ADENOSINE MODULATES VOLTAGE-GATED CA2+ CHANNELS IN ADULT-RAT SYMPATHETIC NEURONS
ADENOSINE MODULATES VOLTAGE-GATED CA2+ CHANNELS IN ADULT-RAT SYMPATHETIC NEURONS
复制标题
DOI：
10.1152/jn.1993.70.2.610
复制
发表时间：
1993-08-01
影响因子：
2.5
通讯作者：
IKEDA, SR
中科院分区：
文献类型：
--
作者：
ZHU, Y;IKEDA, SR
1.采用全细胞膜片钳技术研究腺苷对成年大鼠上级颈神经节（SCG）神经元钙通道的调节作用.腺苷产生浓度依赖性降低钙电流的幅度与EC 50为174 nM和最大抑制36%。腺苷对Ca 2+电流的影响具有时间和电压依赖性。在+ 10 mV时抑制作用最大，在超极化或去极化电位时抑制作用减弱.在长时间（> 1分钟）暴露于10 μ M腺苷后，抑制反应脱敏，而多次短暂（< 30秒）应用则轻微降低了随后的反应.腺苷诱导的Ca 2+电流抑制由Al型腺苷受体介导，因为A 1受体选择性激动剂氯-N-环戊基腺苷的半数最大抑制值比A 2受体选择性激动剂2-对-（2-羧乙基）苯乙基氨基-5 '-N-乙基甲酰氨基腺苷盐酸盐的半数最大抑制值低1，000倍（分别为33 nM对40 μ M）。一种鸟嘌呤核苷酸结合蛋白（G蛋白）可能参与腺苷的作用，这是因为：1）去极化电压预脉冲可大大减轻腺苷对钙通道电流的抑制作用; 2）尾电流分析表明腺苷使钙通道激活向更高的去极化电位移动;和3）腺苷抑制被2 mM细胞内鸟苷5 ′-O-（2-硫代二磷酸）或500 ng/ml百日咳毒素预处理消除。腺苷似乎不抑制L型钙通道，因为由二氢吡啶“激动剂"2，6-二甲基-3-甲氧羰基-5-硝基-4-（2-三氟甲基-苯基）-1，4-二氢吡啶（2 μ M）诱导的延长的尾电流成分不受腺苷的影响。腺苷诱导的抑制作用在应用10 μ M ω-芋螺毒素GVIA后降低至约15%，表明腺苷主要抑制N型Ca 2+通道。抗ω-芋螺毒素GVIA的Ca 2+电流组分也抗ω-蛇毒素IVA（200 nM），表明SCG神经元中缺乏P型Ca 2+通道。总之，腺苷产生的剂量，时间和电压依赖性抑制钙电流SCG神经元。腺苷通过百日咳毒素敏感的G蛋白作用于SCG神经元中的A1腺苷受体亚型，以抑制N型Ca 2+通道和未鉴定的Ca 2+电流成分。腺苷对交感神经元Ca ~（2+）电流的调节可能是其抑制神经递质释放的重要机制。
1. Ca2+-channel modulation by adenosine was investigated in enzymatically dispersed adult rat superior cervical ganglion (SCG) neurons using the whole-cell variant of the patch-clamp technique.2. Adenosine produced a concentration-dependent decrease in the Ca2+-current amplitude with an EC50 of 174 nM and maximum inhibition of 36%. The effects of adenosine on the Ca2+ current were both time and voltage dependent. The inhibition was maximal at + 10 mV and decreased at either hyperpolarizing or depolarizing potentials.3. The inhibitory response desensitized after prolonged (> 1 min) exposure to 10 muM adenosine, whereas multiple brief (< 30 s) applications slightly decreased the subsequent response.4. Adenosine-induced Ca2+-current inhibition was mediated by an Al-type adenosine receptor, because the half-maximal inhibition value for an A, receptor selective agonist, chloro-N-cyclopentyladenosine, was 1,000-fold lower than that for an A2 receptor selective agonist, 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarbozamido adenosine hydrochloride (33 nM vs. 40 muM, respectively).5. A guanine nucleotide binding protein (G protein) appeared to be involved in the action of adenosine, because: 1) the adenosine-induced current inhibition could be largely relieved by depolarizing voltage prepulses; 2) tail current analysis revealed that adenosine shifted Ca2+-channel activation to more depolarized potentials; and 3) adenosine inhibition was abolished by 2 mM intracellular guanosine 5'-O-(2-thiodiphosphate) or 500 ng/ml pertussis toxin pretreatment.6. Adenosine did not appear to inhibit L-type Ca2+ channels, because the prolonged tail current component induced by the dihydropyridine ''agonist'' 2,6-dimethy-3-carbomethoxy-5-nitro-4 (2-trifluoromethyl-phenyl)-1,4-dihydropyridine (2 muM) was not affected by adenosine.7. Adenosine-induced inhibition was reduced to approximately 15% after application of 10 muM omega-conotoxin GVIA, suggesting that adenosine primarily inhibits N-type Ca2+ channels. The Ca2+-current component resistant to omega-conotoxin GVIA was also resistant to omega-agatoxin IVA (200 nM), suggesting a lack of P-type of Ca2+ channels in SCG neurons.8. In conclusion, adenosine produces a dose-, time-, and voltage-dependent inhibition of Ca2+ currents in SCG neurons. Adenosine acts on an A1 adenosine receptor subtype in SCG neurons via a pertussis toxin-sensitive G protein to inhibit N-type Ca2+ channels and an unidentified Ca2+-current component. Modulation of Ca2+ currents by adenosine may be an important mechanism for its inhibitory effect on neurotransmitter release in sympathetic neurons.