Stereotaxic Viral Transduction for Optogenetics

All surgeries were done using a stereotaxic system (Leica Angle Two). The animals were anesthetized with isoflurane (IsoFlo) for the surgery. The skin was opened before determining striatal injection sites with the stereotaxic system. A small opening was made in the skull above the target location at bregma 0.86 mm, medial-lateral (ML) −1.53 mm (Franklin and Paxinos, 2013 ). Subsequently, the left hemisphere was injected with 300 nl viral solution at dorsal-ventral (DV) −3 mm. After that, the wound was closed and sutured before the animal was left for recovery. The virus rAAV5/EF1a-DIO-hChR2(H134R)-eYFP (UNC Vector Core) was used to express Channelrhodopsin2 (ChR2) for optogenetic stimulation experiments. Serotype 5 provided high neuronal and low transynaptic infection (Zincarelli et al., 2008 (link); Aschauer et al., 2013 (link)). The ChR2(H134R) version was selected because previous studies have shown successful expression and excitation in the same mice strains (Lopez-Huerta et al., 2016 (link)).