Two programs for computation of action potentials, stimulus responses, voltage-clamp currents, and current-voltage relations of excitable membranes

Abstract Digital computer programs have been developed which enable these rapid computations to be performed for membranes whose electrical behaviour is described according to the Hodgkin and Huxley scheme or extensions of it which include membrane-potential-dependent functions (rectification). The programs are easily written in any programming language from the flow charts in this article, and the user inserts the appropriate equations describing the membrane of interest. The computation is based on the Runge-Kutta method of numerical solution, but incorporates periodic checks on accuracy and a variable time step length. On-line plotting of results is permitted. The core stores required for the programs do not exceed 8300 and 11,500 32-bit words, when written in FORTRAN IV for an XDS Sigma 5 computer. Complete cardiac membrane action potentials (500 msec) require less than ten minutes of computation. It is the author's hope that ready availability of this program will induce a great many more researchers in all fields of electrophysiology to analyze their data in a form which lends itself to computations, since there will be the additional huge advantage of ready comparison of results with those of others in the field.