Zupanc Günther K H
Laboratory of Neurobiology, Department of Biology, Northeastern University, Boston, MA, United States.
Front Physiol. 2017 Dec 22;8:1087. doi: 10.3389/fphys.2017.01087. eCollection 2017.
The involvement of glial cells in the regulation of physiological functions is being increasingly recognized, yet their role in plasticity of neural oscillators has remained largely elusive. An excellent model system to address the latter function is the pacemaker nucleus of the weakly electric fish, . This brainstem oscillator drives the fish's electric organ discharge in a one-to-one fashion, with median frequencies of 880 Hz in males and 740 Hz in females. Morphometric analysis of the pacemaker nucleus has shown that astrocytes outnumber mature neurons seven-fold, and oscillator neurons even 200-fold. A similar dominance of astrocytes occurs among the adult-born cells that differentiate into glia and neurons. The astrocytes form a dense meshwork of cells interconnected by gap junctions. The degree of association of astrocytic fibers with the neural oscillator cells, and the gap-junction coupling between individual astrocytes, exhibit a sexual dimorphism, which parallels the sexual dimorphisms in the output frequency of the pacemaker nucleus, and ultimately in the electric organ discharge of the fish. It is hypothesized that the dynamics in astroglial structure mediate differences in the capacity to buffer potassium, which increases during the generation of action potentials. These differences, in turn, affect the excitability of the neural oscillator cells, and thus the output frequency of the pacemaker nucleus. Comparison of the pacemaker nucleus with other brain oscillators suggests that modulation of the output activity is one of the chief functions of the interaction of glia with the neural oscillator cells.
神经胶质细胞在生理功能调节中的作用日益受到认可，然而它们在神经振荡器可塑性中的作用在很大程度上仍不明确。研究这一功能的一个极佳模型系统是弱电鱼的起搏核。这个脑干振荡器以一对一的方式驱动鱼的电器官放电，雄性的平均频率为880赫兹，雌性为740赫兹。对起搏核的形态计量分析表明，星形胶质细胞的数量比成熟神经元多七倍，而振荡神经元甚至多200倍。在分化为神经胶质细胞和神经元的成年新生细胞中，星形胶质细胞也占主导地位。星形胶质细胞形成了一个由缝隙连接相互连接的致密细胞网络。星形胶质纤维与神经振荡器细胞的关联程度以及单个星形胶质细胞之间的缝隙连接耦合表现出性别二态性，这与起搏核输出频率的性别二态性平行，最终与鱼的电器官放电的性别二态性平行。据推测，星形胶质结构的动态变化介导了缓冲钾能力的差异，钾在动作电位产生过程中会增加。这些差异反过来又会影响神经振荡器细胞的兴奋性，从而影响起搏核的输出频率。将起搏核与其他脑振荡器进行比较表明，调节输出活动是神经胶质细胞与神经振荡器细胞相互作用的主要功能之一。
