Figure 4.

Multicolor silencing of two neural populations, enabled by blue- and red-light drivable ion pumps of different classes. (A) Action spectra of Mac vs. Halo; rectangles indicate filter bandwidths used for multi-color silencing in vitro. Blue light power is via a 470 ± 20 nm filter at 5.3 mW/mm², and red light power is via a 630 ± 15 nm filter at 2.1 mW/mm². (B) Membrane hyperpolarizations elicited by blue vs. red light, in cells expressing Halo or Mac (N = 5 Mac-expressing neurons, N = 6 Halo-expressing neurons). (C) Action potentials evoked by current injection into patch clamped cultured neurons transfected with Halo (i) were selectively silenced by the red light but not by the blue light, and vice-versa in neurons expressing Mac (ii). Gray boxes in the inset (iii) indicate periods of patch clamp current injection.