Abstract

Introduction

Avoidance learning in inbred I/Ln mice

Spontaneous behavior of I/Ln and BX mice

Brain metabolic mapping of hybrid acallosal mice

Conclusions

Discussion
Board

ADHD has been sometimes attributed to a reduced interhemispheric cross-talk caused by hypoplasia of the corpus callosum. The inbred mouse strain I/LnJ shows total callosal agenesis with complete penetrance, and behavioral features which may resemble ADHD. In the open-field, when compared to normal mice of the strain C57Bl/6, acallosal mice show significantly higher activity, move faster, often along bended trajectories (circling), and show significantly lower intersession habituation. In order to disentangle the influences of the genetic background from the effects of the callosal agenesis, we undertook crossing studies between I/LnJ and C57Bl/6 mice, obtaining hybrids with missing or variably sized corpus callosum. A regional cerebral 2-deoxyglucose mapping using 12 hybrid acallosals and 10 normal C57Bl/6 mice that were freely moving in the open-field revealed significantly higher 2-deoxyglucose uptake in the septal and basal forebrain regions, as well as larger metabolic asymmetries in the brain of acallosal mice. Higher activity in the center of the open.field correlated with higher activation of the right cerebral cortex in acallosal mice. No significant correlations, however, were found between the amount of locomotor activity and the relative uptake of 2-deoxyglucose in any brain region. Future investigations of hybrid mice with different degrees of callosal agenesis are needed to elucidate the functional background of the hyperactivity of I/Ln mice, as well as to disentangle the linkage between hyperactivity/attention deficit and interhemispheric connectivity. Supported by SNF 96. 31.46691.96

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Presentation Number SAmagara,f.0716
Keywords: corpus callosum, agenesis, mouse strain, I/ln, open-field