TAP Wu-Cheng~1,CUI Ji-Hong~1,GUO Xu,LI Yi,CAI Yijun,HU Wen,CHEN Yan,XIANG Hui~(1,*) From School of Life Sciences,Sun Yat-sen(Zhongshan)University,Guangzhou,510275,China
<正>The maturation of interneurons and pyramidal cells is crucial for the construction of cortical neuronal network.Despite its physiological importance,the underlying mechanisms of this developmental process are poorly understood.In this study,we characterized the electrophysiological properties of immature(P≤13)and older(P≥20)necortical somatostatin(SS)marked interneurons and pyramidal cells from transgenic mice using whole-cell patch clamp techniques.We focused on SS-interneurons and pyramidal cells in layer ofⅡtoⅤof the neocortex. With increasing age,while RMPs of pyramidal cells increased,no significant change was found in SS-interneurons; compared with SS-interneurons,pyramidal cells had larger RMPs in both P≤13 and P≥20 group.Also,SS-interneurons exhibited the decrease of cell capacitance and membrane time constant(tau)with the increase of age,and these values at P≥20 were significant smaller than that of pyramidal cells.Under the current clamp condition,peak amplitude and the frequency of action potential increased with age in SS-interneurons,whereas no significant alteration was found in pyramidal cells at P≥20;pyramidal cells had larger peak amplitude than SS-interneurons,no significant difference was found between pyramidal cells and interneurons at P≤13.Compared with pyramidal cells,the frequency of action potential of SS-interneurons at P≤13 and P≥20 were higher.Rise-time,interval time and duration of both categories of neurons decreased with age.Compared with SS-interneurons,interval time (P≥20)and duration(P≥20,P≤13)of pyramidal cells were larger.In the experiment of voltage clamp,the peak amplitude of sodium current increased from P≤13 to P≥20 in pyramidal cells.In kinetic study,rise time at -35 mV and the decay time of pyramidal cells reduced with age.In the study of synaptic properties,the amplitude and decay time of EPSC in both SS-interneurons and pyramidal cells increased with age,and at the stage of P≥20,pyramidal cells had smaller decay time than SS-interneurons.No significant difference of the amplitude of IPSC in pyramidal cells was found between two age groups,whereas at the stage of P≤13,pyramidal cells had higher amplitude than that of SS-interneurons.The decay time of IPSC in pyramidal cells decreased with age,and pyramidal cells had longer decay time at the stage of P≤13 than SS-interneurons.Combining with the result that STP of EPSCs switched from depression to facilitation,while the STP of IPSCs showed depression,we propose that a codevelopmental changes of intrinsic and synaptic properties of SS-interneurons and pyramidal neurons in neocortex occurred during early life.
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