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在许多生物体的早期发育过程中，动作电位实际上最初是由钙电流而不是钠电流携带的。发育过程中钙离子通道的开闭动力学比电压门控钠离子通道的开闭动力学要慢，而电压门控钠离子通道是成熟神经元的动作电位。钙离子通道的开放时间越长，动作电位的速度就会比成熟神经元慢得多<ref name=":0" /> 。非洲爪蟾（Xenopus）神经元最初的动作电位需要 60-90 毫秒。在发育过程中，这个时间减少到 1 毫秒。这种急剧下降有两个原因。首先，向内的电流主要由钠离子通道输送 <ref name=":9">{{Cite book|title=Calcium Channels: Their Properties, Functions, Regulation, and Clinical relevance|last=Partridge|first=Donald | name-list-style = vanc |publisher=CRC Press|year=1991|isbn=9780849388071|pages=138–142}}</ref> 。其次，延迟整流器——一种钾离子通道电流——增加到最初强度的 3.5 倍 <ref name=":0" /> 。

在许多生物体的早期发育过程中，动作电位实际上最初是由钙电流而不是钠电流携带的。发育过程中钙离子通道的开闭动力学比电压门控钠离子通道的开闭动力学要慢，而电压门控钠离子通道是成熟神经元的动作电位。钙离子通道的开放时间越长，动作电位的速度就会比成熟神经元慢得多<ref name=":0" /> 。非洲爪蟾（Xenopus）神经元最初的动作电位需要 60-90 毫秒。在发育过程中，这个时间减少到 1 毫秒。这种急剧下降有两个原因。首先，向内的电流主要由钠离子通道输送 <ref name=":9">{{Cite book|title=Calcium Channels: Their Properties, Functions, Regulation, and Clinical relevance|last=Partridge|first=Donald | name-list-style = vanc |publisher=CRC Press|year=1991|isbn=9780849388071|pages=138–142}}</ref> 。其次，延迟整流器——一种钾离子通道电流——增加到最初强度的 3.5 倍 <ref name=":0" /> 。

In order for the transition from a calcium-dependent action potential to a sodium-dependent action potential to proceed new channels must be added to the membrane. If Xenopus neurons are grown in an environment with [[Transcription (biology)|RNA synthesis]] or [[Translation (biology)|protein synthesis]] inhibitors that transition is prevented.<ref name=":10">{{Cite book|url=https://www.springer.com/us/book/9780306415500|title=Cellular and Molecular Biology of Neuronal Development {{!}} Ira Black {{!}} Springer|last=Black|first=Ira | name-list-style = vanc |publisher=Springer|year=1984|isbn=978-1-4613-2717-2|pages=103|language=en|url-status=live|archive-url=https://web.archive.org/web/20170717154858/http://www.springer.com/us/book/9780306415500|archive-date=17 July 2017|df=dmy-all}}</ref> Even the electrical activity of the cell itself may play a role in channel expression. If action potentials in Xenopus [[myocyte]]s are blocked, the typical increase in sodium and potassium current density is prevented or delayed.<ref name=":11">{{Cite book|title=Current Topics in Developmental Biology, Volume 39|last=Pedersen|first=Roger | name-list-style = vanc |publisher=Elsevier Academic Press|year=1998|isbn=9780080584621|url=https://archive.org/details/currenttopicsind0000unse_x6e1}}</ref>

为了使钙离子依赖的动作电位转变为钠离子依赖的动作电位，膜上必须增加新的通道。如果非洲爪蟾神经元生长在有 RNA 合成抑制剂或蛋白质合成抑制剂的环境中，这种转变就被阻止了 <ref name=":10">{{Cite book|url=https://www.springer.com/us/book/9780306415500|title=Cellular and Molecular Biology of Neuronal Development {{!}} Ira Black {{!}} Springer|last=Black|first=Ira | name-list-style = vanc |publisher=Springer|year=1984|isbn=978-1-4613-2717-2|pages=103|language=en|url-status=live|archive-url=https://web.archive.org/web/20170717154858/http://www.springer.com/us/book/9780306415500|archive-date=17 July 2017|df=dmy-all}}</ref>。甚至细胞本身的电活动也可能在通道的表达中发挥作用。如果阻断非洲爪蟾心肌细胞的动作电位，通常发生的钠和钾电流密度增加就会被阻止或延迟 <ref name=":11">{{Cite book|title=Current Topics in Developmental Biology, Volume 39|last=Pedersen|first=Roger | name-list-style = vanc |publisher=Elsevier Academic Press|year=1998|isbn=9780080584621|url=https://archive.org/details/currenttopicsind0000unse_x6e1}}</ref>。

在不同物种中都可观察到这种电特性的成熟过程。非洲爪蟾的钠和钾电流在神经元进入有丝分裂的最后时相后急剧增加。大鼠大脑皮层神经元的钠电流密度在刚出生的 2 周内增加 600% <ref name=":0" />。

 

This maturation of electrical properties is seen across species. Xenopus sodium and potassium currents increase drastically after a neuron goes through its final phase of [[mitosis]]. The sodium current density of rat [[Cerebral cortex|cortical neurons]] increases by 600% within the first two postnatal weeks.<ref name=":0" />

 

这种电特性的成熟可以在不同物种间观察到。非洲爪蟾的钠和钾电流在神经元进入有丝分裂的最后阶段后急剧增加。大鼠大脑皮层神经元的钠电流密度在出生后第2周内增加了600% .<ref name=":0" />。

==Neurotransmission神经传递==

==Neurotransmission神经传递==