Nicoletti F, Bruno V, Fiore L, Cavallaro S, Canonico P L
Institute of Pharmacology, University of Catania School of Medicine, Italy.
J Neurochem. 1989 Oct;53(4):1026-30. doi: 10.1111/j.1471-4159.1989.tb07390.x.
Inositol hexakisphosphate (InsP6) increased 45Ca2+ uptake in cultured cerebellar granule cells. This increase was concentration dependent (EC50 = 20 microM), exhibited slow kinetics, and was present after 5 days of cell maturation in culture. InsP6 also enhanced D-[3H]aspartate release in cerebellar granule cells at 11-12 days in vitro. Stimulation of 45Ca2+ uptake was also produced by inositol pentakisphosphate but not by inositol 1,3,4,5-tetrakisphosphate. The increase in 45Ca2+ influx induced by InsP6 was independent of extracellular Na+ and was only partially reduced by the organic calcium channel blocker nifedipine. The intrinsic action of InsP6 was not affected by competitive or noncompetitive glutamate receptor antagonists. In addition, stimulations of 45Ca2+ uptake by InsP6 and glutamate were additive. These data provide evidence that InsP6 directly activates a specific population of neurons in the CNS.
肌醇六磷酸（InsP6）可增加培养的小脑颗粒细胞对45Ca2+的摄取。这种增加呈浓度依赖性（半数有效浓度[EC50]=20微摩尔），动力学缓慢，且在细胞培养成熟5天后出现。InsP6还可增强体外培养11 - 12天的小脑颗粒细胞中D-[3H]天冬氨酸的释放。肌醇五磷酸也能刺激45Ca2+摄取，但肌醇1,3,4,5 - 四磷酸则无此作用。InsP6诱导的45Ca2+内流增加不依赖于细胞外Na+，且仅被有机钙通道阻滞剂硝苯地平部分抑制。InsP6的内在作用不受竞争性或非竞争性谷氨酸受体拮抗剂的影响。此外，InsP6和谷氨酸对45Ca2+摄取的刺激作用具有相加性。这些数据表明InsP6可直接激活中枢神经系统中的特定神经元群体。
