The expression of opsins in striatal neurons under CaMKII promoter and in vivo electrophysiological recording during laser stimulation. (a) The illustration of virus-mediated gene expression and laser stimulation; (b) Lentivirus-carrying opsins under the CaMKII promoter transfected striatal neurons. The white arrows show DARPP-32 and YFP double-positive medium spiny neurons. Green represents YFP-positive signals, Red represents DARPP-32-positvie medium spiny neurons, Bar = 30 µm. (c) Cellular morphology of DARPP-32 and YFP double-positive neurons. Green is YFP-positive signals, Red represents DARPP-32-positive medium spiny neurons, Blue is DAPI, Bar = 30 µm. (d) YFP-positive signals in the striatum, from −0.5 mm to 0.5 mm relative to bregma. (e) The activities of striatal neurons expressing ChR2 during laser stimulation. Laser pulses of 473 nm trigger spikes in striatal neurons expressing ChR2. (f) Constant laser of 594 nm reduces the firing rate of striatal neurons expressing NpHR.