Neurotransmitters acting via different G proteins inhibit N-type calcium current by an identical mechanism in rat sympathetic neurons
Neurotransmitters acting via different G proteins inhibit N-type calcium current by an identical mechanism in rat sympathetic neurons
复制标题
DOI：
10.1152/jn.1995.74.6.2251
复制
发表时间：
1995-12-01
影响因子：
2.5
通讯作者：
Elmslie, KS
中科院分区：
文献类型：
--
作者：
Ehrlich, I;Elmslie, KS
1.采用全细胞膜片钳技术研究去甲肾上腺素(NE)和血管活性肠肽(VIP)对成年大鼠颈上神经节(SCG)神经元N型钙电流的电压依赖性抑制机制。抑制作用的电压依赖性表现为强去极化逆转抑制作用。我们测试了一种假设，即这种电压依赖是由于G蛋白与钙通道结合的破坏造成的。根据这一假说，当活性G蛋白浓度较高时，去极化后钙电流再抑制的动力学过程应该会变得更快。假设活性G蛋白浓度越高，抑制越大，我们使用不同浓度的NE来改变抑制的幅度，从而改变活性G蛋白的浓度。我们发现，在去极化脉冲至+80 mV后，在-80 mV处的再抑制动力学对于较大的抑制更快。血管活性肠肽通过一种与去甲肾上腺素(G(O))不同的G蛋白(G(S))引起N-电流的电压依赖性抑制。我们发现，VIP对再抑制动力学的影响与NE.5的相同。去甲肾上腺素和血管活性肠肽联合应用不能显着增加抑制幅度，但可显着增加再抑制率。因此，去甲肾上腺素加血管活性肠肽似乎大大增加了与通道结合的分子的浓度(根据假设是G蛋白)。在强去极化(阶跃至+80 mV)时，钙电流去抑制动力学不随去甲肾上腺素、血管活性肠肽或去甲肾上腺素和血管活性肠肽联合应用的抑制程度而改变。浓度依赖性再抑制动力学和非浓度非依赖性再抑制动力学均符合活性G蛋白直接与N型钙通道结合调节交感神经元活性的假说。
1. We studied the mechanism of voltage-dependent inhibition of N-type calcium current by norepinephrine (NE) and vasoactive intestinal peptide (VIP) in adult rat superior cervical ganglion (SCG) neurons using the whole cell patch-clamp technique.2. The voltage dependence of inhibition is manifest in the reversal of inhibition by strong depolarization. We tested the hypothesis that this voltage dependence results from disruption of G proteins binding to calcium channels. According to this hypothesis, the kinetics of calcium current reinhibition following a strong depolarization should become faster for higher concentrations of active G proteins.3. Assuming that larger inhibitions result from higher concentrations of active G proteins, we used different concentrations of NE to alter the amplitude of inhibition and, thus, the active G protein concentration. We found that the kinetics of reinhibition at -80 mV following a depolarizing pulse to +80 mV were faster for larger inhibitions.4. VIP induces voltage-dependent inhibition of N-current via a different G protein (G(s)) than that of NE (G(o)). We found that the effect of VIP on reinhibition kinetics was identical to that produced by NE.5. Combined application of NE and VIP did not greatly increase the amplitude of the inhibition but significantly increased the rate of reinhibition. Thus NE plus VIP appear to greatly increase the concentration of the molecule binding to the channel (G protein according to the hypothesis).6. The kinetics of calcium current disinhibition during strong depolarization (step to +80 mV) did not change with the size of the inhibition induced by NE, VIP or application of NE and VIP together.7. Both the concentration-dependent reinhibition kinetics and concentration-independent disinhibition kinetics are consistent with the hypothesis that active G proteins bind directly to N-type calcium channels to modulate their activity in rat sympathetic neurons.