Ido2 Deficiency Exacerbates Motor Impairment and Reduces Aryl Hydrocarbon Receptor Activity through Decreased Kynurenine in a Chronic Demyelinating Mouse Model.

Demyelinating diseases including multiple sclerosis (MS) are chronic inflammatory diseases of the central nervous system. Indoleamine 2,3-dioxygenase 2 (Ido2) is a recently identified as catalytic enzyme involved in the rate-limiting step of the tryptophan-kynurenine pathway that influences susceptibility to inflammatory diseases. However, the pathological role of Ido2 in demyelination remains unclear. In this study, we investigated whether Ido2 deficiency influences the pathogenesis of proteolipid protein transgenic (Plp tg) mice, an animal model of chronic demyelination. Ido2 deficiency exacerbates impairments of motor function in the locomotor activity test, wire hanging test, and rotarod test. Ido2 deficiency caused severe demyelination associated with CD68-positive microglial activation in Plp tg mice. In the cerebellum of Plp tg mice, Ido2 deficiency significantly increased the expression of Tnfα. Ido2 deficiency reduced tryptophan metabolite kynurenine (KYN) levels and subsequent aryl hydrocarbon receptor (AhR) activity, which play an important role in anti-inflammatory response. These results suggest that Ido2 has an important role in preventing demyelination through AhR. Taken together, Ido2 could be a potential therapeutic target for demyelinating diseases.

Chronic social defeat stress induces the down-regulation of the Nedd4L-GLT-1 ubiquitination pathway in the prefrontal cortex of mice.

Stressful life events contribute to the onset of major depressive disorder (MDD). We recently demonstrated abnormalities in ubiquitination in the pathophysiology of MDD. However, the underlying molecular mechanisms remain unclear. We investigated the involvement of the ubiquitination system-mediated glutamatergic dysfunction in social impairment induced by chronic social defeat stress (CSDS). Adult C57BL/6J mice were exposed to aggressor ICR male mice for 10 consecutive days. Social impairment was induced by CSDS in the social interaction test 1 days after the last stress exposure. In terms of brain microdialysis, CSDS reduced depolarization-evoked glutamate release in the prefrontal cortex (PFC), which was reversed by a glutamate transporter 1 (GLT-1) inhibitor. Interestingly, the expression of ubiquitinated, but not total GLT-1, was decreased in the PFC of mice exposed to CSDS. The expression of neural precursor cells expressing developmentally downregulated gene 4-like (Nedd4L: E3 ligase for GLT-1), and ubiquitin-conjugating enzyme E2D2 (Ube2d2: E2 ubiquitin-conjugating enzyme for Nedd4L) was also reduced in CSDS mice. Furthermore, the downregulation of the Nedd4L-GLT-1 ubiquitination pathway decreased SIT ratio, but up-regulation increased it even in non-CSDS mice. Taken together, the decrease in GLT-1 ubiquitination may reduce the release of extracellular glutamate induced by high-potassium stimulation, which may lead to social impairment, while we could not find differences in GLT-1 ubiquitination between susceptible and resistant CSDS mice. In conclusion, GLT-1 ubiquitination could play a crucial role in the pathophysiology of MDD and is an attractive target for the development of novel antidepressants.

Duloxetine improves chronic orofacial pain and comorbid depressive symptoms in association with reduction of serotonin transporter protein through upregulation of ubiquitinated serotonin transporter protein.

ABSTRACT: Chronic orofacial pain (COP) is relieved by duloxetine (DLX) and frequently causes depressive symptoms. The aim of this study was to confirm effects of DLX on pain and depressive symptoms, and to associate with their effectiveness in platelet serotonin transporter (SERT) expression, which is a target molecule of DLX and plasma serotonin concentration in COP patients with depressive symptoms. We assessed for the severity of pain and depressive symptoms using the Visual Analog Scale (VAS) and 17-item Hamilton Depression Rating Scale (HDRS), respectively. Chronic orofacial pain patients were classified into 2 groups based on their HDRS before DLX-treatment: COP patients with (COP-D) and without (COP-ND) depressive symptoms. We found that the VAS and HDRS scores of both groups were significantly decreased after DLX treatment compared with those before DLX treatment. Upregulation of total SERT and downregulation of ubiquitinated SERT were observed before DLX treatment in both groups compared with healthy controls. After DLX treatment, there were no differences in total SERT of both groups and in ubiquitinated SERT of COP-D patients compared with healthy controls; whereas, ubiquitinated SERT of COP-ND patients remained downregulated. There were positive correlations between changes of serotonin concentrations and of VAS or HDRS scores in only COP-D patients. Our findings indicate that DLX improves not only pain but also comorbid depressive symptoms of COP-D patients. Duloxetine also reduces platelet SERT through upregulation of ubiquitinated SERT. As the result, decrease of plasma serotonin concentrations may be related to the efficacy of DLX in relieving pain and depression in COP patients.

