Institut National de la Santé et de la Recherche Médicale UMR1072, Marseille 13015, France.
J Neurosci. 2012 Feb 8;32(6):2166-81. doi: 10.1523/JNEUROSCI.5297-11.2012.
The level of expression of ion channels has been demonstrated to vary over a threefold to fourfold range from neuron to neuron, although the expression of distinct channels may be strongly correlated in the same neurons. We demonstrate that variability and covariation also apply to the biophysical properties of ion channels. We show that, in rat substantia nigra pars compacta dopaminergic neurons, the voltage dependences of the A-type (I(A)) and H-type (I(H)) currents exhibit a high degree of cell-to-cell variability, although they are strongly correlated in these cells. Our data also demonstrate that this cell-to-cell covariability of voltage dependences is sensitive to cytosolic cAMP and calcium levels. Finally, using dynamic clamp, we demonstrate that covarying I(A) and I(H) voltage dependences increases the dynamic range of rebound firing while covarying their amplitudes has a homeostatic effect on rebound firing. We propose that the covariation of voltage dependences of ion channels represents a flexible and energy-efficient way of tuning firing in neurons.
离子通道的表达水平已被证明在神经元之间存在三到四倍的变化，尽管在相同的神经元中，不同通道的表达可能具有很强的相关性。我们证明这种可变性和共变性也适用于离子通道的生物物理特性。我们表明，在大鼠黑质致密部多巴胺能神经元中，A型（I(A)）和 H 型（I(H)）电流的电压依赖性表现出高度的细胞间变异性，尽管它们在这些细胞中具有很强的相关性。我们的数据还表明，这种电压依赖性的细胞间共变对细胞浆 cAMP 和钙水平敏感。最后，使用动态钳位，我们证明了共变 I(A)和 I(H)电压依赖性会增加反弹发射的动态范围，而共变它们的幅度对反弹发射具有同型作用。我们提出，离子通道的电压依赖性共变代表了一种灵活且节能的神经元发射调节方式。
