The main aim of the workpackage was to identify a suitable animal model to evaluate functional electrical stimulation (FES) of nerve fibers. During the project and due to previous expertise several rat models for epilepsy were used in which the vagal nerve was stimulated. Following the investigation in different type of rat models (kainic acid status epilepticus model, genetic absence epilepsy model, electrical kindling model) using video-EEG monitoring, 2 rat models were identified as most suitable for the evaluation of vagal nerve fiber stimulation. Firstly, the MST (motor seizure treshold) model was validated. One hour of vagus nerve stimulation (stimulation parameters: 1mA, 30 Hz, 500 microsec) significantly increased the threshold to evoke a motor seizure in rats. This model can now be used to evaluate: 1) different stimulation parameters, 2) more sophisticated electrodes that can simultaneously record and stimulate. Secondly, the pilocarpine model has proven suitable to evaluate vagal nerve fiber stimulation. None of the rats injected with pilocarpine and stimulated with VNS, showed seizures. This model also allows to perform microdialysis during VNS in these rats to evaluate the effect of VNS on neurotransmitter release in the brain.

Although a handy model to study the functionality of VNS for epilepsy, rats are too small for an experimental implantation of a system designed for human use. A suitable animal model for task T8.5 is defined here as well. This workpackage focused on the identification of another animal in which the newly designed electrode could be tested.

Horses are known to be susceptible to a disease of the vocal cords that are innervated by the recurrent laryngeal nerve (RLN) that branches of the vagus nerve (VN). FES may be a suitable treatment option for the disease. For the identification of a larger animal model, dissection of the VN and RLN was performed in a deceased horse. As a pilot experiment, it was decided to implant a commercially available VNS system around the recurrent laryngeal nerve because the available electrodes from this system do not exceed 3 mm.