【Purposes】It has been reported that there is a correlation between the spread of tau pathology in the brain and the progression of cognitive impairment in Alzheimer's disease.　
Recently, a mouse model of tau propagation using wild-type mice and synthetic tau fibrils was reported (Masuda-Suzukake et al., Brain Commun., 2020), but behavioral evaluation of the mice was not conducted. In this study, cognitive function and neurotransmitter levels were assessed in this mouse model.
【Methods】We injected synthetic soluble tau or tau fibrils bilaterally into the hippocampus of 9-week-old C57BL/6J mice. The cognitive function was assessed 3 months and 6 months after injection. The levels of neurotransmitters and their metabolites in the hippocampus were measured using HPLC-ECD 6 months after the injection.
【Results・discussions】The mice injected with tau fibrils showed cognitive impairment at 3 months and 6 months after injection, while those injected with soluble tau did not show cognitive impairment. In the hippocampus, acetylcholine levels were decreased in both groups compared with the control group, and the mice injected with tau fibrils showed a significant decrease. The results suggest that the accumulation and propagation of tau in the brain impair cognitive function and decrease acetylcholine levels in the hippocampus.