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Subchronic elevation of brain kynurenic acid augments amphetamine-induced locomotor response in mice. J Neural Transm (Vienna) 2011; 119:155-63. [PMID: 21904895 DOI: 10.1007/s00702-011-0706-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Accepted: 08/20/2011] [Indexed: 10/17/2022]
Abstract
The neuromodulating tryptophan metabolite kynurenic acid (KYNA) is increased in the brain of patients with schizophrenia. In the present study we investigate the spontaneous locomotor activity as well as the locomotor response to d-amphetamine [5 mg/kg, administered intraperitoneal (i.p.)] after increasing endogenous levels of brain KYNA in mice by acute (10 mg/kg, i.p., 60 min) or subchronic (100 mg/kg i.p., twice daily for 6 days) pretreatment with the blood-brain crossing precursor, L: -kynurenine. We found that an acute increase in the brain KYNA levels caused increased corner time and percent peripheral activity but did not change the d-amphetamine-induced locomotor response. In contrast, subchronic elevation of KYNA did not change the spontaneous locomotor activity but produced an exaggerated d-amphetamine-induced hyperlocomotion. These results cohere with clinical studies of patients with schizophrenia, where a potentiated DA release associated with exacerbation of positive symptoms has been observed following d-amphetamine administration. Present results further underscore KYNA as a possible mediator of the aberrant dopaminergic neurotransmission seen in schizophrenia.
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3-Hydroxykynurenine and clinical symptoms in first-episode neuroleptic-naive patients with schizophrenia. Int J Neuropsychopharmacol 2011; 14:756-67. [PMID: 21275080 PMCID: PMC3117924 DOI: 10.1017/s1461145710001689] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
One branch of the tryptophan catabolic cascade is the kynurenine pathway, which produces neurotoxic [3-hydroxykynurenine (3-OHKY), quinolinic acid] and neuroinhibitory (kynurenic acid) compounds. Kynurenic acid acts as a competitive antagonist at the glycine site of N-methyl-d-asparate receptors at high concentrations and as a non-competitive antagonist on the α7-nicotinic acetylcholine receptor at low concentrations. Kynurenine compounds also influence cognitive functions known to be disrupted in schizophrenia. Alterations in tryptophan metabolism are therefore of potential significance for the pathophysiology of this disorder. In this paper, tryptophan metabolites were measured from plasma using high-pressure liquid chromatography coupled with electrochemical coulometric array detection, and relationships were tested between these metabolic signatures and clinical symptoms for 25 first-episode neuroleptic-naive schizophrenia patients. Blood samples were collected and clinical and neurological symptoms were rated at baseline and again at 4 wk following initiation of treatment. Level of 3-OHKY and total clinical symptom scores were correlated when patients were unmedicated and neuroleptic-naive, and this relationship differed significantly from the correlation observed for patients 4 wk after beginning treatment. Baseline psychosis symptoms were predicted only by neurological symptoms. Moreover, baseline 3-OHKY predicted clinical change at 4 wk, with the lowest concentrations of 3-OHKY being associated with the greatest improvement in symptoms. Taken together, our findings suggest a neurotoxic product of tryptophan metabolism, 3-OHKY, predicts severity of clinical symptoms during the early phase of illness and before exposure to antipsychotic drugs. Baseline level of 3-OHKY may also predict the degree of clinical improvement following brief treatment with antipsychotics.
