a case-control study

Amino acids and derivatives participate in the biosynthesis and downstream effects of numerous neurotransmitters. Variations in specific amino acids have been implicated in the pathophysiology of schizophrenia. Herein, we sought to compare levels of amino acids and derivatives between subjects with schizophrenia and healthy controls (HC). Two hundred and eight subjects with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria (DSM-IV)-defined schizophrenia and 175 age- and sex-matched HC were enrolled. The levels of twenty-five amino acids and seven related derivatives were measured in plasma samples using hydrophilic interaction liquid chromatography (HILIC) liquid chromatography-tandem mass spectrometry (LC-MS). After controlling for age, sex and body mass index (BMI), four amino acids and derivatives (i.e., cysteine, GABA, glutamine and sarcosine) were observed to be higher in the schizophrenia group when compared with HC; seven amino acids and derivatives were lower in the schizophrenia group (i.e., arginine, L-ornithine, threonine, taurine, tryptophan, methylcysteine, and kynurenine). Statistically significant differences in plasma amino-acid profiles between subjects with first-episode vs. recurrent schizophrenia for aspartate and glutamine were also demonstrated using generalized linear models controlling for age, sex, and BMI. The differences in amino acids and derivatives among individuals with schizophrenia when compared to HC may represent underlying pathophysiology, including but not limited to dysfunctional proteinogenic processes, alterations in excitatory and inhibitory neurotransmission, changes in ammonia metabolism and the urea cycle. Taken together, amino-acid profiling may provide a novel stratification approach among individuals with schizophrenia.

Enhanced uptake of BPA in the presence of nanoplastics can lead to neurotoxic effects in adult zebrafish

Plastic particles have been proven to be abundant in the aquatic environment, raising concerns about their potential toxic effects. In the present study, we determined the bioaccumulation potential of bisphenol A (BPA) in adult zebrafish (Danio rerio) in the absence and presence of nano-sized plastic particles (nanoplastics, NPPs). Results show that BPA can accumulate in the viscera, gill, head and muscle of zebrafish with 85, 43, 20, and 3μg/g ww after 1d exposure. NPPs were also found to accumulate in different tissues of the fish. Relative equilibrium was reached after 1d exposure in different tissues with 39 to 636mg/kg ww. Co-exposure of NPPs and BPA led to a 2.2 and 2.6-fold significant increment of BPA uptake in the head and viscera, if compared with BPA alone treatment after 3d exposure. As such, we further investigated several neurotoxic biomarker alterations in the fish head. It was found that either BPA or NPPs can cause myelin basic protein (MBP)/gene up-regulation in the central nervous system (CNS); meanwhile, both contaminants exhibited significant inhibition of acetylcholinesterase (AChE) activity, which is a well-known representative biomarker for neurotoxicity. Moreover, for the co-exposure treatment, biomarkers of myeline and tubulin protein/gene expressions, dopamine content, and the mRNA expression of mesencephalic astrocyte derived neurotrophic factor (MANF) were all significantly up-regulated, suggesting that an enhanced neurotoxic effects in both CNS and dopaminergic system occurred. However, AChE activity was no more inhibited in the co-exposure treatment, which implies that solely AChE measurement may not be sufficient to identify neurotoxic effects in the cholinergic system. Overall, the present study demonstrates that the presence of NPPs can increase BPA bioavailability and cause neurotoxicity in adult zebrafish.

No association between SLC6A2, SLC6A3, DRD2 polymorphisms and schizophrenia in the Han Chinese population

This study was intended to ascertain whether SNPs in dopaminergic and serotoninergic pathway genes SLC6A2, SLC6A3 and DRD2 are associated with schizophrenia in Han Chinese people. We conducted a case-control study by genotyping 7 SNPs of the three genes in 1034 schizophrenia patients and 1034 controls. No significant difference in the allelic or genotypic frequency was detected between cases and controls despite one positive haplotype (rs1362621-rs2242446-rs5564). Stratified analysis of gender and gene-gene interaction analysis showed no positive results. In summary, our study denies the major role of these SNPs within the three genes for schizophrenia in Han Chinese.

