Department of Integrative Neurophysiology, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Vrije Universiteit Amsterdam Amsterdam, Netherlands.
Front Cell Neurosci. 2013 Jun 26;7:99. doi: 10.3389/fncel.2013.00099. eCollection 2013.
Cortical pyramidal neurons show irregular in vivo action potential (AP) spiking with high-frequency bursts occurring on sparse background activity. Somatic APs can backpropagate from soma into basal and apical dendrites and locally generate dendritic calcium spikes. The critical AP frequency for generation of such dendritic calcium spikes can be very different depending on cell type or brain area involved. Previously, it was shown in vitro that calcium electrogenesis can be induced in L(ayer) 5 pyramidal neurons of prefrontal cortex (PFC). It remains an open question whether somatic burst spiking and the resulting dendritic calcium electrogenesis also occur in morphologically more compact L2/3 pyramidal neurons. Furthermore, it is not known whether critical frequencies that trigger dendritic calcium electrogenesis occur in PFC under awake conditions in vivo. Here, we addressed these issues and found that pyramidal neurons in both PFC L2/3 and L5 in awake rats spike APs in short bursts but with different probabilities. The critical frequency (CF) for calcium electrogenesis in vitro was layer-specific and lower in L5 neurons compared to L2/3. Taking the in vitro CF as a predictive measure for dendritic electrogenesis during in vivo spontaneous activity, supracritical bursts in vivo were observed in a larger fraction of L5 neurons compared to L2/3 neurons but with similar incidence within these subpopulations. Together, these results show that in PFC of awake rats, AP spiking occurs at frequencies that are relevant for dendritic calcium electrogenesis and suggest that in awake rat PFC, dendritic calcium electrogenesis may be involved in neuronal computation.
皮质锥体细胞在体内表现出不规则的动作电位 (AP) 爆发，稀疏的背景活动中会发生高频爆发。胞体 AP 可以从胞体逆行传播到基底和顶树突，并在局部产生树突钙峰。产生这种树突钙峰的临界 AP 频率可能因细胞类型或涉及的脑区而异。以前在体外已经证明，前额叶皮层 (PFC) 的 L(ayer) 5 锥体神经元可以诱导钙电发生。胞体爆发式放电和由此产生的树突钙电发生是否也发生在形态上更紧凑的 L2/3 锥体神经元中，这仍然是一个悬而未决的问题。此外，在清醒状态下，体内 PFC 是否会发生引发树突钙电发生的临界频率，这也尚未可知。在这里，我们解决了这些问题，发现清醒大鼠的 PFC L2/3 和 L5 中的锥体神经元都以短爆发的形式爆发 AP，但概率不同。体外钙电发生的临界频率 (CF) 具有层特异性，且 L5 神经元的 CF 比 L2/3 神经元低。将体外 CF 作为体内自发活动期间树突电发生的预测指标，与 L2/3 神经元相比，在更大比例的 L5 神经元中观察到超临界爆发，但在这些亚群内，其发生率相似。总之，这些结果表明，在清醒大鼠的 PFC 中，AP 爆发发生在与树突钙电发生相关的频率范围内，并且表明在清醒大鼠的 PFC 中，树突钙电发生可能参与神经元计算。
