15 research outputs found
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Cognitive Deficits in the R6/2 model of Huntington’s Disease and Amelioration with Donepezil
The neurodegenerative disorder Huntington’s disease (HD) is characterized by motor dysfunction, cognitive impairment and psychiatric symptoms. The R6/2 (120 CAG repeats) mouse model of HD recapitulates many of the symptoms of the disease, including marked impairments in cognition and severe motor deficits. As cholinergic function has been reported to be affected in both HD patients and this mouse model, we tested whether treatment with the cholinesterase inhibitor donepezil could improve the R6/2 mice performance in the two-choice swim tank visual discrimination and reversal task. In this test mice are trained to swim towards a light cued platform located on one side of a water-filled tank. Once mice reach an acquisition criterion a reversal ensues. Wild-type and R6/2 mice were dosed with donepezil (0.6 mg/kg/day) or vehicle starting at 8 weeks of age and tested starting at 9 weeks of age. In experiment 1, vehicle-treated R6/2 mice showed a significant deficit during acquisition and reversal as compared to vehicle-treated WT mice. Donepezil improved reversal in the R6/2 group. In experiment 2, we confirmed the beneficial effect of donepezil on reversal in similar conditions. Donepezil had no effect on activity as measured in the open field test or through the latency to reach the platform during the swim test. We suggest that the donepezil-induced improvements in cognitive function observed in the R6/2 transgenic model of HD may reflect amelioration of deficits in cholinergic function that have been reported previously in this model. Further work is required to confirm the findings of these interesting although preliminary studies
Recommended from our members
Cognitive Deficits in the R6/2 model of Huntington’s Disease and Amelioration with Donepezil
The neurodegenerative disorder Huntington’s disease (HD) is characterized by motor dysfunction, cognitive impairment and psychiatric symptoms. The R6/2 (120 CAG repeats) mouse model of HD recapitulates many of the symptoms of the disease, including marked impairments in cognition and severe motor deficits. As cholinergic function has been reported to be affected in both HD patients and this mouse model, we tested whether treatment with the cholinesterase inhibitor donepezil could improve the R6/2 mice performance in the two-choice swim tank visual discrimination and reversal task. In this test mice are trained to swim towards a light cued platform located on one side of a water-filled tank. Once mice reach an acquisition criterion a reversal ensues. Wild-type and R6/2 mice were dosed with donepezil (0.6 mg/kg/day) or vehicle starting at 8 weeks of age and tested starting at 9 weeks of age. In experiment 1, vehicle-treated R6/2 mice showed a significant deficit during acquisition and reversal as compared to vehicle-treated WT mice. Donepezil improved reversal in the R6/2 group. In experiment 2, we confirmed the beneficial effect of donepezil on reversal in similar conditions. Donepezil had no effect on activity as measured in the open field test or through the latency to reach the platform during the swim test. We suggest that the donepezil-induced improvements in cognitive function observed in the R6/2 transgenic model of HD may reflect amelioration of deficits in cholinergic function that have been reported previously in this model. Further work is required to confirm the findings of these interesting although preliminary studies
Comprehensive behavioral and molecular characterization of a new knock-in mouse model of Huntington's disease: zQ175.
Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder characterized by motor, cognitive and psychiatric manifestations. Since the mutation responsible for the disease was identified as an unstable expansion of CAG repeats in the gene encoding the huntingtin protein in 1993, numerous mouse models of HD have been generated to study disease pathogenesis and evaluate potential therapeutic approaches. Of these, knock-in models best mimic the human condition from a genetic perspective since they express the mutation in the appropriate genetic and protein context. Behaviorally, however, while some abnormal phenotypes have been detected in knock-in mouse models, a model with an earlier and more robust phenotype than the existing models is required. We describe here for the first time a new mouse line, the zQ175 knock-in mouse, derived from a spontaneous expansion of the CAG copy number in our CAG 140 knock-in colony [1]. Given the inverse relationship typically observed between age of HD onset and length of CAG repeat, since this new mouse line carries a significantly higher CAG repeat length it was expected to be more significantly impaired than the parent line. Using a battery of behavioral tests we evaluated both heterozygous and homozygous zQ175 mice. Homozygous mice showed motor and grip strength abnormalities with an early onset (8 and 4 weeks of age, respectively), which were followed by deficits in rotarod and climbing activity at 30 weeks of age and by cognitive deficits at around 1 year of age. Of particular interest for translational work, we also found clear behavioral deficits in heterozygous mice from around 4.5 months of age, especially in the dark phase of the diurnal cycle. Decreased body weight was observed in both heterozygotes and homozygotes, along with significantly reduced survival in the homozygotes. In addition, we detected an early and significant decrease of striatal gene markers from 12 weeks of age. These data suggest that the zQ175 knock-in line could be a suitable model for the evaluation of therapeutic approaches and early events in the pathogenesis of HD
Test ages for behavioral work, broken down by test cohort.
<p>Test ages for behavioral work, broken down by test cohort.</p
Rearing frequency in the Open Field (mean ± SEM) of wild type, heterozygous and homozygous mice as a function of age during the dark phase of the diurnal cycle.
<p>Rearing frequency in the Open Field (mean ± SEM) of wild type, heterozygous and homozygous mice as a function of age during the dark phase of the diurnal cycle.</p
Latency to fall from the rotarod (mean ± SEM) of wild type, heterozygous and homozygous mice as a function of age during the dark phase of the diurnal cycle.
<p>Latency to fall from the rotarod (mean ± SEM) of wild type, heterozygous and homozygous mice as a function of age during the dark phase of the diurnal cycle.</p
Overall visit frequency during PhenoCube testing at 37 weeks, broken down into 1 hour bins (A) and summarized across the two complete light/dark periods from lights-on on day 2 (B).
<p>Overall visit frequency during PhenoCube testing at 37 weeks, broken down into 1 hour bins (A) and summarized across the two complete light/dark periods from lights-on on day 2 (B).</p
Total distance covered in the Open Field per 5 minute bin (mean ± SEM) of wild type, heterozygous and homozygous mice as a function of age and test time during the dark phase of the diurnal cycle.
<p>Total distance covered in the Open Field per 5 minute bin (mean ± SEM) of wild type, heterozygous and homozygous mice as a function of age and test time during the dark phase of the diurnal cycle.</p
Qualitative Polymerase Chain Reaction (qPCR) information.
<p>Qualitative Polymerase Chain Reaction (qPCR) information.</p
Grip strength (mean ± SEM) of wild type, heterozygous and homozygous mice as a function of age during the light phase of the diurnal cycle.
<p>Grip strength (mean ± SEM) of wild type, heterozygous and homozygous mice as a function of age during the light phase of the diurnal cycle.</p