Prenatal fear stress impairs cognitive development in offspring rats by disrupting placental amino acid transport

doi:10.12122/j.issn.1673-4254.2025.08.02

Abstract

Abstract:

Objective To investigate the impact of prenatal fear stress on placental amino acid transport and emotion and cognition development in offspring rats. Methods Thirty pregnant Wistar rats were randomized equally into control and fear stress (induced using an observational foot shock model) groups. In each group, placental and serum samples were collected from 6 dams on gestational day 20, and the remaining rats delivered naturally and the offspring rats were raised under the same conditions until 8 weeks of age. Emotional and cognitive outcomes of the offspring rats were assessed with behavioral tests, and placental structure was examined using HE staining. Bioinformatics analysis was used to identify differentially expressed placental transporter genes under fear stress. The expressions of system A and system L amino acid transporters, along with other specialized transporters, were detected using qRT-PCR and Western blotting. Fetal serum amino acid concentrations were determined by HPLC. The correlations between fetal amino acid levels and behavioral outcomes of the offspring rats were analyzed. Results The dams with fear stress showed reduced open-field activity and increased freezing behavior with significantly decreased placental weight, fetal weight, and fetal-to-placental ratio. Bioinformatics analysis revealed 28 differentially expressed transporter genes involved mainly in amino acid transport. In the fear stress group, fetal serum amino acid levels were significantly lowered and Slc38a1, Slc43a1, Slc43a2, Slc7a8, Slc6a6, Slc1a1 and Slc6a9 mRNA and protein expressions were all downregulated. The offspring rats in fear stress group exhibited decreased novel object preference and spontaneous alternation with reduced open arm exploration and increased immobility in emotional tests. Lower early-life amino acid levels was found to correlate with impaired adult cognition. Conclusion Prenatal fear stress in rats impairs placental amino acid transporter expression and reduces fetal serum amino acid levels, potentially contributing to long-term cognitive deficits in the offspring rats.

Key words: fear stress, placenta, amino acid transport, offspring emotion, cognition development

Zhixin DU, Yueyang WANG, Liping YANG, Junlin HOU, Jianhua SUN, Pengbei FAN, Yaohui WANG, Xiaolin LI. Prenatal fear stress impairs cognitive development in offspring rats by disrupting placental amino acid transport[J]. Journal of Southern Medical University, 2025, 45(8): 1581-1588.

Figures/Tables 11

Tab.1 Sequences of primers for RT-qPCR

Name of primers	Primer sequence 5'-3'
GAPDH-F	CTGGAGAAACCTGCCAAGTATG
GAPDH-R	GGTGGAAGAATGGGAGTTGCT
Slc38a2-F	CGTTCACCTCCTCCTCAAGACT
Slc38a2-R	TTCAGATACCACAGCCCATTCG
Slc38a1-F	CGTTCACCTCCTCCTCAAGACT
Slc38a1-R	TTCAGATACCACAGCCCATTCG
Slc38a4-F	ATGAAGATGCCGAAAGTCAGAAG
Slc38a4-R	GGTGAACCGAGTAGAGCGATAGA
Slc43a1-F	TTCTATTCCAGTCTATGCCCAGC
Slc43a1-R	CAAGGCCATAAGAGTGCAGGAT
Slc43a2-F	TGGGCATCATCATGGACAAGTAT
Slc43a2-R	AAGGTAACTGCTGAGGAAGCGTAG
Slc6a6-F	GAAGGGTTATCGTCGGGAAAT
Slc6a6-R	ATACATGCCACCCTCCGTCA
Slc1a1-F	ATCGTGGTAGGAGTCTTGGTTCG
Slc1a1-R	AGGATTACAGCAATGACGGTGGT
Slc6a9-F	ACTACGCAGCCAGCTTCTCCTT
Slc6a9-R	TGGTAGTGGTTGTAAGTGATTGGC

Fig.1 Impact of prenatal fear stress on behaviors of pregnant rats. A: Time spent in the central area in open field test; B: Number of grid crossings in open field test; C: Freezing time in contextual Fear Paradigm; D: Percentage of freezing time in contextual Fear Paradigm. ***P<0.001 vs Control group.

Fig.2 Impact of prenatal fear stress on placental weight (PW) and fetal weight (FW). A: Placental and fetal weight; B: Placental-Fetal ratio. *P<0.05,**P<0.01,***P<0.001 vs Control group.

Fig.3 Effect of prenatal fear stress on placental structure (HE staining, Scale bar=500 μm). A: Control group. B: Fear stress group. D: Decidua zone; Jz: Junctional zone; Lab: Labyrinth zone.

Fig.4 Bioinformatics analysis of the placenta under prenatal fear stress. A: Venn diagram. B: Gene ontology analysis. C: Kyoto encyclopedia of genes and genomes pathway analysis. DEGs: Differentially expressed genes.

Fig.5 Effect of prenatal fear stress on protein (A) and mRNA (B) expressions of system A amino acid transporters in the placenta. *P<0.05, ***P<0.001 vs Control group.

Fig.6 Effect of prenatal fear stress on protein (A) and mRNA (B) expressions of system L amino acid transporters in the placenta. *P<0.05, **P<0.01 vs Control group.

Fig.7 Effect of prenatal fear stress on protein (A) and mRNA (B) expressions of Slc6a6, Slc1a1 and Slc6a9. *P<0.05, **P<0.01,***P<0.001 vs Control group.

Fig.8 Effect of prenatal fear stress on serum amino acid levels in fetal mice.GLU: Glutamate; ASP: Aspartate; GLY: Glycine; SER: Serine; TAU: Taurine; GABA: Gamma-aminobutyric acid. **P<0.01,***P<0.001 vs Control group.

Fig.9 Effect of prenatal fear stress on behaviors of adult offspring rats. A: Percentage of open arm time in elevated plus maze test. B: Immobility time in tail suspension test. C: Novel object preference index in novel object recognition test. D: Spontaneous alternation rate in Y-maze test (n=10). **P<0.01,***P<0.001 vs Control group.

Fig.10 Correlation analysis of serum glutamate (A), aspartate (B), glycine (C), serine (D), taurine (E) and gamma-aminobutyric acid (F) levels with behavioral performance in fetal rats.

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