Variability of Calcium Dynamics in Brain Astrocyte Cells

Wednesday, May 30, 2018 - 9:00am - 9:50am
Lind 305
Alla Borisyuk (The University of Utah)
Astrocytes are brain cells, as numerous as neurons, but are physiologically quite different. Astrocytes play an important role in neuronal function through their calcium signaling. In our collaborators' experimental data we see a large degree of variability in the calcium signals. In this project we will explore two major causes of this variability.

First, we consider diffusion of the signal molecules as they are released near the surface of the astrocyte. As they diffuse, they can escape through absorbing parts of the boundary, be reflected off the cell walls (reflecting part of the boundary) or be captured. The capture regions (receptors), can switch between being reflecting and absorbing. Specifically, after capturing a particle, the capture region becomes reflecting for an exponentially distributed amount of time (recharge time). We show mathematically that the upper bound for the number of molecules absorbed by the switching receptors grows as the logarithm of the total number of molecules released, introducing a more significant source of variability than simple diffusion with absorbing receptors would suggest.

Next, I will present a model of astrocyte intracellular calcium signaling. We use bifurcation analysis of the model to understand a variety of types of calcium responses that can be generated in response to a brief stimulus. We also make testable predictions regarding how these responses depend on specific composition of calcium channels.