强直刺激的脉冲串间隔在LTP诱导中的重要作用

目的　比较不同参数的强直刺激在海马CA1区长时程增强(LTP)形成中的作用,探讨诱导海马CA1区LTP的适宜强直刺激。方法　采用不同参数的强直刺激在海马脑片的 CA1 区诱导 LTP。在 Schaffer侧枝上给予强直刺激后,记录CA1区锥体细胞的细胞外场电位(fEPSPs),分析不同参数诱导的 fEPSPs。我们使用4种串长和间隔不同而频率均为100 Hz的强直刺激:参数1为60个脉冲的短串刺激,3串为1组,串间隔200 ms,共5组,组间隔逐渐延长;参数2为300个脉冲总数的长串刺激,串间隔为 2 s;参数 3 为 60 个脉冲总数的短串刺激,串间隔为 2 s;参数 4 为60个脉冲的单串刺激。结果　参数1诱导的LTP的幅度及发生率均较其他3个参数的高;参数1和参数3可诱导出持续时间超过3 h的长持续 LTP(long lasting LTP, LL- LTP)。结论　串间隔为 200 ms(串频率相当于θ波)的高频强直刺激是海马CA1区诱导LTP的较好参数;100 Hz的短串刺激可以诱导海马CA1区的LL- LTP。

Significance of inter-burst interval in the induction of long-term potentiation

Objective To compare the different effects of different titanic parameters on the expression of long-term potentiation (LTP) and to determine the optimal patterns of tetanizing stimulation in hippocampal CA1 area in adult male rats. Methods Four tetanic parameters of 100Hz were used in the experiment. Tetanus 1 was a short burst of stimulus composed of 60 pulses, which were divided into 5 sets, each set including 4-pulses-bursts. The inter-burst intervals are lengthened gradually, 1s, 5s, 30s, 10min in sequence. Tetanus 2 was a long burst of stimulus composed of 300 pulses in all, each burst including 20 pulses. The inter-burst interval is 2s, and tetanus 3 is also a short burst of stimulus composed of 15 bursts, each burst including 4 pulses. The inter-burst interval is 2s and tetanus 4 is a single train of burst composed of 60 pulses. The field excitatory post-synaptic potentials (fEPSPs) in hippocampal CA1 area were evoked by stimulating the Schaffer collateral fibers in the stratum radiatum and the expressions of LTP induced by the four parameters were evaluated. Results The amplitude and incidence of LTP induced by tetanus 1 were higher than those induced by the other three parameters. There was no statistical significance between the responses induced by the other three parameters. Both tetanus 1 and tetanus 3 could lead to long-lasting-LTP (LL-LTP, over 3h). Conclusion A high frequency stimulus with 200ms-inter-burst interval (theta frequency) is better in the induction of LTP in hippocampal CA1 area. A short burst of stimulus with 100Hz can evoke the expression of LL-LTP in hippocampal CA1 area.