Indoleamine 2,3-dioxygenase 2 deficiency associates with autism-like behavior via dopaminergic neuronal dysfunction.

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 α-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.

Rho kinase inhibitors ameliorate cognitive impairment in a male mouse model of methamphetamine-induced schizophrenia.

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.

High salt induces cognitive impairment via the interaction of the angiotensin II-AT1 and prostaglandin E2-EP1 systems.

BACKGROUND AND PURPOSE: High salt (HS) intake has been associated with hypertension and cognitive impairment. It is well known that the angiotensin II (Ang II)-AT1 receptor and prostaglandin E2 (PGE2)-EP1 receptor systems are involved in hypertension and neurotoxicity. However, the involvement of these systems in HS-mediated hypertension and emotional and cognitive impairments remains unclear. EXPERIMENTAL APPROACH: Mice were loaded with HS solution (2% NaCl drinking water) for 12 weeks, and blood pressure was monitored. Subsequently, effects of HS intake on emotional and cognitive function and tau phosphorylation in the prefrontal cortex (PFC) and hippocampus (HIP) were investigated. The involvement of Ang II-AT1 and PGE2-EP1 systems in HS-induced hypertension and neuronal and behavioural impairments was examined by treatment with losartan, an AT1 receptor blocker (ARB), or EP1 gene knockout. KEY RESULTS: We demonstrate that hypertension and impaired social behaviour and object recognition memory following HS intake may be associated with tau hyperphosphorylation, decreased phosphorylation of Ca2+ /calmodulin-dependent protein kinase II (CaMKII), and postsynaptic density protein 95 (PSD95) expression in the PFC and HIP of mice. These changes were blocked by pharmacological treatment with losartan or EP1 receptor gene knockout. CONCLUSIONS AND IMPLICATIONS: Our findings suggest that the interaction of Ang II-AT1 receptor and PGE2-EP1 receptor systems could be novel therapeutic targets for hypertension-induced cognitive impairment.

[Promoting Appropriate Use of Medications by "Lectures and Practices Regarding Medicine" for the Regional Community Residents].

We held lectures and practices for the regional community residents with the aim of promoting appropriate use of medications. To evaluate the usefulness of our activity, we conducted medicine-related questionnaire surveys (pre- and post-questionnaires) before and after the lectures and practices, and satisfaction with the activity questionnaire surveys (post-questionnaires) after them. We also evaluated the effect of age difference on the results by dividing the participants into elderly (age ≥65) and non-elderly (age <65), before the analysis. In the both (elderly and non-elderly) groups, the ratio of positive answers in several items of post-questionnaire regarding appropriate use of medications was higher than that of pre-questionnaire. These results suggest that the basic medicine-related knowledge improved by attending the lectures and practices, and indicate that the knowledge of the regional community residents is higher than we imagined. Furthermore, there was no difference in the ratio of positive answers between the both groups, suggesting that our activity is applicable to a wide range of age groups. Our activity benefitted the participants, and not only provided education to the regional community residents regarding appropriate drug use, but also lead to the development of regional community activity, by the coming together of the regional community residents of various age.

[Diagnoses and new therapeutic strategy focused on physiological alteration of tryptophan metabolism].

