Jaffe E H, Marty A, Schulte A, Chow R H
Division of Molecular Biology of Neuronal Signaling, Max-Planck-Institut für Experimentelle Medizin, Göttingen, Germany D-37075, USA.
J Neurosci. 1998 May 15;18(10):3548-53. doi: 10.1523/JNEUROSCI.18-10-03548.1998.
Substantia nigra neurons release dopamine from their somatodendritic regions. A long-unresolved question is whether this release occurs by exocytosis or by a nonvesicular mechanism. We used carbon fiber microelectrodes in a brainstem slice to assay secretion from single cell bodies that had been cleared of connective tissue. Amperometry at the carbon fiber microelectrodes revealed unitary events in approximately 90% of cells in resting conditions. These events had charge integrals ranging from a few femtocoulombs to several hundred femtocoulombs (fC). Local glutamate application enhanced the event frequency by 3.5-fold on average and up to 10-fold in highly responsive cells, although the mean charge integral was not modified. Local application of a high K+-containing saline had effects similar to those of glutamate. The frequency of resting and stimulated amperometric events was much lower at 21-22 degreesC than at 32-35 degreesC. The addition of Cd2+ (50 microM), a blocker of voltage-dependent Ca2+ channels, to the bath solution blocked the stimulatory effects of glutamate. These results suggest that dopamine is released from the somata of substantia nigra neurons by exocytosis and that this mechanism is regulated by neuronal electrical activity. More generally, this study demonstrates the applicability of carbon fiber microelectrodes to the measurement of quantal monoamine secretion in brain slices.
黑质神经元从其胞体树突区域释放多巴胺。一个长期未解决的问题是，这种释放是通过胞吐作用还是通过非囊泡机制发生的。我们在脑干切片中使用碳纤维微电极来检测已清除结缔组织的单个细胞体的分泌情况。在碳纤维微电极上进行的安培测量显示，在静息状态下，约90%的细胞出现单一事件。这些事件的电荷积分范围从几飞库仑到几百飞库仑（fC）。局部应用谷氨酸平均使事件频率提高3.5倍，在高反应性细胞中高达10倍，尽管平均电荷积分未改变。局部应用含高钾的盐溶液具有与谷氨酸类似的作用。在21 - 22摄氏度时，静息和刺激状态下的安培测量事件频率远低于32 - 35摄氏度时的频率。向浴液中添加电压依赖性钙通道阻滞剂Cd2 +（50 microM）可阻断谷氨酸的刺激作用。这些结果表明，多巴胺通过胞吐作用从黑质神经元的胞体释放，并且该机制受神经元电活动调节。更普遍地说，这项研究证明了碳纤维微电极在测量脑切片中量子化单胺分泌方面的适用性。
