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Impaired limbic gamma oscillatory synchrony during anxiety-related behavior in a genetic mouse model of bipolar mania.

ABSTRACT: Alterations in anxiety-related processing are observed across many neuropsychiatric disorders, including bipolar disorder. Though polymorphisms in a number of circadian genes confer risk for this disorder, little is known about how changes in circadian gene function disrupt brain circuits critical for anxiety-related processing. Here we characterize neurophysiological activity simultaneously across five limbic brain areas (nucleus accumbens, amygdala, prelimbic cortex, ventral hippocampus, and ventral tegmental area) as wild-type (WT) mice and mice with a mutation in the circadian gene, CLOCK (Clock-?19 mice) perform an elevated zero maze task. In WT mice, basal limbic gamma oscillatory synchrony observed before task performance predicted future anxiety-related behaviors. Additionally, dynamic changes in limbic gamma oscillatory synchrony were observed based on the position of WT mice in the zero maze. Clock-?19 mice, which displayed an increased propensity to enter the open section of the elevated maze, showed profound deficits in these anxiety-related circuit processes. Thus, our findings link the anxiety-related behavioral deficits observed in Clock-?19 mice with dysfunctional gamma oscillatory tuning across limbic circuits and suggest that alterations in limbic oscillatory circuit function induced by circadian gene polymorphisms may contribute to the behavioral manifestations seen in bipolar mania.

SUBMITTER: Dzirasa K

PROVIDER: S-EPMC3112006 | biostudies-other | 2011 Apr

REPOSITORIES: biostudies-other

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Impaired limbic gamma oscillatory synchrony during anxiety-related behavior in a genetic mouse model of bipolar mania.

Dzirasa Kafui K McGarity DeAnna L DL Bhattacharya Anirban A Kumar Sunil S Takahashi Joseph S JS Dunson David D McClung Colleen A CA Nicolelis Miguel A L MA

The Journal of neuroscience : the official journal of the Society for Neuroscience 20110401 17

Alterations in anxiety-related processing are observed across many neuropsychiatric disorders, including bipolar disorder. Though polymorphisms in a number of circadian genes confer risk for this disorder, little is known about how changes in circadian gene function disrupt brain circuits critical for anxiety-related processing. Here we characterize neurophysiological activity simultaneously across five limbic brain areas (nucleus accumbens, amygdala, prelimbic cortex, ventral hippocampus, and v ...[more]

PMID: 21525286

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Project description:Bipolar disorder (BPD) is a debilitating heritable psychiatric disorder. Contemporary models for the manic pole of BPD have primarily utilized either single locus transgenics or treatment with psychostimulants. Our lab recently characterized a mouse strain, termed Madison (MSN), which naturally displays a manic phenotype, exhibiting elevated locomotor activity, increased sexual behavior, and higher forced swimming relative to control strains. Lithium chloride and olanzapine treatments attenuate this phenotype. In this study, we replicated our locomotor activity experiment, showing that MSN mice display generationally-stable mania relative to their outbred ancestral strain, hsd:ICR (ICR). We then performed a gene expression microarray experiment to compare hippocampus of MSN and ICR mice. We found dysregulation of multiple transcripts whose human orthologs are associated with BPD and other psychiatric disorders including schizophrenia and ADHD, including: Epor, Smarca4, Cmklr1, Cat, Tac1, Npsr1, Fhit, and P2rx7. RT-qPCR confirmed dysregulation for all of seven transcripts tested. Using a network analysis, we found dysregulation of a gene system related to chromatin packaging, a result convergent with recent human findings on BPD. Using a novel genomic enrichment algorithm, we found enrichment in genome regions homologous to human loci implicated in BPD in replicated linkage studies including homologs of human cytobands 1p36, 3p14, 3q29, 6p21-22, 12q24, 16q24, and 17q25. Our findings suggest that MSN mice represent a polygenic model for the manic pole of BPD showing much of the genetic systems complexity of the corresponding human disorder. Further, the high degree of convergence between our findings and the human literature on BPD brings up novel questions about evolution by analogy in mammalian genomes. In total, 12 total RNA samples were used for microarray analysis: 6 samples from Madison mice and 6 samples from ICR outbred mice. All samples were biological replicates.

