Neuronal activation of nucleus accumbens by local methamphetamine administration induces cognitive impairment through microglial inflammation in mice.

More than half of methamphetamine (METH) users present with cognitive impairment, making it difficult for them to reintegrate into society. However, the mechanisms of METH-induced cognitive impairment remain unclear. METH causes neuronal hyperactivation in the nucleus accumbens (NAc) by aberrantly releasing dopamine, which triggers dependence. In this study, to clarify the involvement of hyperactivation of NAc in METH-induced cognitive impairment, mice were locally microinjected with METH into NAc (mice with METH (NAc)) and investigated their cognitive phenotype. Mice with METH (NAc) exhibited cognitive dysfunction in behavioral analyses and decreased long-term potentiation in the hippocampus, with NAc activation confirmed by expression of FosB, a neuronal activity marker. In the hippocampus of mice with METH (NAc), activated microglia, but not astroglia, and upregulated microglia-related genes, Il1b and C1qa were observed. Finally, administration of minocycline, a tetracycline antibiotic with suppressive effect on microglial activation, to mice with METH (NAc) ameliorated cognitive impairment and synaptic dysfunction by suppressing the increased expression of Il1b and C1qa in the hippocampus. In conclusion, activation of NAc by injection of METH into NAc elicited cognitive impairment by facilitating immune activation in mice. This study suggests that immunological intervention could be a therapeutic strategy for addiction-related cognitive disturbances.

Cannabinoid Type 1 Receptors in the Basolateral Amygdala Regulate ACPA-Induced Place Preference and Anxiolytic-Like Behaviors.

The number of cannabis users is increasing in the world. However, the mechanisms involved in the psychiatric effects and addiction formation remain unclear. Medical treatments against cannabis addiction have not yet been established. Δ9-Tetrahydrocannabinol (THC), the main active substance in cannabis, binds and affects cannabinoid type 1 receptors (CB1R) in the brain. The mice were intraperitoneally (i.p.) administered arachidonylcyclopropylamide (ACPA), a CB1R-selective agonist, and then two behavioral experiments on anxiety and addiction were performed. Administration of ACPA caused anxiolytic-like behavior in the elevated plus maze test. In addition, ACPA increased place preference in a conditioned place preference (CPP) test. The basolateral amygdala (BLA), which is the focus of this study, is involved in anxiety-like behavior and reward and is reported to express high levels of CB1R. We aimed to reveal the role of CB1R in BLA for ACPA-induced behavior. AM251, a CB1R selective antagonist, was administered intra-BLA before i.p. administration of ACPA. Intra-BLA administration of AM251 inhibited ACPA-induced anxiolytic-like behavior and place preference. These results suggest that CB1R in the BLA contributes to behavior disorders caused by the acute or chronic use of cannabis.

Knockdown of Piccolo in the Nucleus Accumbens Suppresses Methamphetamine-Induced Hyperlocomotion and Conditioned Place Preference in Mice.

Methamphetamine (METH), the most widely distributed psychostimulant, aberrantly activates the reward system in the brain to induce addictive behaviors. The presynaptic protein "Piccolo", encoded by Pclo, was identified as a METH-responsive protein with enhanced expression in the nucleus accumbens (NAc) in mice. Although the physiological and pathological significance of Piccolo has been identified in dopaminergic signaling, its role in METH-induced behavioral abnormalities and the underlying mechanisms remain unclear. To clarify such functions, mice with Piccolo knockdown in the NAc (NAc-miPiccolo mice) by local injection of an adeno-associated virus vector carrying miRNA targeting Pclo were generated and investigated. NAc-miPiccolo mice exhibited suppressed hyperlocomotion, sensitization, and conditioned place preference behavior induced by systemic administration of METH. The excessive release of dopamine in the NAc was reduced in NAc-miPiccolo mice at baseline and in response to METH. These results suggest that Piccolo in the NAc is involved in METH-induced behavioral alterations and is a candidate therapeutic target for the treatment of drug addiction.

