A variable-threshold motoneuron model that incorporates time- and voltage-dependent potassium and calcium conductances.
A variable-threshold motoneuron model that incorporates time- and voltage-dependent potassium and calcium conductances.
复制标题
可变阈值运动神经元模型，包含时间和电压依赖性钾和钙电导。
DOI：
10.1152/jn.1993.70.1.246
复制
发表时间：
1993
影响因子：
2.5
通讯作者：
Powers,RK
中科院分区：
文献类型：
--
作者：
Powers,RK
1.开发了“跨阈值”运动神经元模型，以将最近描述的猫α运动神经元的生物物理特征与运动神经元放电行为联系起来。该模型融合了先前模型中未包含的三个特征：1）低阈值、持续的钙电流； 2) 主要离子电导的实际电压依赖性； 3) 可变尖峰阈值。通过将这些额外的生物物理特征连续添加到具有单一钾电导的固定阈值模型中，研究了这些额外的生物物理特征对模型行为的影响。 2.具有一或两个钾电导的固定阈值模型无法产生适当的放电行为。稳态频率-电流（F-I）关系的特点是斜率不断增加，与真实运动神经元中观察到的分段线性关系不同。这些模型还在最高“注入”电流水平下产生了不切实际的高放电率。 3. 增加一个可变尖峰阈值，该阈值随着注入电流的大小线性增加，可以将最大放电速率限制在更现实的水平。然而，稳态 F-I 关系仍然没有表现出适当的形状。 4.低阈值钙电流的结合使得模型产生的稳态 F-I 关系与真实运动神经元中获得的稳态 F-I 关系之间具有良好的定量一致性。此外，该模型的总膜电流和膜电压之间的稳态关系（I-V关系）与真实运动神经元中测量的非常相似。该模型的 I-V 和 F-I 关系对于钙电导大小和膜电压之间稳态关系的精确形式都非常敏感。 5. 其他修改，包括第二个钙电导和将尖峰阈值与膜电压相关的因子，有助于产生更真实的后超极化和第一间隔 F-I 关系。 6.通过降低慢速钾电导并增加控制低阈值钙电导的激活和失活的时间常数，可以产生双稳态放电行为。 7. 因此，最终模型再现了广泛的运动神经元行为，包括阈下整流、分段线性第一间隔和稳态 F-I 关系，以及经过适当修改的双稳态放电行为。尽管如此，通过简化快速尖峰电导的表示以及其他离子电导的动力学，该模型仍然足够简单，可以合并到更大的神经网络中。
1. A "threshold-crossing" motoneuron model was developed to relate recently described biophysical features of cat alpha-motoneurons to motoneuron discharge behavior. This model incorporated three features not included in precedent models: 1) a low-threshold, persistent calcium current; 2) realistic voltage dependencies of the major ionic conductances; and 3) a variable spike threshold. The effects of these additional biophysical features on model behavior were investigated by successively adding them to a fixed threshold model with a single potassium conductance. 2. Fixed-threshold models with either one or two potassium conductances could not produce appropriate discharge behavior. Steady-state frequency-current (F-I) relations were characterized by a continuously increasing slope, unlike the piecewise linear relations observed in real motoneurons. These models also produced unrealistically high discharge rates at the highest levels of "injected" current. 3. The addition of a variable spike threshold, which was made to increase linearly with the magnitude of injected current, could limit maximum discharge rates to more realistic levels. However, steady-state F-I relations still did not exhibit the appropriate shape. 4. The incorporation of a low-threshold calcium current led to a good quantitative agreement between the steady-state F-I relations produced by the model and those obtained in real motoneurons. In addition, the steady-state relation between total membrane current and membrane voltage (I-V relation) of the model was very similar to those measured in real motoneurons. The model's I-V and F-I relations were both very sensitive to the exact form of the steady-state relation between the magnitude of the calcium conductance and membrane voltage. 5. Additional modifications, which included a second calcium conductance and a factor relating spike threshold to membrane voltage, helped to produce more realistic afterhyperpolarizations and first-interval F-I relations. 6. Bistable discharge behavior could be produced by reducing the slow potassium conductance and increasing the time constants governing the activation and deactivation of the low-threshold calcium conductance. 7. The final model thus reproduces a wide range of motoneuron behaviors including subthreshold rectification, piecewise linear first interval and steady-state F-I relations, and, with appropriate modifications, bistable discharge behavior. Nonetheless, by simplifying the representation of fast spike conductances as well as the kinetics of the other ionic conductances, the model remains simple enough to be incorporated into a larger neural network.