Neurobiological basis of relapse prediction in stimulant-induced psychosis and schizophrenia: the role of sensitization

The Natural Protoalkaloid Methyl-2-Amino-3-Methoxybenzoate (MAM) Alleviates Positive as well as Cognitive Symptoms in Rat and Mouse Schizophrenia Models

The development of new antipsychotics with pro-cognitive properties and less side effects represents a priority in schizophrenia drug research. In this study, we present for the first time a preclinical exploration of the effects of the promising natural atypical antipsychotic Methyl-2-Amino-3- Methoxybenzoate (MAM), a brain-penetrable protoalkaloid from the seed of the plant Nigella damascena. Using animal models related to hyperdopaminergic activity, namely the pharmacogenetic apomorphine (D2/D1 receptor agonist)-susceptible (APO-SUS) rat model and pharmacologically induced mouse and rat models of schizophrenia, we found that MAM reduced gnawing stereotypy and climbing behaviours induced by dopaminergic agents. This predicts antipsychotic activity. In line, MAM antagonized apomorphine-induced c-Fos and NPAS4 mRNA levels in post-mortem brain nucleus accumbens and dorsolateral striatum of APO-SUS rats. Furthermore, phencyclidine (PCP, an NMDA receptor antagonist) and 2,5-Dimethoxy-4-iodoamphetamine (DOI, a 5HT2A/2C receptor agonist) induced prepulse inhibition deficits, reflecting the positive symptoms of schizophrenia, which were rescued by treatment with MAM and atypical antipsychotics alike. Post-mortem brain immunostaining revealed that MAM blocked the strong activation of both PCP- and DOI-induced c-Fos immunoreactivity in a number of cortical areas. Finally, during a 28-day subchronic treatment regime, MAM did not induce weight gain, hyperglycemia, hyperlipidemia or hepato- and nephrotoxic effects, side effects known to be induced by atypical antipsychotics. MAM also did not show any cataleptic effects. In conclusion, its brain penetrability, the apparent absence of preclinical side effects, and its ability to antagonize positive and cognitive symptoms associated with schizophrenia make MAM an exciting new antipsychotic drug that deserves clinical testing.

Occurrence and severity of cocaine-induced hallucinations: Two distinct phenotypes with shared clinical factors but specific genetic risk factors

Cocaine-induced transient hallucinations (CIH) are a frequent complication following cocaine intake that is associated with addiction severity.

METHODS

Two hundred and forty-two non-psychotic and Caucasian lifetime cocaine users were included in a French multicentric study. Clinical variables and dopamine pathway genotype data were extracted and tested with CIH scores using a zero-inflated binomial model, which allows for the exploration of factors associated with occurrence and severity separately.

RESULTS

Cocaine dependence (p_occurrence= 6.18 × 10^-5, p_severity= 9.25 × 10^-8), number of cocaine dependence DSM IV-Tr criteria (p_occurrence= 1.22 × 10^-7, p_severity= 5.09 × 10^-6), and frequency of intake during the worst period of misuse (p_occurrence= 8.51 × 10^-04, p_severity= 0.04) were associated with greater occurrence and higher severity of CIH. The genetic associations did not yield significant results after correction for multiple tests. However, some nominal associations of SNPs mapped to the VMAT2, DBH, DRD1, and DRD2 genes were significant. In the multivariate model, the significant variables were the number of cocaine dependence criteria, lifetime alcohol dependence, and the nominally associated SNPs.

CONCLUSION

Our study shows that CIH occurrence and severity are two distinct phenotypes, with shared clinical risk factors; however, they likely do not share the same genetic background.

Haloperidol rescues the schizophrenia-like phenotype in adulthood after rotenone administration in neonatal rats

Neuropsychiatric disorders are multifactorial disturbances that encompass several hypotheses, including changes in neurodevelopment. It is known that brain development disturbances during early life can predict psychosis in adulthood. As we have previously demonstrated, rotenone, a mitochondrial complex I inhibitor, could induce psychiatric-like behavior in 60-day-old rats after intraperitoneal injections from the 5th to the 11th postnatal day. Because mitochondrial deregulation is related to psychiatric disorders and the establishment of animal models is a high-value preclinical tool, we investigated the responsiveness of the rotenone (Rot)-treated newborn rats to pharmacological agents used in clinical practice, haloperidol (Hal), and methylphenidate (MPD). Taken together, our data show that Rot-treated animals exhibit hyperlocomotion, decreased social interaction, and diminished contextual fear conditioning response at P60, consistent with positive, negative, and cognitive deficits of schizophrenia (SZ), respectively, that were reverted by Hal, but not MPD. Rot-treated rodents also display a prodromal-related phenotype at P35. Overall, our results seem to present a new SZ animal model as a consequence of mitochondrial inhibition during a critical neurodevelopmental period. Therefore, our study is crucial not only to elucidate the relevance of mitochondrial function in the etiology of SZ but also to fulfill the need for new and trustworthy experimentation models and, likewise, provide possibilities to new therapeutic avenues for this burdensome disorder.

Hippocampal Hyperactivity as a Druggable Circuit-Level Origin of Aberrant Salience in Schizophrenia

The development of current neuroleptics was largely aiming to decrease excessive dopaminergic signaling in the striatum. However, the notion that abnormal dopamine creates psychotic symptoms by causing an aberrant assignment of salience that drives maladaptive learning chronically during disease development suggests a therapeutic value of early interventions that correct salience-related neural processing. The mesolimbic dopaminergic output is modulated by several interconnected brain-wide circuits centrally involving the hippocampus and key relays like the ventral and associative striatum, ventral pallidum, amygdala, bed nucleus of the stria terminalis, nucleus reuniens, lateral and medial septum, prefrontal and cingulate cortex, among others. Unraveling the causal relationships between these circuits using modern neuroscience techniques holds promise for identifying novel cellular-and ultimately molecular-treatment targets for reducing transition to psychosis and symptoms of schizophrenia. Imaging studies in humans have implicated a hyperactivity of the hippocampus as a robust and early endophenotype in schizophrenia. Experiments in rodents, in turn, suggested that the activity of its output region-the ventral subiculum-may modulate dopamine release from ventral tegmental area (VTA) neurons in the ventral striatum. Even though these observations suggested a novel circuit-level target for anti-psychotic action, no therapy has yet been developed along this rationale. Recently evaluated treatment strategies-at least in part-target excess glutamatergic activity, e.g. N-acetyl-cysteine (NAC), levetiracetam, and mGluR2/3 modulators. We here review the evidence for the central implication of the hippocampus-VTA axis in schizophrenia-related pathology, discuss its symptom-related implications with a particular focus on aberrant assignment of salience, and evaluate some of its short-comings and prospects for drug discovery.

Far-infrared Ray-mediated Antioxidant Potentials are Important for Attenuating Psychotoxic Disorders

Far-infrared ray (FIR) is an electromagnetic wave that produces various health benefits against pathophysiological conditions, such as diabetes mellitus, renocardiovascular disorders, stress, and depression etc. However, the therapeutic ap-plication on the FIR-mediated protective potentials remains to be further extended. To achieve better understanding on FIR-mediated therapeutic potentials, we summarized additional findings in the present study that exposure to FIR ameliorates stressful condition, memory impairments, drug dependence, and mitochondrial dysfunction in the central nervous system. In this review, we underlined that FIR requires modulations of janus kinase 2 / signal transducer and activator of transcription 3 (JAK2/STAT3), nuclear factor E2-related factor 2 (Nrf-2), muscarinic M1 acetylcholine receptor (M1 mAChR), dopamine D1 receptor, protein kinase C δ gene, and glutathione peroxidase-1 gene for exerting the protective potentials in response to neuropsychotoxic conditions

Maternal Immune Activation and the Development of Dopaminergic Neurotransmission of the Offspring: Relevance for Schizophrenia and Other Psychoses

Prenatal infections have been linked to the development of schizophrenia (SCZ) and other neurodevelopmental disorders in the offspring, and work in animal models indicates that this is to occur through the maternal inflammatory response triggered by infection. Several studies in animal models demonstrated that acute inflammatory episodes are sufficient to trigger brain alterations in the adult offspring, especially in the mesolimbic dopamine (DA) system, involved in the pathophysiology of SCZ and other disorders involving psychosis. In the current review, we synthesize the literature on the clinical studies implicating prenatal infectious events in the development of SCZ. Then, we summarize evidence from animal models of maternal immune activation (MIA) and the behavioral and molecular alterations relevant for the function of the DAergic system. Furthermore, we discuss the evidence supporting the involvement of maternal cytokines, such as interleukin 6 (IL-6) and leptin (a hormone with effects on inflammation) in mediating the effects of MIA on the fetal brain, leading to the long-lasting effects on the offspring. In particular, IL-6 has been involved in mediating the effects of MIA animal models in the offspring through actions on the placenta, induction of IL-17a, or triggering the decrease in non-heme iron (hypoferremia). Maternal infection is very likely interacting with additional genetic and environmental risk factors in the development of SCZ; systematically investigating how these interactions produce specific phenotypes is the next step in understanding the etiology of complex psychiatric disorders.

