Calcium Dynamics, Buffering, and Buffer Saturation in the Boutons of Dentate Granule-Cell Axons in the Hilus
Calcium Dynamics, Buffering, and Buffer Saturation in the Boutons of Dentate Granule-Cell Axons in the Hilus
复制标题
门齿状颗粒细胞轴突的钙动力学、缓冲和缓冲饱和度
作者：
M. Jackson;S. Redman
齿状回颗粒细胞轴突在门部形成突触。利用共聚焦荧光成像研究了这些轴突钮扣中的Ca2+信号。通过贴片夹紧细胞体并允许染料扩散到轴突，将不同浓度的钙离子指示剂俄勒冈绿BAPTA-1装入钮扣。静息游离[Ca2+]从74 nm开始，在动作电位后立即上升到~ 1 μm，然后以43 msec的时间常数衰减到静息（所有外推到染料浓度为零）。动作电位诱导的[Ca2+]上升在较大钮扣中较小，与尺寸无关的Ca2+通道密度为45/μm2一致。动作电位诱导的[Ca2+]变化随染料浓度的变化而变化，其方式与κE ~ 20一致，内源性缓冲结合Ca2+与游离Ca2+的比例。在动作电位的序列中，[Ca2+]增量的超线性总和超过了染料饱和的预期。内源性Ca2+缓冲量随着[Ca2+]的增加而下降，这种饱和表明缓冲液的解离常数为~ 500 nm，浓度为~ 130 μm。这与钙结合蛋白d28k的解离常数相似，钙结合蛋白d28k是齿状颗粒细胞中丰富的Ca2+结合蛋白。因此，calbinin - d28k是这些实验揭示的Ca2+缓冲液的良好候选者。内源性缓冲液的饱和可以通过放大重复活动中[Ca2+]的变化而产生短期的促进作用。缓冲液饱和也可能与齿状颗粒细胞形成的突触的长时程增强的突触前诱导有关。
The axons of dentate gyrus granule cells form synapses in the hilus. Ca2+ signaling was investigated in the boutons of these axons using confocal fluorescence imaging. Boutons were loaded with various concentrations of the Ca2+indicator Oregon Green BAPTA-1 by patch-clamping the cell bodies and allowing the dye to diffuse into the axon. Resting free [Ca2+] started at 74 nm, rose to ∼1 μm immediately after an action potential, and then decayed to rest with a time constant of 43 msec (all extrapolated to a dye concentration of zero). Action potential-induced [Ca2+] rises were smaller in larger boutons, consistent with a size-independent Ca2+ channel density of 45/μm2. Action potential-induced [Ca2+] changes varied with dye concentration in a manner consistent with κE ∼20 for the ratio of endogenous buffer-bound Ca2+ to free Ca2+. During trains of action potentials, [Ca2+] increments summed supralinearly by more than that expected from dye saturation. The amount of endogenous Ca2+ buffering declined as [Ca2+] rose, and this saturation indicated a buffer with a dissociation constant of ∼500 nm and a concentration of ∼130 μm. This is similar to the dissociation constant of calbindin-D28K, a Ca2+-binding protein that is abundant in dentate granule cells. Thus, calbindin-D28K is a good candidate for the Ca2+ buffer revealed by these experiments. The saturation of endogenous buffer can generate short-term facilitation by amplifying [Ca2+] changes during repetitive activity. Buffer saturation may also be relevant to the presynaptic induction of long-term potentiation at synapses formed by dentate granule cells.
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DOI：
10.1073/pnas.170278697
发表时间：
2000-08-15
影响因子：
11.1
作者：
Cox, CL;Denk, W;Svoboda, K
通讯作者：
Svoboda, K
DOI：
10.1073/pnas.88.2.380
发表时间：
1991-01-01
影响因子：
11.1
作者：
JACKSON, MB;KONNERTH, A;AUGUSTINE, GJ
通讯作者：
AUGUSTINE, GJ
大鼠海马单个苔藓纤维突触前末端的钙信号传导。
影响因子：
2.5
作者：
Liang,Yong;Yuan,Li-Lian;Johnston,Daniel;Gray,Richard
通讯作者：
Gray,Richard
大鼠海马切片齿状棘肺门细胞记录的自发和诱发 EPSP 的特征。
影响因子：
2.5
作者：
Scharfman,HE
通讯作者：
Scharfman,HE
通过电喷雾电离质谱法测定大鼠脑钙结合蛋白 D28K 中的钙结合位点。
DOI：
10.1021/bi9628329
发表时间：
1997
期刊：
Biochemistry.
影响因子：
--
作者：
Veenstra,TD;Johnson,KL;Tomlinson,AJ;Naylor,S;Kumar,R
通讯作者：
Kumar,R