Visualization of astrocytic intracellular Ca mobilization.

Astrocytes generate robust intracellular Ca concentration changes (Ca signals), which are assumed to regulate astrocytic functions that play crucial roles in the regulation of brain functions. One frequently used strategy for exploring the role of astrocytic Ca signalling is the use of mice deficient in the type 2 inositol 1,4,5-trisphosphate receptor (IP R2). These IP R2-knockout (KO) mice are reportedly devoid of Ca mobilization from the endoplasmic reticulum (ER) in astrocytes. However, they have shown no functional deficits in several studies, causing a heated debate as to the functional relevance of ER-mediated Ca signalling in astrocytes. Recently, the assumption that Ca mobilization from the ER is absent in IP R2-KO astrocytes has been re-evaluated using intraorganellar Ca imaging techniques. The new results indicated that IP R2-independent Ca release may generate Ca nanodomains around the ER, which may help explain the absence of functional deficits in IP R2-KO mice.