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Schizophrenia (SCZ) is a severe psychiatric disorder characterized by positive symptoms, negative symptoms, and cognitive deficits. Current antipsychotic treatment in SCZ improves positive symptoms but has major side effects and little impact on negative symptoms and cognitive impairment. The pathoetiology of SCZ remains unclear, but is known to involve small GTPase signaling. Rho kinase, an effector of small GTPase Rho, is highly expressed in the brain and plays a major role in neurite elongation and neuronal architecture. This study used a touchscreen-based visual discrimination (VD) task to investigate the effects of Rho kinase inhibitors on cognitive impairment in a methamphetamine (METH)–treated male mouse model of SCZ. Systemic injection of the Rho kinase inhibitor fasudil dose-dependently ameliorated METH-induced VD impairment. Fasudil also significantly suppressed the increase in the number of c-Fos–positive cells in the infralimbic medial prefrontal cortex (infralimbic mPFC) and dorsomedial striatum (DMS) following METH treatment. Bilateral microinjections of Y-27632, another Rho kinase inhibitor, into the infralimbic mPFC or DMS significantly ameliorated METH-induced VD impairment. Two proteins downstream of Rho kinase, myosin phosphatase-targeting subunit 1 (MYPT1; Thr696) and myosin light chain kinase 2 (MLC2; Thr18/Ser19), exhibited increased phosphorylation in the infralimbic mPFC and DMS, respectively, after METH treatment, and fasudil inhibited these increases. Oral administration of haloperidol and fasudil ameliorated METH-induced VD impairment, while clozapine had little effect. Oral administration of haloperidol and clozapine suppressed METH-induced hyperactivity, but fasudil had no effect. These results suggest that METH activates Rho kinase in the infralimbic mPFC and DMS, which leads to cognitive impairment in male mice. Rho kinase inhibitors ameliorate METH-induced cognitive impairment, perhaps via the cortico-striatal circuit.

We examined whether galantamine (GAL), a cholinesterase inhibitor and allosteric potentiating ligand for α7 nicotinic acetylcholine receptor (nAChR), had an impact on emotional abnormalities in forebrain-specific cholecystokinin receptor-2 overexpressed transgenic mice. Treatment with GAL (1 mg/kg, s.c.) attenuated the decrease of social interaction time, but failed to attenuate anxiety-like behavior in the elevated plus-maze test. The effect of GAL was blocked by an α7 nAChR antagonist, methyllycaconitine (3 mg/kg, i.p.). These results suggest that GAL improved social interaction impairments via α7 nAChR and could be useful to treat sociability-related emotional abnormalities.

GABAA receptors containing α6 subunits (α6GABAARs) in the cerebellum have -been implicated in schizophrenia. It was reported that the GABA synthesizing enzymes were downregulated whereas α6GABAARs were upregulated in postmortem cerebellar tissues of patients with schizophrenia and in a rat model induced by chronic phencyclidine (PCP). We have previously demonstrated that pyrazoloquinolinone Compound 6, an α6GABAAR-highly selective positive allosteric modulator (PAM), can rescue the disrupted prepulse inhibition (PPI) induced by methamphetamine (METH), an animal model mimicking the sensorimotor gating deficit based on the hyper-dopaminergic hypothesis of schizophrenia. Here, we demonstrate that not only Compound 6, but also its structural analogues, LAU463 and LAU159, with similarly high α6GABAAR selectivity and their respective deuterated derivatives (DK-I-56-1, DK-I-58-1 and DK-I-59-1) can rescue METH-induced PPI disruption. Besides, Compound 6 and DK-I-56-I can also rescue the PPI disruption induced by acute administration of PCP, an animal model based on the hypo-glutamatergic hypothesis of schizophrenia. Importantly, Compound 6 and DK-I-56-I, at doses not affecting spontaneous locomotor activity, can also rescue impairments of social interaction and novel object recognition in mice induced by chronic PCP treatments. At similar doses, Compound 6 did not induce sedation but significantly suppressed METH-induced hyperlocomotion. Thus, α6GABAAR-selective PAMs can rescue not only disrupted PPI but also hyperlocomotion, social withdrawal, and cognitive impairment, in both METH- and PCP-induced animal models mimicking schizophrenia, suggesting that they are a potential novel therapy for the three core symptoms, i.e. positive symptoms, negative symptoms, and cognitive impairment, of schizophrenia.

Abstract Dopamine is a key neurotransmitter that regulates attention through dopamine D1 and D2-receptors in the prefrontal cortex (PFC). We previously developed an object-based attention test (OBAT) to evaluate attention in mice. Disruption of the dopaminergic neuronal system in the PFC induced attentional impairment in the OBAT. However, previous studies have not systematically examined which specific brain regions are associated with the blockade of PFC dopamine D1 and D2-receptors in the OBAT. In this study, we investigated the association of dopamine D1 and D2-receptors in the PFC with attention and neuronal activity in diverse brain regions. We found that both dopamine D1 and D2-receptor antagonists induced attentional impairment in the OBAT by bilateral microinjection into the PFC of mice, suggesting that both dopamine D1 and D2-receptors were associated with attention in the OBAT. Our analysis of the neuronal activity as indicated by c-Fos expression in 11 different brain regions showed that based on the antagonist types, there was selective activation of several brain regions. Overall, this study suggests that both dopamine D1 and D2-receptors play a role in attention through different neuronal circuits in the PFC of mice.

Abstract We recently found a significant association between exonic copy-number variations in the Rho GTPase activating protein 10 (Arhgap10) gene and schizophrenia in Japanese patients. Special attention was paid to one patient carrying a missense variant (p.S490P) in exon 17, which overlapped with an exonic deletion in the other allele. Accordingly, we generated a mouse model (Arhgap10 S490P/NHEJ mice) carrying a missense variant and a coexisting frameshift mutation. We examined the spatiotemporal expression of Arhgap10 mRNA in the brain and found the highest expression levels in the cerebellum, striatum, and nucleus accumbens (NAc), followed by the frontal cortex in adolescent mice. The expression levels of phosphorylated myosin phosphatase-targeting subunit 1 and phosphorylated p21-activated kinases in the striatum and NAc were significantly increased in Arhgap10 S490P/NHEJ mice compared with wild-type littermates. Arhgap10 S490P/NHEJ mice exhibited a significant increase in neuronal complexity and spine density in the striatum and NAc. There was no difference in touchscreen-based visual discrimination learning between Arhgap10 S490P/NHEJ and wild-type mice, but a significant impairment of visual discrimination was evident in Arhgap10 S490P/NHEJ mice but not wild-type mice when they were treated with methamphetamine. The number of c-Fos-positive cells was significantly increased after methamphetamine treatment in the dorsomedial striatum and NAc core of Arhgap10 S490P/NHEJ mice. Taken together, these results suggested that schizophrenia-associated Arhgap10 gene mutations result in morphological abnormality of neurons in the striatum and NAc, which may be associated with vulnerability of cognition to methamphetamine treatment.