N-Acetyl Transferase, Shati/Nat8l, in the Dorsal Hippocampus Suppresses Aging-induced Impairment of Cognitive Function in Mice.

As the elderly population rapidly increases worldwide, the onset of cognitive dysfunction is expected to increase. Although neuronal plasticity, neurogenesis, and mitochondrial dysfunction have been reported to be involved in cognitive function, the detailed mechanism of cognitive impairment accompanied by aging is poorly understood as there are many confounding factors associated with aging. Therefore, effective treatments for aging have not yet been developed, and the establishment of therapeutic strategies has not progressed accordingly. We have previously found a decline of cognitive function in the developmental stage in mice who lack the expression of Shati/Nat8l, an N-acetyl transferase However, the contribution of Shati/Nat8l to cognitive impairment in aged mice has not yet been investigated. In this study, we aimed to investigate the role of Shati/Nat8l in cognitive function during aging. We observed a reduction in Shati/Nat8l mRNA expression in the dorsal hippocampus of mice as a result of their aging. Moreover, the cognitive dysfunction observed in aged mice was reversed by Shati/Nat8l overexpression in the dorsal hippocampus. Shati/Nat8l overexpression in the dorsal hippocampus of mice did not alter the expression of neurotrophic factors or mitochondrial function-related genes, including Bdnf or Pgc-1α, which are suggested to be downstream genes of Shati/Nat8l. Decreased N-acetyl aspartate (NAA) in aged mice was upregulated by Shati/Nat8l overexpression, suggesting that the Shati/Nat8l-NAA pathway determines cognitive function with aging. Taken together, Shati/Nat8l and NAA in the dorsal hippocampus may be novel targets for the treatment of cognitive impairment.

Shati/Nat8l Overexpression Improves Cognitive Decline by Upregulating Neuronal Trophic Factor in Alzheimer's Disease Model Mice.

Alzheimer's disease (AD) is a type of dementia characterized by the deposition of amyloid ß, a causative protein of AD, in the brain. Shati/Nat8l, identified as a psychiatric disease related molecule, is a responsive enzyme of N-acetylaspartate (NAA) synthesis. In the hippocampi of AD patients and model mice, the NAA content and Shati/Nat8l expression were reported to be reduced. Having recently clarified the involvement of Shati/Nat8l in cognitive function, we examined the recovery effect of the hippocampal overexpression of Shati/Nat8l in AD model mice (5XFAD). Shati/Nat8l overexpression suppressed cognitive dysfunction without affecting the Aß burden or number of NeuN-positive neurons. In addition, brain-derived neurotrophic factor mRNA was upregulated by Shati/Nat8l overexpression in 5XFAD mice. These results suggest that Shati/Nat8l overexpression prevents cognitive dysfunction in 5XFAD mice, indicating that Shati/Nat8l could be a therapeutic target for AD.

Shati/Nat8l deficiency disrupts adult neurogenesis and causes attentional impairment through dopaminergic neuronal dysfunction in the dentate gyrus.

