iLMO2 is able to suppress neural activity in anesthetized rats.
(a) Left: photograph depicting a cannula-electrode in which a guide cannula (white asterisk) was glued to a 16-channel microwire array (row 1 targeting CA1, row 2 targeting CA3) so that an optical fiber inserted through an injection cannula (white arrow) can be positioned 1–2 mm away from electrode tips. Scale bar: 1 mm. Right: Histology depicting tips of electrode tracks (asterisks) targeted to the pyramidal cell layer (outlined) of the dorsal hippocampus. Note robust expression of iLMO2 (green) in the pyramidal cells around electrode holes. DAPI stain (blue) highlights nuclei of migratory glial cells around electrode tips. Scale bar: 100 μm. (b) Example of single-units sorted using super-paramagnetic clustering. (c) Population average (n = 6) of normalized single-unit firing rate over time (middle, SEM shaded) with corresponding raster (top, each color corresponds to different unit) and spectrogram (bottom) for a representative CTZ injection trial (injected at time = 0, vertical dashed line). (d) Population average (n = 6) of normalized single-unit firing rate, raster and spectrogram for the same units shown in (c) for a representative vehicle injection trial (injected at time = 0, vertical dashed line). (e) Normalized single-unit firing rate averaged across all intracerebral CTZ (red) and vehicle (blue) injection trials (n = 5 trials each, same 24 units for each group) from the same animal shown above. Injections occurred at t = 0 denoted by vertical dashed line. (f) Average peak change in single-unit firing rate to light, CTZ and vehicle across all animals (n = 3). Error bars indicate standard error of the mean.