Abstract Disturbances of attention are a common behavioral feature associated with neuropsychiatric disorders with largely unknown underlying causes. We previously developed an object-based attention test (OBAT) as a simple and practical method for evaluating attention in mice. Since its establishment, the test has become a popular method for assessing attention and related underlying mechanisms in various mouse models. However, the underlying neuronal network involved in this test has yet to be studied. The purpose of this study was to identify the principal brain regions activated in the OBAT. Accordingly, C57BL/6J mice were subjected to the OBAT and thereafter prepared for immunohistochemical quantification of c-Fos, an immediate early gene that is frequently used as a marker of neuronal activity, in 13 different brain regions. The number of c-Fos-positive cells was significantly higher in the prefrontal cortex (PFC), dorsomedial striatum (DMS), and dentate gyrus (DG) in the test group as compared to the control group. The neuronal activation of these brain regions during the OBAT indicates that these brain regions are necessary for the regulation of attention in this test. This was supported by excitotoxic lesioning of these brain regions, leading to impaired attention without causing locomotor dysfunction. This study is one of the first attempts to analyze the brain regions that regulate attention in the OBAT. These findings provide an initial insight into the role of these brain regions and ideas for studying the underlying neural and molecular mechanisms.

Abstract Background Immune molecules, such as cytokines, complement, and major histocompatibility complex (MHC) proteins, in the central nervous system are often associated with neuropsychiatric disorders. Neuronal MHC class I (MHCI), such as H-2D, regulate neurite outgrowth, the establishment and function of cortical connections, and activity-dependent refinement in mice. We previously established mice expressing MHCI specifically in astrocytes of the media prefrontal cortex (mPFC) using the adeno-associated virus (AAV) vector under the control of the GfaABC1D promoter. Mice expressing the soluble form of H-2D (sH-2D) in the mPFC (sH-2D-expressing mice) showed abnormal behaviors, including social interaction deficits and cognitive dysfunctions. However, the pathophysiological significance of astroglial MHCI on higher brain functions, such as learning, memory, and behavioral flexibility, remains unclear. Therefore, cognitive function in mice expressing sH-2D in astrocytes of the mPFC was tested using the visual discrimination (VD) task. Methods sH-2D-expressing mice were subjected to the VD and reversal learning tasks, and morphological analysis. Results In the pretraining, sH-2D-expressing mice required significantly more trials to reach the learning criterion than control mice. The total number of sessions, trials, normal trials, and correction trials to reach the VD criterion were also significantly higher in sH-2D-expressing mice than in control mice. A morphological study showed that dendritic complexity and spine density were significantly reduced in the dorsal striatum of sH-2D-expressing mice. Conclusion Collectively, the present results suggest that the overexpression of astroglial MHCI in the mPFC results in impaired VD learning, which may be accompanied by decreased dendritic complexity in the dorsal striatum and mPFC.

Progranulin is an autocrine growth factor that promotes proliferation, migration, invasion, and chemoresistance of various cancer cells. These mechanisms mainly depend on the protein kinase B (Akt)/mechanistic target of rapamycin (mTOR) pathway. Recent studies have shown that patients with hematopoietic cancer have elevated serum progranulin levels. Thus, the current study aimed to investigate the role of progranulin in hematopoietic cancer cells and how it modulates their proliferation. Both knockdown of progranulin and progranulin neutralizing antibody treatment inhibited proliferation in several human hematopoietic cancer cell lines. Moreover, progranulin depletion not only decreases the phosphorylation level of the Akt/mTOR pathway but also, surprisingly, increases the expression of transforming growth factor-beta (TGF-β) and phosphorylation of mothers against decapentaplegic homolog 2 (SMAD2) in Kasumi-1 cell. Furthermore, LY2109761, an inhibitor of TGF-β receptor type I/II kinase, and TGF-β neutralizing antibody blocked the inhibition of proliferation induced by progranulin depletion. These data provide new insights that progranulin alters cell proliferation via the TGF-β axis and progranulin could be a new therapeutic target for hematopoietic cancers.

In the majority of schizophrenia patients, chronic atypical antipsychotic administration produces a significant reduction in or even complete remission of psychotic symptoms such as hallucinations and delusions. However, these drugs are not effective in improving cognitive and emotional deficits in patients with schizophrenia. Atypical antipsychotic drugs have a high affinity for the dopamine D2 receptor, and a modest affinity for the serotonin 5-HT2A receptor. The cognitive and emotional deficits in schizophrenia are thought to involve neural networks beyond the classical dopaminergic mesolimbic pathway, however, including serotonergic systems. For example, mutations in the RELN gene, which encodes Reelin, an extracellular matrix protein involved in neural development and synaptic plasticity, are associated with neurodevelopmental disorders such as schizophrenia and autism spectrum disorder. Furthermore, hippocampal Reelin levels are down-regulated in the brains of both schizophrenic patients and in rodent models of schizophrenia. In the present study, we investigated the effect of Reelin microinjection into the mouse hippocampus on behavioral phenotypes to evaluate the role of Reelin in neurodevelopmental disorders and to test a therapeutic approach that extends beyond classical monoamine targets. To model the cognitive and emotional deficits, as well as histological decreases in Reelin-positive cell numbers and hippocampal synaptoporin distribution, a synaptic vesicle protein, offspring that were prenatally exposed to maternal immune activation were used. Microinjections of recombinant Reelin protein into the hippocampus rescued impairments in object memory and anxiety-like behavior and recruited synaptoporin in the hippocampus in offspring exposed to antenatal inflammation. These results suggest that Reelin supplementation has the potential to treat cognitive and emotional impairments, as well as synaptic disturbances, in patients with neurodevelopmental disorders such as schizophrenia.

