Characterization of vagus nerve active fibers during seizure in rats

Objective. Epilepsy affects approximately 70 million individuals worldwide. Vagus nerve activity is known to be modulated by seizures; however, the types of fibers that are activated during seizures remain unknown. This work compares the electrical activity of the vagus nerve before, during, and after seizures in epileptic rats.Approach. Six rats experiencing pentylenetetrazol-induced epilepsy seizures and two rats under saline solution were investigated. Action potentials (AP) identified by template matching were sorted according to the fiber type they are deemed to originate from. AP templates were based on a 3D COMSOL simplified model of the vagus nerve. Model templates were established for fibers of different diameters based on histology. Correspondences are thus established based on specific fiber diameters.Main results. During seizures, an increase in the percentage of occurrence of APs was observed for 2μm and 3μm fibers, while a decrease was observed for 4µm, 5-6µm, and 7-11µm fibers. This was not observed in the rat group under saline solution. The increase in smaller diameter sizes is believed to be linked to an increase in autonomic activity.Significance. These findings contribute to a better understanding of vagus nerve dynamics during epileptic seizures and highlight the potential of vagus nerve activity as a physiological marker for seizure detection and monitoring. This would be of particular interest in vagus nerve stimulation to control any closed-loop form of therapy. This work provides a foundation for developing novel diagnostic and therapeutic approaches in epilepsy management.