CALCIUM SPIKES IN TOAD RODS
CALCIUM SPIKES IN TOAD RODS
复制标题
DOI：
10.1113/jphysiol.1980.sp013300
复制
发表时间：
1980-01-01
影响因子：
5.5
通讯作者：
QUANDT, FN
中科院分区：
文献类型：
--
作者：
FAIN, GL;GERSCHENFELD, HM;QUANDT, FN
当用6-12 mM的四乙基氯化铵(TEA)灌流蟾蜍的视网膜时，视杆细胞内的记录显示出巨大的去极化再生潜力。对于短暂的茶暴露，这些电位发生在光反应的恢复阶段；在较长时间的暴露中，它们在黑暗中自发，但在光照下被抑制。在3-10 mM的4-氨基吡啶和1-2 mM的BaCl2灌流过程中观察到相似的再生潜力。再生电位的幅度依赖于细胞外钙浓度([Ca~(2+)]_0)。降低[Ca~(2+)]_0使它们的波幅降低，当[Ca~(2+)]_0为0时，它们可逆地被取消。[Ca~(2+)]_0每增加1.5~2倍，膜电位超极化较小，再生反应幅度较大。较大的[Ca~(2+)]_0升高会产生较大的膜超极化，并可逆地抑制再生反应。茶叶中高浓度的Sr2+也提高了再生活性，但不影响杆状休眠膜电位。再生电位的幅度随[Sr2+]0的增加而持续增加，在28 mM的Sr2+中，即使在无细胞外Na+的情况下，再生杆也产生60-70 mV的动作电位。25微米Cd~(2+)、50~100微米Co2+、5微米镁离子和100微米D-600[甲氧维拉帕米]可阻断再生潜能。他们不受2µm TTX或2-5 mM天冬氨酸钠盐的影响。在含有12 mm TEA的Ringer中，在内向电流脉冲终止时，可以从棒上记录到大的阳极断开响应。这些阳极断裂反应也被Co2+抑制，而不受TTX或天冬氨酸钠的影响。蟾蜍杆的膜可能含有一种通常对钙离子有选择性的电导，这种电导可被去极化激活。在正常的林格中，通过这个电导的内向电流产生的影响很小，因为它被很大的外向电流平衡，可能是由K+携带的。TEA和其他试剂似乎阻止了这种外向电流，允许钙电流变得再生。
When the retina of the toad, B. marinus, was superfused with 6-12 mM tetraethylammonium chloride (TEA), intracellular recordings from rods showed large, depolarizing regenerative potentials. For brief exposures to TEA, these potentials occurred during the recovery phase of the light responses; during longer exposures, they were spontaneous in darkness but suppressed during illumination. Similar regenerative potentials were observed during perfusion with 3-10 mM 4-aminopyridine and 1-2 mM BaCl2. The amplitude of the regenerative potentials depended on the extracellular Ca concentration ([Ca2+]0). Lowering [Ca2+]0 decreased their amplitude and in zero [Ca2+]0 they were reversibly abolished. Increasing [Ca2+]0 by 1.5-2 times produced a small hyperpolarization of membrane potential and a large augmentation in regenerative response amplitude. Larger increases in [Ca2+]0 produced large membrane hyperpolarizations and reversibly suppressed the regenerative responses. High concentrations of Sr2+ in TEA also enhanced regenerative activity but did not affect the rod resting membrane potential. The amplitude of regenerative potentials increased continuously with increasing [Sr2+]0, and in 28 mM Sr2+ the rods generated 60-70 mV action potentials, even in the absence of extracellular Na+. The regenerative potentials were blocked by 25 .mu.M Cd2+, 50-100 .mu.M Co2+, 5 mM Mg2+ and 100 .mu.M D-600 [methoxyverapamil]. They were unaffected by 2 .mu.M TTX or 2-5 mM Na aspartate. In Ringer containing 12 mM TEA, large anode break responses could be recorded from rods at the termination of inward current pulses. These anode break responses were also suppressed by Co2+ and unaffected by TTX or Na aspartate. The membrane of toad rods may contain a conductance normally selective for Ca2+, which is activated by depolarization. In normal Ringer, the inward current through this conductance produces little effect, since it is balanced by a large outward current, probably carried by K+. TEA and other agents appear to block this outward current, permitting the Ca2+ current to become regenerative.