Behavioral modulation patterns fit an animal model of vagus-cardiac pacemaker interactions

The present study used a computer model of the dynamic interaction between the vagus nerve and the sinoatrial pacemaker membrane potential in the heart of the rabbit to reconstruct heart rate changes under vagal excitation conditions. We asked whether a hypothetical pattern of vagal acetylcholine (ACh) release, which was based on human heart rate results in a reaction time task, could be fit to this model. The reconstructed heart rate results showed changes that were highly consistent with experimental human heart rate changes. The model reliably reproduced effects of parameters such as intrinsic heart rate level, ACh stimulus intensity, and ACh stimulus duration. In addition, the effects of anticipatory vagal ACh release, stimulus-induced ACh, and subsequent blocking of ACh, which usually interact in human cardiac cycle time functions, could be untangled in the reconstructed heart rate results. We concluded that the mathematical model may be useful for formulating hypotheses and constructing experimental task designs for studies of human heart rate.