Animal model of the short-term cardiorespiratory effects of intermittent vagus nerve stimulation

Purpose To develop an animal model of the effects of vagus nerve stimulation (VNS) on heart rate and respiration in studies of seizure treatment. Methods Nine rats implanted with ECG, EMG, and VNS electrodes and pulse generator were stimulated with 81 different sets of parameters while they slept in a plethysmographic box. Result From cardiorespiratory effects of VNS, an index (α) was found to distinguish between weak and strong VNS doses. Weak VNS dose induced an increase in respiratory frequency and no significant change in heart rate. The effect of VNS on respiration, similar to that observed in children, can be divided into 3 phases. Strong VNS dose induced a decrease in respiratory frequency concomitant with a decrease in heart rate. Increasing the intensity of the VNS induced a proportional increase in the maximal inspiratory strength. Conclusion Various VNS parameter settings induce different and concomitant cardiorespiratory variations in conscious sleeping rats. These effects correlate with the intensity of the VNS parameters. Understanding the effects of the intensity of VNS parameters may allow for further optimization of VNS parameters in patients receiving VNS.