Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada, H3G 1A4.
J Neurosci. 2011 Jun 15;31(24):8905-19. doi: 10.1523/JNEUROSCI.6341-10.2011.
Astrocytes show a complex structural and physiological interplay with neurons and respond to neuronal activation in vitro and in vivo with intracellular calcium elevations. These calcium changes enable astrocytes to modulate synaptic transmission and plasticity through various mechanisms. However, the response pattern of astrocytes to single neuronal depolarization events still remains unresolved. This information is critical for fully understanding the coordinated network of neuron-glial signaling in the brain. To address this, we developed a system to map astrocyte calcium responses along apical dendrites of CA1 pyramidal neurons in hippocampal slices using single-neuron stimulation with channelrhodopsin-2. This technique allowed selective neuronal depolarization without invasive manipulations known to alter calcium levels in astrocytes. Light-evoked neuronal depolarization was elicited and calcium events in surrounding astrocytes were monitored using the calcium-sensitive dye Calcium Orange. Stimulation of single neurons caused calcium responses in populations of astrocytes along the apical axis of CA1 cell dendrites. Calcium responses included single events that were synchronized with neuronal stimulation and poststimulus changes in calcium event frequency, both of which were modulated by glutamatergic and purinergic signaling. Individual astrocytes near CA1 cells showed low ability to respond to repeated neuronal depolarization events. However, the response of the surrounding astrocyte population was remarkably accurate. Interestingly, the reliability of responses was graded with respect to astrocyte location along the CA1 cell dendrite, with astrocytes residing in the primary dendrite subregion being most responsive. This study provides a new perspective on the dynamic response property of astrocyte ensembles to neuronal activity.
星形胶质细胞与神经元之间存在复杂的结构和生理相互作用，并在体外和体内对神经元的激活做出反应，表现为细胞内钙离子浓度升高。这些钙离子变化使星形胶质细胞能够通过多种机制调节突触传递和可塑性。然而，星形胶质细胞对单个神经元去极化事件的反应模式仍未得到解决。这些信息对于全面理解大脑中神经元-胶质信号的协调网络至关重要。为了解决这个问题，我们开发了一种系统，使用通道视紫红质-2 对海马切片中的 CA1 锥体神经元的顶树突进行单神经元刺激，以绘制星形胶质细胞钙反应图。这项技术允许选择性地去极化神经元，而不会对已知会改变星形胶质细胞钙离子水平的侵入性操作进行处理。用光刺激神经元，并用钙敏感染料 Calcium Orange 监测周围星形胶质细胞中的钙事件。刺激单个神经元会引起 CA1 细胞树突顶轴上的星形胶质细胞群体的钙反应。钙反应包括与神经元刺激同步的单个事件和刺激后钙事件频率的变化，这两者都受到谷氨酸能和嘌呤能信号的调节。靠近 CA1 细胞的单个星形胶质细胞对重复的神经元去极化事件的反应能力较低。然而，周围星形胶质细胞群体的反应却非常准确。有趣的是，反应的可靠性与星形胶质细胞在 CA1 细胞树突上的位置有关，位于主树突子区域的星形胶质细胞反应最强烈。这项研究为星形胶质细胞群体对神经元活动的动态反应特性提供了新的视角。
