Effects Of Zinc Ions On Excitability Of Superficial Neurons In The Mec Of Mice

Zinc is essential trace element for human body,which participates i n a variety of biochemical reactions in the organism.Zinc ions released by synaptic vesicles in the nervous system can regulate information transmission and synaptic plasticity between neurons.Special zinc modules were found in the second layer of the me dial entorhinal cortex of rats,and zinc modules and calcium binding protein positive cell(CB)patches were complementary in spatial location.MEC is located next to the hippocampus,and there are a variety of place cells that participate in and regulate spatial cognition,such as grid cells,head direction cells,border cells and speed cells.Among them,grid cells are located in the second layer of MEC,and most of them are stellate cells(SCs).Different grid modules are clustered and separated by pyramidal cell plaques,while zinc modules and CB patches complement each other,suggesting the characteristics of the location and function of zinc modules.In this study,we explored for the first time whether there is a special modular structure in the superficial layer of mouse MEC;zinc ion chelating agent was used to control the concentration of zinc ion,and the electrophysiological platform was used to detect the effects of zinc ion on ionic glutamate receptor AMPA-R and NMDA-R excitatory postsynaptic current(EPSC)in MEC superficial neurons.In short,the purpose of the whole experiment is to study the role of zinc ions in the basic synaptic transmission of MEC superficial neurons.EPSCs were obtained by stimulating electrodes,and pure AMPA-EPSCs or NMDA-EPSCs were isolated by adding different nerve inhibitors.The zinc ion concentration in circulating liquid was controlled by zinc ion chelator ZX1.The experimental results show that ZX1 can significantly increase the recorded AMPA-EPSCs and NMDA-EPSCs,that is,ZX1 reduces the concentration of zinc ions in the circulating solution through chelation,relieves the inhibition of zinc ions on AMPA-R and NMDA-R,thence increases EPSC.We also recorded the paired-pulse ratio(PPR),which reflects the short-term plasticity of synapses,and the results show that ZX1 does not change PPR,indicating that zinc ions do not affect synaptic short-term plasticity.In addition,we recorded the miniature excitatory postsynaptic currents(m EPSC)of MECL3 neurons,which ca n reflect some of the electrophysiological properties of MECL3 neurons.The results showed that ZX1 have no significant effect on m EPSC.Finally,by morphologically reconstructing the recorded neurons,we can distinguish the types of neurons.This is the first time to study the effect of zinc ion on the basic synaptic transmission of neurons in the MEC of mice,which is basically consistent with the previous findings in the hippocampus : zinc ions inhibit the basic synaptic transmission of neurons by inhibiting the opening of AMPA receptor and NMDA receptor.