Staubli U V, Ji Z X
Center for Neural Science, New York University, New York, NY 10003, USA.
Brain Res. 1996 Apr 1;714(1-2):169-76. doi: 10.1016/0006-8993(95)01523-x.
The induction of long-term depression (LTD) was investigated in area CA1 of hippocampal slices from adult rats. To produce LTD, prolonged low-frequency stimulation (LFS, 900 stimuli at 1 Hz) was delivered to one of two independent Schaffer-collateral/commissural projections, while the second input served as a control to monitor heterosynaptic effects. The depression was calculated as percent decrease in the slope of the dendritic field EPSP relative to baseline values, and LTD was considered established if the response decrement was at least 15% in magnitude and stable for 30-60 min. By delivering LFS in conditions of different relative baseline response magnitudes, it was revealed that the intensity of afferent low-frequency activity has a significant impact on the induction frequency, magnitude and input-specificity of the depression: the rate of LTD occurrence and the effect of LFS on the absolute response decrement increased successively as the stimulation strength was raised, but the impact of LFS on the relative LTD magnitude decreased at higher stimulation intensities; the depression was specific to the stimulated input (homosynaptic LTD) when baseline responses were spike-free, but spread to the pathway which was silent during LFS (heterosynaptic LTD) in experiments conducted above spiking threshold. The results indicate that in the adult rat (i) the induction of input-specific LTD is dependent on the level of synaptic activation during LFS, and (ii) LTD can easily be obtained in strongly stimulated pathways but may be the result of a generalized decrease in the postsynaptic response.
研究了成年大鼠海马切片CA1区中长时程抑制（LTD）的诱导情况。为了产生LTD，对两个独立的Schaffer侧支/联合投射之一施加长时间低频刺激（LFS，1 Hz，900次刺激），而第二个输入作为对照以监测异突触效应。抑制程度以树突野兴奋性突触后电位（EPSP）斜率相对于基线值的下降百分比来计算，如果反应下降幅度至少为15%且在30 - 60分钟内稳定，则认为LTD已建立。通过在不同相对基线反应幅度条件下施加LFS发现，传入低频活动的强度对抑制的诱导频率、幅度和输入特异性有显著影响：随着刺激强度的增加，LTD发生的速率以及LFS对绝对反应下降的影响依次增加，但在较高刺激强度下LFS对相对LTD幅度的影响减小；当基线反应无锋电位时，抑制对受刺激的输入具有特异性（同突触LTD），但在高于锋电位阈值的实验中，抑制会扩散到LFS期间沉默的通路（异突触LTD）。结果表明，在成年大鼠中，（i）输入特异性LTD的诱导取决于LFS期间的突触激活水平，（ii）在强烈刺激的通路中很容易获得LTD，但这可能是突触后反应普遍降低的结果。