Enduring effects of juvenile social isolation on physiological properties of medium spiny neurons in nucleus accumbens

RATIONALE

Juvenile social isolation (SI) and neglect is associated with a wide range of psychiatric disorders. While dysfunction of the corticolimbic pathway is considered to link various abnormal behaviors in SI models of schizophrenia, the enduring effects of early social deprivation on physiological properties of medium spiny neurons (MSNs) in nucleus accumbens (NAc) are not well understood.

OBJECTIVES

This study investigated the impacts of juvenile SI on locomotor activity to methamphetamine (METH) and neurophysiological characteristics of MSNs in the core of NAc.

METHODS

Socially isolated C57BL/6 mice experienced single housing for 4 weeks on postnatal day (PND) 21. The locomotor response to METH (1.0 mg/kg) was observed in both socially isolated and group-housed mice at PND 56. The effects of juvenile SI on the excitatory synaptic events in MSNs and the intrinsic excitability of MSNs in NAc core were investigated in other batches during PND 63-70.

RESULTS

Socially isolated mice showed locomotor hypersensitivity to METH, although the expression of locomotor sensitization to METH in socially isolated mice was not different from group-housed mice. The recordings from MSNs of SI-reared mice exhibited higher frequency and smaller amplitude of miniature/spontaneous excitatory postsynaptic current than those from group-reared mice. Moreover, SI resulted in increased intrinsic excitability of MSNs in adult mice.

CONCLUSIONS

These results demonstrate neuronal hyperactivity in the NAc of socially isolated mice, which could contribute to locomotor hypersensitivity to METH. Furthermore, the findings indicate a biological link between early negative life events and the vulnerability to psychostimulant-induced psychosis in adulthood.

Relationship between schizophrenia and changes in the expression of the long non-coding RNAs Meg3, Miat, Neat1 and Neat2

Schizophrenia (SZ) is a complex disease caused by multiple factors. The development of the disease is mediated by a number of neural growth and development factors, suggesting that extensive changes in nerve structure and abnormal expression of genes in some important signalling pathways occur. Based on accumulating evidence, long non-coding RNAs (lncRNAs) play a crucial role in regulating neural diseases, including SZ. In the current study, we used mouse models of methamphetamine (METH) - and MK801-induced SZ to investigate changes in the expression of four lncRNAs (Meg3, Miat, Neat1 and Neat2) in the prefrontal cortex (PFC). Miat and Neat2 expression was significantly decreased in the PFC of the SZ model mice, regardless of whether the disease was induced by MK801 or METH. We further measured the levels of these lncRNAs in the peripheral blood (PB) collected from treated and untreated patients with SZ and from healthy controls. Neat1 and Neat2 levels were significantly decreased in the PB of untreated patients with SZ, but the trends in the expression of these lncRNAs nearly reached a normal level in treated patients with SZ. In conclusion, Neat2 and Miat may function as important regulators of SZ. Our findings provide important clues for new targets of lncRNAs that are involved in SZ.

Understanding the pediatric psychiatric phenotype of 22q11.2 deletion syndrome

The purpose of this article is to provide an overview of current insights into the neurodevelopmental and psychiatric manifestations of 22q11.2 deletion syndrome (22q11DS) in children and adolescents. The pediatric neuropsychiatric expression of 22q11DS is characterized by high variability, both interindividual and intraindividual (different expressions over the lifespan). Besides varying levels of intellectual disability, the prevalence of autism spectrum disorders, attention deficit disorders, anxiety disorders, and psychotic disorders in young individuals with 22q11DS is significantly higher than in the general population, or in individuals with idiopathic intellectual disability. Possible explanations for this observed phenotypic variability will be discussed, including genetic pleiotropy, gene-environment interactions, the age-dependency of phenotypes, but also the impact of assessment and ascertainment bias as well as the limitations of our current diagnostic classification system. The implications inferred by these observations aforementioned bear direct relevance to both scientists and clinicians. Observations regarding the neuropsychiatric manifestations in individuals with 22q11DS exemplify the need for a dimensional approach to neuropsychiatric assessment, in addition to our current categorical diagnostic classification system. The potential usefulness of 22q11DS as a genetic model to study the early phases of schizophrenia as well as the phenomenon of neuropsychiatric pleiotropy observed in many CNV's will be delineated. From a clinical perspective, the importance of regular neuropsychiatric evaluations with attention to symptoms not always captured in diagnostic categories and of maintaining equilibrium between individual difficulties and competencies and environmental demands will be discussed.

The relationship between illicit amphetamine use and psychiatric symptom profiles in schizophrenia and affective psychoses

This study examines whether illicit amphetamine use is associated with differences in the prevalence of specific psychiatric symptoms in a community sample of individuals diagnosed with schizophrenia or affective psychotic disorders. Data was drawn from the Australian Survey of High Impact Psychosis. The Diagnostic Interview for Psychosis was used to measure substance use and psychiatric symptoms. Participants had used amphetamine within their lifetime and had an ICD-10 diagnosis of schizophrenia (n = 347) or an affective psychotic disorder (n = 289). The past year prevalence of psychiatric symptoms was compared among those who had used amphetamine in the past year (past-year use, 32%) with those who had not (former use, 68%). Univariate logistic regression analysis indicated that past-year users with schizophrenia had a significantly higher past year prevalence of hallucinations, persecutory delusions, racing thoughts, dysphoria, and anhedonia relative to former amphetamine users with schizophrenia. There were no significant differences in symptoms between past-year and former users with affective psychotic disorders. The relationship between amphetamine use and specific psychiatric symptoms varies across different psychotic disorders. Amphetamine use may hinder prognosis by exacerbating symptoms of schizophrenia through dopaminergic dysfunctions or depressive vulnerabilities, however, this needs to be confirmed by prospective longitudinal research.

Neuregulin-2 ablation results in dopamine dysregulation and severe behavioral phenotypes relevant to psychiatric disorders

Numerous genetic and functional studies implicate variants of Neuregulin-1 (NRG1) and its neuronal receptor ErbB4 in schizophrenia and many of its endophenotypes. Although the neurophysiological and behavioral phenotypes of NRG1 mutant mice have been investigated extensively, practically nothing is known about the function of NRG2, the closest NRG1 homolog. We found that NRG2 expression in the adult rodent brain does not overlap with NRG1 and is more extensive than originally reported, including expression in the striatum and medial prefrontal cortex (mPFC), and therefore generated NRG2 knockout mice (KO) to study its function. NRG2 KOs have higher extracellular dopamine levels in the dorsal striatum but lower levels in the mPFC; a pattern with similarities to dopamine dysbalance in schizophrenia. Like ErbB4 KO mice, NRG2 KOs performed abnormally in a battery of behavioral tasks relevant to psychiatric disorders. NRG2 KOs exhibit hyperactivity in a novelty-induced open field, deficits in prepulse inhibition, hypersensitivity to amphetamine, antisocial behaviors, reduced anxiety-like behavior in the elevated plus maze and deficits in the T-maze alteration reward test-a task dependent on hippocampal and mPFC function. Acute administration of clozapine rapidly increased extracellular dopamine levels in the mPFC and improved alternation T-maze performance. Similar to mice treated chronically with N-methyl-d-aspartate receptor (NMDAR) antagonists, we demonstrate that NMDAR synaptic currents in NRG2 KOs are augmented at hippocampal glutamatergic synapses and are more sensitive to ifenprodil, indicating an increased contribution of GluN2B-containing NMDARs. Our findings reveal a novel role for NRG2 in the modulation of behaviors with relevance to psychiatric disorders.

