Numerical Bifurcation Analysis of Pacemaker Dynamics in a Model of Smooth Muscle Cells

Area of Science:

• Biophysics
• Cellular dynamics
• Physiology

Background:

• Smooth muscle cells exhibit spontaneous oscillations, termed pacemaker dynamics, due to electro-mechanical coupling.
• These dynamics are influenced by ion fluxes across the cell membrane.
• Existing models often focus on external applied current for bifurcation analysis.

Purpose of the Study:

• To investigate pacemaker dynamics in smooth muscle cells related to ion fluxes.
• To analyze the transition between Type I and Type II excitabilities.
• To explore the role of transmural pressure in cellular dynamics.

Main Methods:

• Reduction of a smooth muscle pacemaker model to a two-dimensional system, analogous to the Morris-Lecar model.
• Detailed numerical bifurcation analysis of the reduced model.
• Computation of a two-parameter bifurcation diagram.

Main Results:

• Demonstrated a transition between Type I and Type II excitabilities without requiring external current.
• Identified parameters modeling the cell's response to transmural pressure as key drivers of excitability changes.
• Explained the observed excitability transition through the underlying bifurcation structure.

Conclusions:

• Pacemaker dynamics in smooth muscle cells can transition between excitability types based on physiological parameters like transmural pressure.
• The study provides a novel bifurcation analysis framework for understanding smooth muscle cell excitability.
• Findings offer insights into the mechanisms regulating smooth muscle cell electrical activity.