Pertussis toxin-sensitive guanine nucleotide-binding protein(S) couple adenosine A1 and 5-hydroxytryptamine1A receptors to the same effector systems in rat hippocampus: biochemical and electrophysiological studies.
Pertussis toxin-sensitive guanine nucleotide-binding protein(S) couple adenosine A1 and 5-hydroxytryptamine1A receptors to the same effector systems in rat hippocampus: biochemical and electrophysiological studies.
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发表时间：
1989-04
影响因子：
3.6
通讯作者：
J. Zgombick;S. Beck;C. D. Mahle;B. Craddock-Royal;S. Maayani
中科院分区：
文献类型：
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作者：
J. Zgombick;S. Beck;C. D. Mahle;B. Craddock-Royal;S. Maayani
引起类似细胞反应的不同膜受体可能共享信号转导的要素。本研究以大鼠海马腺苷（AD）和5-羟色胺（5-HT）受体为研究对象，采用生化和电生理技术验证了这种可能性。研究了AD受体介导的福斯克林刺激的大鼠海马膜腺苷酸环化酶活性抑制和大鼠海马锥体细胞静息膜电位超极化（RMP）引发的反应，并将其与5-HT1A受体引发的类似反应进行了比较。包括选择性AD A1激动剂(R)-苯异丙基腺苷[(R)-PIA]在内的一系列AD激动剂以浓度依赖的方式抑制福斯克林刺激的大鼠海马膜腺苷酸环化酶活性。环戊基茶碱（Cyclopentyltheophylline， CPT）是一种选择性AD A1拮抗剂，是一种有效的竞争性拮抗剂，其解离常数（Kb）为6 nM （Schild分析）。激动剂EC50值和拮抗剂Kb值的排序以及立体选择性与该受体属于AD A1受体的分类一致。Spiperone是一种有效的5-HT1A拮抗剂，竞争性地拮抗5- ht介导的福斯克林刺激的大鼠海马膜腺苷酸环化酶活性抑制，Kb值为14 nM。细胞内记录技术显示，AD、(R)-PIA、5-HT和5-羧基氨基色胺（5-CT）在同一海马锥体细胞内引发了RMP的浓度依赖性超极化。AD或5-HT类似物在单个锥体细胞中获得的最大超极化是相同的。CPT和spiperone分别通过(R)-PIA和5-CT拮抗超极化。饱和浓度的spiperone不能拮抗(R)- pia介导的反应，CPT也不能阻断生化或电生理制剂中5-HT引起的反应。与单独使用(R)-PIA相比，5-HT和(R)-PIA的饱和浓度联合引起了非加性的生化反应。同样，在电压箝位条件下进行的电生理实验表明，AD和5-CT的最大有效浓度表现出非加性行为。由于这些激动剂混合时引起的外向电流明显小于这些药物单独引起的电流的代数和，我们推断AD A1和5-HT1A受体群体激活了一个共同的鸟嘌呤核苷酸结合蛋白池。（摘要删节为400字）
Distinct membrane receptors that elicit similar cellular responses may share elements of signal transduction. In the present study, rat hippocampal adenosine (AD) and 5-hydroxytryptamine (5-HT) receptors were chosen to test this possibility using biochemical and electrophysiological techniques. Responses elicited by the AD receptor that mediates the inhibition of forskolin-stimulated adenylyl cyclase activity in rat hippocampal membranes and hyperpolarization of resting membrane potential (RMP) in rat hippocampal pyramidal cells were characterized and compared, in the same preparation, with those analogous responses elicited by the 5-HT1A receptor. A series of AD agonists including the selective AD A1 agonist (R)-phenylisopropyladenosine [(R)-PIA] inhibited forskolin-stimulated adenylyl cyclase activity in rat hippocampal membranes in a concentration-dependent manner. Cyclopentyltheophylline (CPT), a selective AD A1 antagonist, was a potent, competitive antagonist of this response with a dissociation constant (Kb) of 6 nM (Schild analysis). The rank order of agonist EC50 values and antagonist Kb values, as well as stereoselectivity, are consistent with the classification of this receptor as the AD A1 receptor. Spiperone, a potent 5-HT1A antagonist, competitively antagonized 5-HT-mediated inhibition of forskolin-stimulated adenylyl cyclase activity in rat hippocampal membranes with a Kb value of 14 nM. Intracellular recording techniques revealed that AD, (R)-PIA, 5-HT, and 5-carboxyamidotryptamine (5-CT) elicited concentration-dependent hyperpolarization of RMP within the same hippocampal pyramidal cell. The maximal hyperpolarization obtained for the AD or 5-HT analogs was the same for individual pyramidal cells. CPT and spiperone antagonized the hyperpolarization by (R)-PIA and 5-CT, respectively. Saturating concentrations of spiperone failed to antagonize (R)-PIA-mediated responses and CPT did not block responses elicited by 5-HT in either the biochemical or electrophysiological preparations. The combination of saturating concentrations of 5-HT and (R)-PIA evoked nonadditive biochemical responses relative to those observed with (R)-PIA alone. Similarly, electrophysiological experiments conducted under voltage-clamp conditions demonstrated that maximally effective concentrations of AD and 5-CT exhibited nonadditive behavior. Because the amount of outward current elicited when these agonists were coperfused was significantly less than the algebraic sum of the currents evoked individually by these agents, we infer that a population of AD A1 and 5-HT1A receptors activates a common pool of guanine nucleotide-binding proteins.(ABSTRACT TRUNCATED AT 400 WORDS)