Time-course changes in videofluoroscopic findings during developmental and aging stages in mice

Videofluoroscopic swallow study methodology in mice has recently been established; however, details of developmental and age-related changes remain unclear. This study aimed to reveal the changes in swallowing associated with the entire lifespan of mice using the videofluoroscopic swallow study methodology. We tested six age groups of male C57BL/6J mice (4, 8, 16, 54, 77, and 104 weeks old; n = 5 for each group, respectively). The videofluoroscopic swallow study analyzed the bolus area, pharyngeal transit time, interswallow interval, lick-swallow ratio, and lick rate. Significant age differences were found in the bolus area and lick rate. The bolus area increased significantly as the mice grew older. There was a significant increase in the lick rate from 4 to 8 weeks (P < 0.001) and then a significant decrease from 8 to 104 weeks (P < 0.01). No significant difference was observed between the various stages in the lick-swallow ratio, interswallow interval, or pharyngeal transit time. There was a significant positive correlation between the body weight and bolus area. This study revealed the detailed changes in swallowing at each life stage from swallowing maturation to old age in the mice. Our research may serve as a guide for future studies on swallowing in humans.