Department of Environmental Management and Control, School of Health Sciences, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, Fukuoka 807-8555, Japan.
Division of Pharmacology, National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki, Kanagawa 210-9501, Japan; Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Neurotoxicology. 2018 Mar;65:1-8. doi: 10.1016/j.neuro.2018.01.001. Epub 2018 Jan 5.
Prenatal valproic acid (VPA) exposure is a well-known animal model of autism spectrum disorder (ASD) that produces alterations in embryonic and adult neurogenesis as well as adolescent/adulthood neurobehavioral phenotypes. However, the effects of prenatal VPA exposure on neural network excitability, especially during the synaptogenic period around eye opening, are not fully understood. In this study, we orally administered VPA (300 mg/kg) to pregnant Wistar rats on gestation day 15 and subsequently performed field potential recording in the CA1 area of hippocampal slices obtained from control (saline-exposed) and VPA-exposed rat pups between postnatal day (PND) 13 and PND18. In control slices, we observed an abrupt enhancement of stimulation-dependent responses including population spike (PS) amplitudes and field excitatory postsynaptic potential (fEPSP) slopes at PND16, which coincided with the average day of eye opening. In contrast, VPA-exposed pups exhibited delayed eye opening (PND17) and gradual rather than abrupt increases in PS amplitudes and fEPSP slopes over the duration of the synaptogenic period. We next investigated the involvement of ambient GABA (γ-aminobutyric acid) in PS generation using bicuculline methiodide (BMI), a GABA type A (GABA) receptor antagonist. In control slices, BMI enhanced PS amplitudes during PND14-15 (before eye opening) and had little effect thereafter during PND16-17; a subsequent regression model analysis of BMI ratios (the ratio of PS amplitudes in the presence and absence of BMI) indicated a possible developmental change between these periods. In contrast, almost identical regression models were obtained for BMI ratios during PND14-15 and PND16-17 in the VPA-exposed group, indicating the absence of a developmental change. Our results suggest that prenatal VPA exposure accelerates the development of hippocampal excitability before eye opening. Moreover, our experimental model can be used as a novel approach for the evaluation of developmental neurotoxicity.
产前丙戊酸（VPA）暴露是一种众所周知的自闭症谱系障碍（ASD）动物模型，它会导致胚胎和成年神经发生以及青少年/成年神经行为表型发生改变。然而，产前 VPA 暴露对神经网络兴奋性的影响，特别是在睁眼前后的突触发生期，尚未完全阐明。在这项研究中，我们在妊娠第 15 天给怀孕的 Wistar 大鼠口服 VPA（300mg/kg），随后在出生后第 13 天至第 18 天从对照（盐水暴露）和 VPA 暴露的大鼠幼崽中获得的海马切片的 CA1 区进行场电位记录。在对照切片中，我们观察到刺激依赖性反应的突然增强，包括群体峰（PS）幅度和场兴奋性突触后电位（fEPSP）斜率，这与平均睁眼日相对应。相比之下，VPA 暴露的幼崽表现出睁眼延迟（PND17），并且在突触发生期间，PS 幅度和 fEPSP 斜率的增加是逐渐的而不是突然的。接下来，我们使用 GABA 型 A（GABA）受体拮抗剂荷包牡丹碱甲碘化物（BMI）研究 PS 产生中环境 GABA（γ-氨基丁酸）的参与。在对照切片中，BMI 在 PND14-15 期间（在睁眼之前）增强了 PS 幅度，并且在此之后的 PND16-17 期间几乎没有影响；BMI 比率（存在和不存在 BMI 时 PS 幅度的比率）的后续回归模型分析表明，在这些时期之间可能存在发育变化。相比之下，在 VPA 暴露组中，PND14-15 和 PND16-17 期间的 BMI 比率获得几乎相同的回归模型，表明不存在发育变化。我们的结果表明，产前 VPA 暴露会在睁眼前加速海马兴奋性的发育。此外，我们的实验模型可以用作评估发育神经毒性的新方法。