Abstract Background Polyriboinosinic-polyribocytidylic acid (polyI:C) triggers a strong innate immune response that mimics immune activation by viral infections. Induction of interferon-induced transmembrane protein 3 (Ifitm3) in astrocytes has a crucial role in polyI:C-induced neurodevelopmental abnormalities. Through a quantitative proteomic screen, we previously identified candidate astroglial factors, such as matrix metalloproteinase-3 (Mmp3) and follistatin-like 1 (Fstl1), in polyl:C-induced neurodevelopmental impairment. Here, we characterized the Ifitm3-dependent inflammatory processes focusing on astrocyte-derived Fstl1 following polyI:C treatment to assess the neuropathologic role of Fstl1. Methods Astrocytes were treated with PBS (control) or polyI:C (10 μg/mL). The conditioned medium was collected 24 h after the polyI:C treatment and used as astrocyte condition medium (ACM). The expression of Fstl1 mRNA and extracellular Fstl1 protein levels were analyzed by quantitative PCR and western blotting, respectively. For functional studies, neurons were treated with ACM and the effects of ACM on dendritic elongation were assayed. To examine the role of Fstl1, recombinant Fstl1 protein and siRNA for Fstl1 were used. To investigate the expression of Fstl1 in vivo, neonatal mice were treated with vehicle or polyI:C on postnatal day 2 to 6. Results ACM prepared with polyI:C (polyI:C ACM) contained significantly higher Fstl1 protein than control ACM, but no increase in Fstl1 was observed in polyI:C ACM derived from Ifitm3-deficient astrocytes. We found that the production of Fstl1 involves the inflammatory responsive molecule Ifitm3 in astrocytes and influences neuronal differentiation. In agreement, the levels of Fstl1 increased in the hippocampus of polyI:C-treated neonatal mice. COS7 cells co-transfected with both Fstl1 and Ifitm3 had higher extracellular levels of Fstl1 than the cells transfected with Fstl1 alone. Treatment of primary cultured hippocampal neurons with recombinant Fstl1 impaired dendritic elongation, and the deleterious effect of polyI:C ACM on dendritic elongation was attenuated by knockdown of Fstl1 in astrocytes. Conclusions The extracellular level of Fstl1 is regulated by Ifitm3 in astrocytes, which could be involved in polyI:C-induced neurodevelopmental impairment.

It has been recognized that serotonin 2A receptor (5-HT2A) agonist 2,5-dimethoxy-4-iodo-amphetamine (DOI) impairs serotonergic homeostasis. However, the mechanism of DOI-induced serotonergic behaviors remains to be explored. Moreover, little is known about therapeutic interventions against serotonin syndrome, although evidence suggests that ginseng might possess modulating effects on the serotonin system. As ginsenoside Re (GRe) is well-known as a novel antioxidant in the nervous system, we investigated whether GRe modulates 5-HT2A receptor agonist DOI-induced serotonin impairments. We proposed that protein kinase Cδ (PKCδ) mediates serotonergic impairments. Treatment with GRe or 5-HT2A receptor antagonist MDL11939 significantly attenuated DOI-induced serotonergic behaviors (i.e., overall serotonergic syndrome behaviors, head twitch response, hyperthermia) by inhibiting mitochondrial translocation of PKCδ, reducing mitochondrial glutathione peroxidase activity, mitochondrial dysfunction, and mitochondrial oxidative stress in wild-type mice. These attenuations were in line with those observed upon PKCδ inhibition (i.e., pharmacologic inhibitor rottlerin or PKCδ knockout mice). Furthermore, GRe was not further implicated in attenuation mediated by PKCδ knockout in mice. Our results suggest that PKCδ is a therapeutic target for GRe against serotonergic behaviors induced by DOI.

Abstract Background Ginkgo biloba has been reported to possess free radical-scavenging antioxidant activity and anti-inflammatory properties. In our pilot study, YY-1224, a terpene trilactone-strengthened extract of G. biloba, showed anti-inflammatory, neurotrophic, and antioxidant effects. Results We investigated the pharmacological potential of YY-1224 in β-amyloid (Aβ) (1-42)-induced memory impairment using cyclooxygenase-2 (COX-2) knockout (−/−) and APPswe/PS1dE9 transgenic (APP/PS1 Tg) mice. Repeated treatment with YY-1224 significantly attenuated Aβ (1-42)-induced memory impairment in COX-2 (+/+) mice, but not in COX-2 (−/−) mice. YY-1224 significantly attenuated Aβ (1-42)-induced upregulation of platelet-activating factor (PAF) receptor gene expression, reactive oxygen species, and pro-inflammatory factors. In addition, YY-1224 significantly inhibited Aβ (1-42)-induced downregulation of PAF-acetylhydrolase-1 (PAF-AH-1) and peroxisome proliferator-activated receptor γ (PPARγ) gene expression. These changes were more pronounced in COX-2 (+/+) mice than in COX-2 (−/−) mice. YY-1224 significantly attenuated learning impairment, Aβ deposition, and pro-inflammatory microglial activation in APP/PS1 Tg mice, whereas it significantly enhanced PAF-AH and PPARγ expression. A preferential COX-2 inhibitor, meloxicam, did not affect the pharmacological activity by YY-1224, suggesting that the COX-2 gene is a critical mediator of the neuroprotective effects of YY-1224. The protective activity of YY-1224 appeared to be more efficacious than a standard G. biloba extract (Gb) against Aβ insult. Conclusions Our results suggest that the protective effects of YY-1224 against Aβ toxicity may be associated with its PAF antagonistic- and PPARγ agonistic-potential as well as inhibition of the Aβ-mediated pro-inflammatory switch of microglia phenotypes through suppression of COX-2 expression.

Methamphetamine (METH), a commonly abused drug, elevates extracellular dopamine (DA) levels by inducing DA efflux through the DA transporter (DAT). Emerging evidence in rodent models suggests that locomotor responses to a novel inescapable open field may predict behavioral responses to abused drugs; METH produces more potent stimulant effects in high responders to novelty than in low responders. We herein found that mice deficient in protein tyrosine phosphatase receptor type Z (Ptprz-KO) exhibited an enhanced behavioral response to novelty; however, METH-induced hyperlocomotion was significantly lower in Ptprz-KO than in wild-type mice when METH was administered at a non-toxic dose of 1 mg per kg body weight (bdw). Single-cell RT-PCR revealed that the majority of midbrain DA neurons expressed PTPRZ. No histological alterations were observed in the mesolimbic or nigrostriatal dopaminergic pathways in Ptprz-KO brains; however, a significant decrease was noted in brain DA turnover, suggesting functional alterations. In vivo microdialysis experiments revealed that METH-evoked DA release in the nucleus accumbens was significantly lower in Ptprz-KO mice than in wild-type mice. Consistent with this result, Ptprz-KO mice showed significantly fewer cell surface DAT as well as weaker DA uptake activity in striatal synaptosomes prepared 1 hr after the administration of METH than wild-type mice, while no significant differences were observed in the two groups treated with saline. These results indicate that the high response phenotype of Ptprz-KO mice to novelty may not be simply attributed to hyper-dopaminergic activity, and that deficits in PTPRZ reduce the effects of METH by reducing DAT activity.