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Acute administration of typical and atypical antipsychotics reduces EEG γ power, but only the preclinical compound LY379268 reduces the ketamine-induced rise in γ power. Int J Neuropsychopharmacol 2011; 15:657-68. [PMID: 21733235 PMCID: PMC3353488 DOI: 10.1017/s1461145711000848] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
A single non-anaesthetic dose of ketamine, a non-competitive NMDA receptor (NMDAR) antagonist with hallucinogenic properties, induces cognitive impairment and psychosis, and aggravates schizophrenia symptoms in patients. In conscious rats an equivalent dose of ketamine induces key features of animal models of acute psychosis, including hyperlocomotor activity, deficits in prepulse inhibition and gating of auditory evoked potentials, and concomitantly increases the power of ongoing spontaneously occurring gamma (30-80 Hz) oscillations in the neocortex. This study investigated whether NMDAR antagonist-induced aberrant gamma oscillations could be modulated by acute treatment with typical and atypical antipsychotic drugs. Extradural electrodes were surgically implanted into the skull of adult male Wistar rats. After recovery, rats were subcutaneously administered either clozapine (1-5 mg/kg, n=7), haloperidol (0.05-0.25 mg/kg; n=8), LY379268 (a preclinical agonist at mGluR2/3 receptors: 0.3-3 mg/kg; n=5) or the appropriate vehicles, and 30 min later received ketamine (5 mg/kg s.c.). Quantitative measures of EEG gamma power and locomotor activity were assessed throughout the experiment. All three drugs significantly reduced the power of baseline EEG gamma oscillations by 30-50%, an effect most prominent after LY379268, and all inhibited ketamine-induced hyperlocomotor activity. However, only pretreatment with LY379268 attenuated trough-to-peak ketamine-induced gamma hyperactivity. These results demonstrate that typical and atypical antipsychotic drugs acutely reduce cortical gamma oscillations, an effect that may be related to their clinical efficacy.
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Naatanen R, Kujala T, Kreegipuu K, Carlson S, Escera C, Baldeweg T, Ponton C. The mismatch negativity: an index of cognitive decline in neuropsychiatric and neurological diseases and in ageing. Brain 2011; 134:3435-53. [DOI: 10.1093/brain/awr064] [Citation(s) in RCA: 159] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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Horton J, Millar A, Labelle A, Knott VJ. MMN responsivity to manipulations of frequency and duration deviants in chronic, clozapine-treated schizophrenia patients. Schizophr Res 2011; 126:202-11. [PMID: 21194893 DOI: 10.1016/j.schres.2010.11.028] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 11/25/2010] [Accepted: 11/30/2010] [Indexed: 11/18/2022]
Abstract
Event-related potential (ERP) probing of abnormal sensory processes in schizophrenia with the mismatch negativity (MMN) has shown impairments in auditory change detection, but knowledge of the acoustic features leading to this deficit is incomplete. Changes in the duration and frequency properties of sound stimuli result in diminished MMNs in schizophrenia but it is unclear as to whether this reduced responsiveness is seen with more subtle changes in sound frequency. In a sample of 19 healthy controls and 21 patients with chronic schizophrenia treated with clozapine, MMN was assessed in response to tone frequency changes of 5%, 10% and 20%, and to tone duration changes. Patients exhibited reduced amplitudes and shorter latencies than controls to all frequency changes, and attenuated amplitudes to tone duration increments and decrements. Clozapine dose was related to MMN, with increasing dose being positively associated with frequency-MMN amplitudes (10% ∆f, 20% ∆f) and negatively associated with the amplitude and latency of duration-MMNs. These data support the well-established findings of auditory sensory abnormality in schizophrenia and underscore the sensitivity of MMN to relatively small auditory change detection deficits that may appear to characterize chronic schizophrenia.
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Affiliation(s)
- Jemeen Horton
- Geriatrics/Integrated Forensic Program, Royal Ottawa Mental Health Centre, Ottawa, ON, Canada K1Z 7K4
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56
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Yadav PN, Abbas AI, Farrell MS, Setola V, Sciaky N, Huang XP, Kroeze WK, Crawford LK, Piel DA, Keiser MJ, Irwin JJ, Shoichet BK, Deneris ES, Gingrich J, Beck SG, Roth BL. The presynaptic component of the serotonergic system is required for clozapine's efficacy. Neuropsychopharmacology 2011; 36:638-51. [PMID: 21048700 PMCID: PMC3055689 DOI: 10.1038/npp.2010.195] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Clozapine, by virtue of its absence of extrapyramidal side effects and greater efficacy, revolutionized the treatment of schizophrenia, although the mechanisms underlying this exceptional activity remain controversial. Combining an unbiased cheminformatics and physical screening approach, we evaluated clozapine's activity at >2350 distinct molecular targets. Clozapine, and the closely related atypical antipsychotic drug olanzapine, interacted potently with a unique spectrum of molecular targets. This distinct pattern, which was not shared with the typical antipsychotic drug haloperidol, suggested that the serotonergic neuronal system was a key determinant of clozapine's actions. To test this hypothesis, we used pet1(-/-) mice, which are deficient in serotonergic presynaptic markers. We discovered that the antipsychotic-like properties of the atypical antipsychotic drugs clozapine and olanzapine were abolished in a pharmacological model that mimics NMDA-receptor hypofunction in pet1(-/-) mice, whereas haloperidol's efficacy was unaffected. These results show that clozapine's ability to normalize NMDA-receptor hypofunction, which is characteristic of schizophrenia, depends on an intact presynaptic serotonergic neuronal system.