Association studies of WD repeat domain 3 and chitobiosyldiphosphodolichol beta-mannosyltransferase genes with schizophrenia in a Japanese population

Schizophrenia and schizophrenia-like symptoms induced by the dopamine agonists and N-methyl-D aspartate type glutamate receptor antagonists occur only after the adolescent period. Similarly, animal models of schizophrenia by these drugs are also induced after the critical period around postnatal week three. Based upon the development-dependent onsets of these psychotomimetic effects, by using a DNA microarray technique, we identified the WD repeat domain 3 (WDR3) and chitobiosyldiphosphodolichol beta-mannosyltransferase (ALG1) genes as novel candidates for schizophrenia-related molecules, whose mRNAs were up-regulated in the adult (postnatal week seven), but not in the infant (postnatal week one) rats by an indirect dopamine agonist, and phencyclidine, an antagonist of the NMDA receptor. WDR3 and other related proteins are the nuclear proteins presumably involved in various cellular activities, such as cell cycle progression, signal transduction, apoptosis, and gene regulation. ALG1 is presumed to be involved in the regulation of the protein N-glycosylation. To further elucidate the molecular pathophysiology of schizophrenia, we have evaluated the genetic association of WDR3 and ALG1 in schizophrenia. We examined 21 single nucleotide polymorphisms [SNPs; W1 (rs1812607)-W16 (rs6656360), A1 (rs8053916)-A10 (rs9673733)] from these genes using the Japanese case-control sample (1,808 schizophrenics and 2,170 matched controls). No significant genetic associations of these SNPs were identified. However, we detected a significant association of W4 (rs319471) in the female schizophrenics (allelic P = 0.003, genotypic P = 0.008). Based on a haplotype analysis, the observed haplotypes consisting of W4 (rs319471)–W5 (rs379058) also displayed a significant association in the female schizophrenics (P = 0.016). Even after correction for multiple testing, these associations remained significant. Our findings suggest that the WDR3 gene may likely be a sensitive factor in female patients with schizophrenia, and that modification of the WDR3 signaling pathway warrants further investigation as to the pathophysiology of schizophrenia.

Toward the Identification of a Specific Psychopathology of Substance Use Disorders

Addiction is a mental illness in which psychiatric conditions imply a prominent burden. Psychopathological symptoms in substance use disorder (SUD) patients are usually viewed as being assignable to the sphere of a personality trait or of comorbidity, leaving doubts about the presence of a specific psychopathology that could only be related to the toxicomanic process. Our research group at the University of Pisa has shed light on the possible definition of a specific psychopathological dimension in SUDs. In heroin use disorder patients, performing an exploratory principal component factor analysis (PCA) on all the 90 items included in the SCL-90 questionnaire led to a five-factor solution. The first factor accounted for a depressive "worthlessness and being trapped" dimension; the second factor picked out a "somatic symptoms" dimension; the third identified a "sensitivity-psychoticism" dimension; the fourth a "panic-anxiety" dimension; and the fifth a "violence-suicide" dimension. These same results were replicated by applying the PCA to another Italian sample of 1,195 heroin addicts entering a Therapeutic Community Treatment. Further analyses confirmed the clusters of symptoms, independently of demographic and clinical characteristics, active heroin use, lifetime psychiatric problems, kind of treatment received, and, especially, other substances used by the patient such as alcohol or cocaine. Moreover, these clusters were able to discriminate patients affected by addiction from those affected by psychiatric diseases such as major depressive disorder. Our studies seem to suggest the trait-dependent, rather than the state-dependent, nature of the introduced psychopathology dimensions of SUDs.

GABAergic mRNA expression is differentially expressed across the prelimbic and orbitofrontal cortices of rats sensitized to methamphetamine: Relevance to psychosis

Psychotic disorders, such as schizophrenia, are characterized by prevalent and persistent executive deficits that are believed to be the result of dysfunctional inhibitory gamma-aminobutyric acid (GABA) processing of the prefrontal cortex (PFC). Methamphetamine (METH) is a commonly used psychostimulant that can induce psychotic and cognitive symptoms that are indistinguishable to schizophrenia, suggesting that METH-induced psychosis may have a similar GABAergic profile of the PFC. As the PFC consists of multiple subregions, the aim of the current study was to investigate changes to GABAergic mRNA expression in the prelimbic (PRL) and orbitofrontal (OFC) cortices of the PFC in rats sensitized to repeated METH administration. Male Sprague Dawley rats underwent daily METH or saline injections for 7 days. Following 14 days of withdrawal, rats were challenged with acute METH administration, RNA was isolated from the PRL and OFC and quantitative PCR was used to compare the relative expression of GABA enzymes, transporters, metabolites and receptor subunits. GAD₆₇, GAD₆₅, GAT₁, GAT₃, VGAT and GABA_T mRNA expression were upregulated in the PRL. Ionotropic GABAA receptor subunits α1, α3, α5 and β2 were specifically upregulated in the OFC. These findings suggest that alterations to GABAergic mRNA expression following sensitization to METH are biologically dissociated between the OFC and PRL, suggesting that GABAergic gene expression is significantly altered following chronic METH exposure in a brain-region and GABA-specific manner. These changes may lead to profound consequences on central inhibitory mechanisms of localized regions of the PFC and may underpin common behavioral phenotypes seen across psychotic disorders.

GABAergic mRNA expression is upregulated in the prefrontal cortex of rats sensitized to methamphetamine

Inhibitory gamma-aminobutyric acid (GABA)-mediated neurotransmission plays an important role in the regulation of the prefrontal cortex (PFC), with increasing evidence suggesting that dysfunctional GABAergic processing of the PFC may underlie certain deficits reported across psychotic disorders. Methamphetamine (METH) is a psychostimulant that induces chronic psychosis in a subset of users, with repeat administration producing a progressively increased vulnerability to psychotic relapse following subsequent drug administration (sensitization). The aim here was to investigate changes to GABAergic mRNA expression in the PFC of rats sensitized to METH using quantitative polymerase chain reaction (qPCR). Male Sprague-Dawley rats (n=12) underwent repeated methamphetamine (intraperitoneal (i.p.) or saline injections for 7 days. Following 14 days of withdrawal, rats were challenged with acute methamphetamine (1mg/kg i.p.) and RNA was isolated from the PFC to compare the relative mRNA expression of a range of GABA enzymes, transporters and receptors subunits. METH challenge resulted in a significant sensitized behavioral (locomotor) response in METH pre-treated animals compared with saline pre-treated controls. The mRNAs of transporters (GAT1 and GAT3), ionotropic GABAA receptor subunits (α3 and β1), together with the metabotropic GABAB1 receptor, were upregulated in the PFC of sensitized rats compared with saline controls. These findings indicate that GABAergic mRNA expression is significantly altered at the pre and postsynaptic level following sensitization to METH, with sensitization resulting in the transcriptional upregulation of several inhibitory genes. These changes likely have significant consequences on GABA-mediated neurotransmission in the PFC and may underlie certain symptoms conserved across psychotic disorders, such as executive dysfunction.

Methamphetamine-induced sensitization is associated with alterations to the proteome of the prefrontal cortex: implications for the maintenance of psychotic disorders

Repeat administration of psychostimulants, such as methamphetamine, produces a progressive increase in locomotor activity (behavioral sensitization) in rodents that is believed to represent the underlying neurochemical changes driving psychoses. Alterations to the prefrontal cortex (PFC) are suggested to mediate the etiology and maintenance of these behavioral changes. As such, the aim of the current study was to investigate changes to protein expression in the PFC in male rats sensitized to methamphetamine using quantitative label-free shotgun proteomics. A methamphetamine challenge resulted in a significant sensitized locomotor response in methamphetamine pretreated animals compared to saline controls. Proteomic analysis revealed 96 proteins that were differentially expressed in the PFC of methamphetamine treated rats, with 20% of these being previously implicated in the neurobiology of schizophrenia in the PFC. We identified multiple biological functions in the PFC that appear to be commonly altered across methamphetamine-induced sensitization and schizophrenia, and these include synaptic regulation, protein phosphatase signaling, mitochondrial function, and alterations to the inhibitory GABAergic network. These changes could inform how alterations to the PFC could underlie the cognitive and behavioral dysfunction commonly seen across psychoses and places such biological changes as potential mediators in the maintenance of psychosis vulnerability.

