Gasparini S, Kasyanov A M, Pietrobon D, Voronin L L, Cherubini E
Neuroscience Program and Istituto Nazionale Fisica della Materia Unit, International School for Advanced Studies, 34014 Trieste, Italy.
J Neurosci. 2001 Nov 15;21(22):8715-21. doi: 10.1523/JNEUROSCI.21-22-08715.2001.
The possibility that R-type calcium channels contribute to fast glutamatergic transmission in the hippocampus has been assessed using low concentrations of NiCl(2) and the peptide toxin SNX 482, a selective antagonist of the pore-forming alpha(1E) subunit of R-type calcium channel. EPSPs or EPSCs were recorded in the whole-cell configuration of the patch-clamp technique mainly from CA3 hippocampal neurons. Effects of both NiCl(2) and SNX 482 were tested on large (composite) EPSCs evoked by mossy and associative-commissural fiber stimulation. NiCl(2) effects were also tested on minimal EPSPs-EPSCs. Both substances reduced the amplitude of EPSPs-EPSCs. This effect was associated with an increase in the number of response failures of minimal EPSPs-EPSCs, an enhancement of the paired-pulse facilitation ratios of both minimal and composite EPSCs, and a reduction of the inverse squared coefficient of variation (CV(-2)). The reduction of CV(-2) was positively correlated with the decrease in EPSC amplitude. The inhibitory effect of NiCl(2) was occluded by SNX 482 but not by omega-conotoxin-MVIIC, a broad-spectrum antagonist thought to interact with N- and P/Q-type calcium channels, supporting a specific action of low concentrations of NiCl(2) on R-type calcium channels. Together, these observations indicate that both NiCl(2) and SNX 482 act at presynaptic sites and block R-type calcium channels with pharmacological properties similar to those encoded by the alpha(1E) gene. These channels are involved in fast glutamatergic transmission at hippocampal synapses.
使用低浓度的NiCl₂和肽毒素SNX 482（R型钙通道孔形成α₁E亚基的选择性拮抗剂）评估了R型钙通道在海马体快速谷氨酸能传递中的作用。主要从海马CA3神经元，采用膜片钳技术的全细胞模式记录兴奋性突触后电位（EPSP）或兴奋性突触后电流（EPSC）。测试了NiCl₂和SNX 482对苔藓纤维和联合连合纤维刺激诱发的大（复合）EPSC的影响。也测试了NiCl₂对最小EPSP-EPSC的影响。两种物质均降低了EPSP-EPSC的幅度。这种作用与最小EPSP-EPSC反应失败次数增加、最小和复合EPSC的双脉冲易化率增强以及变异系数平方倒数（CV⁻²）降低有关。CV⁻²的降低与EPSC幅度的减小呈正相关。NiCl₂的抑制作用被SNX 482阻断，但未被ω-芋螺毒素-MVIIC阻断，ω-芋螺毒素-MVIIC是一种广谱拮抗剂，被认为与N型和P/Q型钙通道相互作用，这支持了低浓度NiCl₂对R型钙通道的特异性作用。总之，这些观察结果表明，NiCl₂和SNX 482均作用于突触前位点，并阻断具有与α₁E基因编码的药理学特性相似的R型钙通道。这些通道参与海马突触的快速谷氨酸能传递。
