Analysis of adenosine actions on Ca2+ currents and synaptic transmission in cultured rat hippocampal pyramidal neurones.
Analysis of adenosine actions on Ca2+ currents and synaptic transmission in cultured rat hippocampal pyramidal neurones.
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DOI：
10.1113/jphysiol.1991.sp018515
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发表时间：
1991-04
期刊：
影响因子：
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通讯作者：
K. Scholz;R. Miller
中科院分区：
文献类型：
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作者：
K. Scholz;R. Miller
1. 利用全细胞膜片钳技术记录培养大鼠海马锥体神经元细胞体的钙电流和突触电流，研究了腺苷受体在减少钙电流（ICa）和触发突触前抑制中的作用。使用指示染料Fura‐2记录细胞内Ca2+，以进一步了解腺苷激动剂的作用。2. 腺苷类似物2‐氯腺苷（2‐CA）降低了这些神经元中的ICa。当Ba2+作为电荷载体通过Ca2+通道时，这种作用也很明显。在Fura‐2测量的去极化电压箝位脉冲期间，腺苷还减少了Ca2+流入细胞体。各种腺苷受体激动剂的效价如下：环戊基腺苷大于环己基腺苷大于或等于R‐苯基异丙基腺苷大于2‐CA，大于S‐苯基异丙基腺苷，与A1腺苷受体的药理学特征一致。3. 特异性A1受体拮抗剂环戊基茶碱（cyclopentyltheophylline， CPT）以竞争性方式阻断2‐CA对ICa的作用。4. 用百日咳毒素（PTX; 250 ng/ml）预先孵育培养细胞，可消除2 - CA对ICa的作用。用GTP类似物GTP‐γ‐S（鸟苷‐5′‐O‐（3‐硫代三磷酸））进行细胞内透析可增强2‐CA的作用，并使反应不可逆。5. 在全细胞电压箝位下，利用细胞外电极刺激锥体神经元，记录了锥体神经元的兴奋性突触后电流（EPSCs）。2‐CA能有效且可逆地降低epsc的振幅。这种作用被证明是由于突触前神经递质释放的抑制。6. 不同腺苷激动剂还原EPSCs的效价顺序为：环戊基腺苷大于环己基腺苷大于等于R‐苯基异丙基腺苷大于2‐CA大于S‐苯基异丙基腺苷。CPT以竞争方式抑制2‐CA的作用。7. 用250 ng/ml PTX预处理可以消除2 - CA对突触传递的影响，表明PTX敏感的G -蛋白参与了这一作用。8. 这些结果表明腺苷受体的激活确实会导致海马锥体神经元中ICa的减少。此外，这种作用和腺苷类似物对兴奋性突触传递的减少都是由PTX敏感的G蛋白介导的，并且具有相同的药理特性。
1. The role of adenosine receptors in reducing calcium currents (ICa) and in triggering presynaptic inhibition was studied using whole‐cell patch‐clamp techniques to record ICa and synaptic currents from the cell bodies of cultured rat hippocampal pyramidal neurones. Recordings of intracellular Ca2+ using the indicator dye Fura‐2 were used to obtain further insights into the actions of adenosine agonists. 2. The adenosine analogue 2‐chloroadenosine (2‐CA) reduced ICa in these neurones. This action was also evident when Ba2+ was used as the charge carrier through Ca2+ channels. Adenosine also reduced the influx of Ca2+ into the cell body during a depolarizing voltage‐clamp pulse as measured with Fura‐2. The potency of various adenosine receptor agonists was as follows: cyclopentyladenosine greater than cyclohexyl‐adenosine greater than or equal to R‐phenylisopropyladenosine greater than 2‐CA greater than S‐phenylisopropyladenosine, consistent with the pharmacological profile of an A1 adenosine receptor. 3. The specific A1 receptor antagonist cyclopentyltheophylline (CPT) blocked the actions of 2‐CA on ICa in a competitive fashion. 4. The actions of 2‐CA on ICa were abolished by pre‐incubation of cultured cells with pertussis toxin (PTX; 250 ng/ml). Intracellular dialysis with the GTP analogue GTP‐gamma‐S (guanosine‐5'‐O‐(3‐thiotriphosphate] enhanced the actions of 2‐CA and rendered the response irreversible. 5. Excitatory postsynaptic currents (EPSCs) were recorded from pyramidal neurones under whole‐cell voltage clamp by stimulating nearby neurones with an extracellular electrode. 2‐CA potently and reversibly reduced the amplitude of EPSCs. This action was shown to be due to presynaptic inhibition of neurotransmitter release. 6. The order of potency of different adenosine agonists in reducing EPSCs was as follows: cyclopentyladenosine greater than cyclohexyladenosine greater than or equal to R‐phenylisopropyladenosine greater than 2‐CA greater than S‐phenylisopropyladenosine. CPT inhibited the action of 2‐CA in a competitive fashion. 7. The effects of 2‐CA on synaptic transmission were abolished by pre‐treatment with 250 ng/ml PTX, indicating that a PTX‐sensitive G‐protein is involved in this action. 8. These results indicate that activation of adenosine receptors does induce a reduction in ICa in hippocampal pyramidal neurones. Furthermore, this effect and the reduction of excitatory synaptic transmission by adenosine analogues are both mediated by PTX‐sensitive G‐proteins and have identical pharmacological properties.