| OCR Text |
Show 8 terminal processes in acute brain slices and in vivo. These features make the PC::G5-tdT line a useful tool for visualizing reactive astrocyte calcium dynamics in the pathological mouse brain. Intrinsic astrocyte calcium activity, that which occurs in the absence of deliberate electrically- or pharmacologically-evoked activity, reflects many different types of intracellular activity. In order characterize basic alterations in intrinsic astrocyte activity in reactive astrocytes, imaging was performed in acute brain slices obtained from an animal model of peripheral-inflammation induced by endotoxemia. Endotoxemia, which is caused by peripheral exposure to the toxic gram-negative cell wall component lipopolysaccharide (LPS), elicits a robust inflammatory response which in turn leads to activation of microglia and astrocytes in the brain. In cell culture, LPS-exposed astrocytes down-regulate several calcium-dependent signaling pathway components, including endoplasmic reticulum associated receptors for IP3 and metabotropic glutamate receptors in the plasma membrane. In vivo administration of LPS has been shown to alter the protein profile of astrocytes in a different way than described in other types of neuropathology. It is not known how in vivo administration of LPS affects astrocyte calcium dynamics in the acute period. In Chapter 4, I describe changes that were observed in astrocytic somata and processes during the acute phase of inflammation. The PC::G5-tdT reporter mouse line was crossed to the GFAP-CreER line in order to express GCaMP5G and tdTomato in astrocytes. LPS was then administered to adult mice from which acute brain slices were prepared either 6- or 24 hr postinjection. Intrinsic calcium activity in cortical layer 2/3 astrocytes was imaged with a two-photon microscope and analyzed using a relatively unbiased region of interest selection algorithm. A gradual decrease in intrinsic event frequency was observed in somata of astrocytes from the inflamed brain. An initial increase in intrinsic activity was |
