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P.1.05 Chronic stress alters cocaine-induced modulation of BDNF expression and signaling in rat brain
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Molecular neuropsychopharmacology
with cytogenetic abnormalities to the schizophrenia phenotype. In this review, recent CNV studies are also included. A literature survey of the Medline and Pubmed databases was performed, using keyword searches with the terms: ‘schizophren*’, ‘chromosom*’, ‘genet*’, and ’cytogenet*’ in several combinations. The quality of the phenotype was rated for each included case. Ratings were based on the clinical description, the presence of psychiatric diagnosis or a classification system. This permits a ranking of regions containing candidate genes based on the most valid clinical diagnosis of schizophrenia. Available probe and marker information was used to define the boundaries of the ‘Cytogenetic Regions Of Interest’ (CROIs). The CROIs found were compared with loci reported in CNV studies and with the regions reported in association studies and two large meta-analyses of linkage studies. The findings of the current review indicate: (1) several regions of overlap between CROIs and known loci from linkage and/or association findings, (2) additional regions of overlap among multiple CROIs at the same locus. Overlap of several CROIs coincides with linkage and association findings at the same locus on 1q21, 5q34, 14q13, and 22q11.2. These regions were most of the time supported by recent CNV findings. Possible novel regions, indicated by clustering of multiple CROIs, include: 9p11, 9q13, and Xp22. In order to aid in the identification of susceptibility genes and to connect functionally related genes within these CROIs, positional candidate gene prioritization methods were performed. The basepair boundaries of the identified CROIs were analyzed with, among others, the Prioritizer gene network [2]. This network integrates information on genes and the functional relationships between genes, based on data from different databases. Thereby it prioritizes positional candidate genes, by assuming that the majority of causative genes are functionally closely related. The analysis of the seven CROIs resulted in a top list of genes for each of the regions. At the same time, current literature was investigated on (implicated) biological pathways in schizophrenia, to identify genes involved in these pathways and residing in these loci, which could suggest a mutation and/or gene expression variation. Preliminary results point out to cytokine-related genes, including CSF2RA and IL3RA, recently indicated as candidate genes for schizophrenia susceptibility (3). Reference(s) [1] MacIntyre, D.J., Blackwood, D.H.R., Porteous, D.J., Pickard, B.S., Muir, W.J., 2003, Chromosomal abnormalities and mental illness. Mol Psychiatry 8: 275–287.
[2] Franke, L., van Bakel, H., Fokkens, L., et al., 2006, Reconstruction of a functional human gene network, with an application for prioritizing positional candidate genes. Am J Hum Genet 78: 1011–1025. [3] Lencz, T., Morgan, T.V., Athanasiou, M., et al., 2007, Converging evidence for a pseudoautosomal cytokine receptor gene locus in schizophrenia. Mol Psychiatry 12: 572–580.
P.1.05 Chronic stress alters cocaine-induced modulation of BDNF expression and signaling in rat brain L. Caffino1 ° , G. Racagni1 , M.A. Riva1 , F. Fumagalli1 . 1 University of Milan, Pharmacological Sciences, Milan, Italy Exposure to drugs of abuse such as cocaine is known to alter the expression of genes and proteins that mediate the acute as well as chronic effects of such drugs. In addition, it has been demonstrated that stress is able to modulate behavioral and neurochemical responses to drugs of abuse [1]. It is conceivable to hypothesize that a commonality exists in the mechanisms mediating the interaction between stress and cocaine which may mutually influence each other and promote cross-sensitization. Among the different factors that could be altered by the combined action of stress and cocaine, a plausible candidate may be represented by the neurotrophin brain-derived neurotrophic factor (BDNF), since our previous work showed that chronic stress alters BDNF expression [2] and cocaine administration evokes regionaland temporal-specific changes in the expression of BDNF [3]. On this basis, we decided to investigate whether a chronic unpredictable stress could alter the short-term modulation of BDNF expression and BDNF-dependent intracellular pathways in rat prefrontal cortex. We thus exposed male rats to a chronic stress consisting mainly of immobilization and swim in cold water. At the end of the last stress session animals were injected with cocaine (10 mg/kg, intraperitoneal) and sacrificed 2 hours later. Total RNA and proteins were extracted from prefrontal cortex and evaluated with RNase Protection Assay and Western Blotting, respectively. Data were analyzed using two way analysis of variance (ANOVA) followed by Single Contrast Post-Hoc Test (SCPHT). Significance for all tests was assumed at p < 0.05. We found that exposure to chronic stress abolished the increase of BDNF expression and its high affinity receptor TrkB observed after cocaine injection, which was instead evident in unstressed animals. In addition to TrkB expression, its trafficking toward the membrane
