Aging decreases preferences for salts, but not for sucrose, and alters morphology of fungiform taste pores in mice

Mice are commonly used for laboratory research, due in large part to the widespread advancement in the genetic toolbox, such as reporters, knock-in, and knockout mice. The effects of aging on the taste system in mice have been largely unstudied. The aim of this study was to examine whether taste preferences to sucrose, NaCl, and NH4Cl were associated with aging and changes in ultrastructural characteristics of fungiform taste pores using scanning electron microscopy. Thirty-minute 2-bottle preference tests in wild-type mice indicated that preferences for NaCl and NH4Cl, but not sucrose, were significantly different in aged mice (16 to 17 months old) relative to young mice (5 months old). In the same animals, we found that the percentage of fungiform papilla with taste pores present was significantly reduced in the aged group. These findings are consistent with our recent study in rats, where aging had a significant impact on chorda tympani nerve responses to salt and ultrastructural characteristics of fungiform taste pores. Collectively, these data suggest that aging significantly affects fungiform taste pore morphology and has a significant impact on taste processing. Future studies investigating the factors that form and maintain taste pores are of critical importance as the pore is necessary for taste stimuli access to taste bud cells.