IS THERE A RELATIONSHIP BETWEEN TOXOPLASMA GONDII AND PSYCHIATRIC DISORDERS?

Abstracts

Poster 206 ADULT-ONSET GLUTAMATE RECEPTOR EXPRESSION DEFICITS IN THE HIPPOCAMPUS OF GLUTAMINASE-DEFICIENT MICE Inna Gaisler-Salomon1,2, Yvonne Wang2, Scott M. McKinney2, Amy J. Ramsey3,4, Etienne Sibille5, Stephen Rayport2,6 1 Psychology, University of Haifa, Haifa, Israel; 2Psychiatry, Columbia University, New York City, NY, USA; 3Pharmacology and Toxicology, University of Toronoto, Toronto, Canada; 4Cell Biology, Duke University Durham, NC, USA; 5Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA; 6Molecular Therapeutics, New York State Psychiatric Institute, New York City, NY, USA Background: Glutamate signaling in the hippocampus is fundamental to learning and memory; its disruption has been linked to schizophrenia and other disorders. Glutaminase-deficient mice (GLS1 hets), with reduced glutamate recycling, have a focal reduction in hippocampal activity and a selective deficit in hippocampal-dependent contextual learning. We asked whether expression of other enzymes in the glutamate-glutamine recycling pathway or glutamate receptors was affected in the hippocampus of GLS1 hets, and whether expression patterns change during development. Methods: We collected hippocampal and cortical samples from GLS1 het and littermate controls at 3 ages and assessed gene expression using Affymetrix gene chips and rtPCR. We compared GLS1 hets to NR1 hypomorphs, which have reduced expression of the NMDA receptor subunit NR1 and model aspects of schizophrenia. Additionally, we examined context-dependent fear conditioning. Results: In adult mice, GLS1 was downregulated, as expected, by ∼50%, while enzymes in related metabolic pathways were unaffected. Gene expression was altered in long-term plasticity pathway genes. GluR2 was downregulated by ∼40%. rtPCR confirmed the latter finding and further revealed an increase in GluR2 in cortex. In adolescent mice, GluR2 and NR1 expression were unaffected. Gene expression in GLS1 hets differed significantly from NR1 hypomorphs. In parallel to the genetid findings, contextual fear conditioning was unaffected in adolescence, but disrupted in adulthood, as we had shown previously. Discussion: GLS1 deficiency does not affect other metabolic pathways, but does lead to adult-onset alterations in glutamate receptor expression, possibly accounting for adult-onset alterations in context-dependent learning. In the context of current knowledge of glutamate abnormalities in schizophrenia, and since GLS1 het gene expression patterns differ striking from NR1 hypomorphs, these findings support the idea that GLS1 hets do not model schizophrenia, but rather resilience to proschizophrenic challenges, and that inhibition of glutaminase may prove therapeutic in this disorder. doi:10.1016/j.schres.2010.02.701

Poster 207 THE PUZZLE BOX AS SIMPLE AND EFFICIENT BEHAVIORAL TEST FOR IMPAIRMENTS OF GENERAL COGNITION AND EXECUTIVE FUNCTIONS IN MOUSE MODELS OF SCHIZOPHRENIA

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it becomes indispensable to establish and/or refine new or currently available analytical tools in animal models. Cognitive symptoms of schizophrenia that primarily depend on the prefrontal cortex, and to some extent also on the hippocampus, i.e. attention deficits, working memory and executive function impairments, are important features of chronic manifestation of schizophrenia. Various behavioral rodent models have therefore been used when attempting to find animal correlates of cognitive symptoms, most of which require extensive labor and time, to name only few of their limitations. We tried here to establish a simple but informative test on executive functions in mice in different schizophrenia models. Methods: The puzzle box is a behavioral test developed in rodents, in which subjects are presented with different problems of increasing difficulties, and are expected to solve the problems during a limited lapse of time. The arena consists of a white Plexiglas box divided by a removable barrier into two separate compartments: a big and brightly-lit start zone (58 cm long, 28 cm wide), and a smaller protected goal zone (15 cm long, 28 cm wide) containing sawdust and cardboards. Mice are trained to escape the start zone through an underpass (∼ 4 cm wide) located under a wall separating both zones. They have to undergo a total of nine trials (T1-T9) over 3 consecutive days (3 trials per day) with increasing difficulty of passing the underpass. The underpass is first marked and open (T1), then only open (T2-T4), then filled with sawdust (T5-T7), then closed by a plug (T8-T9). Thus, at days 2 and 3, the difficulty of the task corresponds to that of the last trial of the day before. Results: We used five different mouse models of schizophrenia, namely mice with prefrontal cortex and hippocampus lesions, respectively, mice treated sub-chronically with the NMDA-antagonist MK-801, mice constitutively lacking the GluR-1 subunit of AMPA-receptors (GluR-1 knockout mice), and mice over-expressing the D2 dopamine receptor in the striatum. Compared to their corresponding experimental controls, all mice models used here demonstrated altered executive functions though to an extent that (not surprisingly) varied between the different models. Strongest deficits where observed in hippocampal lesioned mice and GluR-1 knockout mice, while subtle but specific deficits (particularly in advanced trial 8) were found in prefrontally lesioned mice and in animals over-expressing D2 receptors. Discussion: With this report we demonstrate face validity of the puzzle box as a behavioral screening tool for executive functions in general and for schizophrenia mouse models in particular. Interestingly, among the various models studied here, specific behavioral deficits were also found in two models with previously demonstrated deficits of prefrontal cortical functions, i.e. one lesion models and one transgenic model (D2 receptor overexpressing mice). Additional experiments will be performed in an effort to rescue the observed deficiencies in different models by classical and atypical antipsychotic drugs. doi:10.1016/j.schres.2010.02.702

