G B Baker

University of Alberta, Edmonton, Alberta, Canada

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Publications (415)1397.59 Total impact

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    ABSTRACT: B y modulating the "glutamate-NO (nitric oxide)-cGMP" pathway," a new paradigm for the treatment of schizophrenia seems to arise. Indeed, our group has recently pub-lished a double-blind placebo (PLB) con-trolled trial showing that an infusion of sodium nitroprusside (SNP), a nitric oxide donor, improved positive, negative, anxiety, and depressive symptoms of schizophrenic patients in a matter of hours. 1 During this study, it seemed of interest to test the idea that SNP might also be effective in treating cognitive symptoms found in schizophrenia. For this purpose, it was performed, in the same subjects just mentioned, a pilot study where the patients were evaluated by a battery of cognitive tests on 2 occasions: 1 hour be-fore the start of SNP or PLB infusion and at 8 hours after the end of SNP or PLB infusion. Twenty-four patients agreed to partici-pate and were assessed for eligibility; 4 sub-jects subsequently refused to participate, and 20 individuals were randomized to receive either SNP or placebo. Two subjects from the SNP group refused to participate in the sec-ond cognitive evaluation (cognitive evaluation at 8 hours after the end of the SNP infusion). The other 18 participants who were random-ized completed all the study procedures. The SNP was administered as an endovenous infusion of 0 . 5 μg/kg per min-ute for 4 hours. The placebo was a 5% glu-cose solution that was endovenous infused over the same length of time. The following cognitive tests were con-ducted: (a) Stroop Color Word Test (SCWT) is a test to assess selective attention. Two cards instead of the 3 cards originally pro-posed by Stroop were used, following the procedure used by Liddle and Morris. 2 On the first card 100 words designating 5 colors, printed in black, were used; and on the sec-ond card, 100 words for the same colors, printed in colors incongruent with the des-ignation were used. The task was to read card 1 and designate the colors of card 2. Time spent on the task was measured in seconds and number of errors committed, according to the method proposed by Seabra (1987). (b) N-Back is a test to assess work-ing memory. It lasts about 6 minutes and consists of examining a series of numbers where it is required, at varying intervals, to report the number seen "n" positions back in the sequence. A printed version of the test on laminated cards was used in this study, with 2 distinct blocks presented in-terchangeably. The first and the third blocks contain 5 questions each about the last num-ber seen ("0-Back," task control), and the sec-ond and fourth blocks contain 5 questions each about which number was submitted before the last 2 cards ("2-Back"). The num-ber of errors made during the task was com-puted. (c) FAS (the Verbal Fluency Test) is a test widely used in the literature to measure verbal fluency, which is known to be impaired in schizophrenic patients. The task consists of a period of 3 minutes (1 minute for each letter—F, A, and S) where the volunteer must produce the largest number of words begin-ning with those letters. Brand names, proper names, or variations from the same root (eg, words like fall and fallen) are not allowed. Data were analyzed using the Statistical Package for the Social Sciences (SPSS 17·0). For the SCWT, N-Back, and the FAS scores, separate analyses of variance (ANOVAs) for repeated measures were carried out, with treatment (SNP/PLB) and time (every point of evaluation) as factors. If the ANOVAs were significant, a paired 2-tailed t test was per-formed, considering the groups independently. The following results were found: (a) SCWT—the ANOVA for repeated mea-sures concerning card 1 reading time showed an effect of the time factor (F = 6.98, df = 1–15, P = 0.02), but not drug (F = 1.46, df = 1–15, P = 0.24) and no interaction between time and drug (F = 0.03, df = 1–15, P = 0.85). The analysis of the number of errors on card 1 showed no effect of time (F = 2.4, df = 1–15, P = 0.14), drug (F = 0.18, df = 1–15, P = 0.68), or interaction between time and drug (F = 0.03, df = 1–15, P = 0.86). An interac-tion between time and drug was found for the number of errors on naming incongru-ent colors on card 2 (F = 5.54, df = 1–15, P = 0.03), but no effect of time (F = 0.57, df = 1–15, P = 0.46) or of drug alone (F = 0.03, df = 1–15, P = 0.85). Regarding the time for naming incongruent colors, the ANOVA for repeated measures showed no effect of time (F = 0.02, df = 1–15, P = 0.89), drug (F = 0.71, df = 1–15, P = 0.42), or in-teraction between them (F = 2.32, df = 1–15, P = 0.15). In situations where the ANOVA for repeated measures identified some in-teraction, the paired t test was performed, considering the groups independently. The paired t test for the 2 groups individually (SNP and PLB) showed that those patients who received SNP made fewer errors in the second evaluation of naming incongruent colors, but those who received PLB did not. (b) FAS—the ANOVA for repeated measures showed an effect of