The monoamine hypothesis has been common hypotheses for the pathophysiology of major depressive disorder (MDD). Since mainstream antidepressants are selective serotonin (5-HT) reuptake inhibitors, hypo-serotonergic function has been implicated in the MDD. However, one-third of patients are refractory to the treatment with antidepressants. Tryptophan (TRP) is metabolized via the kynurenine (KYN) and 5-HT pathways. Indoleamine 2,3-dioxygenase 1 (IDO1) is the first metabolizing enzyme in the TRP-KYN pathway which is inducible by pro-inflammatory cytokines, involved depression-like behavior via 5-HT depletion due to decreased level of TRP in the 5-HT pathway. Kynurenine 3-monooxygenase (KMO) is the enzyme in the metabolism of KYN to 3-hydroxykynurenine. KMO deficiency increases level of kynurenic acid (KA), a KYN metabolite by kynurenine aminotransferases (KATs) and induces depression-like behavior. Interestingly, Chronic unpredictable mild stress (CUMS) is associated with a disruption of the hypothalamus-pituitary-adrenocortical (HPA) system and increases KA level with decreased KMO expression in the prefrontal cortex. The decrease of KMO may be related to the reduction in expression of microglia, since KMO is mainly found in microglia in the nervous system. CUMS increases KA level via alternation of enzymes from KMO to KAT. KA is α7 nicotinic acetylcholine receptor (α7nAChR) antagonist. Activation of α7nAChR by nicotine or galantamine attenuates CUMS-induced depression-like behaviors. Taken together, depletion of 5-HT by induction of IDO1 and α7nAChR antagonism by KA via decreased KMO expression cause depression-like behavior, suggesting that metabolic alterations in TRP-KYN pathway are highly involved in the pathophysiology of MDD. Therefore, TRP-KYN pathway is expected to be an attractive target for the development of novel diagnosis of MDD and antidepressants.

An evaluation method for developing abuse-deterrent opioid formulations with agonist and antagonist combinations using conditioned place preference.

Although opioids are useful narcotic analgesics in clinical settings, their misuse and addiction in the United States of America and other countries are rapidly increasing. Therefore, the development of abuse-deterrent formulations is an urgent issue. We herein investigated how to select the ratio of an opioid and the opioid receptor antagonist, naloxone in abuse-deterrent formulations for mice. The conditioned place preference (CPP) test was used to evaluate the rewarding effects of abused drugs. The opioids morphine (30 µmol/kg), oxycodone (3 µmol/kg), fentanyl (0.4 µmol/kg), and buprenorphine (0.5 µmol/kg) significantly induced place preference in mice. We also examined the optimal ratio of naloxone and opioids to inhibit the rewarding effects of the latter. Naloxone (3-5 µmol/kg) effectively inhibited place preference induced by the opioids tested. We calculated theoretical drug doses that exerted the same pharmacodynamic effects based on two parameters: µ-opioid receptor binding affinity and blood-brain barrier (BBB) permeability. Theoretical doses were very close to the drug doses at which mice showed place preference. Therefore, the CPP test is useful as a behavioral method for evaluating abuse-deterrent formulations of opioids mixed with an antagonist. The ratio of naloxone with opioids, at which mice did not show place preference, may be an effective index for developing abuse-deterrent formulations. Ratios may be calculated for other opioids based on µ-opioid receptor binding affinity and BBB permeability.

Neuritogenic steroid glycosides from crown-of-thorns starfish: Possible involvement of p38 mitogen-activated protein kinase and attenuation of cognitive impairment in senescence-accelerated mice (SAMP8) by peripheral administration.

Novel steroid glycosides, acanthasterosides A1, B1, and B3, have been isolated from the crown-of-thorns starfish Acanthaster planci. Acanthasterosides B1 and B3 having two separated xyloses induced neurite outgrowth as like as nerve growth factor (NGF) in the rat pheochromocytoma cell line PC12, whereas acanthasteroside A1, having one xylose, did not induce neurite outgrowth. The acanthasteroside B3 induced neuritogenesis via the significant activation of p38 mitogen-activated protein kinase after the activation of the small G-protein Cdc42 rather than via Ras-MEK-ERK pathway that is predominantly activated by NGF. Following subcutaneous administration, acanthasteroside B3 attenuated cognitive impairment of senescence-accelerated mice (SAMP8) in two different cognitive tests. Liquid chromatography-mass spectrometry-assisted quantitative analysis demonstrated that acanthasteroside B3 could be transported into the brain via the circulatory system in mice. Thus, acanthasteroside B3 (and possibly B1) are a novel class of potential drug candidates for neurodegenerative diseases.

Inhibition of Rho-kinase ameliorates decreased spine density in the medial prefrontal cortex and methamphetamine-induced cognitive dysfunction in mice carrying schizophrenia-associated mutations of the Arhgap10 gene.

