Cyclic AMP regulates an inward rectifying sodium‐potassium current in dissociated bull‐frog sympathetic neurones.
Cyclic AMP regulates an inward rectifying sodium‐potassium current in dissociated bull‐frog sympathetic neurones.
复制标题
DOI：
10.1113/jphysiol.1990.sp017920
复制
发表时间：
1990
期刊：
影响因子：
--
通讯作者：
T. Tokimasa;T. Akasu
中科院分区：
文献类型：
--
作者：
T. Tokimasa;T. Akasu
1.原代培养的牛蛙交感神经元在全细胞配置中被电压钳位。移液管溶液含有ATP（5 mM）。2.在含有钴（2 mM）、镁（4 mM）、钡（2 mM）、四乙基铵（20 mM）、河豚毒素（3 μ M）、蜂毒肽（30 nM）和4-氨基吡啶（1 mM）的标称无钙溶液中，将超极化激活的钠钾电流（H电流：IH）与其他膜电流分离。IH被铯（10 - 300 μ M）选择性阻断。3. IH的稳态激活发生在-60 mV和-130 mV之间。在-90 mV的半激活电压下，H电导为4.1 - 6.6 nS。当灌流液中钾离子和钠离子的浓度分别为20和70 mM时，IH的逆转电位约为-20 mV。IH在-90 mV和22 ℃下以2.8 s的时间常数激活。16 - 26 ℃的Q10为4.3。4.移液器溶液中的不可水解ATP类似物不支持IH激活。GTP-γ-S（30 - 500 μ M）的细胞内“负载”导致IH的进行性激活。5.毛喉素（10 μ M）增加了70%的IH的最大电导。这与半激活电压（5 - 10 mV）和IH激活/失活时间常数的电压依赖性的去极化偏移有关。6.通过细胞内“加载"环AMP（3 - 10 μ M）或浴涂8-溴环AMP（0.1 - 1 mM）、二丁酰环AMP（1 mM）和3-异丁基-1-甲基黄嘌呤（0.1 - 1 mM），获得了与毛喉素基本相同的结果。7.蛋白激酶抑制剂H-8（1 - 10 μ M）降低了IH的峰值幅度。佛波醇12-肉豆蔻酸酯13-乙酸酯（10 μ M），一种蛋白激酶C激活剂，没有效果。8.可以得出结论，电压依赖性阳离子电流可以通过腺苷酸环化酶的基础活性来调节，推测是通过蛋白激酶A，在脊椎动物交感神经元中。
1. Bull‐frog sympathetic neurones in primary culture were voltage clamped in the whole‐cell configuration. The pipette solution contained ATP (5 mM). 2. A hyperpolarization‐activated sodium‐potassium current (H‐current: IH) was separated from other membrane currents in a nominally calcium‐free solution containing cobalt (2 mM), magnesium (4 mM), barium (2 mM), tetraethylammonium (20 mM), tetrodotoxin (3 microM), apamin (30 nM) and 4‐aminopyridine (1 mM). IH was selectively blocked by caesium (10‐300 microM). 3. The steady‐state activation of IH occurred between ‐60 and ‐130 mV. The H‐conductance was 4.1‐6.6 nS at the half‐activation voltage of ‐90 mV. With the concentrations of potassium and sodium ions in the superfusate at 20 and 70 mM, respectively, the reversal potential of IH was about ‐20 mV. IH was activated with a time constant of 2.8 s at ‐90 mV and 22 degrees C. The Q10 between 16 and 26 degrees C was 4.3. 4. A non‐hydrolysable ATP analogue in the pipette solution did not support IH activation. Intracellular ‘loading’ of GTP‐gamma‐S (30‐500 microM) led to a progressive activation of IH. 5. Forskolin (10 microM) increased the maximum conductance of IH by 70%. This was associated with a depolarizing shift in the half‐activation voltage (5‐10 mV) and in the voltage dependence of the activation/deactivation time constant of IH. 6. Essentially the same results as with forskolin were obtained by intracellular ‘loading’ with cyclic AMP (3‐10 microM) or bath application of 8‐bromo cyclic AMP (0.1‐1 mM), dibutyryl cyclic AMP (1 mM) and 3‐isobutyl‐1‐methylxanthine (0.1‐1 mM). 7. The protein kinase inhibitor H‐8 (1‐10 microM) decreased the peak amplitude of IH. Phorbol 12‐myristate 13‐acetate (10 microM), a protein kinase C activator, was without effect. 8. It is concluded that a voltage‐dependent cation current can be regulated by the basal activity of adenylate cyclase, presumably through protein kinase A, in vertebrate sympathetic neurones.