For intracellular injections, sections were incubated in 4′,6-diamidino-2-phenylindole (DAPI; Sigma, St. Louis, MO, USA) for 5 minutes to reveal the cytoarchitectural features of the pyramidal layer of CA1 of the hippocampus. The sections were then mounted on nitrocellulose paper and immersed in ice-cold 0.1 M PBS. Pyramidal neurons in the CA1 region were injected with an intracellular iontophoretic injection of 5% Lucifer Yellow (Molecular Probes, Eugene, OR, USA) in PBS under a DC current of 3-8 nA for 3-5 minutes, or until the dye had completely filled distal processes and no further loading was observed (Duan et al., 2002; Duan et al., 2003; Hao et al., 2006; Radley et al., 2006; Radley et al., 2008). Five to 10 neurons were injected per slice and placed far enough apart to minimize overlap of their dendritic trees. Brain sections containing loaded neurons were then mounted on slide in Fluoromount G (Beckman Coulter, Fullerton, CA, USA).
