Brain or spinal cord sections were removed after perfusion with 4% paraformaldehyde, postfixed and cryosectioned into 30 µm-thick sections at the level of the CN (coordinates: anterior, −14.30~−14.60 mm; lateral, ±1.0~1.4 mm; deep, −7.8~−8.2 mm), the NAc (coordinates: anterior, 1.60~1.30 mm; lateral, ±0.6~1.0 mm; deep, −6.8~−7.4 mm) or the LHb (coordinates: anterior, −3.5 mm; lateral, ±0.7 mm; deep, −4.9 mm). The sections were incubated overnight (approximately 16 hr) at 4 °C with anti-c-fos rabbit polyclonal antibodies (1:200; Sigma, USA) followed by a 2-hr incubation at room temperature with a biotinylated donkey anti-rabbit Alexa Fluor 594 (red; 1:500; Sigma, USA) and mounted onto gelatin-coated slides. The sections were photographed and quantified using confocal laser scanning microscopy (LSM700, Carl Zeiss, Germany).