Davie Jenny T, Clark Beverley A, Häusser Michael
Department of Neuroscience, Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.
J Neurosci. 2008 Jul 23;28(30):7599-609. doi: 10.1523/JNEUROSCI.0559-08.2008.
Activation of the climbing fiber input powerfully excites cerebellar Purkinje cells via hundreds of widespread dendritic synapses, triggering dendritic spikes as well as a characteristic high-frequency burst of somatic spikes known as the complex spike. To investigate the relationship between dendritic spikes and the spikelets within the somatic complex spike, and to evaluate the importance of the dendritic distribution of climbing fiber synapses, we made simultaneous somatic and dendritic patch-clamp recordings from Purkinje cells in cerebellar slices. Injection of large climbing fiber-like synaptic conductances at the soma using dynamic clamp was sufficient to reproduce the complex spike, independently of dendritic spikes, indicating that neither a dendritic synaptic distribution nor dendritic spikes are required. Furthermore, we found that dendritic spikes are not directly linked to spikelets in the complex spike, and that each dendritic spike is associated with only 0.24 +/- 0.09 extra somatic spikelets. Rather, we demonstrate that dendritic spikes regulate the pause in firing that follows the complex spike. Finally, using dual somatic and axonal recording, we show that all spikelets in the complex spike are axonally generated. Thus, complex spike generation proceeds relatively independently of dendritic spikes, reflecting the dual functional role of climbing fiber input: triggering plasticity at dendritic synapses and generating a distinct output signal in the axon. The encoding of dendritic spiking by the post-complex spike pause provides a novel computational function for dendritic spikes, which could serve to link these two roles at the level of the target neurons in the deep cerebellar nuclei.
攀缘纤维输入的激活通过数百个广泛分布的树突突触强烈地兴奋小脑浦肯野细胞，触发树突棘以及一种称为复合峰电位的特征性高频体峰电位爆发。为了研究树突棘与体复合峰电位内的小峰电位之间的关系，并评估攀缘纤维突触树突分布的重要性，我们从小脑切片中的浦肯野细胞进行了同步的体细胞和树突膜片钳记录。使用动态钳在体细胞处注入大的攀缘纤维样突触电导足以重现复合峰电位，而与树突棘无关，这表明既不需要树突突触分布也不需要树突棘。此外，我们发现树突棘与复合峰电位中的小峰电位没有直接联系，并且每个树突棘仅与0.24±0.09个额外的体小峰电位相关。相反，我们证明树突棘调节复合峰电位之后的放电暂停。最后，使用体细胞和轴突双记录，我们表明复合峰电位中的所有小峰电位都是轴突产生的。因此，复合峰电位的产生相对独立于树突棘，反映了攀缘纤维输入的双重功能作用：触发树突突触处的可塑性并在轴突中产生独特的输出信号。复合峰电位后暂停对树突棘放电的编码为树突棘提供了一种新的计算功能，这可能有助于在小脑深部核团的靶神经元水平上连接这两种作用。