Successful completion of daily activities relies on the ability to select the relevant features of the environment for memory and recall. Disruption to these processes can lead to various disorders, such as attention-deficit hyperactivity disorder (ADHD). Dopamine is a neurotransmitter implicated in the regulation of several processes, including attention. In addition to the higher-order brain function, dopamine is implicated in the regulation of adult neurogenesis. Previously, we generated mice lacking Shati, an N-acetyltransferase-8-like protein on a C57BL/6J genetic background (Shati/Nat8l-/- ). These mice showed a series of changes in the dopamine system and ADHD-like behavioral phenotypes. Therefore, we hypothesized that deficiency of Shati/Nat8l would affect neurogenesis and attentional behavior in mice. We found aberrant morphology of neurons and impaired neurogenesis in the dentate gyrus of Shati/Nat8l-/- mice. Additionally, research has suggested that impaired neurogenesis might be because of the reduction of dopamine in the hippocampus. Galantamine (GAL) attenuated the attentional impairment observed in the object-based attention test via increasing the dopamine release in the hippocampus of Shati/Nat8l-/- mice. The α7 nicotinic acetylcholine receptor antagonist, methyllycaconitine, and dopamine D1 receptor antagonist, SCH23390, blocked the ameliorating effect of GAL on attentional impairment in Shati/Nat8l-/- mice. These results suggest that the ameliorating effect of GAL on Shati/Nat8l-/- attentional impairment is associated with activation of D1 receptors following increased dopamine release in the hippocampus via α7 nicotinic acetylcholine receptor. In summary, Shati/Nat8l is important in both morphogenesis and neurogenesis in the dentate gyrus and attention, possible via modulation of dopaminergic transmission. Cover Image for this issue: https://doi.org/10.1111/jnc.15061.

N-acetylaspartate availability is essential for juvenile survival on fat-free diet and determines metabolic health.

N-acetylaspartate (NAA) is synthesized by aspartate N-acetyltransferase (gene: Nat8l) from acetyl-coenzyme A and aspartate. In the brain, NAA is considered an important energy metabolite for lipid synthesis. However, the role of NAA in peripheral tissues remained elusive. Therefore, we characterized the metabolic phenotype of knockout (ko) and adipose tissue-specific (ako) Nat8l-ko mice as well as NAA-supplemented mice on various diets. We identified an important role of NAA availability in the brain during adolescence, as 75% of Nat8l-ko mice died on fat-free diet (FFD) after weaning but could be rescued by NAA supplementation. In adult life, NAA deficiency promotes a beneficial metabolic phenotype, as Nat8l-ko and Nat8l-ako mice showed reduced body weight, increased energy expenditure, and improved glucose tolerance on chow, high-fat, and FFDs. Furthermore, Nat8l-deficient adipocytes exhibited increased mitochondrial respiration, ATP synthesis, and an induction of browning. Conversely, NAA-treated wild-type mice showed reduced adipocyte respiration and lipolysis and increased de novo lipogenesis, culminating in reduced energy expenditure, glucose tolerance, and insulin sensitivity. Mechanistically, our data point to a possible role of NAA as modulator of pancreatic insulin secretion and suggest NAA as a critical energy metabolite for adipocyte and whole-body energy homeostasis.-Hofer, D. C., Zirkovits, G., Pelzmann, H. J., Huber, K., Pessentheiner, A. R., Xia, W., Uno, K., Miyazaki, T., Kon, K., Tsuneki, H., Pendl, T., Al Zoughbi, W., Madreiter-Sokolowski, C. T., Trausinger, G., Abdellatif, M., Schoiswohl, G., Schreiber, R., Eisenberg, T., Magnes, C., Sedej, S., Eckhardt, M., Sasahara, M., Sasaoka, T., Nitta, A., Hoefler, G., Graier, W. F., Kratky, D., Auwerx, J., Bogner-Strauss, J. G. N-acetylaspartate availability is essential for juvenile survival on fat-free diet and determines metabolic health.

Investigating DNA Methylation of SHATI/NAT8L Promoter Sites in Blood of Unmedicated Patients with Major Depressive Disorder.

