Kinetic properties and functional dynamics of sodium channels during repetitive spiking in a slow pacemaker neuron.
Kinetic properties and functional dynamics of sodium channels during repetitive spiking in a slow pacemaker neuron.
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DOI：
10.1523/jneurosci.0445-10.2010
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发表时间：
2010-09-08
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影响因子：
--
通讯作者：
Smith JC
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文献类型：
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作者：
Milescu LS;Yamanishi T;Ptak K;Smith JC
我们研究了电压门控性Na+通道的动力学特性及其对延髓中缝神经元重复发放活动的贡献，这些神经元表现出缓慢的起搏和强烈的发放适应。该研究是基于全细胞膜片钳，建模和实时计算的组合。Na+电流记录从雄性和雌性新生大鼠获得的脑切片中的神经元，使用电压钳协议，旨在减少空间钳伪影，并强调功能相关的动力学特征。一个详细的动力学模型，制定解释了广泛的瞬态和稳态电压依赖性的Na+电流所表现出的性能。通过经由动态钳注入基于模型的电流作为天然TTX敏感性Na+电流的替代物来测试模型，所述天然TTX敏感性Na+电流被阻断。基于模型的电流很好地再现了原生尖峰形状和尖峰频率。通过该模型间接研究了重复尖峰过程中Na+通道的动力学。通过比较动态钳实验中不同动力学模型产生的尖峰活动，我们确定了状态依赖性慢失活对尖峰适应有显著贡献。通过实时操作的模型为基础的电流，我们建立了阈上Na+电流主要控制尖峰的形状，而阈下Na+电流调制尖峰频率，并有助于起搏机制。由于基于模型的电流被注入索马，结果还表明，体细胞Na+通道足以建立在体外的中缝神经元的基本尖峰特性。
We examined the kinetic properties of voltage-gated Na+ channels and their contribution to the repetitive spiking activity of medullary raphé neurons, which exhibit slow pacemaking and strong spiking adaptation. The study is based on a combination of whole-cell patch clamp, modeling and real-time computation. Na+ currents were recorded from neurons in brain slices obtained from male and female neonatal rats, using voltage-clamp protocols designed to reduce space-clamp artifacts and to emphasize functionally relevant kinetic features. A detailed kinetic model was formulated to explain the broad range of transient and stationary voltage-dependent properties exhibited by Na+ currents. The model was tested by injecting via dynamic clamp a model-based current as a substitute for the native TTX-sensitive Na+ currents, which were pharmacologically blocked. The model-based current reproduced well the native spike shape and spiking frequency. The dynamics of Na+ channels during repetitive spiking were indirectly examined through this model. By comparing the spiking activities generated with different kinetic models in dynamic clamp experiments, we determined that state-dependent slow inactivation contributes significantly to spiking adaptation. Through real-time manipulation of the model-based current, we established that suprathreshold Na+ current mainly controls spike shape, whereas subthreshold Na+ current modulates spiking frequency and contributes to the pacemaking mechanism. Since the model-based current was injected in the soma, the results also suggest that somatic Na+ channels are sufficient to establish the essential spiking properties of raphé neurons in vitro.