Effects of Reversed Light-Dark Cycle on Pregnant Mice and their Fetuses

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  • 明暗サイクル逆転が母胎に及ぼす影響
  • メイアン サイクル ギャクテン ガ ボタイ ニ オヨボス エイキョウ

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Abstract

The purpose of this study was to investigate the effect on pregnant mice and their fetuses of changes in daily light-dark cycles. <br>Mice were randomly divided into four groups: <br>1. C group : control group bred in daily common light-dark cycle (Light period 9:00～21:00, dark period 21:00～9:00) <br>2. S group : shift group bred in daily reverse light-dark cycles. Day 1 is common cycle, day 2 is reversed (light period 21:00～9:00, dark period 9:00～21:00), day 3 is common cycle, day 4 is reversed, etc. <br>3. CS group: control-shift group bred for the first week in the common cycle, then thereafter bred in the shift cycle. <br>4. SC group: shift-control group bred for the first week in the shift cycle, then thereafter bred in the common cycle. <br>Although the body weight of the S and SC groups during the first week were significantly lighter than of the C and CS groups, that of the S group increased and that of the SC group decreased compared to the C group just before delivery, but not significantly. Growth of the fetus and placenta in the S group was significantly retarded during the first week, while just before delivery the average fetus weight of the S group was heavier compared to that of the C group. Growth of the fetus weights of the CS and SC groups was retarded in the first week after being changed the shift cycle. Furthermore, this retardation in SC group remained in the common cycle while was introduced after a week of the shift cycle. <br>These findings suggest that the exposure to the shift cycle induces stress which results in retarded growth of the fetus.

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