Pregnancy Impacts Maternal Sleep: Focus on Kynurenine Pathway Activation in Female Rats

Study Objectives: Poor maternal sleep is associated with adverse health outcomes for women and their offspring, and perturbations to tryptophan metabolism through the kynurenine pathway (KP) may contribute. Kynurenic acid (KYNA), a neuroactive KP metabolite and endogenous modulator of glutamatergic and cholinergic neurotransmission, is of particular interest because elevated KYNA has been linked to altered sleep-wake behavior and neurodevelopmental outcomes. Because sleep patterns and KP metabolism change during pregnancy, we tested whether pregnancy modifies the effects of kynurenine supplementation on sleep-wake architecture. Methods: To model enhanced KP metabolism, we used the embryonic kynurenine (EKyn) model, in which the maternal diet is supplemented with kynurenine, the initial KP metabolite, during the last week of gestation. Using a within-subject design, we evaluated sleep-wake parameters in pregnant and non-pregnant female rats and assessed KYNA in brain and saliva. Results: Pregnancy increased dark phase NREM and REM sleep in control-fed (ECon) dams, a pattern largely maintained in EKyn dams. However, near parturition, EKyn dams exhibited reduced light phase REM sleep that was not observed in controls. In non-pregnant females, kynurenine supplementation produced a stronger phenotype, consistently reducing light phase REM sleep across treatment days. During pregnancy, kynurenine-associated sleep effects were detectable only when compared to within-subject non-pregnant baseline. Salivary KYNA distinguished kynurenine-fed females from matched controls and correlated with brain KYNA levels. Conclusion: These findings show that pregnancy reshapes sleep-wake architecture and attenuates, but does not eliminate, kynurenine-associated REM sleep disruption, implicating KP metabolism and potentially elevated brain KYNA in maternal sleep regulation.