慢性电刺激海马结构诱发大鼠脑磁共振成像异常信号分析

为探讨海马结构(hippocampal formation)功能失衡与癫痫源性脑损伤的关系，本工作采用 慢性强直电刺激大鼠海马(hippocampus, HPC) CA1顶树突区（apical dendrite region, A DR）或齿状回（dentate gyrus, DG）诱发大鼠癫痫模型，一天一次，连续刺激6～8天后， 观察人工致痫灶以外的横向弛豫时间加权的核磁共振(T₂ weighted magnetic reson ance im age, T₂-WI) 绝对信号值变化（片厚1mm），以及深部电图和原发性湿狗颤抖（pri mary wet dog shakes, WEDS），并对被检测动物T₂-WI信号异常的相应脑区进行组织学鉴定. 结果表明：（1）电 刺激大 鼠ADR或DG的作用基本相似，引起深部电图的癫痫样电活动和侧脑室区域T₂值增强.（2）含有电极尖端痕迹的核磁共振（magnetic resonance image,MRI）脑切片出现对称性腹部侧脑室区域T₂值增强，连续向后1mm取MRI脑切片进行观察发现，对侧腹部侧脑室区域信号异常. （3）组织学切片观察到：MRI检测的侧脑室区域T₂-WI信号增强与组织切片的侧脑室扩大相吻合，可见扩大的侧脑室中脉络丛上皮细胞病理性增生现象. 提示：在大鼠癫痫点燃现象出现之前，过度激活DG或ADR均可引起相似的早期癫痫源性脑损伤.

ABNORMAL T2-WI SIGNAL IN CHRONIC EPILEPTIC RATS INDUCED BY DELIVERING REPETITIVE TETANUSINTO THE APICAL DENDRITE REGION IN EITHER CA1 OR DENTATE GYRUS

The chronic rat temporal epilepsy was induced by repetitive tetanus (60Hz, 0.4～0.6mA , 2s) to the apical dendrite region (ADR) in either CA1 or the dentate gyrus ( DG ) once a day for 6 or 8 days. T₂-weighted MRI (T₂-WI) measurements and morpholog ical observations were performed on the tetanized rats. A resemble increase of MRI signal intensity in the lateral ventricle area was observed both in the ADR- tetanized rats and the DG-tetanized rats. There is an asymmetric T₂-WI ab normaliti es in the anterior MRI slices and ventral T₂-WI abnormalities contralater al to t he implantation side in the posterior MRI slices (1 mm posterior to the anterior MRI slice). Morphological identification showed that there are the enlarged lat e ral ventricle and pathological ventricular chorodea plexus hyperplasia which cor respond to the MRI observations. The results suggested that the activation of DGor ADR in an intrinsic hippocampal circuit may play the same role in epileptogenesis.