The Impact of Maternal Vitamin D Status on Offspring Brain Development and Function: a Systematic Review

Various studies have examined associations between maternal vitamin D (VD) deficiency and offspring health, including offspring brain health. The purpose of this review was to summarize current evidence concerning the impact of maternal VD deficiency on brain development and function in offspring. A systematic search was conducted within Medline (on Ovid) for studies published through 7 May 2015. Animal and human studies that examined associations between maternal VD status or developmental VD deficiency and offspring brain development and function were included. A total of 26 animal studies and 10 human studies met the inclusion criteria. Several animal studies confirmed the hypothesis that low prenatal VD status may affect brain morphology and physiology as well as behavioral outcomes. In humans, subtle cognitive and psychological impairments in offspring of VD-deficient mothers were observed. However, data obtained from animal and human studies provide inconclusive evidence, and results seem to depend on strain or race and age of offspring. To conclude, prenatal VD status is thought to play an important role in brain development, cognitive function, and psychological function. However, results are inconclusive; validation of these findings and investigation of underlying mechanisms are required. Thus, more investigation is needed before recommending supplementation of VD during pregnancy to promote brain health of offspring.

Attitudes towards cannabis use and genetic testing for schizophrenia

AIM

Within schizophrenia, genetic factors contribute greatly to risk, yet genetic testing for the disorder is not available. For some individuals with specific genotypes, cannabis use may increase risk of schizophrenia. It is possible that genetic tests could be offered in the future to inform individuals of the risk of schizophrenia if they use cannabis. Previous research, however, provides little guidance on how young adults might respond to such tests.

METHODS

We assessed a group of young adults (n = 83) to determine how the perceived magnitude of increased risk for schizophrenia in the presence of cannabis use influences decisions to undergo genetic testing, as well as subsequent attitudes and intentions towards cannabis use.

RESULTS

Participants were significantly more likely to indicate willingness to get tested if the results identified a 10% risk versus a 2% risk of schizophrenia. Participants also indicated that if the results of their test reflected increased risk due to cannabis use, it would be more important to avoid cannabis in the 10% risk scenario as compared to the 2% risk scenario. These findings remained consistent among a subset of participants who indicated cannabis use.

CONCLUSIONS

Results suggest that cannabis users and non-users were positively influenced in terms of intentions to change behaviour based on the magnitude of risk conveyed by genetic testing. These findings provide an initial step towards understanding young people's attitudes towards genetic testing and may help prepare interventions specifically tailored around cannabis use reduction for people at risk for schizophrenia.

Supplementation of Antipsychotic Treatment with the Amino Acid Sarcosine Influences Proton Magnetic Resonance Spectroscopy Parameters in Left Frontal White Matter in Patients with Schizophrenia

Dysfunction of the glutamatergic system, the main stimulating system in the brain, has a major role in pathogenesis of schizophrenia. The frontal white matter (WM) is partially composed of axons from glutamatergic pyramidal neurons and glia with glutamatergic receptors. The natural amino acid sarcosine, a component of a normal diet, inhibits the glycine type 1 transporter, increasing the glycine level. Thus, it modulates glutamatergic transmission through the glutamatergic ionotropic NMDA (N-methyl-d-aspartate) receptor, which requires glycine as a co-agonist. To evaluate the concentrations of brain metabolites (NAA, N-acetylaspartate; Glx, complex of glutamate, glutamine, and γ-aminobutyric acid (GABA); mI, myo-inositol; Cr, creatine; Cho, choline) in the left frontal WM, Proton Nuclear Magnetic Resonance (¹H-NMR) spectroscopy was used. Twenty-five patients randomly chosen from a group of fifty with stable schizophrenia (DSM-IV-TR) and dominant negative symptoms, who were receiving antipsychotic therapy, were administered 2 g of sarcosine daily for six months. The remaining 25 patients received placebo. Assignment was double blinded. ¹H-NMR spectroscopy (1.5 T) was performed twice: before and after the intervention. NAA, Glx and mI were evaluated as Cr and Cho ratios. All patients were also assessed twice with the Positive and Negative Syndrome Scale (PANSS). Results were compared between groups and in two time points in each group. The sarcosine group demonstrated a significant decrease in WM Glx/Cr and Glx/Cho ratios compared to controls after six months of therapy. In the experimental group, the final NAA/Cr ratio significantly increased and Glx/Cr ratio significantly decreased compared to baseline values. Improvement in the PANSS scores was significant only in the sarcosine group. In patients with schizophrenia, sarcosine augmentation can reverse the negative effect of glutamatergic system overstimulation, with a simultaneous beneficial increase of NAA/Cr ratio in the WM of the left frontal lobe. Our results further support the glutamatergic hypothesis of schizophrenia.

