Histological determination of the microinjection sites
At the end of each experiment, animals were anaesthetized with urethane
(1.2 g/kg, i.p.), and Evans blue dye (1%, 100 nL) was microinjected at
the site of drug administration in the brain. Then, the animals were
perfuse-fixed (intracardiac 0.9% NaCl followed by 10% formalin), and
the brains were removed. After fixation in 10% formalin, the brains
were sectioned in 40 µm thick frontal cuts for analysis of the injection
sites. The actual placement of the microinjection needles was determined
upon analysis of serial sections and identified according to the rat
brain atlas of Paxinos and Watson (Paxinos & Watson, 1997).