time (F = 9.37, df = 1–16, P = 0.01), but not of drug (F = 0.08, df = 1–16, P = 0.78) and no interaction between time and drug (F = 0.03, df = 1–16, P = 0.85). (c) N-Back—the ANOVA for repeated mea-sures identified an effect of time (F = 7.63, df = 1–14, P = 0·01), drug (F = 7.76, df = 1–14, P = 0.01), and also an interaction be-tween these 2 (F = 15.24, df = 1–14, P < 0.01). Thus, the paired t test was conducted for the SNP and PLB groups alone, which showed that those who received the SNP infusion pre-sented significant improvement in congnitive performance, whereas those who received the PLB infusion did not (Table 1). To our knowledge, this is the first time that improvements on executive functions that are frequently impaired in patients with schizophrenia were shown after SNP admin-istration. The improvement in SCWT and N-back performance that was observed in the SNP group, but not in the PLB group, suggests that treatment with SNP had an impact on patients cognitive functioning by improving selective attention 3 and work-ing memory 4 deficits. These beneficial effects could be ex-plained through SNP capacity, as a NO do-nor, to act by increasing the concentrations of the second messenger cGMP and medi-ating the neuronal communication in the CNS (central nervous system). 5,6 In this way, NO has been shown to influence learning and memory. 7 NO donors such as SNP have been found to stimulate neuronal growth in vitro 8 and have been proposed as potential new drugs to treat patients with age-related neurodegenerative disease such as Alzheimer disease. 9,10 On the other hand, too much NO could produce neurotoxicity due to accumu-lation of its toxic metabolite, peroxynitrite. 11 The small amount of patients studied is the limitation of this work. Future studies with a larger number of patients are needed. The usual NPS safe dose rate used to treat hypertension is 0.5 to 10 μg/kg per minute. Therefore, we decide to work with its low-est dose to minimize cardiovascular effects. Indeed, no clear effect of NPS on the vascu-lar system was observed (these results have been discussed elsewhere). 1 Further works should investigate the effects of multiple and different doses of SNP and other rele-vant issues like how frequently do we have to administer SNP to sustain its effect in long-term. To minimize possible learning effects, cognitive tests were performed only on 2 occasions. To avoid confounding LETTER TO THE EDITORS Journal of Clinical Psychopharmacology • Volume 35, Number 1, February 2015 www.psychopharmacology.com 1 Copyright © 2014 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. factors from demographic and clinical vari-ables, the selection and pairing of subjects were performed carefully and showed no differences between the 2 groups in any of the parameters evaluated (these results have been discussed elsewhere). 1 Despite the cognitive deficits being considered as the strongest predictors of long-term functional recovery in patients with schizophrenia, they have been among the symptoms most refractory to the treat-ment by both second-and first-generation antipsychotics. 12,13 Perhaps, the develop-ment of drugs that enhance NO levels, such as SNP, could be a productive target to pur-sue in the development of the next genera-tion of antipsychotic drugs. However, the findings here reported are modest and need to be confirmed for future studies. ACKNOWLEDGMENTS The authors thank their respective universities for the continuous support and Dr Judy Baker for the editorial and secretarial assistance.
    Journal of clinical psychopharmacology 02/2015; 35(1):1. · 5.09 Impact Factor
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    ABSTRACT: Recently, we found a rapid and long-lasting improvement of symptoms in schizophrenic patients on antipsychotics after a single four-hour infusion of sodium nitroprusside (SNP), a nitric oxide (NO) donor with a short half-life. This improvement persisted for up to 4 weeks. Because these patients remained on antipsychotics after infusion of SNP was finished, the question arises about whether this improvement was due to SNP itself. We have now investigated whether SNP, alone, can produce preventive antipsychotic effects in rats treated with ketamine (KET). 56 adult rats divided into 7 groups were infused with SNP 4 mg/kg, KET 25 mg/kg, or saline as follows: group1 — saline, group2 — SNP, group3 — KET, group4 — KET 12 h after SNP, group5 — KET 1 day after SNP, group6 — KET 2 days after SNP, and group7 — KET 1 week after SNP. The animals were filmed in an open field arena for 30 min and the videos were later analyzed by ANY-Maze software to measure activity and stereotypy. SNP significantly prevented the emergence of hyperactivity induced by KET when it was administered for up to 1 week before KET, and prevented the emergence of stereotypies when it was administered for up to 1 day before KET. These findings in rats, which have an even faster metabolic rate than humans, suggest that the long-lasting effects observed in our clinical trial with SNP in humans could have been due to SNP itself, and indicate for the first time that SNP may present preventive antipsychotic effects.
