Froemke Robert C, Tsay Ishan A, Raad Mohamad, Long John D, Dan Yang
Division of Neurobiology, Department of Molecular and Cell Biology, University of California, Berkeley, USA.
J Neurophysiol. 2006 Mar;95(3):1620-9. doi: 10.1152/jn.00910.2005. Epub 2005 Nov 30.
Long-term synaptic modification depends on the relative timing of individual pre- and postsynaptic spikes, but the rules governing the effects of multispike bursts remain to be fully understood. In particular, some studies suggest that the spike timing dependence of synaptic modification breaks down with high-frequency bursts. In this study, we characterized the effects of pre- and postsynaptic bursts on long-term modification of layer 2/3 synapses in visual cortical slices from young rats. We found that, while pairing-induced synaptic modification depends on the burst frequency, this dependence can be explained in terms of the timing of individual pre- and postsynaptic spikes. Later spikes in each burst are less effective in synaptic modification, but spike efficacy is regulated differently in pre- and postsynaptic bursts. Presynaptically, spike efficacy is progressively weakened, in parallel with short-term synaptic depression. Postsynaptically, spike efficacy is suppressed to a lesser extent, and it depends on postsynaptic potassium channel activation. Such timing-dependent interaction among multiple spikes can account for synaptic modifications induced by a variety of spike trains, including the frequency-dependent transition from depression to potentiation induced by a postsynaptic burst preceding a presynaptic burst.
长期的突触修饰取决于单个突触前和突触后尖峰的相对时间，但多尖峰脉冲效应的控制规则仍有待充分理解。特别是，一些研究表明，高频脉冲会破坏突触修饰的尖峰时间依赖性。在本研究中，我们表征了突触前和突触后脉冲对幼鼠视觉皮层切片中第2/3层突触长期修饰的影响。我们发现，虽然配对诱导的突触修饰取决于脉冲频率，但这种依赖性可以根据单个突触前和突触后尖峰的时间来解释。每个脉冲中较晚出现的尖峰在突触修饰中的作用较小，但突触前和突触后脉冲中尖峰的功效调节方式不同。在突触前，尖峰功效与短期突触抑制平行逐渐减弱。在突触后，尖峰功效受到的抑制较小，并且它取决于突触后钾通道的激活。多个尖峰之间这种时间依赖性相互作用可以解释由各种尖峰序列诱导的突触修饰，包括突触后脉冲先于突触前脉冲时由抑制到增强的频率依赖性转变。