In vivo amphetamine action is contingent on αCaMKII

Addiction to psychostimulants (ie, amphetamines and cocaine) imposes a major socioeconomic burden. Prevention and treatment represent unmet medical needs, which may be addressed, if the mechanisms underlying psychostimulant action are understood. Cocaine acts as a blocker at the transporters for dopamine (DAT), serotonin (SERT), and norepinephrine (NET), but amphetamines are substrates that do not only block the uptake of monoamines but also induce substrate efflux by promoting reverse transport. Reverse transport has been a focus of research for decades but its mechanistic basis still remains enigmatic. Recently, transporter-interacting proteins were found to regulate amphetamine-triggered reverse transport: calmodulin kinase IIα (αCaMKII) is a prominent example, because it binds the carboxyl terminus of DAT, phosphorylates its amino terminus, and supports amphetamine-induced substrate efflux in vitro. Here, we investigated whether, in vivo, the action of amphetamine was contingent on the presence of αCaMKII by recording the behavioral and neurochemical effects of amphetamine. Measurement of dopamine efflux in the dorsal striatum by microdialysis revealed that amphetamine induced less dopamine efflux in mice lacking αCaMKII. Consistent with this observation, the acute locomotor responses to amphetamine were also significantly blunted in αCaMKII-deficient mice. In addition, while the rewarding properties of amphetamine were preserved in αCaMKII-deficient mice, their behavioral sensitization to amphetamine was markedly reduced. Our findings demonstrate that amphetamine requires the presence of αCaMKII to elicit a full-fledged effect on DAT in vivo: αCaMKII does not only support acute amphetamine-induced dopamine efflux but is also important in shaping the chronic response to amphetamine.

Animal Models of Psychosis: Current State and Future Directions

Psychosis is an abnormal mental state characterized by disorganization, delusions and hallucinations. Animal models have become an increasingly important research tool in the effort to understand both the underlying pathophysiology and treatment of psychosis. There are multiple animal models for psychosis, with each formed by the coupling of a manipulation and a measurement. In this manuscript we do not address the diseases of which psychosis is a prominent comorbidity. Instead, we summarize the current state of affairs and future directions for animal models of psychosis. To accomplish this, our manuscript will first discuss relevant behavioral and electrophysiological measurements. We then provide an overview of the different manipulations that are combined with these measurements to produce animal models. The strengths and limitations of each model will be addressed in order to evaluate its cross-species comparability.

The neurobiology of relapse in schizophrenia

Dopamine's proposed role in psychosis proved a starting point in our understanding of the neurobiology of relapse, fitting given the central role positive symptoms play. This link is reflected in early work examining neurotransmitter metabolite and drug (e.g. amphetamine, methylphenidate) challenge studies as a means of better understanding relapse and predictors. Since, lines of investigation have expanded (e.g. electrophysiological, immunological, hormonal, stress), an important step forward if relapse per se is the question. Arguably, perturbations in dopamine represent the final common pathway in psychosis but it is evident that, like schizophrenia, relapse is heterogeneous and multidimensional. In understanding the neurobiology of relapse, greater gains are likely to be made if these distinctions are acknowledged; for example, efforts to identify trait markers might better be served by distinguishing primary (i.e. idiopathic) and secondary (e.g. substance abuse, medication nonadherence) forms of relapse. Similarly, it has been suggested that relapse is 'neurotoxic', yet individuals do very well on clozapine after multiple relapses and the designation of treatment resistance. An alternative explanation holds that schizophrenia is characterized by different trajectories, at least to some extent biologically and/or structurally distinguishable from the outset, with differential patterns of response and relapse. Just as with schizophrenia, it seems naïve to conceptualize the neurobiology of relapse as a singular process. We propose that it is shaped by the form of illness and in place from the outset, modified by constitutional factors like resilience, as well as treatment, and confounded by secondary forms of relapse.

Psychopathological symptoms of patients with heroin addiction entering opioid agonist or therapeutic community treatment

BACKGROUND

The relationship between substance use disorders and psychiatric pathology is still an open question. The main aim of the present study was to verify whether the five psychopathological dimensions identified through the SCL-90 tool in a previous study carried out on patients with heroin addiction entering an outpatient opioid agonist treatment (OAT) were also observable in those entering a residential treatment community (TC). Further aims were to look at differences in the psychopathological profiles of patients entering a TC versus an OAT treatment and at the correlation between gender and the observed psychopathology.

METHODS

A confirmatory factor analysis was performed on the results of SCL-90 filled by 1,195 patients with heroin dependence entering TC treatment. It replicates the extraction method previously used on 1,055 OAT patients with heroin addiction by using a principal component factor analysis (PCA). The association between the kind of treatment received (TC or OAT), gender, and the psychopathological dimensions was assessed through logistic regression and general linear model (GLM) analysis.

RESULTS

The PCA carried out on the SCL-90 results of patients entering a TC yielded a five-factor solution, confirming the same dimensions observed in patients entering an OAT: 'worthlessness and being trapped', 'somatization', 'sensitivity-psychoticism', 'panic anxiety', and 'violence-suicide'. The logistic regression analysis showed a statistically significant association between 'somatization' and 'violence-suicide' severity score and OAT. GLM analysis showed that psychopathological factorial scores for 'worthlessness-being trapped', 'somatic symptoms', and 'panic anxiety' dimensions were more severe in OAT vs TC male patients and in TC vs OAT female ones. 'Violence suicide' followed the same severity pattern for males, but did not differ in TC vs OAT females, while 'sensitivity-psychoticism' did not differ in OAT vs TC patients. The five dimensions did not differ in OAT males vs females.

CONCLUSIONS

Our research appears to confirm the existence of a specific aggregation of psychological/psychiatric features within the category of individuals with heroin addiction. It also shows a correlation between the dominant psychopathological subgroup and the assignment to TC versus OAT. Further research is needed to clarify the differences between the five psychopathological subgroups and their determinants.

Chronic cannabinoid exposure reduces phencyclidine-induced schizophrenia-like positive symptoms in adult rats

RATIONALE

Chronic cannabis use can induce psychotic states that resemble schizophrenia. Yet, schizophrenic patients often smoke cannabis as a form of self-medication to counter the aversive symptoms of schizophrenia. We recently demonstrated an ameliorating effect of cannabinoid self-administration (SA) on negative and cognitive schizophrenia-like symptoms induced experimentally by the non-competitive N-methyl-D-aspartate receptor antagonist phencyclidine (PCP). Whether cannabinoid SA alleviates or exacerbates schizophrenia-like positive symptoms is still unclear.

OBJECTIVES

This follow-up study aimed to evaluate the effect of self-administered cannabinoid on PCP-induced schizotypic positive symptoms in adult rats.

METHODS

Male rats were trained to self-administer either the cannabinoid CB1 receptor agonist WIN 55,212-2 (WIN; 12.5 μg/kg/infusion) or its vehicle (Veh) intravenously. The effects of acute and chronic intermittent intraperitoneal administration of PCP (2.5 mg/kg) on motor parameters were then tested in Veh-SA and WIN-SA.

RESULTS

Cannabinoid SA significantly attenuated the psychotomimetic effects of PCP exposure observed in control rats. Following acute PCP administration, WIN-SA animals displayed more frequent rearing and lower anxiety-like profile than Veh-SA rats. WIN-SA rats also exhibited lower behavioural sensitisation to chronic PCP treatment as demonstrated by reduced hyperlocomotion in response to an acute PCP challenge. In addition, parallel experiments performed in experimenter-administered rats that received WIN at comparable SA doses confirmed the ameliorating effects of cannabinoid exposure on PCP-induced schizotypic behaviours, indicating that motivational effects were not responsible for the ameliorative effects of cannabinoids.