Poster 208 Peter Gass1, Nada BenAbdallah1, Johannes Fuss1, Massimo Trusel1, Mike Galsworthy2, Robert Deacon3, Marco Riva4, Christoph Kellendonk5, Rolf Sprengel6, Hans-Peter Lipp2 1 Central Institute of Mental Health Mannheim, Germany; 2Anatomy Institute University of Zürich, Switzerland; 3Dep. Experimental Psychology University of Oxford, United Kingdom; 4Dep. Pharmacology University of Milano, Italy; 5The Lieber Center for Schizophrenia Research Columbia University, New York, USA; 6Max-Planck-Institute for Medical Research, Heidelberg, Germany

IS THERE A RELATIONSHIP BETWEEN TOXOPLASMA GONDII AND PSYCHIATRIC DISORDERS?

Background: In light of the current breakthroughs that are unraveling molecular and genetic underpinnings of schizophrenia,

Background: Toxoplasma gondii is implicated as a risk factor for the development of schizophrenia and depression, and is associated

Selina A. Henriquez1, David M. Thompson2, Fiona L. Henriquez3, James Alexander1, Judith Pratt1, Ros Brett1, Craig W. Roberts1 1 University of Strathclyde, Glasgow, Lanarkshire, Scotland; 2University of Glasgow, Glasgow, Lanarkshire, Scotland; 3University of the West of Scotland, Paisley, Renfrewshire, Scotland

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Abstracts

with behavioural changes in humans and rodents. Infected rodents are shown to be more prone to be attacked by cats, in which the sexual life cycle is completed, through reduced levels of anxiety and the attraction to the odour of the cat's urine. As T. gondii forms cysts that are located mainly in the brain during a chronic infection, it is well placed anatomically to mediate these effects. Recently, changes in the immune response have also been associated with mood and behavioural alterations and compounds designed to alter mood, such as fluoxetine, have been demonstrated to alter aspects of immune function. Methods: The ability of T. gondii to alter murine behaviour was assessed through a series of behavioural tests (open field task and PPI). Possible molecular mechanisms for T. gondii to alter behaviour through the action of the immune response were investigated. In particular the ability of T. gondii to alter levels of tryptophan metabolising enzymes including indolamine 2,3, dioxygenase (IDO), tryptophan hydroxylase (TPH2) and tryptophan oxygenase (TDO) which could in turn affect levels of serotonin. Results: Infected mice spent more time in the centre of the open field in comparison to uninfected controls significantly at one and two months after infection. PPI levels in infected mice were reduced significantly at one month after infection. Transcripts for IFN- γ were increased in the brains of T. gondii infected mice. However, no differences were found in the transcript levels of TPH2, IDO, TDO between infected and non-infected mice. Discussion: Lower anxiety levels were measured in T. gondii-infected mice in the open field task. This may lead to a reduced chance of survival in the wild and an increased likelihood of attack by felines, thus increasing the perpetuation of the parasite's life-cycle. The reduction of PPI in infected mice demonstrates a novel affect of T. gondii on the sensorimotor gating circuit, which is also deficit in schizophrenic patients. Although no significant differences were detected in transcript levels of TPH2, IDO and TDO potential differences in protein levels of these enzymes need to be assessed by Western blotting.

