Journal of Neuroscience, Vol 14, 4705-4715, Copyright © 1994 by Society for Neuroscience
Linearized models of calcium dynamics: formal equivalence to the cable equation
A Zador and C Koch
Neuroscience Program, Yale University School of Medicine, New Haven, Connecticut 06520.
The dynamics of calcium and other diffusible second messengers play an
important role in intracellular signaling. We show here the conditions
under which nonlinear equations governing the diffusion, extrusion, and
buffering of calcium can be linearized. Because the resulting partial
differential equation is formally identical to the one-dimensional cable
equation, quantities analogous to the input resistance, space constant, and
time constant--familiar from the study of passive electrical
propagation--can be defined. Using simulated calcium dynamics in an
infinite cable and in a dendritic spine as examples, we bound the errors
due to the linearization, and show that parameter uncertainty is so large
that most nonlinearities can usually be ignored: robust phenomena in the
nonlinear model are also present in the linear model.