Rejection attitudes, poor parental bonding, and stressful life events in heroin addicts' families

BACKGROUND

The influence of family factors on the development and/or on maintenance of heroin addiction still remains unclear.

OBJECTIVES

The aim of this study was to investigate family factors, which might be associated with heroin addiction in a sample of male individuals.

METHODS

A group of 40 heroin addicts' families was compared with a group of 17 families with a member presenting schizophrenia and a group of 27 families with mentally healthy members in regard to (1) parents' rejection attitudes toward their adult child, (2) quality of parental bond, as perceived by the adult child, and (3) stressful life events in the nuclear family.

RESULTS

The main findings showed that the degree of rejection by the fathers in the heroin addicts' families as well as in the subjects with schizophrenia was significantly higher compared to the fathers' degree of rejection in the control group. Moreover, the degree of rejection by mothers in the heroin addicts' families was significantly higher compared to the mothers' degree of rejection in the control group. Heroin addicts reported that they had perceived less care from their fathers than healthy controls. The total number of stressful life events in the nuclear family was higher in the patients with schizophrenia in comparison to the healthy controls. Also, in the heroin addicts' group, a significantly higher number of fathers presented a current or past psychiatric disorder.

CONCLUSIONS

The findings of this study showed the importance of negative family factors in the course of heroin addiction.

Adolescent self-control predicts midlife hallucinatory experiences: 40-year follow-up of a national birth cohort

BACKGROUND

Associations between self-control in adolescence and adult mental health are unclear in the general population; to our knowledge, no study has investigated self-control in relation to psychotic-like symptoms.

AIMS

To investigate the relationship between adolescent self-control and the midlife mental health outcomes of anxiety and depression symptoms and psychotic-like experiences (PLEs), controlling for the effect of adolescent conduct and emotional problems and for parental occupational social class and childhood cognition.

METHODS

A population-based sample, the MRC National Survey of Health and Development (the British 1946 birth cohort) was contacted 23 times between ages 6 weeks and 53 years. Teachers completed rating scales to assess emotional adjustment and behaviors, from which factors measuring self-control, behavioral, and emotional problems were extracted. At age 53 years, PLEs were self-reported by 2918 participants using 4 items from the Psychosis Screening Questionnaire; symptoms of anxiety and depression were assessed using the scaled version of the General Health Questionnaire (GHQ-28).

RESULTS

After adjustment for the above covariates, poor adolescent self-control was associated with the presence of PLEs in adulthood, specifically hallucinatory experiences at age 53 years, even after adjustment for GHQ-28 scores.

CONCLUSIONS

Lower self-control in adolescence is a risk factor for hallucinatory experiences in adulthood.

Does treatment of schizophrenia with antipsychotic medications eliminate or reduce psychosis? A 20-year multi-follow-up study

BACKGROUND

This research assesses whether multi-year treatment with antipsychotic medications reduces or eliminates psychosis in schizophrenia. It provides 20 years of longitudinal data on the frequency and severity of psychotic activity in samples of schizophrenia patients (SZ) treated versus those not treated with antipsychotic medications.

METHOD

A total of 139 early young schizophrenia and mood-disordered patients were assessed at index hospitalization and then reassessed six times over 20 years for psychosis and other major variables.

RESULTS

At each follow-up assessment over the 20 years, a surprisingly high percentage of SZ treated with antipsychotics longitudinally had psychotic activity. More than 70% of SZ continuously prescribed antipsychotics experienced psychotic activity at four or more of six follow-up assessments over 20 years. Longitudinally, SZ not prescribed antipsychotics showed significantly less psychotic activity than those prescribed antipsychotics (p < 0.05).