CONCLUSIONS

Our results indicate that cannabis may exert protective effects on positive schizotypic symptoms in adult animals such as hypermotility and anxiety state.

Variable maternal stress in rats alters locomotor activity, social behavior, and recognition memory in the adult offspring

Rats repeatedly exposed to variable prenatal stress (PNS) exhibit behavioral signs that are similar to those manifested in several neuropsychiatric disorders such as deficits in attention and inhibitory control, and impairments in memory-related task performance. The purpose of the study described here was to conduct a comprehensive battery of tests to further characterize the behavioral phenotype of PNS rats as well as to evaluate the sensitivity of the model to therapeutic interventions (i.e., to compounds previously shown to have therapeutic potential in neuropsychiatric disorders). The results of this study indicated that PNS in rats is associated with: 1) increased locomotor activity and stereotypic behaviors, 2) elevated sensitivity to the psychostimulant amphetamine, 3) increased aggressive behaviors toward both adult and juvenile rats and 4) delay-dependent deficits in recognition memory. There was no evidence that PNS rats exhibited deficits in other areas of motor function/learning, sensorimotor gating, spatial learning and memory, social withdrawal, or anhedonia. In addition, the results revealed that the second generation antipsychotic risperidone attenuated amphetamine-related increases in locomotor activity in PNS rats; however, the effect was not sustained over time. Furthermore, deficits in recognition memory in PNS rats were attenuated by the norepinephrine reuptake inhibitor, atomoxetine, but not by the α7 nicotinic acetylcholine receptor partial agonist, GTS-21. This study supports the supposition that important phenomenological similarities exist between rats exposed to PNS and patients afflicted with neuropsychiatric disorders thus further establishing the face validity of the model for evaluating potential therapeutic interventions.

The γ-aminobutyric acid type B (GABAB) receptor agonist baclofen inhibits morphine sensitization by decreasing the dopamine level in rat nucleus accumbens

Background

Repeated morphine exposure can induce behavioral sensitization. There are evidences have shown that central gamma-aminobutyric acid (GABA) system is involved in morphine dependence. However, the effect of a GABA_B receptor agonist baclofen on morphine-induced behavioral sensitization in rats is unclear.

Methods

We used morphine-induced behavioral sensitization model in rat to investigate the effects of baclofen on behavioral sensitization. Moreover, dopamine release in the shell of the nucleus accumbens was evaluated using microdialysis assay in vivo.

Results

The present study demonstrated that morphine challenge (3 mg/kg, s.c.) obviously enhanced the locomotor activity following 4-day consecutive morphine administration and 3-day withdrawal period, which indicated the expression of morphine sensitization. In addition, chronic treatment with baclofen (2.5, 5 mg/kg) significantly inhibited the development of morphine sensitization. It was also found that morphine challenge 3 days after repeated morphine administration produced a significant increase of extracellular dopamine release in nucleus accumbens. Furthermore, chronic treatment with baclofen decreased the dopamine release induced by morphine challenge.

Conclusions

Our results indicated that gamma-aminobutyric acid system plays an important role in the morphine sensitization in rat and suggested that behavioral sensitization is a promising model to study the mechanism underlying drug abuse.

Effects of antipsychotics and amphetamine on social behaviors in spontaneously hypertensive rats

We have recently reported that spontaneously hypertensive rats (SHRs) exhibit a deficit in contextual fear conditioning that is specifically reversed by antipsychotic and potentiated by psychostimulants and other manipulations thought to produce schizophrenia-like states in rodents. Based on these findings, we suggested that this deficit in fear conditioning could be used as an experimental model of emotional processing impairments observed in schizophrenia. This strain has also been suggested as a model by which to study attention deficit/hyperactivity disorder (ADHD). Considering that schizophrenia and ADHD are both characterized by poor social function, this study aimed to investigate possible behavioral deficits of SHRs in a social context. Furthermore, we sought to examine the effects of typical and atypical antipsychotics (used for the treatment of schizophrenia) and a psychostimulant (used to treat ADHD) on these behaviors. Pairs of unfamiliar rats of the same or different (i.e., Wistar) strains were treated with one of the aforementioned drugs and placed in an open-field for 10min. During this time, social behaviors, locomotion and rearing frequencies were scored. Atypical antipsychotics increased social interaction in Wistar rats (WRs) and improved the deficit in social interaction exhibited by SHRs. In addition, the SHR group displayed hyperlocomotion that was attenuated by all antipsychotics (quetiapine and clozapine also decreased locomotion in WRs) and potentiated by amphetamine (which also increased locomotion in WRs). Our results reveal that the behavioral profile of the SHR group demonstrates that this strain can be a useful animal model to study several aspects of schizophrenia.

Cholinergic contributions to the cognitive symptoms of schizophrenia and the viability of cholinergic treatments

Effective treatment of the cognitive symptoms of schizophrenia has remained an elusive goal. Despite the intense focus on treatments acting at or via cholinergic mechanisms, little remains known about the dynamic cholinergic abnormalities that contribute to the manifestation of the cognitive symptoms in patients. Evidence from basic neuroscientific and psychopharmacological investigations assists in proposing detailed cholinergic mechanisms and treatment targets for enhancement of attentional performance. Dynamic, cognitive performance-dependent abnormalities in cholinergic activity have been observed in animal models of the disorder and serve to further refine such proposals. Finally, the potential usefulness of individual groups of cholinergic drugs and important issues concerning the interactions between pro-cholinergic and antipsychotic treatments are addressed. The limited evidence available from patient studies and animal models indicates pressing research needs in order to guide the development of cholinergic treatments of the cognitive symptoms of schizophrenia.

Delineating the psychic structure of substance abuse and addictions: should anxiety, mood and impulse-control dysregulation be included?

Current "official" nosology (e.g. DSM IV) is largely limited to physical manifestations of addiction that can be objectively observed and are suited to the maintaining of an "atheoretical" perspective. However, addicted subjects display additional psychiatric symptoms that affect their well-being and social functioning and, in accordance with DSM IV, are typically relegated to the domain of psychiatric "comorbidity." We contend that the relationship of these psychiatric symptoms with addiction is very close, as demonstrated by the high frequency of association observed. We further assert that substance use may modify pre-existing psychic structures such as temperament and related subthreshold conditions and lead to addiction as a specific mental disorder, inclusive also of symptoms pertaining to mood/anxiety, or impulse-control dimensions. The present contribution addresses the weaknesses of the current DSM-based nosology of addiction-related mental comorbidity. We highlight the overlap of the biological substrates and the neurophysiology of addictive processes and psychiatric symptoms associated with addiction, and propose the inclusion of specific mood, anxiety, and impulse-control dimensions in the psychopathology of addictive processes. We postulate that addiction reaches beyond the mere result of drug-elicited effects on the brain and cannot be peremptorily equated only with the use of drugs despite the adverse consequences produced. We infer that mood, anxiety and impulse-control dysregulation is at the very core of both the origins and clinical manifestations of addiction and should be incorporated into the nosology of the same, emphasising how addiction is a relapsing chronic condition in which psychiatric manifestations play a crucial role. To conclude, addictionology cannot be severed from its psychopathological connotations, in view of the undeniable presence of symptoms, of their manifest contribution to the way addicted patients feel and behave, and to the role they play in maintaining the continued use of substances.

Effects of clozapine on behavioral sensitization induced by cocaine

Using cocaine-sensitized mice as a model for psychosis, this study investigated whether subchronic treatment with clozapine could affect the sensitized state of the animals and examined the accompanying molecular changes in the brain. To induce sensitization, ICR mice (n=44) were treated with cocaine for 5 days. After 7 days of withdrawal, sensitization was confirmed by a cocaine challenge. Then, the sensitized animals were treated with clozapine for 5 days and rechallenged with cocaine. The frontal cortices were removed from the mice (n=16) 24 h after the last challenge, and the phosphorylation status of some key signaling molecules was investigated. Compared with the sensitized mice receiving the vehicle treatment, the sensitized mice receiving subchronic clozapine showed less locomotor activity, with an activity level similar to that of non-sensitized mice. However, clozapine did not directly affect the stimulatory effect of cocaine. Clozapine also reversed some of the sensitization-induced biochemical changes, including increased phosphorylation of GSK-3beta and CREB, in the frontal cortex. Subchronic treatment with clozapine apparently de-sensitized the sensitized mice. The long-term effect of clozapine on stimulant-induced sensitization may be related to the therapeutic effect of the drug as an antipsychotic agent.