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Affiliation(s)
- Prem N Yadav
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
| | - Atheir I Abbas
- Department of Biochemistry, Case Western Reserve University Medical School, Cleveland, OH, USA
| | - Martilias S Farrell
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
| | - Vincent Setola
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA,National Institute of Mental Heath Psychoactive Drug Screening Program, University of North Carolina, Chapel Hill, NC, USA
| | - Noah Sciaky
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
| | - Xi-Ping Huang
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA,National Institute of Mental Heath Psychoactive Drug Screening Program, University of North Carolina, Chapel Hill, NC, USA
| | - Wesley K Kroeze
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
| | - LaTasha K Crawford
- Department of Anesthesiology, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA, USA
| | - David A Piel
- Department of Anesthesiology, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA, USA
| | - Michael J Keiser
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - John J Irwin
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Brian K Shoichet
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Evan S Deneris
- Department of Neurosciences, Case Western Reserve University Medical School, Cleveland, OH, USA
| | - Jay Gingrich
- Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - Sheryl G Beck
- Department of Anesthesiology, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA, USA,Department of Anesthesiology, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA 19104, USA. Tel: +1 215 590 0651; Fax: +1 215 590 4107; E-mail:
| | - Bryan L Roth
- National Institute of Mental Heath Psychoactive Drug Screening Program, University of North Carolina, Chapel Hill, NC, USA,Departments of Pharmacology, Medicinal Chemistry and Psychiatry, Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC, USA,Department of Pharmacology, University of North Carolina, National Institute of Mental Heath Psychoactive Drug Screening Program, Chapel Hill, NC, 27516, USA. Tel: +1 919 966 7535; Fax: +1 919 843 5788; E-mail:
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Abstract
Growing evidence for glutamate abnormalities in schizophrenia support the development of novel antipsychotic agents targeting this system. Early studies investigating modulation of the glutamate system using glycine, D-serine and sarcosine in patients with schizophrenia have demonstrated significant effects, particularly on negative symptoms, conventionally thought to be refractory to antipsychotic drug treatment. Drugs targeting the glutamate system also have a completely different side-effect profile to dopamine D2 antagonists, with no propensity to extrapyramidal side effects, prolactinaemia or weight gain. It has been hypothesized that glutamatergic drugs may be of benefit to the 20-30% of individuals with schizophrenia who fail to show any response to dopaminergic agents, and may be particularly useful in the early stages of the illness, where they may be disease-modifying. A number of glutamatergic compounds have been reported as having promising results in phase II drug trials. If these reach the clinic, they will represent the first truly novel approach to pharmacotherapy in schizophrenia for more than 50 years.
