Zayas Ricardo M, Qazi Sanjive, Morton David B, Trimmer Barry A
Department of Biology, Dana Laboratory, Tufts University, Medford, Massachusetts 02155, USA.
J Neurochem. 2002 Oct;83(2):421-31. doi: 10.1046/j.1471-4159.2002.01147.x.
In addition to their ionotropic role, neuronal nicotinic acetylcholine receptors (nAChRs) can influence second messenger levels, transmitter release and gene transcription. In this study, we show that nAChRs in an insect CNS control cGMP levels by coupling to NO production. In conditions that inhibit spiking, nicotine induced cGMP synthesis. This increase in cGMP was blocked by nicotinic antagonists, and by inhibitors of both nitric oxide synthase and soluble guanylyl cyclase. The nicotinic-evoked increase in cGMP was localized to specific NO-sensitive neurons in the CNS, several of which are identified motoneurons. Because NO production requires Ca2+, we investigated the effect of nicotinic stimulation on [Ca2+]i in cultured neurons. We found that activation of nAChRs increased [Ca2+]i, which was blocked by nAChR antagonists. Nicotinic stimulation of neurons in the isolated CNS in low-Na+, also evoked increases in [Ca2+]i independent of fast changes in voltage. In addition, approximately 10% of the nicotinic-evoked [Ca2+]i increase in cultured neurons persisted when voltage-gated Ca2+ channels were blocked by Ni2+. Under the same conditions, nicotinic stimulation of cGMP in the CNS was unaffected. These combined results suggest that nicotinic stimulation is coupled to NOS potentially by directly gating Ca2+.
除了其离子型作用外，神经元烟碱型乙酰胆碱受体（nAChRs）还可影响第二信使水平、神经递质释放和基因转录。在本研究中，我们表明昆虫中枢神经系统中的nAChRs通过与一氧化氮（NO）生成偶联来控制环鸟苷酸（cGMP）水平。在抑制动作电位发放的条件下，尼古丁诱导cGMP合成。cGMP的这种增加被烟碱拮抗剂以及一氧化氮合酶和可溶性鸟苷酸环化酶的抑制剂所阻断。烟碱诱发的cGMP增加定位于中枢神经系统中特定的对NO敏感的神经元，其中一些是已鉴定的运动神经元。由于NO生成需要Ca2+，我们研究了烟碱刺激对培养神经元中[Ca2+]i的影响。我们发现nAChRs的激活增加了[Ca2+]i，这被nAChR拮抗剂所阻断。在低钠条件下对离体中枢神经系统中的神经元进行烟碱刺激，也能诱发[Ca2+]i的增加，且与电压的快速变化无关。此外，当电压门控Ca2+通道被Ni2+阻断时，培养神经元中约10%的烟碱诱发的[Ca2+]i增加持续存在。在相同条件下，中枢神经系统中烟碱对cGMP的刺激不受影响。这些综合结果表明，烟碱刺激可能通过直接门控Ca2+与一氧化氮合酶偶联。