Dextromethorphan (DM) administered at supra-antitussive doses produce psychotoxic and neurotoxic effects in humans. We administered DM (80 mg/kg) to rats intraperitoneally to determine the ultrastructural change induced by DM, because intraperitoneal route is sensitive for the behavioral responses. Treatment with DM resulted in mitochondrial dysfunction and formation of myelinoid bodies in the hippocampus. MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate] attenuated DM-induced cytosolic oxidative burdens. However, neither MK-801 nor naloxone affected DM-induced mitochondrial dysfunction and formation of myelinoid bodies, indicating that the neurotoxic mechanism needs to be further elucidated. Therefore, the spectrum of toxicological effects associated with DM need to be reassessed.

The authors wish to make the following corrections to their paper [...]

Environmental conditions, including enrichment and stress, affect animal behaviors, but limited information is available regarding the differences in animal functions between the chamber (ventilated system) vs. IVC (individually ventilated cages) housing systems. Therefore, the effects of different housing systems were examined on physical, emotional, and cognitive functions and the intestinal flora with aging. DBA/2CrSlc mice were divided into chamber and IVC groups. Differences in the structure of the two cages considered whether the mouse could dangle or not. Physical, emotional, and cognitive functions were examined using the open field, black and white box, object recognition, horizontal bar, wire hanging, balancing, footprint, and locomotor tests. The IVC group demonstrated significantly less food intake, higher body weight (by approximately 5 g), lower rectal core temperature, less muscle and balancing powers with aging, and fewer anxiety-like behaviors than the chamber group. No differences were observed in the cognitive function and intestinal microbiota between the groups. The housing environment affected the rodent basal temperature and body weight as well as the physical and emotional functions. Scientists should be attentive to the type of cages used in the housing system for an experiment, especially when comparing the results with animals reared in different systems.

BackgroundIt has been recognized that a defect in klotho gene expression accelerates the degeneration of multiple age-sensitive traits. Accumulating evidence indicates that aging is associated with declines in cognitive function and the activity of growth hormone (GH)/insulin-like growth factor-1 (IGF-1).MethodsIn this study, we examined whether a GH-releaser diet could be effective in protecting against cognitive impairment in klotho mutant mice.ResultsThe GH-releaser diet significantly induced the expression of IGF-1 and IGF-1 receptors in the hippocampus of klotho mutant mice. Klotho mutant mice showed significant memory impairments as compared with wild-type mice. In addition, the klotho mutation significantly decreased the expression of cell survival/antiapoptotic factors, including phospho-Akt (p-Akt)/phospho-glycogen synthase kinase3β (p-GSK3β), phospho-extracellular signal-related kinase (p-ERK), and Bcl-2, but significantly increased those of cell death/proapoptotic factors, such as phospho-c-jun N-terminal kinase (p-JNK), Bax, and cleaved caspase-3 in the hippocampus. Treatment with GH-releaser diet significantly attenuated both decreases in the expression of cell survival/antiapoptotic factors and increases in the expression of cell death/proapoptotic factors in the hippocampus of klotho mutant mice. In addition, klotho mutation-induced oxidative stress was significantly attenuated by the GH-releaser diet. Consequently, a GH-releaser diet significantly improved memory function in the klotho mutant mice. GH-releaser diet-mediated actions were significantly reversed by JB-1, an IGF-1 receptor antagonist.ConclusionThe results suggest that a GH-releaser diet attenuates oxidative stress, proapoptotic changes and consequent dysfunction in klotho mutant mice by promoting IGF-1 expression and IGF-1 receptor activation.

Purpose: Heavy and long-term alcohol consumption increase the risk of alcohol-related diseases. Epidemiological studies show moderate drinking reduces the risk of mortality, cardiovascular diseases, and brain infarction in the J-shaped or U-shaped curve effect. However, why moderate drinkers may be healthy and non-drinkers may be ill in diverse populations remains controversial. Herein, we examined the relationship between moderate/lifelong alcohol intake and aging, especially aging-related cognitive functions in senescence-accelerated mouse prone 8 (SAMP8) model. Methods: SAMP8 model (5-week-old, male, n = 36), a model of age-related cognitive deficit, were group-housed (n = 6/cage) and provided free access to water (water group, n = 18) or 1% ethanol (EtOH group, n = 18, intake started when mice were 9 weeks old). The object recognition test (ORT) and object location test (OLT) were used to evaluate cognitive functions. The intestinal flora at the age of 87 weeks was analyzed by terminal restriction fragment length polymorphism (T-RFLP). Results: The lifespan of the EtOH-group mice was about 4 weeks longer than that of the water-group mice. In the EtOH group, spatial recognition impairment, assessed by OLT, was observed later (age, 73 weeks) than that in the water group (age, 52 weeks). The spinal curvature and skin conditions progressed significantly slower in the EtOH group than in the water group. Moreover, diarrhea symptoms only appeared in the water group, at the age of 82 weeks. The T-RFLP analysis of the intestinal flora indicated higher Lactobacillales order and lower Clostridium cluster XI in the EtOH group than in the water group, although those were extremely high in some mice close to death in both groups. Water-group mice with diarrhea presented significantly higher Clostridium cluster XI than did those without diarrhea (P = 0.017). Conclusion: Moderate alcohol intake changes intestinal flora and positively affects aging of SAMP8 model.

