¹University of South Carolina School of Medicine, Pharmacology, Physiology, and Neuroscience, Columbia, United States, ²University of Maryland School of Medicine, Psychiatry, Baltimore, United States, ³University of Ferrara, Life Sciences and Biotechnology, Ferrara, Italy

Background: Elevated brain kynurenic acid (KYNA) levels are implicated in the pathophysiology of schizophrenia (SZ). As an antagonist of cholinergic and glutamatergic neurotransmission, elevated KYNA levels may be causally related to cognitive dysfunctions in SZ. We developed an embryonic kynurenine model (“EKyn”; Beggiato et al., 2018) in mice to mimic elevated KYNA levels during neurodevelopment and study cognitive function in adulthood.

Aims & Objectives: We presently investigated if perinatal choline supplementation (Freedman et al., 2022), an essential nutrient and agonist of α7nACh receptors, would alleviate adverse learning outcomes in EKyn adult offspring.

Method: Pregnant C57Bl/6J mice were fed a standard diet (0.1% choline chloride) or choline-supplemented diet (0.5% choline chloride) from embryonic day (ED) 11 to postnatal day (PD) 21. From ED 11 to ED 18 each diet remained control (ECon) or was laced with the KYNA precursor kynurenine (50 mg/day; EKyn). Upon weaning, all offspring received control rodent chow until experimental testing in adulthood (PD 56-85). Separate cohorts of adult, male and female offspring were then assessed in biochemical (in vivo microdialysis in prefrontal cortex; N=10 per group), electrophysiology (ex vivo recordings of interhemispheric transmission; N=17-22 per group), and behavioral studies (Barnes maze; N=13-30 per group).

Results: EKyn male and female offspring had significantly higher KYNA in the prefrontal cortex in adulthood (64% increase; t = 3.483, Df = 18, P = 0.03) and significantly delated interhemispheric transmission (F_1,74 = 16.11, P = 0.0001). EKyn exposure significantly impacts spatial learning such that latency to find the escape box (males: F_1,69 = 5.613, P = 0.02; females: F_1,67 = 3.785, P = 0.05) and errors (males: F_1,70 = 6.958, P = 0.01; females: F_1,67 = 6.591, P = 0.01) were increased in the Barnes maze across days. On the last day, latency was significantly higher in EKyn males (P = 0.001) and females (P = 0.002) and this impairment was reversed in offspring of mothers that received choline supplemented diet with EKyn exposure (males: P = 0.005; P = 0.02; females: P = 0.05). Taken together, EKyn impaired Barnes Maze performance in both sexes, but choline reversed these deficits, suggesting rescue of hippocampal-dependent learning. Analysis of Barnes maze behavior revealed significant difference in the use of random, serial, or direct search strategies across learning days between both sexes of ECon and EKyn (P < 0.05).

Discussion & Conclusions: Physiological and behavioral abnormalities are seen in adult EKyn mice with concurrent elevations in brain KYNA levels indicating that prolonged treatment with kynurenine during the embryonic period causes permanent, functionally significant changes in brain development in these experimental animals. Understanding the role of choline supplementation, which mitigated cognitive impairments in EKyn offspring, as a potential intervention for alleviating prenatal risk factors associated with cognitive dysfunction and SZ helps to inform future treatment strategies.