Rats were anaesthetized with a lethal dose of pentobarbital (100 mg/kg i.p.), and perfused intracardially with 0.1 M phosphate-buffered saline (PBS) followed by 4% paraformaldehyde in 0.1 M phosphate buffer (pH 7.4). Brains were removed, post-fixed for 48 h in the same fixative and transferred to 0.1 M PBS solution. Forty μm coronal vibratome forebrain sections (Bregma +2.5 mm to −7.5 mm) were collected in cryoprotectant solution (30% ethylene glycol, 30% glycerol in 40 mM PB; pH 7.4) in 1:12 series and stored at −20 °C. Every sixth section/animal (each section 240 μm apart) was kept for analysis of BrdU immunoreactivity (IR), an established marker of cell proliferation. Because BrdU staining may be affected by factors other than proliferation rates, such as differences in BrdU availability caused by altered blood flow or in blood–brain barrier permeability, we also used the endogenous marker of the cell cycle, Ki67 (Gerdes et al. 1984) on adjacent sections. Every twelfth section/animal (each section 480 μm apart) was kept for DCX immunohistochemistry to detect newly differentiated neurons (Brown et al. 2003; Gleeson et al. 1999;