    Schizophrenia Research 01/2015; · 4.43 Impact Factor
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    ABSTRACT: Increasing evidence suggests that the tetracycline antibiotic minocycline has neuroprotective effects and is a potential treatment for schizophrenia. However, the mechanisms of action of minocycline in the CNS remain elusive. The aim of this study was to investigate the effects of minocycline on brain morphology and cerebral perfusion in patients with recent-onset schizophrenia after 12 months of a randomized double-blind, placebo-controlled clinical trial of minocycline add-on treatment. This study included 24 outpatients with recent-onset schizophrenia randomized for 12 months of adjuvant treatment with minocycline (200 mg/d) or placebo. MRI (1.5 T) and [ 99m Tc]-ECD SPECT brain scans were performed at the end of the 12-month of trial. Between-condition comparisons of SPECT and MRI brain images were performed using statistical parametric mapping and analyzed by voxel-based morphometry (VBM). Minocycline adjuvant treatment significantly reduced positive and negative symptoms when compared with placebo. The VBM analysis of MRI scans showed that the patients in the placebo group had significant lower gray matter volumes in the midposterior cingulate cortex and in the precentral gyrus in comparison with the patients in the minocycline group. In addition, a decreased ECD uptake in the minocycline condition was observed in fronto-temporal areas. These results suggest that minocycline may protect against gray matter loss and modulate fronto-temporal areas involved in the pathophysiology of schizophrenia. Furthermore, minocycline add-on treatment may be a potential treatment in the early stages of schizophrenia and may ameliorate clinical deterioration and brain alterations observed in this period.
    Schizophrenia Research 12/2014; 161(2-3). · 4.43 Impact Factor
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    ABSTRACT: ZET: fiizofreni için yeni tedavi stratejileri olarak nitrik oksit modülasyonu Antipsikotik ilaç gelifltirilmesindeki son ilerlemelere ra¤-men, flizofreninin farmakolojik yönetimi görece yetersiz kalmaktad›r. Santral nitrik oksit modülasyonuna dair artan kan›tlar flizofreni tedavisi için yeni bir tedavi stratejisi suna-bilir. Bu nedenle, bu editöryal yaz›da flizofreni ve antipsiko-tik ilaçlar›n mekanizmas› ile santral nitrik oksit patofizyolo-jisi iliflkisi anlat›lmaya çal›fl›lmaktad›r. Nitrik oksit modülas-yonunun yeni stratejileri flizofreni için potansiyel bir farma-koterapi yöntemi olarak karfl›m›zda durmaktad›r.
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    Schizophrenia Research 11/2014; · 4.43 Impact Factor
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    Journal of clinical psychopharmacology 09/2014; · 5.09 Impact Factor
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    ABSTRACT: Background Neuropsychiatric disorders during HIV/AIDS are common although the contribution of HIV-1 infection within the brain, and in particular individual HIV-1 proteins, to the development of these brain disorders is unknown. Herein, an in vivo transgenic mouse model was generated in which the HIV-1 Nef protein was expressed in microglia cells, permitting investigation of neurobehavioral phenotypes and associated cellular and molecular properties. Methods Transgenic (Tg) mice that expressed full length HIV-1 nef under the control of the c-fms promoter and wildtype (Wt) littermates were investigated using different measures of neurobehavioral performance including locomotory, forced swim (FST), elevated plus maze (EPM) and T-maze tests. Host gene and transgene expression were assessed by RT-PCR, immunoblotting, enzymatic activity and immunohistochemistry. Biogenic amine levels were measured by HPLC with electrochemical detection. Results Tg animals exhibited Nef expression in brain microglia and cultured macrophages. Tg males displayed hyperactive behaviors including augmented locomotor activity, decreased immobility in the FST and increased open-arm EPM exploration compared to Wt littermates (p<0.05). Tg animals showed increased CCL2 expression with concurrent IFN-α suppression in striatum compared with Wt littermates (p<0.05). Dopamine levels, MAO activity and the dopamine transporter (DAT) expression were reduced in the striatum of Tg animals (p<0.05). Conclusions HIV-1 Nef expression in microglia induced CCL2 expression together with disrupting striatal dopaminergic transmission, resulting in hyperactive behaviors which are observed in mania and other psychiatric comorbidities among HIV-infected persons. These findings emphasize the selective effects of individual viral proteins in the brain and their participation in neuropathogenesis.
