Grigonis Ramunas, Guzulaitis Robertas, Buisas Rokas, Alaburda Aidas
Department of Neurobiology and Biophysics, Vilnius University, Sauletekio ave. 7, LT-10222 Vilnius, Lithuania.
Department of Neuroscience and Pharmacology, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
Brain Res. 2016 Oct 1;1648(Pt A):110-118. doi: 10.1016/j.brainres.2016.07.030. Epub 2016 Jul 19.
During functional spinal neural network activity motoneurons receive massive synaptic excitation and inhibition, and their membrane conductance increases considerably - they are switched to a high-conductance state. High-conductance states can substantially alter response properties of motoneurons. In the present study we investigated how an increase in membrane conductance affects spike frequency adaptation, the gain (i.e., the slope of the frequency-current relationship) and the threshold for action potential generation. We used intracellular recordings from adult turtle motoneurons in spinal cord slices. Membrane conductance was increased pharmacologically by extracellular application of the GABAA receptor agonist muscimol. Our findings suggest that an increase in membrane conductance of about 40-50% increases the magnitude of spike frequency adaptation, but does not change the threshold for action potential generation. Increased conductance causes a subtractive rather than a divisive effect on the initial and the early frequency-current relationships and may have not only a subtractive but also a divisive effect on the steady-state frequency-current relationship.
在功能性脊髓神经网络活动期间，运动神经元会接收到大量的突触兴奋和抑制，并且它们的膜电导会显著增加——它们会切换到高电导状态。高电导状态会极大地改变运动神经元的反应特性。在本研究中，我们探究了膜电导增加如何影响动作电位频率适应性、增益（即频率 - 电流关系的斜率）以及动作电位产生的阈值。我们使用细胞内记录技术，记录成年海龟脊髓切片中的运动神经元。通过在细胞外应用GABAA受体激动剂蝇蕈醇，从药理学角度增加膜电导。我们的研究结果表明，膜电导增加约40 - 50%会增加动作电位频率适应性的幅度，但不会改变动作电位产生的阈值。电导增加对初始和早期频率 - 电流关系产生相减而非相除的效应，并且对稳态频率 - 电流关系可能不仅产生相减效应，还产生相除效应。
