Characterization of age-dependent decline in spontaneous running performance in the heart failure Tgα*44 mice.

In this study we characterize the impact of aging on the spontaneous running performance of the Tgα44 mice (transgenic murine model of chronic heart failure) as compared to the wild-type FVB mice. In 166 mice we have recorded the following parameters of their physical activities in the running wheels: the total distance covered during the experiment (D), the maximal distance covered in single-effort (D), mean time spent on running per 24 h (T), mean running speed (ν), the maximum instantaneous speed of run (ν) and the number of efforts (i.e. the number of running events undertaken by the mice) during 54 days, in four age groups ~4, ~10, ~12 and ≥12.5 months of age. The level of spontaneous running performance of the FVB mice remained essentially unchanged, but a strong impact of aging in the Tgα44 mice on their running performance was found. Namely, the D, D, T and ν in the Tgα44 mice at the age of ≥12.5 months decreased by ~50%, when compared to its level corresponding level at the age of ~4 months, with far lesser effect of aging on their V. Surprisingly, the number of attempts to perform running by the Tgαq44 mice at the age of 4 - 12 months remained essentially unchanged. This suggests that the exercise intolerance of the aging heart failure (HF) mice seems to be more dependent on deterioration of heart and muscles function linked to HF than on a possible ageing-related impairment of the 'willngness' to initiate running, generated by the central nervous system.