    Brain Behavior and Immunity 08/2014; · 6.13 Impact Factor
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    ABSTRACT: The progesterone derivative allopregnanolone (ALLO) is one of the most widely studied compounds among neurosteroids. Through interactions with GABA-A receptors expressed by neurons and glial cells, ALLO has been shown to affect diverse aspects of neural cell physiology, including cell proliferation and survival, migration, and gene expression. Recent data point to important roles for ALLO in different neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and multiple sclerosis (MS). Dysregulation in ALLO biosynthesis pathways has been reported in brain tissue from MS patients as well as in the central nervous system (CNS) tissue derived from MS animal models. Administration of ALLO has been shown to ameliorate neurobehavioral deficits together with neuropathology and inflammation in the CNS of animals with autoimmune demyelination. These findings are in line with previous reports indicating growth- and differentiation-promoting actions of ALLO on neurons and glial cells as well as its neuroprotective effects in the context of other CNS diseases. Nonetheless, these findings have also raised the possibility that ALLO might influence leukocyte biology and associated neuroinflammatory mechanisms independent of its neuroregenerative properties. Herein, we review the current knowledge regarding the role of ALLO in the pathogenesis of MS, and discuss the potential cellular and molecular pathways that might be influenced by ALLO in the context of disease.
    Frontiers in Cellular Neuroscience 06/2014; 8:134. · 4.18 Impact Factor
    This article is viewable in ResearchGate's enriched format
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    ABSTRACT: Interactions between neurotransmitters and the immune system represent new prospects for understanding neuroinflammation and subsequent neurological disease. γ-amino butyric acid (GABA) is the chief inhibitory neurotransmitter but its actions on immune pathways in the brain are unclear. In the present study, we investigated GABAergic transport in conjunction with neuroinflammation in models of multiple sclerosis (MS). Protein and mRNA levels of γ-amino butyric acid transporter 2 (GAT-2) were examined in cerebral white matter from MS and control (Non-MS) patients, in cultured human macrophages, microglia and astrocytes, and in spinal cords from mice with and without experimental autoimmune encephalomyelitis (EAE) using western blotting, immunocytochemistry and quantitative real-time polymerase chain reaction (qRT-PCR). GABA levels were measured by HPLC. The GAT-2's expression was increased in multiple sclerosis (MS) patients' (n=6) white matter, particularly in macrophage lineage cells, compared to Non-MS patients (n=6) (p<0.05). Interferon-γ (IFN-γ) stimulation of human macrophage lineage cells induced GAT-2 expression and reduced extracellular GABA levels (p<0.05) but soluble GABA treatment suppressed HLA-DRα, GAT-2 and XBP-1/s expression in stimulated macrophage lineage cells (p<0.05). Similarly, the synthetic allopregnanolone analogue, ganaxolone (GNX), repressed GAT-2, JAK-1 and STAT-1 expression in activated macrophage lineage cells (p<0.05). In vivo GNX treatment reduced Gat-2, Cd3ε, MhcII, and Xbp-1/s expression in spinal cords following EAE induction (p<0.05), which was correlated with improved neurobehavioral outcomes and reduced neuroinflammation, demyelination and axonal injury. These findings highlight altered GABAergic transport through GAT-2 induction during neuroinflammation. GABA transport and neuroinflammation are closely coupled but regulated by GNX, pointing to GABAergic pathways as therapeutic targets in neuroinflammatory diseases.
