Donevan S D, Rogawski M A
Neuronal Excitability Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 29892, USA.
Proc Natl Acad Sci U S A. 1995 Sep 26;92(20):9298-302. doi: 10.1073/pnas.92.20.9298.
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors that lack the glutamate receptor GluR2 subunit are Ca(2+)-permeable and exhibit inwardly rectifying current responses to kainate and AMPA. A proportion of cultured rat hippocampal neurons show similar Ca(2+)-permeable inwardly rectifying AMPA receptor currents. Inward rectification in these neurons was lost with intracellular dialysis and was not present in excised outside-out patches but was maintained in perforated-patch whole-cell recordings, suggesting that a diffusible cytoplasmic factor may be responsible for rectification. Inclusion of the naturally occurring polyamines spermine and spermidine in the recording pipette prevented loss of rectification in both whole-cell and excised-patch recordings; Mg2+ and putrescine were without effect. Inward rectification of Ca(2+)-permeable AMPA receptors may reflect voltage-dependent channel block by intracellular polyamines.
缺乏谷氨酸受体GluR2亚基的α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）受体是钙离子通透的，并且对海人藻酸和AMPA表现出内向整流电流反应。一部分培养的大鼠海马神经元显示出类似的钙离子通透内向整流AMPA受体电流。这些神经元中的内向整流在细胞内透析时消失，在切除的外侧向外膜片中不存在，但在穿孔膜片全细胞记录中得以维持，这表明一种可扩散的细胞质因子可能是整流的原因。在记录电极中加入天然存在的多胺精胺和亚精胺可防止全细胞和膜片切除记录中整流的丧失；镁离子和腐胺则没有作用。钙离子通透AMPA受体的内向整流可能反映了细胞内多胺对电压依赖性通道的阻断。
