Bernstein M, Behnisch T, Balschun D, Reymann K G, Reiser G
Otto-von-Guericke Universität Magdeburg, Institut für Neurobiochemie, Germany.
Neuropharmacology. 1998;37(2):169-78. doi: 10.1016/s0028-3908(98)00012-4.
Intracellular Ca2+ ([Ca2+]i) signals induced by metabotropic glutamate receptor (mGluR) agonists and by purinergic agonists in cultured hippocampal astrocytes were investigated using [Ca2+]-sensitive fluorophores. The mGluR agonists (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) and (R,S)-3,5-dihydroxyphenylglycine (DHPG) induced [Ca2+]i responses in 76 and 93% of the cells, respectively. The broad-spectrum mGluR antagonist (+)-alpha-methyl-4-carboxyphenylglycine (MCPG) and the mGluR1 antagonists (S)-4-carboxy-3-hydroxyphenylglycine (4C3HPG) and (S)-4-carboxyphenylglycine (4CPG) suppressed the agonist-evoked [Ca2+]i response in about 25% of the cells completely and in about 60% partially, depending on the agonist concentration employed. Together with immunohistochemical receptor localisations these results suggest the presence of at least two subpopulations of class I mGluRs recruited from the truncated splice variants of mGluR1 (mGluR 1b, 1c, 1d) and/or hitherto unknown glial-specific class I mGluRs. Of the hippocampal astrocytes 88, 92 or 83% of the cells responded with a [Ca2+]i elevation (mostly oscillations) to application of ATP, ADP, or 2-methylthio-ATP (2-MeS-ATP), respectively, whereas only 14 and 5% responded to AMP and adenosine, respectively, indicating the predominance of P2 receptors. The ATP-induced [Ca2+]i signal was suppressed by suramin. Release of Ca2+ from intracellular stores was involved in the response to ATP because the cells also exhibited [Ca2+]i elevations in Ca2+-free medium. Cells did not respond to 10 microM UTP. We conclude that the P2Y subtype represents the main [Ca2+]i-linked purinoceptor in hippocampal astrocytes. Sequential application of ATP and DHPG in Ca-free medium showed that metabotropic glutamate and purinergic receptors initiate release of Ca2+ from subsets of cyclopiazonic acid-sensitive Ca2+ stores which are partly independent.
使用钙敏感荧光团研究了代谢型谷氨酸受体（mGluR）激动剂和嘌呤能激动剂在培养的海马星形胶质细胞中诱导的细胞内钙离子浓度（[Ca2+]i）信号。mGluR激动剂（1S,3R）-1-氨基环戊烷-1,3-二羧酸（ACPD）和（R,S）-3,5-二羟基苯甘氨酸（DHPG）分别在76%和93%的细胞中诱导了[Ca2+]i反应。广谱mGluR拮抗剂（+）-α-甲基-4-羧基苯甘氨酸（MCPG）以及mGluR1拮抗剂（S）-4-羧基-3-羟基苯甘氨酸（4C3HPG）和（S）-4-羧基苯甘氨酸（4CPG），根据所使用的激动剂浓度，在约25%的细胞中完全抑制了激动剂诱发的[Ca2+]i反应，在约60%的细胞中部分抑制了该反应。结合免疫组织化学受体定位，这些结果表明至少存在两个I类mGluR亚群，它们是从mGluR1的截短剪接变体（mGluR 1b、1c、1d）和/或迄今未知的胶质细胞特异性I类mGluR中募集而来的。在海马星形胶质细胞中，分别有88%、92%或83%的细胞对ATP、ADP或2-甲硫基ATP（2-MeS-ATP）的应用产生[Ca2+]i升高（主要是振荡）反应，而分别只有14%和5%的细胞对AMP和腺苷有反应，这表明P2受体占主导地位。ATP诱导的[Ca2+]i信号被苏拉明抑制。细胞内钙库释放Ca2+参与了对ATP的反应，因为细胞在无钙培养基中也表现出[Ca2+]i升高。细胞对10 microM UTP无反应。我们得出结论，P2Y亚型是海马星形胶质细胞中主要的[Ca2+]i相关嘌呤受体。在无钙培养基中依次应用ATP和DHPG表明，代谢型谷氨酸受体和嘌呤能受体引发了对环匹阿尼酸敏感的钙库亚群释放Ca2+，这些亚群部分是独立的。
