線条体ニューロン及びグリア細胞における自発カルシウム濃度変化

抄録

The striatum plays an important role in linking cortical activity to basal ganglia outputs. We conducted the Ca²⁺ imaging study to investigate the spontaneous activities of the striatum. Corticostriatal slices of 1-3 weeks old GFAP-GFP mice expressed GFP in astrocytes were used. We can discriminate whether astrocytes or neurons by observation of GFP fluorescence. The slices were stained with Fura-PE3-AM to measure intracellular Ca²⁺ concentration ([Ca²⁺]_i) and the ratiometric fluorescence measurement was conducted. Long-lasting spontaneous [Ca²⁺]_i transients, which lasted up to about 300 s, were observed in both GFP positive cells (astrocytes) and GFP negative cells (putative neurons). Distributions of the duration, interval and peak amplitude of the spontaneous [Ca²⁺]_i transients in putative neurons were slightly different from those of astrocytes (p < 0.05, Kormogorov-Smirnov test). Average values were followings; duration (s): 17.3 ± 20.8 and 16.2 ± 20.5; interval (s): 105 ± 141 and 104 ± 158; peak amplitude (ΔR): 0.0206 ± 0.0115 and 0.0202 ± 0.0114 (mean ± SD, data from 178 putative neurons and 113 astrocytes, respectively). Administration of CNQX + AP5 did not block the [Ca²⁺]_i transients in the both types of cells (in 4 slices). In contrast, the numbers of the active cells, which exhibited the [Ca²⁺]_i transients, were greatly reduced by the intracellular Ca²⁺ store depletor, thapsigargin. These results suggested that both neurons and astrocytes exhibited the long-lasting spontaneous [Ca²⁺]_i transients, which were caused mainly by Ca²⁺ release from the intracellular Ca²⁺ store. [J Physiol Sci. 2008;58 Suppl:S56]