Postnatal realignment of circadian PER2::LUC rhythms in the submandibular gland during oral feeding development.

OBJECTIVES

Circadian rhythms in peripheral organs undergo dynamic reorganization during postnatal development. However, the mechanisms underlying the maturation of circadian clocks in the salivary glands, particularly in relation to feeding behavior, remain poorly understood. In this study, we aimed to characterize the developmental maturation of circadian rhythms in the mouse submandibular gland (SMG).

METHODS

PERIOD2::LUCIFERASE bioluminescence rhythms were recorded from cultured suprachiasmatic nucleus (SCN) and SMG tissues isolated from mice at postnatal days 0, 1, 7, 14, 21, and 28, and 8 weeks. Maternal behavior and pup feeding activity were continuously monitored using infrared video recording. Peak phases and circadian periods were analyzed to evaluate developmental changes.

RESULTS

Robust circadian oscillations were observed in the SCN tissue at all developmental stages, with stable periods and peak phases. In contrast, rhythms in the SMG were rapidly damped in culture, and exhibited a progressive phase shift from the light phase to the middle of the dark phase during postnatal development. Circadian periods in both tissues remained close to 24 h throughout development. Behavioral analyses revealed that developmental changes in maternal care and feeding activity were closely associated with the phase realignment of SMG rhythms. After weaning, SMG peak phases resembled those in adult mice.

CONCLUSIONS

Postnatal maturation of circadian rhythms in the SMG is characterized by progressive phase realignment that parallels the transition from suckling to independent feeding. These findings suggest that developmental coordination between feeding behavior and peripheral clock machinery contributes to the establishment of circadian regulation of salivary function.