Opioid inhibition of Ca2+ channel subtypes in bovine chromaffin cells: Selectivity of action and voltage dependence
Opioid inhibition of Ca2+ channel subtypes in bovine chromaffin cells: Selectivity of action and voltage dependence
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DOI：
10.1111/j.1460-9568.1996.tb01301.x
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发表时间：
1996-08-01
影响因子：
3.4
通讯作者：
Pollo, A
中科院分区：
文献类型：
--
作者：
Albillos, A;Carbone, E;Pollo, A
牛染色质细胞具有高电压激活的Ca2+通道亚型的混合物：l型，二氢吡啶敏感通道，N-， P-和q型，omega- concontoxin mviic敏感通道。在这些细胞中，我们研究了阿片激动剂-脑啡肽对Ba2+电流的可逆、纳洛酮拮抗抑制（IC50 = 272 nM）。这种抑制可以分解为电压依赖性和电压非依赖性成分。第一个特征是在0 mV时Ba2+电流的缓慢激活动力学和+90 mV短预脉冲诱导的电流易化。第二种被估计为在促进方案后持续存在的残留抑制。这两种抑制成分因细胞而异，各占总抑制量的一半左右。用gdp - β - s或百日咳毒素细胞预处理替代内部GTP完全消除了阿片类药物的电压依赖性抑制，部分保留了电压非依赖性成分。阿片类药物诱导的抑制对任何Ca2+通道亚型都没有选择性，在添加特异性Ca2+通道拮抗剂后也不会被阻止。然而，当分别分析每种通道类型对电压依赖和电压无关调制的贡献时，可以实现明确的区分。电压无关的抑制对所有Ca2+通道亚型有效，但主要对l型Ca2+通道有效。电压依赖性过程被ω -conotoxin- mviic消除，但不受硝苯地平影响，因此严格限制于非l型通道（N-， P-和q型）。我们的数据表明，在功能上，阿片受体介导的L型和非L型通道的调节是不同的，即两类通道共享对牛嗜铬细胞儿茶酚胺分泌的主要控制。
Bovine chromaffin cells possess a mixture of high-voltage-activated Ca2+ channel subtypes: L-type, dihydropyridine-sensitive channels, and N-, P- and Q-types, omega-conotoxin MVIIC-sensitive channels. In these cells, we studied the reversible, naloxone-antagonized inhibition of Ba2+ currents by the opioid agonist met-enkephalin (IC50 = 272 nM). This inhibition could be resolved into a voltage-dependent and a voltage-independent component. The first was revealed by its slow Ba2+ current activation kinetics at 0 mV and by the current facilitation induced by short prepulses to +90 mV. The second was estimated as the residual inhibition persisting after the facilitation protocol. The two inhibitory components varied markedly from cell to cell and each contributed to about half of the total inhibition. Replacement of internal GTP by GDP-beta-S or cell pretreatment with pertussis toxin completely abolished the voltage-dependent inhibition by opioids, partially preserving the voltage-independent component. The opioid-induced inhibition was not selective for any Ca2+ channel subtype, being not prevented after the addition of specific Ca2+ channel antagonists. However, when separately analysing the contribution of each channel type to the voltage-dependent and voltage-independent modulation, a clear-cut distinction could be achieved. The voltage-independent inhibition was effective on all Ca2+ channel subtypes but predominantly on L-type Ca2+ channels. The voltage-dependent process was abolished by omega-conotoxin-MVIIC, but unaffected by nifedipine, and was thus sharply restricted to non-L-type channels (N-, P- and Q-types). Our data suggest a functionally distinct opioid receptor-mediated modulation of L- and non-L-type channels, i.e. of the two channel classes sharing major control of catecholamine secretion from bovine chromaffin cells.