Zhao Shunbing, Golowasch Jorge, Nadim Farzan
Federated Department of Biological Sciences, Rutgers University and New Jersey Institute of Technology Newark, NJ, USA.
Front Behav Neurosci. 2010 May 18;4:21. doi: 10.3389/fnbeh.2010.00021. eCollection 2010.
Linear leak currents have been implicated in the regulation of neuronal excitability, generation of neuronal and network oscillations, and network state transitions. Yet, few studies have directly tested the dependence of network oscillations on leak currents or explored the role of leak currents on network activity. In the oscillatory pyloric network of decapod crustaceans neuromodulatory inputs are necessary for pacemaker activity. A large subset of neuromodulators is known to activate a single voltage-gated inward current I(MI), which has been shown to regulate the rhythmic activity of the network and its pacemaker neurons. Using the dynamic clamp technique, we show that the crucial component of I(MI) for the generation of oscillatory activity is only a close-to-linear portion of the current-voltage relationship. The nature of this conductance is such that the presence or the absence of neuromodulators effectively regulates the amount of leak current and the input resistance in the pacemaker neurons. When deprived of neuromodulatory inputs, pyloric oscillations are disrupted; yet, a linear reduction of the total conductance in a single neuron within the pacemaker group recovers not only the pacemaker activity in that neuron, but also leads to a recovery of oscillations in the entire pyloric network. The recovered activity produces proper frequency and phasing that is similar to that induced by neuromodulators. These results show that the passive properties of pacemaker neurons can significantly affect their capacity to generate and regulate the oscillatory activity of an entire network, and that this feature is exploited by neuromodulatory inputs.
线性泄漏电流与神经元兴奋性的调节、神经元及网络振荡的产生以及网络状态转换有关。然而，很少有研究直接测试网络振荡对泄漏电流的依赖性，或探究泄漏电流在网络活动中的作用。在十足目甲壳动物的振荡幽门网络中，神经调节输入对于起搏器活动是必需的。已知很大一部分神经调质会激活单一的电压门控内向电流I(MI)，该电流已被证明可调节网络及其起搏器神经元的节律性活动。使用动态钳技术，我们表明，I(MI)产生振荡活动的关键成分仅是电流-电压关系中接近线性的部分。这种电导的性质使得神经调质的存在与否有效地调节了起搏器神经元中的泄漏电流量和输入电阻。当缺乏神经调节输入时，幽门振荡会被破坏；然而，起搏器组中单个神经元的总电导线性降低不仅能恢复该神经元的起搏器活动，还能使整个幽门网络的振荡恢复。恢复的活动产生的频率和相位与神经调质诱导的相似。这些结果表明，起搏器神经元的被动特性可显著影响其产生和调节整个网络振荡活动的能力，并且神经调节输入利用了这一特性。