Project description:Recent investigations have used diffusion-weighted imaging to reveal disturbances in the neurocircuitry that underlie cognitive-emotional control in bipolar disorder (BD) and in unaffected siblings or children at high genetic risk (HR). It has been difficult to quantify the mechanism by which structural changes disrupt the superimposed brain dynamics, leading to the emotional lability that is characteristic of BD. Average controllability is a concept from network control theory that extends structural connectivity data to estimate the manner in which local neuronal fluctuations spread from a node or subnetwork to alter the state of the rest of the brain. We used this theory to ask whether structural connectivity deficits previously observed in HR individuals (n?=?84, mean age 22.4), patients with BD (n?=?38, mean age 23.9), and age- and gender-matched controls (n?=?96, mean age 22.6) translate to differences in the ability of brain systems to be manipulated between states. Localized impairments in network controllability were seen in the left parahippocampal, left middle occipital, left superior frontal, right inferior frontal, and right precentral gyri in BD and HR groups. Subjects with BD had distributed deficits in a subnetwork containing the left superior and inferior frontal gyri, postcentral gyrus, and insula (p?=?0.004). HR participants had controllability deficits in a right-lateralized subnetwork involving connections between the dorsomedial and ventrolateral prefrontal cortex, the superior temporal pole, putamen, and caudate nucleus (p?=?0.008). Between-group controllability differences were attenuated after removal of topological factors by network randomization. Some previously reported differences in network connectivity were not associated with controllability-differences, likely reflecting the contribution of more complex brain network properties. These analyses highlight the potential functional consequences of altered brain networks in BD, and may guide future clinical interventions.

Project description:Abnormalities in functional connectivity between brain areas have been postulated as an important pathophysiological mechanism underlying schizophrenia. In particular, macroscopic measurements of brain activity in patients suggest that functional connectivity between the frontal and temporal lobes may be altered. However, it remains unclear whether such dysconnectivity relates to the aetiology of the illness, and how it is manifested in the activity of neural circuits. Because schizophrenia has a strong genetic component, animal models of genetic risk factors are likely to aid our understanding of the pathogenesis and pathophysiology of the disease. Here we study Df(16)A(+/-) mice, which model a microdeletion on human chromosome 22 (22q11.2) that constitutes one of the largest known genetic risk factors for schizophrenia. To examine functional connectivity in these mice, we measured the synchronization of neural activity between the hippocampus and the prefrontal cortex during the performance of a task requiring working memory, which is one of the cognitive functions disrupted in the disease. In wild-type mice, hippocampal-prefrontal synchrony increased during working memory performance, consistent with previous reports in rats. Df(16)A(+/-) mice, which are impaired in the acquisition of the task, showed drastically reduced synchrony, measured both by phase-locking of prefrontal cells to hippocampal theta oscillations and by coherence of prefrontal and hippocampal local field potentials. Furthermore, the magnitude of hippocampal-prefrontal coherence at the onset of training could be used to predict the time it took the Df(16)A(+/-) mice to learn the task and increased more slowly during task acquisition. These data suggest how the deficits in functional connectivity observed in patients with schizophrenia may be realized at the single-neuron level. Our findings further suggest that impaired long-range synchrony of neural activity is one consequence of the 22q11.2 deletion and may be a fundamental component of the pathophysiology underlying schizophrenia.

Project description:BACKGROUND:Symptoms of anxiety, irritability, and agitation (AIA) are prevalent among patients with bipolar I disorder (BD-I) mania with depressive symptoms, and could potentially be used to aid physicians in the identification of this more severe form of BD-I. Using data from two clinical trials, the aims of this post hoc analysis were to describe the phenomenology of bipolar mania in terms of AIA and depressive symptoms, and to evaluate the influence of these symptoms on the likelihood of remission during treatment. METHODS:Patients with a BD-I manic or mixed episode (Diagnostic and Statistical Manual of Mental Disorders IV criteria) were randomised to 3 weeks of double-blind treatment with asenapine, placebo, or olanzapine (active comparator). Anxiety was defined as a score of ?3 on the Positive and Negative Syndrome Scale 'anxiety' item, irritability as a score of ?4 on the Young Mania Rating Scale (YMRS) 'irritability' item, and agitation as a score of ?3 on the YMRS 'increased motor activity-energy' item. Depressive symptoms were defined as a score of ?1 on three or more individual Montgomery-Åsberg Depression Rating Scale (MADRS) items, or a MADRS Total score of ?20. RESULTS:A total of 960 patients with BD-I were analysed, 665 with a manic episode and 295 with a mixed episode. At baseline, 61.4% had anxiety, 62.4% had irritability, 76.4% had agitation, and 34.0% had all three AIA symptoms ('severe AIA'); 47.3% had three or more depressive symptoms, and 13.5% had a MADRS total score of ?20. Anxiety, irritability, and severe AIA (but not agitation) were statistically significantly more common in patients with depressive symptoms. Patients with anxiety or severe AIA at baseline were statistically significantly less likely to achieve remission (YMRS total <12). In general, remission rates were higher with asenapine and olanzapine than with placebo, irrespective of baseline AIA or depressive symptoms. CONCLUSIONS:Assessment of AIA symptoms in bipolar mania could enable physicians to identify patients with more severe depressive symptoms, allowing for appropriate intervention. Assessment and monitoring of AIA may help physicians to predict which patients may be harder to treat and at risk for self-harm. Trial registration ClinicalTrials.gov NCT00159744, NCT00159796. Registered 8 September 2005 (retrospectively registered).

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Impaired limbic gamma oscillatory synchrony during anxiety-related behavior in a genetic mouse model of bipolar mania.

Publications

Impaired limbic gamma oscillatory synchrony during anxiety-related behavior in a genetic mouse model of bipolar mania.

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