Barley intake reportedly reduces the risk of cardiovascular disease, but effects on the systemic phenotypes during healthy aging have not yet been examined. Therefore, we examined the effects of barley on the lifespan; behavioral phenotypes, such as locomotor activity, and cognitive functions, and intestinal microbiome in the senescence-accelerated mouse-prone 8 (SAMP8) mouse. We prepared two mild high-fat diets by adding lard, in which the starch components of AIN-93G were replaced by rice or barley “Motchiriboshi.” SAMP8 (four weeks old, male) mice were fed AIN-93G until eight weeks old, and then rice (rice group) or barley diet (rice: barley = 1:4, barley group) until death. Changes in aging-related phenotypes, object and spatial recognition, locomotor and balancing activities, and the intestinal microbiome were recorded. Moreover, plasma cholesterol levels were analyzed at 16 weeks old. Barley intake prolonged the lifespan by approximately four weeks, delayed locomotor atrophy, and reduced balancing ability and spatial recognition. Barley intake significantly increased the medium and small particle sizes of high-density lipoprotein (HDL) cholesterol, which is associated with a reduced risk of total stroke. The Bacteroidetes to Firmicutes ratio in the barley group was significantly higher than that in the rice group during aging. Thus, lifelong barley intake may have positive effects on healthy aging.

The number of patients with schizophrenia has increased over the past decade. Previously, many studies have been performed to establish its diagnostic criteria, prophylactic methods, and effective therapies. In this study, we analyzed whether the ratios of DNA methylation in CpG islands of the Shati/Nat8l is decreased in model mice of schizophrenia-like phenotype using genomic DNA collected from brain regions and peripheral blood, since the mouse model of schizophrenia-like phenotype, mice treated repeatedly with methamphetamine showed increase of Shati/Nat8l mRNA expression in our previous experiment. The ratios of Shati/Nat8l CpG island methylation were significantly decreased in both the nucleus accumbens and the peripheral blood of model mice compared with those of control mice. We also investigated Shati/Nat8l methylation in the blood of patients with schizophrenia. We found that Shati/Nat8l CpG island methylation ratios were lower in the patients with schizophrenia than in the healthy controls, which is consistent with our findings in the mice model. To our knowledge, this is the first study to show similar alterations in methylation status of a particular genomic DNA site in both the brain and peripheral blood of mice. Furthermore, the same phenomenon was observed in corresponding human genomic sequences of the DNA extracted from the peripheral blood of patients with schizophrenia. Based on our findings, DNA methylation profiles of the CpG island of Shati/Nat8l might be a diagnostic biomarker of schizophrenia.

Polyriboinosinic-polyribocytidilic acid (polyI:C) is a synthetic analog that elicits viral-like immune responses in mammals. We have recently found that polyI:C treatment in neonatal mice induced abnormalities of emotional, cognitive, and sensorimotor gating and dysfunction of glutamatergic neurotransmission in adulthood. In this study, we investigated the effect of the NMDA-receptor co-agonist d-serine on polyI:C-induced behavioral abnormalities in mice. Neonatal ICR mice were repeatedly injected with polyI:C for 5 days from postnatal day 2 to 6. At 10 weeks, sensorimotor gating function was analyzed in the prepulse inhibition (PPI) test. Emotional function was analyzed in open field and social interaction tests. Cognitive function was analyzed by novel object recognition tests. d-Serine dose-dependently improved polyI:C-induced impairment of emotional and cognitive behaviors whereas it had no effect on PPI deficit in adults. The ameliorating effects of d-serine were antagonized by pretreatment with an NMDA-receptor antagonist, MK-801. Although the mRNA level of d-amino acid oxidase (DAAO) was increased in the prefrontal cortex and hippocampus of neonatal polyI:C-treated mice in adulthood, no changes were observed in d-serine content and DAAO enzymatic activity. These results suggest that d-serine ameliorates emotional and cognitive impairments of the polyI:C-treated mice through potentiating NMDA receptor activity. Keywords:: cognition, emotion, d-serine, polyI:C, d-amino acid oxidase

Purpose: Due to the use of multiple drugs and prevalence of diminished cognitive function, community-dwelling elderly individuals are more likely to have drug-related issues. We examined changes in quality of life (QOL) and activities of daily living (ADL) 3 months and 6 months after reducing drug use of dementia patients who had newly begun community-dwelling care. Methods: Prescription drug use was reduced in the intervention group, whereas the non-intervention group continued their regimen or began using additional drugs. QOL and ADL were assessed with the Japanese version of the EQ-5D and the Barthel Index, respectively. Results: Subjects were 32 individuals aged ≥65 years who had begun community-dwelling between March and July 2014 and had received approval for long-term care insurance. On average, the intervention group (n = 19) stopped using 2.6 prescription drugs. After 6 months, the differences in the QOL and ADL scores in the intervention group were -0.03 ± 0.29 and 6.32 ± 18.6, respectively, while the differences in the QOL and ADL scores in the non-intervention group (n = 13) were -0.13 ± 0.29 and -2.69 ± 23.7, respectively. In the intervention group, ADL scores were significantly increased by 14.0 ± 11.1 6 months after reduced benzodiazepine use. Conclusions: QOL was maintained with reduced drug use, while ADL score was slightly increased. In addition, the reduction of benzodiazepine use significantly increased ADL. In order to reduce polypharmacy among community-dwelling elderly patients, it is necessary to create an opportunity for pharmacists to re-examine their prescriptions This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

Abstract.: Dextromethorphan (3-methoxy-17-methylmorphinan) has complex pharmacologic effects on the central nervous system. Although some of these effects are neuropsychotoxic, this review focuses on the neuroprotective effects of dextromethorphan and its analogs. Some of these analogs, particularly dimemorfan (3-methyl-17-methylmorphinan) and 3-hydroxymorphinan, have promising neuroprotective properties with negligible neuropsychotoxic effects. Their neuroprotective effects, the mechanisms underlying these effects, and their therapeutic potential for the treatment of diverse neurodegenerative disorders are discussed. Keywords:: dextromethorphan, dimemorfan, 3-hydroxymorphinan, neuroprotection, neuropsychotoxicity, neurodegenerative disorder

Parishin C, a major component of Gastrodia elata BLUME (GE), was purified from GE. Because GE modulates the serotonergic system and the 5-HT1A receptor is an important therapeutic target of schizophrenia, we examined whether parishin C affects phencyclidine-induced abnormal behaviors in mice. Phencyclidine-induced abnormal behaviors were significantly ameliorated by parishin C. These effects were reversed by WAY 100635, a 5-HT1A–receptor antagonist. Consistently, parishin C showed high affinity at 5-HT1A receptor as well as a 5-HT1A–agonist activity in a 8-OH-DPAT–stimulated [ 35S]GTP-γS binding assay. Our results suggest that the antipsychotic effects of parishin C require activation of 5-HT1A receptors. Keywords:: parishin C, phencyclidine, 5-HT1A receptor