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Affiliation(s)
- James M. Stone
- Experimental Medicine, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
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Clozapine and N-methyl-D-aspartate have positive modulatory actions on their respective discriminative stimulus properties in C57BL/6 mice. Eur J Pharmacol 2011; 650:579-85. [PMID: 20969851 DOI: 10.1016/j.ejphar.2010.10.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 09/30/2010] [Accepted: 10/06/2010] [Indexed: 11/21/2022]
Abstract
The impairment of N-Methyl-D-Aspartate receptors is thought to contribute to negative symptoms and cognitive deficits. In vitro studies suggest that atypical antipsychotic drugs like clozapine may help to alleviate these deficits by enhancing glutamatergic function. The present study examined the in vivo interaction of clozapine with N-Methyl D-aspartate by training one group of C57BL/6 mice to discrimination 2.5 mg/kg clozapine from vehicle and another group to discriminate 30 mg/kg N-Methyl D-aspartate from vehicle in a two-lever drug discrimination task. Cross-generalization testing revealed that N-Methyl D-aspartate (3-56 mg/kg) failed to substitute for clozapine in the clozapine-trained mice, while clozapine (0.625 mg/kg) produced partial substitution in the N-Methyl D-aspartate-trained mice. Interestingly, administration of a low, non-generalizing dose of each training drug in combination with the full range of doses of the alternate training drug produced full and dose-dependent substitution in both clozapine- and N-Methyl D-aspartate-trained mice. The α(1) antagonist prazosin fully and dose-dependently substituted for both clozapine and N-Methyl D-aspartate. These results suggest that the shared discriminative stimulus properties between clozapine and N-Methyl D-aspartate may be mediated through indirect mechanisms, possibly in part through α(1) adrenergic antagonism.
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Iasevoli F, Tomasetti C, Marmo F, Bravi D, Arnt J, de Bartolomeis A. Divergent acute and chronic modulation of glutamatergic postsynaptic density genes expression by the antipsychotics haloperidol and sertindole. Psychopharmacology (Berl) 2010; 212:329-44. [PMID: 20652539 DOI: 10.1007/s00213-010-1954-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 07/09/2010] [Indexed: 10/19/2022]
Abstract
RATIONALE A pivotal role for glutamate in the pathophysiology and treatment of schizophrenia has been suggested. Few reports have investigated the impact of antipsychotics on postsynaptic density (PSD) molecules involved in glutamatergic transmission and synaptic remodeling. Homer is a key PSD molecule putatively implicated in schizophrenia. OBJECTIVES We studied the effect, in acute and chronic paradigms, of a first and a second generation antipsychotic (haloperidol and sertindole, respectively) on the expression of Homer1a and Homer-interacting PSD molecules. RESULTS In the acute paradigm, Homer1a expression was induced by haloperidol but not sertindole in the striatum, consistent with the less propensity of sertindole to affect nigrostriatal neurotransmission. The profile of expression of two other inducible genes, Ania3 and Arc, was highly similar to Homer1a. In the cortex, haloperidol reduced Homer1a and induced Ania3. In the chronic paradigm, striatal expression of Homer1a and Ania3 resembled that observed in the acute paradigm. In the cortex, haloperidol induced Homer1a, while sertindole did not. Homer1b expression was increased by haloperidol in the striatum and cortex whereas sertindole selectively induced Homer1b in the cortex. The expression of mGluR5 was increased by both antipsychotics. A modulation by haloperidol was also seen for PSD-95 and αCaMKII. CONCLUSIONS These results suggest that haloperidol and sertindole may significantly modulate glutamatergic transcripts of the postsynaptic density. Sertindole induces constitutive genes in the cortex predominantly, which may correlate with its propensity to improve cognitive functions. Haloperidol preferentially modulates gene expression in the striatum, consistent with its action at nigrostriatal projections and its propensity to give motor side effects.
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Affiliation(s)
- Felice Iasevoli
- Laboratory of Molecular Psychiatry and Psychopharmacotherapeutics, Section of Psychiatry, Department of Neuroscience, University School of Medicine Federico II, Edificio 18, Via Pansini 5, 80131, Naples, Italy
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60
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Stone JM, Raffin M, Morrison P, McGuire PK. Review: The biological basis of antipsychotic response in schizophrenia. J Psychopharmacol 2010; 24:953-64. [PMID: 19939865 DOI: 10.1177/0269881109106959] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Schizophrenia is a severe mental illness affecting approximately 1% of the population worldwide. Antipsychotic drugs are effective in symptom control in up to two-thirds of patients, but in at least one-third of patients the response is poor. The reason for this is not clear, but one possibility is that good and poor responders have different neurochemical pathologies, and may therefore benefit from different treatment approaches. In this selective review we summarise research findings investigating the biological differences between patients with schizophrenia who show a good or a poor response to treatment with antipsychotic drugs.
