Histology
Electrode placements were verified via electrophoretic ejection of
Chicago Sky Blue dye (Sigma) at the recording site. Rats were euthanized
with a lethal dose of pentobarbital (182.2 mg/kg, IP), and brains were
removed. The tissue was fixed in 8% paraformaldehyde for at least 48 h
and transferred to a 25% sucrose solution for cryoprotection. Once
saturated, the brains were frozen and sliced coronally at 60 μm thick
using a cryostat (Thermo Scientific™ Cryostat CryoStar™ NX70) and
mounted onto gelatin-coated slides. Tissue was stained with a
combination of neutral red and cresyl violet. Only rats with verified
electrode placements for both recording and infusion sites were included
in the data analysis.