FMRFamide neuropeptides simultaneously increase and decrease K+ currents in an identified neurone
FMRFamide neuropeptides simultaneously increase and decrease K+ currents in an identified neurone
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FMRFamide 神经肽同时增加和减少已识别神经元中的 K 电流
作者：
G. Cottrell
Phe-Met-Arg-Phe-NH2（或 FMRFamide）是在蛤蜊的神经节中发现的，在一些软体动物物种中具有有效的心脏刺激活性，但在其他物种中具有心脏抑制作用，并产生某些非心肌的收缩2。具有相似特性的肽存在于蜗牛 Helix3 的神经节中，并且被认为与 Macrocallista 肽的不同之处在于具有一个或多个与末端游离氨基氮结合的附加氨基酸。在肾上腺髓质颗粒和纹状体中鉴定出同源阿片肽 Tyr-Gly-Gly-Phe-Met-Arg-Phe（或 YGGFMRF，使用单字母缩写 4）。 YGGFMRFamide 的色谱特性与 Helix 肽比 FMRFamide 本身更相似，但不完全相同（D. A. Price、M. J. Greenberg 和 G.A.C.，未发表）。 FMRFamide 对螺旋神经元具有强大而复杂的作用。每个大脑神经节中的一个神经元，即 C1 或巨型血清素神经元 (GSN)，在静息膜水平上被 FMRFamide 超极化，但在负电位较小的情况下去极化6。我在此表明，YGGFMRFamide 与 FMRFamide 具有相似的作用，并进一步研究了 GSN 两种反应背后的离子机制。结果表明，超极化、外向电流响应是由 K+ 电导增加引起的，而去极化响应（记录为净外向电流的减少）是由于 Ca2+ 激活的 K+ 电流的抑制。
Phe-Met-Arg-Phe-NH2, or FMRFamide, discovered in ganglia of the clam Macrocallista nimbosa1 has potent cardio-stimulatory activity in some molluscan species, but is cardio-inhibitory in others, and produces contractions of certain non-cardiac muscles2. A peptide with similar properties is present in the ganglia of the snail Helix3, and is thought to differ from the Macrocallista peptide in having one or more additional amino acids combined with the terminal free amino nitrogen. An homologous opiate peptide, Tyr-Gly-GIy-Phe-Met-Arg-Phe (or YGGFMRF, using single letter abbreviations4), was identified in adrenal medullary granules and the striatum5. YGGFMRFamide has chromatographic properties more similar, though not identical, to the Helix peptide than FMRFamide itself (D. A. Price, M. J. Greenberg and G.A.C., unpublished). FMRFamide has potent and complex effects on Helix neurones. One neurone in each cerebral ganglion, the C1 or giant serotonin neurone (GSN), is hyperpolarized by FMRFamide at the resting membrane level, but depolarized at less negative potentials6.I show here that YGGFMRFamide has similar effects to FMRFamide and examine further the ionic mechanisms underlying the two responses of the GSN. The results indicate that the hyperpolarizing, outward current response results from an increase in conductance to K+ whereas the depolarizing response, which was recorded as a reduction in net outward current, is due to the suppression of a Ca2+ activated K+current.