Emergence of regular and complex calcium oscillations by inositol 1,4,5-trisphosphate signaling in astrocytes

We use tools of bifurcation theory to characterize dynamics of astrocytic IP(_3) and Ca(^{2+}) for different IP(_3) regimes. We do so starting from a compact, well-stirred astrocyte model to first identify characteristic IP(_3) pathways whereby Ca(^{2+}) and IP(_3) dynamics “bifurcate,” namely their dynamics changes from stable (constant) concentration levels, to oscillating ones. Then, we extend our analysis to the elemental case of two astrocytes, coupled by IP(_3) diffusion mediated by gap junction channels, leveraging on the mechanisms of emergence of chaotic oscillations. Finally, we discuss spatiotemporal Ca(^{2+}) dynamics in a spatially extended astrocyte model, gaining insights on the possible physical mechanisms whereby random Ca(^{2+}) generation could be orchestrated into robust, spatially confined intracellular Ca(^{2+}) oscillations.