Functional morphology of excitable glial nets associated with sensory nerve endings-calcium image analysis.

最近的研究表明，神经胶质细胞对各种刺激的反应是通过细胞内钙离子浓度的一过性升高来实现的，这些信号介导了神经胶质细胞的活动，从而调节了神经元的功能。在皮肤感觉装置中，神经胶质细胞通过分支突起相互连接，形成一个延伸到不同轴突终末的网络。为了确定这些神经胶质网络中细胞信号的时空动力学和生理特性，用延时共聚焦显微镜监测了大鼠触觉运动感受器--披针形终末的钙图像，同时用神经递质三磷酸腺苷(ATP)刺激细胞，或用显微操作器驱动的玻璃针触摸细胞。在电子显微镜下观察神经胶质信号的形态背景。用ATP刺激可引起神经胶质细胞内钙离子浓度的振荡性升高。Thei…中的回应更多覆盖轴突终末的板层突起总是向胞体内的突起推进。在每个薄板中，由给定的刺激剂试验引起的初始波来自细胞突起中的特定位置。用玻璃针接触针状突起，会在受影响的神经胶质细胞板层中产生钙离子尖峰。钙电波偶尔在神经胶质细胞内部或之间传播，进入包围邻近轮状突起的其他神经胶质突起。这些发现暗示了亚细胞的区域化，这可能使每个神经胶质板层通过其自身的钙信号调节其伴随的披针形末端的活动，并通过板层间信号的传播来调节相邻的披针形终末的活动。药理学实验表明，神经胶质细胞的ATP诱发反应是由嘌呤受体亚型P2Y_2介导的，该亚型激活后可诱导细胞内钙离子释放。电子显微镜下可见细胞管腔内储存钙离子的光滑内质网和可能参与细胞间信号传递的缝隙连接。较少

Recent studies have shown that glial cells respond to various stimuli by a transient elevation in the intracellular Ca^<2+> concentration, and that these signals mediate glial activities to regulate neuronal functions. In cutaneous sensory devices, glial elements connect with each other by branched processes to form a network extending among different axon terminals. In order to define spatiotemporal dynamics and physiological properties of the cell signals in these glial nets, calcium images of isolated lanceolate endings, motion receptors of rat vibrissae, were monitored by time-lapse confocal microscopy while the cells were stimulated by application of the neurotransmitter adenosine 5'-triphosphate (ATP), or by touching with a micromanipulator-driven glass needle. Morphological backgrounds of the glial signaling were observed electron microscopically. Stimulation with ATP evoked an oscillatory elevation in the intracellular Ca^<2+> concentration in the glial cells. Responses in thei … More r lamellar processes covering axon terminals always proceeded to those in their cell bodies. In each lamella, the initial wave evoked by a given trial of the stimulant arose from a specific locus within the cell process. Touching with a glass needle on lanceolates triggered a Ca^<2+> spike in the affected glial lamellae. The Ca^<2+> waves occasionally traveled within, and between the glial cells, to enter other glial processes enveloping neighboring lanceolates. These findings imply subcellular compartmentalization that may enable each glial lamella to modulate the activity of its accompanying lanceolate terminal through its own Ca signal as well as to regulate neighboring lanceolates through interlamellar signal propagation. Pharmacological experiments have shown that the ATP-evoked responses of the glia are mediated by the purinoceptor subtype P2Y_2, activation of which induces Ca^<2+> release from an intracellular store. Gliai lamellae of lanceolate endings examined by electron microscopy revealed smooth endoplasmic reticulum which would store Ca^<2+> in the lumen, and gap junctions which maybe involved in the intercellular signal propagation. Less