Spectrally distinct channelrhodopsins for two-colour optogenetic peripheral nerve stimulation.

Technologies for peripheral nerve stimulation have conventionally relied on the anatomic placement of electrodes adjacent to subsets of sensory fibres or motor fibres that selectively target an end effector. Here, we demonstrate the use of optogenetics to directly target the innervating fibres of an end effector by relying on retrograde transfection of adeno-associated virus serotype 6 to restrict axonal opsin expression to the desired fibre targets. By using an in vivo screen in rats, we identify the first channelrhodopsins as well as a halorhodopsin that respond to red light in the peripheral nerve.