Copy-number variations in the ARHGAP10 gene encoding Rho GTPase-activating protein 10 are associated with schizophrenia. Model mice (Arhgap10 S490P/NHEJ mice) that carry "double-hit" mutations in the Arhgap10 gene mimic the schizophrenia in a Japanese patient, exhibiting altered spine density, methamphetamine-induced cognitive dysfunction, and activation of RhoA/Rho-kinase signaling. However, it remains unclear whether the activation of RhoA/Rho-kinase signaling due to schizophrenia-associated Arhgap10 mutations causes the phenotypes of these model mice. Here, we investigated the effects of fasudil, a brain permeable Rho-kinase inhibitor, on altered spine density in the medial prefrontal cortex (mPFC) and on methamphetamine-induced cognitive impairment in a touchscreen­based visual discrimination task in Arhgap10 S490P/NHEJ mice. Fasudil (20 mg/kg, intraperitoneal) suppressed the increased phosphorylation of myosin phosphatase-targeting subunit 1, a substrate of Rho-kinase, in the striatum and mPFC of Arhgap10 S490P/NHEJ mice. In addition, daily oral administration of fasudil (20 mg/kg/day) for 7 days ameliorated the reduced spine density of layer 2/3 pyramidal neurons in the mPFC. Moreover, fasudil (3-20 mg/kg, intraperitoneal) rescued the methamphetamine (0.3 mg/kg)-induced cognitive impairment of visual discrimination in Arhgap10 S490P/NHEJ mice. Our results suggest that Rho-kinase plays significant roles in the neuropathological changes in spine morphology and in the vulnerability of cognition to methamphetamine in mice with schizophrenia-associated Arhgap10 mutations.

Deficiency of kynurenine 3-monooxygenase exacerbates impairment of prepulse inhibition induced by phencyclidine.

Phencyclidine (PCP) causes mental symptoms that closely resemble schizophrenia through the inhibition of the glutamatergic system. The kynurenine (KYN) pathway (KP) generates metabolites that modulate glutamatergic systems such as kynurenic acid (KA), quinolinic acid (QA), and xanthurenic acid (XA). Kynurenine 3-monooxygenase (KMO) metabolizes KYN to 3-hydroxykynurenine (3-HK), an upstream metabolite of QA and XA. Clinical studies have reported lower KMO mRNA and higher KA levels in the postmortem brains of patients with schizophrenia and exacerbation of symptoms in schizophrenia by PCP. However, the association between KMO deficiency and PCP remains elusive. Here, we demonstrated that a non-effective dose of PCP induced impairment of prepulse inhibition (PPI) in KMO KO mice. KA levels were increased in the prefrontal cortex (PFC) and hippocampus (HIP) of KMO KO mice, but 3-HK levels were decreased. In wild-type C57BL/6 N mice, the PPI impairment induced by PCP is exacerbated by KA, while attenuated by 3-HK, QA and XA. Taken together, KMO KO mice were vulnerable to the PPI impairment induced by PCP through an increase in KA and a decrease in 3-HK, suggesting that an increase in the ratio of KA to 3-HK (QA and XA) may play an important role in the pathophysiology of schizophrenia.

Ginsenoside Re attenuates memory impairments in aged Klotho deficient mice via interactive modulations of angiotensin II AT1 receptor, Nrf2 and GPx-1 gene.

Ginseng is known to possess anti-aging potential. Klotho mutant mice exhibit phenotypes that resemble the phenotype of the human aging process. Similar to Klotho deficient mice, patients with chronic kidney disease (CKD) suffer vascular damage and cognitive impairment, which might upregulate the angiotensin II AT1 receptor. Since AT1 receptor expression was more pronounced than endothelin ET-1 expression in the hippocampus of aged Klotho deficient (±) mice, we focused on the AT1 receptor in this study. Ginsenoside Re (GRe), but not ginsenoside Rb1 (GRb1), significantly attenuated the increase in AT1 receptor expression in aged Klotho deficient mice. Both GRe and the AT1 receptor antagonist losartan failed to attenuate the decrease in phosphorylation of JAK2/STAT3 in aged Klotho deficient (±) mice but significantly activated nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated signaling. Both GRe and losartan attenuated the increased NADPH oxidase (NOX) activity and reactive oxygen species (ROS) in aged Klotho deficient mice. Furthermore, of all the antioxidant enzymes, GRe significantly increased glutathione peroxidase (GPx) activity. GRe significantly attenuated the reduced phosphorylation of ERK and CREB in GPx-1 knockout mice; however, genetic overexpression of GPx-1 did not significantly affect them in aged mice. Klotho-, Nrf2-, and GPx-1-immunoreactivities were co-localized in the same cells of the hippocampus in aged Klotho wild-type mice. Both the GPx inhibitor mercaptosuccinate and Nrf2 inhibitor brusatol counteracted the effects of GRe on all neurobehavioral impairments in aged Klotho deficient (±) mice. Our results suggest that GRe attenuates all alterations, such as AT1 receptor expression, NOX-, ROS-, and GPx-levels, and cognitive dysfunction in aged Klotho deficient (±) mice via upregulation of Nrf2/GPx-1/ERK/CREB signaling.

