Bosc M J, Nicolle A
Reprod Nutr Dev (1980). 1980;20(3A):735-45. doi: 10.1051/rnd:19800416.
Four groups of normal rats have been studied to elucidate the effect on the time of birth of four different light regimes applied throughout pregnancy (day 1: beginning of pregnancy). The results showed that the time of parturition (onset of expulsion) depended on the light treatment: the longer the duration of the daily illumination, the longer pregnancy lasted. With a 14 hrs light regime, the births occurred during two main periods: 50 p. 100 before 8 p.m. on day 22 of pregnancy and 36 p. 100 between 5 a.m. and 1 p.m. on day 23. With 8 h of light per day, 69 p. 100 of the rats delivered before 9 p.m. on day 22 and 85 p. 100 before 5 a.m. of day of pregnancy. On the other hand, only 22 and 49 p. 100 of the rats gave birth at the same periods under a 20 hrs light regime. Parturition under a completely dark photoperiod occurred mainly before day 23 of pregnancy and with a different rhythm than those of the preceding groups. The influence of maternal adrenalectomy on the time of parturition was determined using two light regimes (14 or 20 hrs of light per day). Under those conditions, the length of pregnancy was modified; parturition occurred earlier in adrenalectomized than in the normal rats submitted to the same light regime. These results suggest that the effect of light on the time of birth in the rat involves adrenal gland secretions.
为了阐明整个孕期（第1天：怀孕开始）应用的四种不同光照方案对出生时间的影响，对四组正常大鼠进行了研究。结果表明，分娩时间（开始排出胎儿）取决于光照处理：每日光照时间越长，孕期持续时间越长。在14小时光照方案下，分娩发生在两个主要时间段：怀孕第22天晚上8点前占50%，怀孕第23天上午5点至下午1点之间占36%。每天光照8小时，69%的大鼠在怀孕第22天晚上9点前分娩，85%在怀孕第22天凌晨5点前分娩。另一方面，在20小时光照方案下，只有22%和49%的大鼠在相同时间段分娩。在完全黑暗的光周期下分娩主要发生在怀孕第23天之前，且节律与前几组不同。使用两种光照方案（每天14或20小时光照）确定了母体肾上腺切除术对分娩时间的影响。在这些条件下，孕期长度发生了改变；肾上腺切除的大鼠比接受相同光照方案的正常大鼠分娩更早。这些结果表明，光照对大鼠出生时间的影响涉及肾上腺分泌。
