In this short article we review muscle satellite cell characteristics and our studies in adult rodent muscle satellite cells in situ. Using confocal laser scanning microscopy and immunocytochemistry, a high level of IP3 receptor (IP3R) immunostaining was detected in satellite cells. These cells were identified by their peripheral position, their size, the shape of their nucleus, the paucity of the apparent cytoplasm, and the immunostaining with specific molecular markers such as a-actinin, the neural cell adhesion molecule (N-CAM) and desmin. High extracellular K+ (60 mM) induced long-lasting Ca2+ signalsin satellite cells in situ. We suggest that electrical activity stimulates IP3-associated Ca2+ signals that could act in concert with signaling pathways triggered by growth factors and/or hormones