Effects of electroconvulsive shock on the phosphorylation of DARPP-32 in rat striatum

Dopamine- and cAMP-regulated phosphoprotein with molecular weight 32 kDa (DARPP-32) is a key integrative molecule in the dopaminergic and glutamatergic signaling pathways in the striatum. Electroconvulsive shock (ECS), which induces massive neuronal depolarization, can activate various signaling pathways. In this study we investigated whether ECS could affect the phosphorylation status of DARPP-32. Male Sprague-Dawley rats underwent ECS and were sacrificed by decapitation at 0, 2, 10, 60, and 180 min after treatment. The phosphorylations of Thr34 and Thr75 residues of DARPP-32 and Ser159 residue of cyclin-dependent kinase 5 (CDK5) were investigated in the striatum. The activity of protein phosphatase 1 (PP1) and the binding between DARPP-32 and PP1 were also analyzed. Thr34 phosphorylation of DARPP-32 increased immediately after ECS and this state was maintained for more than 60 min. The activity of PP1 decreased and the binding between PP1 and DARPP-32 increased in accordance with this phosphorylation pattern. However, the phosphorylation at Thr75 showed no significant change except for an initial transient decrease. The phosphorylation of CDK5, which is responsible for Thr75 phosphorylation of DARPP-32, did not exhibit significant fluctuations. Our findings indicate that ECS increases Thr34 phosphorylation of DARPP-32, and thus inhibits the activity of PP1.

Neuropsychiatric correlates of traumatic brain injury (TBI) among Australian prison entrants

PRIMARY OBJECTIVE

To investigate the association between reported past traumatic brain injury (TBI) and demographic, neuropsychiatric and criminographic parameters among individuals recently received into custody.

RESEARCH DESIGN

A random sample of men recently received into the New South Wales (Australia) criminal justice system were screened for a history of TBI and the details of up to five separate TBI episodes were obtained. We also screened for depression, psychosis, personality disorder, drug and alcohol use, and 'social connectedness'.

MAIN OUTCOME AND RESULTS

Among the 200 study participants, 82% reported past TBI. TBI was associated with a history of engagement in contact sports, school expulsion, daily illicit drug use, depression and psychosis.

CONCLUSIONS

Past TBI is common among prisoners entering the criminal justice system and, amongst other correlates, appears to be highly associated with increased rates of major mental illness.

Recent advances in treating cognitive impairment in schizophrenia

INTRODUCTION

Schizophrenia is often associated with chronic disability and poor outcome. In addition to positive symptoms, such as hallucinations and delusions, and negative symptoms including poverty of speech and blunted affect, schizophrenia is also associated with deficits in cognitive function. It has been increasingly recognized that the severity of cognitive impairment is a major determinant of outcome. Therefore, interventions to improve cognitive function also have the capacity to improve quality of life and social and occupational outcomes. Whilst some of the antipsychotic drugs have shown some selective benefits, there is some controversy about the extent of these benefits.

OBJECTIVES

This article provides an overview of research into drugs that might enhance cognition in schizophrenia.

CONCLUSION

Drugs such as modafanil and galantamine are being evaluated, and a number of new drugs are currently in development. Standardized cognitive assessment measures are being developed so studies can be compared more easily. This field is advancing rapidly, but as yet, no widely applicable, evidence-based treatments are available to the clinician.

Intermittent Dopaminergic stimulation causes behavioral sensitization in the addicted brain and parkinsonism

The gold standard therapy for Parkinson's disease (PD) consists in chronic administration of pulses of the dopamine (DA) precursor l-dihydroxyphenylalanine (l-DOPA). Although the main brain area which is DA-deficient is the dorsal striatum (more the putamen than the caudate nucleus), other DA-innervated brain regions (i.e., the ventral striatum and other limbic areas) are affected by systemic administration of l-DOPA. While such a therapy produces an increase in synaptic and nonsynaptic DA, which replace the neurotransmitter deficiency, peaks of extracellular DA in the course of disease progression produce abnormal involuntary movements related to behavioral sensitization. Methamphetamine (METH), a widely abused drug, is known to produce behavioral sensitization, related to DA release (more in the ventral than dorsal striatum as well as other limbic regions). The present review discusses the overlapping between these treatments, based on pulses of DA stimulation with an emphasis on the class of DA receptors; signal transduction pathways; rearranged expression of neurotransmitters, cotransmitters, and their receptors coupled with ultrastructural changes. In fact, all these levels of synaptic plasticity show a surprising homology following these treatments, posing the mechanisms of behavioral sensitization during DA-replacement therapy in PD very close to the neurobiological mechanisms operating during METH abuse. In line with this view is the growing evidence of addictive behaviors in PD patients during the course of DA-replacement therapy.

A neurocognitive animal model dissociating between acute illness and remission periods of schizophrenia

RATIONALE

The development and validation of animal models of the cognitive impairments of schizophrenia have remained challenging subjects.

OBJECTIVE

We review evidence from a series of experiments concerning an animal model that dissociates between the disruption of attentional capacities during acute illness periods and the cognitive load-dependent impairments that characterize periods of remission. The model focuses on the long-term attentional consequences of an escalating-dosing pretreatment regimen with amphetamine (AMPH).

RESULTS

Acute illness periods are modeled by the administration of AMPH challenges. Such challenges result in extensive impairments in attentional performance and the "freezing" of performance-associated cortical acetylcholine (ACh) release at pretask levels. During periods of remission (in the absence of AMPH challenges), AMPH-pretreated animals' attentional performance is associated with abnormally high levels of performance-associated cortical ACh release, indicative of the elevated attentional effort required to maintain performance. Furthermore, and corresponding with clinical evidence, attentional performance during remission periods is exquisitely vulnerable to distractors, reflecting impaired top-down control and abnormalities in fronto-mesolimbic-basal forebrain circuitry. Finally, this animal model detects the moderately beneficial cognitive effects of low-dose treatment with haloperidol and clozapine that were observed in clinical studies.

CONCLUSIONS

The usefulness and limitations of this model for research on the neuronal mechanisms underlying the cognitive impairments in schizophrenia and for drug-finding efforts are discussed.

Detection of the moderately beneficial cognitive effects of low-dose treatment with haloperidol or clozapine in an animal model of the attentional impairments of schizophrenia

The absence of effective cognition enhancers for the treatment of patients with schizophrenia limits the validation of animal models and behavioral tests used for drug finding and characterization. However, low doses of haloperidol and clozapine were documented to produce moderately beneficial effects in patients. Therefore, this experiment was designed to determine the attentional effects of such treatments in a repeated-amphetamine (AMPH) animal model. Animals were trained in an operant-sustained attention task and underwent a 40-day pretreatment period with saline or increasing doses (1-10 mg per kg) of AMPH. After regaining baseline performance following 10 days of saline treatment, animals were treated with haloperidol (0.025 mg per kg), clozapine (2.5 mg per kg), or vehicle for 10 days. Furthermore, the effects of AMPH challenges (1.0 mg per kg) were assessed. In AMPH-pretreated animals, the administration of AMPH challenges resulted in the disruption of attentional performance. Treatment with haloperidol and clozapine attenuated the detrimental performance effects of these challenges, with clozapine exhibiting more robust attenuation. Furthermore, clozapine, but not haloperidol, impaired the performance of control animals. In contrast, the performance of AMPH-pretreated animals remained unaffected by clozapine. As this animal model detects the moderately beneficial cognitive effects of haloperidol and clozapine, it may be useful for preclinical research designed to detect and characterize treatments for the cognitive symptoms of schizophrenia.

