Analysis of nociceptin-induced spontaneous transient outward currents and their physiological function in the CNS

自发性瞬时外向电流(STOCs)存在于外周神经元和平滑肌细胞，但很少见于中枢神经元。利用制霉菌素穿孔膜片钳技术，我们成功地记录了小鼠齿状回颗粒细胞的STOCs。伤害素增加STOCs的波幅和频率。我们认为STOCs的调制是调节中枢神经元细胞活动的一种新手段，并研究了其增强的特点和机制。全细胞电流-电压关系表现为外向整流，反转电位接近K的平衡电位，去极化时STOCs的出现频率增加。四乙基铵、硫杆菌毒素和钙离子螯合剂BAPTA-AM对STOCs有抑制作用。这些结果提示大电导Ca~(2+)和Gt~(2+)激活的K~(++)通道参与其中。内向外配置的单通道记录显示，钙激活的K^+通道的电导范围从82到352p…伤害素的增强作用可被[Phe^1Ψ(CH-NH)Gly^2]Nociceptin(1-13)NH所抵消。Cd^lt；2+不影响瞬时外向电流，也不影响伤害素的增强作用。在对照条件下，伤害素、茶碱和环状ADP核糖可诱发持续时间较短的瞬时外向电流，而肌醇1，4，5-三磷酸除可诱发持续时间较短的电流外，还可诱发持续时间较长的瞬时外向电流。兰诺定可抑制伤害素增加STOC。我们的数据表明，是Ca^&lt；2+&gt；火花，而不是Ca^&lt；2+&gt；夸克，瞬时激活大电导钙激活的K~+通道，以诱导瞬时外向电流，Nociceptin可能敏化Ryanodine受体，增加瞬时外向电流，从而降低细胞的兴奋性。即使在伤害素受体基因敲除的小鼠中，也观察到了伤害素诱导的STOCs的幅度和频率的增加，这表明存在受体亚型。在本研究中，我们首先揭示了STOCs在中枢神经系统的存在和特征，以及G蛋白偶联受体对STOCs的调节作用。较少

Spontaneous transient outward currents (STOCs) have been found in peripheral neurons and smooth muscle cells, but rarely in central neurons. Using a nystatin-perforated patch clamp technique, we succeeded in recording STOCs in mouse dentate gyrus granule cells. Nociceptin increased the amplitude and frequency of STOCs. We consider modulation of STOCs to be a new means to regulate cell activity in central neurons, and studied their characteristics and mechanism of augmentation. The whole-cell current-voltage relationship showed outward rectification and the reversal potential was close to the equilibrium potential for K The frequency of STOCs increased at depolarized potentials. Tetraethylammonium, iberiotoxin and a Ca^<2+> chelator BAPTA-AM inhibited STOCs. These results suggest the involvement of large-conductance Ca^<2+>-activated K^+ channels. Single-channel recordings in the inside-out configuration revealed Ca^<2+>-activated K^+ channels with a conductance ranging from 82 to 352 p … More S. The augmenting effect of nociceptin was cancelled by [Phe^1Ψ(CH -NH)Gly^2]Nociceptin(1-13)NH. Cd^<2+> did not affect the transient outward currents or augmentation by nociceptin. Whereas nociceptin, theophylline and cyclic ADP ribose induced transient outward currents with short duration observed under control conditions, inositol 1, 4, 5-trisphosphate induced transient outward currents with long duration, in addition to those with short duration. Ryanodine inhibited nociceptin from augmenting STOCs. Our data suggest that Ca^<2+> sparks, not Ca^<2+> quarks, transiently activate large-conductance Ca -activated K^+ channels to induce transient outward currents Nociceptin probably sensitizes ryanodine receptors and increases transient outward currents to reduce cell excitability. Nociceptin-induced increase in the amplitude and frequency of STOCs was observed even in the nociceptin receptor knockout mice, suggesting the presence of receptor subtype. In this study, we first revealed the presence and the characteristics of STOCs in the CNS and the modulation of STOCs by G protein coupled receptor. Less