Software for characterizing the ionic basis of the molluscan cardiac action potential

The goal of this modeling effort was to examine how individual membrane currents determine the repertoire of electrical signals recorded from bivalve cardiac action potentials. Software was developed in C++ (for both PC and Macintosh) and Java (Internet). A series of Hodgkin-Huxley equations described the kinetics of pacemaker activity, while a degree of customization was incorporated into the simulation, enabling the user to adjust parameters to accommodate a number of animal models. A graphical user interface was developed, suitable for demonstrating the dynamics of the system to students at the introductory level via the Internet. Modulation by molluscan neurotransmitters (5HT, FRMFamide, acetylcholine) was tested by adjustment of the respective ionic conductances. The model exhibited high sensitivity to minor alterations in model parameters and provided quantification of physiological recordings. The simulation software will be useful for developing hypotheses and interpreting experimental data, in an attempt to conduct more quantitative studies on invertebrate hearts. It is proposed that the model will be used as an educational tool for introducing ionic conductance and equilibrium potential as key components of the membrane potential in pacemaker mechanisms. This will be conducted in parallel with related animal investigations in the laboratory.