Modulating and Recording Gastrointestinal Motility Using the Opennerve Open Source Platform

Introduction: OpenNerve is a complete open-source platform designed to enable translational research in bioelectronic medicine. The platform includes a rechargeable implantable pulse generator (IPG) that can be used with various designs of leads for biosensing and/or stimulation, as well as an external charger and a Bluetooth-based controller such as phone or tablet. All source files and protocols are available on GitHub under a permissive license [1]. The OpenNerve IPG can provide bipolar current stimulation across any two of eight electrodes and its analog front-ends can support recording electromyography (EMG), electrocardiography, or neural signals. A digital I2C port allows connection to in-body sensors. OpenNerve is currently undergoing validation in animal models.

Methods: As a proof of concept, OpenNerve is being tested for modulating gastrointestinal motility in pigs. First pig has been implanted with a bipolar cuff electrode on the cervical vagus nerve and EMG electrodes in the duodenal wall, and a second pig has been implanted with an electrode array in the sacral foramen at S3 and EMG electrodes in the colon wall. Electrodes were left in place for at least 60 days, then connected externally to an OpenNerve pulse generator. Glucagon was injected intravenously to suppress gastrointestinal motility, and stimulation was applied while simultaneously recording EMG. After electrophysiology, animals were sacrificed and histological assessment was performed on tissue around the electrodes.

Results: Stimulation of the cervical vagus nerve and the S3 sacral nerve (1 ms, 10 Hz, 3-5 mA) triggered increased motility in the duodenum and colon respectively after approximately 5 minutes of continuous stimulation, as evidenced by a sharp increase in EMG power. In the duodenum, EMG power decreased when stimulation ended, while in the colon, EMG power remained high for at least 30 minutes afterwards. Histology at the sites of EMG electrodes in the duodenal and colonic wall showed no damage or inflammation beyond the expected thin fibrotic capsule around electrodes.

Conclusion: The OpenNerve platform was used for simultaneous stimulation and biosensing in the pig gastrointestinal tract. As expected, duodenal motility increased during stimulation of the cervical vagus nerve, while colonic motility increase was triggered by sacral nerve stimulation and continued after stimulation ended. Histology showed no significant tissue damage or inflammation to the intestinal wall at 60 days after implantation. Next steps include implanting six pigs using the OpenNerve IPG with stimulation, EMG, and motion sensing leads to evaluate the safety of chronic stimulation for increasing gastrointestinal motility.