CONCLUSIONS

The 20-year data indicate that, longitudinally, after the first few years, antipsychotic medications do not eliminate or reduce the frequency of psychosis in schizophrenia, or reduce the severity of post-acute psychosis, although it is difficult to reach unambiguous conclusions about the efficacy of treatment in purely naturalistic or observational research. Longitudinally, on the basis of their psychotic activity and the disruption of functioning, the condition of the majority of SZ prescribed antipsychotics for multiple years would raise questions as to how many of them are truly in remission.

The relationship between DRD2 gene polymorphisms (C957T and C939T) and schizophrenia: a meta-analysis

Schizophrenia is a common, complex multi-factorial psychiatric disorder. Many studies have reported associations between the C957T and C939T polymorphisms in Dopamine D2 receptor (DRD2) gene and schizophrenia, but results are inconsistent. To derive a more precise estimation of the relationship, a meta-analysis was conducted to systematically summarize the possibility. We included 13 articles involving 3079 schizophrenia cases and 3851 healthy controls. Positive associations were found between C957T polymorphism and schizophrenia risk in C vs. T (OR=1.26, 95% CI=1.09-1.46, Praw=0.002, PFDR=0.005) and CC+CT vs. TT (OR=1.47, 95% CI=1.25-1.73, Praw<0.001, PFDR<0.001). When stratified by race, a significantly increased risk of schizophrenia was observed in Caucasians, but not in Asians. No association between C939T polymorphism and schizophrenia was found in overall or Asian population. Our study suggested that C957T of DRD2 gene polymorphism is likely to be a risk factor for schizophrenia, especially in Caucasian.

Prediction of brain clozapine and norclozapine concentrations in humans from a scaled pharmacokinetic model for rat brain and plasma pharmacokinetics

BACKGROUND

Clozapine is highly effective in treatment-resistant schizophrenia, although, there remains significant variability in the response to this drug. To better understand this variability, the objective of this study was to predict brain extracellular fluid (ECF) concentrations and receptor occupancy of clozapine and norclozapine in human central nervous system by translating plasma and brain ECF pharmacokinetic (PK) relationships in the rat and coupling these with known human disposition of clozapine in the plasma.

METHODS

Unbound concentrations of clozapine and norclozapine were measured in rat brain ECF using quantitative microdialysis after subcutaneous administration of a 10 mg/kg single dose of clozapine or norclozapine. These data were linked with plasma concentrations obtained in the same rats to develop a plasma-brain ECF compartmental model. Parameters describing brain ECF disposition were then allometrically scaled and linked with published human plasma PK to predict human ECF concentrations. Subsequently, prediction of human receptor occupancy at several CNS receptors was based on an effect model that related the predicted ECF concentrations to published concentration-driven receptor occupancy parameters.

RESULTS

A one compartment model with first order absorption and elimination best described clozapine and norclozapine plasma concentrations in rats. A delay in the transfer of clozapine and norclozapine from plasma to the brain ECF compartment was captured using a transit compartment model approach. Human clozapine and norclozapine concentrations in brain ECF were simulated, and from these the median percentage of receptor occupancy of dopamine-2, serotonin-2A, muscarinic-1, alpha-1 adrenergic, alpha-2 adrenergic and histamine-1 for clozapine, and dopamine-2 for norclozapine were consistent with values reported in the literature.

CONCLUSIONS

A PK model that relates clozapine and norclozapine disposition in rat plasma and brain, including blood-brain barrier transport, was developed. Using allometry and published human plasma PK, the model was successfully translated to predict clozapine and norclozapine concentrations and accordant receptor occupancy of both agents in human brain. These predicted exposure and occupancy measures at several receptors that bind clozapine may be employed to extend our understanding of clozapine's complex behavioral effects in humans.

Genetic dissection of the psychotomimetic effects of cannabinoid exposure

Cannabis use is an established risk factor for the development of schizophrenia and related psychotic disorders. Factors that may mediate susceptibility to the psychosis-inducing effects of cannabis include the age at onset of first cannabis use, genetic predisposition, as well as interaction with other environmental risk variables. Clinical and preclinical genetic studies provide increasing evidence that, in particular, genes encoding proteins implicated in dopamine signalling are implicated in the cannabis-psychosis association. In the present review, we focus on both human and animal studies which have focused on identifying the neuronal basis of these interactions. We conclude that further studies are required to provide greater mechanistic insight into the long-term and neurodevelopmental effects of cannabis use, with implications for improved understanding of the cannabis-psychosis relationship.