    Neuroscience 05/2014; · 3.33 Impact Factor
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    ABSTRACT: Primary human fetal neurons and astrocytes (HFNs and HFAs, respectively) provide relevant cell types with which to study in vitro the mechanisms involved in various human neurological diseases, such as multiple sclerosis, Parkinson's disease, and Alzheimer's disease. However, the limited availability of human fetal cells poses a significant problem for the study of these diseases when a human cell model system is required. Thus, generating a readily available alternative cell source with the essential features of human neurons and astrocytes is necessary. The human teratoma-derived NTera2/D1 (NT2) cell line is a promising tool from which both neuronal and glial cells can be generated. Nevertheless, a direct comparison of NT2 neurons and primary HFNs in terms of their morphology physiological and chemical properties is still missing. This study directly compares NT2-derived neurons and primary HFNs using immunocytochemistry, confocal calcium imaging, high-performance liquid chromatography, and high-content analysis techniques. We investigated the morphological similarities and differences, levels of relevant amino acids, and internal calcium fluctuations in response to certain neurotransmitters/stimuli. We also compared NT2-derived astrocytes and HFAs. In most of the parameters tested, both neuronal and astrocytic cell types exhibited similarities to primary human fetal neurons and astrocytes. NT2-derived neurons and astrocytes are reliable in vitro tools and a renewable cell source that can serve as a valid alternative to HFNs/HFAs for mechanistic studies of neurological diseases. © 2014 Wiley Periodicals, Inc.
    Journal of Neuroscience Research 05/2014; · 2.73 Impact Factor
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    ABSTRACT: Despite decades of study, the etiology and physiopathology of schizophrenia remain unknown. Recent evidence suggests that nitric oxide (NO) may be implicated in schizophrenia. NO is a gas that mediates the release of neurotransmitters, learning, memory, and neurodevelopment. Studies investigating the role of NO in patients with schizophrenia found evidence that points to a disruption in NO-mediated neurotransmission. Therefore, we investigated the effects of sodium nitroprusside, a NO donor, as an add- on treatment for patients with schizophrenia.
    Schizophrenia Research 04/2014; 153(1):1-384. · 4.43 Impact Factor
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    ABSTRACT: Phenelzine, a non-selective irreversible inhibitor of monoamine oxidase (MAO), has been used in the treatment of depression and anxiety disorders for several decades. It is a unique inhibitor of MAO as it is also a substrate for MAO, with one of the metabolites being β-phenylethylidenehydrazine (PEH), and it also inhibits several transaminases (e.g. GABA transaminase) in the brain when administered i.p. to rats. Administration of either phenelzine or PEH to rats has been reported to produce dramatic increases in rat brain levels of GABA and alanine while reducing levels of glutamine; these effects are abolished for phenelzine, but not for PEH, when the animals are pre-treated with another MAO inhibitor, suggesting that they are mediated by the MAO-catalyzed formation of PEH from phenelzine. In the present report, we have found that phenelzine and E-and Z- geometric isomers of PEH significantly increased rat whole brain concentrations of L-tyrosine. In a time-response study, acute administration of phenelzine, E-PEH and Z-PEH (30mg/kgi.p.) elevated rat whole brain L-tyrosine levels at 3 and 6hours following injection, reaching approximately 265-305% of vehicle-treated controls at 3hours. To determine whether the effect on L-tyrosine is MAO-dependent, animals were pre-treated with the non-selective MAO inhibitor tranylcypromine (1mg/kgi.p.) prior to administration of phenelzine, racemic PEH or vehicle controls. This pre-treatment reversed the effects of phenelzine, but not of PEH, on brain L-tyrosine levels, suggesting that the tyrosine-elevating property of phenelzine is largely the result of its active metabolite PEH. These results are discussed in relation to possible therapeutic applications of these drugs.