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Affiliation(s)
- James M Stone
- Institute of Psychiatry, King's College London, London SE5 8AF, UK.
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61
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D-cycloserine inhibits the development and the expression of locomotor sensitization to amphetamine in rats. Behav Pharmacol 2010; 21:165-70. [DOI: 10.1097/fbp.0b013e32833a5bcb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Olsson SK, Samuelsson M, Saetre P, Lindström L, Jönsson EG, Nordin C, Engberg G, Erhardt S, Landén M. Elevated levels of kynurenic acid in the cerebrospinal fluid of patients with bipolar disorder. J Psychiatry Neurosci 2010; 35:195-9. [PMID: 20420770 PMCID: PMC2861136 DOI: 10.1503/jpn.090180] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
BACKGROUND Patients with schizophrenia show elevated brain levels of the neuroactive tryptophan metabolite kynurenic acid (KYNA). This astrocyte-derived mediator acts as a neuroprotectant and modulates sensory gating and cognitive function. We measured the levels of KYNA in the cerebrospinal fluid (CSF) of patients with bipolar disorder and healthy volunteers to investigate the putative involvement of KYNA in bipolar disorder. METHODS We obtained CSF by lumbar puncture from 23 healthy men and 31 euthymic men with bipolar disorder. We analyzed the samples using high-performance liquid chromatography. RESULTS Patients with bipolar disorder had increased levels of KYNA in their CSF compared with healthy volunteers (1.71 nM, standard error of the mean [SEM] 0.13 v. 1.13 nM, SEM 0.09; p = 0.002. The levels of KYNA were positively correlated with age among bipolar patients but not healthy volunteers. LIMITATIONS The influence of ongoing drug treatment among patients cannot be ruled out. We conducted our study during the euthymic phase of the disease. CONCLUSION Brain KYNA levels are increased in euthymic men with bipolar disorder. In addition, KYNA levels increased with age in these patients. These findings indicate shared mechanisms between bipolar disorder and schizophrenia. Elevated levels of brain KYNA may provide further insight to the pathophysiology and progression of bipolar disorder.
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Affiliation(s)
| | | | | | | | | | | | | | - Sophie Erhardt
- Correspondence to: Dr. S. Erhardt, Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden; fax 46 8 31 06 22;
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Linderholm K, Powell S, Olsson E, Holtze M, Snodgrass R, Erhardt S. Role of the NMDA-receptor in Prepulse Inhibition in the Rat. Int J Tryptophan Res 2010; 3:1-12. [PMID: 22084584 PMCID: PMC3195246 DOI: 10.4137/ijtr.s4260] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Kynurenic acid (KYNA) is an endogenous metabolite of tryptophan. Studies have revealed increased brain KYNA levels in patients with schizophrenia. Prepulse inhibition (PPI) is a behavioral model for sensorimotor gating and found to be reduced in schizophrenia. Previous studies have shown that pharmacologically elevated brain KYNA levels disrupt PPI in the rat. The aim of the present study was to investigate the receptor(s) involved in this effect. Rats were treated with different drugs selectively blocking each of the sites that KYNA antagonizes, namely the glutamate recognition site of the N-methyl-D-aspartate receptor (NMDAR), the α7* nicotinic acetylcholine receptor (α7nAChR) and the glycine site of the NMDAR. Kynurenine (200 mg/kg) was given to replicate the effects of increased levels of KYNA on PPI. In order to block the glutamate recognition site of the NMDAR, CGS 19755 (10 mg/kg) or SDZ 220–581 (2.5 mg/kg) were administered and to antagonize the α7nAChR methyllycaconitine (MLA; 6 mg/kg) was given. L-701,324 (1 and 4 mg/kg) or 4-Chloro-kynurenine (4-Cl-KYN; 25, 50 and 100 mg/kg), a drug in situ converted to 7-Chloro-kynurenic acid, were used to block the glycine-site of the NMDAR. Administration of SDZ 220-581 or CGS 19755 was associated with a robust reduction in PPI, whereas L-701,324, 4-Cl-KYN or MLA failed to alter PPI. Kynurenine increased brain KYNA levels 5-fold and tended to decrease PPI. The present study suggests that neither antagonism of the glycine-site of the NMDA receptor nor antagonism of the α7nAChR disrupts PPI, rather with regard to the effects of KYNA, blockade of the glutamate recognition-site is necessary to reduce PPI.