Different rates of first admissions for psychosis in migrant groups in Paris

PURPOSE

The association between migration and psychosis has been reported in the past decades in many European countries. Despite large-scale migration into France, epidemiological data on the incidence of psychosis in this population are lacking. In this study, we compare the incidence rates of first admission for psychosis among natives and first generation migrants.

METHODS

Two-hundred and fifty-eight patients aged 15+ with first admission for psychosis were identified in the catchment area of the 20th district of Paris between 2005 and 2009. Standardised incidence rates and incidence rate ratios were calculated for migrant and native groups.

RESULTS

We found higher rates of admissions for psychosis in the migrant group (IRR 2.9, 95 % CI 0.9-9.8) compared to individuals born in France. Among migrants, incidence was higher in individuals from Sub-Saharan Africa compared to natives (IRR 7.1, CI 95 % 2.3-21.8), whereas the incidence was similar for those from Europe (IRR 1.2, CI 95 % 0.3-5.1) and from North Africa (IRR 1.4, CI 95 % 0.4-5.6).

CONCLUSIONS

Our findings suggest that Sub-Saharan migrants were identified as the most vulnerable migrant group for developing psychosis in France, but additional work is warranted to confirm these trends.

Schizophrenia: an integrated sociodevelopmental-cognitive model

Schizophrenia remains a major burden on patients and society. The dopamine hypothesis attempts to explain the pathogenic mechanisms of the disorder, and the neurodevelopmental hypothesis the origins. In the past 10 years an alternative, the cognitive model, has gained popularity. However, the first two theories have not been satisfactorily integrated, and the most influential iteration of the cognitive model makes no mention of dopamine, neurodevelopment, or indeed the brain. In this Review we show that developmental alterations secondary to variant genes, early hazards to the brain, and childhood adversity sensitise the dopamine system, and result in excessive presynaptic dopamine synthesis and release. Social adversity biases the cognitive schema that the individual uses to interpret experiences towards paranoid interpretations. Subsequent stress results in dysregulated dopamine release, causing the misattribution of salience to stimuli, which are then misinterpreted by the biased cognitive processes. The resulting paranoia and hallucinations in turn cause further stress, and eventually repeated dopamine dysregulation hardwires the psychotic beliefs. Finally, we consider the implications of this model for understanding and treatment of schizophrenia.

The amphetamine sensitization model of schizophrenia symptoms and its effect on schedule-induced polydipsia in the rat

RATIONALE

Amphetamine enhances dopamine (DA) transmission and induces psychotic states or exacerbates psychosis in at-risk individuals. Amphetamine sensitization of the DA system has been proposed as a rodent model of schizophrenia-like symptoms. In humans, excessive nonphysiologic drinking or primary polydipsia is significantly associated with a diagnosis of schizophrenia. In rodents, nonphysiologic drinking can be induced by intermittent presentation of food in the presence of a drinking spout to a hungry animal; this phenomenon is termed, "schedule-induced polydipsia" (SIP).

OBJECTIVE

This study aims to determine the effects of amphetamine sensitization on SIP.

METHODS

We injected rats with amphetamine (1.5 mg/kg) daily for 5 days. Following 4 weeks of withdrawal, animals were food restricted and exposed to the SIP protocol (noncontingent fixed-time 1-min food schedule) for daily 2-h sessions for 24 days.

RESULTS

Results showed that previously amphetamine-injected animals drank more in the SIP protocol and drank more than controls when the intermittent food presentation schedule was removed.

CONCLUSIONS

These findings suggest that hyperdopaminergia associated with schizophrenia may contribute to the development of polydipsia in this population. Whether animals that develop SIP have DA dysfunction or aberrant activity of other circuits that modulate DA activity has yet to be clearly defined.