Loureirin C and Xanthoceraside Prevent Abnormal Behaviors Associated with Downregulation of Brain Derived Neurotrophic Factor and AKT/mTOR/CREB Signaling in the Prefrontal Cortex Induced by Chronic Corticosterone Exposure in Mice.

Brain derived neurotrophic factor (BDNF) is one of the most abundant neurotrophic factors, and its deficits are involved in the pathogenesis of major depressive disorders (MDD). Loureirin C (Lou C) is a compound derived from red resin extracted from the stems of Chinese dragon's blood. Xanthoceraside (Xan) is a triterpenoid saponin extracted from the husks of Xanthoceras sorbifolia Bunge. These compounds have neuroprotective effects through upregulation of BDNF. The present study aimed to evaluate whether Lou C and Xan attenuate abnormal behaviors induced by chronic corticosterone (CORT) administration. CORT was administered subcutaneously to mice for 3 weeks, and Lou C and Xan, dispensed orally once a day during the last 2 weeks of CORT administration. Chronic CORT administration induced abnormal behaviors such as prolonged starting latency in the open field test, decreased social interaction time in the social interaction test and prolonged latency to eat in the novelty suppressed feeding test. Chronic CORT administration decreased the expression levels of BDNF and the phosphorylation of protein kinase B (Akt), mammalian target of rapamycin (mTOR), and the cAMP response element binding protein (CREB) in the prefrontal cortex. Lou C and Xan dose-dependently prevented the abnormal behaviors and decreased the expression levels of BDNF and in phosphorylation of AKT, mTOR, and CREB in the prefrontal cortex of CORT mice. These results suggest that Lou C and Xan could be attractive candidates for pharmacotherapy of MDD at least in part, given their propensity to increase BDNF expression and phosphorylation of AKT, mTOR, and CREB.

Loureirin C and Xanthoceraside Attenuate Depression-Like Behaviors and Expression of Interleukin-17 in the Prefrontal Cortex Induced by Chronic Unpredictable Mild Stress in Mice.

Major depressive disorder (MDD) is the most prevalent and serious psychiatric disease involving inflammation. Loureirin C and Xanthoceraside are extracts of dragon's blood and Xanthoceras sorbifolia Bunge, respectively, which have neuroprotective and anti-inflammatory properties. In this study, we examined whether Loureirin C and Xanthoceraside attenuated depression-like behaviors and inflammation induced by chronic unpredicted mild stress (CUMS) in mice. Adult C57BL/6 J mice exposed to CUMS for 4 weeks showed depression-like behaviors characterized by hyperactivity in a novel environment, decreased interaction time in the social interaction test, prolongation of eating latency in the novelty suppressed feeding test, and increased immobility in the forced swimming test. CUMS increased the expression of interleukin-17 (IL-17) in the prefrontal cortex (PFC). One week after exposure to CUMS, the mice were treated with Loureirin C (0.64 mg/kg) or Xanthoceraside (1.28 mg/kg) once a day for 3 weeks during CUMS. Loureirin C and Xanthoceraside significantly attenuated CUMS-induced behavioral impairment. Furthermore, both Loureirin C and Xanthoceraside prevented IL-17 expression induced by CUMS in the PFC. This data suggests that Loureirin C and Xanthoceraside have antidepressant-like properties that may be associated with the inhibition of IL-17 expression.

Targeting α6GABAA receptors as a novel therapy for schizophrenia: A proof-of-concept preclinical study using various animal models.

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.

Effects of galantamine on social interaction impairments in cholecystokinin receptor-2 overexpression mice.

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.

Duloxetine attenuates pain in association with downregulation of platelet serotonin transporter in patients with burning mouth syndrome and atypical odontalgia.

