Optogenetic stimulation

A blue laser (Opto Engine, 100 mW, 473 nm) was used as the light source for optogenetic stimulation. For all optogenetic experiments, Optopatcher (AM System; Katz et al., 2013) was used to replace the standard pipette holder. The light was delivered with a custom cut and polished optical fiber (Thorlabs, 0.39 NA TECS hard-clad, multimode, step-index fibers, FT200EMT). The optical fiber was inserted into a glass pipette within 1 mm from the pipette tip and was located coaxially to the pipette. A 2-mW laser power (measured at the internal solution filled pipette tip) was used for all experiments. The laser output power was calibrated before and after experiments to make sure the same power was used for all recordings.