抄録
Evidence for astrocytic participation of neuronal signal processing has cumulated in recent years. In particular, large and long-lasting cytosolic calcium surges in astrocytes, which may result in neurotransmitter release from the astrocytes, have been described in in vitro preparations. The mechanisms that give rise to these calcium events have been extensively studied in vitro. However, their existence and functions in the intact brain have just started to be addressed. We demonstrate that a topical application of Fluo-4 AM to the neocortical surface of a juvenile rat results in specific uptake of the dye in astrocytes. Using this method, we have imaged cytosolic calcium fluctuation in astrocytes of superficial cortical layers in vivo with two-photon laser scanning microscopy. Surface application of AM-ester dyes becomes increasingly difficult as the brain matures, possibly due to increased brain density. We have employed a bolus loading method [1] to apply Oregon Green 1 BAPTA AM to layer 2/3 neurons and glia of the somatosensory cortex. Co-application of sulforhodamine 101 [2] made it possible to separate astrocytes from neurons among the dye loaded cell populations. The bulk-loaded cells with the fluorescent calcium indicator were imaged simultaneously with the local field potential and the associated multi-unit activity. Spontaneously calcium surges in astrocytes were also seen in adult (> P25) rodents. Correlation of neural activity and astrocytic calcium surges in mature animal is currently being investigated.[1] Stosiek C. et al. PNAS, 100 (2003) 7319-24[2] Nimmerjahn A. et al. Nat. Methods, 31 (2004) 1: 31-37 [J Physiol Sci. 2007;57 Suppl:S26]
