FIGURE 1. Electrophysiological properties of NpHR in oocytes and hippocampal neurons.

a, Action spectrum of NpHR in oocytes held at -50 mV, determined by 20 nm narrow bandwidth interference filters. The ChR2 action spectrum is provided for comparison⁴. b, Extracellular [Cl^-] dependence of NpHR pump currents indicates a simple Michaelis–Menten type saturation with a K_M of 16 mM (dashed fit curve). c, Hippocampal neurons expressing NpHR–EYFP (scale bar 50 m). d, Yellow light (593 nm)-induced outward photocurrent in neurons (top panel, voltage clamp) and membrane hyperpolarization (bottom panel, current clamp); illumination duration is indicated by the yellow bar. e, NpHR peak versus steady-state current (mean  s.d.; n  =  15). f, Latency of NpHR activity measured from light onset to 50% of the peak current or hyperpolarization (mean  s.d.; n  =  15). g, NpHR peak versus steady-state membrane hyperpolarization (mean  s.d.; n  =  15). h, Illumination with yellow light potently inhibited neuronal firing.