We previously demonstrated that the growth hormone (GH)-releaser diet ameliorated β-amyloid (Aβ) (1-42)–induced memory impairment, but the underlying mechanism remained to be characterized. We show here that the GH-releaser diet significantly attenuated Aβ(1-42)-induced impairment in context-dependent conditioned fear, with a reduction in GH levels and changes in hippocampal acetylcholine, acetylcholinesterase, choline acetyltransferase, insulin-like growth factor (IGF)-1, and IGF-1–receptor activity in mice. JB-1, an IGF-1–receptor antagonist, significantly blocked GH-releaser diet–mediated pharmacological actions. Our results suggest that the GH-releaser diet prevents Aβ(1-42)-induced cognitive deficits via stimulation of the hippocampal IGF-1 receptor. Keywords:: growth hormone releaser, β-amyloid, insulin-like growth factor (IGF)-1 receptor

Nicotine, a primary component of tobacco, is one of the most abused drugs worldwide. Mesolimbic dopaminergic neurons mediate the rewarding effects of abused drugs, including nicotine. We show that the tissue plasminogen activator (tPA) – plasmin system regulates nicotine-induced reward and dopamine release in the nucleus accumbens (NAc) by activating proteinase-activated receptor 1 (PAR1). Nicotine-induced conditioned place preference and dopamine release in the NAc are diminished in tPA knockout (tPA−/−) mice. The defect of nicotine-induced dopamine release in tPA−/− mice is reversed by microinjection of either exogenous tPA or plasmin into the NAc. Acute nicotine treatment increases tPA protein levels and promoted the release of tPA into the extracellular space. The expression of PAR1 on dopaminergic neurons is evident and the activation of PAR1 by plasmin is demonstrated by assaying GTP-γS binding. Finally, nicotine-induced conditioned place preference and dopamine release are diminished in PAR1−/− mice. These findings suggest that targeting the tPA-plasmin– PAR1 system would provide new therapeutic approaches for the treatment of nicotine dependence. Keywords:: dependence, dopamine, nicotine, proteinase-activated receptor, 1 (PAR1), tissue plasminogen activator (tPA)

To investigate the role of tissue plasminogen activator (tPA) in methamphetamine (METH)-induced dopaminergic neurotoxicity, we compared the changes in tyrosine hydroxylase (TH) and dopamine transporter (DAT) levels in the striatum after repetitive treatment of METH at 4 mg/kg among wild-type, tPA-deficient (tPA−/−), and protease activated receptor-1–deficient (PAR-1−/−) mice. METH treatment caused a marked decrease in TH and DAT levels in the striatum of those mice with a similar magnitude. No difference in METH-induced abnormal behavior and hyperthermia was observed among the three types of mice. These results suggest that neither tPA nor PAR-1 is involved in METH-induced dopaminergic neurotoxicity in vivo. Keywords:: methamphetamine, neurotoxicity, tissue plasminogen activator

Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) function to remodel the pericellular environment. We have investigated the role of the MMP/ TIMP system in methamphetamine (METH) dependence in rodents, in which the remodeling of neural circuits may be crucial. Repeated METH treatment induced behavioral sensitization, which was accompanied by an increase in MMP-2/-9/ TIMP-2 activity in the brain. An antisense TIMP-2 oligonucleotide enhanced the sensitization, which was associated with a potentiation of the METH-induced release of dopamine in the nucleus accumbens (NAc). MMP-2/-9 inhibitors blocked the METH-induced behavioral sensitization and conditioned place preference (CPP), a measure of the rewarding effect of a drug, and reduced the METH-increased dopamine release in the NAc. In MMP-2– and MMP-9–deficient mice, METH-induced behavioral sensitization and CPP as well as dopamine release were attenuated. The MMP/ TIMP system may be involved in METH-induced sensitization and reward by regulating extracellular dopamine levels. Keywords:: drugs of abuse, matrix metalloproteinase, tissue inhibitor of matrix metalloproteinase, methamphetamine, dopamine

Drug abuse involving dextromethorphan, an antitussive, has been a social problem in various geographic locations since the 1960s. Ironically, high doses of the drug confer neuroprotective activity with central nervous system and behavioral effects. Accumulating evidence suggests that metabolism to phencyclidine-like dextrorphan is not essential for the neuroprotective activity of dextromethorphan. Here, we review the neuroprotective properties of dextromethorphan and its potential for abuse and the potential neuroprotective effects of the drug’s analogs and 3-hydroxymorphinan, a metabolite of dextromethorphan. These compounds may provide a novel therapeutic direction for the treatment of neurodegenerative diseases such as convulsive or parkinsonian-like disorders. Keywords:: drugs of abuse, dextromethorphan and its analog, phencyclidine-like dextrorphan, 3-hydroxymorphinan, neuroprotective effect

We demonstrated that exposure to extremely low frequency magnetic fields (ELF-MF) enhanced dopamine levels in the rat striatum. To extend our understanding, we examined the role of dopaminergic receptors in ELF-MF–induced behavioral changes. Exposure to ELF-MF (2.4 mT, 1 h/day, for one or seven days) enhanced locomotor activity in a time-dependent manner. This hyperlocomotor activity paralleled an increase in c-Fos-like immunoreactivity (c-Fos-IR). Pretreatment with SCH23390, a dopaminergic D1-like receptor antagonist, but not with sulpiride, a dopaminergic D2-like receptor antagonist, inhibited ELF-MF–induced increased locomotor activity and c-Fos-IR. Thus, our results suggest that ELF-MF–induced behavioral responses are, at least in part, mediated by activation of dopamine D1-like receptors. Keywords:: extremely low frequency magnetic field, locomotor activity, dopaminergic receptor

