| OCR Text |
Show 64 has been previously reported that somatic baseline fluorescence decreases in cultured astrocytes obtained from the immature rat brain during the first 24 hr following LPSexposure (Strokin et al., 2011). An increased response to bath applied ATP was also observed suggesting that during the acute phase of LPS-induced changes, endoplasmic reticula sequester calcium via store-operated calcium channels in the plasma membrane. Another group observed the opposite effect when applying mGluR5-agonists 72 hr after administration of LPS to rat astrocytes, bulk loaded with Fura-2 AM (Ronco et al., 2014). They also measured a decrease in IP3R and mGluR5 mRNA at 24 hr after LPS-exposure. GECI technology has provided the opportunity to directly observe astrocytic calcium dynamics in fine processes in situ or in vivo. To the best of our knowledge, no data have been reported regarding changes in astrocytic calcium dynamics in response to LPS in situ. Furthermore, it has been difficult to monitor calcium dynamics in astrocytic processes where important neuronal-astrocytic interactions occur. In this study, we used the GCaMP5G-expressing PC::G5-tdT reporter line crossed to the astrocyte-enriching GFAP-CreER line (Chow et al., 2008; Gee et al., 2014). GCaMP5G robustly reports calcium transients throughout the whole cytosolic compartment including fine process terminals associated with neuronal synapses. We monitored intrinsic calcium activity in somas and processes of cortical layer 2/3 astrocytes at 6 and 24 hr following LPS-administration (5 mg/kg i.p.) in C57Bl/6 mice. Similar to previous reported results obtained from cell cultures (Strokin et al., 2011), we observed a decrease in the frequency of somatic events during the acute phase of the inflammatory response. Intrinsic somatic event frequency and duration progressively decreased during the first 24 hr following LPS-administration. Intrinsic process activity also progressively decreased but temporally lagged behind the decrease observed in somas. Fine terminal |
