Xiong Jiaxiang, He Chao, Li Chao, Tan Gang, Li Jingcheng, Yu Zhengping, Hu Zhian, Chen Fang
Department of Physiology, Third Military Medical University, Chongqing, PR China.
Department of Occupational Health, Third Military Medical University, Chongqing, PR China.
PLoS One. 2013 Dec 20;8(12):e83561. doi: 10.1371/journal.pone.0083561. eCollection 2013.
In the present study, we investigated the effects of chronic exposure (14 and 28 days) to a 0.5 mT 50 Hz extremely low-frequency magnetic field (ELM) on the dendritic spine density and shape in the superficial layers of the medial entorhinal cortex (MEC). We performed Golgi staining to reveal the dendritic spines of the principal neurons in rats. The results showed that ELM exposure induced a decrease in the spine density in the dendrites of stellate neurons and the basal dendrites of pyramidal neurons at both 14 days and 28 days, which was largely due to the loss of the thin and branched spines. The alteration in the density of mushroom and stubby spines post ELM exposure was cell-type specific. For the stellate neurons, ELM exposure slightly increased the density of stubby spines at 28 days, while it did not affect the density of mushroom spines at the same time. In the basal dendrites of pyramidal neurons, we observed a significant decrease in the mushroom spine density only at the later time point post ELM exposure, while the stubby spine density was reduced at 14 days and partially restored at 28 days post ELM exposure. ELM exposure-induced reduction in the spine density in the apical dendrites of pyramidal neurons was only observed at 28 days, reflecting the distinct vulnerability of spines in the apical and basal dendrites. Considering the changes in spine number and shape are involved in synaptic plasticity and the MEC is a part of neural network that is closely related to learning and memory, these findings may be helpful for explaining the ELM exposure-induced impairment in cognitive functions.
在本研究中，我们调查了慢性暴露（14天和28天）于0.5 mT 50 Hz极低频磁场（ELM）对内侧内嗅皮质（MEC）浅层树突棘密度和形态的影响。我们进行了高尔基染色以揭示大鼠主要神经元的树突棘。结果表明，暴露于ELM在14天和28天时均导致星状神经元树突以及锥体神经元基底树突中的棘密度降低，这主要是由于细而分支的棘丢失所致。ELM暴露后蘑菇状棘和短粗状棘密度的改变具有细胞类型特异性。对于星状神经元，ELM暴露在28天时略微增加了短粗状棘的密度，而同时并未影响蘑菇状棘的密度。在锥体神经元的基底树突中，我们仅在ELM暴露后的较晚时间点观察到蘑菇状棘密度显著降低，而短粗状棘密度在ELM暴露后14天时降低，并在28天时部分恢复。仅在28天时观察到ELM暴露诱导锥体神经元顶树突中的棘密度降低，这反映了顶树突和基底树突中棘的不同易损性。考虑到棘数量和形态的变化与突触可塑性有关，且MEC是与学习和记忆密切相关的神经网络的一部分，这些发现可能有助于解释ELM暴露引起的认知功能损害。
