Electrical stimulation of a cardiac pacemaker cell

We studied our Hodgkin-Huxley (HH) compartmental model of the single rabbit sinoatrial node (SAN) cell to elucidate the phase-sensitive response of this pacemaker cell to aperiodic and periodic pulses of hyperpolarizing electrical current. Our computations show that the characteristics of the phase-sensitive effects (in phase response curves (PRCs) and entrainment curves (ECs)) are dependent upon the intensity (the amplitude and duration) of the stimulus applied. We explained the mechanisms involved in the phase sensitivity of the SAN cell to electrical stimulation in terms of current-voltage (IV) plots. Since the hyperpolarizing current pulses applied perturb the ionic currents only due to voltage changes, the transient changes in the membrane properties of the pacemaker cell are depicted in the PRCs.