    Progress in Neuro-Psychopharmacology and Biological Psychiatry 03/2014; · 4.03 Impact Factor
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    ABSTRACT: Converging evidence from clinical, preclinical, neuroimaging, and genetic research implicates dopamine neurotransmission in the pathophysiology of attention deficit hyperactivity disorder(ADHD). In-vivo neuroreceptor imaging evidence also suggests alterations in the dopamine system in ADHD, however, the nature and behavioural significance of those have not yet been established. Here, we investigated striatal dopaminergic function in ADHD using [(11)C]raclopride PET with a d-amphetamine challenge. We also examined the relationship of striatal dopamine responses to ADHD symptoms and neurocognitive function. Fifteen treatment-free, non-comorbid adult males with ADHD (age: 29.87±8.65) and 18 healthy male controls (age: 25.44±6.77) underwent two PET scans: one following a lactose placebo and the other following d-amphetamine (0.3 mg/kg, p.o.), administered double-blind and in random order counterbalanced across groups. In a separate session without a drug, participants performed a battery of neurocognitive tests. Relative to the healthy controls, the ADHD patients, as a group, showed greater d-amphetamine-induced decreases in striatal [(11)C]raclopride binding and performed more poorly on measures of response inhibition. Across groups, a greater magnitude of d-amphetamine-induced change in [(11)C]raclopride binding potential was associated with poorer performance on measures of response inhibition and ADHD symptoms. Our findings suggest an augmented striatal dopaminergic response in treatment-naïve ADHD. Though in contrast to results of a previous study, this finding appears consistent with a model proposing exaggerated phasic dopamine release in ADHD. A susceptibility to increased phasic dopamine responsivity may contribute to such characteristics of ADHD as poor inhibition and impulsivity.Neuropsychopharmacology accepted article preview online, 30 December 2013. doi:10.1038/npp.2013.349.
    Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 12/2013; · 8.68 Impact Factor
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    ABSTRACT: Not everyone who tries addictive drugs develops a substance use disorder. One of the best predictors of risk is a family history (FH) of substance use problems. In part, this might reflect perturbed mesolimbic dopamine responses. We measured amphetamine-induced changes in [(11)C]raclopride binding in 1) high-risk young adults with a multigenerational FH of substance use disorders (n = 16); 2) stimulant drug-naïve healthy control subjects with no known risk factors for addiction (n = 17); and 3) subjects matched to the high-risk group on personal drug use but without a FH of substance use problems (n = 15). Compared with either control group, the high-risk young adults with a multigenerational FH of substance use disorders exhibited smaller [(11)C]raclopride responses, particularly within the right ventral striatum. Past drug use predicted the dopamine response also, but including it as a covariate increased the group differences. Together, the results suggest that young people at familial high risk for substance use disorders have decreased dopamine responses to an amphetamine challenge, an effect that predates the onset of addiction.
    Biological psychiatry 10/2013; · 8.93 Impact Factor
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    ABSTRACT: Spinal cord transection leads to the elimination of the brainstem-derived monoamine fibres that normally synthesize most of the monoamines in the spinal cord, including serotonin (5-HT) that is synthesized from tryptophan by the enzymes tryptophan hydroxylase (TPH, synthesizing 5-hydroxytryptophan, 5-HTP) and aromatic L-amino acid decarboxylase (AADC, synthesizing 5-HT from 5-HTP). Here we examine whether the spinal cord of transected rats remains able to manufacture and metabolize 5-HT. Immunolabelling for AADC reveals that, while most AADC is confined to brainstem-derived monoamine fibres in spinal cords from normal rats, caudal to a transection AADC is primarily in blood vessel endothelial cells and pericytes, as well as in a novel group of neurons (NeuN positive and GFAP negative), all of which strongly upregulate AADC with injury. However, immunolabelling for 5-HT reveals that there is no detectable endogenous 5-HT synthesis in any structure in the spinal cord caudal to a chronic transection, including in AADC containing vessels and neurons, consistent with a lack of TPH. In contrast, when we applied exogenous 5-HTP (in vitro or in vivo), AADC-containing vessels and neurons synthesized 5-HT, which contributed to increased motoneuron activity and muscle spasms (long-lasting reflexes, LLRs), by acting on 5-HT2 receptors (SB206553-sensitive) located on motoneurons (TTX-resistant). Blocking monoamine oxidase (MAO) markedly increased the sensitivity of the motoneurons (LLR) to 5-HTP. In summary, after spinal cord injury AADC is upregulated in vessels, pericytes and neurons, but does not produce 5-HT that affects motoneurons unless exogenous 5-HTP is administered.
