大鼠孕期尼古丁暴露致成年雌性子代抑郁症易感机制研究

Study on the Mechanism of Increased Susceptibility to Depression in Adult Female Rats Offspring Resulting from Prenatal Nicotine Exposure

目的:探讨大鼠孕期尼古丁暴露(PNE)致成年雌性子代抑郁症易感的宫内发生机制。方法:将受孕Wistar大鼠随机分为对照组和PNE组,PNE组大鼠于孕9~20 d皮下注射尼古丁2 mg/(kg·d),2次/日。部分子代大鼠于孕20 d取脑切片Neu N免疫荧光染色观察前额叶皮质和海马形态改变;部分大鼠正常出生喂养至3月龄,给予慢性不可预见性温和刺激(CUMS),检测刺激前后雌性子代大鼠行为学改变,实时定量PCR检测前额叶皮质和海马组织中与突触生长发育相关基因的表达。结果:与对照组相比,旷场试验中PNE组成年雌性子代大鼠CUMS后表现为总路程、总速率和直立次数明显减少(P<0.05),粪便粒数增加(P<0.05),强迫游泳实验中不动时间明显延长(P<0.01),表现出抑郁行为;PNE组孕20 d胎鼠前额叶皮质变薄,海马细胞层结构不清,轴突不连续;CUMS后PNE组成年子代前额叶皮质和海马,突触生长发育相关基因NR1、NR2A、NR2B、Syn I和Snap25 m RNA转录水平明显下降(P<0.01)。结论:PNE导致大鼠成年雌性子代应激后抑郁症易感性增加,可能与子代前额皮质和海马神经元和突触形成发育等基因转录水平降低,所致前额叶皮质和海马结构和功能改变有关。

Objective： To investigate the possible intrauterine mechanism of increased susceptibility of depression in adult female rats offspring resulting from prenatal nicotine exposure （PNE）. Methods： Pregnant Wistar rats were randomly divided into control and PNE groups. PNE rats were given nicotine （2 mg/kg·d） by subcutaneous injection from the 9th day to the 20th day of gestation. Brain sections were taken of some offspring rats on the 20th day of pregnancy, and NeuN staining was performed to observe morphological changes in the prefrontal cortex and hippocampus. The other offspring rats were raised to 3 months old and given chronic unpredictable mild stimulation （CUMS）. The behavioral changes of female offspring rats were observed before and after stimulation. Real-time quantitative PCR was used to detect expression of genes related to synapse formation in the prefrontal cortex and hippocampus. Results： Compared with the control group, the female rats in the PNE group showed significant decrease in total distance traveled and total rate after CUMS in the open-field test （P〈0.05）. The frequency of upright position decreased also （P〈0.05）. However, the quantity of feces was increased in the PNE group （P〈0.05）. In the forced swimming test, adult female offspring in the PNE group showed significantly longer immobility time than those in the control group （P〈0.01）, displaying depressive behavior. Fetal offspring in the PNE group showed thinner prefrontal cortex and unclear cell layers in the hippocampus with incomplete axons. The mRNA expression of NR1, NR2A, NR2B, Syn I, and Snap25 in the prefrontal cortex and hippocampus was significantly decreased after CUMS in adult offspring of the PNE group compared to those of the control group （P〈0.01）. Conclusion： Exposure to nicotine during pregnancy in rats leads to an increased susceptibility to depression in their adult female offspring, which may be related to decreased expression of genes involved in the development of neurons and synapses in the prefrontal cortex and hippocampus, resulting in changes in the structure and function of the prefrontal cortex and hippocampus.