Mintz I M, Sabatini B L, Regehr W G
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Neuron. 1995 Sep;15(3):675-88. doi: 10.1016/0896-6273(95)90155-8.
The manner in which presynaptic Ca2+ influx controls the release of neurotransmitter was investigated at the granule cell to Purkinje cell synapse in rat cerebellar slices. Excitatory postsynaptic currents were measured using whole-cell voltage clamp, and changes in presynaptic Ca2+ influx were determined with the Ca(2+)-sensitive dye furaptra. We manipulated presynaptic Ca2+ entry by altering external Ca2+ levels and by blocking Ca2+ channels with Cd2+ or with the toxins omega-conotoxin GVIA and omega-Aga-IVA. For all of the manipulations, other than the application of omega-Aga-IVA, the relationship between Ca2+ influx and release was well approximated by a power law, n approximately 2.5. When omega-Aga-IVA was applied, release appeared to be more steeply dependent on Ca2+ (n approximately 4), suggesting that omega-Aga-IVA-sensitive channels are more effective at triggering release. Based on interactive effects of toxins on synaptic currents, we conclude that multiple types of Ca2+ channels synergistically control individual release sites.
在大鼠小脑切片的颗粒细胞与浦肯野细胞突触处，研究了突触前Ca2+内流控制神经递质释放的方式。使用全细胞膜片钳记录兴奋性突触后电流，并用Ca(2+)敏感染料fura-ptra测定突触前Ca2+内流的变化。我们通过改变细胞外Ca2+水平以及用Cd2+或毒素ω-芋螺毒素GVIA和ω-银环蛇毒素IVA阻断Ca2+通道来操纵突触前Ca2+内流。对于所有这些操作，除了应用ω-银环蛇毒素IVA外，Ca2+内流与释放之间的关系可用幂律很好地近似，n约为2.5。当应用ω-银环蛇毒素IVA时，释放似乎对Ca2+的依赖性更强（n约为4），这表明ω-银环蛇毒素IVA敏感通道在触发释放方面更有效。基于毒素对突触电流的相互作用效应，我们得出结论，多种类型的Ca2+通道协同控制单个释放位点。
