Background: Electrical stimulation applied to individual organs, peripheral nerves, or specific brain regions has been used to treat a range of medical conditions. In cardiovascular disease, autonomic dysfunction contributes to the disease progression and electrical stimulation of the vagus nerve has been pursued as a treatment for the purpose of restoring the autonomic balance. However, this approach lacks selectivity in activating function- and organ-specific vagal fibers and, despite promising results of many preclinical studies, has so far failed to translate into a clinical treatment of cardiovascular disease. Objective: Here we report a successful application of optogenetics for selective stimulation of vagal efferent activity in a large animal model (sheep). Methods and results: Twelve weeks after viral transduction of a subset of vagal motoneurons, strong axonal membrane expression of the excitatory light-sensitive ion channel ChIEF was achieved in the efferent projections innervating thoracic organs and reaching beyond the level of the diaphragm. Blue laser or LED light (>10 mW mm−2; 1 ms pulses) applied to the cervical vagus triggered precisely timed, strong bursts of efferent activity with evoked action potentials propagating at speeds of ∼6 m s−1. Conclusions: These findings demonstrate that in species with a large, multi-fascicled vagus nerve, it is possible to stimulate a specific sub-population of efferent fibers using light at a site remote from the vector delivery, marking an important step towards eventual clinical use of optogenetic technology for autonomic neuromodulation.

Transcutaneous energy transfer (TET) using inductive power transfer is a promising technology for powering implantable medical devices without the need for percutaneous power cables, removing a long-term infection risk. Compared to a driveline, a TET system will produce more heat. The dominant contribution to body heating is ohmic losses in skin contacting and implanted components. This paper reports on using the body's thermoregulation mechanisms to dissipate the heat of a TET system. The ohmic losses in the primary coil of a TET system were replicated with a DC source. The coil was fixed to human participants and the temperature at the skin was measured with the coil exposed to air, and when insulation covered the coil. The highest temperature recorded was 39 °C, 2 °C lower than the regulatory limit of 41 °C. These results are supportive of using the body to dissipate heat from a TET system.