生後早期の光環境は母ラットの概日リズムと養育行動に変化を与え、仔ラットの不安や記憶の障害をもたらす。

抄録

Although dramatic changes of lighting environments are occurring in modern society, the influence of these changes has not been fully elucidated. It is demonstrated that, early life experiences (i.e. maternal care) induce various changes in the function of circadian rhythm, emotionality and memory. Here, we examined whether ELC affected circadian rhythm and maternal care of dam, and the offspring's circadian rhythm, anxiety and memory. Prolonged dark phase (PDP) was used to study the effects of ELC. Dams and their litters were kept in a PDP cycle (L/D=6:18h; postnatal days 2-14) or under a normal condition (L/D=12:12h). Throughout this period, locomotor activity of dams was measured and all cages were video recorded for behavioral scoring. At age of 10-week, behavioral observations of the offsprings were undertaken. Circadian rhythm of locomotor, avoidant behavior, social interaction and object recognition memory were examined. Under PDP, the morning offset of dams' motor activity was delayed and amounts of maternal care decreased for the first 2-7 days of lactation. In the adult offspring, circadian rhythm of locomotor was not affected. Whereas PDP increased avoidant behavior, PDP decreased social interaction and memory. In conclusion, the PDP mothers showed impaired circadian rhythm and maternal care, and the offsprings exhibited depressive-like behaviors. Therefore, it is conceivable that ELC may alter mother-infant interaction and subsequently change the offsprings' emotionality. [J Physiol Sci. 2006;56 Suppl:S96]