Abstract
Valproic acid (VPA) is used to establish models of experimental autism. The present study investigated the developmental exposure effect of VPA on postnatal hippocampal neurogenesis in accordance with the exposure scheme of OECD Test Guideline 426 adopted for developmental neurotoxicity. Pregnant rats were administered drinking water containing 0, 667, or 2000 ppm VPA from gestational day 6 until day 21 post-delivery. In the subgranular zone (SGZ) and granule cell layer (GCL) of offspring, the number of granule cell lineage subpopulations remained unchanged upon weaning. However, in the hilus of the dentate gyrus, the number of reelin+ interneurons decreased at ≥667 ppm, and the number of PVALB+ or GAD67+ interneurons decreased at 2000 ppm. Conversely, Reln and Gad1 transcript levels increased at 2000 ppm, but Pvalb and Grin2d decreased, in the dentate gyrus. At the adult stage, PCNA+ proliferating SGZ cells, NeuN+ postmitotic SGZ/GCL neurons, and ARC+ or COX2+ GCL neurons increased at ≥667 ppm. In the dentate hilus, decreases in GAD67+ interneuron subpopulations and Grin2d transcript levels sustained at 2000 ppm. These results suggested that VPA primarily targets interneurons by developmental exposure, and this is followed by late effects on granule cell lineages, likely by influencing SGZ cell proliferation and synaptic plasticity. A reduced population of reelin+ or PVALB+ interneurons did not affect distribution of granule cell lineage subpopulations upon weaning. The late effect on neurogenesis, which resulted in increased GCL neurons, might be the result of a sustained decrease in GAD67+ interneurons expressing NR2D encoded by Grin2d.
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Abbreviations
- ARC:
-
Activity-regulated cytoskeleton-associated protein
- BLBP:
-
Brain lipid-binding protein
- BW:
-
Body weight
- CALB1:
-
Calbindin-D-28K
- CALB2:
-
Calbindin-D-29K
- COX2:
-
Cyclooxygenase 2
- C T :
-
Threshold cycle
- DAB:
-
3,3′-Diaminobenzidine
- DCX:
-
Doublecortin
- DNT:
-
Developmental neurotoxicity
- FOS:
-
FBJ osteosarcoma oncogene
- GABA:
-
γ-Aminobutyric acid
- GAD67:
-
Glutamate decarboxylase 67
- GCL:
-
Granule cell layer
- GD:
-
Gestational day
- GFAP:
-
Glial fibrillary acidic protein
- HDAC:
-
Histone deacetylase
- i.p.:
-
Intraperitoneal
- NeuN:
-
Neuron-specific nuclear protein
- NMDA:
-
N-Methyl-d-aspartic acid
- OECD:
-
Organisation for Economic Co-operation and Development
- PCNA:
-
Proliferating cell nuclear antigen
- PCR:
-
Polymerase chain reaction
- PFA:
-
Paraformaldehyde
- PND:
-
Postnatal day
- PVALB:
-
Parvalbumin
- SGZ:
-
Subgranular zone
- SOX2:
-
SRY (sex-determining region Y)-box 2
- TBR2:
-
T-box brain protein 2
- TUNEL:
-
Terminal deoxynucleotidyl transferase dUTP nick end labeling
- VPA:
-
Valproic acid
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Acknowledgments
The authors thank Mrs. Shigeko Suzuki for her technical assistance in preparing the histological specimens. The authors thank Mr. Hirotada Murayama and Miss Rei Nagahara for their technical assistance in immunohistochemical analysis. This work was supported by a Grant from the Ministry of Economy, Trade and Industry (METI), Japan.
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All procedures in this study were conducted in accordance with the Guidelines for Proper Conduct of Animal Experiments (Science Council of Japan, 1 June 2006) and according to the protocol approved by the Animal Care and Use Committee of The Tokyo University of Agriculture and Technology. All efforts were made to minimize animal suffering.
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Watanabe, Y., Murakami, T., Kawashima, M. et al. Maternal Exposure to Valproic Acid Primarily Targets Interneurons Followed by Late Effects on Neurogenesis in the Hippocampal Dentate Gyrus in Rat Offspring. Neurotox Res 31, 46–62 (2017). https://doi.org/10.1007/s12640-016-9660-2
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DOI: https://doi.org/10.1007/s12640-016-9660-2