Evaluating negative-symptom-like behavioural changes in developmental models of schizophrenia

Many lines of evidence suggest that schizophrenia has a major developmental component and that environmental factors that disrupt key stages of development, such as maternal stress during pregnancy as a result of infection or malnutrition, can increase the risk of developing schizophrenia in later life. This review examines how non-clinical neurodevelopmental models pertinent to schizophrenia have been evaluated for their ability to reproduce behavioural deficits related to the negative symptoms of schizophrenia. The more frequently used are the prenatal application of the mitotoxic agent methylazoxymethanol, prenatal immune challenge and the neonatal ventral hippocampus lesion model. In general they have been extensively evaluated in models considered relevant to positive symptoms of schizophrenia. In contrast, very few studies have examined tests related to negative symptoms and, when they have, it has almost exclusively been a social interaction model. Other aspects related to negative symptoms such as anhedonia, affective flattening and avolition have almost never been studied. Further studies examining other components of negative symptomatology are needed to more clearly associate these deficits with a schizophrenia-like profile as social withdrawal is a hallmark of many disorders. Although there are no truly effective treatments for negative symptoms, better characterisation with a broader range of drugs used in schizophrenia will be necessary to better evaluate the utility of these models. In summary, developmental models of schizophrenia have been extensively studied as models of positive symptoms but, given the unmet need in the clinic, the same effort now needs to be made with regard to negative symptoms.

Consequences at adulthood of transient inactivation of the parahippocampal and prefrontal regions during early development: new insights from a disconnection animal model for schizophrenia

The psychic disintegration characteristic of schizophrenia is thought to result from a defective connectivity, of neurodevelopmental origin, between several integrative brain regions. The parahippocampal region and the prefrontal cortex are described as the main regions affected in schizophrenia. Interestingly, latent inhibition (LI) has been found to be reduced in patients with schizophrenia, and the existence of a dopaminergic dysfunction is also generally well accepted in this disorder. In the present review, we have integrated behavioral and neurochemical data obtained in a LI protocol involving adult rats subjected to neonatal functional inactivation of the entorhinal cortex, the ventral subiculum or the prefrontal cortex. The data discussed suggest a subtle and transient functional blockade during early development of the aforementioned brain regions is sufficient to induce schizophrenia-related behavioral and dopaminergic abnormalities in adulthood. In summary, these results support the view that our conceptual and methodological approach, based on functional disconnections, is valid for modeling some aspects of the pathophysiology of schizophrenia from a neurodevelopmental perspective.

What's intact and what's not within the mismatch negativity system in schizophrenia

Repetitive patterning facilitates inferences about likely properties of sound to follow. Mismatch negativity (MMN) occurs when sound fails to match an inference. Smaller MMN in schizophrenia indexes deficient gain control (difference in utilizing a limited dynamic range). Although it is clear that this group has a lower limit to MMN size, this study addressed whether smaller MMN indicates impaired perceptual inference. MMN was elicited to four deviants in two sequences: one in which occurrence was random and one in which it was paired. Despite smaller MMN, persons with schizophrenia are equally able to reduce MMN size evoked by a deviant when its occurrence is cued. Results also expose alterations in the evoked response to repeated sounds that appear to be exacerbations of age-related amplitude decline. Since these anomalies impact the computed MMN, they highlight the need to identify all contributions to limits in gain control in schizophrenia.

Genetics, cognition, and neurobiology of schizotypal personality: a review of the overlap with schizophrenia

Schizotypy refers to a set of temporally stable traits that are observed in the general population and that resemble the signs and symptoms of schizophrenia. Here, we review evidence from studies on genetics, cognition, perception, motor and oculomotor control, brain structure, brain function, and psychopharmacology in schizotypy. We specifically focused on identifying areas of overlap between schizotypy and schizophrenia. Evidence was corroborated that significant overlap exists between the two, covering the behavioral brain structural and functional as well molecular levels. In particular, several studies showed that individuals with high levels of schizotypal traits exhibit alterations in neurocognitive task performance and underlying brain function similar to the deficits seen in patients with schizophrenia. Studies of brain structure have shown both volume reductions and increase in schizotypy, pointing to schizophrenia-like deficits as well as possible protective or compensatory mechanisms. Experimental pharmacological studies have shown that high levels of schizotypy are associated with (i) enhanced dopaminergic response in striatum following administration of amphetamine and (ii) improvement of cognitive performance following administration of antipsychotic compounds. Together, this body of work suggests that schizotypy shows overlap with schizophrenia across multiple behavioral and neurobiological domains, suggesting that the study of schizotypal traits may be useful in improving our understanding of the etiology of schizophrenia.

