Supplementation of L-Ornithine Could Increase Sleep-like Behavior in the Mouse Pups

Along the maternal-fetal-neonatal axis, one of the problems relating to the maternal-neonatal axis is infant sleep problems including nighttime crying. One possible solution could be to provide the newborn with sleep-promoting ingredients through breast milk or formula. So far, it has been reported that L-ornithine has a sleep-related effect. Therefore, we investigated the effect of dietary L-ornithine on maternal mouse plasma and milk L-ornithine levels in Experiment 1. In Experiment 2, a single dose of L-ornithine was applied to know the time-course changes in plasma, mammary gland and milk L-ornithine levels. Experiment 3 was conducted to confirm sleep behavior as well as changes in polyamine levels in milk. L-Ornithine levels in maternal plasma significantly increased by both dietary regimen and single oral administration in Experiments 1 and 2. Both L-ornithine treatments also increased its levels in milk, although not to a concentration as high as in plasma. In Experiment 3, the level of polyamines, which are metabolized from L-ornithine, did not significantly differ after L-ornithine administration. In sleep-like behavior observations, the average concentration of L-ornithine in milk did not increase the sleep-like behavior of mouse pups. However, more concentrated L-ornithine solutions can significantly increase sleep-like behavior. These results revealed that even if mothers ingested L-ornithine to increase L-ornithine levels in breast milk, it is difficult to promote sleep in newborns. Because it is difficult to raise L-ornithine in breast milk to sleep-inducing levels, L-ornithine added formula may partially improve infant sleep and has the potential for preventing infant sleep problems such as nighttime crying.