Toward a neuro-cognitive animal model of the cognitive symptoms of schizophrenia: disruption of cortical cholinergic neurotransmission following repeated amphetamine exposure in attentional task-performing, but not non-performing, rats

Impairments in attentional functions and capacities represent core aspects of the cognitive symptoms of schizophrenia. Attentional performance has been demonstrated to depend on the integrity and activity of cortical cholinergic inputs. The neurobiological, behavioral, and cognitive effects of repeated exposure to psychostimulants model important aspects of schizophrenia. In the present experiment, prefrontal acetylcholine (ACh) release was measured in attentional task-performing and non-performing rats pretreated with an escalating dosing regimen of amphetamine (AMPH) and following challenges with AMPH. In non-performing rats, pretreatment with AMPH did not affect the increases in ACh release produced by AMPH-challenges. In contrast, attentional task performance-associated increases in ACh release were attenuated in AMPH-pretreated and AMPH-challenged rats. This effect of repeated AMPH exposure on ACh release was already present before task-onset, suggesting that the loss of cognitive control that characterized these animals' performance was a result of cholinergic dysregulation. The findings indicate that the demonstration of repeated AMPH-induced dysregulation of the prefrontal cholinergic input system depends on interactions between the effects of repeated AMPH exposure and cognitive performance-associated recruitment of this neuronal system. Repeated AMPH-induced disruption of prefrontal cholinergic activity and attentional performance represents a useful model to investigate the cholinergic mechanisms contributing to the cognitive impairments of schizophrenia.

Neurotoxicity of substituted amphetamines: Molecular and cellular mechanisms

The amphetamines, including amphetamine (AMPH), methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA), are among abused drugs in the US and throughout the world. Their abuse is associated with severe neurologic and psychiatric adverse events including the development of psychotic states. These neuropsychiatric complications might, in part, be related to drug-induced neurotoxic effects, which include damage to dopaminergic and serotonergic terminals, neuronal apoptosis, as well as activated astroglial and microglial cells in the brain. The purpose of the present review is to summarize the toxic effects of AMPH, METH and MDMA. The paper also presents some of the factors that are thought to underlie this toxicity. These include oxidative stress, hyperthermia, excitotoxicity and various apoptotic pathways. Better understanding of the cellular and molecular mechanisms involved in their toxicity should help to generate modern therapeutic approaches to prevent or attenuate the long-term consequences of amphetamine use disorders in humans.

Disruption of reelin signaling attenuates methamphetamine-induced hyperlocomotion

To clarify whether reelin signaling is involved in dopaminergic neurotransmission in the adult mouse brain, we investigated dopamine function in mice lacking reelin (reeler). We found that methamphetamine-induced locomotor activity is significantly attenuated in reeler mice. To elucidate the mechanism of this phenomenon, we first investigated presynaptic dopamine release; however, there were no significant differences in wildtype, heterozygous reeler and homozygous reeler mice. Next, we examined the locomotor response to intra-accumbens injection of dopamine D1 and D2 receptor agonists, and found that lack of reelin signaling results in decreases in both D1 and D2 receptor-mediated dopaminergic functions. In addition, we measured dopamine receptor binding in the striatum, and found that both D1 and D2 classes of dopamine receptors are reduced in reeler mice. Furthermore, we found that the phosphorylation levels of DARPP-32 are also changed by lack of reelin signaling. Finally, to distinguish between a developmental role of reelin or an acute role of reelin in adult mouse, we intraventricularly infused CR-50, a monoclonal antibody against reelin. Interestingly, infusion of CR-50 also significantly reduced methamphetamine-induced hyperlocomotion in wildtype mice, showing that reelin has an acute role in the dopaminergic system. These results indicate that reelin signaling plays a pivotal role in the dopaminergic system in adult mice, especially in postsynaptic levels.

Stress sensitization in schizophrenia

It is well known that environmental factors, such as early life events, perinatal damage, and urbanicity, which interact with multiple genes, induces persistent sensitization to stress possibly through an imbalance in interactions between dopaminergic and glutamatergic systems. This stress sensitization may be critical in the development or relapse of schizophrenia. The neural correlates of a negative mood might be impaired, resulting in stress sensitization and difficulties in social adjustment (Dr. Habel). Urbanicity is associated with later schizophrenia. Metabolic stress induces stress sensitization via dysregulation of dopaminergic and/or noradrenergic systems in activated HVA and cortical response (Dr. Marcelis). The glutamatergic regulation activates HPA axis in stress response (Dr. Zelena). Ameloblast activity in human molar's enamel slowed by exposure to stress, and the segment of enamel rods is smaller, making a particular dark line. Stress sensitization may be induced at the age of 10.5 to 11.5 years resulting from severe emotional stress at the age of 10.5 to 11.5 years (Dr. Yui). It has been reported that volume reductions in the amygdala, hippocampus, superior temporal gyrus, and anterior parietal cortex common to both patient groups may represent the vulnerability to schizophrenia, while volume loss of the prefrontal cortex, posterior parietal cortex, cingulate, insula, and fusiform cortex preferentially observed in schizophrenia may be critical for overt manifestation of psychosis (Dr. Suzuki).

Chronic phencyclidine treatment increases dendritic spine density in prefrontal cortex and nucleus accumbens neurons

We examined whether repeated exposure to the noncompetitive NMDA receptor antagonist phencyclidine (PCP) produces enduring changes in dendritic structure in a manner similar to the stimulants cocaine and amphetamine. Adult rats were treated with i.p. injections of PCP (5 mg/kg) or saline, twice a day, for 5 consecutive days, for a total of 4 weeks. One month after the last injection, their brains were removed and processed for Golgi-Cox staining. Prior exposure to PCP increased dendritic spine density in the mPFC and NAcc core, but not in the parietal cortex. These findings, which are similar to those observed after chronic treatment with cocaine and amphetamine, raise the possibility that, despite differences in their mechanisms of action, PCP and stimulant drugs may induce some of their enduring effects via common processes.

Psychosis pathways converge via D2high dopamine receptors

The objective of this review is to identify a target or biomarker of altered neurochemical sensitivity that is common to the many animal models of human psychoses associated with street drugs, brain injury, steroid use, birth injury, and gene alterations. Psychosis in humans can be caused by amphetamine, phencyclidine, steroids, ethanol, and brain lesions such as hippocampal, cortical, and entorhinal lesions. Strikingly, all of these drugs and lesions in rats lead to dopamine supersensitivity and increase the high-affinity states of dopamine D2 receptors, or D2High, by 200-400% in striata. Similar supersensitivity and D2High elevations occur in rats born by Caesarian section and in rats treated with corticosterone or antipsychotics such as reserpine, risperidone, haloperidol, olanzapine, quetiapine, and clozapine, with the latter two inducing elevated D2High states less than that caused by haloperidol or olanzapine. Mice born with gene knockouts of some possible schizophrenia susceptibility genes are dopamine supersensitive, and their striata reveal markedly elevated D2High states; suchgenes include dopamine-beta-hydroxylase, dopamine D4 receptors, G protein receptor kinase 6, tyrosine hydroxylase, catechol-O-methyltransferase, the trace amine-1 receptor, regulator of G protein signaling RGS9, and the RIIbeta form of cAMP-dependent protein kinase (PKA). Striata from mice that are not dopamine supersensitive did not reveal elevated D2High states; these include mice with knockouts of adenosine A2A receptors, glycogen synthase kinase GSK3beta, metabotropic glutamate receptor 5, dopamine D1 or D3 receptors, histamine H1, H2, or H3 receptors, and rats treated with ketanserin or aD1 antagonist. The evidence suggests that there are multiple pathways that convergetoelevate the D2High state in brain regions and that this elevation may elicit psychosis. This proposition is supported by the dopamine supersensitivity that is a common feature of schizophrenia and that also occurs in many types of genetically altered, drug-altered, and lesion-altered animals. Dopamine supersensitivity, in turn, correlates with D2High states. The finding that all antipsychotics, traditional and recent ones, act on D2High dopamine receptors further supports the proposition.