Major depressive disorder (MDD) is one of the most common psychiatric diseases. However, early detection and diagnosis of MDD is difficult, largely because there is no known biomarker or objective diagnostic examination, and its diagnosis is instead based on a clinical interview. The aim of this study was to develop a novel diagnostic tool using DNA methylation as a blood biomarker. We sought to determine whether unmedicated patients with MDD showed significant differences in DNA methylation in the promoter region of the SHATI/N-acetyltransferase 8 like (SHATI/NAT8L) gene compared to healthy controls. Sixty participants with MDD were recruited from all over Japan. They were diagnosed and assessed by at least two trained psychiatrists according to DSM-5 criteria. DNA was extracted from peripheral blood. We then assessed DNA methylation of the SHATI/NAT8L promoter regions in patients with MDD by pyrosequencing. Methylation levels of the SHATI/NAT8L promoter region at CpG sites in peripheral blood from unmedicated patients were significantly higher than in healthy controls. In contrast, medicated patients with MDD showed significantly lower methylation levels in the same region compared to healthy controls. Since previous studies of DNA methylation in MDD only assessed medicated patients, the methylation status of the SHATI/NAT8L promoter region in unmedicated patients presented herein may prove useful for the diagnosis of MDD. To our knowledge, this is the first attempt to measure methylation of the SHATI/NAT8L gene in drug-naïve patients with psychiatric diseases. Based on our findings, methylation of SHATI/NAT8L DNA might be a diagnostic biomarker of MDD.

Inhibitory effects of Shati/Nat8l overexpression in the medial prefrontal cortex on methamphetamine-induced conditioned place preference in mice.

Shati/Nat8l is a novel N-acetyltransferase identified in the brain of mice treated with methamphetamine (METH). Shati/Nat8l mRNA is expressed in various brain areas, including the prefrontal cortex (PFC), where the expression level is higher than that in other brain regions. Shati/Nat8l overexpression in the nucleus accumbens (NAc) attenuates the pharmacological response to METH via mGluR3. Meanwhile, dopamine (DA) and glutamate dysregulations have been reported in the medial prefrontal cortex (mPFC) and NAc after METH self-administration and during reinstatement. However, the mechanism, the reward system, and function of Shati/Nat8l in the mPFC is unclear. Here, we injected an adeno-associated virus (AAV) vector containing Shati/Nat8l into the mPFC of mice, to overexpress Shati/Nat8l in the mPFC (mPFC-Shati/Nat8l). Interestingly, the METH-induced conditioned place preference (CPP) was attenuated in the mPFC-Shati/Nat8l mice, but locomotor activity was not. Additionally, immunohistochemical results from mice that were injected with AAV-GFP showed fluorescence in the mPFC and other brain regions, mainly the NAc, indicating an mPFC-NAc top-down connection. Finally, in vivo microdialysis experiments revealed that Shati/Nat8l overexpression in the mPFC reduced extracellular DA levels and suppressed the METH-induced DA increase in the NAc. Moreover, decreased extracellular glutamate levels were observed in the NAc. These results indicate that Shati/Nat8l overexpression in the mPFC attenuates METH-induced CPP by decreasing extracellular DA in the NAc. In contrast, Shati/Nat8l-mPFC overexpression did not alter METH-induced hyperlocomotion. This study demonstrates that Shati/Nat8l in the mPFC attenuates METH reward-seeking behaviour but not the psychomotor activity of METH.

Striatal N-Acetylaspartate Synthetase Shati/Nat8l Regulates Depression-Like Behaviors via mGluR3-Mediated Serotonergic Suppression in Mice.

