Development of membrane conductance improves coincidence detection in the nucleus laminaris of the chicken
Development of membrane conductance improves coincidence detection in the nucleus laminaris of the chicken
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DOI：
10.1113/jphysiol.2001.013365
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发表时间：
2002-04-15
影响因子：
5.5
通讯作者：
Ohmori, H
中科院分区：
文献类型：
--
作者：
Kuba, H;Koyano, K;Ohmori, H
切片制剂提高了鸡胚（胚期(E) 16 ~ 17）和雏鸡（孵化后(P) 2 ~ 7）层状核（NL）重合检测。电刺激以不同的间隔施加在两侧的NL投射纤维上。采用电刺激的时间间隔导致半最大放电概率的响应窗口作为重合检测的度量，小鸡（1.4英寸）比胚胎（3.9英寸）窄。两种年龄的NL神经元的膜时间常数从18.4 ms降低到3.2 ms，膜电导增加了5倍，而输入电容没有变化。诱导的EPSCs在雏鸡体内的衰变速度略快，而微型EPSCs的大小和时间进程不变。与胚胎相比，小鸡的动作电位阈值更低，超极化后动作电位更大。在两个年龄阶段，Dendrotoxin-I均能使细胞去极化并显著增加其输入电阻，消除后超极化，延迟动作电位的衰减阶段，提示低阈值K+通道的表达。Cs+使细胞超极化，增加了输入电阻，消除了超极化过程中的凹陷，而Ba2+和TEA对超极化凹陷没有影响。这些数据表明了超极化激活阳离子通道的表达。在这两个时期，低阈值K+通道的最大电导增加了4倍，达到约16 nS，超极化激活通道的最大电导增加了6倍，达到约10 nS。由于这些电导的增加，一致性检测的改进与EPSP时间过程的加速相关。
Coincidence detection at the nucleus laminaris (NL) of a chicken was improved between embryos (embryonic days (E) 16 and 17) and chicks (post-hatch days (P) 2-7) in slice preparations. Electrical stimuli were applied bilaterally to the projection fibres to the NL at various intervals. The response window corresponding to the temporal separation of electrical stimuli that resulted in half-maximal firing probability was adopted as the measure of coincidence detection, and was narrower in chicks (1.4 ins) than in embryos (3.9 ins). Between these two ages, the membrane time constant of NL neurons was reduced from 18.4 to 3.2 ms and the membrane conductance was increased 5-fold, while no difference was measured in the input capacitance. Evoked EPSCs decayed slightly faster in chicks, while the size and the time course of miniature EPSCs were unchanged. Action potentials had lower thresholds and larger after-hyperpolarization in chicks than in embryos. Dendrotoxin-I depolarized cells and increased their input resistance significantly at both ages, eliminated the after-hyperpolarization, and delayed the decay phase of action potentials, indicative of the expression of low-threshold K+ channels. Cs+ hyperpolarized the cells, increased the input resistance and eliminated sags during hyperpolarization at both ages, while the hyperpolarization sag was affected by neither Ba2+ nor TEA. These data indicate the expression of hyperpolarization-activated cation channels. Between these two ages, the maximum conductance of low-threshold K+ channels increased 4-fold to about 16 nS, and hyperpolarization-activated channels increased 6-fold to about 10 nS. Improvement of coincidence detection correlated with the acceleration of the EPSP time course as a result of the increase of these conductances.