    Journal of Neurophysiology 09/2013; · 3.04 Impact Factor
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    ABSTRACT: The meso-striatal dopamine system influences responses to rewards and the motivation to seek them out. Marked individual differences in these responses are seen in laboratory animals, related in part to input from the prefrontal cortex. Here we measured the relation between cortical morphology and drug-induced striatal dopamine release in healthy young people. Participants were 24 (17 male, 7 female; age 23.0 ± 6.2 years) stimulant drug-naive subjects who underwent PET [(11)C]raclopride scans with 0.3 mg/kg d-amphetamine orally and placebo, and an anatomical MRI scan for measuring cortical thickness. As expected, d-amphetamine produced significant reductions in [(11)C]raclopride binding potential in the striatum as a percentage of the value in the placebo condition. There was substantial individual variability in this response, which was correlated with cortical thickness in the frontal lobe as a whole. The association was strongest in the anterior part of the right lateral prefrontal cortex and bilateral supplementary motor area. A thicker cortex was correlated with a smaller dopamine response. Together, this work demonstrates in humans an association between cortical thickness and the striatal dopamine response to drugs of abuse. Although prefrontal regulation of striatal function has been well studied, it was unclear whether the thickness of the prefrontal cortex was an acceptable proxy to the function of that region. These results suggest it is.
    Journal of Neuroscience 09/2013; 33(38):15285-94. · 6.75 Impact Factor
  • Pierre S Chue, Glen B Baker
    Future medicinal chemistry 09/2013; 5(13):1475-7. · 4.00 Impact Factor
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    ABSTRACT: Depression is one of the most common disorders appearing following a stroke, and is also a major factor limiting recovery and rehabilitation in stroke patients. Antidepressants are the most common prescribed treatment for depression and have shown to have anti-inflammatory properties within the central nervous system (CNS). The major source of pro-inflammatory factors within the CNS are from activated microglia, the innate immune cells of the CNS. Antidepressants have been shown to promote midbrain and hippocampal neuronal survival following an ischemic insult and are mediated through the anti-inflammatory effects on microglia, but the effects on cortical neuronal survival after this insult has yet to be investigated. The present study aimed to test and compare antidepressants from three distinct classes (tricylics, monoamine oxidase inhibitors, and selective serotonin-reuptake inhibitors [SSRIs]) on the release of inflammatory factors and amino acids from activated microglia and whether altering this release could affect cortical neuronal viability after an ischemic insult. Primary microglia were treated with 1 μg/ml LPS and/or 10 μM antidepressants, and the various factors released into medium were assayed. Co-cultures consisting of microglia and primary cortical neurons were used to assess the effects of antidepressant-treated activated microglia on the viability of ischemic injured neurons. Of the antidepressants tested, most decreased the release of the proinflammatory factors nitric oxide, tumor necrosis factor-alpha, and interleukin 1-beta from activated microglia. Fluoxetine and citalopram, the SSRIs, decreased the release of the amino acids glutamate and D-serine from LPS-activated microglia. Oxygen-glucose deprived (OGD) cortical neurons cocultured with LPS- activated microglia pre-treated with fluoxetine and citalopram showed greater survival compared to injured neurons co-cultured with untreated activated microglia. Microglial release of glutamate and D- serine were shown to be the most important factors mediating neuronal survival following antagonism studies. To our knowledge, our results demonstrate for the first time that fluoxetine and citalopram decrease the release of glutamate and D-serine from LPS-activated microglia and this causes an increase in the survival of OGD-injured cortical neurons after co-culture.
    Molecular and Cellular Neuroscience 07/2013; · 3.73 Impact Factor
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    ABSTRACT: Neurons and neighboring astrocytic glia are mostly studied in nervous tissues from rodents whereas less is known on their properties and interactions in human brain. Here, confocal/multiphoton fluorescence imaging for several hours revealed that co-cultured fetal human cortical neurons and astrocytes show pronounced spontaneous rises of cytosolic Ca(2+) which last for up to several minutes without concomitant changes in either movements or membrane potential of mitochondria. Similar Ca(2+) rises were evoked mainly in neurons by bath-applied glutamate or γ-aminobutyric acid (GABA) acting via NMDA+AMPA/Kainate and GABAA receptors, respectively. Predominantly in astrocytes, Ca(2+) baseline was elevated by adenosine-diphosphate (ADP) and adenosine triphosphate (ATP) acting via P2Y1 and P2X7 receptors likely causing release of glutamate and glutamine. Mainly astrocytes responded to histamine, whereas activation of muscarinic acetylcholine (ACh) receptors raised Ca(2+) in both cell types. Evoked neuronal and astrocytic Ca(2+) rises could last for several minutes without affecting mitochondrial movements or membrane potential. In contrast, reversible depolarization of mitochondrial membrane potential accompanied neuronal Ca(2+) rises induced by cyanide-evoked chemical anoxia or uncoupling of mitochondrial respiration with carbonyl-cyanide-4-(trifluoromethoxy)-phenylhydrazone (FCCP). During such metabolic perturbation, mitochondrial depolarization also occurred in astrocytes, whereas Ca(2+) was largely unaffected. In summary, fetal human cortical neurons and astrocytes show distinct patterns of neuro/glio-transmitter- and metabolically-evoked Ca(2+) rises and possess active mitochondria. One aspect of our discussion deals with the question of whether the functional mitochondria contribute to cellular Ca(2+) homeostasis that seems to be already well developed in fetal human cortical brain cells.