Background: Several clinical studies have suggested that N-acetylaspartate and N-acetylaspartylglutamate levels in the human brain are associated with various psychiatric disorders, including major depressive disorder. We have previously identified Shati/Nat8l, an N-acetyltransferase, in the brain using an animal model of psychosis. Shati/Nat8l synthesizes N-acetylaspartate from L-aspartate and acetyl-coenzyme A. Further, N-acetylaspartate is converted into N-acetylaspartylglutamate, a neurotransmitter for metabotropic glutamate receptor 3. Methods: Because Shati/Nat8l mRNA levels were increased in the dorsal striatum of mice following the exposure to forced swimming stress, Shati/Nat8l was overexpressed in mice by the microinjection of adeno-associated virus vectors containing Shati/Nat8l gene into the dorsal striatum (dS-Shati/Nat8l mice). The dS-Shati/Nat8l mice were further assessed using behavioral and neurochemical tests. Results: The dS-Shati/Nat8l mice exhibited behavioral despair in the forced swimming and tail suspension tests and social withdrawal in the 3-chamber social interaction test. These depression-like behaviors were attenuated by the administration of a metabotropic glutamate receptor 2/3 antagonist and a selective serotonin reuptake inhibitor. Furthermore, the metabolism of N-acetylaspartate to N-acetylaspartylglutamate was decreased in the dorsal striatum of the dS-Shati/Nat8l mice. This finding corresponded with the increased expression of glutamate carboxypeptidase II, an enzyme that metabolizes N-acetylaspartylglutamate present in the extracellular space. Extracellular serotonin levels were lower in the dorsal striatum of the dS-Shati/Nat8l and normal mice that were repeatedly administered a selective glutamate carboxypeptidase II inhibitor. Conclusions: Our findings indicate that the striatal expression of N-acetylaspartate synthetase Shati/Nat8l plays a role in major depressive disorder via the metabotropic glutamate receptor 3-mediated functional control of the serotonergic neuronal system.

Pubertal administration of antiserum against nerve growth factor regresses renal vascular remodeling in spontaneously hypertensive rats.

To investigate the role of nerve growth factor (NGF) in the development of hypertensive renal vascular remodeling, antiserum against NGF (anti-NGF) or vehicle was injected at 3 weeks of age in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats (n = 9 for each treatment in each strain). Flow-pressure (F-P) and pressure-glomerular filtration rate (P-GFR) relationships at vasodilated perfused kidneys were determined at 10 weeks of age. In the vehicle rats, blood pressure, renal noradrenaline content, the gradient of F-P (minimal vascular resistance at pre- and post-glomerular vasculature) and the X-intercept of P-GFR (preglomerular : postglomerular vascular resistance ratio) were greater in SHR than in WKY rats, although the gradient of P-GFR (glomerular filtration capacity) did not differ significantly between the strains. Blood pressure and renal noradrenaline content were lower in SHR receiving anti-NGF than in SHR receiving vehicle, although such difference was not observed in WKY rats. The gradient of F-P was less but the gradient of P-GFR was greater in SHR receiving anti-NGF compared with SHR receiving vehicle, although the similar differences did not occur in WKY rats. Blood pressure and renal noradrenaline content remained greater in SHR treated with anti-NGF compared with WKY rats treated with vehicle; however, the gradient of F-P did not differ significantly between them. Contrary, anti-NGF did not affect the X-intercept of P-GFR in either strain. In conclusion, NGF could contribute to the genesis of renal vascular remodeling, at least in part, through modification of renal sympathetic activity and blood pressure in SHR.

NAT8L (N-acetyltransferase 8-like) accelerates lipid turnover and increases energy expenditure in brown adipocytes.

NAT8L (N-acetyltransferase 8-like) catalyzes the formation of N-acetylaspartate (NAA) from acetyl-CoA and aspartate. In the brain, NAA delivers the acetate moiety for synthesis of acetyl-CoA that is further used for fatty acid generation. However, its function in other tissues remained elusive. Here, we show for the first time that Nat8l is highly expressed in adipose tissues and murine and human adipogenic cell lines and is localized in the mitochondria of brown adipocytes. Stable overexpression of Nat8l in immortalized brown adipogenic cells strongly increases glucose incorporation into neutral lipids, accompanied by increased lipolysis, indicating an accelerated lipid turnover. Additionally, mitochondrial mass and number as well as oxygen consumption are elevated upon Nat8l overexpression. Concordantly, expression levels of brown marker genes, such as Prdm16, Cidea, Pgc1α, Pparα, and particularly UCP1, are markedly elevated in these cells. Treatment with a PPARα antagonist indicates that the increase in UCP1 expression and oxygen consumption is PPARα-dependent. Nat8l knockdown in brown adipocytes has no impact on cellular triglyceride content, lipogenesis, or oxygen consumption, but lipolysis and brown marker gene expression are increased; the latter is also observed in BAT of Nat8l-KO mice. Interestingly, the expression of ATP-citrate lyase is increased in Nat8l-silenced adipocytes and BAT of Nat8l-KO mice, indicating a compensatory mechanism to sustain the acetyl-CoA pool once Nat8l levels are reduced. Taken together, our data show that Nat8l impacts on the brown adipogenic phenotype and suggests the existence of the NAT8L-driven NAA metabolism as a novel pathway to provide cytosolic acetyl-CoA for lipid synthesis in adipocytes.