Molecular neuropsychopharmacology observed in unstressed animals was abolished in repeatedly stressed rats. We next analyzed the different intracellular signaling pathways that can be activated by the neurotrophin, i.e. ERK1/2, GSK3b/Akt and PLCg pathways. To this end, we found that, in the crude synaptosomal fraction of unstressed animals, cocaine is able to selectively activate ERK1/2 pathway, an effect which is abolished in rats exposed to repeated stress. We also measured Arc gene expression, a well known marker of neuronal activity, and found that, in both unstressed and stressed animals, the single injection of cocaine enhanced Arc expression, thus indicating that the lack of effects in stressed rats is not due to impaired responsiveness to external stimuli induced by the stress procedure. Taken together, our data indicate that the neurotrophin BDNF, its high affinity receptor trkB and the MAP kinases ERK1/2 represent specific vulnerable targets of the combination of stress and cocaine in rat prefrontal cortex. These results identify a potential molecular target through which stress alters cellular sensitivity to cocaine, and might also prove useful in understanding the mechanisms underlying brain vulnerability to stress. Reference(s) [1] Piazza, P.V., Le Moal, M., 1998, Trends Pharmacol Sci Feb; 19(2): 67−74. [2] Fumagalli, F., et al., 2003, Mol Psychiatry Nov; 8(11): 898–899. [3] Fumagalli, F., et al., 2007, Eur J Neurosci Nov; 26(10): 2756–2763. P.1.06 Limbic dopamine D2-receptor binding and social desirability S. Cervenka1 ° , C. Halldin1 , L. Farde1 . 1 Karolinska Institutet, Dept of Clinical Neuroscience, Stockholm, Sweden Purpose: Research on the biological underpinnings of personality can provide leads to the pathophysiology of psychiatric disorders, and thus aid the development of novel pharmacological treatment approaches. The dopamine system has a role in social behaviour and personality, as supported by animal research and studies in human subjects. In particular, recent molecular imaging studies have shown a negative correlation between dopamine D2-receptor binding in the striatum and a measure of socially desirable responding [1,2], which can be viewed as a tendency towards social compliance in order to gain approval or acceptance. The emotional and cognitive aspects of this behaviour suggest involvement
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of brain regions outside of the striatum, in particular limbic structures. The aim of the present study was to explore associations between the personality trait social desirability and dopamine D2-receptor binding in both striatal and extrastriatal brain regions. Methods: We examined dopamine D2-receptor availability in 16 healthy control subjects using Positron Emission Tomography and the radioligands [11 C]raclopride and [11 C]FLB 457. Regions of interest were defined for each subject individually on a T1 weighted MRI image, and included striatum for [11 C]raclopride examinations and frontal and limbic cortical brain regions for [11 C]FLB 457 measurements. Regional binding potential (BP) values were calculated using the simplified reference tissue model with cerebellum as reference input. The personality trait social desirability was assessed using the inventory Swedish universities Scales of Personality (SSP). Partial correlations, controlling for potential confounders age and educational level, were calculated between BP values and SSP social desirability scores. Results: Negative correlation coefficients were found between D2-receptor binding and social desirability scores for all brain regions examined. For [11 C]FLB 457 BP values in the hippocampal-amygdala complex, the correlation was statistically significant (p = 0.008, twotailed), while for [11 C]raclopride binding in striatum the relationship showed trend level significance (p = 0.075). Conclusion: The present results add to previous evidence of a role for the striatal dopamine system in socially desirable behaviour, and extend this research into extrastriatal brain regions. Since binding potential is a product of receptor density and apparent affinity, the observed relationships may reflect differences in D2-receptor density, endogenous dopamine levels, or both. Hippocampus and amygdala have in other lines of research shown to be of key importance in memory function and fear processing, respectively. Furthermore, dopaminergic neurotransmission in these regions has been linked to learning and modulation of emotional processes. Consequently, it may be speculated that the present findings reflect an involvement of the mesolimbic dopamine system in socially desirable behaviour by influencing explicit learning or conditioning to social stimuli. The personality trait social desirability is of relevance to several psychiatric disorders, including anxiety syndromes such as social phobia, and the results thus motivate detailed mapping of dopaminergic markers in clinical samples. Reference(s) [1] Huang, C.L., Yang, Y.K., Chu, C.L., Lee, I.H., Yeh, T.L., Chen, P.S., Chiu, N.T., 2006, The association