There are few efficacious medications for drug dependence at present. Recent evidence has suggested that various cytokines are involved in the effects of abused drugs, suggesting that these factors play a role in drug dependence. In this article, the roles of glial cell line-derived neurotrophic factor (GDNF) and tumor necrosis factor-α (TNF-α) in drug dependence are discussed. GDNF inhibits the cocaine-induced upregulation of tyrosine hydroxylase activity in the ventral tegmental area and blocks behavioral responses to cocaine. TNF-α attenuates rewarding effects and locomotor sensitization induced by methamphetamine (METH) and morphine (MOR). Moreover, we mentioned the potential of Leu-Ile, which induces the expression of GDNF and TNF-α, as a novel therapeutic agent for drug dependence. Leu-Ile inhibits not only the development but also the maintenance of METH- or MOR-induced place preference and locomotor sensitization in mice. The inhibitory effect of Leu-Ile on METH- or MOR-induced place preference is not observed in GDNF heterozygous and TNF-α knockout mice. Leu-Ile inhibits METH- or MOR-induced place preference and sensitization by attenuating the METH- or MOR-induced increase in extracellular dopamine levels in the nucleus accumbens via the induction of GDNF and TNF-α expression. These findings suggest that Leu-Ile could be a novel therapeutic agent for drug dependence. Keywords:: glial cell line-derived neurotrophic factor, tumor necrosis factor-α, methamphetamine, morphine, Leu-Ile

Major local adverse reactions in the nicotine patches are skin reactions. To assess the skin reaction of PHK-301p, a newly developed nicotine patch, we conducted a phase I study that consisted of 2 parts: a skin irritation test (48-h closed patch test) and a photosensitivity test (24-h closed patch test + Ultraviolet A irradiation). Twenty healthy men were treated with PHK-301p and placebo. Both preparations were punched out to a circle of 6-mm diameter and were applied simultaneously to each participant. Skin irritation and photosensitivity were assessed by a physician who was kept unaware of the treatment. In the skin irritation test, moderate and mild erythemas were observed in each participant 72 h after application (24 h after removal) for PHK-301p. Mild erythema was observed in one participant 49 h after application (1 h after removal) for placebo. The skin irritation index, which was calculated based on the skin reactions of participants, was 7.5 for PHK-301p and 2.5 for placebo. In the photosensitivity test, one participant had mild erythema (±) approximately 25 and 72 h after application of PHK-301p. No solar urticaria was observed. From these results, we concluded that PHK-301p is an acceptable product as a nicotine patch. Keywords:: nicotine replacement therapy, patch test, smoking cessation, nicotine patch, skin reaction

The mesocorticolimbic dopaminergic system plays an important role in the reinforcing effects of drugs of abuse, and the activity-dependent synaptic plasticity of the system is involved in drug dependence. A DNA microarray screening revealed that the expression levels of tissue plasminogen activator (tPA) mRNA in the nucleus accumbens of morphine- or methamphetamine-dependent rats were significantly increased compared with those in control animals. Since tPA plays a role in synaptic plasticity, we hypothesized that tPA may contribute to the development of drug dependence. Single and repeated morphine treatment as well as repeated methamphetamine treatment induced tPA mRNA expression in the nucleus accumbens, which was associated with an increase in the enzyme activity. Conditioned place preference induced by morphine was markedly reduced in mice with a targeted deletion of the tPA gene (tPA−/− mice), being accompanied by a loss of morphine-induced dopamine release. Similarly, methamphetamine-induced conditioned place preference and locomotor sensitization were reduced in tPA−/− mice. The defects of morphine-induced hyperlocomotion as well as methamphetamine-induced locomotor sensitization in tPA−/− mice were reversed by microinjection of exogenous tPA or plasmin into the nucleus accumbens. These results support our hypothesis that tPA plays a role in long-lasting neuronal changes related to drug dependence. Keywords:: dependence, methamphetamine, morphine, plasmin, tissue plasminogen activator

Amyloid β-protein (Aβ) is one of the most studied peptides in human neurodegenerative disorders. Although much has been learned about the biochemistry of this peptide, fundamental questions such as when and how the Aβ becomes pathologic remain unanswered. In this article we review the recent findings on the biology and pathology of Aβ and the role protein kinase C (PKC) plays in these processes. The potential neuroprotective role of PKC and the possible therapeutic effects of PKC activators in Alzheimer’s disease (AD) will be discussed. Briefly, comments will be also addressed on the role of PKC in cell death and neurogenesis in AD. Keywords:: amyloid protein, Alzheimer’s disease, signal transduction, protein kinase C, cell death

Neurologists have little concern about the high atherosclerotic risk among epileptics. Recent evidences mount that chronic epilepsy and prolonged use of antiepileptic drugs (AEDs) are associated with multiple risk factors that are critically implicated in pathobiology and dysfunction of the vessel wall through complex molecular mechanisms that promote atherogenesis. This review is concerned with three metabolic alterations, which are attributed as major risk factors for atherosclerosis among epileptics: altered metabolism of a) homocysteine (Hcy), b) lipids and lipoproteins, and c) uric acid. Most conventional AEDs reduce folic acid levels, thereby raising Hcy levels. Hyperhomosysteinemia is recently believed to induce endothelial dysfunction and promote atherosclerosis through complex oxidative and excitatory neurotoxic molecular mechanisms. However, Hcy itself is a convulsing substance with increased seizure recurrence and intractability to antiepileptic medications. AEDs can disturb lipid metabolism with resultant hypercholestrolemia and dyslipidemia, common recognized risks for atherosclerosis. Altered uric acid metabolism is common among epileptics. Uric acid has been implicated in endothelial cell damage and decreased endothelial nitric oxide bioavailability. In the presence of atherosclerotic milieu, uric acid interacts with other substrate toxicities and increased reactive oxygen species, accelerating atherosclerosis. The above information forms the rationale for future routine screening and correction of such metabolic alterations in epileptics. A convincing argument now develops that routine polyvitamin supplementation (folic acid, vitamin B12, vitamin B6, vitamin C, vitamin E, and β-carotene) becomes increasingly important for women and men receiving AEDs at all ages. The atheroprotective effect of multivitamins is through their antioxidant and anti-inflammatory effects together with their lipid and Hcy lowering effects. Keywords:: atherosclerosis, epilepsy, homocysteine, oxidative stress, multivitamin

Accumulating evidence indicates that growth hormone (GH) might be effective at preventing the development of Alzheimer’s disease. However, exogenous GH treatment has exhibited side effects for clinical application; thus supplementation with amino acids to promote the release of GH could be a possible alternative treatment. In this study, mice that were fed with a diet of GH-releasing supplements had significantly attenuated memory impairments and hippocampal changes in the acetylcholinesterase activity and acetylcholine level induced by amyloid beta protein (Aβ) (1 – 42). Our results suggest that the use of GH-releasing supplement exerts beneficial effects on the memory impairment induced by Aβ (1 – 42). Keywords:: growth hormone releaser, amyloid beta protein, cognitive enhancer

