Development of Theta Rhythmicity in Entorhinal Stellate Cells of the Juvenile Rat
Development of Theta Rhythmicity in Entorhinal Stellate Cells of the Juvenile Rat
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DOI：
10.1152/jn.90424.2008
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发表时间：
2008-12-01
影响因子：
2.5
通讯作者：
White, John A.
中科院分区：
文献类型：
--
作者：
Burton, Brian G.;Economo, Michael N.;White, John A.
大鼠内侧内嗅皮质（EC）第II层的成熟星状细胞在体外以θ频率（4-12 Hz）表现出阈下膜电位振荡（MPO）。我们发现MPO出现在出生后14天（P14）和18天（P18）之间，但到28天+（P28-P32）时几乎没有进一步的变化。为了确定相关因素，我们研究了发育中的星状细胞的电反应，注意两个被认为是成熟振荡所必需的电流：h电流I-h，它提供了共振所需的缓慢整流;和持续的钠电流I-NaP，它提供了共振的放大。对注入电流的反应显示，P14细胞通常是非共振的，具有相对较高的电阻。从P14到P18，I-h和I-NaP的密度都增加了约50%。然而，I-h水平下降到P28+的中间值。考虑到I-h表达的非稳健趋势和先前证明的甚至低水平I-h维持振荡的效力，我们建议共振和MPO在P14时受到低水平I-NaP的限制多于I-h。I-NaP对MPO发展的相对重要性得到了基于电导模型的模拟的支持，该模型还表明，一般的分流电导可能会影响MPO出现的确切年龄。除了我们的生理学研究，我们分析了P14，P18和P28+的棘密度，发现整个时期都有强烈的突触发生。我们的数据预测，海马网络中依赖θ节律的功能至少在P18之前是有限的。
Mature stellate cells of the rat medial entorhinal cortex (EC), layer II, exhibit subthreshold membrane potential oscillations (MPOs) at theta frequencies (4-12 Hz) in vitro. We find that MPOs appear between postnatal days 14 (P14) and 18 (P18) but show little further change by day 28+ (P28-P32). To identify the factors responsible, we examined the electrical responses of developing stellate cells, paying attention to two currents thought necessary for mature oscillation: the h current I-h, which provides the slow rectification required for resonance; and a persistent sodium current I-NaP, which provides amplification of resonance. Responses to injected current revealed that P14 cells were often nonresonant with a relatively high resistance. Densities of I-h and I-NaP both rose by about 50% from P14 to P18. However, I-h levels fell to intermediate values by P28+. Given the nonrobust trend in I-h expression and a previously demonstrated potency of even low levels of I-h to sustain oscillation, we propose that resonance and MPOs are limited at P14 more by low levels of I-NaP than of I-h. The relative importance of I-NaP for the development of MPOs is supported by simulations of a conductance-based model, which also suggest that general shunt conductance may influence the precise age when MPOs appear. In addition to our physiological study, we analyzed spine densities at P14, P18, and P28+ and found a vigorous synaptogenesis across the whole period. Our data predict that functions that rely on theta rhythmicity in the hippocampal network are limited until at least P18.