In vitro neuronal depolarization and increased synaptic activity induced by infrared neural stimulation

Neuronal responses to infrared neural stimulation (INS) are explored at the single cell level using patch-clamp electrophysiology. We examined membrane and synaptic responses of solitary tract neurons recorded in acute slices prepared from the Sprague-Dawley rat. Neurons were stimulated using a compact 1890 nm waveguide laser with light delivered to a small target area, comparable to the size of a single cell, via a single-mode fiber. We show that infrared radiation increased spontaneous synaptic event frequency, and evoked steady-state currents and neuronal depolarization. The magnitude of the responses was proportional to laser output.