Figure 1. Optical inhibition of electrically evoked motor neuron and muscle activity in Thy1-ChR2-EYFP mice with blue light.

(a) Schematic of experimental measures during electrical excitation and optical inhibition in a Thy1-ChR2-EYFP mouse. Motor axons were electrically stimulated with a stimulation cuff around the proximal sciatic nerve of an anesthetized mouse. The distal nerve was cooled and illuminated with blue laser light (465 nm). Fine wire EMG electrodes recorded electrical activity of the medial gastrocnemius. A force transducer attached at the Achilles tendon recorded contractile force of the lower limb muscles. (b) Example force and EMG data recorded during muscle twitches elicited by 25 s of 1 Hz, maximal electrical stimulation (0.1 ms pulse duration, , n = 1 mouse, 1 trial). EMG was full-wave rectified, filtered, and normalized to the maximum amplitude recorded during the trial. Average force and EMG were inhibited to 1% and 2%, respectively, of the pre-light amplitudes during 5 s of 50 Hz pulses of blue light (2 ms pulse duration, 7 mW/mm², ) with the nerve cooled to 7°C.