AAV Viral Injections in Dbh-Cre Mice

Injections were performed using our established procedures [24 (link)]. Briefly, Dbh^Cre+/- mice at 6 weeks of age were anesthetized with isoflurane (4% induction, 1–2% maintenance) and stabilized in a custom stereotaxic apparatus with body temperature being maintained by a heating pad. A small craniotomy was made over each target of interest and a pulled glass micropipette (Drummond, tip diameter: 15–20 μm), beveled sharp and loaded with the injectant, was lowered into the brain. Pipettes were front-filled with AAV (serotype 2/1) expressing either CAG-FLEX-GFP (UPenn, lot# V0827) or pCAG-FLEX-tdTomato-WPRE (Addgene cat# 51503). 3 min after reaching the target, 30–50 nL of virus was dispensed using a hydraulic injector (Narishige) followed by a 5-min waiting period. The pipette was retracted 0.3 mm, paused for 10 min, and then fully retracted. Up to two injections were made per mouse targeting the locus coeruleus bilaterally (in mm relative to Bregma; 4.80 posterior, +/- 0.75 lateral, 4.00 ventral).