Electrophysiological and molecular evidence of L-(Cav1), N- (Cav2.2), and R- (Cav2.3) type Ca2+ channels in rat cortical astrocytes
Electrophysiological and molecular evidence of L-(Cav1), N- (Cav2.2), and R- (Cav2.3) type Ca2+ channels in rat cortical astrocytes
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作者：
D'ascenzo, M;Vairano, M;Grassi, C
细胞内Ca 2+水平的变化是神经元-胶质细胞串扰的一个重要信号，但人们对电压门控Ca 2+通道（VGCCs）在控制胶质细胞Ca 2+内流中可能发挥的作用知之甚少。我们在培养的大鼠皮质星形胶质细胞中研究了VGCC的药理学和生物物理学特征。在全细胞膜片钳实验中，L-通道阻断剂（5 μ M硝苯地平）使Ba 2+电流幅度降低了28%，N-通道阻断剂（3 μ M ω-芋螺毒素-GVIA）使Ba 2+电流幅度进一步降低（32%）。在P/Q通道阻断（3 μ M ω-芋螺毒素-MVIIC）后没有观察到显著的额外变化。残余电流（对照组的36%）与R通道阻断（100 nM SNX-482）消除的百分比（34%）大致相同。L、N和R通道的电生理学证据与VGCC亚基α（1C）（L型）、α（1B）（N型）和α（1 E）（R型）的mRNA转录物的RT-PCR检测相关。在细胞贴附记录中，单通道特性（L-电流：振幅，10 mV时为-1.21 +/- 0.02 pA;斜率电导，22.0 +/- 1.1 pS;平均开放时间，5.95 +/- 0.24 ms; N-电流：振幅，10 mV时为-1.09 +/- 0.02 pA;斜率电导，18.0 +/- 1.1 pS;平均开放时间，1.14 +/- 0.02 ms; R-电流：振幅，-0.81 +/- 0.01 pA（20 mV）;斜率电导，10.5 +/- 0.3 pS;平均开放时间，0.88 +/- 0.02 ms）与神经元中相应的VGCC相似。这些新的发现表明，皮质星形胶质细胞的VGCC表达可能比以前认为的更多样化，这表明这些通道可能确实在星形胶质细胞Ca 2+内流的调节中发挥重要作用，从而影响神经元-胶质细胞的串扰和许多其他钙介导的胶质细胞功能。(C)2003 Wiley-Liss，Inc.
Changes in intracellular Ca2+ levels are an important signal underlying neuron-glia cross-talk, but little is known about the possible role of voltage-gated Ca2+ channels (VGCCs) in controlling glial cell Ca2+ influx. We investigated the pharmacological and biophysical features of VGCCs in cultured rat cortical astrocytes. In whole-cell patchclamp experiments, L-channel blockade (5 muM nifedipine) reduced Ba2+ current amplitude by 28% of controls, and further decrease (32%) was produced by N-channel blockade (3 muM omega-conotoxin-GVIA). No significant additional changes were observed after P/Q channel blockade (3 muM omega-conotoxin-MVIIC). Residual current (36% of controls) amounted to roughly the same percentage (34%) that was abolished by R-channel blockade (100 nM SNX-482). Electrophysiological evidence of L-, N-, and R-channels was associated with RT-PCR detection of mRNA transcripts for VGCC subunits alpha(1C) (L-type), alpha(1B) (N-type), and alpha(1E) (R-type). In cell-attached recordings, single-channel properties (L-currents: amplitude, -1.21 +/- 0.02 pA at 10 mV; slope conductance, 22.0 +/- 1.1 pS; mean open time, 5.95 +/- 0.24 ms; N-currents: amplitude, -1.09 +/- 0.02 pA at 10 mV; slope conductance, 18.0 +/- 1.1 pS; mean open time, 1.14 +/- 0.02 ms; R-currents: amplitude, -0.81 +/- 0.01 pA at 20 mV; slope conductance, 10.5 +/- 0.3 pS; mean open time, 0.88 +/- 0.02 ms) resembled those of corresponding VGCCs in neurons. These novel findings indicate that VGCC expression by cortical astrocytes may be more varied than previously thought, suggesting that these channels may indeed play substantial roles in the regulation of astrocyte Ca2+ influx, which influences neuron-glia cross-talk and numerous other calcium-mediated glial-cell functions. (C) 2003 Wiley-Liss, Inc.