Roundabout receptors

Roundabout receptors (Robo) and their Slit ligands were discovered in the 1990s and found to be key players in axon guidance. Slit was initially described s an extracellular matrix protein that was expressed by midline glia in Drosophila. A few years later, it was shown that, in vertebrates and invertebrates, Slits acted as chemorepellents for axons crossing the midline. Robo proteins were originally discovered in Drosophila in a mutant screen for genes involved in the regulation of midline crossing. This ligand-receptor pair has since been implicated in a variety of other neuronal and non-neuronal processes ranging from cell migration to angiogenesis, tumourigenesis and even organogenesis of tissues such as kidneys, lungs and breasts.

The brain effects of cannabis in healthy adolescents and in adolescents with schizophrenia: a systematic review

Cannabis is widely used in adolescence; however, the effects of cannabis on the developing brain remain unclear. Cannabis might be expected to have increased effects upon brain development and cognition during adolescence. There is extensive re-organisation of grey (GM) and white matter (WM) at this time, while the endocannabinoid (eCB) system, which is involved in the normal physiological regulation of neural transmission, is still developing. In healthy adolescent cannabis users there is a suggestion of greater memory loss and hippocampal volume changes. Functional studies point to recruitment of greater brain areas under cognitive load. Structural and DTI studies are few, and limited by comorbid drug and alcohol use. The studies of cannabis use in adolescent-onset schizophrenia (AOS) differ, with one study pointing to extensive GM and WM changes. There is an intriguing suggestion that the left parietal lobe may be more vulnerable to the effects of cannabis in AOS. As in adult schizophrenia cognition does not appear to be adversely affected in AOS following cannabis use. Given the limited number of studies it is not possible to draw firm conclusions. There is a need for adequately powered, longitudinal studies.

Mismatch negativity: translating the potential

The mismatch negativity (MMN) component of the auditory event-related potential has become a valuable tool in cognitive neuroscience. Its reduced size in persons with schizophrenia is of unknown origin but theories proposed include links to problems in experience-dependent plasticity reliant on N-methyl-d-aspartate glutamate receptors. In this review we address the utility of this tool in revealing the nature and time course of problems in perceptual inference in this illness together with its potential for use in translational research testing animal models of schizophrenia-related phenotypes. Specifically, we review the reasons for interest in MMN in schizophrenia, issues pertaining to the measurement of MMN, its use as a vulnerability index for the development of schizophrenia, the pharmacological sensitivity of MMN and the progress in developing animal models of MMN. Within this process we highlight the challenges posed by knowledge gaps pertaining to the tool and the pharmacology of the underlying system.

What can we learn about schizophrenia from studying the human model, drug-induced psychosis?

When drug-induced psychoses were first identified in the mid-20th century, schizophrenia was considered a discrete disease with a likely genetic cause. Consequently, drug-induced psychoses were not considered central to understanding schizophrenia as they were thought to be phenocopies rather than examples of the illness secondary to a particular known cause. However, now that we know that schizophrenia is a clinical syndrome with multiple component causes, then it is clear that the drug-induced psychoses have much to teach us. This article shows how the major neuropharmacological theories of schizophrenia have their origins in studies of the effects of drugs of abuse. Research into the effects of LSD initiated the serotonergic model; amphetamines the dopamine hypothesis, PCP and ketamine the glutamatergic hypothesis, while most recently the effects of cannabis have provoked interest in the role of endocannabinoids in schizophrenia. None of these models account for the complete picture of schizophrenia; rather the various drug models mimic different aspects of the illness. Determining the different molecular effects of those drugs whose pharmacological effects do and do not mimic the various aspects of schizophrenia has much to teach us concerning the pathogenesis of the illness.

Memory reconsolidation in aversive and appetitive settings

Memory reconsolidation has been observed across species and in a number of behavioral paradigms. The majority of memory reconsolidation studies have been carried out in Pavlovian fear conditioning and other aversive memory settings, with potential implications for the treatment of post-traumatic stress disorder. However, there is a growing literature on memory reconsolidation in appetitive reward-related memory paradigms, including translational models of drug addiction. While there appears to be substantial similarity in the basic phenomenon and underlying mechanisms of memory reconsolidation across unconditioned stimulus valence, there are also notable discrepancies. These arise both when comparing aversive to appetitive paradigms and also across different paradigms within the same valence of memory. We review the demonstration of memory reconsolidation across different aversive and appetitive memory paradigms, the commonalities and differences in underlying mechanisms and the conditions under which each memory undergoes reconsolidation. We focus particularly on whether principles derived from the aversive literature are applicable to appetitive settings, and also whether the expanding literature in appetitive paradigms is informative for fear memory reconsolidation.

