Benhassine Narimane, Berger Thomas
Institute of Physiology, University of Bern, Switzerland.
Pflugers Arch. 2009 Mar;457(5):1133-45. doi: 10.1007/s00424-008-0569-3. Epub 2008 Sep 2.
Large-conductance calcium-dependent potassium channels (BK channels) are homogeneously distributed along the somatodendritic axis of layer 5 pyramidal neurons of the rat somatosensory cortex. The relevance of this conductance for dendritic calcium electrogenesis was studied in acute brain slices using somatodendritic patch clamp recordings and calcium imaging. BK channel activation reduces the occurrence of dendritic calcium spikes. This is reflected in an increased critical frequency of somatic spikes necessary to activate the distal initiation zone. Whilst BK channels repolarise the somatic spike, they dampen it only in the distal dendrite. Their activation reduces dendritic calcium influx via glutamate receptors. Furthermore, they prevent dendritic calcium electrogenesis and subsequent somatic burst discharges. However, the time window for coincident somatic action potential and dendritic input to elicit dendritic calcium events is not influenced by BK channels. Thus, BK channel activation in layer 5 pyramidal neurons affects cellular excitability primarily by establishing a high threshold at the distal action potential initiation zone.
大电导钙激活钾通道（BK通道）均匀分布于大鼠体感皮层第5层锥体神经元的胞体树突轴上。利用胞体树突膜片钳记录和钙成像技术，在急性脑片中研究了这种电导对树突钙电活动的影响。BK通道激活可减少树突钙峰电位的发生。这表现为激活远端起始区所需的体细胞峰电位临界频率增加。虽然BK通道使体细胞峰电位复极化，但它们仅在远端树突中减弱峰电位。它们的激活减少了通过谷氨酸受体的树突钙内流。此外，它们可防止树突钙电活动及随后的体细胞爆发性放电。然而，BK通道不影响引发树突钙事件的体细胞动作电位与树突输入同时发生的时间窗口。因此，第5层锥体神经元中BK通道的激活主要通过在远端动作电位起始区建立高阈值来影响细胞兴奋性。