    Neuroscience 07/2013; · 3.33 Impact Factor
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    ABSTRACT: IMPORTANCE The treatment of schizophrenia remains a challenge, and the currently available antipsychotic drugs are slow acting and produce a number of adverse effects. OBJECTIVE To examine the effectiveness and safety of a single intravenous administration of sodium nitroprusside (0.5 μg/kg/min for 4 hours) on the positive, negative, anxiety, and depressive symptoms in patients with schizophrenia. DESIGN Single-center, randomized, double-blind, placebo-controlled trial performed from March 9, 2007, to March 12, 2009. SETTING University teaching hospital in São Paulo, Brazil. PARTICIPANTS Twenty inpatients aged 19 to 40 years with a diagnosis of schizophrenia who were in the first 5 years of the disease who are taking antipsychotics. INTERVENTION Sodium nitroprusside administration. MAIN OUTCOME MEASURES The 18-item Brief Psychiatric Rating Scale and the negative subscale of the Positive and Negative Syndrome Scale. RESULTS After the infusion of sodium nitroprusside, a rapid (within 4 hours) improvement of symptoms was observed. The placebo and experimental groups had significant differences in the 18-item Brief Psychiatric Rating Scale total score and subscale scores, which persisted for 4 weeks after infusion. CONCLUSIONS The results clearly show a therapeutic effect of sodium nitroprusside. If this drug is approved for routine clinical use in patients with schizophrenia, this discovery will be an important advance in the pharmacologic treatment of this devastating disorder. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01548612.
    JAMA Psychiatry 05/2013; · 12.01 Impact Factor

Publication Stats

6k Citations
1,397.59 Total Impact Points

Institutions

  • 1980–2014
    • University of Alberta
      • • Department of Psychiatry
      • • Faculty of Pharmacy and Pharmaceutical Sciences
      Edmonton, Alberta, Canada
  • 2013
    • University of São Paulo
      • Ribeirão Preto School of Medicine (FMRP)
      San Paulo, São Paulo, Brazil
  • 2012
    • National Council for Scientific and Technological Development, Brazil
      Palmyra, Minas Gerais, Brazil
  • 2008–2012
    • University of Saskatchewan
      • • Department of Psychiatry
      • • Department of Physiology
      Saskatoon, Saskatchewan, Canada
    • Université de Montréal
      Montréal, Quebec, Canada
  • 2011
    • Cadi Ayyad University
      • Faculty of Sciences Semlalia
      Maraksh, Marrakech-Tensift-Al Haouz, Morocco
  • 2009
    • University of Arkansas for Medical Sciences
      • Department of Psychiatry
      Little Rock, Arkansas, United States
  • 2007
    • Montreal Heart Institute
      Montréal, Quebec, Canada
  • 1999–2007
    • McGill University
      • Department of Psychiatry
      Montréal, Quebec, Canada
  • 2006
    • Northwestern University
      • Department of Biomedical Engineering
      Evanston, IL, United States
  • 2003
    • Gracie Square Hospital, New York, NY
      New York City, New York, United States
  • 1999–2000
    • Centre for Addiction and Mental Health
      • Schizophrenia Program
      Toronto, Ontario, Canada
  • 1986–1996
    • The University of Western Ontario
      • Department of Psychology
      London, Ontario, Canada
  • 1988–1995
    • The Ohio State University
      • Department of Psychiatry
      Columbus, OH, United States
  • 1990
    • University of Michigan
      • Department of Psychiatry
      Ann Arbor, MI, United States
  • 1989
    • TEC Edmonton
      Edmonton, Alberta, Canada