Analysis of aging-dependent changes in taste sensitivities of the senescence-accelerated mouse SAMP1.

To investigate aging-dependent changes in taste sensitivities, we performed behavioral tests regarding taste sensitivity among young and old SAMP1 mice. In this senescence-accelerated mice model, dramatic changes in taste sensitivities were observed at least 70 weeks old. As for in a brief access test, old mice showed significantly increased taste sensitivity to bitter, salty, sweet, and umami tastes. On the other hand, in a two-bottle test, avoidance of bitter and salty tastes increased, while preference for umami decreased with aging. To investigate the participation of peripheral taste detection systems in the observed changes, we analyzed both the expression of representative taste-related molecules and also turnover rates of taste bud cells. The mRNA expressions of the bitter taste receptor Tas2r105 and its coupled G protein gustducin were significantly decreased with aging. However, the majority of molecules tested did not show significant expression changes. In addition, no significant differences in the turnover rates of taste bud cells were observed between the two age groups. These results suggest that the changes in taste sensitivity of SAMP1 mice due to aging are caused by factors other than the deterioration of taste detection systems in the oral cavity.