Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
Sci Rep. 2017 Feb 17;7:42897. doi: 10.1038/srep42897.
Artificial cerebrospinal fluid (ACSF), i.e., brain extracellular medium, which includes Ca and Mg, but not other divalent cations such as Zn, has been used for in vitro and in vivo experiments. The present study deals with the physiological significance of extracellular Zn in ACSF. Spontaneous presynaptic activity is suppressed in the stratum lucidum of brain slices from young rats bathed in ACSF containing 10 nM ZnCl, indicating that extracellular Zn modifies hippocampal presynaptic activity. To examine the in vivo action of 10 nM ZnCl on long-term potentiation (LTP), the recording region was perfused using a recording electrode attached to a microdialysis probe. The magnitude of LTP was not modified in young rats by perfusion with ACSF containing 10 nM ZnCl, compared to perfusion with ACSF without Zn, but attenuated by perfusion with ACSF containing 100 nM ZnCl. Interestingly, the magnitude of LTP was not modified in aged rats even by perfusion with ACSF containing 100 nM ZnCl, but enhanced by perfusion with ACSF containing 10 mM CaEDTA, an extracellular Zn chelator. The present study indicates that the basal levels of extracellular Zn, which are in the range of low nanomolar concentrations, are critical for synaptic activity and perhaps increased age-dependently.
人工脑脊液（ACSF），即脑细胞外液，其中包含 Ca 和 Mg，但不包含其他二价阳离子，如 Zn，已被用于体外和体内实验。本研究探讨了细胞外液 Zn 对 ACSF 的生理意义。在含有 10 nM ZnCl 的 ACSF 中孵育的年轻大鼠脑片的 lucidum 层中，自发性突触前活动受到抑制，表明细胞外液 Zn 调节海马突触前活动。为了研究 10 nM ZnCl 在长时程增强（LTP）中的体内作用，使用与微透析探针相连的记录电极对记录区域进行灌流。与不含 Zn 的 ACSF 灌流相比，含有 10 nM ZnCl 的 ACSF 灌流并未改变年轻大鼠的 LTP 幅度，但含有 100 nM ZnCl 的 ACSF 灌流则减弱了 LTP 幅度。有趣的是，即使含有 100 nM ZnCl 的 ACSF 灌流也不会改变老年大鼠的 LTP 幅度，但含有 10 mM CaEDTA（一种细胞外 Zn 螯合剂）的 ACSF 灌流增强了 LTP 幅度。本研究表明，细胞外液 Zn 的基础水平，处于低纳摩尔浓度范围内，对突触活动至关重要，并且可能随年龄的增长而增加。