doi:10.1016/j.schres.2010.02.703

Poster 209 THE MGLUR2/3 AGONIST LY379268 REVERSES POST-WEANING SOCIAL ISOLATION-INDUCED RECOGNITION MEMORY DEFICITS IN THE RAT Caitlin A. Jones1, Janice W. Smith2, Angus M. Brown1, Dorothee P. Auer3, Kevin C.F. Fone1 1 School of Biomedical Sciences, University of Nottingham Queen's Medical Centre, Nottinghamshire, United Kingdom; 2Lilly UK, Erl Wood Manor Windlesham, Surrey, United Kingdom; 3Academic Radiology, University of Nottingham Queen's Medical Centre, Nottinghamshire, United Kingdom Background: An mGluR2/3 receptor agonist, LY404039 has previously shown clinical efficacy against some positive and negative symptoms of schizophrenia. However, the preclinical understanding of how mGluR2/3 agonists modulate schizophrenia-like symptoms is limited. Given both the lack of studies of the potent, selective, mGluR2/3 agonist, LY379268, in neurodevelopmental models of psychosis and the unknown contribution that changes in glutamatergic neuronal function make to the isolation rearing syndrome, this study explored the ability of acute, systemic administration of a single dose of LY379268 (1 mg/kg) to reverse isolation rearinginduced behavioural changes. Methods: Male Lister Hooded rats obtained immediately after weaning on post-natal day (PND) 23-25 were either group-housed

(GH; 4 per cage) or isolation-reared (IR) for 6 weeks. At subsequent weekly intervals, animals received either saline (1 ml/kg; i.p) or LY379268 (1 mg/kg; i.p. n = 9-12 per group) 30 min prior to recording, locomotor activity in a novel arena, novel object discrimination (NOD), pre-pulse inhibition (PPI) of the acoustic startle response and contextual fear conditioning. Statistical analyses were all carried out using either a one-way or two-way RM ANOVA with post-hoc Bonferroni tests. Results: Isolation rearing induced locomotor hyperactivity that was significantly reversed by LY379268 (mean total activity counts/ 60 min ± SEM; GH vehicle: 1201 ± 92; IR vehicle: 1635 ± 95; IR LY379268: 1183 ± 91, GH LY379268: 920 ± 75; p ≤ 0.0001). GH vehicle-treated rats successfully discriminated the novel from the familiar object in a two-trial object discrimination task (inter-trial interval 2 h), whilst no significant object discrimination was seen in vehicle-treated IR rats (Object p ≤ 0.0001; Treatment p = 0.62; Object x Treatment p = 0.16). This NOD deficit was fully reversed in LY379268-treated isolates such that they spent a greater amount of time on the novel object (mean exploratory activity sec ± SEM; GH vehicle 16 ± 2 and 7 ± 1 sec; IR vehicle 14 ± 2 and 12 ± 2; IR LY379268 16 ± 2 and 9 ± 2; GH LY379268 13 ± 2 and 8 ± 1 sec at novel and familiar object respectively). % PPI increased with increasing pre-pulse intensity in all treatment groups (Pre-pulse intensity p ≤ 0.0001; Treatment p ≤ 0.01; Interaction p = 0.50). There was no effect of IR alone on % PPI, but post-hoc analysis showed that LY379268 significantly impaired % PPI in IR and not GH rats. The initial startle response of vehicle-treated IR rats was significantly lower than all other treatment groups, however this was reversed by LY379268 (p ≤ 0.0001). Isolation-rearing induced a significant contextual fear conditioning deficit that was unaltered by LY379268. 24 h and 48 h post-training, freezing behaviour was significantly reduced in IR-vehicle and IR-LY379268 compared to both vehicle- and LY379268-treated GH rats (mean freezing sec ± SEM 24 h and 48 h post-training; GH vehicle 205 ± 19 and 149 ± 27 sec; IR vehicle 146 ± 27 and 71 ± 17; IR LY379268 113 ± 17 and 72 ± 18; GH LY379268 216 ± 16 and 148 ± 32 sec). In all groups a significant attenuation in freezing behaviour was seen between 24 h and 48 h post-training (Trial p ≤ 0.001; Treatment p ≤ 0.01; Trial x Treatment p = 0.62). Discussion: These data show that modulation of glutamatergic receptor function by LY379268 can reverse some post-weaning, social isolation-induced changes which have translational relevance to core symptom deficits in schizophrenia and support a potential therapeutic role of mGluR2/3 agonists in its treatment of positive and some cognitive symptoms. doi:10.1016/j.schres.2010.02.704

Poster 210 CANNABINOIDS: ENVIRONMENTAL RISK FACTORS FOR A NEUREGULIN 1 MOUSE MODEL FOR SCHIZOPHRENIA? Tim Karl1,2,3, Rose Chesworth1,2, Jonathon Arnold2,4, Leonora Long1,2,3 1 Prince of Wales Medical Research Inst. Sydney, NSW, Australia; 2 Schizophrenia Research Institute, Sydney, NSW, Australia; 3University of New South Wales, Sydney, NSW, Australia; 4University of Sydney, Sydney, NSW, Australia Background: Heavy cannabis consumption is associated with increased risk of developing schizophrenia in susceptible individuals. Adolescence appears to be a particular time of vulnerability to the detrimental effects of cannabis. Importantly, cannabis is a mixture of cannabinoids, including the psychotomimetic Δ9-tetra-