Knockdown of dopamine D2 receptors in the nucleus accumbens core suppresses methamphetamine-induced behaviors and signal transduction in mice.

BACKGROUND: Addictive drugs lead to reinforcing properties by increasing dopamine in the nucleus accumbens, which is composed of a core and shell regions. Neurons in the nucleus accumbens are divided into 2 subtypes based on the differential gene expression of the dopamine D1 receptors and D2 receptors. METHODS: In the present study, we investigated the role of D2 receptors in the nucleus accumbens core in behaviors and signal transduction induced by psychostimulant methamphetamine in mice that were microinjected with adeno-associated virus vectors containing a microRNA (miRNA) sequence for D2 receptor (adeno-associated virus-miD2r vectors) in the nucleus accumbens core. The adeno-associated virus vectors containing a miRNA sequence for D2 receptor-treated mice (miD2r mice) were assessed at a reduction in D2 receptor, but at no change in dopamine D1 receptor, in the nucleus accumbens core compared with the adeno-associated virus-Mock vectors-treated mice (Mock mice). RESULTS: miD2r mice exhibited a reduction in hyperlocomotion that was induced by a single treatment with methamphetamine. The development of locomotor sensitization induced by repeated treatment with methamphetamine exhibited less extension in miD2r mice. In a place conditioning paradigm, the preferred effects of methamphetamine were significantly weaker in miD2r mice than in Mock mice. Furthermore, the single treatment with methamphetamine-induced phosphorylation of extracellular signal regulated kinase and cyclic adenosine monophosphate response element-binding protein in the nucleus accumbens core of miD2r mice was decreased compared with that in Mock mice. Repeated treatment with methamphetamine-induced delta FBJ murine osteosarcoma viral oncogene homolog B accumulation in the nucleus accumbens core of miD2r mice was also attenuated. CONCLUSIONS: These findings suggest that a D2 receptor-mediated neuronal pathway from the nucleus accumbens core plays an inhibitory role in the development of reinforcing properties.

Overexpression of Shati/Nat8l, an N-acetyltransferase, in the nucleus accumbens attenuates the response to methamphetamine via activation of group II mGluRs in mice.

A novel N-acetyltransferase, Shati/Nat8l, was identified in the nucleus accumbens (NAc) of mice with methamphetamine (METH) treatment. Previously we reported that suppression of Shati/Nat8l enhanced METH-induced behavioral alterations via dopaminergic neuronal regulation. However, the physiological mechanisms of Shati/Nat8l on the dopaminergic system in the brain are unclear. In this study, we injected adeno-associated virus (AAV) vector containing Shati/Nat8l into the NAc or dorsal striatum (dS) of mice, to increase Shati/Nat8l expression. Overexpression of Shati/Nat8l in the NAc, but not in the dS, attenuated METH-induced hyperlocomotion, locomotor sensitization, and conditioned place preference in mice. Moreover, the Shati/Nat8l overexpression in the NAc attenuated the elevation of extracellular dopamine levels induced by METH in in vivo microdialysis experiments. These behavioral and neurochemical alterations due to Shati/Nat8l overexpression in the NAc were inhibited by treatment with selective group II metabotropic glutamate receptor type 2 and 3 (mGluR2/3) antagonist LY341495. In the AAV vector-injected NAc, the tissue contents of both N-acetylaspartate and N-acetylaspartylglutamate (NAAG), endogenous mGluR3 agonist, were elevated. The injection of peptidase inhibitor of NAAG or the perfusion of NAAG itself reduced the basal levels of extracellular dopamine in the NAc of naive mice. These results indicate that Shati/Nat8l in the NAc, but not in the dS, plays an important suppressive role in the behavioral responses to METH by controlling the dopaminergic system via activation of group II mGluRs.

