Quinta-Ferreira M E, Matias C M
Department of Physics and Center for Neurosciences of Coimbra, University of Coimbra, 3004-516 Coimbra, Portugal.
Brain Res. 2005 Jun 14;1047(1):1-9. doi: 10.1016/j.brainres.2005.04.006.
At the zinc-enriched mossy fiber synapses from hippocampal CA3 area, electrical or chemical stimulation evokes zinc release from glutamatergic synaptic vesicles that may cause different pre- or postsynaptic actions. Besides zinc that can be co-localized with glutamate and GABA, the mossy fibers contain a very high density of ATP-sensitive potassium channels that are activated by zinc. We have investigated the possibility that intensely released zinc inhibits presynaptic calcium changes and consequently zinc and glutamate release. The studies were made combining optical recording of fast presynaptic calcium and zinc signals, using the fluorescent indicators Fura-2 and N-(6-methoxy-8-quinolyl)-para-toluenesulfonamide, respectively, with measurements of field potentials. We have observed that strong tetanic stimulation caused posttetanic depressions of electrically induced presynaptic calcium and zinc signals and of synaptic responses, the depressions being blocked by zinc chelators. These results suggest that endogenously released zinc has an inhibitory role, mediated by presynaptic ATP-sensitive potassium channels and/or presynaptic calcium channels, that leads to the depression of zinc and glutamate release.
在来自海马体CA3区富含锌的苔藓纤维突触处，电刺激或化学刺激会引发锌从谷氨酸能突触小泡中释放，这可能会导致不同的突触前或突触后作用。除了可与谷氨酸和γ-氨基丁酸共定位的锌外，苔藓纤维还含有高密度的对ATP敏感的钾通道，这些通道可被锌激活。我们研究了大量释放的锌抑制突触前钙变化并进而抑制锌和谷氨酸释放的可能性。研究结合了分别使用荧光指示剂Fura-2和N-(6-甲氧基-8-喹啉基)-对甲苯磺酰胺对突触前快速钙和锌信号进行光学记录以及对场电位的测量。我们观察到，强烈的强直刺激会导致电诱导的突触前钙和锌信号以及突触反应的强直后抑制，而锌螯合剂可阻断这种抑制。这些结果表明，内源性释放的锌具有抑制作用，由突触前对ATP敏感的钾通道和/或突触前钙通道介导，导致锌和谷氨酸释放的抑制。