Ontogeny of the adrenal response to (+)-methamphetamine in neonatal rats: the effect of prior drug exposure

We examined the ontogeny of the corticosterone response to (+)-methamphetamine in neonatal rats. In experiment-1, animals were injected with 10 mg/kg of (+)-methamphetamine or saline and plasma corticosterone levels were examined in separate groups 30 or 105 min later on postnatal day (P) 1, 3, 5, 7, 9, 11, 13, 15, 17, or 19. The adrenal response to methamphetamine was best described by a U-shaped function with the nadir of corticosterone release occurring between P7 and P13. Experiment-2 was similar except that the effect of four consecutive days of exposure to (+)-methamphetamine (four times daily at 2 h intervals with 10 mg/kg) was assessed with a single final dose early on the fifth day (i.e. P1-5, 3-7, 5-9, 7-11, 9-13, 11-15, 13-17, 15-19). The 30 min corticosterone response after multiple methamphetamine doses was augmented compared to single exposures, with the exception of the two earliest dosing intervals ending on P5 and P7, where the responses were lower. In addition, at 105 min, the levels of corticosterone were attenuated relative to a single drug administration. With the exception of animals receiving methamphetamine from P15 to P19, thymus weights were unaffected. The data demonstrate that (+)-methamphetamine is a robust activator of corticosterone release in developing animals and this release is extensively modified by age and previous drug exposure.

A 200-kb region of human chromosome 22q11.2 confers antipsychotic-responsive behavioral abnormalities in mice

Human chromosome 22q11.2 has been implicated in various behavioral abnormalities, including schizophrenia and other neuropsychiatric/behavioral disorders. However, the specific genes within 22q11.2 that contribute to these disorders are still poorly understood. Here, we show that an approximately 200-kb segment of human 22q11.2 causes specific behavioral abnormalities in mice. Mice that overexpress an approximately 200-kb region of human 22q11.2, containing CDCrel, GP1Bbeta, TBX1, and WDR14, exhibited spontaneous sensitization of hyperactivity and a lack of habituation. These effects were ameliorated by antipsychotic drugs. The transgenic mice were also impaired in nesting behavior. Although Tbx1 has been shown to be responsible for many physical defects associated with 22q11.2 haploinsufficiency, Tbx1 heterozygous mice did not display these behavioral abnormalities. Our results show that the approximately 200-kb region of 22q11.2 contains a gene(s) responsible for behavioral abnormalities and suggest that distinct genetic components within 22q11.2 mediate physical and behavioral abnormalities.

Psychostimulants, madness, memory... and RGS proteins?

The ingestion of psychostimulant drugs by humans imparts a profound sense of alertness and well-being. However, repeated use of these drugs in some individuals will induce a physiological state of dependence, characterized by compulsive behavior directed toward the acquisition and ingestion of the drug, at the expense of customary social obligations. Drugs of abuse and many other types of experiences share the ability to alter the morphology and density of neuronal dendrites and spines. Dopaminergic modulation of corticostriatal synaptic plasticity is necessary for these morphological changes. Changes in the density of dendritic spines on striatal neurons may underlie the development of this pathological pattern of drug-seeking behavior. Identifying proteins that regulate dopaminergic signaling are of value. A family of proteins, the regulators of G protein signaling (RGS) proteins, which regulate signaling from G protein-coupled receptors, such as dopamine and glutamate, may be important in this regard. By regulating corticostriatal synaptic plasticity, RGS proteins can influence presynaptic activity, neurotransmitter release, and postsynaptic depolarization and thereby play a key role in the development of this plasticity. Pharmacological agents that modify RGS activity in humans could be efficacious in ameliorating the dependence on psychostimulant drugs.

Methamphetamine-induced neuronal apoptosis involves the activation of multiple death pathways. Review

The abuse of the illicit drug methamphetamine (METH) is a major concern because it can cause terminal degeneration and neuronal cell death in the brain. METH-induced cell death occurs via processes that resemble apoptosis. In the present review, we discuss the role of various apoptotic events in the causation of METH-induced neuronal apoptosis in vitro and in vivo. Studies using comprehensive approaches to gene expression profiling have allowed for the identification of several genes that are up-regulated or down-regulated after an apoptosis-inducing dose of the drug. Further experiments have also documented the fact that the drug can cause demise of striatal enkephalinergic neurons by cross-talks between mitochondria-, endoplasmic reticulum- and receptor-mediated apoptotic events. These neuropathological observations have also been reported in models of drug-induced neuroplastic alterations used to mimic drug addiction (Nestler, 2001).

Transcriptional and behavioral interaction between 22q11.2 orthologs modulates schizophrenia-related phenotypes in mice

Microdeletions of 22q11.2 represent one of the highest known genetic risk factors for schizophrenia. It is likely that more than one gene contributes to the marked risk associated with this locus. Two of the candidate risk genes encode the enzymes proline dehydrogenase (PRODH) and catechol-O-methyltransferase (COMT), which modulate the levels of a putative neuromodulator (L-proline) and the neurotransmitter dopamine, respectively. Mice that model the state of PRODH deficiency observed in humans with schizophrenia show increased neurotransmitter release at glutamatergic synapses as well as deficits in associative learning and response to psychomimetic drugs. Transcriptional profiling and pharmacological manipulations identified a transcriptional and behavioral interaction between the Prodh and Comt genes that is likely to represent a homeostatic response to enhanced dopaminergic signaling in the frontal cortex. This interaction modulates a number of schizophrenia-related phenotypes, providing a framework for understanding the high disease risk associated with this locus, the expression of the phenotype, or both.

Netrin receptor deficient mice exhibit functional reorganization of dopaminergic systems and do not sensitize to amphetamine

Netrins are guidance cues that play a fundamental role in organizing the developing brain. The netrin receptor, DCC (deleted in colorectal cancer), is highly expressed by dopaminergic (DA) neurons. DCC may therefore participate in the organization of DA circuitry during development and also influence DA function in the adult. Here we show that adult dcc heterozygous mice exhibit a blunted behavioral response to the indirect DA agonist amphetamine and do not develop sensitization to its effects when treated repeatedly. These behavioral alterations are associated with profound changes in DA function. In the medial prefrontal cortex, dcc heterozygotes exhibit increased tyrosine hydroxylase (TH) protein levels and dramatic increases in basal concentrations of DA and DA metabolites. In contrast, in the nucleus accumbens, dcc heterozygotes show no changes in either TH or DA levels, but exhibit decreased concentrations of DA metabolites, suggesting reduced DA activity. In addition, dcc heterozygous mice exhibit a small, but significant reduction in total number of TH-positive neurons in midbrain DA cell body regions. These results demonstrate for the first time that alterations in dcc expression lead to selective changes in DA function and, in turn, to differences in DA-related behaviors in adulthood. These findings raise the possibility that changes in dcc function early in life are implicated in the development of DA dysregulation observed in certain psychiatric disorders, such as schizophrenia, or following chronic use of drugs of abuse.

Sensitivity to psychostimulants in mice bred for high and low stimulation to methamphetamine

Methamphetamine (MA) and cocaine induce behavioral effects primarily through modulation of dopamine neurotransmission. However, the genetic regulation of sensitivity to these two drugs may be similar or disparate. Using selective breeding, lines of mice were produced with extreme sensitivity (high MA activation; HMACT) and insensitivity (low MA activation; LMACT) to the locomotor stimulant effects of acute MA treatment. Studies were performed to determine whether there is pleiotropic genetic influence on sensitivity to the locomotor stimulant effect of MA and to other MA- and cocaine-related behaviors. The HMACT line exhibited more locomotor stimulation in response to several doses of MA and cocaine, compared to the LMACT line. Both lines exhibited locomotor sensitization to 2 mg/kg of MA and 10 mg/kg of cocaine; the magnitude of sensitization was similar in the two lines. However, the lines differed in the magnitude of sensitization to a 1 mg/kg dose of MA, a dose that did not produce a ceiling effect that may confound interpretation of studies using higher doses. The LMACT line consumed more MA and cocaine in a two-bottle choice drinking paradigm; the lines consumed similar amounts of saccharin and quinine, although the HMACT line exhibited slightly elevated preference for a low concentration of saccharin. These results suggest that some genes that influence sensitivity to the acute locomotor stimulant effect of MA have a pleiotropic influence on the magnitude of behavioral sensitization to MA and sensitivity to the stimulant effects of cocaine. Further, extreme sensitivity to MA may protect against MA and cocaine self-administration.