Koike M, Iino M, Ozawa S
Department of Physiology, Gunma University School of Medicine, Japan.
Neurosci Res. 1997 Sep;29(1):27-36. doi: 10.1016/s0168-0102(97)00067-9.
Effects of 1-naphthyl acetyl spermine (NASPM), a synthetic analogue of Joro spider toxin (JSTX), on alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors were studied in cultured rat hippocampal neurons using the whole-cell patch clamp technique. A population of cultured neurons had AMPA receptors with a strong inward rectification and a high permeability to Ca2+ (type II neurons). Whereas most neurons (type I neurons) had AMPA receptors with a slight outward rectification and little Ca2+ permeability. NASPM selectively suppressed the inwardly rectifying and Ca(2+)-permeable AMPA receptors expressed in type II neurons. It had no effect on AMPA receptors in type I neurons. The blocking effect of NASPM on the Ca(2+)-permeable AMPA receptors was use and voltage-dependent. When the effect of NASPM reached a steady state, current responses induced by ionophoretic applications of kainate, a non-desensitizing agonist of AMPA receptors, in type II neurons were suppressed by NASPM in a dose-dependent manner at -60 mV (IC50 0.33 microM, and Hill coefficient 0.94). The response to kainate recovered partially after washing out NASPM. NASPM did not affect the Ca(2+)-permeable AMPA receptors when the neuronal membrane was held at potentials more positive than +40 mV. Furthermore, the blockade by NASPM which was attained at negative potentials was transiently removed by shifting membrane potential to +60 mV for 5 s together with a single ionophoretic application of kainate. NASPM would be useful as a pharmacological tool for elucidating both physiological and pathological significances of Ca(2+)-permeable AMPA receptors in the CNS.
采用全细胞膜片钳技术，在培养的大鼠海马神经元中研究了1-萘乙酰亚精胺（NASPM），一种乔罗蜘蛛毒素（JSTX）的合成类似物，对α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）型谷氨酸受体的影响。一群培养的神经元具有对Ca2+具有强内向整流和高通透性的AMPA受体（II型神经元）。而大多数神经元（I型神经元）具有轻微外向整流且Ca2+通透性小的AMPA受体。NASPM选择性抑制II型神经元中表达的内向整流和Ca(2+)通透性AMPA受体。它对I型神经元中的AMPA受体没有影响。NASPM对Ca(2+)通透性AMPA受体的阻断作用具有使用和电压依赖性。当NASPM的作用达到稳态时，在II型神经元中，由离子导入应用AMPA受体的非脱敏激动剂海藻酸诱导的电流反应在-60 mV时被NASPM以剂量依赖性方式抑制（IC50为0.33 microM，希尔系数为0.94）。洗脱NASPM后，对海藻酸的反应部分恢复。当神经元膜保持在比+40 mV更正的电位时，NASPM不影响Ca(2+)通透性AMPA受体。此外，通过将膜电位转移到+60 mV 5 s并同时单次离子导入应用海藻酸，可暂时消除在负电位下由NASPM实现的阻断。NASPM可作为一种药理学工具，用于阐明中枢神经系统中Ca(2+)通透性AMPA受体的生理和病理意义。
