Liu Xiao, Yuan Jizhen, Guang Yu, Wang Xiaoxia, Feng Zhengzhi
School of Psychology, Army Medical University, Chongqing, China.
Department of Microbiology, College of Basic Medical Sciences, Army Medical University, Chongqing, China.
Front Neurosci. 2018 Aug 29;12:613. doi: 10.3389/fnins.2018.00613. eCollection 2018.
Microstructural alterations in the hippocampus may underlie stress-related disorders and stress susceptibility. However, whether these alterations are pre-existing stress vulnerability biomarkers or accumulative results of chronic stress remain unclear. Moreover, examining the whole hippocampus as one unit and ignoring the possibility of a lateralized effect of stress may mask some stress effects and contribute to the heterogeneity of previous findings. After C57BL/6 mice were exposed to a 10-day chronic social defeat stress (CSDS) paradigm, different stress phenotypes, i.e., susceptible ( = 10) and resilient ( = 7) mice, were discriminated by the behavior of the mice in a social interaction test. With diffusion tensor imaging (DTI) scans that were conducted both before and after the stress paradigm, we evaluated diffusion properties in the left and right, dorsal (dHi) and ventral hippocampus (vHi) of experimental mice. A significantly lower fractional anisotropy (FA) was found in the right vHi of the susceptible mice prior to the CSDS paradigm than that found in the resilient mice, suggesting that pre-existing microstructural abnormalities may result in stress susceptibility. However, no significant group differences were found in the post-stress FA values of any of the hippocampal regions of interest (ROIs). In addition, mean diffusivity (MD) and radial diffusivity (RD) values were found to be significantly greater only in the right dHi of the resilient group compared to those of the susceptible mice. Furthermore, a significant longitudinal decrease was only observed in the right dHi RD value of the susceptible mice. Moreover, the social interaction (SI) ratio was positively related to post-stress left MD, right dHi MD, and right dHi RD values and the longitudinal right dHi MD percent change. Meanwhile, a negative relationship was detected between the SI ratio and bilateral mean of the post-stress left relative to right vHi FA value, highlighting the important role of right hippocampus in stress-resilience phenotype. Our findings demonstrated different longitudinal microstructural alterations in the bilateral dHi and vHi between stress-susceptible and resilient subgroups and indicated a right-sided lateralized stress effect, which may be useful in the diagnosis and prevention of stress-related disorders as well as their intervention.
海马体的微观结构改变可能是应激相关障碍和应激易感性的基础。然而，这些改变是预先存在的应激易感性生物标志物还是慢性应激的累积结果仍不清楚。此外，将整个海马体作为一个整体进行研究，而忽略应激的侧化效应的可能性，可能会掩盖一些应激效应，并导致先前研究结果的异质性。将C57BL/6小鼠暴露于为期10天的慢性社会挫败应激（CSDS）范式后，通过社交互动测试中小鼠的行为区分出不同的应激表型，即易感（n = 10）和 resilient（n = 7）小鼠。通过在应激范式前后进行的扩散张量成像（DTI）扫描，我们评估了实验小鼠左右侧、背侧（dHi）和腹侧海马体（vHi）的扩散特性。在CSDS范式之前，易感小鼠右侧vHi的分数各向异性（FA）显著低于resilient小鼠，这表明预先存在的微观结构异常可能导致应激易感性。然而，在任何感兴趣的海马区（ROI）的应激后FA值中未发现显著的组间差异。此外，发现resilient组仅右侧dHi的平均扩散率（MD）和径向扩散率（RD）值显著高于易感小鼠。此外，仅在易感小鼠右侧dHi的RD值中观察到显著的纵向下降。此外，社交互动（SI）比率与应激后左侧MD、右侧dHi MD和右侧dHi RD值以及纵向右侧dHi MD百分比变化呈正相关。同时，在SI比率与应激后左侧相对于右侧vHi FA值的双侧平均值之间检测到负相关，突出了右侧海马体在应激恢复力表型中的重要作用。我们的研究结果表明，应激易感和resilient亚组之间双侧dHi和vHi存在不同的纵向微观结构改变，并表明存在右侧侧化应激效应，这可能有助于应激相关障碍的诊断、预防及其干预。