Molecular neuropsychopharmacology
with cytogenetic abnormalities to the schizophrenia phenotype. In this review, recent CNV studies are also included. A literature survey of the Medline and Pubmed databases was performed, using keyword searches with the terms: ‘schizophren*’, ‘chromosom*’, ‘genet*’, and ’cytogenet*’ in several combinations. The quality of the phenotype was rated for each included case. Ratings were based on the clinical description, the presence of psychiatric diagnosis or a classification system. This permits a ranking of regions containing candidate genes based on the most valid clinical diagnosis of schizophrenia. Available probe and marker information was used to define the boundaries of the ‘Cytogenetic Regions Of Interest’ (CROIs). The CROIs found were compared with loci reported in CNV studies and with the regions reported in association studies and two large meta-analyses of linkage studies. The findings of the current review indicate: (1) several regions of overlap between CROIs and known loci from linkage and/or association findings, (2) additional regions of overlap among multiple CROIs at the same locus. Overlap of several CROIs coincides with linkage and association findings at the same locus on 1q21, 5q34, 14q13, and 22q11.2. These regions were most of the time supported by recent CNV findings. Possible novel regions, indicated by clustering of multiple CROIs, include: 9p11, 9q13, and Xp22. In order to aid in the identification of susceptibility genes and to connect functionally related genes within these CROIs, positional candidate gene prioritization methods were performed. The basepair boundaries of the identified CROIs were analyzed with, among others, the Prioritizer gene network [2]. This network integrates information on genes and the functional relationships between genes, based on data from different databases. Thereby it prioritizes positional candidate genes, by assuming that the majority of causative genes are functionally closely related. The analysis of the seven CROIs resulted in a top list of genes for each of the regions. At the same time, current literature was investigated on (implicated) biological pathways in schizophrenia, to identify genes involved in these pathways and residing in these loci, which could suggest a mutation and/or gene expression variation. Preliminary results point out to cytokine-related genes, including CSF2RA and IL3RA, recently indicated as candidate genes for schizophrenia susceptibility (3). Reference(s) [1] MacIntyre, D.J., Blackwood, D.H.R., Porteous, D.J., Pickard, B.S., Muir, W.J., 2003, Chromosomal abnormalities and mental illness. Mol Psychiatry 8: 275–287.
[2] Franke, L., van Bakel, H., Fokkens, L., et al., 2006, Reconstruction of a functional human gene network, with an application for prioritizing positional candidate genes. Am J Hum Genet 78: 1011–1025. [3] Lencz, T., Morgan, T.V., Athanasiou, M., et al., 2007, Converging evidence for a pseudoautosomal cytokine receptor gene locus in schizophrenia. Mol Psychiatry 12: 572–580.
P.1.05 Chronic stress alters cocaine-induced modulation of BDNF expression and signaling in rat brain L. Caffino1 ° , G. Racagni1 , M.A. Riva1 , F. Fumagalli1 . 1 University of Milan, Pharmacological Sciences, Milan, Italy Exposure to drugs of abuse such as cocaine is known to alter the expression of genes and proteins that mediate the acute as well as chronic effects of such drugs. In addition, it has been demonstrated that stress is able to modulate behavioral and neurochemical responses to drugs of abuse [1]. It is conceivable to hypothesize that a commonality exists in the mechanisms mediating the interaction between stress and cocaine which may mutually influence each other and promote cross-sensitization. Among the different factors that could be altered by the combined action of stress and cocaine, a plausible candidate may be represented by the neurotrophin brain-derived neurotrophic factor (BDNF), since our previous work showed that chronic stress alters BDNF expression [2] and cocaine administration evokes regionaland temporal-specific changes in the expression of BDNF [3]. On this basis, we decided to investigate whether a chronic unpredictable stress could alter the short-term modulation of BDNF expression and BDNF-dependent intracellular pathways in rat prefrontal cortex. We thus exposed male rats to a chronic stress consisting mainly of immobilization and swim in cold water. At the end of the last stress session animals were injected with cocaine (10 mg/kg, intraperitoneal) and sacrificed 2 hours later. Total RNA and proteins were extracted from prefrontal cortex and evaluated with RNase Protection Assay and Western Blotting, respectively. Data were analyzed using two way analysis of variance (ANOVA) followed by Single Contrast Post-Hoc Test (SCPHT). Significance for all tests was assumed at p < 0.05. We found that exposure to chronic stress abolished the increase of BDNF expression and its high affinity receptor TrkB observed after cocaine injection, which was instead evident in unstressed animals. In addition to TrkB expression, its trafficking toward the membrane
