Dynamics of a three-variable nonlinear model of vasomotion: Comparison of theory and experiment

The effects of pharmacological interventions that modulate Ca²⁺ homeodynamics and membrane potential in rat isolated cerebral vessels during vasomotion (i.e., rhythmic fluctuations in arterial diameter) were simulated by a third-order system of nonlinear differential equations. Independent control variables employed in the model were [Ca²⁺] in the cytosol, [Ca ²⁺] in intracellular stores, and smooth muscle membrane potential. Interactions between ryanodine- and inositol 1,4,5-trisphosphate-sensitive intracellular Ca²⁺ stores and transmembrane ion fluxes via K ⁺ channels, Cl^- channels, and voltage-operated Ca ²⁺ channels were studied by comparing simulations of oscillatory behavior with experimental measurements of membrane potential, intracellular free [Ca²⁺] and vessel diameter during a range of pharmacological interventions. The main conclusion of the study is that a general model of vasomotion that predicts experimental data can be constructed by a low-order system that incorporates nonlinear interactions between dynamical control variables.