Deletion of SHATI/NAT8L increases dopamine D1 receptor on the cell surface in the nucleus accumbens, accelerating methamphetamine dependence.

In a previous report, we identified a novel molecule, SHATI/NAT8L, having an inhibitory effect on methamphetamine (METH)-induced hyperlocomotion, sensitization, and conditioned place preference (CPP). SHATI/NAT8L attenuates the METH-induced increase in dopamine overflow in the nucleus accumbens (NAc) by promoting plasmalemmal and vesicular dopamine uptake. However, the biological functions of the protein remain unclear. In this study, we explored NAT8L-binding proteins using pull-down assays and identified a number of components of the adaptor protein (AP)-2 complex, which is a multimeric protein localized to the plasma membrane that functions to internalize cargo during clathrin-mediated endocytosis. To investigate whether NAT8L regulates the receptor localization to the cell surface, cell-surface dopamine D1 receptor in the NAc of Nat8l knockout (KO) mice was quantified. We found that dopamine D1 receptor on the cell surface was increased in the NAc of Nat8l KO mice compared with the wild type (WT) animals. Consistent with this finding, Nat8l KO mice showed higher basal locomotor activity and heightened sensitivity to D1 agonist compared with WT mice. In addition, METH-induced sensitization and CPP were enhanced in Nat8l KO mice. These results suggest that NAT8L might regulate the localization of cell-surface dopamine D1 receptor, thereby controlling basal behaviour and sensitivity to METH. Furthermore, we observed a single nucleotide polymorphism (SNP) in the human NAT8L gene related to reward dependence, a personality trait, and grey matter volume in the caudate nucleus in healthy subjects, suggesting that NAT8L might also affect human personality.

Behavioral phenotypes for negative symptoms in animal models of schizophrenia.

A devastating psychiatric disorder, schizophrenia is characterized by three major symptoms, positive and negative symptoms and cognitive deficit. Almost all current therapeutic drugs for schizophrenia have efficacy for positive symptoms, and weak efficacy for negative and cognitive deficit. In particular, social withdrawal, diminished motivation, and anhedonia as the depressive aspects of negative symptoms are resistant to the treatment of antipsychotic drugs. Therefore, there is a need for development of new therapeutic drugs for negative symptoms of schizophrenia, and it is necessary to have comprehensive animal models to understand the neurobiological foundations of their symptoms. In this review, we represent the behavioral phenotypes in available animal models of schizophrenia for drug discovery, focusing on the depressive aspects of negative symptoms. We mention here animal models based on the pathology and epidemiology of schizophrenia, e.g., the pharmacological, neurodevelopmental, genetic, and gene-environment combination models. The animal models of schizophrenia are developed by various approaches and are assessed, but there are few models demonstrating negative symptoms with sensitivities to available therapeutic drugs. The development of comprehensive animal model reflecting negative symptoms and of novel compounds that can remedy them provide certain insight into the neurobiological process of schizophrenia and also point the way to a new therapeutic strategy.

SHATI/NAT8L regulates neurite outgrowth via microtubule stabilization.

