Oesch Nicholas, Euler Thomas, Taylor W Rowland
Neurological Sciences Institute, Oregon Health and Sciences University, Beaverton, Oregon 97006, USA.
Neuron. 2005 Sep 1;47(5):739-50. doi: 10.1016/j.neuron.2005.06.036.
Dendritic spikes that propagate toward the soma are well documented, but their physiological role remains uncertain. Our in vitro patch-clamp recordings and two-photon calcium imaging show that direction-selective retinal ganglion cells (DSGCs) utilize orthograde dendritic spikes during physiological activity. DSGCs signal the direction of image motion. Excitatory subthreshold postsynaptic potentials are observed in DSGCs for motion in all directions and provide a weakly tuned directional signal. However, spikes are generated over only a narrow range of motion angles, indicating that spike generation greatly enhances directional tuning. Our results indicate that spikes are initiated at multiple sites within the dendritic arbors of DSGCs and that each dendritic spike initiates a somatic spike. We propose that dendritic spike failure, produced by local inhibitory inputs, might be a critical factor that enhances directional tuning of somatic spikes.
向胞体传播的树突棘波已有充分记录，但其生理作用仍不确定。我们的体外膜片钳记录和双光子钙成像表明，方向选择性视网膜神经节细胞（DSGCs）在生理活动期间利用顺行性树突棘波。DSGCs对图像运动方向进行信号编码。在DSGCs中观察到对所有方向运动的兴奋性阈下突触后电位，并提供一个弱调谐的方向信号。然而，动作电位仅在很窄的运动角度范围内产生，这表明动作电位的产生极大地增强了方向调谐。我们的结果表明，动作电位在DSGCs树突分支内的多个位点起始，并且每个树突棘波引发一个胞体动作电位。我们提出，由局部抑制性输入产生的树突棘波失败可能是增强胞体动作电位方向调谐的关键因素。
