Dopamine enhancement and depression of glutamate-regulated calcium and electrical activity in hypothalamic neurons.
Dopamine enhancement and depression of glutamate-regulated calcium and electrical activity in hypothalamic neurons.
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多巴胺增强和抑制下丘脑神经元中谷氨酸调节的钙和电活动。
DOI：
10.1152/jn.1996.76.6.3934
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Belousov,AB
中科院分区：
文献类型：
--
作者：
vandenPol,AN;Cao,V;Belousov,AB
1.神经递质多巴胺存在于下丘脑的细胞体和下丘脑内外的轴突中。为了研究多巴胺对培养的大鼠下丘脑神经元的作用机制，特别是与Ca ~（2+）调节的关系，我们使用了Fura-2钙离子数字成像和全细胞膜片钳记录。我们专注于多巴胺对谷氨酸的调节作用。2.多巴胺给药对细胞内Ca 2+几乎没有或没有独立的影响。然而，在河豚毒素阻断动作电位和动作电位依赖性递质释放的情况下，多巴胺（10 μ M，2-3分钟）导致64个神经元中22%的谷氨酸诱发的Ca 2+升高增加，并在相同数量的神经元中抑制谷氨酸诱发的Ca 2+升高。短时间接触多巴胺会减少反应细胞的数量。3.多巴胺应用于神经元与升高的Ca 2+由于突触释放谷氨酸（在没有河豚毒素）通常会导致Ca 2+水平下降（40%的106个神经元），但有时增加胞质Ca 2+（10%的106个神经元）。与诱发活动相比，多巴胺在自发活动条件下对细胞的影响不同，这可能是由于多巴胺对突触前受体的影响，而突触前受体是在持续释放谷氨酸的条件下检测到的。4.在神经元发育的早期阶段（体外培养2天后的胚胎第18天）和体外培养60天后检测到多巴胺对谷氨酸反应的调节。5. D1、D2和D3多巴胺受体激动剂SKF 38393、喹吡罗和7-OH-DPAT（+/- 7羟基-二丙基氨基四氢萘）引起内源性谷氨酸释放引起的或外源性谷氨酸应用引起的Ca 2+水平降低。6.为了阻断下丘脑神经元释放多巴胺的作用，使用D1和D2多巴胺受体拮抗剂。与多巴胺一样，多巴胺拮抗剂在谷氨酸受体阻断期间对细胞内Ca 2+没有影响。在没有谷氨酸受体阻滞的情况下，D1拮抗剂SCH 23390（1 μ M）降低了响应细胞中的Ca 2 +;相反，D2拮抗剂依替氯必利（1 μ M）产生了延迟的Ca 2+水平升高。7.已知多巴胺通过G蛋白激活第二信使，而不依赖于膜电位或输入电阻的变化。全细胞记录被用来证明，平行于Ca 2+的调制，多巴胺谷氨酸介导的电活动产生了巨大的变化，一般抑制活动和超极化膜电位（15个神经元中的8个）。在少数神经元（15个中的5个）中，多巴胺增强了谷氨酸介导的兴奋性活动。8.多巴胺诱发的膜电位的变化，部分介导的谷氨酸作用的调制。多巴胺以剂量依赖性方式抑制谷氨酸诱发电流，单个神经元的Hill斜率范围为0.3至0.6。在河豚毒素或谷氨酸受体阻断剂存在下，多巴胺也可以引起下丘脑神经元的直接超极化作用，至少部分通过开放K+通道。9.谷氨酸作为下丘脑内的主要兴奋性递质起着重要作用。我们的数据支持这一假设，多巴胺对下丘脑神经元的影响的主要机制涉及谷氨酸的兴奋作用的调制，主要是通过抑制。这与谷氨酸活性的调节可能是整个神经系统中多巴胺作用的重要机制的假设是一致的。
1. The neurotransmitter dopamine is found throughout the hypothalamus both in cell bodies and in axons originating from intra- and extrahypothalamic sources. To study the mechanisms of action of dopamine on cultured rat hypothalamic neurons, particularly in relation to Ca2+ regulation, we used Ca2+ digital imaging with fura-2 and whole cell patch-clamp recording. We focused on the modulatory actions of dopamine on glutamate. 2. Dopamine administration had little or no independent effect on intracellular Ca2+. However, in the presence of tetrodotoxin to block action potentials and action-potential-dependent transmitter release, dopamine (10 microM for 2-3 min) caused an increase in glutamate-evoked Ca2+ rises in 22% of 64 neurons and depressed glutamate-evoked Ca2+ rises in an equal number of neurons. Shorter exposure to dopamine reduced the number of responding cells. 3. Dopamine application to neurons with an elevated Ca2+ due to synaptic release of glutamate (in the absence of tetrodotoxin) generally caused a decrease in Ca2+ levels (40% of 106 neurons), but sometimes increased cytosolic Ca2+ (10% of 106 neurons). That dopamine influenced cells differently in conditions of spontaneous activity compared with evoked activity may be due to dopamine effects on presynaptic receptors detected under conditions of ongoing synaptic release of glutamate. 4. Dopamine modulation of glutamate responses was detected at early stages of neuronal development (embryonic day 18 after 2 days in vitro) and also after 60 days in vitro. 5. The D1, D2, and D3 dopamine receptor agonists SKF38393, quinpirole, and 7-OH-DPAT (+/- 7 hydroxy-dipropylaminotetralin) caused a reduction in Ca2+ levels raised by endogenous glutamate release or evoked by exogenous glutamate application. 6. To block the actions of dopamine released by hypothalamic neurons, D1 and D2 dopamine receptor antagonists were used. As with dopamine, dopamine antagonists had no effect on intracellular Ca2+ during glutamate receptor blockade. In the absence of glutamate receptor block, the D1 antagonist SCH23390 (1 microM) reduced Ca2+ in responding cells; in contrast, the D2 antagonist eticlopride (1 microM) generated a delayed increase in Ca2+ levels. 7. Dopamine is known to activate second messengers through G proteins independent of changes in membrane potential or input resistance. Whole cell recording was used to demonstrate that, parallel to the modulation of Ca2+, dopamine exerted a dramatic change in glutamate-mediated electrical activity, generally depressing activity and hyperpolarizing the membrane potential (8 of 15 neurons). In a smaller number of neurons (5 of 15), dopamine enhanced glutamate-mediated excitatory activity. 8. Dopamine-evoked changes in membrane potential were in part mediated through modulation of glutamate actions. Dopamine depressed glutamate-evoked currents in a dose-dependent fashion, with Hill slopes in individual neurons ranging from 0.3 to 0.6. Dopamine could also evoke a direct hyperpolarizing action on hypothalamic neurons in the presence of tetrodotoxin or glutamate receptor blockers, at least in part by opening K+ channels. 9. Glutamate plays an important role as a primary excitatory transmitter within the hypothalamus. Our data support the hypothesis that a major mechanism of dopamine's influence on hypothalamic neurons involves the modulation of glutamate's excitatory action, mostly by inhibition. This is consistent with the hypothesis that modulation of glutamate activity may be an important mechanism of dopamine action throughout the nervous system.