Effects of spatio-temporal changes in intracellular free-calcium concentration in central nerve system on signal transmission and anesthetic action

用高速光学成像技术对大脑皮层、海马体、三叉神经尾侧亚核和脊髓的信号传递进行了时空特征分析。(1)用电压敏感染料RH414或钙指示剂Rhod-2对小鼠大脑皮质切片进行荧光成像。对V层的单脉冲电刺激在V层引起一过性去极化，然后这种兴奋性反应传播到II-III层，并在这些层广泛扩展。AMPA/海人藻酸受体拮抗剂CNQX和P/Q型钙通道拮抗剂ω-agatoxin IVA抑制II-III层的兴奋。刺激后，V层和II-III层细胞内Ca~(2+)水平升高。ω-agatoxin IVA和Nmda受体拮抗剂MK-801部分抑制了钙通道的反应。因此，激发在层II-III m…中的传播更多的可能是由突触后AMPA/海人藻酸受体介导的。钙离子通过P/Q型钙通道的内流可能在导致突触前谷氨酸释放的细胞内钙升高中起重要作用。(2)在海马脑片上，CNQX也能抑制CA1区的兴奋传播。单脉冲刺激引起的Ca~(2+)升高对MK-801或Ca~(2+)~(2+)拮抗剂的敏感性与皮层脑片相同。(3)在三叉神经尾侧亚核，CNQX既能抑制兴奋传递，又能抑制单次脉冲刺激引起的Ca~(2+)升高。结果提示，单次脉冲刺激引起中枢神经系统不同部位钙离子升高的过程不同。(4)高频脉冲串刺激后根可诱发向更深层扩展的慢兴奋传播。高频刺激的迭代增强了其传播能力。这种增强的反应可能与被称为“发条”现象的过度兴奋相对应。较少

Signal transmissions in the cerebral cortex, hippocampus, trigeminal subnucleus caudalis and spinal cord were spatio-temporally characterized using a high-speed optical imaging technique. (1)Slice preparations of the mouse cerebral cortex were stained with a voltage sensitive dye RH414 or a Ca^<2+> indicator Rhod-2 for fluorescence imaging. Electrical single-pulse stimulation to the layer V evoked transient depolarization in the layer V, and then this excitatory response propagated to the layers II-III and widely expanded in these layers. The excitation in the layers II-III was inhibited by an AMPA/kainate receptor antagonist, CNQX, and a P/Q-type Ca^<2+> channel antagonist, ω-agatoxin IVA. Intracellular Ca^<2+> level elevated in the layer V and layers II-III in response to the stimulation. The Ca^<2+> responses were insensitive to CNQX but were profound inhibited by ω-agatoxin IVA and partially by an NMDA receptor antagonist, MK-801. Thus, excitation propagation in the layers II-III m … More ay be mediated by the post-synaptic AMPA/kainate receptors. Ca^<2+> influx through P/Q-type Ca^<2+> channels may play an important role in an intracellular Ca^<2+> elevation inducing pre-synaptic glutamate release. (2)In hippocampal slices, excitation propagation in the CA1 region was also inhibited by CNQX. Ca^<2+> elevation in response to single-pulse stimulation was not so sensitive to MK-801 or Ca^<2+> antagonists at the same concentrations as applied to the cortical slices. (3)In the trigeminal subnucleus caudalis, both excitation propagation and Ca^<2+> elevations in response to single-pulse stimulation were inhibited by CNQX. The results suggest that processes of the Ca^<2+> elevation by single-pulse stimulation were different among the regions of the central nerve system. (4)Slow excitation propagation expanded to the deeper laminae was elicited by high-frequent pulse-train stimulation to the dorsal root. The propagation was enhanced by iteration of the high-frequent stimulation. This enhanced response may correspond to hyper-excitability known as "wind-up" phenomenon. Less