Early onset deficits on the delayed alternation task in the Hdh(Q92) knock-in mouse model of Huntington's disease.

A number of genetic mouse models of Huntington's disease have been created, in order to examine the pathogenesis of Huntington's disease and to test potential therapeutics. In the present study we demonstrate that the full-length knock-in homozygote Hdh(Q92) mice exhibit impairments at 5 months of age on the delayed alternation task, conducted in 9-hole operant chambers. This test is sensitive to cortico-striatal dysfunction and demonstrates again that although Hdh(Q92) mice do not display an overt motor phenotype, they do exhibit clear impairments that can be related to deficits seen in HD patients. This indicates that if appropriately sensitive tasks are used, the more subtle and specific Hdh(Q92) knock-in model could be of use for the examination of pathogenic mechanisms in Huntington's disease and to test potential therapeutics.