OBJECTIVE: The aim of this study was evaluation of the association between severity of pain and expression of total or ubiquitinated serotonin transporter (SERT) protein in patients with burning mouth syndrome and atypical odontalgia (BMS/AO), who were treated by duloxetine. METHODS: Patients with BMS/AO were assessed for severity of pain using the visual analog scale (VAS), and expression of total and ubiquitinated SERT protein in platelets before (baseline) and 12 weeks after duloxetine-treatment. RESULTS: The expression of total and ubiquitinated SERT protein at baseline in all patients (n = 33) were higher and lower, respectively, compared to those in healthy controls. 12 weeks after duloxetine-treatment, there was no difference in the total SERT protein levels between patients (n = 21) and healthy controls. In the 16 patients who could be measured, mean VAS scores and total SERT protein levels were significantly decreased after the treatment, compared to those at baseline. There was tendency for a positive correlation between total SERT protein levels and VAS scores in these patients. CONCLUSIONS: Our findings indicate that duloxetine relieves pain in association with downregulation of platelet SERT expression in patients with BMS/AO.

Mice with exonic RELN deletion identified from a patient with schizophrenia have impaired visual discrimination learning and reversal learning in touchscreen operant tasks.

The Reelin gene (RELN) encodes a large extracellular protein, which has multiple roles in brain development and adult brain function. It activates a series of neuronal signal transduction pathways in the adult brain that function in synaptic plasticity, dendritic morphology, and cognitive function. To further investigate the roles of Reln in brain function, we generated a mouse line using the C57BL/6 J strain with the specific Reln deletion identified from a Japanese patient with schizophrenia (Reln-del mice). These mice exhibited abnormal sociality, but the pathophysiological significance of the Reln deletion for higher brain functions, such as learning and behavioral flexibility remains unclear. In this study, cognitive function in Reln-del mice was assessed using touchscreen-based visual discrimination (VD) and reversal learning (RL) tasks. Reln-del mice showed normal learning in the simple VD task, but the learning was delayed in the complex VD task as compared to their wild-type (WT) littermates. In the RL task, sessions were divided into early perseverative phase (sessions with <50% correct) and later learning phase (sessions with ≥50% correct). Reln-del mice showed normal perseveration but impaired relearning ability in both simple RL and complex RL task as compared to WT mice. These results suggest that Reln-del mice have impaired learning ability, but the behavioral flexibility is unaffected. Overall, the observed behavioral abnormalities in Reln-del mice suggest that this mouse model is a useful preclinical tool for investigating the neurobiological mechanism underlying cognitive impairments in schizophrenia and a therapeutic strategy.

Ouabain inhibitor rostafuroxin attenuates dextromethorphan-induced manic potential.

Dextromethorphan (DM) abuse produces mania-like symptoms in humans. ERK/Akt signaling activation involved in manic potential can be attenuated by the inhibition of ouabain-like cardiac steroids. In this study, increased phosphorylations of ERK/Akt and hyperlocomotion induced by DM (30 mg/kg, i.p./day × 7) were significantly protected by the ouabain inhibitor rostafuroxin (ROSTA), suggesting that DM induces the manic potential. ROSTA significantly attenuated DM-induced protein kinase C δ (PKCδ) phosphorylation, GluN2B (i.e., MDA receptor subunit) expression, and phospho-PKCδ/GluN2B interaction. DM instantly upregulated the nuclear factor erythroid-2-related factor 2 (Nrf2)-dependent system. However, DM reduced Nrf2 nuclear translocation, Nrf2 DNA binding activity, γ-glutamylcysteine mRNA expression, and subsequent GSH/GSSG level and enhanced oxidative parameters following 1-h of administration. ROSTA, PKCδ inhibitor rottlerin, and GluN2B inhibitor traxoprodil significantly attenuated DM-induced alterations in Nrf2-related redox parameters and locomotor activity induced by DM in wild-type mice. Importantly, in PKCδ knockout mice, DM failed to alter the above parameters. Further, ROSTA and traxoprodil also failed to enhance PKCδ depletion effect, suggesting that PKCδ is a critical target for the anti-manic potential of ROSTA or GluN2B antagonism. Our results suggest that ROSTA inhibits DM-induced manic potential by attenuating ERK/Akt activation, GluN2B/PKCδ signalings, and Nrf2-dependent system.