Womack Mary D, Khodakhah Kamran
Department of Physiology and Biophysics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
J Neurosci. 2003 Apr 1;23(7):2600-7. doi: 10.1523/JNEUROSCI.23-07-02600.2003.
Cerebellar Purkinje neurons provide the sole output of the cerebellar cortex and play a crucial role in motor coordination and maintenance of balance. They are spontaneously active, and it is thought that they encode timing signals in the rate and pattern of their activity. An understanding of factors that control their excitability is important for delineating their computational role in the cerebellum. We evaluated the role of small-conductance calcium-activated potassium (SK) channels in the regulation of activity of mouse and rat Purkinje neurons. We find that somatic SK channels effectively limit the maximum firing rate of Purkinje neurons; when SK channels are blocked by the specific antagonists apamin or scyllatoxin, cells fire spontaneously at rates as high as 500 spikes per second. Dendritic SK channels, however, control primarily the extent to which dendrites contribute to the firing rate of Purkinje cells. Given their presence in the dendrites, it is likely that SK channels in the proximal dendrites govern the efficacy of dendrosomatic electrical coupling. When studied under physiological conditions, it is found that SK channels play the same role in controlling the excitability of adult Purkinje neurons as they do in young cells.
小脑浦肯野神经元是小脑皮质的唯一输出神经元，在运动协调和平衡维持中起着关键作用。它们具有自发活动，并且人们认为它们在其活动的速率和模式中编码时间信号。了解控制其兴奋性的因素对于阐明它们在小脑中的计算作用很重要。我们评估了小电导钙激活钾（SK）通道在调节小鼠和大鼠浦肯野神经元活动中的作用。我们发现，体细胞SK通道有效地限制了浦肯野神经元的最大放电率；当SK通道被特异性拮抗剂蜂毒明肽或刺尾鱼毒素阻断时，细胞会以高达每秒500次的速率自发放电。然而，树突状SK通道主要控制树突对浦肯野细胞放电率的贡献程度。鉴于它们存在于树突中，近端树突中的SK通道可能控制树突体电耦合的效率。在生理条件下进行研究时，发现SK通道在控制成年浦肯野神经元兴奋性方面与在年轻细胞中发挥着相同的作用。