Altered dopamine ontogeny in the developmentally vitamin D deficient rat and its relevance to schizophrenia

Schizophrenia is a heterogeneous group of disorders with unknown etiology. Although abnormalities in multiple neurotransmitter systems have been linked to schizophrenia, alterations in dopamine (DA) neurotransmission remain central to the treatment of this disorder. Given that schizophrenia is considered a neurodevelopmental disorder we have hypothesized that abnormal DA signaling in the adult patient may result from altered DA signaling during fetal brain development. Environmental and genetic risk factors can be modeled in rodents to allow for the investigation of early neurodevelopmental pathogenesis that may lead to clues into the etiology of schizophrenia. To address this we created an animal model of one such risk factor, developmental vitamin D (DVD) deficiency. DVD-deficient adult rats display an altered behavioral profile in response to DA releasing and blocking agents that are reminiscent of that seen in schizophrenia patients. Furthermore, developmental studies revealed that DVD deficiency also altered cell proliferation, apoptosis, and neurotransmission across the embryonic brain. In particular, DVD deficiency reduces the expression of crucial dopaminergic specification factors and alters DA metabolism in the developing brain. We speculate such alterations in fetal brain development may change the trajectory of DA neuron ontogeny to induce the behavioral abnormalities observed in adult offspring. The widespread evidence that both dopaminergic and structural changes are present in people who develop schizophrenia prior to onset also suggest that early alterations in development are central to the disease. Taken together, early alterations in DA ontogeny may represent a core feature in the pathology of schizophrenia. Such a mechanism could bring together evidence from multiple risk factors and genetic vulnerabilities to form a convergent pathway in disease pathophysiology.

Functional −141C Ins/Del polymorphism in the dopamine D2 receptor gene promoter and schizophrenia in a Chinese Han population

Objective

The association between a putative functional promoter polymorphism, −141C insertion/deletion (Ins/Del), in the dopamine receptor D2 gene ( DRD2) and schizophrenia was investigated in a Chinese Han population.

Methods

The polymorphism was studied in unrelated schizophrenia patients and unrelated healthy controls. Linkage relationships were explored in core families of the schizophrenic patients using the transmission disequilibrium test. The Positive and Negative Syndrome Scale was used to evaluate the severity of the disorder.

Results

The Del allele was significantly less frequently found in patients (13/120; 11%) than in controls (18/100; 18%). In the 32 core families studied, 16 parents were Ins/Del heterozygotes. Parents transmitted the Ins and Del alleles to their children in 10 and six cases, respectively. Data from core families did not demonstrate linkage. Age, age at onset of schizophrenia and sex were not significantly different between carriers of the Ins and Del alleles. The group with the Ins allele had a significantly higher positive symptom score (75.3 ± 23.4 versus 53.9 ± 21.9) and excitement score (83.6 ± 16.8 versus 50.3 ± 24.6) than the Del group. Groups did not differ significantly in negative symptom and general psychopathology scores.

Conclusions

The DRD2 −141C Ins/Del polymorphism may affect susceptibility to schizophrenia in a Chinese Han population.

BDNF and schizophrenia: from neurodevelopment to neuronal plasticity, learning, and memory

Brain-Derived Neurotrophic Factor (BDNF) is a neurotrophin that has been related not only to neurodevelopment and neuroprotection, but also to synapse regulation, learning, and memory. Research focused on the neurobiology of schizophrenia has emphasized the relevance of neurodevelopmental and neurotoxicity-related elements in the pathogenesis of this disease. Research focused on the clinical features of schizophrenia in the past decades has emphasized the relevance of cognitive deficits of this illness, considered a core manifestation and an important predictor for functional outcome. Variations in neurotrophins such as BDNF may have a role as part of the molecular mechanisms underlying these processes, from the neurodevelopmental alterations to the molecular mechanisms of cognitive dysfunction in schizophrenia patients.