Spatiotemporally graded NMDA spike/plateau potentials in basal dendrites of neocortical pyramidal neurons
Spatiotemporally graded NMDA spike/plateau potentials in basal dendrites of neocortical pyramidal neurons
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DOI：
10.1152/jn.00011.2008
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发表时间：
2008-05-01
影响因子：
2.5
通讯作者：
Tank, David W.
中科院分区：
文献类型：
--
作者：
Major, Guy;Polsky, Alon;Tank, David W.
谷氨酸能输入聚集在20-40 μ m范围内，可以在皮质锥体神经元的末端树突中引发局部n-甲基- d -天冬氨酸（NMDA）峰值/平台电位，激发了单个末端树突可以作为决策计算亚基的概念。一个典型的顶基树突大约有100-200 μ m长，它是否可以作为多个决策亚基？我们通过对大鼠体感觉皮质脑切片第5层锥体神经元末端基底树突的多个部位进行连续的局部刺激来验证这一点，使用离子电泳或释放短暂的谷氨酸脉冲。在体细胞测量的平均峰值/平台振幅的空间梯度约为7倍，从远端输入类似于3 mV到近端输入类似于23 mV。峰值/高原在所有位置均以NMDA受体（NMDAR）电导为主。大的Ca2+瞬态伴随着峰值/高原在输入点周围类似的10- 40亩区域；较小的Ca2+瞬态几乎均匀地延伸到枝晶尖端。峰值/平台持续时间随着谷氨酸和去极化的增加而增加；高Ca2+区大小随峰值/平台持续时间的增加而增加。最小高Ca2+区半宽度（刚好高于NMDA峰值阈值）从远端（类似于10 μ m）增加到近端位置（类似于25 μ m）， NMDA峰值谷氨酸阈值也是如此。去极化降低了谷氨酸阈值。基于此的多位点交互模拟表明，如果在体内发生适当的定时和局部输入，单个基底树突可以对应多个合作动态决策亚单位的级联，这些亚单位能够保留数百毫秒的信息，并从远端到近端增加对神经输出的影响。因此，树突NMDA峰值/高原非常适合支持分级持续放电。
Glutamatergic inputs clustered over similar to 20-40 mu m can elicit local N-methyl-D-aspartate (NMDA) spike/plateau potentials in terminal dendrites of cortical pyramidal neurons, inspiring the notion that a single terminal dendrite can function as a decision-making computational subunit. A typical terminal basal dendrite is similar to 100-200 mu m long: could it function as multiple decision-making subunits? We test this by sequential focal stimulation of multiple sites along terminal basal dendrites of layer 5 pyramidal neurons in rat somatosensory cortical brain slices, using iontophoresis or uncaging of brief glutamate pulses. There was an approximately sevenfold spatial gradient in average spike/plateau amplitude measured at the soma, from similar to 3 mV for distal inputs to similar to 23 mV for proximal inputs. Spike/plateaus were NMDA receptor (NMDAR) conductance-dominated at all locations. Large Ca2+ transients accompanied spike/plateaus over a similar to 10- to 40-mu m zone around the input site; smaller Ca2+ transients extended approximately uniformly to the dendritic tip. Spike/plateau duration grew with increasing glutamate and depolarization; high Ca2+ zone size grew with spike/plateau duration. The minimum high Ca2+ zone half-width (just above NMDA spike threshold) increased from distal (similar to 10 mu m) to proximal locations (similar to 25 mu m), as did the NMDA spike glutamate threshold. Depolarization reduced glutamate thresholds. Simulations exploring multi-site interactions based on this demonstrate that if appropriately timed and localized inputs occur in vivo, a single basal dendrite could correspond to a cascade of multiple co-operating dynamic decision-making subunits able to retain information for hundreds of milliseconds, with increasing influence on neural output from distal to proximal. Dendritic NMDA spike/plateaus are thus well-suited to support graded persistent firing.