We previously identified a new molecule, "SHATI/NAT8L," which has an inhibitory effect on methamphetamine (METH)-induced hyperlocomotion, sensitization, and conditioned place preference. Nevertheless, the extent of SHATI localization and its functions are only partially understood. In this study, we used the FLAG-tag method to investigate SHATI localization. We found that SHATI was localized to microtubules when expressed in COS7 cells and cortical primary neurons. This distribution of SHATI was less apparent after cells were treated with colchicine, a tubulin polymerization inhibitor that disrupts the microtubule structure. This finding suggests that SHATI is associated with microtubule structure. Interestingly, overexpression of SHATI in COS7 cells could attenuate the colchicine-induced decrease in acetylated microtubules, indicating that SHATI plays a role in stabilizing microtubules. Furthermore, we showed that Shati deletion impaired neurite elongation. In cortical primary neurons, neurite length and complexity in Shati-knockout (KO) mice were significantly decreased. In pyramidal neurons in the prefrontal cortex, dendrite length and complexity were also significantly decreased in Shati-KO mice compared with wild-type mice. These results suggest a novel function for SHATI, which may be a new member of the microtubule-associated protein family.

Intrastriatal gene delivery of GDNF persistently attenuates methamphetamine self-administration and relapse in mice.

Relapse of drug abuse after abstinence is a major challenge to the treatment of addicts. In our well-established mouse models of methamphetamine (Meth) self-administration and reinstatement, bilateral microinjection of adeno-associated virus vectors expressing GDNF (AAV-Gdnf) into the striatum significantly reduced Meth self-administration, without affecting locomotor activity. Moreover, the intrastriatal AAV-Gdnf attenuated cue-induced reinstatement of Meth-seeking behaviour in a sustainable manner. In addition, this manipulation showed that Meth-primed reinstatement of Meth-seeking behaviour was reduced. These findings suggest that the AAV vector-mediated Gdnf gene transfer into the striatum is an effective and sustainable approach to attenuate Meth self-administration and Meth-associated cue-induced relapsing behaviour and that the AAV-mediated Gdnf gene transfer in the brain may be a valuable gene therapy against drug dependence and protracted relapse in clinical settings.

[The role of a molecule associated with drug dependence, shati/nat8l].

Various molecules are involved in drug addiction induced by drugs of abuse. Therefore, the mechanism of drug addiction is still not clear, and it has been a difficulty in the development of preventive and curative drugs for drug dependence. We tried to identify the molecules associated with drug dependence, and found three molecules including shati/nat81. Recently, it has been demonstrated that the substrate for shati/nat81 is aspaltate and shati/nat8l biosynthesizes N-acetylaspartate, which exists abundantly in the mammalian brain. In this study, we investigated the physiological function of shati/nat81 and the role of shati/nat81 in drug dependence. The overexpression of shati/nat81 in the dorsal striatum of mice led to social abnormality and depression-like behavior, and worsened a part of the motor dysfunction induced by Ca2+ channel agonist BAY-K 8644. The overexpression of shati/nat81 in the nucleus accumbens of mice inhibited methamphetamine-induced behavioral and biochemical abnormalities. These findings suggest that the shati/nat81-associated system could play a role in the regulation of mental activity and motor action, and be a new target in the development of therapeutic drugs for drug dependence.

Sleep disturbance after cessation of cannabis administration in mice.

Cannabis withdrawal syndrome (CWS) in humans is characterized by various somatic symptoms, including sleep disturbances. In the present study, we investigated sleep alterations in mice after the cessation of arachidonylcyclopropylamide (ACPA), a cannabinoid type 1 receptor agonist, administration. ACPA-administered mice (ACPA mice) displayed an increased number of rearings after the cessation of ACPA administration compared to saline-administered mice (Saline mice). Moreover, the number of rubbings was also decreased in ACPA mice compared with those of the control mice. Electroencephalography (EEG) and electromyography (EMG) were measured for 3 days after the cessation of ACPA administration. During ACPA administration, there was no difference in the relative amounts of total sleep and wake time between ACPA and Saline mice. However, ACPA-induced withdrawal decreased total sleep time during the light period in ACPA mice after ACPA cessation. These results suggest that ACPA cessation induces sleep disturbances in the mouse model of CWS.