title: In vivo evaluation of cellular activity in αCaMKII heterozygous knockout mice using manganese-enhanced magnetic resonance imaging (MEMRI).
abstract: The alpha-calcium/calmodulin-dependent protein kinase II (αCaMKII) is a serine/threonine protein kinase predominantly expressed in the forebrain, especially in the postsynaptic density, and plays a key role in synaptic plasticity, learning and memory. αCaMKII heterozygous knockout (HKO) mice exhibit abnormal emotional and aggressive behaviors and cognitive impairments and have been proposed as an animal model of psychiatric illness. Our previous studies have shown that the expression of immediate early genes (IEGs) after exposure to electric foot shock or after performing a working memory task is decreased in the hippocampus, central amygdala, and medial prefrontal cortex of mutant mice. These changes could be caused by disturbances in neuronal signal transduction; however, it is still unclear whether neuronal activity is reduced in these regions. In this study, we performed in vivo manganese-enhanced magnetic resonance imaging (MEMRI) to assess the regional cellular activity in the brains of αCaMKII HKO mice. The signal intensity of MEMRI 24 h after systemic MnCl2 administration reflects functional increases of Mn(2+) influx into neurons and glia via transport mechanisms, such as voltage-gated and/or ligand-gated Ca(2+) channels. αCaMKII HKO mice demonstrated a low signal intensity of MEMRI in the dentate gyrus (DG), in which almost all neurons were at immature status at the molecular, morphological, and electrophysiological levels. In contrast, analysis of the signal intensity in these mutant mice revealed increased activity in the CA1 area of the hippocampus, a region crucial for cognitive function. The signal intensity was also increased in the bed nucleus of the stria terminalis (BNST), which is involved in anxiety. These changes in the mutant mice may be responsible for the observed dysregulated behaviors, such as cognitive deficit and abnormal anxiety-like behavior, which are similar to symptoms seen in human psychiatric disorders.
authors.affiliation: 1Molecular Neuroimaging Program, Molecular Imaging Center, National Institute of Radiological Sciences Chiba, Japan ; 2Division of Systems Medical Science, Institute for Comprehensive Medical Science, Fujita Health University Toyoake, Aichi, Japan ; 3Japan Science and Technology Agency (JST), Core Research for Evolutional Science and Technology (CREST) Kawaguchi, Saitama, Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Hattori
authors.forename: Hideo
authors.initials: H
authors.lastname: Hagihara
authors.forename: Koji
authors.initials: K
authors.lastname: Ohira
authors.forename: Ichio
authors.initials: I
authors.lastname: Aoki
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Saga
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Suhara
authors.forename: Makoto
authors.initials: M
authors.lastname: Higuchi
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Miyakawa
keywords: bed nucleus of stria terminalis; dentate gyrus; hippocampus; immature; manganese-enhanced MRI; psychiatric disorder; schizophrenia; αCaMKII