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Affiliation(s)
- Klas Linderholm
- Dept. of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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Ishii D, Matsuzawa D, Kanahara N, Matsuda S, Sutoh C, Ohtsuka H, Nakazawa K, Kohno M, Hashimoto K, Iyo M, Shimizu E. Effects of aripiprazole on MK-801-induced prepulse inhibition deficits and mitogen-activated protein kinase signal transduction pathway. Neurosci Lett 2010; 471:53-7. [PMID: 20083164 DOI: 10.1016/j.neulet.2010.01.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Revised: 01/07/2010] [Accepted: 01/08/2010] [Indexed: 10/20/2022]
Abstract
Based on NMDA hypofunction hypothesis for negative symptoms and cognitive deficits in schizophrenia, MK-801-induced animal models of schizophrenia may help us understand the different effects between typical and atypical antipsychotics. On the other hand, the mitogen-activated protein kinase (MAPK) signaling pathways may participate in antipsychotic actions. The aim of this study was to investigate the effects of aripiprazole on MK-801-induced prepulse inhibition (PPI) disruption and MAPK phosphorylation in mice. To clarify the effects of aripiprazole on MK-801-induced PPI disruption, we measured PPI of 51 ddY male mice after aripiprazole was administered 15 min prior to the injection of MK-801, and measured activation of cytosol and nuclear MAPK phosphorylation by western blotting. Aripiprazole (4.0 mg/kg) significantly reversed the MK-801 (0.15 mg/kg)-induced PPI deficits. Pretreatment of aripiprazole (40 mg/kg) had a tendency to suppress MK-801 (1.0 mg/kg)-induced pMEK/MEK (Ser218/222) activation. In addition, aripiprazole treatment showed a significant decrease of pERK/ERK. Our data suggested that aripiprazole may reverse MK-801-induced PPI deficits through regulation of MAPK phosphorylation in the same way as the atypical antipsychotic drug, clozapine.
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Affiliation(s)
- Daisuke Ishii
- Department of Integrative Neurophysiology, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chiba 260-8670, Japan
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Erhardt S, Olsson SK, Engberg G. Pharmacological manipulation of kynurenic acid: potential in the treatment of psychiatric disorders. CNS Drugs 2009; 23:91-101. [PMID: 19173370 DOI: 10.2165/00023210-200923020-00001] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The kynurenine pathway constitutes the main route of tryptophan degradation and generates the production of several neuroactive compounds; quinolinic acid is an excitotoxic NMDA receptor agonist, 3-hydroxykynurenine is a free-radical generator and kynurenic acid (KYNA) is an antagonist at glutamate and nicotinic receptors. In low micromolar concentrations, KYNA blocks the glycine site of the NMDA receptor and the nicotinic alpha(7) acetylcholine receptor. Knowledge regarding kynurenine metabolites and their involvement in neurophysiological processes has increased dramatically in recent years. In particular, endogenous KYNA appears to tightly control firing of midbrain dopamine neurons and to be involved in cognitive functions. Thus, decreased endogenous levels of rat brain KYNA have been found to reduce firing of these neurons, and mice with a targeted deletion of kynurenine aminotransferase II display low endogenous brain KYNA levels concomitant with an increased performance in cognitive tests. It is also suggested that kynurenines participate in the pathophysiology of psychiatric disorders. Thus, elevated levels of KYNA have been found in the CSF as well as in the post-mortem brain of patients with schizophrenia. Advantages in understanding how kynurenines can be pharmacologically manipulated may provide new possibilities in the treatment of psychiatric disorders, such as schizophrenia.
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Affiliation(s)
- Sophie Erhardt
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
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