Western blot analysis was performed as described previously [3 (link),6 (link)]. Hippocampal tissues were homogenized with lysis buffer. Protein content was measured using a Bio-Rad colorimetric protein assay kit (Bio-Rad, Hercules, CA, USA). The protein mixture containing 40 μg total protein was separated on sodium dodecyl sulfate-polyacrylamide gels and transferred onto a nitrocellulose membrane. Mouse actin antibody (1:2,000; Santa Cruz Biotechnology), mouse Bax antibody (1:1,000; Santa Cruz Biotechnology) and mouse Bcl-2 antibody (1:1,000; Santa Cruz Biotechnology) were used as primary antibodies. Horseradish peroxidase-conjugated antimouse antibodies for Bax and Bcl-2 (1:2,000; Amersham Pharmacia Biothech GmbH, Freiburg, Germany) were used as secondary antibodies. Bands were detected using an enhanced chemiluminescence detection kit (Santa Cruz Biotechnology).