Jacklet J W
Department of Biological Sciences, University at Albany, SUNY 12222, USA.
Invert Neurosci. 1997 Jun;3(1):1-14. doi: 10.1007/BF02481710.
Nitric oxide (NO) is an unconventional neurotransmitter and neuromodulator molecule that is increasingly found to have important signaling functions in animals from nematodes to mammals. NO signaling mechanisms in the past were identified largely through experiments on mammals, after the discovery of NO's vasodilatory functions. The use of gene knock out mice has been particularly important in revealing the functions of the several isoforms of nitric oxide synthase (NOS), the enzyme that produces NO. Recent studies have revealed rich diversity in NO signaling. In addition to the well-established pathway in which NO activates guanylyl cyclase and cGMP production, redox mechanisms involving protein nitrosylation are important contributors to modulation of neurotransmitter release and reception. NO signaling studies in invertebrates are now generating a wealth of comparative information. Invertebrate NOS isoforms have been identified in insects and molluscs, and the conserved and variable amino acid sequences evaluated. Calcium-calmodulin dependence and cofactor requirements are conserved. NADPH diaphorase studies show that NOS is found in echinoderms, coelenterates, nematodes, annelids, insects, crustaceans and molluscs. Accumulating evidence reveals that NO is used as an orthograde transmitter and cotransmitter, and as a modulator of conventional transmitter release. NO appears to be used in diverse animals for certain neuronal functions, such as chemosensory signaling, learning, and development, suggesting that these NO functions have been conserved during evolution. The discovery of NO's diverse and unconventional signaling functions has stimulated a plethora of enthusiastic investigations into its uses. We can anticipate the discovery of many more interesting and some surprising NO signaling functions.
一氧化氮（NO）是一种非常规的神经递质和神经调节分子，越来越多的研究发现它在从线虫到哺乳动物的动物体内具有重要的信号传导功能。在发现NO的血管舒张功能后，过去NO的信号传导机制主要是通过对哺乳动物的实验来确定的。基因敲除小鼠的使用在揭示一氧化氮合酶（NOS，产生NO的酶）的几种同工型的功能方面尤为重要。最近的研究揭示了NO信号传导的丰富多样性。除了已确立的NO激活鸟苷酸环化酶和产生cGMP的途径外，涉及蛋白质亚硝基化的氧化还原机制也是调节神经递质释放和接收的重要因素。目前，对无脊椎动物的NO信号传导研究正在产生大量的比较信息。在昆虫和软体动物中已鉴定出无脊椎动物的NOS同工型，并对其保守和可变的氨基酸序列进行了评估。钙-钙调蛋白依赖性和辅因子需求是保守的。NADPH黄递酶研究表明，在棘皮动物、腔肠动物、线虫、环节动物、昆虫、甲壳类动物和软体动物中都发现了NOS。越来越多的证据表明，NO被用作顺行递质和共递质，以及传统递质释放的调节剂。NO似乎在多种动物中用于某些神经元功能，如化学感受信号传导、学习和发育，这表明这些NO功能在进化过程中得以保留。NO多样且非常规的信号传导功能的发现激发了大量关于其用途的热情研究。我们可以预期会发现更多有趣甚至令人惊讶的NO信号传导功能。
