中文摘要：

标准低频率连续刺激（1～2 Hz,15 min）能够诱导幼年大鼠（＜4周）海马CA1区同突触长时程压抑（long-term depression,LTD）,而只有较高频率且持续时间较长的连续刺激才能诱导出成年动物该部位稳定的LTD.本研究采用成年大鼠海马脑片标本,电刺激Schaffer侧枝传入纤维,在CA1区锥体细胞层记录群体锋电位,选用两种新的刺激参数以观测不同刺激型式在诱导成年大鼠LTD中的作用.诱导LTD的刺激参数为：（1）2 Hz,5串,串长60 s,串间隔60 s;（2）5 Hz,5串,串长24 s,串间隔96 s;（3）对照组参数：2 Hz,300 s.结果显示,对照参数未能诱导出LTD;而两种频率不同但脉冲总数与刺激总时程相同的多串刺激,即参数（1）与参数（2）,均在成年大鼠海马CA1区诱导产生了LTD.两种参数所诱导的LTD特征具有参数特异性,该特征主要表现为LTD诱导潜伏期和LTD的幅度：参数（1）、（2）诱导的LTD的潜伏期分别为15～25 min和30～40 min;强直刺激后80 min时LTD的幅度分别为（57.5±2.8）%和（67.7±3.4）%.以上结果表明：特定型式的低频率刺激能够诱导成年大鼠海马CA1区的LTD,提示LTD的诱导与刺激的组合型式相关,并且2 Hz较5 Hz的多串刺激在诱导LTD中更为有效.

英文摘要：

Previous reports suggested that a low-frequency stimulus （LFS） of 1-2 Hz （600,-900 pulses） induced a homosynaptic longterm depression （LTD） of synaptic efficacy in the hippocampal CAI area of young rats （〈 4-week old）. However, these stimulation protocols often failed to induce LTD in the adult CA 1 hippocampus. In the present study, we examined the effects of two novel tetanus patterns on LTD induction in adult rat hippocampal slices. We determined that these novel stimulation protocols induced LTD in the adult hippocampus, and that the characteristics of induced LTD were parameter-specific, including latency （period from the end of tetanus to a beginning of LTD） and the amplitude of LTD. These results suggest that LFS with certain patterns can induce LTD in the CAI area of adult rat hippocampal slices, and that the multi-trains of 2-Hz protocol provided more effective response than the 5-Hz protocol.