Activity-dependent changes in synaptic strength are considered mechanisms underlying learning and memory. Brain-derived neurotrophic factor (BDNF) plays an important role in activity-dependent synaptic plasticity such as long-term potentiation. Recent experimental evidence supports the role of BDNF in memory processes: Memory acquisition and consolidation are associated with an increase in BDNF mRNA expression and the activation of its receptor TrkB. Genetic as well as pharmacologic deprivation of BDNF or TrkB impairs learning and memory. In a positively motivated radial arm maze test, activation of the TrkB/phosphatidylinositol-3 kinase (PI3-K) signaling pathway in the hippocampus is associated with consolidation of spatial memory through an activation of translational processes. In a negatively motivated passive avoidance test, mitogen-activated protein kinase (MAPK) is activated during acquisition of fear memory. Furthermore, recent findings suggest the importance of interaction between BDNF/TrkB signaling and NMDA receptors for spatial memory. A Src-family tyrosine kinase, Fyn plays a role in this interaction by linking TrkB with NR2B. These findings suggest that BDNF/TrkB signaling in the hippocampus plays a crucial role in learning and memory.

The single nucleotide polymorphism (SNP) rs13438494 in intron 24 of PCLO was significantly associated with bipolar disorder in a meta-analysis of genome-wide association studies. In this study, we performed functional minigene analysis and bioinformatics prediction of splicing regulatory sequences to characterize the deep intronic SNP rs13438494. We constructed minigenes with A and C alleles containing exon 24, intron 24, and exon 25 of PCLO to assess the genetic effect of rs13438494 on splicing. We found that the C allele of rs13438494 reduces the splicing efficiency of the PCLO minigene. In addition, prediction analysis of enhancer/silencer motifs using the Human Splice Finder web tool indicated that rs13438494 induces the abrogation or creation of such binding sites. Our results indicate that rs13438494 alters splicing efficiency by creating or disrupting a splicing motif, which functions by binding of splicing regulatory proteins, and may ultimately result in bipolar disorder in affected people.

The tail suspension test (TST) is widely recognized as a useful experimental paradigm for assessing antidepressant activity and depression-like behavior. We have previously identified ubiquitin-specific peptidase 46 (Usp46) as a quantitative trait gene responsible for decreasing immobility time in the TST in mice. This Usp46 mutation has a 3-bp deletion coding for lysine in the open reading frame, and we indicated that Usp46 is implicated in the regulation of the GABAergic system. However, it is not known precisely how the immobile behavior is regulated by the GABAergic system. Therefore, in the present study, we examined whether the immobility time is influenced by drugs affecting the action mediated by GABA(A) receptor using both 3-bp deleted (the Usp46 mutant) and null Usp46 (Usp46 KO) mice. Nitrazepam, an agonist at the benzodiazepine-binding site of the GABA(A) receptor, which potentiates the action of GABA, produced a dose-dependent increase in TST immobility time in the Usp46 mutant mice without affecting general behaviors. The Usp46 KO mice exhibited short immobility times comparable to the Usp46 mutant mice, which was also increased by nitrazepam administration. The effects of nitrazepam in the Usp46 mutant and KO mice were antagonized by flumazenil. These results indicate that the 3-bp deleted Usp46 mutation causes a loss-of-function phenotype, and that the GABA(A) receptor might participate in the regulation of TST immobility time.

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) remodel the pericellular environment by regulating the cleavage of extracellular matrix proteins, cell surface components, neurotransmitter receptors, and growth factors that mediate cell adhesion, synaptogenesis, synaptic plasticity, and long-term potentiation. Interestingly, increased MMP activity and dysregulation of the balance between MMPs and TIMPs have also been implicated in various pathologic conditions. In this paper, we discuss various animal models that suggest that the activation of the gelatinases MMP-2 and MMP-9 is involved in pathogenesis of drug dependence, Alzheimer's disease, and epilepsy.

Phencyclidine (PCP), a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, increases locomotor activity in rodents and causes schizophrenia-like symptoms in humans. Although activation of the dopamine (DA) pathway is hypothesized to mediate these effects of PCP, the precise mechanisms by which PCP induces its effects remain to be elucidated. The present study investigated the effect of PCP on extracellular levels of DA (DA(ex)) in the striatum and prefrontal cortex (PFC) using in vivo microdialysis in mice lacking the NMDA receptor channel ε1 or ε4 subunit (GluRε1 [GluN2A] or GluRε4 [GluN2D]) and locomotor activity. PCP significantly increased DA(ex) in wildtype and GluRε1 knockout mice, but not in GluRε4 knockout mice, in the striatum and PFC. Acute and repeated administration of PCP did not increase locomotor activity in GluRε4 knockout mice. The present results suggest that PCP enhances dopaminergic transmission and increases locomotor activity by acting at GluRε4.

Indoleamine 2,3-dioxygenase 2 (IDO2) is an enzyme of the tryptophan- kynurenine pathway that is constitutively expressed in the brain. To provide insight into the physiological role of IDO2 in the brain, behavioral and neurochemical analyses in IDO2 knockout (KO) mice were performed. IDO2 KO mice showed stereotyped behavior, restricted interest and social deficits, traits that are associated with behavioral endophenotypes of autism spectrum disorder (ASD). IDO2 was colocalized immunohistochemically with tyrosine-hydroxylase-positive cells in dopaminergic neurons. In the striatum and amygdala of IDO2 KO mice, decreased dopamine turnover was associated with increased a-synuclein level. Correspondingly, levels of downstream dopamine D1 receptor signaling molecules such as brain-derived neurotrophic factor and c-Fos positive proteins were decreased. Furthermore, decreased abundance of ramified-type microglia resulted in increased dendritic spine density in the striatum of IDO2 KO mice. Both chemogenetic activation of dopaminergic neurons and treatment with methylphenidate, a dopamine reuptake inhibitor, ameliorated the ASD-like behavior of IDO2 KO mice. Sequencing analysis of exon regions in IDO2 from 309 ASD samples identified a rare canonical splice site variant in one ASD case. These results suggest that the IDO2 gene is, at least in part, a factor closely related to the development of psychiatric disorders. [ABSTRACT FROM AUTHOR]