PM484. BQCA Allosteric Modulation of [3H]NMS Binding to Human Cortex is Reduced in a Subgroup of Schizophrenia and Modulation by Divalent Cations

Muscarinic M1 receptor (CHRM1) positive allosteric modulators represent a promising approach to treating the cognitive deficits of schizophrenia. Hence, we decided to extend studies using cloned receptors and animal models to study CHRM1 orthoand allosteric binding in human cortex. Therefore, we measured the displacement of [3H]NMS(0.13nM) with acetylcholine(0—1mM) in the presence of BQCA (positive allosteric modulator: 0—3μM) using tissue from muscarinic receptor deficit schizophrenia (MRDS) subjects (defined by a marked loss in [3H]pirenzepine binding to cortical CHRM1 (~75)), other schizophrenia subjects, and non-psychiatric control subjects. This is a measure of the response of CHRM1 to positive allosteric modulation. CHRM binding sites have been shown to be ion dependent and hence we repeated our experiments using cortex from subjects without a psychiatric illness and [3H]NMS (0.13nM) or [3H]pirenzepine (7nM) in the presence or absence of Zn2+ (10mg/ml) and Mg2+ (10mg/ml). As with cloned CHRM1, BQCA increases the affinity of the CHRM1 orthosteric site for acetylcholine in human cortex (logIC50: 0μM BQCA=−4.95, 0.3μM BQCA=−5.50, and 3.0μM BQCA=−6.21). The effect of BQCA was reduced in MRDS subjects (p<0.01; Cohen’s d=−0.948), but not of sufficient magnitude to suggest allosteric modulators will not elicit a response in MRDS subjects. Zn2+ reduced specific [3H]pirenzepine (p=0.025 cohen’s d=−1.625) and [3H]NMS (p=0.0003 cohen’s d=−5.54) binding; Mg2+ and Zn2+ enhanced acetylcholine displacement of [3H]NMS binding (logIC50: 0mg/ml Mg 2+ or Zn2+=−4.091; 10mg/ml Mg2+=−4.436; 10mg/ml Zn2+=−7.294), but Mg2+ reduced and Zn2+ enhanced displacement of [3H]pirenzepine binding (logIC50: 0mg/ml Mg 2+ or Zn2+=−4.656; 10mg/ml Mg2+=−4.380; 10mg/ml Zn2+=−5.029). Additionally, both Mg2+ and Zn2+ enhanced the effect of BQCA on [3H]NMS (∆logIC50: 0mg/ml Mg2+ or Zn2+=−0.193; 10mg/ml Mg2+=−1.082; 10mg/ml Zn2+=−1.694), but not [3H]pirenzepine (∆logIC50: 0mg/ml Mg2+ or Zn2+=−0.227; 10mg/ml Mg2+=−0.256; 10mg/ml Zn2+=−0.229), binding. Our data suggests that both orthosteric and allosteric sites of CHRMs have complex and differing responses to divalent cations. PM485 Association between erythrocyte membrane fatty acids and psychopathology in individuals at ultrahigh risk for psychosis Min Jhon1, Paul Amminger2, Michael Berk3, Jae-Min Kim1, Sung-Wan Kim1, Claudia M. Klier4, Simon Rice2, Miriam R. Schäfer2, Stefan Smesny5 1Chonnam National University, Republic of Korea, 2Orygen Youth Health, Australia, 3Deakin University, Australia, 4Medical University of Vienna, Austria, 5University Hospital Jena, Germany Abstract Object: This study investigated the relationship between erythrocyte membrane fatty acid (FA) levels and the severity of symptoms of individuals at ultra-high risk(UHR) for psychosis. Methods: The study sample consisted of 80 neuroleptic-naïve UHR patients. Associations between baseline erythrocyte membrane FA levels, measured by gas chromatography, and scores on the Positive and Negative Syndrome Scale (PANSS), the Global Assessment of Functioning Scale, and the Montgomery–Asberg Depression Rating Scale (MADRS) were investigated. After correlation analysis in all participants, subjects were divided into three groups according to the predominance of positive or negative symptoms based on PANSS subscale scores; membrane FA levels in the three groups were then compared. Results: PANSS negative symptom scores were negatively correlated with two saturated FAs (myristic and margaric acids), one ω-9 monounsaturated FA (MUFA;nervonic acid), and oneω-3 polyunsaturated FA(PUFA; docosapentaenoic acid). Negative symptom scores were positively correlated with twoω-9 MUFAs(eicosenoic and erucic acids) and two ω-6 PUFAsObject: This study investigated the relationship between erythrocyte membrane fatty acid (FA) levels and the severity of symptoms of individuals at ultra-high risk(UHR) for psychosis. Methods: The study sample consisted of 80 neuroleptic-naïve UHR patients. Associations between baseline erythrocyte membrane FA levels, measured by gas chromatography, and scores on the Positive and Negative Syndrome Scale (PANSS), the Global Assessment of Functioning Scale, and the Montgomery–Asberg Depression Rating Scale (MADRS) were investigated. After correlation analysis in all participants, subjects were divided into three groups according to the predominance of positive or negative symptoms based on PANSS subscale scores; membrane FA levels in the three groups were then compared. Results: PANSS negative symptom scores were negatively correlated with two saturated FAs (myristic and margaric acids), one ω-9 monounsaturated FA (MUFA;nervonic acid), and oneω-3 polyunsaturated FA(PUFA; docosapentaenoic acid). Negative symptom scores were positively correlated with twoω-9 MUFAs(eicosenoic and erucic acids) and two ω-6 PUFAs (γ-linoleic and docosadienoic acids). PANSS positive symptom scores were correlated only with nervonic acid. No associations were observed between FAs and MADRS scores. In subjects with dominant negative symptoms, the sum of the ω-9 MUFAs and the ω-6:ω-3 FA ratio were both significantly higher than in those with dominant positive symptoms, whereas the sum of ω-3 PUFAs was significantly lower. Conclusions: Abnormalities in FA metabolism may contribute to the neurobiology of psychopathology in UHR individuals. In particular, membrane FA alterations may play a role in negative symptoms, which are primary psychopathological manifestations of schizophrenia-related disability. PM486 Disrupting GluR2-GAPDH Interaction Affects Axon and Dendrite Development Min Jhon1, Paul Amminger2, Michael Berk3, Jae-Min Kim1, Sung-Wan Kim1, Claudia M. Klier4, Simon Rice2, Miriam R. Schäfer2, Stefan Smesny5