Selective Gating of Neuronal Activity by Intrinsic Properties in Distinct Motor Rhythms
Selective Gating of Neuronal Activity by Intrinsic Properties in Distinct Motor Rhythms
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DOI：
10.1523/jneurosci.0323-15.2015
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发表时间：
2015-07
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通讯作者：
Wen-Chang Li
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作者：
Wen-Chang Li
许多神经回路在改变感觉或调节输入后表现出快速重构，以产生定型输出。在非洲爪蟾蝌蚪的电机电路中，我研究了某些电压依赖性离子电流如何影响发射阈值，并有助于电路重构，以产生两种不同的电机模式，游泳和挣扎。兴奋性中间神经元的放电阈值[即，游泳中枢模式发生器中的下行中间神经元（dIN）]由于Na+电流的失活而通过去极化而升高。相反，在游泳或挣扎中活跃的其他类型的神经元的阈值通过来自快速瞬时K+电流激活的超极化而升高。然后将放电阈值与兴奋性突触驱动进行比较，兴奋性突触驱动通过在游泳和挣扎期间使用QX 314在细胞内阻断动作电位来揭示。在游泳过程中，瞬时K+电流降低神经元的兴奋性并以弱兴奋关闭神经元，而其他神经元中的强兴奋使其失活增加兴奋性并使快速突触电位能够驱动可靠的放电。在挣扎过程中，持续的感觉输入会导致高水平的网络兴奋。这使得Na+电流失活和dIN活性抑制，同时失活瞬时K+电流，募集在游泳中不活跃的神经元。因此，这些电流在神经元类型之间的差异表达可以解释为什么突触强度不能预测游泳和挣扎期间的放电可靠性/强度。这些数据表明，内在属性可以覆盖快速突触电位，介导电路重构，并有助于电机模式切换。
Many neural circuits show fast reconfiguration following altered sensory or modulatory inputs to generate stereotyped outputs. In the motor circuit of Xenopus tadpoles, I study how certain voltage-dependent ionic currents affect firing thresholds and contribute to circuit reconfiguration to generate two distinct motor patterns, swimming and struggling. Firing thresholds of excitatory interneurons [i.e., descending interneurons (dINs)] in the swimming central pattern generator are raised by depolarization due to the inactivation of Na+ currents. In contrast, the thresholds of other types of neurons active in swimming or struggling are raised by hyperpolarization from the activation of fast transient K+ currents. The firing thresholds are then compared with the excitatory synaptic drives, which are revealed by blocking action potentials intracellularly using QX314 during swimming and struggling. During swimming, transient K+ currents lower neuronal excitability and gate out neurons with weak excitation, whereas their inactivation by strong excitation in other neurons increases excitability and enables fast synaptic potentials to drive reliable firing. During struggling, continuous sensory inputs lead to high levels of network excitation. This allows the inactivation of Na+ currents and suppression of dIN activity while inactivating transient K+ currents, recruiting neurons that are not active in swimming. Therefore, differential expression of these currents between neuron types can explain why synaptic strength does not predict firing reliability/intensity during swimming and struggling. These data show that intrinsic properties can override fast synaptic potentials, mediate circuit reconfiguration, and contribute to motor–pattern switching.