Molecular neuropsychopharmacology observed in unstressed animals was abolished in repeatedly stressed rats. We next analyzed the different intracellular signaling pathways that can be activated by the neurotrophin, i.e. ERK1/2, GSK3b/Akt and PLCg pathways. To this end, we found that, in the crude synaptosomal fraction of unstressed animals, cocaine is able to selectively activate ERK1/2 pathway, an effect which is abolished in rats exposed to repeated stress. We also measured Arc gene expression, a well known marker of neuronal activity, and found that, in both unstressed and stressed animals, the single injection of cocaine enhanced Arc expression, thus indicating that the lack of effects in stressed rats is not due to impaired responsiveness to external stimuli induced by the stress procedure. Taken together, our data indicate that the neurotrophin BDNF, its high affinity receptor trkB and the MAP kinases ERK1/2 represent specific vulnerable targets of the combination of stress and cocaine in rat prefrontal cortex. These results identify a potential molecular target through which stress alters cellular sensitivity to cocaine, and might also prove useful in understanding the mechanisms underlying brain vulnerability to stress. Reference(s) [1] Piazza, P.V., Le Moal, M., 1998, Trends Pharmacol Sci Feb; 19(2): 67−74. [2] Fumagalli, F., et al., 2003, Mol Psychiatry Nov; 8(11): 898–899. [3] Fumagalli, F., et al., 2007, Eur J Neurosci Nov; 26(10): 2756–2763. P.1.06 Limbic dopamine D2-receptor binding and social desirability S. Cervenka1 ° , C. Halldin1 , L. Farde1 . 1 Karolinska Institutet, Dept of Clinical Neuroscience, Stockholm, Sweden Purpose: Research on the biological underpinnings of personality can provide leads to the pathophysiology of psychiatric disorders, and thus aid the development of novel pharmacological treatment approaches. The dopamine system has a role in social behaviour and personality, as supported by animal research and studies in human subjects. In particular, recent molecular imaging studies have shown a negative correlation between dopamine D2-receptor binding in the striatum and a measure of socially desirable responding [1,2], which can be viewed as a tendency towards social compliance in order to gain approval or acceptance. The emotional and cognitive aspects of this behaviour suggest involvement
S7
of brain regions outside of the striatum, in particular limbic structures. The aim of the present study was to explore associations between the personality trait social desirability and dopamine D2-receptor binding in both striatal and extrastriatal brain regions. Methods: We examined dopamine D2-receptor availability in 16 healthy control subjects using Positron Emission Tomography and the radioligands [11 C]raclopride and [11 C]FLB 457. Regions of interest were defined for each subject individually on a T1 weighted MRI image, and included striatum for [11 C]raclopride examinations and frontal and limbic cortical brain regions for [11 C]FLB 457 measurements. Regional binding potential (BP) values were calculated using the simplified reference tissue model with cerebellum as reference input. The personality trait social desirability was assessed using the inventory Swedish universities Scales of Personality (SSP). Partial correlations, controlling for potential confounders age and educational level, were calculated between BP values and SSP social desirability scores. Results: Negative correlation coefficients were found between D2-receptor binding and social desirability scores for all brain regions examined. For [11 C]FLB 457 BP values in the hippocampal-amygdala complex, the correlation was statistically significant (p = 0.008, twotailed), while for [11 C]raclopride binding in striatum the relationship showed trend level significance (p = 0.075). Conclusion: The present results add to previous evidence of a role for the striatal dopamine system in socially desirable behaviour, and extend this research into extrastriatal brain regions. Since binding potential is a product of receptor density and apparent affinity, the observed relationships may reflect differences in D2-receptor density, endogenous dopamine levels, or both. Hippocampus and amygdala have in other lines of research shown to be of key importance in memory function and fear processing, respectively. Furthermore, dopaminergic neurotransmission in these regions has been linked to learning and modulation of emotional processes. Consequently, it may be speculated that the present findings reflect an involvement of the mesolimbic dopamine system in socially desirable behaviour by influencing explicit learning or conditioning to social stimuli. The personality trait social desirability is of relevance to several psychiatric disorders, including anxiety syndromes such as social phobia, and the results thus motivate detailed mapping of dopaminergic markers in clinical samples. Reference(s) [1] Huang, C.L., Yang, Y.K., Chu, C.L., Lee, I.H., Yeh, T.L., Chen, P.S., Chiu, N.T., 2006, The association